File-Chemical Inject
File-Chemical Inject
File-Chemical Inject
SABP-A-015
Chemical Injection Systems
Document Responsibility: Corrosion Control Standards Committee
Contents
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SAES-A-133
SAES-A-134
SAEP-43
3.1 3.1 Deletion Deleted the following
references:
SAES-L-133
SAES-J-400
SAER-2365
SAER-5941
3.1 3.1 Modification Corrected the title of the
following references:
SAES-A-205
SAES-D-109
SAES-G-006
SAES-L-132
32-SAMSS030
32-SAMSS-038
DB-950175-001
DB-950176-001
DB-950177-001
DB-950178-001
DB-950179-001
3.2 3.2 Addition Added the following reference:
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API 570
NACE MR0103/ISO17945
NACE MR0175/ISO 15156
- 4.1 New New section with Acronyms
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The intent of this best practice is to provide guidelines for the detailed design, materials
selection, quality assurance, operations and inspection of chemical injection systems.
The content is based on established industry guidelines and field experience with their
use in Saudi Aramco facilities.
This Best Practice was developed to assist with improving and maintaining the
mechanical integrity of Saudi Aramco upstream and downstream facilities through the
use of the chemical injection systems.
This Best Practice covers chemical injection systems in all refining units, including wash
water and chloride injection in reformer units. All upstream oil & gas processing
facilities, transmission and producing pipelines and steam generators chemical injection
systems have been also covered. The chemical injection system for sea water
application is not covered in this document.
References
All referenced specifications, standards, codes, drawings, and similar material are
considered part of this Best Practice to the extent specified applying latest revisions
unless stated otherwise.
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API 570 Piping Inspection Code: In-Service Inspection, Rating, Repair, and
Alteration of Piping Systems
API RP 932-B Design, Materials, Fabrication, Operation, and Inspection
Guidelines for Corrosion Control in Hydroprocessing Reactor
Effluent Air Cooler (REAC) Systems
American Society of Mechanical Engineers
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Acronyms
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Definitions
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Stress Corrosion Cracking (SCC): SCC is the cracking induced from the combined
influence of tensile stress and a corrosive environment.
Chemicals play an important role in the enhancement of oil and gas production and
processing. They control corrosion, prevent organic and inorganic deposits, aid in
phase separation, control microbial problems, control pH, scavenge oxygen and
neutralize chlorides. Chemical injection is considered one of several corrosion
mitigation methods such as coating, material selection, cathodic protection, process
control, use of CRAs, etc.
Chemicals can be delivered to the process through a variety of methods. There are
three typical injection system configurations used in hydrocarbon production and
processing:
• Retrievable (high pressure)
• Retractable (low pressure)
• Fixed (high or low pressure)
The retrievable system allows operators inject chemicals, retrieve, inspect and maintain
the equipment while the system is fully operating. These systems are used in the oil
and gas production industry; from the wellhead through the GOSP, and pipelines.
Figure 1 shows a typical retrievable chemical injection system. The system assembly
consists of a high-pressure access fitting, a solid plug, an injection nut, and an injection
tube (quill, cross head or perpendicular spray nozzle). Also see DA-950035-001.
Commentary Note:
There are also systems available that injects through a hollow plug, incorporating a small
non-return valve in the plug.
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The retractable type injection system (see Figure 2) is commonly used in refining
operations, that operate at low temperature (< 100°C/212°F) and pressure (< 1034
kPag/150 psig).
A retractable quill style injector, which has a packing gland design, offers the ability to
remove and service the injector system during normal operations. This design can be
manually retracted from lines or other equipment operating at low pressure.
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The following factors need to be considered as these can have a significant impact on
the safety, maintenance, operation, and service life of the chemical injection system:
• Chemical solution being injected
• Concentration of the chemical being injected and the mixed chemical/process
stream (for example; concentrated sulfuric acid injected into a RO water stream)
• Flow rate of the chemical injected and the process stream
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General
Vent
Relief Valve
Chemical
Storage Tank
Level Pressure
Meter Calibration Gauge Damper
Over-flow Tube
Truck
Conection
To
Injection
Point
Y-Strainer
Positive Displacement Pump Flow Switch Flow Meter
The chemical injection system is designed to accommodate the chemical types and
volumes that are considered necessary for efficient operation throughout the facility
lifetime. All systems are appropriately sized to handle ‘worse-case’ scenarios. Unless
otherwise specified, equipment will normally be installed outdoors in a relative humidity
from zero to 100% (condensing) and exposed to heat and sand. Site specific
meteorological and seismic data as specified in SAES-A-112 are used for equipment
design.
Commentary Note:
In Saudi Arabia, metal temperatures can reach 70°C when exposed to direct solar
radiation.
