We replaced the seat of Fisher Control valve HPT Size 6 inch S/N 18591010 HPT globe valve NPS 6 Rating : CL 1500 / 3750 PSI CWP. due to passing issue.
However after six months, again passing started. As the utility is to control drum water level, there is excessive throttling in line with variation of steam generation requirement from the HRSG unit. Gradually passing has increased to level of ~130 t/h over 2 years time.
From understanding that the amount of valve movement should not adversely affect the life of the throttling portion of a control valve, but it will affect the time between packing failures. However we are not experiencing packing leakage from the valve.
Can suggest if anyone else has experienced same thing and is this related with suspected flashing/cavitation or erosion issue?
However after six months, again passing started. As the utility is to control drum water level, there is excessive throttling in line with variation of steam generation requirement from the HRSG unit. Gradually passing has increased to level of ~130 t/h over 2 years time.
From understanding that the amount of valve movement should not adversely affect the life of the throttling portion of a control valve, but it will affect the time between packing failures. However we are not experiencing packing leakage from the valve.
Can suggest if anyone else has experienced same thing and is this related with suspected flashing/cavitation or erosion issue?