API 560 Fired Heaters

This document is under review as revision to an API Standard; it is under consideration within an API technical committee but has
not received all approvals required for

publication. This document shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee activities except with the approval of the Chairman
of the committee having jurisdiction and staff of the API Standards Dept. Copyright API. All rights reserved.
Fired Heaters for General Refinery

Service
API STANDARD 560
Proposed 5th Edition, Addendum 2
Redline Ballot Draft: Sections 12.1.5-12.1.6 and corresponding material

in Annex A datasheet (datasheet page 3 line 6)
Note: USC datasheets are currently under edit.
1
This document is under review as revision to an API Standard; it is under consideration within an API technical committee but has not received all approvals required for
Foreword
Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise,
for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither
should anything contained in the publication be construed as insuring anyone against liability for infringement
of letters patents.
Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the specification.
Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required in
order to conform to the specification.
May: As used in a standard, “may” denotes a course of action permissible within the limits of a standard.
Can: As used in a standard, “can” denotes a statement of possibility or capability.
This document was produced under API standardization procedures that ensure appropriate notification and
participation in the developmental process and is designated as an API standard. Questions concerning the
interpretation of the content of this publication or comments and questions concerning the procedures under
which this publication was developed should be directed in writing to the Director of Standards, American
Petroleum Institute, 1220 L Street, NW, Washington, D.C. 20005. Requests for permission to reproduce or
translate all or any part of the material published herein should also be addressed to the director.
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Suggested revisions are invited and should be submitted to the Standards Department, API,
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Introduction
Direct fired heaters are used extensively in oil refineries, chemical, petrochemical, and other industrial plants to
heat fluids within tubes at high temperatures not achievable by other methods. Heat is provided by combustion
of fuel in burners. API 560 is the industry recognized standard for design and fabrication of direct fired heaters.
This document defines common terms and requirements for the design, fabrication, and inspection of direct
fired heaters for general refinery service.
This standard also has applicability to specific aspects to steam reformers, pyrolysis furnaces and other fired
equipment in the areas of design, fabrication and inspection of components common to direct fired heaters.
Users of this Standard should be aware that further or differing requirements may be needed for individual
applications. This Standard is not intended to inhibit a supplier from offering, or the purchaser from accepting,
alternative equipment or engineering solutions for the individual application. This may be particularly applicable
where there is innovative or developing technology. Where an alternative is offered, the supplier should identify
any variations from this standard and provide details.
In API Standards, the SI system of units is used. In this standard, where practical, US Customary (USC) units
are included in brackets for information.
A bullet () at the beginning of a clause or sub-clause indicates that either a decision is required, or further
information is to be provided by the purchaser. This information should be indicated on the purchaser’s
checklist (see Annex B) or stated in the inquiry or purchase order.
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1 Scope
This standard specifies requirements and guidance for the design, specification, materials, refractory lining
systems, fabrication, inspection, testing, and preparation for shipment of direct fired heaters, including air
preheaters, fans, and burners for general refinery service.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references,
only the edition cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
>>>Note to Committee Members and API Staff: With the introduction of “pressure design code”, “structural
design code”, and the use of “informative examples” such as in reference to codes, material specifications, and
reference to “or equivalent” in the material tables in the document, several normative references have been
moved to the Bibliography. The intent is to provide a document that is more inclusion of international codes and
standards with the purchaser making decisions on the selected code, standard or specification and associated
materials.
However, since a few sections of the standard have not been reviewed since e5.0, some legacy normative
references may remain, in Section 2, which otherwise should have been moved to the Bibliography. The full
transition should be complete the next Addendum 3 or the next edition, i.e. Edition 6.0.
The footnote references have not been updated. API Editors please handle since it is difficult to do this with track
change on and the large number of changes made.
The following documents are no longer contained in the standard and therefore have been removed from
Section 2.
ASTM C155 ASTM C177 ASTM C201 ASTM C401 ASTM C892 ASTM E1172 EN 10025-2:2004
EN 60079 ISA 51.1 ISO 1940-2:2003 NFPA 70
NOTE 1 See F.3 for normative references specific to air preheat and ducting systems
NOTE 2 See M.2 for normative references specific to ceramic coatings.
API Standard 530, Calculation of Heater Tube Thickness in Petroleum Refineries
API Recommended Practice 535, Burners for Fired Heaters in General Refinery Services
API Standard 673, Centrifugal Fans for Petroleum, Chemical, and Gas Industry Services
API Standard 936, Refractory Installation Quality Control—Inspection and Testing Monolithic Refractory Linings
and Materials
API Standard 975, Refractory Installation Quality Control - Inspection and Testing of Refractory Brick Systems
and Materials
API Standard 976, Refractory Installation Quality Control-Inspection and Testing of AES/RCF Fiber Linings and
Materials
ASTM A123/A123M, Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products
ASTM A143/A143M, Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural
Steel Products and Procedure for Detecting Embrittlement
4
ASTM A153/A153M, Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
ASTM A240/A240M, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet,
and Strip for Pressure Vessels and for General Applications
ASTM A387/A387M, Standard Specification for Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum
ASTM A1008/A1008M, Standard Specification For Steel, Sheet, Cold-Rolled, Carbon, Structural, High-
Strength Low-Alloy, High-Strength Low-Alloy With Improved Formability, Solution Hardened, And Bake
Hardenable
ASTM B633/B633M, Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel
ASTM C27, Standard Classification of Fireclay and High-Alumina Refractory Brick

1
ISO 1461 , Hot dip galvanized coatings on fabricated iron and steel articles—Specifications and test methods
ISO 8501-1, Preparation of steel substrates before application of paints and related products—Visual
assessment of surface cleanliness—Part 1: Rust grades and preparation grades of uncoated steel substrates
and of steel substrates after overall removal of previous coatings
ISO 10684, Fasteners—Hot dip galvanized coatings

2
MSS SP-53 , Quality Standard for Steel Castings and Forgings for Valves, Flanges and Fittings and Other
Piping Components—Magnetic Particle Exam Method
MSS SP-55, Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components—
Visual Method for Evaluation of Surface Irregularities
MSS SP-93, Quality Standard for Steel Castings and Forgings for Valves, Flanges, Fittings, and Other Piping
Components—Liquid Penetrant Examination Method
3
SSPC SP 3 , Power Tool Cleaning
SSPC SP 6/NACE No. 3, Commercial Blast Cleaning
1
International Organization for Standardization, 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20,
Switzerland, www.iso.org.
2
Manufacturers Standardization Society of the Valve and Fittings Industry, Inc., 127 Park Street, NE, Vienna, Virginia
22180- 4602, www.mss-hq.com.
3
The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, Pennsylvania 15222, www.sspc.org.
5
3 Terms, Definitions, and Abbreviations

For the purposes of this document, the following terms and definitions apply.
NOTE 1 See F.3 for terms, definitions and abbreviations specific to air preheat and ducting systems.
NOTE 2 See M.3 for terms, definitions, symbols and abbreviations specific to ceramic coatings.
3.1 General Terms and Definitions

NOTE 1 The following general definitions are provided to better define and distinguish the multi-disciplined workforce
and the typical areas of responsibility involved in the specification, design and supply work processes required in the
overall procurement process for fired heat transfer equipment such as a reforming furnace. These definitions are intended
to build upon the typical definitions of purchaser and vendor normally used in API Standards.
NOTE 2 Recognizing that the work process and areas of responsibility may differ between projects and owner
organizations, the terms and definitions contained in the purchaser’s procurement documentation take precedence over
definition of parties of the multi-disciplined workforces and their respective areas of responsibility.
>>>API Editors to revise 3.1 into alphabetical order
3.1.1
purchaser
The owner or purchaser is the party with responsibility for all or part of the process and thermal design /
definition, the mechanical specification, procurement, and construction of the purchased equipment.
NOTE 1 The owner or purchaser most often works through an engineering contractor (contractor) as an agent undertaking
owner’s requirement for the engineering, procurement and construction phases of work including representation of the owner
on decisions related to operation and maintenance as may be required. The term purchaser within this document will be
considered synonymous with the term contractor or owner.
NOTE 2 Construction includes installation/erection of purchased equipment.
3.1.2
supplier
The supplier is the party that manufactures or supplies equipment and services to perform the duties specified
by the purchaser.
NOTE The supplier typically has the prime responsibility for the thermal design, detailed engineering, material
procurement, project management and manufacturing processes involved in the physical supply of the fired equipment
including all aspects of quality assurance, quality control for work of their own and others whom they qualify for providing work,
products, or services on their behalf i.e. vendors, fabricators, refractory manufacturers, and refractory contractors.
3.1.3
technology provider
The technology provider is the party that provides licensed or proprietary technology information typically in the
form of a process design or licensor package including a process performance guarantee.
3.1.4
vendor
The vendor is the party that provides engineered products, sub-components, or services for the project work.
NOTE The vendor, whether they directly produce the materials or are agents in supply of such components, have
responsibility for the quality of the product to either recognized industry or other standards as directed by the purchaser,
whomever they may be. Vendors typically supply sub-components such as; burners, fans, dampers, instrumentation, pipe
hangers, castings, refractory, pipe / tubes, and fittings etc. A vendor may also provide specialty engineering services such as;
finite element analysis (FEA). Within the context of this standard, the supplier has prime responsibility for the products and
services provided by the vendor.
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3.1.5
fabricator
The fabricator is the party that provides the facilities and services to physically construct, all or part of the
project work as directed by the supplier.
NOTE The fabricator would be responsible for the quality control of their own works and quality assurance of any directly
purchased or sub-contracted work by them.
3.1.6
refractory contractor
The refractory contractor, when different from the refractory manufacturer, is the party that undertakes all, or
part of, the construction, design, engineering, material procurement and application of refractory products on
behalf of the supplier.
NOTE The refractory contractor has responsibly for the quality control of their products and services.
3.1.7
refractory manufacturer
The refractory manufacturer is the party that manufactures the refractory products and / or ancillaries for
supply to the refractory contractor.
NOTE The refractory manufacturer has primary responsibility for material design properties, manufacturing quality control
at the manufacturing site and specific procedures such as those for product mixing, installation, and start-up.
3.1.8
installer
Company or individual responsible for installing the ceramic coating or refractory lining.
3.2 Terms and Definitions – Fired Heaters

3.2.1
air preheater
preheater
Heat transfer apparatus through which combustion air is passed and heated by a medium of higher temperature,
such as combustion products, steam, or other fluid.
3.2.2
arch
Flat or sloped portion of the heater radiant section opposite the floor.
3.2.3
ash
The non-combustible residue, considered a foulant on the tubes, that remains after burning a fuel or other
combustible material.
NOTE Ash may be corrosive to steel or the refractory lining, depending on the composition and metals content of the fuel.
3.2.4
atomizer
Device used to reduce a liquid fuel oil to a fine mist, using steam, air, or mechanical means.
3.2.5
average heat flux density
The average heat flux is the net heat transferred per tube outside surface area.
NOTE 1 When referred to the radiant section, it is equal to the process duty absorbed in the section or zone divided by the
total outside surface area of the coil in the section or zone.
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NOTE 2 The relation between the average heat flux and the peak circumferential flux onto the tubes is defined in API 530
Annex B.
NOTE 3 Average flux for an extended-surface tube is indicated on a bare surface basis with extension ratio noted.
3.2.6
balanced draft heater
Heater that uses forced-draft fans to supply combustion air and uses induced-draft fans to remove flue gases.
3.2.7
breeching
Heater section where flue gases are collected after the last convection coil for transmission to the stack or the
outlet ductwork.
3.2.8
bridgewall
gravity wall
Wall that separates two adjacent heater zones.
3.2.9
bridgewall temperature
Temperature of flue gas leaving the radiant section.
3.2.10
bull nose
A rounded convex edge, corner, or projection such as at the flue gas inlet to a convection section.
3.2.11
burner
Device that introduces fuel and air into a heater at the desired velocities, turbulence, and concentration to
establish and maintain proper ignition and combustion.
NOTE Burners are classified by the type of fuel fired, such as oil, gas, or a combination of gas and oil, which may be
designated as “dual fuel” or “combination.”
3.2.12
burner block
burner brick
burner tile
Refractory block that forms the burner’s air flow opening, stabilizes the flame, and provides the desired flame
shape.
NOTE: Also referred to as muffle block or quarl.
3.2.13
butterfly damper
Single-blade damper, which pivots about its center.
3.2.14
casing
Metal plate used to enclose the fired heater.
3.2.15
convection section
Portion of the heater in which the heat is transferred to the tubes primarily by convection.
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3.2.16
corbel
Projection from the refractory surface generally used to prevent flue gas bypassing the tubes of the convection
section if they are on a staggered pitch.
3.2.17
corrosion allowance
Material thickness added to allow for material loss during the design life of the component.
3.2.18
corrosion rate
Rate of reduction in the material thickness due to chemical attack from the process fluid or flue gas, or both.
3.2.19
critical section (tube supports)
Tube support sections subjected to the highest loads and / or stress typically considered to be abrupt changes in
sections, seating surfaces and at junctions of risers, gates or feeders to the castings.
3.2.20
crossover
Interconnecting piping between any two heater sections (e.g. radiant to convection).
NOTE Interconnecting pipework within radiant coil sections may be referred as jump overs.
3.2.21
damper
Device for introducing a variable resistance in order to regulate the flow of flue gas or air.
3.2.22
4
dead time
The time after the initiation of an input change and before the start of the resulting observable response.
3.2.23
deflection / target wall
A refractory wall used to redirect flames or shield portions of a fired heater from gas or radiant heat.
3.2.24
design heat release
3.2.24.1
design heat release (burner)
The burner design heat release for a single burner is the heater design heat release, divided by the number of
burners, and multiplied by the burner design margin. See 14.1.7.
3.2.24.2
design heat release (heater)
The design absorbed duty of the fired heater divided by the lower heating value fuel efficiency for the same
process case.
NOTE The fuel efficiency is calculated using:
− the design excess air level,
4
ANSI/ISA-TR75.25.02-2000 (R2010), Control Valve Response Measurement from Step Inputs, Clause 3.4
9
− design ambient humidity,