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Other products which do not meet these guidelines, such as strong acids, or inhibitors
injected in refinery process systems, etc., should be assessed on a case by case basis,
using the minimum mandatory requirements of SAES-L-132. Specific materials for a
few applications are detailed in this document. Non-metallic materials are generally not
used for chemical injection and may only be used as indicated in this document or
permitted in SAES-L-132.
When handling chemical solutions where the solvent is water or when injecting water,
dissimilar metal flanged joints should use insulation kits as mandated by SAES-A-133.
The chemical storage tanks should be sufficiently sized so that re-filling is not required
every day. The size of chemical storage tank depends on their exact application.
Chemical storage tanks in offshore upstream operations are normally sized for 3
months use. Chemical storage tanks in refineries are usually sized to provide at least
one month’s capacity. Some applications, such as caustic (NaOH) in a refinery, may
use local unit tanks that are made up on a batch basis from a bulk supply. Such local
unit tanks should have a minimum of one day’s capacity.
A chemical tank should be equipped with a fill nozzle, vent, discharge, level instrument
and drain. The chemical storage tank level should be monitored. Chemical storage
tanks should be flushed and cleaned when replacing chemical type.
Chemical tanks must be properly labeled as to the contents of the tank and its hazards.
Tanker connection should be accessible by road and must be clearly identified with
connected tank number and product. Unloading connections shall be sealed, in order to
prevent cross-contaminating chemical products, with blind flanges or if fitted with quick
connect systems with plugs or caps. Chemical tanks must be electrically grounded
similar to any other tanks in the plant. Also, the chemical tanker must be connected to
the ground system before starting chemical filling to the tank.
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A containment concrete slab and curb should be constructed around the tank to contain
its contents in the event of a spill or tank rupture. This concrete slab and curb must be
sloped toward a drainage system. It should be noted that, any new chemicals should
be included in the plants spill prevention controls. Spacing and diking of tanks shall be
in accordance with SAES-B-005. Concrete foundations for tanks shall be in accordance
with SAES-Q-005.
Standard storage units or tanks provided by chemical vendors are sometimes used for
some applications including temporary chemical applications or where there is limited
space for the construction a storage tank. These containers are usually made of
austenitic stainless steel type 316L (UNS S31063). For products that are corrosive to
stainless steel, polyethylene and other non-metallic materials are used.
Vendor storage systems usually contain a shuttle tank and a base tank (see Figure 5).
The shuttle tank is used for the transportation of the product. The two tanks are
connected via the filling hose. Transfer of the product from the shuttle tank is done
under gravity. The supplier fills a shuttle tank with a product and delivers the filled tank
to the facility. When the shuttle tank empties it is disconnected and returned to the
product supplier for reuse. The supplier replaces the empty tank rather than refilling it
on-site.
The preferred use of these tanks is to stack one on top of another and drain the shuttle
tank into the permanent site tank.
Some chemical tanks require nitrogen purge to exclude oxygen from the feed. Some
tanks require mixers, caustic tanks in particular. These mixers should be nitrogen or
mechanical. No air blowing is allowed for mixing purpose.
Special materials are required for special chemicals such as caustic and sulfuric acid.
The materials of construction should be as mandated by SAES-L-132.
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Non-metallic tanks have been used for more than 25 years successfully in the offshore
Berri field.
Pumps
Positive displacement pumps are frequently used for injection of chemicals into a
pressurized system. The positive displacement pump must be a metering type with
stroke adjustment to vary the chemical injection rate. It is important to select a pump
from Saudi Aramco approved manufacturers that meet the required flow rate and
pressure.
The chemical injection pump pressure needs only to be slightly higher than the internal
process stream pressure. The positive displacement pump must be capable of
generating sufficient injection line pressure to overcome injection line losses, the
process line operating pressure and thus create the required pressure differential
across the injection tube.
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Most process piping failures that are related to chemical injection points have occurred
immediately downstream of the injection quill. Many of these failures have been
attributed to localized corrosion attack of the concentrated product, which corroded the
process line pipe wall. Consequently, the use of internal injection tubes, such as quills
or atomizing nozzles, which direct the product into the process fluids, are required.
The design of an injection quill is very critical. The quill should be designed
efficiently to disperse injected chemicals into a process stream without
allowing the injected chemicals to concentrate against the pipe interior walls
and without clogging the injection quill opening.
The injection quill must be sized to inject the desired amount of chemical, and
should be capable of effectively and intimately mixing the chemical with the
process stream. Injection quills should be installed per approved design
drawings and an inspector has to verify all injection quill insertion dimensions
according to 01-SAIP-004 prior to the installation.
The quill design should be evaluated for possible stress, fatigue problems and
flow induced vibration. For new projects or installations, stress calculations
must be performed to determine the optimum injection quill insertion length.
For any replacement quills, stress calculations must also be performed and
provided. Process stream flow rate fluctuations, flow regimes, fluid viscosity
and quill natural frequencies are essential variables affecting injection quill
design.
