what could be the reason for the da

[Amir Nagy]

what could be the reason for the damage of the valve plug end ,this valve ( Pump Minimum flow Valve ) is designed for up stream water temperature around 180c and pressure 250 barg and the down stream water temperature 180c and pressure around 8 barg.

 

[casflo]

Probably the cause of the damage is the cavitation. If the water temperature is 180ºC, its vapor pressure is approximately 10 bara and the cavitation index is (265 - 10)/(250 - 8) = 1.05
You need a valve with a cavitation coefficient equal or less than 1.05
The damaged valve surely has a cavitation coefficient greater than 1.05 and therefore has cavitation.
You need an anticavitation valve with a cavitation coefficient close to 1 or alternatively divide the total pressure drop using two or more valves in serie.
In any case, you must ask to the valve manufacturer which is the cavitation coefficient of the valve, but according the valve design of the photograph, it seems that have a cavitation coefficient much greater than 1.

 

[shvet]

Cavitation caused by improper design of valve internals.
See chap. 6 Fisher's Control Valve Handbook. Power&Severe Services

 

[pierreick]

HI,
Consider this link to support your query, cavitation seems the answer and remedy, staging.
sigma = (251-11)/ (251-9) <= 1 means flashing.

https://www.flotechinc.com/understanding-predicting-cavitation-control-valves/

Pierre