− the fuel composition requiring the highest air to fuel ratio at the target excess air level, and
− the combustion air temperature calculated with the air preheat system in service (where applicable)
− the ambient air temperature used for determining the stack height.
3.2.25
draft
Negative pressure (vacuum) of the air and / or flue gas measured at any point in the heater.
3.2.26
draft loss
Pressure drop (including buoyancy effect) through duct conduits or across tubes and equipment in air and flue
gas systems.
3.2.27
duct
Conduit for air or flue gas flow.
3.2.28
erosion
Reduction in material thickness due to mechanical attack from a solid or fluid.
3.2.29
excess air
Amount of air above the stoichiometric requirement.
NOTE Excess air is expressed as a percentage.
3.2.30
extended surface
Heat-transfer surface in the form of fins or studs attached to the heat-absorbing surface.
3.2.31
extension ratio
Ratio of total outside exposed surface to the outside surface of the bare tube.
3.2.32
fan static pressure rise
Static pressure at the fan outlet flange minus the static pressure at the fan inlet flange.
3.2.33
flue gas
Gaseous product of combustion including excess air.
3.2.34
forced-draft heater
Heater for which combustion air is supplied by a fan or other mechanical means.
3.2.35
fouling resistance
Factor used to calculate the overall heat transfer coefficient.
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NOTE The inside fouling resistance is used to calculate the maximum metal temperature for design. The external fouling
resistance is used to compensate the loss of performance due to deposits on the external surface of the tubes or extended
surface.
3.2.36
fuel efficiency
Total heat absorbed divided by the total input of heat derived from the combustion of fuel only (lower heating
value basis).
NOTE This definition excludes sensible heat of the fuels and applies to the net amount of heat exported from the unit.
3.2.37
guillotine
isolation blind
Single-blade device used to isolate equipment or heaters.
3.2.39
header box
Internally insulated compartment, separated from the flue gas stream, which is used to enclose a number of
return bends, headers or manifolds.
NOTE Access is afforded by means of hinged doors or removable panels.
3.2.40
heat absorption
Total heat absorbed by the coils, excluding any combustion air preheat.
3.2.41
higher (gross) heating value
HHV
Total heat obtained from the combustion of a specified fuel at 15 °C (60 °F).
3.2.42
indirect preheater
Fluid-to-air heat-transfer device.
NOTE The heat transfer can be accomplished by using a heat-transfer fluid, process stream, or utility stream that has been
heated by the flue gas or other means. A heat pipe preheater uses a vaporizing/condensing fluid to transfer heat between the
flue gas and air.
3.2.43
induced-draft heater
Heater that uses a fan to remove flue gases and to maintain a negative pressure in the heater to induce
combustion air without a forced-draft fan.
3.2.44
louver damper
Damper consisting of several blades, each of which pivots about its center and is linked to the other blades for
simultaneous operation.
3.2.45
lower (net) heating value
LHV
Higher heating value minus the latent heat of vaporization of the water formed by combustion of hydrogen in the
fuel.
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3.2.46
manifold
Chamber for the collection and distribution of fluid to or from multiple parallel flow paths.
3.2.47
maximum expected fan inlet temperature
Normal operating fan inlet temperature plus a margin for any abnormal specified operating condition, e.g. the
upstream equipment becoming fouled.
3.2.48
maximum heat flux density
Maximum local rate of heat transfer in the coil section.
3.2.49
minimum heat release
Lowest absorbed duty of the fired heater divided by the lower heating value fuel efficiency for the same process
case.
NOTE1: Where the fuel efficiency is calculated using:
− the target excess air level for the lowest absorbed duty case,
− zero ambient humidity,
− the fuel composition requiring the lowest air to fuel ratio at the target excess air level,
− the combustion air temperature calculated with the air preheat system in service (where applicable)
− the ambient air temperature used for determining the stack height.
3.2.50
natural draft heater
Heater in which a stack effect induces the combustion air and removes the flue gases.
3.2.51
normal heat release (burner)
The Heater Design Heat Release, as defined in 3.2.24.2, divided by the number of burners.
3.2.52
pass stream
Flow circuit consisting of one or more tubes in series.
3.2.53
pilot
Small burner that provides ignition energy to light the main burner.
3.2.54
plenum windbox
Chamber surrounding the burners that is used to distribute air to the burners or reduce combustion noise.
3.2.55
plug header
Cast return bend provided with one or more openings for the purpose of inspection or mechanical tube cleaning.
3.2.56
pressure design code
Recognized pressure design code or standard that is specified or agreed by the purchaser.
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EXAMPLES ASME Boiler and Pressure Vessel Code, Section VIII or EN 13445 (all parts) for pressure vessels and ASME B31.3 or
EN 13480 (all parts) for piping.
NOTE Tube wall thickness calculations for fired process tubes follow API 530.
3.2.57
pressure drop
Difference between the inlet and the outlet static pressures between termination points, excluding the static
differential head.
3.2.58
protective coating
Corrosion-resistant material applied to a metal surface.
EXAMPLE Coating on casing plates behind porous refractory materials to protect against sulfur in the flue gases.
3.2.59
radiant section
Portion of the heater in which heat is transferred to the tubes primarily by radiation.
3.2.60
radiation loss
setting loss
Heat lost to the surroundings from the casing of the heater and the ducts and auxiliary equipment (when heat
recovery systems are used).
3.2.61
return bend
Cast or wrought fitting shaped in a 180 ° bend and used to connect two tubes.
3.2.62
setting
Heater casing, brickwork, refractory, and insulation, including the tie-backs.
3.2.63
shield section
shock section
Tubes that shield the remaining convection-section tubes from direct flame radiation.
3.2.64
sootblower
Device used to remove soot or other deposits from heat-absorbing surfaces in the convection section.
NOTE Steam is normally the medium used for soot-blowing.
3.2.65
stack
Vertical conduit used to discharge flue gas to the atmosphere.
3.2.66
strake
spoiler
Metal attachment to a stack that can prevent the formation of von Karman vortices that can cause wind-induced
vibration.
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3.2.67
structural design code
Recognized structural design code or standard specified or agreed by the purchaser.
EXAMPLE International Building Code (IBC).
3.2.68
structural welding code
Recognized structural welding code or standard specified or agreed by the purchaser.
EXAMPLE AWS D1.1/D1.1M
3.2.69
target wall reradiating wall
Vertical refractory firebrick wall that is exposed to direct flame impingement on one or both sides.
3.2.70
temperature allowance
Number of degrees Celsius (Fahrenheit) to be added to the process fluid temperature to account for flow
maldistribution and operating unknowns.
NOTE The temperature allowance is added to the calculated maximum tube metal temperature or the equivalent tube
metal temperature to obtain the design metal temperature.
3.2.71
terminal
Flanged or welded connection to or from the coil providing for inlet and outlet of fluids.
3.2.72
thermal efficiency
Total heat absorbed divided by the total input of heat derived from the combustion of fuel (hL) plus sensible heats
from air, fuel, and any atomizing medium.
3.2.73
tube guide
Device used with vertical tubes to restrict horizontal movement while allowing the tubes to expand axially.
3.2.74
tube sheet, end
Tube sheet located at the convection section end walls, which are welded or bolted to the heater casing and
usually are refractory lined on the hot face.
3.2.75
tube sheet, intermediate
tube support, intermediate
Tube sheet located in the convection exposed to the hot flue gases on both sides.
3.3 Terms and Definitions – Refractory

3.3.1
alkali hydrolysis
A potentially destructive, naturally occurring reaction between hydraulic setting refractory concrete, carbon
dioxide, alkaline compounds, and water.
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3.3.2
alkaline earth silicate fiber
AES fiber
Manmade vitreous fiber (MMVF) composed of at least 18 % alkaline earth oxides developed for their low bio-
persistence.
NOTE Also known as bio-fiber, bio-soluble, or low bio-persistence fiber.
3.3.3
anchor
Metallic or refractory device that holds the refractory or insulation in place.
3.3.4
backup layer
Refractory layer behind the hot-face layer.
3.3.5
batten strip
A layer of fiber blanket placed and compressed between courses of fiber modules.
3.3.6
block insulation
Lightweight, preformed rigid block used as a backup layer because of its high insulating properties and its limited
temperature resistance.
3.3.7
castable
A combination of refractory grain (aggregate) and suitable bonding agent that, after the addition of a proper liquid,
is installed into place to form a refractory shape or structure that becomes rigid because of thermal or chemical
action.
3.3.8
cold-face
The surface of a refractory lining against the metal casing surface.
3.3.9
cold-face temperature
Temperature at the casing calculated using the thermal resistance of the lining and hot-face temperature.
3.3.10
cold joint
A joint formed in an otherwise monolithic refractory that results from work stoppage during refractory installation.
3.3.11
compliance datasheet
A list of mechanical and chemical properties for a specified refractory material that are warranted by the
manufacturer to be met if and when the product is tested by the listed procedure.
3.3.12
dual layer
Refractory construction comprised of two refractory materials wherein each material performs a separate
function.
EXAMPLE A dense monolithic over insulating monolithic.
15
3.3.13
expansion joint
A non-bonded joint in a refractory lining system with a gap designed to accommodate thermal expansion of
adjoining materials, commonly packed with a temperature resistant compressible material such as fiber.
3.3.14
firebrick
Refractory brick of any type.
3.2.15
high-duty fireclay brick
Fireclay brick which has a pyrometric cone equivalent (P.C.E.) not lower than Cone 31½, or above 32½ to 33.
3.3.16
hot-face layer
Refractory layer exposed to the highest temperatures in a multilayer or multicomponent lining.
3.3.17
hot-face temperature
Temperature of the refractory surface in contact with the flue gas or heated combustion air.
NOTE This is the temperature used for thermal calculations for operating cold-face temperature and heat loss.
3.3.18
interface temperature
Calculated temperature between any two adjacent layers of a multi-layer or multicomponent refractory
construction.
3.3.19
mineral wool block
Block insulation composed of mineral wool fiber and an organic binder.
3.3.20
module
Construction of fibrous refractory insulation in stacked / folded blankets or monolithic form, commonly with an
integrated attachment system.
3.3.21
monolithic refractory
A refractory which may be installed in situ, without joints to form an integral structure.
3.3.22
mortar
A finely ground preparation which becomes plastic and trowelable when mixed with water and is suitable for use
in laying and bonding refractory bricks together.
3.3.23
multicomponent lining
Refractory system consisting of two or more layers of different refractory types.
NOTE Examples of refractory types are castable, insulating firebrick, firebrick, block, board, and ceramic fiber.
3.3.24
needled
A knitted structure of fibers to enhance handling and mechanical strength of fibrous refractory insulation in
stacked or folded blanket form.
16
3.3.25
parquet
A fibrous refractory insulation module lining design where module support anchoring is aligned perpendicular for
each adjacent module.
3.3.26
permanent linear change
A measure of a refractory’s physical property that defines the change in dimensions as a result of initial heating to
a specific temperature.
3.3.27
refractory ceramic fibers
RCF
Manmade vitreous fiber whose chemical constituents are predominantly alumina and silica.
3.3.28
refractory to maximum continuous use temperature
Maximum temperature to which a refractory may be continuously exposed without excessive shrinkage or
mechanical breakdown.
NOTE 1 It is also sometimes referred to as the “recommended use limit” or “continuous-use temperature”.
NOTE 2 This may not be the same as the “Maximum Service Temperature” quoted on the manufacturer’s product data
sheet.
3.3.29
rigidizer
A liquid applied to alkaline earth silicate / refractory ceramic fiber (AES/RCF) construction which produces a rigid
lining surface when dried.
3.3.30
soldier course
A fibrous refractory insulation module lining design where module support anchoring is aligned (parallel) similarly
for all modules in a row.
3.3.31
sprayable/pumpable fibers
Mixture of bulk fiber and wet binder suitable for pumping or spraying.
3.3.32
super-duty fireclay brick
Fireclay bricks which have a pyrometric cone equivalent (P.C.E.) not lower than Cone 33, and which meet certain
other requirements, as outlined in ASTM C27.
3.3.33
tie-backs
Mechanical fastening devices used to hold a refractory lining structure in position while permitting the lining to
thermally expand and contract.
3.3.34
vapor barrier
Metallic foil placed between layers of refractory as a barrier to flue gas flow.
NOTE This barrier protects the steel shell from corrosion caused by condensing acids.
17
3.3.35
wet blanket
Flexible, formable, RCF blanket saturated with wet binder that sets on heat exposure forming a rigid durable
structure.
3.4 Abbreviations
For the purposes of this document, the following abbreviations apply.
AES alkaline earth silicate fiber
APH air preheat system
BCD burner-circle-diameter
BTB normalized burner-to-burner spacing
BTC normalized burner-to-coil spacing
CO carbon monoxide
HHV higher (gross) heat value
IFB insulating firebrick
LHV lower (net) heating value
MMVF manmade vitreous fiber
NOx oxides of nitrogen, i.e. nitrous oxide, nitric oxide
PMI positive materials identification
RCF refractory ceramic fibers
SCR selective catalytic reduction
SiO2 silicon dioxide
TCD tube-circle-diameter
4 General
● 4.1 The pressure design code shall be specified or agreed by the purchaser.
4.2 Pressure components shall comply with the pressure design code and the supplemental requirements in
this standard.
● 4.3 The structural design code shall be specified or agreed by the purchaser.
4.4 Structural components shall comply with the structural design code and the supplemental requirements
in this standard.
● 4.5 Structural welding shall comply the structural welding code and the supplemental requirements in this
standard. >>new
18
● 4.6 The purchaser and the supplier shall mutually determine the measures required to comply with all local
and national regulations applicable to the equipment.
● 4.7 The supplier shall comply with all local and national regulations specified by the purchaser.
API Staff Note: 4.3 Heater Nomenclature and Figures 1, 2 and 3 in e5.1 have been moved to a new annex;
Annex O in e5.2
5 Proposals
5.1 Purchaser’s Responsibilities

5.1.1 The purchaser’s inquiry shall include data sheets, checklists, and other applicable information outlined in
this standard. This information shall include any special requirements or exceptions to this standard.
NOTE The purchaser should complete, as a minimum, those items on the datasheet that are designated by an asterisk (*).
Refer to Annex A.
5.1.2 The purchaser is responsible for the correct process specification to enable the supplier to prepare the
fired heater design.
NOTE Process engineers historically provide process conditions for normal mode of operation, at start-of-run, end-of-run
and process design cases. In addition, consideration should be given to providing one or more of the following cases.
a) startup mode of operation, including;
1) burner lighting state of operation and,
2) ramp-up state of operation.
b) normal mode of operation / turndown state of operation;
c) maintenance mode of operation / coke removal.
5.1.3 The purchaser’s inquiry shall state clearly the supplier’s scope of supply.
5.1.4 Process performance and guarantee requirements shall be communicated through the equipment
datasheets and documentation requirements as defined in the inquiry documents. Specific guarantee
requirements for all guaranteed criteria shall be clearly noted in the purchase order.
5.1.5 The purchaser shall specify the required degree of shop assembly and/or modularization and any
transportation limits, local to, or within the plant site.
5.1.6 The purchaser shall specify the anticipated period time between delivery to site and commissioning for
refractory dryout and equipment preservation considerations.
5.1.7 The purchaser shall specify the applicable codes for design and fabrication including any registration and
inspection requirements with local or national regulatory authority.
5.2 Supplier’s Responsibilities