Open-end injection quills shall have a bevel cut angle at 45° minimum and
60° maximum. Angles less than 45° would limit the influence of the scarf cut.
The quill must include a slot through a wall of the quill tip. The slot shall not
be longer than the length of the bevel. The slot is rectangular and is opposed
to the angled end.
Quills with an angled face utilizes the turbulence created by its design, in
conjunction with the natural turbulence within the pipe, to accomplish
distribution of the injected chemical into the process stream.
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For liquid streams, the quill should be installed in the pipe so that the angled
face of the quill faces downstream of the fluid flow direction (Figure 6). For
mixed and vapor phase streams, the angled face of the quill should face the
fluid upstream as shown in Figure 7.
Caustic injection quills (Figure 8) shall not be fabricated using pipe with a
welded end plate. Caustic injection quills shall therefore be fabricated from
solid alloy bar as follows:
• Operating temperature ≤ 204°C (400°F): Alloy 400 (UNS N04400)
• Operating temperature > 204°C (400°F): Alloy 600 (UNS N06600)
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Fabricating the caustic injection quill by boring a solid alloy bar is considered
as unlisted components in ASME B31.3. The ASME B31.3 Code defines
unlisted components as components not in Tables 326.1, A326.1, or K326.1
of the code.
The processes used to fabricate the caustic injection quill must be reviewed
for Code compliance. Some fabrication processes can cause gross or local
wall thinning. The absolute first stage in the process of fabricating the caustic
injection quill is to perform PMI on the bar material to assure that the material
is indeed the intended alloy. Do not rely on paperwork or bar stamping. The
metallurgical condition of the bar should be “annealed”. The machining
should be done in more than one pass. First a rough cut is required followed
by fine cutting. The objective is to avoid work hardening the surface. All
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The pressure design of the fabricated caustic injection quill shall be based on
calculations consistent with the design criteria of ASME B31.3. These
calculations shall be substantiated by one or more of the means stated below
(paragraph 304.7.2 of ASME B31.3) considering applicable dynamic, thermal,
and cyclic effects in paragraphs 301.4 through 301.10 of ASME B31.3, as
well as thermal shock.
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A calibration tube is typically a clear tube with markings in milliliters, gallons/hour (GPH)
or gallons/day (GPD) as appropriate and used with a stop watch to measure the flow
rate. The tube should be placed on the suction side of the injection pump with the
necessary valves and fittings so the injection rate can be checked any time by the
operator. Main line chemical feed and calibration tube shut off valve shall be ¼ turn ball
valves and shall be positioned so that the operator can easily and simultaneously
operate both valves during calibration. Calibration tubes should be vented back to the
storage tank above the high-high liquid level.
Injection Line
Injection lines should be sized to allow for the efficient transfer of chemical and stay
within the working pressure of the material. All connections from the chemical pump to
the point of injection shall be hard piped. Flexible tubing in certain section can only be
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Check Valve
Check valves must be installed on all chemical lines at the inlet line to the injector to
prevent the process fluid from pushing back into the chemical injection line. Some of
the line or fittings have built-in internal check valve. It is recommended to install external
ones. The internal check valves are not reliable in case of internal corrosion that will
damage the internal threads causing the check valves to be disoriented and becoming
useless. Also, the long inspection intervals of these fittings, once a year during the
plant PM shutdown, will make them un-reliable.
Filter
Filters/Y-strainers must be placed between the chemical supply and the injection pump.
The size and type of the filter element will depend on the rate and type of fluid that is to
be pumped. Two separate filters with individual isolation valves shall be provided where
chemical injection cannot be stopped for process reasons (for example: injection of
demulsifiers).
Miscellaneous
Most of the chemical injection lines are small in size (less than 1-inch diameter) and are
therefore not rigid. These injection lines can easily vibrate if not properly supported.
Such continuous vibration can result in fatigue failures. As a result, adequate support to
these chemical lines must be provided.
Each injection point should be installed with an isolation valve in case any repairs are of
the chemical feed system are required. For retractable systems, a vent valve must be
installed to release pressure and drain any process fluid/gas that accumulates after the
quill is retracted from the process and the injection valve is closed.
A pressure relief valve must be installed on the pump discharge to vent fluid back into
the chemical tank or pump suction line if pressure builds up.
The actual pump internal relief valve setting shall be between 110% and 120% of the
rated discharge pressure.
A sight flow indicator is recommended to be provided close to the injection point location
as visual indication of chemical flow.
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As per SAES-L-110, Section 9, seal welding of threaded joints is required when deemed
necessary by the Operating Organization for those locations and services where an
uncontrolled leakage would result in serious consequences for the operation or safety of
plant and personnel. Seal welding of all threaded joints up to the first block valve is
required in the following services and applications:
• All hydrocarbons
• Boiler feed water, condensate, and steam systems utilizing ASME Class 300 and
higher flange ratings
• Toxic materials such as chlorine, phenol, hydrogen sulfide, etc.
