Understanding Valves and Their
Role in Mechanical Integrity
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Understanding Valves and Their Role in Mechanical Integrity
CONTENTS
Introduction
4
Industry Standards and References
4
Valve Types and Usage
5
Critical Check Valves and Emergency Isolation Valves
8
Mechanical Integrity Considerations
8
Conclusion
12
References
12
Understanding Valves and Their Role in Mechanical Integrity
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Introduction
Owner/operators who are responsible for the mechanical
ASME B16.34 1, Valves—Flanged, Threaded, and
Welding End
integrity of valves often lack knowledge and background
According to ASME:
experience in valve anatomy, valve inspection, and valve
maintenance. This may be because, at least for API in-service
inspection codes commonly required for in-house inspection
positions (i.e., 510, 570, 653), valves are described in vague terms
and leave many details up to interpretation by the owner/
operator.
ASME B16.34 Valves Flanged, Threaded, and Welding End
applies to new construction. It covers pressure-temperature
ratings, dimensions, tolerances, materials, nondestructive
examination requirements, testing, and marking for cast,
forged, and fabricated anged, threaded, and welding end
and wafer or
Valves critical to process safety should require the same attention
to detail as any other fixed equipment or piping system
components. Often, the responsibility to inspect and maintain
valves is delegated to outside valve repair facilities. Owner/
operators typically offer minimal input outside of their standard
specifications. It benefits owner/operators to know and
angeless valves of steel, nickel-base alloys,
and other alloys.
Intended for manufacturers, owners, employers, users and
others concerned with the speci cation, buying,
maintenance, training and safe use of valves with pressure
equipment, plus all potential governing entities. [1]
understand the details involved with valve inspection and
In short, ASME B16.34 is the design book for valves. As it relates
maintenance and how it affects their mechanical integrity
to inspection, this standard is primarily used as part of the QA/
programs.
QC process during manufacturing. Outside of manufacturing, it
Even something as simple as an external visual inspection can
be more effective with a basic understanding of valve anatomy
and common problems associated with them. Understanding
how the hardware on the outside affects the hardware on the
inside adds value to the external visual inspection. It is hard to
is often referred to by engineering during design and project
development as it provides dimensions, materials, and pressuretemperature ratings that can be helpful with valve selection. It is
not the type of document that is routinely referenced by
inspectors, but it can be a helpful reference in certain situations.
seen the inside of that type of valve or understanding how the
API 570, Piping Inspection Code: Inspection, Repair,
Alteration, and Rerating of In-service Piping Systems
internal parts move. Knowing what sounds to listen for, how
API 570 is one of the primary standards referenced in
internal seals are made, and potential leak points can help
mechanical integrity programs for inspection, rating, repair, and
inspectors make credible assumptions and recommendations to
alteration of in-service piping systems. This code gives general
maintain the integrity of valves.
guidance for valve inspections, both internal and external.
This eBook covers valves and their role in the overall mechanical
API Recommended Practice 574, Inspection
Practices for Piping System Components
visualize what is going on inside of valves without ever having
integrity process. First, we will discuss the various valve types,
their common uses, and the governing standards and
recommended practices that apply. Second, we’ll discuss the
common failure mechanisms affecting valves, the potential
causes of the failures, and what can be done on-line to detect
and/or prevent them from happening in the rst place.
API RP 574 discusses inspection practices for piping, tubing,
valves, and
ttings used in petroleum re neries and chemical
plants. This document supplements API 570, going further indepth with the inspection of piping systems, including valves.
Section 4.3 goes into great detail about the many types of valves,
Industry Standards and References
including their operation and internal components.
For starters, we will discuss the industry standards and
API Standard 598, Valve Inspection and Testing
recommended practices that apply to the inspection, testing, and
maintenance of valves.