5.2.1 The supplier’s proposal shall include:
19
a) completed data sheets for each fired heater and the associated equipment (see examples in Annex A);
b) a description of the full scope of supply and work;
c) an outline drawing showing firebox dimensions, burner layout and clearances, arrangement of tubes,
platforms, ducting, stack, breeching, and a plot plan of the heater, fans, preheater, SCR etc., as may be
applicable;
d) full definition of the extent of shop assembly including the number, size and mass of prefabricated parts,
and the number of field welds (see examples in Annex C);
e) detailed description of any exceptions to the specified requirement;
● f) when specified by the purchaser, a completed noise datasheet;
g) curves for heaters in vaporizing service, showing pressure, temperature, weight fraction vapor, and bulk
velocity as a function of the tube number for each specified operating case;
h) a time schedule for submission of all required drawings, data, and documents;
i) a program for scheduling the work after receipt of an order;
NOTE The program schedule should include a specified period of time for the purchaser to review and return drawings,
procurement of materials, manufacture, and the required date of supply;
j) a list of utilities and quantities required;
● k) when specified by the purchaser, a list of sub-suppliers, including country and location, shall be provided by
the following:
1) pipes and fittings;
2) coil fabrication;
3) extended surfaces on tubes;
4) castings, steel fabrication;
5) ladders and platforms;
6) refractory supply;
7) refractory installation;
8) air preheater;
9) fans;
10) burners;
11) instrumentation;
12) system skids;
13) other auxiliary equipment as applicable.
l) equipment warrantees and process performance guarantees.
20
5.3 Documentation
5.3.1 Drawings for Purchaser’s Review
5.3.1.1 The supplier shall submit general arrangement drawings of each heater for review. The general
arrangement drawings shall include the following information:
a) heater service, the purchaser’s equipment number, the project name and location, the purchase order
numbers, and the supplier’s reference number;
b) coil terminal sizes, including flange ratings and facings, dimensional locations, direction of process flow,
and allowable loads, moments, and forces on terminals;
c) coil and crossover arrangements, tube spacings, tube diameters, tube-wall thicknesses, tube lengths,
material specifications, including grades for pressure parts only, and all extended surface data;
d) tube support details;
e) coil design pressures, hydrostatic test pressures, design fluid, and tube-wall temperatures and corrosion
allowance;
f) the applicable coil design code and fabrication codes or specification;
g) refractory and insulation types, thicknesses, and service temperature ratings;
h) types and materials of anchors for refractory and insulation;
i) burner assembly drawings and, if applicable, burner piping drawings;
j) locations and number of access doors, observation doors, burners, sootblowers, dampers, and instrument
and auxiliary connections;
k) locations and dimensions of platforms, ladders, and stairways;
l) overall dimensions, including auxiliary equipment;
m) an overall plot plan when air preheat, emission control, fan system, skid packages or any other grade
mounted equipment or components are provided.
5.3.1.2 The supplier shall submit the additional drawings for review:
a) arrangement drawings, including modules and sub-assemblies shipped to the jobsite;
b) details of dampers;
NOTE Details of dampers should include enough information to allow verification that the normative requirements are
satisfied.
c) auxiliary nozzle, instrument and sample point legend and details;
d) refractory anchor layout drawings and attachment details;
f) tube visibility drawing (see 12.3.3.5 and 12.3.3.7)
NOTE Tube visibility drawings should show the extent of view of the burners, radiant tubes/supports, lowest row of shock
tubes/supports, and tubeskin thermocouples from each observation port.
h) tube support drawings;
21
NOTE Drawings should include enough information to allow verification that the normative requirements are satisfied.
i) burner fuel capacity curves (heat release vs. burner tip pressure) for the specified fuels and design excess
air and including operating points for burner “design”, “normal” and “minimum” heat release rates;
j) burner air capacity curves (heat release vs. draft loss) for forced draft burners with design excess air at
15°C (60°F) and design air temperature;
k) all auxiliary equipment including control actuators, control and isolation louvers / dampers, expansion joints,
fans, motors, air preheaters, air flow measurement devices, burners, pilots etc.
5.3.2 Foundation-loading Diagrams

5.3.2.1 The supplier shall submit for purchaser’s review foundation-loading diagrams for each heater and for any
other grade mounted equipment within the scope of supply. The diagram shall include the following information:
a) number and locations of piers and supports;
b) baseplate dimensions;
c) anchor bolt locations, bolt diameters, and projection above foundations;
d) dead loads, live loads, wind or earthquake loads, reaction to overturning moments, and lateral shear loads.
5.3.3 Documents for Purchaser’s Review

5.3.3.1 The individual stages of design, procurement, and fabrication shall not proceed until the relevant
document has been reviewed and confirmed as being accepted by the purchaser. The supplier shall submit the
following documents for review and comment:
a) documentation list
b) structural steel calculations;
c) stack design and structural calculations; (see 13.3 and Annex H)
● d) when specified by the purchaser, structural welding, examination, and test procedures;
e) draft calculations for natural and balanced draft heater with configurations including the air preheat system
(APH), fans, SCRs etc. for each defined operating case with design fuel and excess air with summer
ambient design conditions;
f) burner test procedures;
g) lifting lug and trunnion calculations
● h) when specified by the purchaser, tube support design calculations;
i) thermowell and thermocouple details;
j) pressure welding, examination, and test procedures;
k) installation, dry-out, and test procedures for refractories and insulation;
l) refractory thickness calculations, including temperature gradients through all refractory sections and
sources of thermal conductivities;
● m) when specified by the purchaser, decoking procedures;

22
n) installation, operation, and maintenance instructions for the heater and for auxiliary equipment such as air
preheaters, fans, drivers, dampers, and burners;
o) performance curves or data sheets for air preheaters, fans, drivers, burners, and other auxiliary equipment;
p) factory acceptance test results;
● q) when specified by the purchaser, noise data sheets
r) inspection and test plan (ITP) covering all phases of supply, fabrication and construction including that of all
vendors, fabricators, and refractory contractors.
5.3.4 Certified Drawings and Diagrams

5.3.4.1 Following receipt of the purchaser’s comments and confirmation to proceed on the general
arrangement drawing and other documentation submitted for approval, the supplier shall provide the following
certified data:
a) certified general arrangement drawings and foundation loading diagrams;
b) detail drawings, erection drawings, and an erection sequence;
c) pressure design code calculations.
NOTE Registration with a local or national regulatory authority is not always required.
5.3.5 Performance Tests and Guarantees
● 5.3.5.1 Performance tests shall be performed when specified by the purchaser.
5.3.5.2 The test protocol shall be mutually agreed by supplier and purchaser, including for differences in feed,
fuel, and ambient conditions.
NOTE The variation of operating conditions, feedstock and fuels, relative to design and its impact on guarantees should
be adjusted with agreement between purchaser and supplier.
5.4 Final Records

5.4.1 Within a specified time after completion of shop fabrication or shipment, the supplier shall furnish the
purchaser with the following documents:
a) data sheets and drawings for the heater and all equipment in the scope of work, representing the
as-manufactured equipment; in the event field-changes are made, as-built drawings and data sheets shall not be
provided unless specifically requested by the purchaser;
b) certified material reports, mill test reports, or ladle analysis for all pressure parts and for alloy extended
surfaces;
c) installation, operation, and maintenance instructions for the heater and auxiliary equipment, such as air
preheaters, fans, drivers, dampers, and burners;
d) performance curves or data sheets for air preheaters, fans, drivers, burners, and other auxiliary equipment;
e) bill of materials;
● f) when specified by the purchaser, noise data sheets;
g) refractory dry-out procedures;

23
h) decoking procedures where applicable;
i) NDE reports for tube-support castings;
j) all other test documents, including test reports and nondestructive examination reports;
k) factory acceptance test results;
l) equipment shop test results;
m) calculated internal pressure (see 12.1.6).
6 Design Considerations
6.1 Process Design

6.1.1 Heaters shall be designed for symmetric heat distribution. Multipass heaters shall be designed for hydraulic
symmetry of all passes.
6.1.2 The number of passes for vaporizing fluids shall be minimized. Each pass shall be a single circuit from inlet
to outlet.
6.1.3 Unless otherwise specified, the design average heat flux density shall be based on a single row of tubes
spaced on two nominal tube diameters. The first row of shield-section tubes shall be considered as radiant
service in determining the average heat flux density if these tubes are exposed to direct flame radiation.
6.1.4 For tubes spaced on three nominal diameters or double-sided firing, provided the maximum flux including
maldistribution, shall not exceed that specified for two nominal diameters.
NOTE 1 Average heat flux density in the radiant section is normally based on a single row of tubes spaced on two
nominal tube diameters.
NOTE 2 Where the average radiant heat flux density is specified based on two nominal diameters, the supplier may
increase the flux rate for other coil arrangements.
6.1.5 The maximum allowable inside film temperature for any process service shall not be exceeded anywhere in
the specified coil.
6.2 Combustion Design

6.2.1 Margins provided in the combustion system are not intended to permit operation of the heater at greater
than the design case absorbed duty.
6.2.2 Calculated fuel efficiencies shall be based on the lower heating value of the design fuel and shall account
for the rate of heat loss from the exterior surfaces of the heater; along with heat loss from associated ducts, fans,
air preheater and selective catalytic reduction (SCR); to cooler surroundings. Hardware on the flue gas side
downstream of the last heat exchange is not applicable.
6.2.3 Unless otherwise specified by the purchaser, calculated efficiencies for natural draft operation shall be
based upon 15 % excess air if gas is the primary fuel and 25 % excess air if oil is the primary fuel. In the case of
forced-draft operation, calculated efficiencies shall be based on 15 % excess air for fuel gas and 20 % excess air
for fuel oil.
6.2.4 The heater efficiency and tube-wall temperature shall be calculated using the specified fouling resistances.
NOTE Annex G gives guidance on the measurement of efficiency.
2 2
6.2.5 The floor firing density of the radiant section shall not exceed 950 kW/m (300,000 Btu/h/ft ) for floor
mounted gas or oil-fired burners.
24
NOTE 1 Floor firing density is based on the heater design heat release (LHV basis) plus the sensible heat of preheated air at
normal heat release conditions, divided by the floor surface area bound by the tube centerline for tubes near the vertical wall
excluding roof and hip tubes. When multiple tube diameters or multiple tube rows are present, the tube centerline that results
in the minimum floor surface area shall be used. For layouts with tubes not near the vertical wall then the wall itself becomes
the boundary of the area.
NOTE 2 Although the luminous nature of oil flames usually leads to a much higher peak to average flux ratio than on gas
flames, design limits on floor firing density, normalized burner-to-burner spacing (BTB) and normalized burner-to-coil spacing
(BTC) are expected to avoid undesirable flame collapse and flame roll over. See Section 14 for more information on burner
spacing.
6.2.6 Stack and flue gas systems shall be designed so that a negative pressure of at least 25 Pa (0.10 in. H2O) is
maintained in the arch section or point of minimum draft location (which is typically below the shield section).
Stack design conditions shall be based on heater design conditions with 120% of flue gas mass flow.
6.3 Mechanical Design

6.3.1 Provisions for thermal expansion shall take into consideration all specified operating conditions, including
short-term conditions such as steam-air decoking.
● 6.3.2 When specified by the purchaser, the convection-section tube layout shall include space for future
installation of sootblowers, water washing, or steam-lancing doors.
6.3.3 When the heater is designed for heavy fuel-oil firing, sootblowers shall be provided for convection-
section cleaning.
● 6.3.4 If light fuel oils such as naphtha are to be fired, the purchaser shall specify whether sootblowers are to
be supplied.
6.3.5 The convection-section design shall incorporate space for the future addition of two rows of tubes, including
the end and intermediate tube sheets. Placement of sootblowers and cleaning lanes shall be suitable for the
addition of the future tubes. Holes in end-tube sheets shall be plugged to prevent flue gas leakage.
6.3.6 Vertical cylindrical heaters shall be designed with a maximum height-to-diameter ratio of 3.00, where the
height is that of the radiant section (inside refractory face) and the diameter is that of the tube circle, both
measured in the same units.
6.3.7 For single-fired, box-type, floor-fired heaters with sidewall tubes only, an equivalent height-to-width factor
shall be determined by dividing the height of the wall bank (or the straight tube length for vertical tubes) by the
distance between wall tube banks and applying the limitations in Table 1.
Table 1--Heater Height-to-Width Ranges
Design Absorption Height-to-Width Ratio Height-to-Width Ratio

MW (Btu/h × 106) max. min.
Up to 3.5 (12) 2.00 1.50

3.5 to 7 (12 to 24) 3.00 1.50
Over 7 (24) 4.00 1.50
NOTE Unless otherwise agreed, for heaters with hip tubes, the maximum height-to-width ratio
shall be measured to the top of the hip tubes and the minimum height-to-width ratio shall be
measured the bottom of the hip tubes.
6.3.8 Shield sections shall have at least three rows of bare tubes.
25
6.3.9 Except for the first shield row, triangular pitched convection sections shall be designed with corbels or
baffles to minimize the amount of flue gas bypassing the heating surface. The first corbel or baffle shall be
installed at the second shield tube row.
6.3.10 The minimum clearance from grade to burner plenum or register and fuel manifold or burner piping shall
be 2 m (6.5 ft) for floor-fired heaters, unless otherwise specified by the purchaser.
6.3.11 For vertical-tube, vertical-fired heaters, the maximum radiant straight tube length shall be 21.35 m (70 ft)
and shall not contain intermediate welds, unless approved by purchaser (refer to 7.1.4). For horizontal heaters
fired from both ends, the maximum radiant straight tube length shall be 12.2 m (40 ft).
6.3.12 Radiant tubes shall be installed with minimum spacing from refractory or insulation to tube centerline of
1.5 nominal tube diameters, with a clearance of not less than 100 mm (4 in.) from the refractory or insulation. For
horizontal radiant tubes, the minimum clearance from floor refractory to tube outside diameter shall be not less
than 300 mm (12 in.).
6.3.13 The heater arrangement shall allow for replacement of individual tubes or hairpins without disturbing
adjacent tubes.
● 6.3.14 When specified by the purchaser, the layout of tubes in the convection section shall incorporate a
450 mm (18 in.) fin tip to fin tip vertical gap or space every eight tube rows to allow access for inspection. Provide
a minimum of one access door, having a minimum clear opening of 600 mm × 600 mm (24 in. × 24 in.), in the
space between each set of tube sheets in each vertical gap. Permanent platforms are not required.
● 6.3.15 When specified by the purchaser, tubes and / or refractory shall be coated in accordance with Annex M.
26
7 Tubes
7.1 General
7.1.1 Tube-wall thickness for coils shall be determined in accordance with API 530, in which the practical
limit to minimum thickness for new tubes is specified. For materials not included, tube-wall thickness shall be
determined in accordance with API 530 using stress values mutually agreed upon between purchaser and
supplier.
7.1.2 Unless otherwise agreed between the purchaser and supplier, calculations made to determine tube-
wall thickness for coils shall include considerations for erosion and corrosion allowances for the various coil
materials. The following corrosion allowances shall be used as a minimum:
a) carbon steel through C-1/2Mo: 3 mm (0.125 in.);
b) low alloys through 9Cr-1Mo: 2 mm (0.080 in.);
c) above 9Cr-1Mo through austenitic steels: 1 mm (0.040 in.).
NOTE For erosive services, the purchaser may consider adding additional allowance as required. This allowance is
intended to be treated in the calculations as “corrosion allowance”.
7.1.3 Maximum tube metal temperature shall be determined in accordance with API 530. The tube-metal
temperature allowance shall be at least 15 °C (25 °F).
7.1.4 All tubes shall be seamless. Tubes shall not be circumferentially welded to obtain the required tube
length, unless approved by the purchaser, in which case the location of welds shall be agreed by purchaser.
Electric resistance welding shall not be used for intermediate welds. Tubes furnished to an average wall
thickness shall be in accordance with tolerances that provide the required minimum wall thickness is
provided.
7.1.5 Tubes, if projected into header box housings, shall extend at least 150 mm (6 in.), in the cold
position, beyond the face of the end-tube sheet, of which 100 mm (4 in.) shall be bare.
7.1.6 Tube size shall be selected in accordance with sizes as indicated in Table 5.
NOTE 1 Other tube sizes should be used only if warranted by special process considerations.
NOTE 2 Pipes and tubes have different specification criteria and manufacturing tolerances. The intent of this clause is to
keep the outside diameters consistent with nominal pipe size specifications.
7.1.7 If the shield and radiant tubes are in the same service, the shield tubes shall be of the same material
as the connecting radiant tubes.
7.2 Extended Surface

