HAZARD
IDENTIFICATION
Injection Point and Process Mixing Point Hazards
Purpose and Use:
The Process Safety Hazard Identification documents serve to help facilities identify potential risks associated with work
practices, safety practices, process equipment, and technology. Hazard Identification documents are meant to:

Improve process safety awareness with a focus on higher potential risks,

Provide information and ready reference guides for potentially overlooked and not widely known process safety
hazards, and

Share lessons from industry related incidents and near misses.
Scope:
Category: Piping and Other Equipment Associated with Mixing and Injection in Process or Utility Streams, Engineering and
Design Practices, Operating Procedures, Operator Training, Mechanical Integrity Inspection Procedures
A process mixing point is where process streams of differing compositions and/or temperatures join together. An injection point
is a specific type of process mixing point where there can be a significant potential for degradation of equipment integrity due
to operation (or mis-operation) of the injection or change in the process parameters. Some examples of common injection
points are; water injection in overhead systems, antifoam injections, corrosion inhibitor injections, neutralizer injections, and
catalyst injection into reactant streams.
The term ‘injection quill’, as contained in this document, refers to a smaller diameter piece of piping or tubing which is inserted
into a larger diameter pipe for the purposes of injecting a material into the stream flowing through the larger pipe. It also
includes any flow distribution nozzle (or nozzles) which may be attached to the smaller pipe to obtain the required mixing,
contacting, and/or wetting. Injection quills may be retractable or fixed.
Example of An Injection Quill
Process streams are typically combined or joined together at mixing or injection points to:

Mix or blend two separate streams,

Cause a chemical or physical reaction by combining components of two process streams,

Scrub or extract components from one stream by contact with a second stream,

Heat or cool (flash or quench) one process stream by combining with another, and/or

Protect the internal surfaces of equipment handling a process stream.
Examples of Inherent Process Safety Concerns and/or Hazards include:

Loss of primary containment (LOPC) due to internal corrosion and/or erosion resulting from:
A. Potential damage mechanisms not identified
B. Equipment design deficiencies
C. Process changes or creep without management of change (MOC)
D. Operation outside of design window
E. Inadequate mixing point or injection point equipment condition monitoring