API Standard 598 is a supplement to API 570 and API RP 574. It is
primarily used by valve manufacturers and valve repair shops
when inspecting and testing a
nal product, whether new or
repaired. In particular, it covers “inspection, examination,
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for resilient-seated, nonmetallic-seated (e.g., ceramic), and metalto-metal-seated valves of the gate, globe, plug, ball, check, and
butter y types.” [2]
Valve Types and Usage
Next, let’s discuss the most common valve types. Each valve type
is different and serves a speci c need. It is important to know
the difference between valve types and their individual
anatomies in order to understand the proper application and
potential problems associated with each type.
Common valve types include gate, globe, plug, ball, diaphragm,
butter y, check, and slide valves. They are made in standard pipe
sizes, materials, thickness, and pressure ratings. Valve bodies are
typically cast, forged, machined, or welded. The seating surfaces
can either be integral or made as inserts. Inserts allow for the
seat material to differ from the body material. For instance, a
carbon steel body ange may have stainless steel seat inserts to
minimize wear and tear over time. Valves are either
anged,
threaded, socket welded, or butt-welded depending on the
process conditions and piping speci cations.
Figure 1. Gate valve cutaway. Image courtesy of Bayport
Training & Technical Center.
Gate Valves
A gate valve, often referred to as a “block valve,” consists of a
tapered, with the taper getting steeper for ne-throttling service.
valves are either completely open or closed. They are not
Globe valves are typically used in locations where ow control is
intended to be used to regulate ow by “throttling,” as that will
essential. They are considered uni-directional and must be
typically wear and erode the gate and seats.
installed in proper relation to the media ow as indicated by the
Standard gate valves are the least costly of the valve types and
are one of the most common valves in the re ning and
petrochemical industry. They are suitable for most services and
they can easily be actuated via electric, pneumatic, or piston
by “throttling” the valve to the proper position to maintain a
speci ed pressure, temperature, or level. Because of their ability
to throttle and regulate
ow, globe valves are often used as
control valves.
Since they are typically designed to be open or closed, gate
Plug Valves
valves are often set in position and left alone until needed for
A plug valve consists of a tapered or cylindrical plug
maintenance. In some cases, like with site-wide utilities such as
snugly into a correspondingly shaped seat in the valve body.
water, steam, air, nitrogen, etc., gate valves may remain open or
There is an opening in the plug that lines up with the opening of
closed inde nitely.
the valve body when in the open position. Plug valves can be
Globe Valves
used for isolation (similar to the gate valve) or
with a circular disc that contacts the seat and moves up and
down, parallel to the disc axis. Globe valves distribute ow more
evenly across the entire seat to reduce wear; therefore, they are
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Understanding Valves and Their Role in Mechanical Integrity
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ow direction arrow marked on the valve body. Flow is managed
style units.
A globe valve is a linear motion valve consisting of a valve body
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commonly used to regulate uid ow. The seat can be at or
ow. Typically, gate
body that contains a gate that interrupts
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supplementary examinations, and pressure test requirements
tted
ow control
(similar to the globe valve).
The plug is integral to the handle. Because of the design, the
valve opens and closes with just one-quarter of a turn. For larger
valves, and for valves requiring even distribution during
Inspectioneering.com | Page 5
Figure 3. Plug valve cutaway. Image courtesy of Bayport
Training & Technical Center.
Figure 2. Globe valve cutaway. Image courtesy of Bayport
Training & Technical Center.
operation, a gear operator can be installed to prevent sideloading.
Plug valves are used in many processes and are engineered for
high-cycle, low-emissions service. They are used with
con dence in applications where tight shutoff and emissions
containment are essential. Because of their performance, plug
valves are commonly used in HF Alkylation units. Besides HF
Figure 4. Ball valve cutaway. Image courtesy of Bayport
Alkylation units, plug valves are also used in isomerization,
Training & Technical Center.
blending, light ends, gas plants, sulfur plants, and crude
With pressure-assisted sealing, they have become a preferred
desalting.
valve for many applications. Critical service ball valves are found
Ball Valves
in Distillation, Reforming, Fluidized Catalytic Cracking (FCC),
A ball valve is another type of quarter-turn valve that is similar
Hydrotreating, Hydrocracking, Delayed Coking, Gasi cation,
to a plug valve except that the ow restriction in a ball valve is
and other re ning units.