• Corrosive materials such as acid, caustic, etc.
• Oilfield chemicals (e.g., corrosion inhibitors, Demulsifiers, electrolytes, etc.)
• Piping which is subject to vibration, whether continuous or intermittent
As per SAES-A-206, Section 5 and 00-SAIP-07, PMI testing shall be performed at a
point in time that ensures proper alloy materials have been used in the fabrication of an
identifiable assembly. Usually, this is done after fabrication and immediately prior to
fabrication to ensure completes testing of the injection system components before their
installation in the field.
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The injection point should be installed in a location which can be accessed. Adequate
clearance should be available for insertion and removal of the quill.
The effectiveness of the chemical injection is influenced by the location of the injection
point. The quill should be installed in a location where the flow rate will promote
effective distribution of the chemical. The turbulent flow at the injection point should
cause mixing of the injected chemical with the process stream. The relative viscosity of
the injected chemical and the process stream play a major role in mixing.
The injection tube tip should be inserted within the center 1/3 of the pipe (Figure 10).
This is where the highest fluid velocity normally is, and will avoid prevent concentration
of the chemical at the pipe wall. It is imperative that any injected chemical is not
directed at the equipment or pipe wall where it could cause localized corrosion damage.
For nominal pipe sizes of 36 inches and greater, the inserted quill length shall provide a
tip location not greater than 35% of the nominal diameter measured from the outside
wall of the pipe while the minimum insertion must be no less than 6 inches.
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The quill opening must be aligned parallel to the process flow with the correct opening
orientation, as illustrated in the previous section. Therefore, the orientation of the quill
must be marked to insure proper positioning of the quill opening once the injection tube
assembly is installed in the process pipe.
One of the recommended field practices for high pressure injection systems, is to
permanently mark, on the solid plug hex nut, the long side of the quill with a straight
line. This convention should be maintained, if possible, whenever the quill is reinstalled.
The solid plug should not be loosened in order to achieve orientation, as this may affect
the plug seal in the access fitting. This shall be part of an installation checklist signed
off by the installer and assigned inspector.
Monitoring and inspection are key activities in maintaining chemical injection system
integrity. Chemical injection systems must be inspected regularly, including the
injection point itself, downstream and upstream piping and equipment that may have
been affected.
The need for more detailed inspection requirements for chemical injection system was
formally addressed industry-wide with the publication of API 570. Additional inspection
requirements can be found in 01-SAIP-04 “Injection Point Inspection Program”. This
Saudi Aramco inspection procedure provides guidelines for the identification, tracking
and monitoring of chemical injection points.
Management of Change
The Management of Change (MOC) process should be used to identify changes which
could impact the inspection plan for a particular injection point circuit. Below are some
examples of work/changes requiring MOC approval:
• Use of different chemicals
• Change of chemical manufacturer
• Change in process conditions
• Change of materials of construction
• Changing the location of a chemical injection point
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The proper assembly and care of a chemical injection system is extremely important.
Establishing and following a thorough maintenance routine will aid in preventing any
problems. To ensure maximum performance, periodic checks and cleaning are
necessary for the injection quill. This cleaning practice can be done during the plant
shutdown.
All tubing connections, fittings, tanks, and pumps should be checked by the plant
operators on a daily basis. The injection fittings must be examined regularly for leaks
and thread damage. Injection fittings should be thoroughly cleaned at least once a
year. Installed filters should be disassembled, cleaned, and inspected on a regular
basis for contamination and damage. The frequency of inspection is dependent upon
the fluid injection rates; the higher the rates, the shorter the time between inspections.
Filter elements should be replaced if there are any signs of plugging or contamination.
The filter element can be flushed from the inside out with solvent. If any significant
debris is noted at any one time, the source must be identified and eliminated. The
check valve should be checked regularly to confirm that its seat is clean and seated
correctly to stop any back flow.
If a chemical injection system appears to be plugged or the flow restricted, stop injecting
immediately. Pull and inspect the filters for debris. If the injection system does not
respond to this treatment, stop pumping. Troubleshoot the chemical injection system to
identify the location of plugging and clean it. Continued pumping may only increase the
severity of the problem and possibly damage the system.
If any piping or equipment shuts down or is taken down for inspection or maintenance,
the chemical injection system related to this piping or equipment shall be stopped.
This will avoid concentration of the injected chemical at the injection site which can lead
to corrosion for the pumps, valves and piping system.
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The injection point isolation valve must not be closed without stopping the pumps,
because injection against a closed injection location valve will cause continual operation
of the PZV.
Records of maintenance activities, repairs and downtime for the chemical injection
system should be documented to develop appropriate maintenance strategies.
Appendix A contains a sample form that can be used for documenting plant injection
point details. This form should be carefully completed with as much detailed information
as possible for each injection point in the plant. It will help concerned
engineers/inspectors to make sure that all injection points are included in the inspection
program. This form will assist plant inspector to select the proper inspection techniques
and to optimize the inspection interval.
