Control Valve Cutting
Control Valve Cutting
(OP)
I'm trying to replace/modify a series of valves that reduces pressure from 1600 psi to 400 psi. There is currently one PRV along with an isolation valve in series. Both get steam/condesate cut in a matter of months. These valves are cycled approx. twice a day.
Will replacing the isolation valve with another PRV help the situation? This would allow two pressure drops across two valves from 1600 to 400 psi.
Also, does steam cut valves when they are cycled or condesate or both?
Thanks for the input.
Will replacing the isolation valve with another PRV help the situation? This would allow two pressure drops across two valves from 1600 to 400 psi.
Also, does steam cut valves when they are cycled or condesate or both?
Thanks for the input.





RE: Control Valve Cutting
How do you plan to control the two valves in series?
Typically, a two phase mixture at the inlet to a control valve is a no-no and should be avoided. Perhaps you could provide a bit more detail on the application.
I2I
RE: Control Valve Cutting
I would use a split range controller to control both valves.
There is approx. 16 ft of vertical 2 inch pipe down from the steam drum to the control valves. The steam drum contains 1600 psi sat steam. These valves are used twice a day for about an hour. While the valves are closed, I assume that the 2 inch vertical pipe begins to fill with condensate. There is no steam trap upstream of the valves.
Thanks again.
RE: Control Valve Cutting
RE: Control Valve Cutting
If this is a blowdown valve, I definitely would not recommend using two valves. I think your best solution is to purchase a valve suitable for the operating conditions. The service conditions are not unusual and a competent valve supplier should be able to get you the right valve provided he's given the correct information to do so.
I2I
RE: Control Valve Cutting
Like JLSeagull suggested, wire drawing may be the issue. The valve could possibly be over sized.
Thanks for the input.
RE: Control Valve Cutting
It's very likely that the failure is a result of wire drawing/improper valve sizing. You may be able to just change out the trim (different design/materials) without buying a complete new valve. Talk to the OEM for guidance on this. The use of a hard faced overlay will help resist the wire drawing; however, it will still fail eventually. If the valve is mis-sized, correct that problem first.
I2I
RE: Control Valve Cutting
Firs, I would talk to the sootblower supplier because they usually have guidelines about the design of inlet piping to prevent damage to the valve. Such guidelines can include ensuring that the common sootblower supply pipe vertical with a steam trap at the botoom to clear the condensate and the steam supplies to individual blowers branch off horizontally from the main with the lowest branch being 1m from the ssteam trap.
Regards,
athomas236
RE: Control Valve Cutting