spherical instead of tapered or cylindrical. Similar to plug and
globe valves, ball valves are used as block valves or for
ow
control. Ball valves are great for quick on/off applications or in
A diaphragm valve is a packless valve containing a
processes requiring a bubble-tight seal. Typically, ball valves
diaphragm on the inside. When the valve is closed, the stem
have a coating around the surface of the ball that serves as a
pushes down on the diaphragm. The diaphragm presses against
sealing medium.
the seat or dam to form a seal and block the ow of uid. When
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Diaphragm Valves
exible
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Figure 5. Diaphragm valve cutaway. Image courtesy of
Bayport Training & Technical Center.
the valve is opened, the diaphragm raises from the seat or dam
to resume ow.
Figure 6. Butterfly valve cutaway. Image courtesy of Bayport
Training & Technical Center.
The metallurgy of the diaphragm is chosen based on the process
conditions (e.g., corrosivity, abrasiveness). They are ideal for
creating a tight seal in abrasive services with some amounts of
solids. They are not used in many places, but they are commonly
found in uid catalytic cracking (FCC) slurry services.
They are not designed for tight shut off; rather, they are
designed for erosive and high-temperature service and can be
used for both “throttling” or blocking.
The most notable application is in the FCC units. FCC slide
Butterfly Valves
Butter y valves consist of a disc mounted on a stem within the
valve body. Similar to a ball valve, butter y valves are a quarterturn valve designed for quick shut off. However, butter y valves
are generally favored over ball valves because of the reduced
valves will typically have an erosion-resistant overlay or
refractory due to the high wear to the internal surface from the
catalyst.
Check Valves
cost. Butter y valves are most often used in low-pressure service
Check valves are used to mechanically prevent back ow without
for coarse ow control. The seating material is chosen based on
human intervention. They are designed to close automatically
how tight of a seal is required.
when back ow occurs. There are many types of check valves
Larger butter y valves are typically found in cooling water
service connected to the cooling water pumps and exchangers,
and are typically operated mechanically or with a gear operator
to prevent the valve from slamming shut while turning.
Slide Valves
including swing, piston, and spring-loaded wafer check valves.
Check valves of all types are used widely throughout the
industry. They’re most commonly found on the discharge of
pumps to prevent reverse
ow and damage to the pump
internals. The spring-loaded wafer type check valves are
commonly found attached to tank
Slide valves are equipped with a
at plate that slides within
oating roof drain piping
within the roof sump.
guides on each side to the seat that is similar to a guillotine.
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longer a recommendation to inspect or test CCVs; it is a
requirement.
EIVs are also among the commonly considered engineered
safeguards. An EIV is a special category of valve that is dedicated
to the purpose of isolating
ammable or toxic material from
sources or equipment whose relative consequence of signi cant
leakage is high. In short, EIVs are valves that absolutely must
work when needed, which is usually during an emergency. Any
valve type can be classi ed as an EIV, including critical check
valves.
Identifying these CCVs and EIVs can be done in a few ways.
Figure 7. Ball check valve cutaway. Image courtesy of Bayport
Training & Technical Center.
in an unintended direction (reverse
Typically, the identi cation is led by process engineering.
Sometimes, a once-through effort takes place to identify CCVs
and EIVs to get them into the mechanical integrity program to
When a check valve malfunctions, it allows the process to ow
ow). In some cases, this
isn’t a major problem. For instance, a check valve installed on the
discharge of a water pump is usually there to prevent water
from backing up when the pump is removed for maintenance. If
begin with. In other cases, the identi cation of CCVs and EIVs
takes place through attrition during process hazard analysis
(PHA). Regardless of how they’re initially identi ed, the
recurring PHA is the primary method for keeping the list
evergreen.
that valve leaks, it is simply going to make a mess and be
Once a valve is identi ed as a CCV or an EIV, it should be stored
inconvenient for maintenance crews. On the other hand, the
in the site's inspection data management system (IDMS) along
proper function of some check valves is deemed critical to
with the appropriate inspection tasks, as with any other asset. As
process safety. These are typically designated as critical check
future PHAs and MOCs are carried out, EIVs and CCVs may be
valves (CCVs).
added or removed; these changes should be re ected within the
Critical Check Valves and Emergency Isolation
Valves
IDMS.