For caustic, neutralizing and filming amine injection points, all PMI performed must be
documented and logged in inspection files. Proved quill tip location and orientation after
installation and before startup by radiography shall be also retained by the plant
inspection. It is recommended that a digital photograph before installation to be taken
for the quill tube inserted in the pipe so that the conditions and details of the quill can be
noted. This photograph should be documented in inspection files.
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The purpose of warnings and cautions highlighted below is to call the operator’s
attention to possible danger of injury to personnel and/or damage to equipment, and
deserve careful attention and understanding. Safety precautions must be established
throughout any activities related to the chemical injection system operations including,
but not limited to the following:
• Safe operation for the retrieval equipment requires a minimum of two (2) trained
operators.
• The retrieval equipment shall not be used unless the crew performing the work
has been trained in its safe operation.
• All plant safety requirements and environmental regulations shall be followed.
• The media type, its pressure and temperature for the attended job shall be
identified before commencing the job.
• All the required personal protective equipment shall be provided and used when
checking the injector, i.e. hard hat, safety glasses, protective clothing, face
shield, safety gloves, breathing apparatus, etc.
• Any actions which could vary system pressure such as surges caused by
opening and closing of valves and chokes should be delayed until completion of
the attended job related to the chemical injection system operations.
• Enough clearance for safe operation around the attended location should be
established.
• Wind direction prior to starting operations involving hazardous products should
be noticed.
• Up-to-date CHBs shall be posted near all chemical storage tanks and unloading
sites.
• Ensure safe release of chemical to the environment by proper installation of
equipment, provision of ventilation and personnel protection.
• Every chemical injection skid shall be equipped with eye washes and showers
side to be used in case of any emergency situation.
• Waste chemical shall be disposed in a safe place.
• For the retractable injector, be careful when breaking connections. Release the
pressure on the chemical line using the drain valve on the pump discharge. Be
sure to close the isolating valve on the process before inspecting the retractable
injector. Break the connection between the retractable injector and the isolating
valve slowly and carefully to release any pressure. Verify that the valve is
completely shut and holding before removing the retractable injector. Never
operate the retractable injector without the external support frame.
• The operator should always position himself to the side when working on the
injector location.
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Many different types of process additives are used to maintain reliability and optimal
performance of refinery operations. The types of injection chemicals used in refineries
are as varied as the intent and purpose of the programs they service. An additive can
be either a commodity chemical such as acid, caustic, methanol; or a proprietary
chemical such as neutralizing amine, filming amine, antifoulant and chloride. NACE
Publication 34101 contains general guidelines for refinery chemical injection and mixing
points and NACE Publication 34109 contains specific guidelines for chemical treatment
in Crude Distillation Units (CDUs).
The additive can be as simple as a water stream injected to dissolve salt deposits or to
dilute corrosive process components. Wash water requirements in SAES-A-133 and
DB-950176-001 shall be followed. Some of the major types of additives used in
refineries are:
Caustic (NaOH) injection is used to reduce crude column overhead acid corrosion,
caused by hydrogen chloride (HCl). Caustic is injected at different locations in a Crude
Distillation Unit (CDU).
Caustic is sometimes injected upstream of the desalters to control desalting pH, but this
is seldom used. pH values above 7.0 leads to tighter emulsions and poor performance
of the desalters while pH values below 7.0 is better for the desalter performance.
For CDU overhead corrosion control, caustic is injected at a location between the
desalter and the fired heaters. The location of this injection point varies from refinery to
refinery in Saudi Aramco’s operations. Injection immediately downstream of the
desalters, referred to as the “Cold Location” is preferred. However, some refineries
prefer to inject caustic in a “Hot Location” immediately upstream, of the CDU charge
heaters. Caustic injection in the Hot Location is considered higher risk than the Cold
Location.
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Injection Locations
Refer to SABP-A-016
The most important consideration in the design of the crude bypass stream is
to establish a controlled flow which will maintain an injection velocity of 9.1
m/s (30 ft/s) into the main crude stream. It is assumed that the velocity of the
main crude stream at the point of injection will normally be greater than 2.0
m/s (7 ft/s).
In order to meet this objective, while at the same time limiting the bypassed
crude rate to less than 1% of the maximum expected crude rate, three
differently sized injection sections, as shown in Table 1, are recommended to
cover the range of crude unit capacities.
The detailed design of the caustic injection system is shown in the Library
Drawing DB-950177-001. Table 2 summarizes the caustic injection
requirements. Each refinery must have updated as-built quill detailed design
drawings which also specify the quill materials of construction.
