REPOSTING a user thread as there is a ton of great knowledge here that we hope others can benefit from. Please note that Jim Cahill is not the source of the original post.
We face problem with, one of the valve was installed in our plant. After two or three years, the valve body and trim corroded and need to be replaced, we replace it two times, but did not find exact reason to solve it. The valve specification as below:
Body size: 12” trim:8”
Material: monel
Service: sea water
Pressure:15 Bar
Trim type: anticavitation, cavitrol III
body and cage photos o
Hi all,
Lots of great information here!
As Eric correctly noted, the process conditions provided would result in cavitation that may be damaging if the incorrect valve construction is selected. Based on the pictures, it appears that a one-stage Cavitrol III anti-cavitation trim was in use, which should be acceptable for the conditions provided. However, the alarming part is the location of the damage on the cage. Cavitrol III one-stage trim is designed to be “flow down” which allows the cavitating liquid to recover in the center of the cage, away from any critical trim or valve body surfaces. The cavitation damage shown here is quite clearly occurring on the outside of the cage, indicating that the valve and trim is probably being “flowed up”, which is the incorrect direction for this trim. Flowing up allows the liquid to recover to a higher pressure while it is still in the holes of the cage and would result in damage consistent with what is shown in the pictures of the cage and body. Of course, the best way to know this for sure is to work with your local sales office and/or local Fisher Instrument and Valve Services office to evaluate the current valve installation and process conditions.
For more information on cavitation and the solutions that Fisher can provide, please see the links below:
Fisher Cavitation-Control Technologies: www.documentation.emersonprocess.com/.../d351912x012.pdf
Fisher Cavitrol III Trims: www.documentation.emersonprocess.com/.../d100196x012.pdf
Regards, Jake