Hi pdp123,
Simplified answer. For commodity / common valves, if:
- the piping material can handle it (assuming the valve body is the same with piping)
- Not prone to water hammer, cavitation, or other erosion possibilities e.g. located at Dead lag such as Drain, low differential pressure, low velocity, etc.
- Not critical function wise. Risk of failure is ALARP
- End user aware that the valves deemed to fail and capable to interchange it with new ones (because its relatively cheap) with minimum to no downtime
- Etc.
Then the trim reasonably can be made from the same sort of material as valve body. A manufacturer requires valve stockist turn over also, as well as end user requires low cost replacement program instead of maintenance/repair.
In some cases, for relatively expensive custom valve which are:
- Critical for Process and safety.
- Normally for throttling function
- Prone however design for cavitation, etc. which may lead to vibration
- Other numerous factors.
Applying a stiff yet brittle (corrosion or erosion resistance) material on trim are deemed to have brittle fracture failure.
Therefore applying a softer material (often overlay with Hard Facing) which may be the same with Body material, may do the trick. It will damp the vibration and deemed to be only experiencing wear instead of fracture / creep.
Etc. etc., others may have different view.
Regards,
MR
All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected