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Neutralizing amine is introduced into the crude unit overhead lines from the atmospheric
columns and vacuum columns to neutralize the acids that cause very low pH and high
corrosion rates at the water dew point. The objective of injecting neutralizing amine is
to control the pH in the overhead receiver water at a pH of 5.5 to 6.5 which is the range
commonly used in the industry. However, some companies have adopted different
ranges. Other operating companies use a target range of 7.5-8.0. This higher pH is
achievable in systems using ammonia for neutralization but is not cost effective in Saudi
Aramco systems where a neutralizing amine is used.
Design Basis
This method will fully disperse the neutralizer into the vapor stream and will
prevent neat chemical injection which could lead to under-deposit and severe
localized corrosion.
In order to have a good neutralizing amine injection the following items shall
be consider in the system design:
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Injection Locations
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Filming amine is added to provide a protective film, or barrier, between the metal
surface and corrosive liquids.
Injection rates are typically set to add the chemical at 3 - 5 ppm based on total overhead
naphtha rate. Filming amine should normally not be injected in concentrated form. The
product is injected into the overhead line through a quill with a naphtha slipstream with a
dilution between 50 and 100 naphtha to 1 inhibitor. Typically, naphtha dilution is
provided to help the dispersion, at the injection point, and to dilute the concentrated
filming amine that may be corrosive to injection equipment.
Design Basis
The filming amine shall be injected through an injection quill with naphtha to
distribute the filming chemical. This method will fully disperse the filming
amine into the overhead stream and will prevent neat chemical injection
which can be corrosive at elevated temperature.
In order to have a good filming amine injection the following items shall be
consider in the system design:
• All process-wetted parts, including the injector pipe with a quill tip or
nozzle, are constructed of Alloy C2000 (UNS N06200), Alloy B-2 (UNS
N10665) or Alloy 625 (UNS N06625).
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Injection Locations
For crude distillation units (CDU/VDU), the filming amine is typically injected
immediately downstream of the neutralizer separated by minimum space of
5D if possible. However, Ras Tanura Refinery injects filming amine upstream
of fin fans.
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The detailed design of filming amine injection system is shown in the Library
Drawing DB-950179-001. Table 4 summarizes the filming amine injection
requirements; refer to SABP-A-025, Appendix I, for Vacuum Unit locations.
Refinery must have current as-built quill detailed design drawings which also
specify the quill materials of construction. These drawings should be up-to-
date and signed-off.
Table 4: Corrosion Inhibitor Injection Requirements for Crude Atmospheric Tower Overhead
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Water washing has been practiced in many refinery process units as a means of
preventing formation or removing fouling salt deposits and to dilute corrosives, often in
column overhead systems, hydrotreater reactor effluent systems, and in the overhead of
some fractionators. For hydroprocessing units, refer to API RP 932-B and SABP-Z-031.
Most water washes have been continuous. Intermittent washing has been
used in some applications for periodic removal of salt deposits. Low water
wash rates can be more harmful than beneficial. The water rate must be high
enough so that the bulk of the water does not flash at system conditions when
injected. Because many of the salt deposits encountered in refining
processes are hygroscopic, inadequate water washing can lead to severe
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Injection Locations
Many refinery process units have used water wash as a corrosion control
method. The following are list of the water wash injection locations which are:
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The detailed design of the water wash injection system is shown in the Library
Drawing DB-950176-001. Table 5 summarizes the water wash injection
requirements. Refinery must have current as-built quill detailed design
drawings which also specify the quill materials of construction. These
drawings should be up-to-date and signed-off.
Table 5: Water Wash Injection Requirements for Crude Atmospheric Tower Overhead
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Older reformer units use fixed bed reactors in series. Typically, four reactor beds are
used in a cascade arrangement. These units are referred to as semi-regenerative
catalytic reformers. Removing one bed at a time from service and physically opening
the reactor and removing and replacing the catalyst achieve regeneration of this type of
process.
The chloride content of the catalyst must be kept in the range that is provided by the
catalyst supplier to maintain good catalyst activity and selectivity.
Design Basis
The injection quill and as much of the related piping and valves as possible
have often been fabricated from Alloy 600 (UNS N06600), which has
sufficient nickel content to make it immune to chloride stress corrosion
cracking.
Injection locations
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Fouling deposits can degrade the operation of refinery process units in several ways:
restricting fluid flow, reducing heat transfer rates, shortening service life, and
compromising product quality. While fouling can be found throughout the refinery, the
most common problem area includes Condensate Fractionation Unit.
Fouling deposits can consist of inorganic materials, such as iron sulfide corrosion by-
products, and organic materials, such as agglomerated asphaltenes, thermally
degraded polymer, and coke. Deposits often contain a complex mixture of organic and
inorganic materials.
An antifoulant is a chemical additive which may be injected into a process stream at low
concentration to prevent the buildup of deposits on downstream tube/shell exchangers.