Loss of primary containment due to mechanical failure of injection or associated equipment
Note: This hazard identification document is a generic, non-comprehensive synthesis of inherent concerns and / or hazards for
the related topic. It in no way alters any legal requirements. It is not intended to replace sound engineering analysis or
judgment.
HAZ002.000
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HAZARD IDENTIFICATION
Injection Point and Process Mixing Point Hazards
Mixing and injection points are potential locations for damage mechanisms not present in the feed streams or in the final mixed
stream. They may also be susceptible to corrosion, erosion, fatigue, stress corrosion cracking or other damage mechanisms
which may be present before the feed streams are homogenously mixed.
Each of the following hazard situations could lead to possible LOPC with a broad range of consequences depending on the
material released, including injury, toxic exposures, fire/ explosion, damage to equipment and/or the environment and negative
community impacts.
Potential Concerns
1.0
Design Practices
Potential Hazards - UNLESS OTHERWISE SPECIFIED, ALL THE HAZARDS
MENTIONED MAY RESULT IN LOPC
1.1 Process mixing points and injection points that are not identified for further
evaluation.
1.2 Process mixing points and injection points that are not properly evaluated with
such considerations as:
1.2.1 Chemical engineering principles – including the effects of mixing of the
components in the process streams (e.g. mixing tables or incompatibility
tables),
1.2.2 Mechanical engineering principles,
1.2.3 Materials and corrosion engineering principles,
1.2.4 The process objectives for the mixing or injection point.
1.3 The required process conditions (including operating window) that affect the
necessary mixing, contacting, and/or wetting at the mixing point or injection
point and immediately downstream are not correctly evaluated and/or specified
with such considerations as:
1.3.1 The flow rate and flow regime downstream of the mixing or injection
point,
1.3.2 The temperature gradient between two feed streams,
1.3.3 The degree of atomization of the injected stream,
1.3.4 The distribution of the injected stream across the flow area (and, if
applicable, downstream flow splits),
1.3.5 The location of the mixing or injection point relative to upstream and
downstream equipment could be important considerations in this
evaluation and/or specification,
1.3.6 The need for an in-line mixer and the additional damage mechanisms
that it would introduce.
Note: This hazard identification document is a generic, non-comprehensive synthesis of inherent concerns and / or hazards for
the related topic. It in no way alters any legal requirements. It is not intended to replace sound engineering analysis or
judgment.
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HAZARD IDENTIFICATION
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Injection Point and Process Mixing Point Hazards
Section 1.3 Figure
Injected Material
Very High
Corrosion Rates
Could Occur In
These Areas
1.4 Adequate materials of construction that are not specified for the process and
mechanical operating conditions of the mixing point or injection point (e.g.
temperature, vibration, localized corrosion/erosion, etc.) or for the impacted
equipment immediately downstream. This includes piping and equipment
immediately downstream of a bypass around a heat exchanger that may
encounter elevated temperatures during the time in which the exchanger is
partially or fully bypassed. Also, special mechanical design considerations may
be required for mixing streams with a greater than 250⁰F temperature
difference.
Section 1.4 Figure
Cooler Vapor Stream
Saturated with Water
Localized
Corrosion Where
Vapors Condense
Warmer Vapor
Stream with Halides
1.5 Injection quill/s that are not adequately designed, tested and/or installed for the
needed mixing, contacting, and/or wetting.
1.6 Injection point quills and ancillary equipment (e.g., tankage, pumps,
instrumentation, strainers, filters, valves, etc.) that are not designed to meet the
on-stream specifications of the injection point.
1.7 Adequate design provisions for monitoring key variables of the design operating
window that are not made (e.g., accessibility, instrumentation, sampling points).
Note: This hazard identification document is a generic, non-comprehensive synthesis of inherent concerns and / or hazards for
the related topic. It in no way alters any legal requirements. It is not intended to replace sound engineering analysis or
judgment.
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HAZARD IDENTIFICATION
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Injection Point and Process Mixing Point Hazards
1.8 Adequate design provisions for future equipment condition monitoring
inspections (e.g., removable spools, manways, accessibility, etc.) that are not
made.
1.9 Adequate backflow prevention that is not made to keep the main process
stream from backing through an injection point during any type of operation to
which it will be subjected. This could lead to inadvertent mixing or equipment
being subjected to different process conditions than it was designed.
2.0
Unmanaged Process
Changes
3.0
Operation Outside of
Design Window
4.0
Mechanical Failure
2.1 Process changes outside of the design operating window that are not properly
managed with an MOC. This may include unmanaged changes in flowrates,
compositions, pressures and/or temperatures of streams involved in process
mixing or injection points.
2.2 Physical changes made to piping and/or equipment downstream of the mixing
or injection point, or at the mixing or injection point, that are not properly
managed with an MOC. This could lead to mechanical integrity issues.
2.3 Temporary injection points installed for startup or shutdown activities that are
not managed effectively to ensure they are disconnected when they are no
longer required.
3.1 Compositions, flowrates, pressures and/or temperatures of process or chemical
injection streams associated with process mixing points or injection points that
are not routinely monitored and kept within the design operating window.
3.2 Performance monitoring that is not routinely done to ensure that the mixing
point or injection point is achieving any key process objective.
3.3 Injection points that are not commissioned and/or decommissioned at the
proper time during associated equipment startup and shutdown.
4.1 Injection quills and the associated nozzles could corrode, erode or plug causing
a deficiency of mixing, contacting and/or wetting downstream of the injection
point. (Plugging could be a common problem with intermittently used quills
which remain in place.)
4.2 Injection quills could blow out of their packing gland during retraction without a
blowout prevention device.
4.3 Thermal fatigue due to temperature cycling could cause equipment failures at
mixing points and injection points. This cycling could be a function of flowrate
and/or temperature differences of the streams being mixed, as well as
fluctuations in them.
Section 4.3 Figure
Hotter
Stream
Localized
temperature swings
could result in
fatigue failure
Cooler
Stream
4.4 Pressure cycling and flow induced vibrations at mixing points and injection
points (especially those resulting from multi-phase flow regimes or flashing)
could cause fatigue and associated equipment failure.
Note: This hazard identification document is a generic, non-comprehensive synthesis of inherent concerns and / or hazards for
the related topic. It in no way alters any legal requirements. It is not intended to replace sound engineering analysis or
judgment.
HAZ002.000
HAZARD IDENTIFICATION
Injection Point and Process Mixing Point Hazards
4.5 Shutoff valves for intermittently operated injection points could leak through and
result in accelerated corrosion.
5.0
Inadequate
Equipment Condition
Monitoring
5.1 Inspection techniques consistent with the specific damage mechanisms and
their probable locations at mixing points and injection points that are not
identified and routinely used.
5.2 Equipment deficiency limits that are not set and enforced for the integrity of
mixing point or injection point associated equipment.
5.3 The flow pattern/s from the quill/s associated with an injection point that is not
verified on a periodic basis.
References and Resources:
API 570 – Piping Inspection Code; In-service Inspection, Rating, Repair, and Alteration of Piping Systems, Fourth Edition,
February 2016
NACE Technical Committee Report 34101 “Refinery Injection and Process Mixing Points”
NACE SP0114-2014 “Standard Practice Refinery Injection and Process Mixing Points”
Inspectioneering Journal – July/August 2013 “The Many Parts of Injection Points”, Available at https:/inspectioneering.com/
API RP 932-B – Design, Materials, Fabrication, Operations, and Inspection Guidelines for Corrosion Control in
Hydroprocessing Reactor Effluent Air Cooler (REAC) Systems. Second Edition, March 2012, Errata, January 2014.
Industry Incidents:

May 5, 1988 – Incident at Norco, LA, Refinery

October 8, 1992 – Incident at Wilmington, CA, Refinery

April 16, 2001 – Incident at United Kingdom Refinery

November 20, 2008 – Incident at Tyler, TX, Refinery
Note: This hazard identification document is a generic, non-comprehensive synthesis of inherent concerns and / or hazards for
the related topic. It in no way alters any legal requirements. It is not intended to replace sound engineering analysis or
judgment.
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HAZARD IDENTIFICATION
Injection Point and Process Mixing Point Hazards
Appendix Figure 1
Failure of Elbow Downstream of Injection Point on Overhead of De-ethanizer Line
United Kingdom Refinery Failure April 2001
Appendix Figure 2
Fire Following Failure of Naphtha Line at a Mix Point Tyler, TX, Refinery
Failure November 2008
Note: This hazard identification document is a generic, non-comprehensive synthesis of inherent concerns and / or hazards for
the related topic. It in no way alters any legal requirements. It is not intended to replace sound engineering analysis or
judgment.
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HAZARD IDENTIFICATION
Injection Point and Process Mixing Point Hazards
Revision
Date
Summary of Changes
1
11/06/2015
First Draft With Illustrations
2
01/16/2016
Draft with Subgroup Submitted Comments
3
01/25/2016
Draft with Comments from Subgroup Joint Review
4
01/30/2016
Draft with Late Comments from Subgroup
5
03/16/2016
Final with Legal and MI Task Force Comments
Note: This hazard identification document is a generic, non-comprehensive synthesis of inherent concerns and / or hazards for
the related topic. It in no way alters any legal requirements. It is not intended to replace sound engineering analysis or
judgment.
HAZ002.000
7