Mechanical Integrity Considerations
Now that we’ve discussed the basic valve types, we’ll transition
Understanding valves, their anatomy, and how they operate,
to particular classi cations of valves that belong in the
gives the inspector a better sense of what potential problems
mechanical integrity program: critical check valves (CCVs) and
exist. At the same time, knowing which problems are more
emergency isolation valves (EIVs).
common to a speci c type of valve allows the inspector to
CCVs are any check valves in piping systems that have been
identi ed as vital to process safety. CCVs are check valves that
connect these dots and formulate an inspection plan that
ensures the continued reliability of valves.
need to operate reliably in order to avoid the potential for
Ideally, all valves should work when needed; but the truth is that
hazardous events or substantial consequences should reverse
valves fail. While many valve failures may have minimal impact
on process safety, there are a number of valves whose failures
ow occur.
The fourth edition of API 570, released in 2016, addresses CCVs.
Section 5.13 states that CCVs “should be adequately inspected or
tested to provide greater assurance that they will prevent ow
reversals.” [3] The key here is the word “should.” It wasn’t until
the May 2017 Addendum to API 570 that the “should” was
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Understanding Valves and Their Role in Mechanical Integrity
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changed to “shall.” Because of this slight change wording, it is no
can potentially domino into safety problems or larger failures of
a process unit. EIVs and CCVs are highlighted in industry
standards and references because they’re vital to process safety,
and they should be included in mechanical integrity programs
to be inspected and maintained. However, the owner/operator’s
inspection group oftentimes has limited experience in this eld.
Inspectioneering.com | Page 8
Valves often seem to fall into the “gray zone” of equipment –
globe valves. Installing a globe or check valve backwards may
they don’t explicitly belong to one functional group or another.
cause damage to the valve or associated piping and equipment.
Along with a handful of other miscellaneous assets, valves tend
Uni-directional valves have
to slip through the cracks of expertise for owner/operators.
casting or forging to show the proper direction.
They’re typically maintained by third-party valve repair facilities
that are experienced and able to specialize in valves.
ow arrows built into the body
However, not all valves are clearly marked for direction of ow
and it’s important to refer to the manufacturer’s instructions
With this eBook, we hope to close the gap by discussing the
when performing valve installation and startup. Rising stem ball
common failure mechanisms of valves and give the inspector an
valves, which are common in re ning and petrochemical
idea of what to look for during an inspection. For externally
applications, are a good example. These valves are designed to be
detectable failure mechanisms, we will discuss the on-stream
installed with the core seat facing the inlet pressure. The valve
inspection methods used to detect premature valve failure and
may operate in a reversed ow condition, but over time this can
provide guidance for minimizing or mitigating these failures.
lead to performance and reliability degradation.
Valve Selection/Installation Flaws
In addition to the
Let’s start where it all begins: the pipe design and valve selection
that occurs on the front end, even before the valve is installed.
Valve selection includes design aspects such as valve type,
metallurgy, orientation, pressure and temperature rating, etc.
Issues related to valve selection usually arise when the process
conditions or the intended valve function are incorrect or not
ow direction, it’s also important to have
proper valve orientation. Check valves are especially sensitive to
valve orientation. If a swing check valve is installed such that
gravity causes the gate to hang away from the seat, then it’s
almost certain to not prevent back ow when needed. Similarly,
when a spring check is installed upside down, the weight of the
plug compresses the spring, thus taking pressure off of the seats.
understood during the selection process. For example, installing
In short, it’s important to ensure that valves are installed as
a 316 stainless steel valve in a service that was not expected to
recommended by the manufacturer and per the engineering/
have chlorides can lead to chloride cracking of the valve stem or
construction drawings.
body. Had the process conditions been fully understood, 316
stainless steel would not have been selected for this application.