Because of the variety of complex mechanisms which contribute to an overall fouling
problem, no single balanced formulation is effective for all fouling cases. Consequently,
each fouling problem is highly individual and dependent on many variables such as
experience on similar operating units, unit history, stream characterization, deposit
analysis, and/or laboratory screening. The use of antifoulants is often a matter of
experimentation to establish which compound is most effective. Then, the success of
an antifoulant application depends largely upon properly selecting the right antifoulant
for the fouling problem at hand and determining what dosage level is required to
maintain fouling control.
Design Basis
The injection quill should be made from austenitic stainless steel type 316L
(UNS S31603) pipe.
Injection Locations
The detailed design of the antifoulant injection system is shown in the Library
Drawing DB-950175-001. Table 7 summarizes the antifoulant injection
requirements. Refinery must have current as-built quill detailed design
drawings which also specify the quill materials of construction. These
drawings should be up-to-date and signed-off.
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Design Basis
Standard two-inch high pressure access fittings and injection quills are commonly used
in GOSPs, oil & gas processing facility and gas plants for injecting typical oilfield
treatment chemicals. High pressure access fittings are designed to permit safe,
relatively easy insertion and retrieval of injection quills as well as other devices (such as
coupons or monitoring equipment) while under full operating pressure.
This type of injection quill can be removed for cleaning while system is under pressure.
The injection components, other than the access fitting body, shall be made from
austenitic stainless steel type of 316L (UNS S31603) or better and shall be suitable for
sour service and meet all sour service requirements of SAES-A-133, NACE
MR0103/ISO 17945 or NACE MR0175/ISO 15156, as applicable.
Access fittings for injection must be installed in straight run pipe. The fitting must not be
installed closer than a minimum of two pipe diameters downstream of a bend, valve or
reducer and there must be a minimum run of 5D of straight pipe downstream of the
fitting before a bend, reducer, etc. When more than one access fitting is installed in one
location, the fittings must be separated by a minimum of 1.0 m (3 ft). In order to operate
the retriever, a minimum of 300 mm (12”) clearance is required around the access fitting
body and a minimum of 2,500 mm (8 ft) above or to the side of the pipe for top and side
mounted fittings.
Check valves are required immediately upstream of the shut-off valve at the fitting. The
shut-off valve should be austenitic stainless steel type 316L (UNS S31603) and after
installation onto the nipple must be seal welded in accordance to Saudi Aramco welding
procedures. Positive shut-off valve required such as gate, needle or ball.
Short nipples and shutoff valves must be rated for sour service and they should be
identifiable (grade and rating) as per SAES-L-105. All valves installation and seal
welding should be as per SAES-L-110, Section 9.
If a chemical injection fitting is not in service, the solid plug, injection nut and quill shall
be extracted, the quill must be removed from the injection nut and a solid stainless steel
pipe plug installed in its place. This prevents service fluid from migrating up the quill
through the hollow injection nut and contacting and possible corroding the threaded
nipple installed in the access fitting body tee. Prior to re-installing the plugged injection
assembly into the access fitting the upper and lower O-rings shall be replaced.
Injection Locations
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The typical design of the chemical injection point is shown in the Library Drawing DA-
950035-001 “2-Inch high Pressure Access System Chemical Injection and Corrosion
Monitoring”. The following Table 8 summarizes the chemical injection requirements in
upstream facilities and Gas Plants.
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Scaling in steam generators is caused by impurities being precipitated out of the water
directly on heat transfer surfaces or by suspended matter in water settling out on the
metal and becoming hard and adherent. Scaling in steam generators will result in
excessive fuel consumption due to loss of heat transfer and may also cause localized
overheating. This can lead to tube failure. The first preventative measure for scaling is
to supply good quality water as make–up feed water.
Feed water also contains dissolved gases such as oxygen or carbon dioxide. These
gases in the presence of water and metal can cause corrosion. Oxygen attack is one of
the most common causes of corrosion inside steam generators. Oxygen attack can
cause damage to economizers, steam drums, mud drums, boiler headers and
condensate piping. A deaerator removes most of the oxygen in feed water; however,
trace amounts are still present and can cause corrosion-related problems. Oxygen
scavengers are added to the feed water, preferably in the deaerator storage section, to
react with the trace amounts of oxygen not removed by the deaerator.
Corrosion can also occur from excessive alkalinity of excessive pH of the boiler water.
This caustic attack is most likely to occur under scale or deposits, where very high local
concentrations of hydroxide can build or in zones where insufficient cooling.
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Design Basis
Chemicals used in steam generator systems are best injected neat, to avoid batch
preparation errors and to minimize the size of the dosing pumps. Most water treatment
vendors supply chemicals in semi-bulk tanks of 1000 liter capacity. The use of semi-
bulk tanks avoids the need for day tanks.
Refer to SABP-A-021 for Desalination Plants, SABP-A-026 for Cooling Water Systems,
SABP-A-028 for Reverse Osmosis Systems, and SABP-A-029 for Boilers.