● 7.2.1 The purchaser shall specify or agree on the type of extended surface used in convection sections:
a) finned – where helically wound fins are high frequency continuously welded to the tube, or;
b) studded – where each stud is attached to the tube by arc-resistance welding.
● 7.2.2 Where finned extended surface finning is used; the purchaser shall specify or agree on the use of solid
or segmented (serrated) fins.
NOTE Other extended surface designs may be allowed with purchaser acceptance.
27
7.2.3 Metallurgy for the extended surface shall be selected on the basis of maximum calculated tip
temperature as listed in Table 2.
Table 2—Extended Surface Materials
Studs Fins
a
Material Maximum Tip Temperature Maximum Tip Temperature ASTM Specification
°C (°F) °C (°F)
Carbon steel 510 (950) 454 (850) A1008
2 1/4Cr-1Mo, 5Cr-1/2Mo 593 (1100) 549 (1000) A387 Gr 22, A387 Gr 5
11-13Cr 649 (1200) 593 (1100) A240 TP 409

18Cr-8Ni stainless steel 815 (1500) 815 (1500) A240 TP304
25Cr-20Ni stainless steel 982 (1800) 982 (1800) A240 TP 310
a
or purchaser approved materials
7.2.4 Extended surface dimensions shall be limited to those listed in Table 3.
Table 3—Extended Surface Dimensions
Studs Fins
Minimum Normal Maximum Number
Fuel Minimum Diameter Maximum Height Maximum Height
Thickness per Unit Length
mm (in.) mm (in.) mm (in.) mm (in.) per m (per in.)
Gas 12.5 (1/2) 25 (1) 1.3 (0.05) 25.4 (1) 197 (5)
Oil 12.5 (1/2) 25 (1) 2.5 (0.10) 19.1 (3/4) 118 (3)
7.2.5 A minimum clearance of 32 mm (1.25 in.) shall be maintained between the outside diameter of
extended surfaces of adjacent tubes.
28
7.3 Materials
Tube materials shall be selected in accordance with material specifications listed in Table 4 and as contained in API 530 or
their equivalent agreed by the purchaser.
Table 4—Heater-tube Material Specifications

a
ASTM Specifications
Material
Pipe Tube
Carbon steel A53, A106 Gr B A192, A210 Gr A-1
Carbon-1/2Mo A335 Gr P1 A209 Gr T1
11/4Cr-1/2Mo A335 Gr P11 A213 Gr T11
21/4Cr-1Mo A335 Gr P22 A213 Gr T22
3Cr-1Mo A335 Gr P21 A213 Gr T21
5Cr-1/2Mo A335 Gr P5 A213 Gr T5
5Cr-1/2Mo-Si A335 Gr P5b A213 Gr T5b
9Cr-1Mo A335 Gr P9 A213 Gr T9
9Cr-1Mo-V A335 Gr P91 A213 Gr T91
9Cr-2Si-1Cu A335 Gr P921 A213 Gr T921
10.5Cr-V A335 Gr P115 A213 Gr T115
18Cr-8Ni A312, A376, TP 304, TP 304H, and TP 304L A213, TP 304, TP 304H, and TP 304L
16Cr-12Ni-2Mo A312, A376, TP 316, TP 316H, and TP 316L A213, TP 316, TP 316H, and TP 316L
18Cr-10Ni-3Mo A312, A376, and TP 317L A213, and TP 317L
18Cr-10Ni-Ti A312, A376, TP 321, and TP 321H A213, TP 321, and TP 321H
18Cr-10Ni-Nb b A312, A376, TP 347, TP 347H and TP 347LN A213, TP 347, TP 347H and TP 347LN
18Cr-10Ni-3Cu-Nb b A312, UNS S34752 A213, UNS S34752
Nickel alloy 800 H/800 HT c B407 B407
25Cr-20Ni A608 Gr HK40 A213 TP 310H
a or equivalent materials from the applicable pressure design code.
b Niobium (Nb) was formerly called columbium (Cb).
c Minimum grain size shall be ASTM #5 or coarser.
8 Return Bends and Plug Headers
8.1 General
8.1.1 The allowable stress shall be no higher than that for similar materials as given in API 530 and shall be
reduced by casting-quality factors if made from castings. Casting-quality factors shall be in accordance with the
pressure design code, e.g. ASME B31.3.
8.1.2 The specified wall thickness shall include a corrosion allowance. This allowance shall not be less than
that used for the tubes.
NOTE For erosive services, the purchaser may consider adding additional allowance as required.
29
8.1.3 Any material thickness added as an erosion factor shall be treated in design calculations as a corrosion
allowance.
8.1.4 Elbows and other return fittings shall follow the same design criteria as return bends and plug
headers.8.1.5The use of thicker schedule return bends and plug headers (ID constraints) than the tubes they are
connected to shall not create challenges with respect to cleaning and inspection.
8.2 Return Bends

8.2.1 Return bends shall be attached to tubes by welding when inside the radiant section or header boxes.
8.2.2 Return bends inside the firebox shall be selected for the same design pressure and temperature as the
connecting tubes.
8.2.3 Return bends inside a header box shall be selected for the same design pressure as the connecting
tubes and for a design temperature equal to the maximum fluid operating temperature at that location plus a
minimum of 30 °C (55 °F).
8.2.4 Return bends shall be at least the same thickness as the connecting tubes.
8.2.5 Regardless of the location of the welded return bends, the heater design shall incorporate means to
permit convenient removal and replacement of tubes and return bends.
8.2.6 Longitudinally welded return bends and elbows shall not be used
8.3 Plug Headers

8.3.1 Plug headers shall be located in a header box and shall be selected for the same design pressure as
the connecting tubes and for a design temperature equal to the maximum fluid operating temperature at that
location, plus a minimum of 30 °C (55 °F).
8.3.2 Tubes and plug headers shall be arranged so that there is enough space for field maintenance
operations, such as welding and stress relieving.
8.3.3 When plug headers are specified, they shall consist of the two-hole type.
NOTE Plug headers may be used for cleaning of coked or fouled tubes using mechanical techniques such as turbining.
● 8.3.4 When plug headers are specified by the purchaser for horizontal tubes that are 18.3 m (60 ft) or longer,
two-hole plug headers shall be used on both ends of the coil assembly. For shorter coils, plug headers shall be
provided on one end of the coil with welded return bends on the opposite end.
● 8.3.5 When plug headers are specified by the purchaser for vertical tube heaters, two-hole plug headers shall
be installed on the top of the coil and one-hole Y-fittings installed at the bottom of the tubes.
8.3.6 Headers and corresponding plugs shall be match-marked by 12 mm (0.5 in.) permanent numerals and
installed in accordance with a fitting-location drawing.
8.3.7 Minimum tube center-to-center dimensions shall be as shown in Table 5.
8.3.8 Plugs and screws shall be assembled in the fittings with an approved compound on the seats and
screws to prevent galling.
30
Table 5—Tube Center-to-center Dimensions
Tube Outside Diameter Header Center-to-center Dimension

mm in. mm in.
60.3 2.375 101.6 4.00 a
73.0 2.875 127.0 5.00 a
88.9 3.50 152.4 6.00 a
101.6 4.00 177.8 7.00 a
114.3 4.50 203.2 8.00 a
127.0 5.00 228.6 9.00
141.3 5.563 254.0 10.00 a
152.4 6.00 279.4 11.00
168.3 6.625 304.8 12.00 a
193.7 7.625 355.6 14.00
219.1 8.625 406.4 16.00 a
273.1 10.75 508.0 20.00 a
NOTE Center-to-center dimensions are applicable only to manufacturers’ standard header pressure ratings for 5850 kPa
(850 psig) nominal fittings.
a This center-to-center dimension equals two times the corresponding nominal size and is based on the center-to-center
dimension for short-radius welded return bends.
8.4 Materials
8.4.1 Return bends shall be seamless and the metallurgy selected shall be equivalent to the tubes or be
similar but with an equal or greater strength and degradation resistance.
8.4.2 Return bend and plug header material shall be in accordance with the material specifications in Table 6
or to other specifications when specified or agreed by the purchaser.
Table 6—Pressure Part Fittings Materials
a
ASTM Specifications
Material
Forged Wrought Cast
A105
Carbon steel A234, WPB A216, WCB
A181, class 60 or 70
C-1/2Mo A182, F1 A234, WP1 A217, WC1
11/4Cr-1/2Mo A182, F11 A234, WP11 A217, WC6
21/4Cr-1Mo A182, F22 A234, WP22 A217, WC9
3Cr-1Mo A182, F21 — —
5Cr-1/2Mo A182, F5 A234, WP5 A217, C5
9Cr-1Mo A182, F9 A234, WP9 A217, C12
9Cr-1Mo-V A182, F91 A234, WP91 A217, C12A
31
b
9Cr-2Si-1Cu — — —
10.5Cr-V A182, F115 A234, WP115 —
18Cr-8Ni Type 304 A182, F304 A403, WP304 A351, CF8
18Cr-8Ni Type 304H A182, F304H A403, WP304H A351, CF10
18Cr-8Ni Type 304L A182, F304L A403, WP304L A351, CF3
16Cr-12Ni-2Mo Type 316 A182, F316 A403, WP316 A351, CF8M
16Cr-12Ni-2Mo Type 316H A182, F316H A403, WP316H A351, CF10M
16Cr-12Ni-2Mo Type 316L A182, F316L A403, WP316L A351, CF3M
18Cr-10Ni-3Mo Type 317L A182, F317L A403, WP317L A351, CG3M
18Cr-10Ni-Ti Type 321 A182, F321 A403, WP321 —
18Cr-10Ni-Ti Type 321H A182, F321H A403, WP321H —

b
18Cr-10Ni-Nb Type 347 A182, F347 A403, WP347 A351, CF8C
b
18Cr-10Ni-Nb Type 347H A182, F347H A403, WP347H A351, CF8C
b
18Cr-10Ni-Nb Type 347LN A182, F347LN A403, WP347LN A351, CF8C
c
18Cr-10Ni-3Cu-Nb A182, F347LNCuB A403, WPS34752 —
Nickel alloy 800H/800HT d B564 B366 A351, CT-15C
A351, CK-20
25Cr-20Ni A182, F310 A403, WP310
A351, HK40
a No applicable ASTM flange or fittings specifications exist for 9Cr-2Si-1Cu at the tim e of publication.
b or equivalent materials from the applicable pressure design code.
c Niobium (Nb) was formerly called columbium (Cb).
dMinimum grain size shall be ASTM #5 or coarser.
8.4.1 Cast fittings shall have the material identification permanently marked on the fitting with raised letters
or by using low-stress stamps.
9 Piping, Terminals, and Manifolds
9.1 General
9.1.1 The minimum corrosion allowance shall be in accordance with 7.1.2.
9.1.2 All flanges shall be welding-neck flanges.
9.1.3 Piping, terminals, and manifolds external to the heater enclosure shall be in accordance with the
pressure design code, e.g. ASME B31.3, or purchaser approved equivalent.
9.1.4 Pressure components external to the heater enclosure shall be selected for the same design pressure
as the connecting tubes and for a design temperature equal to the fluid design temperature at that location.
9.1.5 Manifolds inside a header box shall be designed in accordance with the pressure design code, e.g.
ASME B31.3, or purchaser approved equivalent.
9.1.6 Manifolds inside a header box shall be selected designed for the same design pressure as the
connecting tubes and for a design temperature equal to the maximum calculated temperature at that location plus
32
a minimum of 30 ºC (55 ºF).
● 9.1.7 The purchaser shall specify when inspection openings are required.
NOTE When inspection openings are required, if agreed by the purchaser, terminal flanges may be used when pipe
sections are readily removable for inspection access.
9.1.8 Threaded connections shall not be used.
● 9.1.9 The purchaser shall specify when low-point drains and high-point vents are required, in which case
they shall be accessible from outside the heater casing.
9.1.10 Manifolds and external piping shall be located so as not to block access for the removal of single
tubes or hairpins.
9.2 Allowable Movement and Loads

9.2.1 Heater terminals, shall be designed to accept the simultaneous application of allowable forces (F),
moments (M), and movements (± x, y, and z) in the corroded condition as shown in Figure 4 - Table 7 and Table
8 for tubes, and Figure 5 - Table 9 and Table 10 for manifolds.
9.2.2 Non-piped auxiliary connections, such as vents, drains, and cleaning connections, are excluded from
the requirements of 9.2.1.
● 9.2.3 The purchaser shall specify any requirements beyond the requirements of 9.2.1 and 9.2.2.
● 9.2.4 The type of analysis applied shall be specified or agreed with the purchaser.
a) Horizontal Tubes b) Vertical Tubes

Key
1 tube centerline
Figure 4—Diagram of Forces for Tubes
Table 7—Allowable Forces and Moments for Force
Force Moment
Pipe Size Fx Fy Fz Mx My Mz
33
DN (NPS)
N (lbf) N (lbf) N (lbf) N⋅m (ft⋅lbf) N⋅m (ft⋅lbf) N⋅m (ft⋅lbf)
50 (2) 445 (100) 890 (200) 890 (200) 475 (350) 339 (250) 339 (250)
75 (3) 667 (150) 1334 (300) 1334 (300) 610 (450) 475 (350) 475 (350)
100 (4) 890 (200) 1779 (400) 1779 (400) 813 (600) 610 (450) 610 (450)
125 (5) 1001 (225) 2002 (450) 2002 (450) 895 (660) 678 (500) 678 (500)
150 (6) 1112 (250) 2224 (500) 2224 (500) 990 (730) 746 (550) 746 (550)
200 (8) 1334 (300) 2669 (600) 2669 (600) 1166 (860) 881 (650) 881 (650)
250 (10) 1557 (350) 2891 (650) 2891 (650) 1261 (930) 949 (700) 949 (700)
300 (12) 1779 (400) 3114 (700) 3114 (700) 1356 (1000) 1017 (750) 1017 (750)
Table 8—Allowable Movements for Tubes
Allowable Movement mm (in.)
Terminals Horizontal Tubes Vertical Tubes
Δx Δy Δz Δx Δy Δz
Radiant a a +25 (+1) 25 (1) a a 25 (1) 25 (1)
Convection a a +13 (+0.5) 13 (0.5) — — — — — —
NOTE Except where noted, the above movements are allowable in both directions (±).
a To be specified by heater supplier.
a) Horizontal Manifold b) Vertical Manifold

