Sabp A 015 PDF
Sabp A 015 PDF
Sabp A 015 PDF
1 Introduction............................................................................ 2
2 References............................................................................ 3
3 Definitions and Abbreviations................................................ 6
4 Chemical Injection Overview................................................. 7
5 Chemical Injection System Design...................................... 10
6 Chemical Injection Point Position........................................ 22
7 Chemical Injection System Inspection................................ 24
8 Management of Change...................................................... 24
9 Chemical Injection System Maintenance............................ 25
10 Injection Point Documentation............................................ 26
11 Safety.................................................................................. 27
12 Refinery Chemicals and Water Wash Injection................... 28
13 Upstream Facilities and Gas Plants Chemical Injection...... 45
14 Steam Generator Chemical Injection.................................. 49
15 Chemical Dosage Control................................................... 51
16 Chemical Injection Effectiveness........................................ 51
17 Strategies for Chemical Optimization.................................. 53
18 Quality Control of Chemicals............................................... 55
Appendix A.................................................................................. 56
1 Introduction
1.1 Purpose
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.
1.2 Scope
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 stem
generators chemical injection systems have been also covered. The chemical
injection system for sea water application is not covered in this document.
In the event of a conflict between this Best Practice and other Mandatory Saudi
Aramco Engineering Requirement, please contact the Chairman of the Corrosion
Control Standards Committee for resolution.
1.4 Disclaimer
The material in this Best Practice document provides the most correct and
accurate design guidelines available to Saudi Aramco which complies with
international industry practices. This material is being provided for the general
guidance and benefit of the Saudi Aramco engineers and designers. Use of this
Best Practice in designing projects for Saudi Aramco, however, does not relieve
the designer from his responsibility to verify the accuracy of any information
presented or from his contractual liability to provide safe and sound designs that
conform to Mandatory Saudi Aramco Engineering Requirements. Use of the
information or material contained herein is no guarantee that the resulting
product will satisfy the applicable requirements of any project.
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Document Responsibility: Corrosion Control Standards Committee SABP-A-015
Issue Date: 18 November 2015
Next Planned Update: TBD Chemical Injection Systems
2 References
Unless stated otherwise, all Standards, Specifications and Codes referenced in this Best
Practice shall be the latest issued (including revisions, addenda and supplements) and
are considered a part of this Best Practice.
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Document Responsibility: Corrosion Control Standards Committee SABP-A-015
Issue Date: 18 November 2015
Next Planned Update: TBD Chemical Injection Systems
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Document Responsibility: Corrosion Control Standards Committee SABP-A-015
Issue Date: 18 November 2015
Next Planned Update: TBD Chemical Injection Systems
NACE International
NACE MR0103 Materials Resistant to Sulfide Stress Cracking in
Corrosive Refinery Environments
NACE MR0175/ISO 15156 Petroleum and Natural Gas Industries-
Materials for Use in H2S-Containing
Environments in Oil and Gas Production
NACE Report 34101 Refinery Injection and Process Mixing Points
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Document Responsibility: Corrosion Control Standards Committee SABP-A-015
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Document Responsibility: Corrosion Control Standards Committee SABP-A-015
Issue Date: 18 November 2015
Next Planned Update: TBD Chemical Injection Systems
Stress Corrosion Cracking: (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.
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Chemicals can be applied through a variety of mechanisms. There are three typical
configurations of injection systems used in hydrocarbon production and processing:
retrievable (high pressure), retractable (low pressure) and fixed (high or low pressure).
The retrievable system allows operators to undertake injection, retrieve, inspect and
maintain equipment while the system is under full operating conditions. The oil and gas
production industry from the wellhead through the GOSP generally employs retrievable
injection systems (Figure 1) that operate with high pressure access fittings. The unit
assembly consists of an access fitting, a solid plug, an injection nut, and an injection
tube (quill, cross head or perpendicular spray nozzle).
The retractable type injection system (Figure 2) is commonly used in the refining
operations. 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 fixed assembly (Figure 3) is recommended for use in a by-pass loop which can be
isolated, or in systems having frequent and regular shut-down, since system
depressurization is required during insertion and removal. The unit is ideally suited for
use in high pressure and/or hazardous applications where threaded fittings are not
recommended to avoid leakage. Process shutdown or process isolation is required for
installation and inspection. The unit assembly consists of a flange and an insertion rod
with an injection quill.