Injection Locations
Chemical injection system requires continual operator attention to make sure that the
correct dosage rate is being injected in the system. Adjustments to the volume of
chemical injected should be made to maintain the dosage rate set point. The operator
should visually check the condition of the chemical pumps, tanks and piping in a daily
basis. Maintaining the optimum chemical dosage to process streams and monitoring
the effect on corrosion rates are extremely important in corrosion control. Failure to do
so would result in surprises and unplanned equipment failures. Plant operators should
check the chemical injection rates twice per shift.
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Monthly status reports should be issued by the Area Corrosion Engineer and sent to the
Operations Foreman, highlighting the monthly spot check deficiencies noted and the
required course of action. Tracking of chemical consumption and adherence to
established injection targets is an Operations responsibility. Operations staff should
highlight the deficiencies up through their organization on a daily basis. Follow-up visits
by the Corrosion Engineer should be made to observe the implementation of
recommendations. In addition to the periodic reports, more formal chemical injection
system review meetings and audits are recommended to be conducted regularly. The
frequency of review meetings and audits depends on the corrosivity and history of the
plant piping and equipment system, and has to be determined for each specific case
and chemical.
The success of the effective chemical injection program ultimately revolves around the
ability of operations personnel, process and corrosion engineers to interact and
effectively communicating targets, objectives, and problems.
Strict adherence to this procedure allows the plant operations staff to reliably and
accurately optimize the chemical injection rate. This level of chemical dosage control
can significantly reduce the need for maintenance, lower the risk of unexpected failure
and further reduce operation and maintenance costs by assuring adequate dosage of
the chemical is injected in the plant piping and equipment.
The most important aspect of the chemical obviously is its performance and
effectiveness. Therefore, regular corrosion monitoring to obtain trended data are the
only means to ensure that chemical injection is effective. Inspection is also used
periodically to ensure the integrity of plant piping and equipment. The monitoring and
recording of all available parameters, including flow rates, and chemical consumption, is
required to ensure that the chemical treatment program is operated and managed
correctly.
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The aim should be to use data from at least two types of technique to obtain consistent
information; for example, on-line corrosion monitoring, weight loss coupons, and iron
counts. Appropriate sampling equipment location is also crucial for the determination of
the system corrosivity.
Data from the monitoring activities outlined above should be gathered together and
correlated with relevant process data and other information. The trended data should
enable out-of-compliance conditions to be detected and for the appropriate corrective
actions to be taken or for repairs to be completed before the operation or integrity is
compromised. The main goal of overall process system condition monitoring, should be
to detect out of compliance conditions very early after their occurrence and to correct
the condition and return the system to compliance before there would be enough
damage to the system to warrant repair.
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Regular monitoring and adjustments are typically needed to optimize the performance
of the costly chemicals due to operational conditions changes. The chemical
optimization activity concentrates on injecting the correct amount of treatment chemical
into a system or specific piece of equipment under the current process conditions, to
achieve the result anticipated from the application of the chemical. The chemical
requirement is driven by factors such as water cut, water volume, flow regime, and
condition of the equipment. However, the ultimate measure of whether or not enough
chemical is used can only be determined by consideration of other factors such as
corrosion monitoring data and/or the amount of active corrosion detected by the OSI
program, results of inspections during T&Is and process variables changes.
The correlation between the inspection data and the corrosion monitoring data allows
the corrosion monitoring data to be interpreted with better confidence to manage the
chemical injection program in an efficient manner.
Information from corrosion monitoring and inspection activities should be collated and
gathered together to help in the chemical optimization. This information should also
include relevant process conditions and chemical inhibition data. Typically, the data
gathered should include:
• Process conditions, highlighting any changes.
• Visual observations
• Corrosion monitoring data
• Weight loss coupons.
• Electrical Resistance (ER) probes.
• Linear polarization resistance (LPR) probes
• Inspection data covering
• Ultrasonic inspection data (OSI data)
• Radiographic (X-ray) inspection data
• T&Is inspection reports
• Leak History
• Instrument scraping results for pipelines
• Corrosion and failure analysis reports
Not all inspection and monitoring systems are required and/or applicable for any
particular facility and their use will be dependent on the type of corrosion
process/material damage that is anticipated. It is not intended that this Best Practice
document provides a detailed description of the different techniques which can be found
elsewhere.
The usual monitoring tools for chemical optimization are corrosion coupons, Linear
Polarization Resistance (LPR), electrical resistance (ER) probes and iron counts.
Weight loss coupons provide a check on LPR and ER results and identify the onset of
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Lab analysis for the process should be taken periodically to lead for good monitoring
and chemical optimization as well as protection the system.
Chemical injection inhibitors are typically not pure chemicals. Many of the ingredients
that are used for the formulation of these chemicals are side stream products having
some degree of variation from batch to batch. These chemicals undergo a multitude of
laboratory and field tests before they can be injected in the operating units.
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