Key
1 manifold centerline
Figure 5—Diagram of Forces for Manifolds
Table 9—Allowable Forces and Moments for Manifolds

Manifold Force Moment
Size
DN (NPS) Fx Fy Fz Mx My Mz
34
N (lbf) N (lbf) N (lbf) N⋅m (ft⋅lbf) N⋅m (ft⋅lbf) N⋅m (ft⋅lbf)

150 (6) 2224 (500) 4448 (1000) 4448 (1000) 1980 (1460) 1492 (1100) 1492 (1100)
200 (8) 2668 (600) 5338 (1200) 5338 (1200) 2332 (1720) 1762 (1300) 1762 (1300)
250 (10) 3114 (700) 5782 (1300) 5782 (1300) 2522 (1860) 1898 (1400) 1898 (1400)
300 (12) 3558 (800) 6228 (1400) 6228 (1400) 2712 (2000) 2034 (1500) 2034 (1500)
350 (14) 4004 (900) 6672 (1500) 6672 (1500) 2902 (2140) 2170 (1600) 2170 (1600)
400 (16) 4448 (1000) 7117 (1600) 7117 (1600) 3092 (2280) 2305 (1700) 2305 (1700)
450 (18) 4893 (1100) 7562 (1700) 7562 (1700) 3282 (2420) 2441 (1800) 2441 (1800)
500 (20) 5338 (1200) 8006 (1800) 8006 (1800) 3471 (2560) 2576 (1900) 2576 (1900)
Table 10—Allowable Movements for Manifolds
Allowable Movement
Terminals Horizontal Manifolds Vertical Manifolds
Δx Δy Δz Δx Δy Δz
Radiant 13 (0.5) 0 (0) a a 0 (0) 13 (0.5) a a
Convection 13 (0.5) 0 (0) a a — — — — — —
NOTE The above movements are allowable in both directions (±).

a Δz is to be specified by heater supplier.
9.3 Materials
External crossover piping shall be of the same metallurgy as the preceding heater tube; internal crossover piping
shall be of the same metallurgy as the radiant tubes.
10 Tube Supports API Staff Note: no changes in e5.2 except for the following:
>>>RW - Change “vendor” to “supplier” as shown:
10.1.3Top-supported vertical tubes shall include bottom guides. Bottom-supported vertical tubes shall include
top guides.
NOTE Additional tube guides may be included as deemed necessary by the supplier and/or purchaser.
10.1.5 The potential for lateral movement of horizontal radiant tubes off the supports caused by process
related events shall be considered in the tube support design when specified by the supplier, purchaser, or
process licensor. The design load for positive containment features shall be agreed upon between the supplier
and purchaser prior to the commencement of engineering design of the positive containment features.
Table 1011 – revise table header to include reference to a note (same as Table 6 etc.) “ASTM Specifications a”
followed by; “a or equivalent materials from the applicable pressure or structural design code.”
>>>RW – API Staff; Please confirm Table numbers throughout the document – Table as referenced above
should become Table 11. This is difficult to do with a fragmented / partial document.
11 Refractory Linings (API Staff Note: no changes in e5.2)
12 Structures and Appurtenances (API Staff Note: replace section 12 with the
35
following)
12.1 General
12.1.1 Unless otherwise specified, structural steel shall be designed, fabricated, and tested in accordance with
the project specifications and the structural design code.
12.1.2 Minimum design loads for wind and earthquake shall conform to the structural design code.
12.1.3 Platform live loads shall be in accordance with the structural design code.
12.1.4 Structures and appurtenances shall be designed for all applicable load conditions expected during
shipment, erection, operation, and maintenance. Cold-weather conditions shall be considered, particularly when
the fired heater is not in operation. These load conditions shall include, but are not limited to, dead load, wind
load, earthquake load, live load, snow load, and thermal load.
● 12.1.5 When an internal pressure is specified by the purchaser, the load condition created by that internal
pressure shall be added to the list of loads in 12.1.4 when designing structures.
12.1.6 When the fired heater structural design is complete, the supplier shall calculate the maximum load condition that
could be created by internal pressure without violating the structural design code. The supplier shall then calculate the internal
pressure necessary to create that load.
NOTE 1 Appurtenances are specifically excluded from the scope of 12.1.5 and 12.1.6.
NOTE 2 The internal pressure calculated in 12.1.6 may be greater than or equal to the internal pressure specified by the
purchaser in 12.1.5.
12.1.7 Design metal temperature of structures and appurtenances shall be the calculated metal temperature
plus 55 °C (100 °F), based on the maximum flue gas and/or combustion air temperature expected for all
operating modes with an ambient temperature of 27 °C (80 °F) with zero wind velocity (see11.1.2).
12.1.8 The effect of elevated design temperature on yield strength and modulus of elasticity shall be taken into
account (see 12.5.5).
12.1.9 The material of the structures and appurtenances for load bearing members shall consider all load
conditions at the lowest specified ambient temperature when the fired heater is not in operation.
12.2 Structures
12.2.1 All loads from the tubes and headers shall be supported by the structural steel and shall not be
transmitted into the refractory.
12.2.2 Structural steel shall be designed to permit lateral and vertical expansion of all heater parts.
12.2.3 Heater casing shall be plate of a minimum thickness of 5 mm (3/16 in.), which shall be reinforced
against warping. Casing, if calculated to resist buckling stresses, shall have a minimum thickness of 5 mm (3/16
in.).
12.2.4 Floor plates shall have a minimum thickness of 6 mm (1/4 in.). Maximum unstiffened area shall not be
2 2
more than 1.4 m (15 ft ).
12.2.5 External connections between heater-casing plate shall be fully sealed by welding to prevent air and
water infiltration. Skip or stitch welding shall not be permitted.
● 12.2.6 The heater structure shall be capable of supporting ladders, stairs, and platforms in locations where
installed or where specified by the purchaser for future use.
36
12.2.7 Roof design shall prevent the holdup of water e.g., from rain or snow, and shall allow for an
unobstructed pathway for runoff of rainwater following one or more of the following measures:
a) Unobstructed runoff shall be accomplished by arrangement of structural members and drain openings and
by sloping the roof, or with a secondary roof for weather protection.
b) When roof members obstruct the open pathway for runoff, minimum 25 mm X 50 mm (1 in. x 2 in.) slots
shall be made in any roofline crossmembers that would obstruct flow of water.
c) Minimum roof slope shall be 6 mm per 3 m (1/4 in per 10 ft) or a 25 mm (1 in) drop from the centerline of
the heater to the outside edge, whichever is greater.
12.2.8 When pitched roofs are provided for weather protection, eaves and gables shall prevent the entry of
windblown rain or snow.
12.2.9 Horizontally oriented stiffening members shall have a minimum of 25 mm X 50 mm (1 in. x 2 in.) slots
between all areas that can collect rainwater.
● 12.2.10 When fireproofing is specified by the purchaser, the main structural columns of the heater from the
baseplate to the floor level plus the main floor beams shall be designed for the addition of 50 mm (2 in.) of
fireproofing unless otherwise specified.
12.2.11 Heaters with horizontal tubes that have return bends inside the firebox shall have removable end
panels or panels in the sidewalls to provide access to the return-bend welds.
12.2.12 Duct structural systems shall support ductwork independent of expansion joints.
12.2.13 The casing shall be reinforced at the burner mounting to maintain the burner alignment during
operation.
12.2.14 The floor deflection limit shall not exceed 1/100th of the span for the design static loads. Central posts
shall be used as required and to the extent agreed by the purchaser.
12.3 Header Boxes, Doors, and Ports

12.3.1 Header Boxes
12.3.1.1 Each header box shall allow for the total tube expansion. A minimum clearance of 75 mm (3 in.)
shall be provided between the header box door refractory and the header in the hot position.
12.3.1.2 Header boxes shall be bolted on all sides. Header boxes shall be removable with externally
through-bolted connections.
12.3.1.3 Lifting lugs shall be provided on header box panels weighing greater than 50 kg (110 lb). Handles
shall not be used on panels exceeding 50 kg (110 lb) in weight.
12.3.1.4 Header boxes, including doors, shall be of 5 mm (3/16 in.), minimum steel plate reinforced against
warping during operation and when removed.
● 12.3.1.5 When specified by the purchaser, to minimize flue gas bypassing, horizontal partitions shall be
provided in convection-section header boxes at a spacing no greater than 1.5 m (5 ft).
● 12.3.1.6 When horizontal partitions in convection-section header boxes are specified, the purchaser shall
define partition material design temperature.
12.3.1.7 Gaskets shall be used in all header-box joints to achieve airtightness.
37
12.3.2 Tube Penetration Seals

12.3.2.1 Where terminals and crossovers protrude through the header box, the opening around the coil shall
be sealed to minimize leakage.
12.3.2.2 Tube penetration seals shall be flexible and sized to account for thermal expansion and minimize
leakage.
12.3.2.3 Tube penetration seals shall be attached with a collar welded to the casing or header box
12.3.3 Doors and Ports

12.3.3.1 Two access doors having a minimum clear opening of 915 mm × 915 mm (36 in. × 36 in.) shall be
provided for each radiant chamber of a box or cabin heater. Where space is not available due to thermal design
considerations, the largest possible opening shall be provided, subject to approval by the purchaser.
12.3.3.2 One access door having a minimum clear opening of 760 mm × 760 mm (30 in. × 30 in.) shall be
provided in the floor for vertical cylindrical heaters. Where space is not available due to thermal design
considerations, the largest possible opening shall be provided, subject to approval by the purchaser. A bolted and
gasketed access door of equivalent size or larger than floor access shall be provided in any air plenum below the
floor access.
12.3.3.3 One access door having a minimum clear opening of 610 mm × 610 mm (24 in. × 24 in.), or 610 mm
(24 in.) in diameter, shall be provided in the stack or breeching for access to the damper and convection sections.
12.3.3.4 One tube-removal door having a minimum clear opening of 460 mm × 610 mm (18 in. × 24 in.) shall
be provided in the arch of each radiant chamber of vertical tube heaters.
12.3.3.5 Access doors shall be through-bolted to minimize air ingress during operation. Access doors
weighing greater than 50 kg (110 lb) require lifting lugs.
NOTE 1 Handles should not be used on doors exceeding 50 kg (110 lb) in weight.
NOTE 2 Observation ports may be integrated with access doors.
NOTE 3 Refractory around access doors should be designed and installed to prevent hot flue gas or radiation from causing
damage to the door and mounting frame.
12.3.3.6 Floor access doors shall have a mechanical support device installed to assist during opening.
12.3.3.7 Access doors having a minimum clear opening of 610 mm × 610 mm (24 in. × 24 in.) shall be
provided to ducts, plenums, and at all duct connections to preheaters, control dampers, and guillotines.
12.3.3.8 Observation doors and ports shall be provided for viewing and IR inspection of radiant tubes and
convection section shield tubes, including tube guides, radiant and shield tube supports.
12.3.3.9 Observation doors and ports shall be provided for viewing all burner flames for proper operation and
for light-off.
12.4 Ladders, Platforms, and Stairways

12.4.1 Platforms shall be provided as follows:
a) at burner and burner controls that are not accessible from grade;
b) at both ends of the convection section for maintenance purposes;
c) at damper and sootblower locations for maintenance and operation purposes;
38
d) at all observation ports and firebox-access doors not accessible from grade;
e) at auxiliary equipment, such as steam drums, fans, drivers, and air preheaters, as required for operating
and maintenance purposes;
f) at all areas necessary to meet the requirements of 15.5;
g) connected when at the same elevation within a 1.8 m (6 ft) radius of each;
● h) to connect to platforms on adjacent equipment when specified by the purchaser.
12.4.2 Vertical cylindrical heaters shall have a full circular platform at the floor level.
● 12.4.3 The purchaser shall specify the extent of ladders and platforms for access to observation ports for
cylindrical heaters with a casing diameter 3 m (10 ft) or less.
NOTE Individual ladders from grade and platforms to each observation door may be considered.
● 12.4.4 The purchaser shall specify instrumentation dimensions in consideration of maintenance access and
platform sizing.
12.4.5 Platforms shall have a minimum clear width as follows:
a) operating platforms: 915 mm (36 in.),
b) maintenance platforms: 915 mm (36 in.),
c) walkways: 760 mm (30 in.).
● 12.4.6 Platforms intended for use during flue gas analyzer maintenance shall have the following minimum
dimensions:
a) perpendicular from the face of the flue gas analyzer mounting flange to the opposite edge of the platform:
1.5 mm (60 in.)
b) parallel to the flue gas analyzer mounting flange face:
i) for a single flue gas analyzer in a location as specified in 15.1.3; 2.1 m (84 in.) wide with equal space
to each side of the flange.
ii) for two flue gas analyzers in a location as specified in 15.1.3; 2.9 m (114 in.) wide with equal space to
the side of each flange
● 12.4.7 Platform decking shall have a minimum thickness of 6 mm (1/4 in.) and be checkered plate or 25 mm ×
5 mm (1 in. × 3/16 in.) open grating, as specified by the purchaser.
12.4.8 Stair treads shall be open grating with a checkered plate nosing.
12.4.9 Dual access shall be provided to each operating platform, except if the individual platform length is less
than 6.0 m (20 ft).
12.4.10 An intermediate landing shall be provided if the vertical rise exceeds 7.3 m (24 ft) for ladders and 4.5 m
(15 ft) for stairways.
12.4.11 Ladders shall be caged from a point 2.3 m (7.5 ft) above grade or any platform. A self-closing safety
39
gate shall be provided for all ladders serving platforms and landings. Ladders shall be arranged for side step-off;
step- through ladders shall not be used unless specified or agreed by the purchaser.
12.4.12 Stairs shall have a minimum width of 760 mm (30 in.), a minimum tread width of 240 mm (9.5 in.), and
a maximum riser of 200 mm (8 in.). The slope of the stairway shall not exceed a 9 (vertical) to 12 (horizontal)
ratio.
12.4.13 Headroom over platforms, walkways, and stairways shall be a minimum of 2.1 m (7 ft).
12.4.14 Handrails shall be provided on all platforms, walkways, and stairways. Stairways shall be equipped with
grab rails.
12.4.15 Handrails, ladders, and platforms shall be arranged so as not to interfere with tube handling. Where
interference exists, removable sections shall be provided.
12.4.16 The gap between the toe plate and casing or adjacent steel shall not exceed 75 mm (3 in.).
12.5 Materials
● 12.5.1 Materials for service at design ambient temperatures below −30 °C (−20 °F) shall be as specified by
the purchaser.
NOTE For ambient temperatures below −20 °C (−5 °F), special low-temperature steels should be considered.
12.5.2 The mechanical properties and the chemical composition of structural, alloy, or stainless steels shall
comply with the requirements of this standard.
12.5.3 For metal temperatures lower than 425 °C (800 °F), stacks, ducts, and breeching shall be constructed
with material in accordance with the structural design code.
EXAMPLE ASTM A36, ASTM A242, ASTM A572, ASTM A588 or equivalent materials from the structural design
code.
12.5.4 If metal temperatures exceed 425 °C (800 °F), stainless or alloy steels shall be used.
12.5.5 The mechanical properties of the steels at temperatures between 20 °C (70 °F) and 425 °C (800 °F)
shall be determined according to the material properties published in ASTM STS-1 or equivalent materials.
12.5.6 Bolting materials shall be in accordance with the structural design code.
EXAMPLE 1 When the minimum service temperature is –18 °C (0 °F) or higher; ASTM A307, ASTM A325, ASTM
A193-B7, or equivalent materials.
EXAMPLE 2 When the minimum service temperature is below –18 °C (0 °F); ASTM A193-B7 bolts with ASTM A194-
2H nuts, ASTM A320-L7 bolting, or equivalent materials.
EXAMPLE 3 Refer to the applicable structural design code for limitations on welding of bolting materials (example no
welding is permitted on ASTM A320-L7 or ASTM A193-B7 materials).
13 Stacks, Ducts, and Breeching (API Staff Note: replace section 13 with the
following)
13.1 General
● 13.1.1 The design of stacks, ducts, and breechings shall be in accordance with the applicable provisions of the
codes and standards specified by the purchaser.
40
13.2 Design Considerations