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* While fixed systems could be employed in a wide variety of situations, their limited flexibility with
regard to serviceability and maintenance typically restricts their application to more extreme or
hazardous services.
The following factors can have significant impact on the safety, maintenance, operation,
and service life of the chemical injection system:
Chemical solution being injected
Concentration (both of the chemical being injected and the mixed chemical/process
stream, i.e., concentrated sulfuric acid injection into an RO water stream)
Flow rates (both stream receiving the injection and the product injected)
Viscosity
Chemical hazard
Materials of construction
The chemical injection system must be well designed to accommodate the chemical
types and volumes that are considered necessary for efficient operation throughout the
project lifetime. All systems should be appropriately sized to handle the worse-case
scenarios. Unless otherwise specified, equipment will 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 shall be used for
equipment design.
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Commentary Note:
Metal temperatures can reach 70C when exposed to direct solar radiation.
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
5.1 Materials
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When handling chemical solutions where the solvent is water or when injecting
water streams, dissimilar metal flanged joints shall use insulation kits.
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 months 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 days capacity.
The chemical tank shall be equipped with a fill nozzle, vent, discharge, level
instrument and drain. The chemical storage tank level should be monitored.
Tanks shall be reinforced to withstand all forces when full of liquid. 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, i.e., Kamlock, 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.
CHB (it is also known as MSDS) shall be located near the unloading
connections, in enclosures protected from direct sun, wind and rain. In general,
CHBs must be readily available to the workers who are exposed to the chemical
product.
Containment concrete slab and curb must 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.
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Document Responsibility: Corrosion Control Standards Committee SABP-A-015
Issue Date: 18 November 2015
Next Planned Update: TBD Chemical Injection Systems
Chemical tanks manufacturer shall be selected from Saudi Aramco approved RVL
list. Skid-mounted injection systems shall be designed as per 32-SAMSS-038.
These storage systems usually contain a shuttle tank and a base tank (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 automatically under the influence of 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 mode for these tanks location is to stack one on top of another
and drain the new one shuttle tank into the permanent site tank base 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 per SAES-L-132.
Non-metallic tanks have been used for more than 25 years successfully in the
offshore Berri field. For new applications, seek the approval of CSD/OCSD/
Materials Engineering & Corrosion Operation Support Group.
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Document Responsibility: Corrosion Control Standards Committee SABP-A-015
Issue Date: 18 November 2015
Next Planned Update: TBD Chemical Injection Systems
5.3 Pump
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 needs only to be
slightly higher than the internal process stream pressure. So, 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.
5.4 Quill
Most of the failures that is related to the injection point have occurred
immediately downstream of the injection quill. Such failures have been
attributed to general corrosion attack of the concentrated product, which
attacked the pipe wall prior to the product being diluted by the produced fluids.
Consequently, the use of internal injection tubes, as quills, atomizing nozzles,
etc., which direct the product into the process fluids, is required.
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The quill design should be evaluated for possible stress, fatigue problems
and flow induced vibration. For new projects, stress calculations must
be performed and provided by the engineering contractor to determine
the optimum injection quill insertion length. These calculations should
be reviewed and approved by CSD. For any replacement quills, stress
calculations must also be performed and provided. Process stream flow
rate fluctuations, flow regimes, fluid viscosity and quill natural
frequency are essential variables affecting injection quill design.
Natural frequency and wake frequency calculations shall be performed
on each quill that will be installed in the field. The purpose of these
calculations is to prevent the quill from entering a resonant vibration in
which fatigue failure can occur. The wake frequency should be less than
80% of the quill's natural frequency to guarantee no resonant harmonic
vibration. This can be determined by applying the thermowell
calculations in SAES-J-400, Paragraph 5.3.
The style of the injection quill with open end shall has a bevel cut angle
with 45 as a minimum and 60 as a 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.
The quill with 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.
