Ruttie,
have you tried to put the same thread into the "Piping & fluid mechanics engineering Forum" (Forum378) and/or into the "Chemical plant design & operations Forum" (Forum124)?
I would also suggest to search the web for Plant Maintenance Engineers' sites...
Bye, 'NGL
For more information on Control Valves, problems & solutions visit "ccivalve.com" ( contact - Control Components Inc.California, Tel 001-949-858-1877.)
If it is intended for reliability assessment / analysis the common control valves suppliers fail to give accurate reliability data. The best you will find is them promoting smart psoitioners claiming that htese enhance reliability, but no mention of statisticla reliability data of the valve themself.
Mokveld Valves (from Holland) have certified reliability data avaialable (at least for their shut-off valves). Try to contact them, maybe they have cert's or reliability data for the control valve range as well.
For many years Norwegian and foreign oil companies have been collaborating with SINTEF Technology and Society, Dept. of Safety and Reliability, DnV (Oslo) and other consultants in the collection of data on maintenance, reliability and safety of offshore installations. Used in conjunction with specially developed software, these data provide a basis for the preparation of reliability analyses. Such analyses simplify the job of selecting the "best" technical solutions and have led to significant savings in the development and operation of platforms.
Purchase the handbook and you will get reliability data on much equipment including valves.
Just for information:
the standard IEC 61508 has identified four different Safety Integrity Levels (SIL), which are defined by applying risk assessment criteria in various areas (personnel, environmental, production & equipment) and failure modes analysis (see also FMEA as a "Six Sigma" tool...).
Some valve (and actuator) Manufacturers have their SIL calculated by specialized consulting companies and certified by Third Parties (such as Lloyd's Register or similar).
For examples, try to visit
By now you may be armed with the offshore reliability data. You also state that your issue is with manufacturing. Consider other perspectives.
Predetermined failure position.
In the control system business we address the topic of control valve failure as it relates to the spring action. Engineers determine the prefereed failure mode. Usurally we want the steam valve that provides energy to a chemical reactor to fail closed. Perhaps we want the cooling water to the same reactor to fail open. These are actuated valves that typically use a spring-opposed diaphragm or piston to move the valve. Upon loss of the actuating supply medium such as air or hydraulic pressure, the spring moves the valve to the predetermined safe location. In these actuated valves the term failure can be interpreted as loss of the actuating medium. Besides failure of the air compressor system, wet dirty air is a common cause of air supply problems. In cold climates por quality air can freeze.
Valve trim problems are often a function of the misapplication of the valve more than a manufacturing issue. Water can wire-draw the plug and seat of a control valve plug when it operates very near the seat. This can occur with some of the hardest trim materials. The controls can be applied to avoid operation with the plug near the seat. Many misapplication issues exist. Some valves intended for open/closed operation may be used to throttle. Misapplication is a far greater problem for control valves than manufacturing.
Bubble-tight shutoff valves work great in the lab. However, just the rust and dirt contained in hydrostatic testing fluids can scratch the seating surface for a ball-valve in a manner that causes some leakage.
The list of valve failure issues can go on forever. What issues are of interest in your question?