13.2.1 Stacks shall be self-supporting and shall be bolted to their supporting structure.
● 13.2.2 Stack intermediate construction shall be performed with full-penetration welding or, if agreed by the
purchaser, shall be bolted.
13.2.3 Breeching and ducting shall be of welded or bolted construction.
13.2.4 External attachments to stacks shall be seal-welded.
13.2.5 Stacks, ducts, and breeching mounted on concrete shall be designed to prevent concrete temperatures
in excess of 150 °C (300 °F).
13.2.6 Connections between stacks and flue gas ducts shall not be welded.
13.2.7 The metallurgy for the top 1 m (3 ft) of the stack shall be stainless steel for oil fired and fuel gas heaters
with greater than 100 ml/m3 (100 ppmv) H2S in the fuel gas
13.2.8 A stainless steel metal ring shall be provided at the top of the stack lining refractory to protect its
horizontal surface from the weather.
13.2.9 Linings shall be provided in steel stacks for one or more of the following purposes:
a) to protect structural steel from gases of excessively high temperature,
b) corrosion protection,
c) to maintain the flue gas temperature at least 20 °C (35 °F) above the acid dew point.
NOTE 1 Other considerations may include fire protection or to reduce the potential for aerodynamic instability.
NOTE 2 The suitability of specialty linings other than monolithic refractory should be discussed with the manufacturer, but
consideration should be given to their strength, flexibility, thermal properties, and resistance to chemical attack
13.2.10 Castable linings shall be secured to stacks, ducts, and breeching by suitable
anchorage in accordance with Section 11.
13.2.11 All openings and connections on the stack, duct, or breeching shall be sealed to prevent air or
flue gas leakage.
13.2.12 Breeching shall have a minimum clear distance beyond the last (present or future) convection row of
0.8 m (2.5 ft) for access and flue gas distribution.
13.2.13 At least one take-off shall be provided every 12 m (40 ft) of convection- section tube length.
13.2.14 Stacks, ducts, and breeching shall be designed for all applicable load conditions expected during
shipment, erection, and operation. Snow and ice shall be considered, particularly when the fired heater is
not in operation. These load conditions shall include, but not be limited to, dead load, wind load, earthquake
load, live load, and thermal load.
13.2.15 The combination of loads that could occur simultaneously to create the maximum load condition
shall be the design load, but in no case shall individual loads create stresses that exceed those permitted in
13.4. Wind and earthquake loads shall not be considered as acting simultaneously.
13.2.16 The minimum thickness of the stack shell plate shall be 6 mm (1/4 in.), including corrosion
allowance. The minimum corrosion allowance shall be 1.6 mm (1/16 in.) for lined stacks and 3 mm (1/8 in.) for
41
unlined stacks.
13.2.17 The minimum number of anchor bolts for any stack shall be eight.
13.2.18 Lifting lugs on stacks, if required, shall be designed for the lifting load as the stack is raised from a
horizontal to a vertical position.
● 13.2.19 The purchaser shall specify when single piece lifting of multiple stack sections is required.
13.2.20 Design metal temperature of stacks, ducts, and breeching shall be the calculated metal
temperature plus 50 °C (90 °F), based on the maximum flue gas temperature expected for all operating
modes with an ambient temperature of 27 °C (80 °F) and with zero wind velocity.
13.2.21 The minimum thickness of breeching and duct plate shall be 5 mm (3/16 in.).
13.2.22 Ducts and breeching shall be stiffened to prevent excessive warpage and deflection. Deflection of
castable refractory lined ducts and breeching shall be limited to 1/360 of the span. Deflection of other ducts and
breeching shall be limited to 1/240 of the span.
13.3 Design Methods

NOTE Where no specific requirements are given by the purchaser, one of the methods given in H.2 or H.3 should be
adopted.
13.4 Static Design

13.4.1 All stacks shall be designed as cantilever beam columns.
13.4.2 Linings shall not be considered as contributing to the strength of the stack, duct, or breeching.
13.4.3 Discontinuities in the stack shell plate, such as conical-to-cylindrical junctions and noncircular
transitions, shall be designed so that the combined membrane and bending stresses in the stack shell or
stiffening rings do not exceed 90 % of the minimum yield strength of the respective materials at design
temperature.
13.4.4 Openings cut into the stack shall be limited in size to a clear width no greater than two-thirds of the
stack diameter. For two openings opposite each other, each chord shall not exceed the stack radius. Openings
shall be reinforced to fully restore the required structural capacity of the uncut section.
13.4.5 Apertures in the stack shell plates, other than flue inlets, shall have the corners radiused to a
minimum of 10 times the plate thickness.
13.4.6 Changes in cylindrical stack diameters shall be made with cones having an apex angle of 60° or less.
13.4.7 Ring stiffeners provided to carry wind pressure should be designed for the circumferential bending
moments.
NOTE Circumferential bending moments due to wind pressure may be neglected in unstiffened cylindrical shells if the ratio
R/t ≤ 160, where R is the radius and t is the corroded thickness of the shell.
13.4.8 Stiffening rings are required if t ≤ (5M/9Fys)0.5 and shall be provided as follows:
a) ring spacing limits: 1 ≤ Hs/D < 3 (1)
b) ring section modulus required: Z ≥ HsM/(0.6 Fyr) (2)
42
where
M is the maximum circumferential moment per unit length of shell, expressed in newton meters per
meter (inch-pounds per inch);
Fys is the minimum yield strength of shell material at design temperature, expressed in Newtons per
square millimeter (pounds per square inch);
t is the corroded shell thickness, expressed in millimeters (inches);
Hs is the ring spacing, expressed in millimeters (inches);
D is the shell diameter, expressed in millimeters (inches);
Z is the section modulus of ring, expressed in cubic millimeters (cubic inches);
Fyr is the minimum yield strength of ring stiffener at the shell design temperature, expressed in Newtons
per square millimeter (pounds per square inch).
13.4.9 Stack deflection due to static wind loads shall not exceed 1 in 200 of stack height, calculated from the
base of the stack, based on the shell-plate thickness less 50 % of the corrosion allowance and without considering
the presence of a lining.
13.5 Wind-induced Vibration Design

13.5.1 A dynamic analysis of the stack shall be made to determine its response to wind and earthquake
action.
NOTE 1 If no specific requirements are given by the purchaser, the methods given in Annex H should be adopted for the
dynamics due to wind.
NOTE 2 If the critical wind speed for the first mode of vibration of the stack is 1.25 times higher than the maximum (hourly
mean) design wind speed (evaluated at the top of the stack), dynamic loads resulting from cross-wind response need
not be included in the design load.
13.5.2 If analysis indicates that excessive vibrations due to cross-winds are possible, one of the following
methods to reduce vortex-induced amplitudes shall be used.
a) Increase mass and structural damping characteristics (e.g. use of refractory lining).
b) Use a mass damper (e.g. tuned pendulum damper).
● c) Use aerodynamic devices (e.g. helical or vertical strakes as described in 13.5.3 and 13.5.4), the choice of
which shall be specified or agreed by the purchaser.
NOTE Annex H gives recommendations regarding the application of spoilers or strakes.
d) Modify stack length and/or diameter until acceptable vibration characteristics are achieved.
13.5.3 If strakes are required to disrupt wind-induced vibration, they shall be used on at least the upper third of
the stack height.
13.5.4 Helical strakes shall consist of three rectangular strakes of 6 mm (1/4 in.) thickness at 120° spacing
with a pitch of five diameters and a projection of 0.1 diameters.
43
NOTE If a stack is positioned within close proximity of other tall structures, consideration should be given to the
possibility of buffeting effects.
13.5.5 If a stack is positioned adjacent to another stack or tall cylindrical vessel, the minimum spacing
between centers shall be 4d, where d is the largest diameter of the adjacent structures.
NOTE Interference effects may be neglected for spacing between centers of greater than 15d.
13.5.6 For a stack downwind of an adjacent stack or a tall vessel, interference effects shall be accounted for
by an increase in wind load as defined in ASTM STS-1.
13.6 Materials
The material of the stack, breeching, and duct shall be adequate for all load conditions at the lowest specified
ambient temperature when the fired heater is not in operation (see 12.5).
14 Burners and Auxiliary Equipment API Staff Note: no changes in e5.2 other than
- remove bullet from 14.1.9)
14.1.9 Gas pilots shall be provided for each burner, unless otherwise specified.
44
15 Instrumentation and Auxiliary Connections (API Staff Note: replace 15.1.3 with the
following and add 15.1.4 to e5.2)
15.1.3 Flue Gas Analyzer Locations
15.1.3.1 Flue gas analyzer connections shall be provided at the exit of the radiant section or before the inlet to
the convection section, and at the convection section exit prior to the flue gas damper. Unless otherwise
specified, the analyzer location arrangement shall be as defined in Table X.
API Staff Note: Please number table and figures accordingly
Table X-- Flue Gas Analyzer---Mounting Flange Locations
Point-based Measurement Path-averaged Measurement
The flue gas analyzer located such that it is not Flue gas analyzer connection(s) placed as shown for
influenced by any other flue gas sources other than the Heater Types A-F in Figure YY.
source to be measured.
Flue gas analyzer connection(s) located as shown for

a Two pairs of nozzles placed in each of these locations.
Heater Types A-F in Figure ZZ .
The flue gas connection(s) located to have no The flue gas analyzer connection(s) in an area where
interference from convection or radiant tubes and any the beam can cross the path of the flue gas.
associated tube supports.
Flue gas connection(s) installed at the exit of each The flue gas analyzer connection(s) no closer than 2 m
b
independent combustion zone. (6.5 ft) above the highest edge of the flame envelope .
Each pair of flue gas analyzer connection(s) opposed,

Flue gas connection(s) spread as evenly as possible
aligned, and concentric within 2 degrees and stabilized
along the length of the radiant section exit or convection
to move less than 1-2 degrees under all modes of
section entrance.
operation.
Number of connections as follows:
Number of
Effective Convection Tube Length Connections If multiple flue gas analyzers are used, the minimum
distance between flue gas analyzer connections:
≤ 9.1 m (30 ft) 1
460 mm (18 in.)
9.1 m (30 ft) < L ≤ 13.7 m (45 ft) 2
13.7 m (45 ft) < L ≤ 18.3 m (60 ft) 3
a
Heater Types D and F: A single analyze located at the base of the convection section may be used where the
cells are not independently fired.
b
This is the preferred location for path-averaged measurement of flue gas concentration.
45
Figure YY— Heater Layouts - Path Averaged Measurement
Notes
a analyzer located here
b possible alternate location on taller fireboxes
c two pairs of nozzles located here
>>>RW - API Editors – Replace the written notes to the figures with the appropriate notes – a, b, etc.
46
Alternate
location – see
Table X
Alternate location
– see Table X
Figure ZZ— Heater Layouts – Point Based Measurement
Notes
a analyzer located here
b analyzer located here through roof on each cell
c analyzer located here below convection tubes
d analyzer located here through roof tubes on each cell
e alternate location – see Table X
>>>RW - API Editors – Replace the written notes to the figures with the appropriate notes – a, b, etc.
>>>RW – The native files for the above figures belong to API. API Editors to add labels as appropriate according
to the API Style Guide.
● 15.1.3.2 The purchaser shall specify whether point-based or path-averaged measurement is required.
15.1.3.3 A continuous temperature representative of the flue gas path of measurement shall be provided as an
input to the flue gas analyzer.
15.1.3.4 Connections on the heater casing used for analyzer mounting shall be in accordance with the following:
47
a) class PN 20 (ASME class 150) raised face slip-on through-stud flange in accordance with the pressure
design code;
b) flange bolt holes to straddle the natural centerline of the connection;
c) DN 100 (4 NPS) schedule 80 pipe nozzle welded to the outside of the casing with a minimum 200 mm
(8 in.) and maximum 300 mm (12 in.) projection to the flange face;
d) nozzle internal projection not to extend beyond the refractory hot face;
e) supplied with a class PN 20 (ASME class 150) raised face blind flange with appropriate gaskets for the
temperature and corrosive conditions of the flue gas.
15.1.4 Environmental / Regulatory Connections
15.1.4.1 Connections shall be provided in each stack and each take-off to a stack in compliance with
environmental air-quality monitoring requirements, as specified by the regulatory body.
15.1.4.2 Sampling-point locations shall be determined according to environmental requirements regarding