The disadvantage of the quill with angled open end is that at low process
stream flow rates there tends to be a concentration of the injected
chemical at the pipe wall surface below the injection point.
For liquid-phase stream, the quill should be installed in the pipe so that
the angled face of the quill faces the fluid downstream (Figure 6). While
for mixed and vapor phase streams, the angled face of the quill should
face the fluid upstream as shown in Figure 7.
45o-60o
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45o-60o
Caustic Injection Quill (Figure 8) shall not be fabricated using pipe with
welded end plate. Cracking around a circumferential fillet weld can
occur due to the difficulty of getting a sound weld in this restricted area.
So, caustic injection quill must be fabricated from solid Monel bar.
The design, materials, fabrication, examination, and testing of the
fabricated Monel bar shall meet the requirements of ASME B31.3
Process Piping.
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Flow switches can be installed which shut the pump in on low flow and send an
alarm indicating low flow. Flow measurement data and alarms shall be sent to
the DCS.
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
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Document Responsibility: Corrosion Control Standards Committee SABP-A-015
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certain portions can be used only if pressure and temperature limitations are not
exceeded. The distance between the chemical storage tank and the injection
point should be minimized as much as possible. All piping to the injection
pump and from the pump should be free draining towards the pump to avoid any
chemical stagnation.
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.
5.8 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 can not be stopped for process
requirement such as demulsifier.
5.9 Miscellaneous
Most of the chemical injection lines are small in size (less than 1-inch diameter
mostly) and they are not rigid, which can vibrates easily if not properly
supported. This continuous vibration, even if it was minor, would result in
pending fatigue failure in the chemical lines in the long run. As a result,
adequate support to these chemical lines must be provided.
Each injection point shall be installed with an isolation valve in case any repairs
are needed to chemical feed system. For retractable system, 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 process 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.
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Any fittings required for charging the pulsation dampers shall be securely
connected to the discharge piping. Pulsation dampers shall be designed so that
no solids settle in the interior of these devices.
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The injection point is installed through an opening in the wall of the pipeline, refer to
SABP-A-019. It should be installed in location which can be accessed by the Operations.
Adequate clearance shall be available for insertion and removal of the quill.
The effectiveness of the chemical injection is heavily influenced by the location of the
injection point. The quill should be installed in pipe provided, of course, a sufficient flow
rate to promote distribution of the chemical solution. The turbulent flow at the injection
point should cause mixing of the injected chemical with the process stream. The relative
viscosity of injected chemical and the process stream play a major role in mixing.
The injection tube tip shall be inserted within the center 1/3 of the pipe as shown in
Figure 10 that illustrates a side view of the chemical injector installed in a pipeline.
Generally, the most effective position for chemical injection is at the center of the pipe.
Highest fluid velocity is normally at the center of the line, therefore, injection at this
point is supposed to prevent concentration of the chemical at the edge where the
velocity is low due to friction and will ensure efficient distribution of the introduced
chemical. It is imperative that any injected chemical is not directed at the equipment
wall where it could cause local corrosion attack and wall perforation. In large diameter
systems, it may be impossible to find a quill that can be either retractable or retrievable.
Therefore, for nominal line sizes of 36 inches and greater, insertion quill length shall
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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.
If the line pipes are designed for regular scraping operations, protruding injection quill
must be removed before scraping begins. Installation of the protruding chemical
injection tubes in the scrapable line can be avoided by locating the injection point at
other locations such as lateral lines, etc.
Commentary Note:
The most effective position for chemical injection is at the center of the pipe.
Injection Tube
See Note
Proper insertion depth shall be
within center 1/3 of the pipe
The quill opening must be aligned parallel to the process flow with the correct opening
orientation, as illustrated in the previous paragraph, when the injection tube assembly is
placed in the process pipe. 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 system, is to
permanently mark, on the solid plug hex nut, the long side of the quill with a straight
line using a file, small hacksaw cut or waterproof paint marker. 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.
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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 issuance of API RP 570 Piping Inspection
Code Inspection, Repair, Alteration, and Rerating of In-Service Piping Systems.