Pressure and Temperature Ratings
As we discuss these common valve issues, you’ll nd that many
All valves come with design pressure and temperature ratings
of them can be tied to the pipe design and valve selection
set by the manufacturer. Typically, these ratings are listed on a
process.
tag attached to the valve handle or valve bonnet. It’s important
that the speci ed pressure and temperature ratings of valves are
Metallurgy
not exceeded. Doing so could lead to valve failures from either
Improper metallurgy selection is one of the most common
examples. As stated earlier, the improper metallurgy of valve
bodies, stems, seats, etc., usually occurs when the process
conditions were misunderstood or not fully considered during
selection. It’s important to have an understanding of the normal
process chemistry of the system along with any potential upset
overpressure or overheating.
Similar to direction and orientation, ensure that the ratings on
the valve tag matches the engineering/construction drawings.
It’s not uncommon to
nd a valve of an improper rating
installed where it shouldn’t be.
conditions that may change that chemistry. This responsibility
External Corrosion, Cracking, and Mechanical Damage
typically falls on the metallurgist and piping designer.
Even when designed properly for the service, valves are not
Direction and Orientation
immune to damage. External damage mechanisms still exist,
Attention should be paid to the correct installation of the valve,
and they affect valves of all types.
ensuring the valve is installed in the correct ow direction for
Carbon steel and low-alloy valves are vulnerable to external
the pipework in which it is being used. This is particularly
corrosion, especially in low-temperature services. Just like with
important for uni-directional valves such as check valves and
any other equipment, the coating still requires inspection and
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maintenance; and corrosion under insulation (CUI) inspections
valves, pro le radiography is a great tool for this and can be
need to be a part of the routine inspection plan. External
performed while in service.
corrosion not only affects the valve body, but it also affects the
valve hardware keeping the valve together. For actuated valves,
Cracking
Cracking is typically found on the internal tack welds, valve
the actuator housing should also be inspected.
External cracking is not very common, but it exists. Stainless
steel valve bodies are susceptible to chloride cracking, typically
induced from high chloride water (i.e., rewater, being used to
wash down the unit or from chloride leaching from insulation).
From an inspection point of view, there isn’t much that can be
done to prevent the high chloride water wash aside from
operator training, but a good under-insulation coating can help
minimize under-insulation cracking.
stems, guide pins, check valve hinges, and retainer hardware.
Most of the time, a cracked valve stem is identi ed by
operations when opening and closing the valve. It’s not
uncommon for cracking of internal tack welds to go unnoticed
until the equipment is removed for inspections. A simple dye
penetrant test (PT) will usually bring these cracks to light.
Pro le radiography can be used on smaller valves, while in
service, to inspect for valve stem cracking or other hardware
anomalies.
Mechanical damage is pretty self-explanatory. There are many
ways for a valve to inhibit mechanical damage, especially in a
re nery or petrochemical setting with heavy equipment moving
around. There is also the potential for operator-induced damage.
Pipe wrench marks on a manual valve stem are a sign that the
valve may be dif cult to actuate or to seal. In many cases, the
operator will apply too much torque to the valve stem, which can
cause galling on the seating surfaces. During inspection, be on
the lookout for bent valve stems or hardware. Bent valve stems
Mechanical Damage
Internal mechanical damage is caused by conditions such as
valve chattering or vibration, process debris, and water hammer.
Oftentimes, these will have audible signs that are noticeable
while in service. Operations are usually best suited to identify
“new” noises in the unit and will often ag these conditions for
follow-up inspections. In automated valves, operators can look
for erratic/jerky movement or increased opening/closing times
can deem the valve inoperable, and damaged hardware can lead
during operation as a potential sign of internal damage.
to leaks. Typically, mechanical damage to anges isn’t a major
Valve chattering and vibration can cause damage to valve gates
deal unless it infringes on the gasket area.
and seats. The constant contact between the gate, the guide, and
Internal Corrosion, Cracking, and Mechanical Damage
the seats creates an irregular wear pattern that eventually
Corrosion, cracking, and mechanical damage to valve internals
can vary widely depending on the service and operating
causes the valve to leak. It’s usually pretty obvious, visually,
when a valve has been worn in such a manner.