upstream and downstream flow disturbances.
● 15.1.4.3 The purchaser shall specify additional connections to meet applicable governmental or local
environmental requirements.
API Staff Note: Change “vendor” to “supplier” as noted below:
15.1.3.4 The connections shall be DN 100 (4 NPS) schedule 80 pipe with a class PN 20 (ASME class 150)
raised- face flange. The pipe shall be welded to the outside casing plate and project 200 mm (8 in.) to the face of
the flange. The heater supplier shall furnish for each connection a class PN 20 (ASME class 150) blind flange
with appropriate gaskets for the temperature and corrosive conditions of the flue gas. The pipe shall extend to
within 38 mm (1.5 in.) into the heater from the hot-face of the refractory lining.
15.2 Thermowell
• 15.2.1 When specified by the purchaser, the heater supplier shall provide thermowell connections in the
convection to radiant crossovers.
15.2.2 If process-outlet thermowell connections are specified by the purchaser and individual outlets are
provided by the heater supplier, the thermowell connections shall be furnished as part of the outlet piping system.
If an outlet manifold is furnished, the specified thermowell connections shall be provided by the heater supplier.
16 Shop Fabrication and Field Erection (API Staff Note: no changes in e5.2 except as
follows:
API Staff Note: Change “vendor” to “supplier” as noted below:
16.1.2 The supplier shall state the type of protection provided for refractory and insulation to avoid damage
from handling or weather during shipment, storage, and erection.
16.5.3 See 16.1.2. The following shall also apply.
c) The supplier shall identify on the drawings the maximum number of shop-lined sections that can be
stacked and the orientation of sections for shipping and storage purposes.
48
16.5.15 The supplier shall advise the purchaser if any pieces are temporarily fixed for shipping purposes.
Transit and erection clips or fasteners shall be clearly identified on the equipment and the field-assembly
drawings to ensure removal before commissioning of the heater.
16.6.1 It shall be the responsibility of the erector to ensure that the heater is erected in accordance with the
specifications and drawings furnished by the supplier and in accordance with the applicable sections of this
standard.
16.6.5 Field joints between panels shall be sealed in accordance with the heater supplier’s requirements.
17 Inspection, Examination, and Testing (API Staff Note: no changes other than to
remove the bullet from 17.3.2 c) in e5.2)
17.3 Castings Examination
17.3.2 Shield and convection-section cast tube supports shall be examined as follows.
c) c)Radiographic examination of critical sections of the pilot castings shall be performed for each pattern to
confirm soundness of the casting design.
…and change “vendor” to “supplier” as noted below:
17.1.2 The supplier shall examine all individual heater components and their shop-assembled units to ensure
that materials and workmanship are in accordance with applicable standards, specifications, codes, and
drawings.
17.6.1.2 If hydrostatic testing or pneumatic pressure-testing of pressure parts is not considered practical, by
agreement between the purchaser and the supplier, 100 % radiography shall be performed on all circumferential
welds and pneumatic leak-testing shall be performed using air or a nontoxic, nonflammable gas…etc.
17.6.3.2 PMI program methods, degree of examination, PMI testing instruments, and tester qualifications shall
be agreed upon between the purchaser and the supplier prior to manufacturing. PMI shall not be required for
burner components, unless specified by the purchaser.
49
Annex A
(informative)
Equipment Datasheets Comment [A1]: USC Datasheets are

currently under edit
(API Staff Note: no changes in e5.2 other than noted below)

A.1 General
This annex includes datasheets for the following equipment items:
a) fired heater datasheets: 12 sheets (6 in SI units, 6 in USC units);
b) burner datasheets: 6 sheets (3 in SI units, 3 in USC units);
c) air preheater datasheets: 4 sheets (2 in SI units, 2 in USC units);
d) fan datasheets: 4 sheets (2 in SI units, 2 in USC units);
e) sootblower datasheets: 2 sheets (1 in SI units, 1 in USC units);
f) isolation guillotine/isolation blind datasheet; and
g) louver/butterfly damper datasheet.
See Section 5 for instructions on using the equipment datasheets.
NOTE The purchaser should complete, as a minimum, those items that are designated by an asterisk (*).
Changes to Datasheets made by R Wey:
Fired heater data sheets – SI Units:

Change title on fired heater datasheets to Fired Heater Datasheets (no hyphen)
Change kPa to kPa (ga) throughout for static pressure
Sheet 1, top header, change Air-preheater Datasheet to Air Preheater Datasheet
Sheet 2, line 10: APH to air preheater
Fired heater data sheets – USC Units:
Change title on fired heater datasheets to Fired Heater Datasheets (no hyphen)
Change psi to psig throughout for static pressure
Sheet 1, top header, change Air-preheater Datasheet to Air Preheater Datasheet
On page 3 of 6 (both SI and USC), a) insert new line 6 below *minimum/normal/maximum ambient air temperature, °C” that
states *internal pressure (12.1.5)” b) insert new line 7 above the solid line that states “internal pressure (12.1.6)” c) and, adjust
the subsequent line numbers accordingly.
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
Annex B
(informative)
Purchaser’s Checklist 13
This checklist may be used to indicate the purchaser’s specific requirements where this standard provides a
choice or specifies that a decision shall be made. These items are indicated by a bullet () in this standard.
Subsection Item Requirement
4.1 Pressure design code
4.3 Structural design code
4.5 Structural welding code
4.6 Applicable local rules and regulations for the equipment
4.7 Local rules and regulations specified by the purchaser
5.2 k) List of sub-suppliers required? Yes No

5.3.3 d) Structural welding, examination, and test procedures? Yes No
5.3.3 h) Tube-support design calculations required? Yes No
5.3.3 m) Decoking procedures required? Yes No
5.2 f)
5.3.3 q) Noise datasheets required? Yes No
5.4 f)
5.3.5.1 Perform performance tests? Yes No
6.3.2 Space required for future sootblowers, water washing, etc.? Yes No
6.3.4 Sootblowers to be provided? Yes No
6.3.14 Fin tip to fin tip vertical gap and access door requirements Yes No
Ceramic coating on:
6.3.15 tubes? Yes No
refractory? Yes No
Acceptable extended surface type:
7.2.1 a) finned Yes No
b) studded Yes No
Acceptable type of finned extended surface:
7.2.2 solid Yes No
studded Yes No
8.3.4 Plug headers for horizontal tubes? Yes No
8.3.5 Plug headers for vertical tubes? Yes No
Inspection openings required? Yes No
9.1.7
If yes, are terminal flanges acceptable? Yes No
66

Low-point drains required? Yes No
9.1.9
High-point vents required? Yes No
Allowable forces, moments and movements beyond the standard
9.2.3 Yes No
requirements?
9.2.4 Type of terminal stress analysis? _______________________
10.1.5 Tube support positive containment features required by purchaser? Yes No
Tube support design details specified by purchaser? Yes No

10.5.2
Design details: a) or b) ______________________
12.1.5 Internal positive pressure _______________________
______________________
12.2.6 Locations for future platforms, ladders, and stairways
______________________
12.2.11 Fireproofing required? Yes No
12.3.1.5 Horizontal partitions required in convection-section header boxes? Yes No
12.3.1.6 Headbox partition material design temperature (when specified)? _______________________
12.4.1 h) Platforms connecting to adjacent equipment? Yes No
Extent of ladders and platforms for observation ports on small diameter
12.4.3 _______________________
heaters where applicable
12.4.4 Instrumentation dimensions in consideration of access and platforms _______________________
Platform decking requirements:
12.4.6 checkered plate Yes No
open grating Yes No
12.5.1 Acceptable low-temperature materials ______________________
13.1.1 Codes for stacks, ducts and breeching ______________________
13.2.2 Bolting permitted for stack assembly? Yes No
Acceptable aerodynamic devices:
13.5.2 c) helical strakes Yes No
vertical strakes Yes No
Required heater capacity during forced-draft outage and continued ______________________
14.1.12
operation on natural draft ______________________
______________________
14.1.15 Removable gas guns, diffusers or complete burner assembly; specify
______________________
Acceptable sootblower type:
retractable Yes No
14.2.1
automatic Yes No
sequential Yes No
14.4.1.3 Required or preferred damper and damper control: specify Use damper datasheets
14.4.1. 4 Minimum travel time from full open to full close _____________________
14.4.1.13 Required mode of actuation for each damper: specify Use damper data sheets
14.4.1.14 Instrumentation requirements for each damper assembly: specify Use damper data sheets
14.4.3.1 Are damper frames required as an integral part of damper assembly? Yes No
Amount of adjustability, as percentage of full travel, including the use of
14.4.4.3 Use damper data sheets
minimum and maximum travel stops: specify
14.4.5.6 Preferred connection method of damper blade to shaft a b c
67

14.4.7.4 Preferred crank arm attachment method a b c d
Fail position for both loss of control signal and/or loss of motive force:
14.4.8.2 Use damper data sheets
specify
14.4.8.6 Damper drive manual override: yes / no Use damper data sheets
14.4.8.7 Location for operation of manual dampers _______________________
14.4.11.21 Guillotine dampers: self-locking electric or manual _______________________
14.4.11.23 Guillotine dampers: required cycle time (full open to full closed) _______________________
14.4.12.1 Natural draft doors supplied? Yes No
14.4.12.3 Allowable variance from symmetry in combustion air flow to each burner ______________________
15.1.3.2 Point-based or path-averaged flue gas measurement? ______________________
Additional connections to meet applicable governmental or local ______________________
15.1.4.2
environmental requirements. ______________________
15.2.1 Crossover thermowell connections required? Yes No
15.2.2 Outlet thermowell connections required? Yes No
Water washing required?
15.3.2.2 radiant section Yes No
convection section Yes No
15.4.1 Tube-skin thermocouples required? Yes No
______________________
16.1.1 Site receiving and handling limitations
______________________
______________________
16.2.1 f) Charpy impact test requirements
______________________
Galvanizing of handrails, etc.? Yes No
16.4.3 Bolt protection:
galvanizing Yes No
zinc-coating Yes No
______________________
16.5.16 Export crating
______________________
______________________
16.5.17 Long-term storage requirements
______________________
17.1.3 Pre-inspection meetings required prior to the start of fabrication? Yes No
17.3.1 Positive materials identification (PMI) required? Yes No
17.3.2 d) Additional radiography of pilot castings and / or production castings? Yes No
17.3.3 c) Additional inspection of pilot castings and / or production castings? Yes No
Sampling quantities and degree of coverage for radiography of cast return ____________________
17.3.4 c)
bends and pressure fittings ____________________
17.6.1.2 Is pneumatic pressure-testing acceptable instead of hydrostatic? Yes No
______________________
17.6.3.2 PMI requirements
______________________
E.2.3 a) Static pressure at inlet to first piece of equipment in the forced draft? ______________________
E.2.3 c) Static pressure at the fan outlet flange or the evase outlet? ______________________
Static pressure at the inlet to the first piece of equipment in the induced
E.3.3.1 a) ______________________
draft?
68

E.3.3.1 c) Static pressure at the fan outlet flange? ______________________
F.5.2.1 APH with dual draft or natural draft capability? ______________________
Dual draft air preheat systems with natural draft and:
- balanced draft
F.5.2.2 a) ______________________
- forced draft, or
- induced draft.
F.5.2.3 a) Degree of natural operation as a percentage of design absorbed duty? ______________________
F.5.4.1.1 i) Combustion air ducting modeling required? Yes No
F.5.4.4.1 b) Flow control damper installed in each parallel combustion air duct Yes No
F.5.6.5 Ceramic fiber blanket refractory lining? Yes No
F.5.6.7 Ducting external insulation required Yes No
69
ANNEX C
(informative)
Proposed Shop-assembly Conditions
(API Staff Note: no changes in e5.2)
70
ANNEX D
(normative)
Stress Curves for Use in the Design of Tube-support Elements
71
Annex E
(normative)
Fan Process Sizing Requirements

72
Annex F
(normative / informative)
Air Preheat and Ducting Systems
for Fired Heaters in General Refinery Services
API Staff NOTE: Annex F has been completely rewritten including title. This Annex contains two parts; Part I –
normative, F.1 to F.6 and Part II – informative F.7 to F.8. In consideration of the length of the Annex (> 80
pages) and the extensive amount of effort to integrate it into this document with proper format, Annex F is
provided as a separate document for committee review and API editing. The Annex contains a Table of
Contents as well as Table of Figures and Table of Tables. It is requested that API Staff include the full TOC in
the Annex. The TOC could be reduced to minimum of two levels of headings, where applicable e.g. F.4.1.
Please Note – The abbreviation APH has also been changed; formerly used in reference to “air preheater”,
which was a single component (heat exchanger) and now changed to reference an “air preheat system” which
would include an air preheater as one of the components in an APH. This change in terminology has been
made throughout the whole document.
Annex F as currently presented could serve as a stand-alone API Standard in the future.
73
Annex G
(informative)
Measurement of Efficiency of Fired-process Heaters
API Staff Note: no changes in e5.2
74
Annex H
(informative)
Stack Design
API Staff NOTE: Two changes in Annex H for e5.2: Section H.4.2 and Equation (H.28) as noted
below.
H.1 General
H.2 Stability of Steel Shell (API Allowable-stress Method)
H.3 Stability of the Steel Shell (ISO Limit-state Method)
H.4 Wind-induced Vibration Design (API Allowable-stress

Method)
H.4.2 The critical wind velocity, vc, for the modes of vibration of the stack shall be calculated for the
new and corroded conditions according to Equation (H.11). For the first and second modes, respectively,
vc equals vc1, expressed in meters per second (feet per second), and vc2, which is equal to vc1 × 6.0,
expressed in meters per second (feet per second):
vc = f × DAV ⁄ Sr (H.11)
where:
f is the frequency of transverse vibration of the stack, in hertz;
DAV is the average stack shell diameter for its top 33 % of height, in meters (feet);
Sr is the Strouhal number, equal to 0.2 (dimensionless).
The determination of f requires a rigorous analysis of the stack and supporting structure. Equation (H.12) is
used to calculate the frequency of transverse vibration, f, for a stack of uniform mass distribution and constant
cross section with a rigid (fixed) base:
(H.12)
where:
E is the modulus of elasticity at design temperature, in Newtons per square meter (pounds per square
inch);
I is the moment of inertia of stack cross section, in meters to the fourth power (inches to the fourth
power);
W is the weight per unit height of stack, in Newtons per meter (pounds per inch);
H is the overall height of stack, in meters (inches);
g is the acceleration due to gravity [equal to 9.806 m/s2 (386 in./s2)].
75
Solutions for stacks not covered by this equation shall be subject to the approval of the purchaser.
H.5.8
-3 6
In (H.28) change (0.1082 X 10 ) to 0.1082 X 10 )
76
ANNEX I
API Staff NOTE: Annex I (Measurement of Noise from Fired-process Heaters) has no
changes to e5.2.
77
Annex J
(informative)
API Staff Note: no changes in e5.2
78
Annex K
(informative)
Burner-to-Burner and Burner-to-Coil Spacing Example Calculations
API Staff Note: no changes to e5.1 in e5.2
79
Annex L
(informative)
Damper Classifications and Damper Controls for Fired Heaters
80
Annex M
(normative)
Ceramic Coating for Outer Surfaces of Fired Heater Tubes, Fiber and
Monolithic Refractories
81
Annex N
(informative)
Ceramic Coating for Outer Surfaces of Fired Heater Tubes, Fiber