As stated in API RP 570, injection points are sometimes subject to accelerated or
localized corrosion from normal or abnormal operating conditions. So, API RP 570
recommends more rigorous inspection of injection points due to the potential
susceptibility to accelerated or localized corrosion and these areas need to be inspected
thoroughly on a regular schedule. Moreover, inspection requirements can be found in
01-SAIP-04 Injection Point Inspection Program. This Saudi Aramco inspection
procedure provides guidelines to plant personnel on the injection point's identification,
tracking and monitoring. Refer to 01-SAIP-04 for more details.
8 Management of Change
The Management of Change (MOC) process shall be used to identify changes which
could impact the inspection plan for a particular injection point circuit. Changes to the
composition of the additive, location of the injection, and length of time the additive is
injected can occur frequently. This is especially important when a trial program for an
additive is initiated. Close communication between Operations, Engineering, and
Inspection personnel regarding these types of changes will help prevent the
development of problems due to an oversight in the inspection program. In addition,
the same type of communication on new installations will help improve the
effectiveness and minimize the cost impact of the inspection program by addressing key
issues such as materials selection, inspection access, and potential corrosion problems.
A detailed review of the methodology involved in performing an effective MOC is
beyond the scope of this best practice.
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Process parameters
Materials of construction
Locations of the injection point
Routing chemicals to any sewer
New chemicals being introduced
Existing chemicals being mixed in different ways
Quill replacement in kind to ensure updated construction drawings.
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 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 filled out completely 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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11 Safety
The purpose of warnings and cautions highlighted below is to call the operators
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 emergencies 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.
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The operator should always position himself to the side when working on the
injector location.
The following Sections (12, 13 and 14) describe the details of chemical and water wash
injection requirements in Saudi Aramco facilities with respect to design basis, injection
locations, and material of construction.
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. 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-L-133 shall be followed.
Some of the major types of additives used in refineries are:
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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 2, are
recommended to cover the range of crude unit capacities:
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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.
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Injection rates are typically set to add the filmer 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.
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Table 5 - 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.
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The typical injection point has been located upstream from the
point in the pretreater reactor feed/effluent exchangers where the
temperature allows deposition of ammonium chloride. Water is
injected on a continuous or intermittent basis to remove
accumulations of ammonium chloride salts.
Fluid catalytic cracking unit (FCCU) light ends recovery unit
The detailed design of the water wash injection system is shown in the
Library Drawing # DB-950176. Table 6 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 6 - Water Wash Injection Requirements for Crude Atmospheric Tower Overhead
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Old 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.
To maintain chloride on the catalyst at an optimum level as per catalyst supplier
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The injection quill and as much of the related piping and valves as
possible have often been fabricated from Inconel 600 (UNS N06600),
which has sufficient nickel content to make it immune to chloride
stress corrosion cracking.
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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.
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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
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made out of 316L stainless steel or better and shall be suitable for sour service and
meet the requirement of SAES-L-133 and NACE MR 0103 or NACE MR 0175 /
ISO 15156, as applicable, if injection is required into a sour service process.
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 three (3) feet. In order to operate the retriever, a minimum of twelve
(12) inches clearance is required around the access fitting body and a minimum
of eight (8) feet is required above or to the side of the pipe for top and side
mounted fittings, respectively.
Check valves are required immediately upstream of the shut-off valve at the
fitting. The shut-off valve should be 316L stainless steel 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.
The following is a list of some of the chemical types and their typical injection
locations in upstream facilities and Gas Plants:
Corrosion Inhibitor; refer to SABP-A-018
GOSP production/test header
Trunk lines/flow lines with high water cut
GOSP Wasia wash water line
GOSP LPPT/IPPT/HPPT gas compressor discharge lines
GOSP dry gas line to NGL
GOSP disposal water header
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Biocide Injection
Disposal water line in the 3-Phase Separators
(Plant 429 of Abqaiq Plants)
Demulsifier Injection; refer to SABP-A-018
Production Manifold
GOSP test header
Dehydrator/Desalter inlet
Upstream of 3-Phase Separators (Plant 429 of Abqaiq Plants)
The typical design of the chemical injection point is shown in the Library
Drawing DA-950035 2-Inch high Pressure Access System Chemical Injection
and Corrosion Monitoring. The following Table 9 summarizes the chemical
injection requirements in upstream facilities and Gas Plants.