Damage from debris is typically easy to spot internally. Debris
conditions.
can be anything from vessel tray parts, process scale/corrosion
Corrosion
products, or trash that manages to get into the system during
Internal corrosion affects all metallic components, including the
shutdowns or maintenance. With check valves, debris can
body and trim. A good rule of thumb is that if you have corrosion
prevent the valve from stopping reverse ow. Debris is usually
in your piping, you likely have corrosion in your valves. A review
the result of poor cleanup after maintenance or shutdowns.
of corrosion rates from corrosion monitoring locations (CMLs)
Sometimes debris can be pushed through the system from an
should direct you to potentially problematic valves.
upset upstream. For smaller valves, when an obstruction is
Pitting on the trim or inside the valve body can be found with
visual inspection. When localized corrosion or washout of the
suspected, it’s common to perform radiography to con rm
whether or not an obstruction exists.
valve body is expected, it’s sometimes advisable to take
Water hammer is another cause of mechanical damage. It’s a
ultrasonic thickness (UT) measurements, since the corrosion
very common check valve problem that is caused by a pressure
may be too smooth to notice visually. For smaller diameter
surge when a liquid or gas is forced to stop or change direction
suddenly. Water hammer can result in both noise and vibration.
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performance over time allows a preventative maintenance
when
ow reversal downstream causes the valve to close too
strategy to be deployed as opposed to reactive maintenance.
quickly resulting in pressure waves throughout the pipe. It’s
Recording details like the mean time between failure (MTBF),
important for operations to recognize changes to the normal
the repair frequency, the repair costs, and other details allow the
sounds in the area and to bring up concerns to the inspection
operator to address the bad actors within their inventory.
group for further investigation. Water hammer can lead to pipe,
tting, and valve damage if not mitigated. Water hammer can be
minimized, and even eliminated, if the system and valve types
are designed properly.
Risk-based inspection (RBI) and maintenance strategies are also
common. With enough history and operating data, as well as a
clear understanding of the valve criticality, a risk-based approach
allows the operator to focus more attention on the higher risk
Normal Wear and Tear / Leaking Seals
Finally, there are issues related to normal wear and tear.
Although it’s expected, it’s still worth discussing ways to identify
valves. Age becomes a large factor, as the longer a valve remains
in service without inspection and testing, the higher the risk of
failure.
and minimize these issues. Most wear and tear damage is
There are many variables affecting valve inspection, testing, and
related to a lack of lubrication.
maintenance programs. An experienced valve service
With actuated valves, degradation of polymeric materials such
as valve seals, seats, actuator O-rings, or weather seals could
cause the valve to leak internally across the seats, leak to the
atmosphere, or lose ef ciency in operation. Degradation of the
case weather seals will lead to water ingress and accelerated
corrosion buildup in the actuator, which will also have a
detrimental effect on performance. Degradation of grease and
lubricants can lead to valve seizure or increased friction
resulting in the valve failing to operate as intended.
With non-lubricated valves, a Te on or soft metal material is
typically used as the sealing element. Te on and soft-seat
materials require replacement over time. Normal wear and tear
organization will be able to assist in the process of determining
inspection and maintenance protocols by means of reviewing
client data on each tag number in line with process conditions to
allow a criticality study to be prepared.
On-Line Valve Inspection and Repair
While on-line, there are a few ways to potentially detect some of
the problems above.
External visual inspection is one of the most effective methods.
It can be performed by inspectors during regulatory inspections
and it can be done during operator rounds, which typically take
place multiple times throughout the day.
is very dif cult to inspect while in service. Typically, the only
The external visual inspection should look for corrosion of the
sign of a leaking seal is a leak to the atmosphere. The only way
valve body, bonnet, and hardware. Valve body and bonnet
to properly inspect all sealing elements is to break the valve
corrosion can lead to through-wall failures, but it’s easy to
down and rebuild it.
mitigate with a simple clean and paint. Valve hardware
corrosion can also lead to gasket surface failures. Attention
Inspection Practices
should be paid to bonnet bolts, adjuster bolts, ange bolts, and
Now that we’ve discussed the types of damage to look for, we’ll
other applicable hardware. To stay ahead of the problem,
review good inspection practices and what should be included in
corrective maintenance should be documented and performed at
a valve inspection program.
the next opportunity.
