Common Valve Failure? 5

[MudBugg]

I am working on a small project for my company who uses various Valves in a production line. What are some of the common failures for valves such as Gate Valves, Ball Valves, Check Valves, etc? I will be compiling a 'cause code' sheet to fit in with the Root Cause Analysis project, so breaking down failures to specific areas of the valve would be appreciated! I'm going to start off with the little pieces I have gathered so far, please feel free to let me know if I am on track.

Body > Corrosion
Fatigue
Stem > Corrosion
Fatigue > High Torque
Seals >

 

[gerhardl]

The type of failures you will get will in a high degree be depending of the quality of the valves different parts and quality and how suited they are compared to the process media and conditions.

As the process seems to have a larger number of different smaller valves, one way could be to build on existing experiance and routines, and change complete valves and check types of wear/failures after a preplanned periode and system.

I gather your purpose is to preplan maintenance. This again to have as few unplanned stops as possible and select valve and parts quality, maintenance or new valves to have best cost/lifetime value.

part of this would also be to chart how much wear is acceptable before the process get disturbed.

Apart from this, you will probably have a failure rate, a bit different on the different types of valves, but perhaps mainly (if valves materials are selected to suit process)

Sealings: wear of stem sealings and seat sealings.

Seats: wear of seats.

Wear of stem (depending of valve/stemtype) mostly caused by penetration of seals and deposits on stem.

Same as above for balls.

Corrosion (only by uncorrect or poorer quality of (inner?)part of body (material and/or protection) compared to fluid requirements.

Cavitation (by wrong selection or throtteling of valve comared to flow and delta p)

Remember that dirt, deposits, and particle abrasion and 'non optimum clean' fluid condition often are the strongest contribution to wear.

preventive maintenance should start with a check of what can be done to have ckleanest possible inner piping system and fluid, and optimum layout of total piping systes.

 

[TechThreads]

Ball valves #1 failure... stem leakage !

 

[MikeHalloran]

Stem leakage could be classified as one form of 'external leakage', and applied to all valves.

All valves are subject to failure by 'internal leakage', i.e., the valve does not completely shut off the flow when it's nominally closed, for whatever reason.

Another common failure mode is that the valve gets stuck, i.e. the stem or operating handle cannot be moved except by extraordinary means.

Less common failure modes include outright fracture, e.g. of bodies by freezing trapped water, of ends by application of excessive bending moment or makeup torque.


Mike Halloran
Pembroke Pines, FL, USA

 

[NGiLuzzu]

Some more information, based on statistical studies, about the effects of the mentioned "failure mode" (external leakage) may be found within an interesting pubblication by the European Sealing Association (see, in particular, pages 13 and 14, and paragraph 8.4 at page 52):
--->

http://www.europeansealing.com/uploads/resources/publications/ESA-Sealing-BAT-014_09_ENG_rev1.pdf

Besides this, some valve Manufacturers publish documents about their products' SIL (Safety Integrity Level, according to IEC 61508 and/or IEC 61511 standards), MTBF, FMEA, etc.: perhaps their identification of the possible valves "failure modes" may represent a good source of inspiration...


Hope this helps,
'NGL
___________________________

 

[ValveSteve]

With knife gate valves, a common failure is in the packing which eventually looses it's seal. When this happens, we send a kit with new packing and instructions to repack.

 

[HitokiriAoshi]

I would separate Root Cause with Incident report. Leave the root cause analysis to the experts and just make sure you properly report the problem.

Regardless of valves.

Failure modes:

Operation Failure
- Cannot be operated
- Excessive torque to operate
- Fail to fully open
- Fail to fully close
Failure to Seal
- Passing in a closed position
Failure to retain pressure
- Leaking outside the system through ____________ Connection
- Leaking outside the system through material defect in Body
Excessive Vibration/Noise

That should get you started and should cover Most incidents, root cause varies and would take too much work than a forum to figure out. (certainly will not be able to be covered with drop downs)

 

[YBM]

Nice listing of failure modes.

Add to this, improper selection, and failure of the operator to maintain, service, and observe the valve.

(Most valve failures are predictable, and therefore preventable. Operators will give their bicycles better maintenance than a valve.Okay so I exaggerated.)

 

[gerhardl]

xsnipersgox: I liked your way of systemating things. Normally it would however in my opinion be practical and easy to add some comments on cause, and yes:

vbm:... how true, how true, and perhaps not exaggerated!

 

[stanier]

Some thoughts away from mainstream:-

Check valves installed the wrong way around. There was a famous plane crash where the arrow on the hydraulic check valve was cast incorrectly the wrong way around.

Check valves selected without design for dynamic conditions. In a surge analysis the reverse velocity vs the dv/dT needs to be determined and the valve selected accordingly.

Air valve selection can be too large or small. The selection and location needs to consider filling, draining, pipe burst and dynamic behaviour of the system. Also if buried in a bolted cover pit they cant vent of fill.

No maintenance on sewage air valves and they clog up.

Valves selected for solids service need to be considered for wear of components. Sewage is a nightmare as stringy parts catch up in the system.

Wafer butterfly valves stcuk in the open position unable to be removed without massive excavation of the pipeline. Wafer valves selected without considering removal of pipe or equipment downstream. Select full flange type.

Incorrect or no drawings of the valve installation so cannot be found when you need to isolate or maintain. Sydney Water had to get someone out of a retirement village hoping his alzheimers hadnt kicked in as this guy was the only one who knew where a particular isolation valve was buried.

Knife gate valves where fastners in the chest bear onto the slide plate and stop it operating.

Inside screw gate valve in dirty or corrosive service.

Relief valves unsupported so discharge force stresses pipe.

Suggest you get hold of the book " What went wrong!"

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[asbaraheem]

i have problem with the tilting check valve. the disc was fall down because of the damage on the handling pin. so i need your help and investigation soon .

 

[asbaraheem]

i would like to inform you that the valve located in the discharge of the main boiler feed pump

 

[vpl]

asbaraheem

Please start a new thread. You might also want to provide more details about your problem.

Patricia Lougheed

******

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.