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Chemical treatment of water inside the steam generators is necessary to prevent scaling
and corrosion in the steam generator and its associated condensate system.
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 makeup 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
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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.
Neutralizing Amines are high pH chemicals that intended to react with trace levels of
carbon dioxide in the condensate system. Being alkaline, neutralizing amines also raise
the pH in the condensate system, which aids in reducing corrosion rates.
Refer to Paragraph 13.1 and Table 9 for complete design requirements of the
steam generator chemical injection point. 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.
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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.
Frequent field visits and spot-checks should be conducted by the Area Corrosion
Engineer to ensure strict adherence to the chemical injection procedures. The intent of
the spot checks is to bring to the attention of the operations organizations the
deficiencies in the chemical dosage rates, chemical injection pumps, type of chemicals
used and similar issues.
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
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LPI
Instrument scraping runs for pipelines
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.
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.
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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
pitting but do not usually give specific information about weld corrosion. The probes
are often installed on a side or top stream of the main production line, for measuring
corrosion rates. LPR measurement can provide a relatively faster response than ER
probes where both of them are used to detect general corrosion. The main difficulty
with this approach is that flow and corrosive conditions in the side or top stream can be
different from those in the main lines. This is particularly true in the case of localized
corrosion. The localized corrosion can be as crevice or pitting caused by water
accumulation at the bottom of the line. In addition, the duration of the chemical
injection optimization study is often not long enough to ensure that stable corrosion
conditions have been established.
Lab analysis for the process should be taken periodically to lead for good monitoring
and chemical optimization as well as protection the system.
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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.
Revision Summary
1 July 2007 New Saudi Aramco Best Practice.
8 February 2015 Minor revision.
The main reason for this minor revision is to include best practice guidelines on Chemical
Injection System Design from cancelled 01-SAMSS-091 Oil Field Chemical Injection Skid
System.
Added reference to mandatory requirement for skid-mounted chemical injection systems
as per 32-SAMSS-038 Manufacture of Skid-Mounted Units.
Added reference to mandatory wash water injection and sour service requirements as per
SAES-L-133 Corrosion Protection Requirements for Pipelines, Piping and Process
Equipment.
Also, added new and updated existing references to Saudi Aramco and International
documents.
Finally, removed trademark and commercial product names from this best practice and
updated Primary Contact information.
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Appendix A
INSPECTION UNIT
Chemical Injection Point Datasheet
(Injection Point Number: Title)
1. Receiving Stream Description
Unit Description
Line Number P & ID No.
Receiving Stream Phase G L G/L Line Size (inch)/Schedule
Line Metallurgy Operating Temperature (F)
Operating Pressure (psi) Corrosion Rate (mpy)
Upstream Equipment Downstream Equipment
Flow Rate (BPD or MMSCF/D) Normal:______________ Min:________________ Max: ____________ Optimum:___________
2. Injection Stream Description
Injection Phase G L G/L Line Size (inch)/Schedule
Line Metallurgy Operating Temperature (F)
Operating Pressure (psi) Corrosion Rate (mpy)
Injection Rate (GPD) Normal:______________ Min:________________ Max: ____________ Optimum:___________
Type of Injection Continuous Intermittent (Frequency:_____________________ )
Back Flow Prevention Check valve Other (Specify:____________________________ )
3. Injection Hardware
Injection Point Type 45o Bevel Quill Spray Nozzle Normal elbow Small Circular Hole
Injection Origin (From) Top Bottom Side of Horizontal Pipe Side of Vertical Pipe
Direction of Injection Injection Face the Fluid Upstream Injection Face the Fluid Downstream
Injection Tube Metallurgy
Flow Measurement System Flow Control System
Name of Vender (if any)
Nearest Pipe Change is Bend Tee Reducer Orifice Other (Specify:_______________ )
Distance
4. Chemical Data
Generic Description
Injection Purpose
Supplier
Product Name
Injection Start Date
(m/d//yr)
5. Injection Point Inspection
Isometric Sketch No.
Inspection Interval
Inspection Technique
Last Inspection Date
Next Inspection Date
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