Refractories and Monolithic Refractories
82
Annex O
(informative)
Heater Nomenclature--Fired Heaters for General Refinery Service
API Staff Note: Annex O is new in e5.2
O.1 General
In a fired heater, heat liberated by the combustion of fuels is transferred to fluids contained in tubular coils
within an internally insulated enclosure. The type of heater is normally described by the structural
configuration, radiant-tube coil configuration, and burner arrangement. Some examples of structural
configurations are cylindrical, box, cabin, and multicell box. Examples of radiant-tube coil configurations
include vertical, horizontal, helical, and arbor. Examples of burner arrangements include up-fired, down-fired,
and wall-fired. The wall-fired arrangement can be further classified as sidewall, endwall, and multilevel.
Figure O.1 illustrates some typical heater types.
Figure O.2 illustrates typical burner arrangements.
Various combinations of Figure O.1 and Figure O.2 can be used. For example, Figure O.1 c) can employ burner
arrangements as in Figure O.2 a), Figure O.2 b), or Figure O.2 c). Similarly, Figure O.1 d) can employ burner
arrangements as in Figure O.2 a) or Figure O.2 d).
Figure O.3 shows typical components in a horizontal tube fired heater.
Annex F gives guidelines for the design, selection, and evaluation of air-preheat systems. Figure O.1, Figure
O.2, and Figure O.3 show typical air preheat systems.
83
Type A—Box heater with arbor coil Type B—Cylindrical heater with Type C—Cabin heater with
helical coil horizontal tube coil
Type D—Box heater with vertical Type E—Cylindrical heater with Type F—Box heater with horizontal
tube coil vertical coil tube coil
Figure O.1—Typical Heater Types
84
Type A—Up-fired Type B—Endwall-fired
Type C—Sidewall fired Type D—Sidewall-fired multi-level
Figure O.2—Typical Burner Arrangements (Elevation View)

>>>API Staff: These are legacy figures from much earlier editions of API 560, the native file of which are in
your possession. No changes are made to the figure content.
85
Delete Pressure
Relief Door
86
Key
1 mule ear fitting 14 pressure relief door
2 horizontal radiant tubes 14 (15) observation / sight port
3 end tubesheet 15 (16) outside casing plate
4 burners 16 (17) refractory / insulation
5 cast wall hangers 17 (18) stack
6 cast arch tube hangers 18 (19) flue gas duct
7 horizontal convection tubes (bare rows) 19 (20) combustion air duct
8 horizontal convection tubes (extended surface rows) 20 (21) maintenance platform
9 tube support casting 21 (22) structural steel framing
10 return bends 22 (23) various instrumentation connections (typical)
11 space for future tubes 23 (24) header box
12 sootblower openings 24 (25) concrete foundation (by purchaser)
13 access door
Figure 0.3—Typical Components in a Horizontal Tube Fired Heater
>>>RW Comments on Figure O.3 – Heater Components (above) – ACTION for Jean-Marc Rivard - Wood /
Foster Wheeler)
- remove legend form the figure image file; replaced by key in the document as noted above
- remove FW logo / name
- delete 14 – pressure relief door and renumber drawing accordingly
- remove colour and shading – line drawing only, tube OD may be a solid such as in the original Figure 3
- see guidance on the Development and Application of Figures in API Documents
- submit and API image permission form with the revised files
87
Bibliography
>>>APII Staff: Rationalization of the Bibliography has been difficult since the full content of the document is
fragmented (e5.0, e5.1, and e5.2 Annex F). Once the full copy of e5.2 has been assembled, a more accurate
review of the Bibliography and Section 2 can be undertaken.
[1] ISO 13709, Centrifugal pumps for petroleum, petrochemical and natural gas industries
[9] API Standard 536, Post-Combustion NOx Control for Fired Equipment in General Refinery Services
[ } API Standard 541 Data Sheet, Form Wound Squirrel- Cage Induction - Mechanical Equipment Data Sheet
{ ] API Standard 546 Data Sheet, Brushless Synchronous Machines - 500 kVA and Larger – Mechanical
Equipment
[ ] API Standard 547 Data Sheet, General-purpose Form-wound Squirrel Cage Induction Motors 250
Horsepower and Larger – Mechanical Equipment Data Sheet
[10] API Recommended Practice 554, Process Instrumentation and Control
[11] API Recommended Practice 555, Process Analyzers
[ ] API Standard 673 Data Sheet, Centrifugal Fans for Petroleum, Chemical and Gas for Industry Services -
Mechanical Equipment Data Sheet
[14] ASM Metals Handbook 26, Volume 3, Properties and selection: stainless steels, tool materials and special-
purpose metals
[15] ASME B31.3, Process Piping
[16] ASME STS-1, Steel Stacks
[xx] ASME Boiler and Pressure Vessel Code (BPVC), Section VIII: Rules for Construction of Pressure Vessels;
Division 1
5
[xx] ASTM A36/A36M , Standard Specification for Carbon Structural Steel
[xx] ASTM A53/A53M, Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded
and Seamless
[xx] ASTM A105/A105M, Standard Specification for Carbon Steel Forgings for Piping Applications
[xx} ASTM A106/A106M, Standard Specification for Seamless Carbon Steel Pipe for High-Temperature
Service
[XX] ASTM A181/A181M, Standard Specification for Carbon Steel Forgings, for General-Purpose Piping
[xx] ASTM A182/182M, Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges,
Forged Fittings, and Valves and Parts for High-Temperature Service
[xx] ASTM A192/A192M, Standard Specification for Seamless Carbon Steel Boiler Tubes for High-Pressure
Service
[xx] ASTM A193/A193M, Standard Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature
or High Pressure Service and Other Special Purpose Applications
5
ASTM International, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428, www.astm.org.
88
[ ] ASTM A194/A194M, Standard Specification for Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts
for High Pressure or High Temperature Service, or Both
[ ] ASTM A209/A209M, Standard Specification for Seamless Carbon-Molybdenum Alloy-Steel Boiler and
Superheater Tubes
[ ] ASTM A210/A210M, Standard Specification for Seamless Medium-Carbon Steel Boiler and Superheater
Tubes
[ ] ASTM A213/A213M, Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler,
Superheater, and Heat- Exchanger Tubes
[ ] ASTM A216/A216M, Standard Specification for Steel Castings, Carbon, Suitable for Fusion Welding, for
High-Temperature Service
[ ] ASTM A217/A217M, Standard Specification for Steel Castings, Martensitic Stainless and Alloy, for Pressure-
Containing Parts, Suitable for High-Temperature Service
[ ] ASTM A234/A234M, Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for
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[ ] ASTM A240/A240M, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate,
Sheet, and Strip for Pressure Vessels and for General Applications
[ ] ASTM A242/A242M, Standard Specification for High-Strength Low-Alloy Structural Steel
[ ] ASTM A283/A283M, Standard Specification for Low and Intermediate Tensile Strength Carbon Steel Plates
[ ] ASTM A297/A297M, Standard Specification for Steel Castings, Iron-Chromium and Iron-Chromium-Nickel,
Heat Resistant, for General Application
[ ] ASTM A307/A307M, Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod 60,000 PSI
Tensile Strength
[ ] ASTM A312/A312M, Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic
Stainless Steel Pipes
[ ] ASTM A320/A320M, Standard Specification for Alloy Steel and Stainless Steel Bolting for Low-Temperature
Service
[ ] ASTM A325/A325M, Standard Specification for Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum
Tensile Strength
[ ] ASTM A335/A335M, Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature
Service
[ ] ASTM A351/A351M, Standard Specification for Castings, Austenitic, for Pressure-Containing Parts
[ ] ASTM A376/A376M, Standard Specification for Seamless Austenitic Steel Pipe for High-Temperature Service
[ ] ASTM A384/A384M, Standard Practice for Safeguarding Against Warpage and Distortion During Hot-Dip
Galvanizing of Steel Assemblies
[ ] ASTM A385/A385M, Standard Practice for Providing High-Quality Zinc Coatings (Hot-Dip)
89
[ ] ASTM A387/A387M, Standard Specification for Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum
[ ] ASTM A403/A403M, Standard Specification for Wrought Austenitic Stainless Steel Piping Fittings
[ ] ASTM A447/A447M, Standard Specification for Steel Castings, Chromium-Nickel-Iron Alloy (25-12 Class), for
High- Temperature Service
[ ] ASTM A560/A560M, Standard Specification for Castings, Chromium-Nickel Alloy
[ ] ASTM A572/A572M, Standard Specification for High-Strength Low-Alloy Columbium-Vanadium Structural

Steel
[ ] ASTM A588/A588M, Standard Specification for High-Strength Low-Alloy Structural Steel, up to 50 ksi [345
MPa] Minimum Yield Point, with Atmospheric Corrosion Resistance
[ ] ASTM A608/A608M, Standard Specification for Centrifugally Cast Iron-Chromium-Nickel High-Alloy Tubing
for Pressure Application at High Temperatures
[ ] ASTM B366/B366M, Standard Specification for Factory-Made Wrought Nickel and Nickel Alloy Fittings
[ ] ASTM B407/B407M, Standard Specification for Nickel-Iron-Chromium Alloy Seamless Pipe and Tube
[ ] ASTM B564/B564M, Standard Specification for Nickel Alloy Forgings
[18] ASTM C553, Standard Specification for Mineral Fiber Blanket Thermal Insulation for Commercial and
Industrial Applications
[19] ASTM D396, Standard Specification for Fuel Oils
[20] ASTM D975, Standard Specification for Diesel Fuel Oils
[21] ASTM D2880, Standard Specification for Gas Turbine Fuel Oils
25 American Institute of Steel Construction, One East Wacker Drive, Suite 700, Chicago, Illinois 60601, www.aisc.org.
26 ASM International, 9636 Kinsman Road, Materials Park, Ohio 44073, www.asminternational.org.
[22] ASTM D5504, Standard Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous
Fuels by Gas Chromatography and Chemiluminescence
[23] ASTM DS5, Report on the Elevated Temperature Properties of Stainless Steels
[24] ASTM DS5S2, An Evaluation of the Yield, Tensile, Creep, and Rupture Strengths of Wrought 304, 316, 321
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[25] ASTM DS6, Report on the Elevated Temperature Properties of Chromium-Molybdenum Steels
[26] ASTM S6S2, Supplemental Report on the Elevated Temperature Properties of Chromium-Molybdenum
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[27] ASTM DS11S1, An Evaluation of the Elevated Temperature Tensile and Creep Rupture Properties of
Wrought Carbon Steel
90
[28] ASTM DS58, Evaluation of the Elevated Temperature Tensile and Creep Rupture Properties of 3 to 9 %
6
[ ] AWS D1.1/d1.1M , Structural Welding Code—Steel
Chromium-Molybdenum Steels
[29] CICIND2F 27, Model Code for Steel Chimneys
[30] EN 1991 (Eurocode 1), Actions on structures
[31] EN 1993 (Eurocode 3), Design of steel structures
[32] ICBO4F 28, International Building Code
[33] IN-657, Cast Nickel-Chromium-Niobium Alloy for Service Against Fuel-Ash Corrosion—Engineering
Properties, Inco Alloy Products Ltd., Wiggin Street, Birmingham B16 0AJ, UK
[34] MSS SP-53, Quality Standard for Steel Castings and Forgings for Valves, Flanges and Fittings and Other
Piping Components—Magnetic Particle Exam Method16)
[35] MSS SP-55, Quality Standard for Steel Castings for Valves, Flanges and Fittings and Other Piping
Components—Visual Method for Evaluation of Surface Irregularities
[36] MSS SP-93, Quality Standard for Steel Castings and Forgings for Valves, Flanges, and Fittings and Other
Piping Components—Liquid Penetrant Examination Method
[37] NEMA SM 23, Steam Turbines for Mechanical Drive Service
[38] SFSA5F 30, Steel Castings Handbook
[39] Corbett, P. F. and F. Fereday, The SO3 content of the combustion gases from an oil-fired water-tube boiler, J.
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27 Comité International des Cheminées Industrielles, The Secretary, 14 The Chestnuts, Beechwood Park, Hemel
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28 International Code Council, 500 New Jersey Avenue, NW, 6th Floor, Washington, D.C. 20001, www.iccsafe.org.
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[49] Mahajan, Kanti H., Tall Stack Design Simplified, Hydrocarbon Process, September, 1975, p. 217.
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93

API 560 Fired Heaters

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This document is under review as revision to an API Standard; it is under consideration within an API technical committee but has

not received all approvals required for

Fired Heaters for General Refinery

Redline Ballot Draft: Sections 12.1.5-12.1.6 and corresponding material

Note: USC datasheets are currently under edit.

Can: As used in a standard, “can” denotes a statement of possibility or capability.

EN 60079 ISA 51.1 ISO 1940-2:2003 NFPA 70

NOTE 2 See M.2 for normative references specific to ceramic coatings.

API Standard 530, Calculation of Heater Tube Thickness in Petroleum Refineries

ASTM C27, Standard Classification of Fireclay and High-Alumina Refractory Brick

ISO 10684, Fasteners—Hot dip galvanized coatings

SSPC SP 6/NACE No. 3, Commercial Blast Cleaning

3 Terms, Definitions, and Abbreviations

3.1 General Terms and Definitions

NOTE 2 Construction includes installation/erection of purchased equipment.

3.2 Terms and Definitions – Fired Heaters

NOTE: Also referred to as muffle block or quarl.

NOTE The fuel efficiency is calculated using:

− the design excess air level,

− design ambient humidity,

NOTE Excess air is expressed as a percentage.

NOTE Access is afforded by means of hinged doors or removable panels.

NOTE1: Where the fuel efficiency is calculated using:

NOTE Steam is normally the medium used for soot-blowing.

EXAMPLE International Building Code (IBC).

EXAMPLE AWS D1.1/D1.1M

3.3 Terms and Definitions – Refractory

NOTE Also known as bio-fiber, bio-soluble, or low bio-persistence fiber.

EXAMPLE A dense monolithic over insulating monolithic.

AES alkaline earth silicate fiber

APH air preheat system

BTB normalized burner-to-burner spacing

BTC normalized burner-to-coil spacing

HHV higher (gross) heat value

IFB insulating firebrick

LHV lower (net) heating value

MMVF manmade vitreous fiber

NOx oxides of nitrogen, i.e. nitrous oxide, nitric oxide

PMI positive materials identification

RCF refractory ceramic fibers

SCR selective catalytic reduction

SiO2 silicon dioxide

5.1 Purchaser’s Responsibilities

a) startup mode of operation, including;

1) burner lighting state of operation and,

2) ramp-up state of operation.

b) normal mode of operation / turndown state of operation;

c) maintenance mode of operation / coke removal.

5.2 Supplier’s Responsibilities

b) a description of the full scope of supply and work;

e) detailed description of any exceptions to the specified requirement;

● f) when specified by the purchaser, a completed noise datasheet;

i) a program for scheduling the work after receipt of an order;

1) pipes and fittings;

3) extended surfaces on tubes;

4) castings, steel fabrication;

5) ladders and platforms;

12) system skids;

13) other auxiliary equipment as applicable.