Inspection Intervals
Valves in corrosive or erosive service can have on-line thickness
Inspection intervals will normally be determined by service,
operator requirements, manufacturer recommendations, and
regulations which can vary by location.
Many operators have extensive programs already in place to
measurements or pro le radiography performed while on-line.
These two methods can help identify corrosion and erosion
within the valve bodies. It is a good practice to review corrosion
data from the associated piping circuits.
capture valve performance issues. Regular monitoring of valve
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This phenomenon typically occurs in swing type check valves
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Fugitive emissions testing is a typical practice which can also
understanding of the inspection and maintenance demands that
help to identify valves with leaking seals, packing, etc.
they require. This is especially true for EIVs and CCVs. We hope
A common practice for determining EIV performance is to
“stroke test” the valve on a set interval. This involves operations
that this eBook has provided some insight into the role valves
play in the overall mechanical integrity process.
fully opening and fully closing the EIV to ensure that it has full
References
range of motion and will close if needed. Because of their
1.
ASME B16.34-2020, 2021, Valves – Flanged, Threaded, and
criticality, any issues noted during the stroke testing requires
Welding End, The American Society of Mechanical Engineers,
maintenance to be performed at the next opportunity.
https://www.asme.org/codes-standards/ nd-codes-
Off-Line Check Valve Inspection and Repair
standards/b16-34-valves- anged-threaded-welding-end.
Off-line inspection and repair of EIVs and CCVs require the valve
2. API Standard 598, 2016, Valve Inspection and Testing, Tenth
to be removed from the line. This can be performed in the eld
Edition, Section 1.1, American Petroleum Institute.
or sent to an offsite valve repair facility. The inspection typically
3. API 570, 2016, Piping Inspection Code: In-service Inspection,
looks for damage to the body or damaged internal parts. In some
Rating, Repair, and Alteration of Piping Systems, Fourth Edition,
cases, with erosive or corrosive services, thickness readings may
American Petroleum Institute.
be performed on the valve body.
In addition to the visual and thickness inspection, a simple
function test should be performed to identify problems with
valve operation. Common ndings include a stuck gate/ apper,
excessive play (wiggle room) of the hinges, lack of tension on
springs/hinges, etc.
Without fully disassembling the valve, there are some components
of the valve that will not be fully visible, such as the edges of the
hinge, the stem within the bonnet area, the top of the gate and some
areas of the seats.
Procedures and Documentation
For consistency in the inspection and repair process, it’s
important to have written procedures that are followed by
inspection or operation personnel. Checklists are often used to
generate trigger words and ensure a minimum expectation is
met.
Proper documentation of the inspections, including the details
of the valves, services, etc., allow for detailed analysis of the
results to be used during future inspection planning. This allows
for pattern detection where, for example, a particular style or
valve manufacturer is not performing well in a speci c service.
Conclusion
Valves are crucial to the ongoing operation of process facilities,
and yet they are oftentimes overlooked from a reliability
perspective. While it is true that some valves are more important
to process safety than others, it’s necessary to have a holistic
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Understanding Valves and Their Role in Mechanical Integrity
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Preserving Asset
Integrity in Every Stage
Inspections are vital to achieving asset integrity,
but at TEAM, they’re just step one.
We go beyond identifying potential problems to deliver the solutions you need,
when you need them. That means supplementing our inspection expertise with
maintenance and repair services that ensure the protection of your most critical
assets.
After we’ve inspected your valves, your pipelines or your tanks, trust TEAM to
provide innovative maintenance and repair solutions to keep those assets up and
running. To learn more about how we can contribute in every stage of asset
integrity.
Visit us today at TeamInc.com
Understanding Valves and Their Role in Mechanical Integrity
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