Use of Plug Valves
Use of Plug Valves
(OP)
We have a design on an influent pump station at the start of a wastewater treatment plant that uses Check and Plug Valves on the discharge side of the pumps. I need to know why plug valves are better for this operation versus using gate valves? Thanks.
RE: Use of Plug Valves
RE: Use of Plug Valves
RE: Use of Plug Valves
That may be a wrong (unintentional) option. It is always better to use control valves on the pump discharge rather than on/off valves. A gate valve (if disc seat contact is good) is a better option.
Regards,
Truth: Even the hardest of the problems will have atleast one simple solution. Mine may not be one.
RE: Use of Plug Valves
RE: Use of Plug Valves
You stole my thunder...I have yet to find an application where a plug valve is the best choice. In fact, I have outlawed plug valves from my factory. After a few years, they usually turn with great difficulty or not at all.
One caution on the quarter-turn valves; operators need to understand what water hammer is, and how to prevent it by operating these valves slowly. Other than that, I would go with a good quality ball valve any day over a gate. They're compact, easier to operate, and usually hold better and have less stem leakage.
RE: Use of Plug Valves
I'm with Ken, I've never found a case where a plug valve was among the top 5 choices. Even if you follow the mfgr recommendation and grease them frequently, they are still hard to operate and don't seal all that well.
As to using gate valves for a throttling application, they have very similar (bad) throttling characteristics as a ball or plug valve. None of the three should ever be installed in an application where they would normally be partially closed.
RE: Use of Plug Valves
RE: Use of Plug Valves
My comments above apply to traditional ball valves with a simple hole bored through a ball.
David
RE: Use of Plug Valves
I run into lots of plug valves on older installations all the time. You see them a lot in old gas plants, oilfields, and old LPG/NGL terminals. I think it's because 50 years ago there were no PTFE seals, so if a 1/4 turn valve was wanted, you used a plug valve. I'm with all you guys - they are usually stuck open or closed and they frequently leak by when closed. A plug valve is not acceptable by most plant owners for use in double block and bleed service, for example. We replace them routinely nowadays with some other valve. I don't know of anyone who specifies them for new installations.
Thanks!
Pete
RE: Use of Plug Valves
We have a well known gathering, processing, transportation company here in the four corners that still specifies that ONLY plug valves will be installed. When I asked one of their engineers why she said that no one had revisited their bid specifications since plug valves where the only choice for 1/4 operations (which was really less than 20 years ago).
RE: Use of Plug Valves
The plug valves mentioned in this thread are not the "TWIN SEAL " kind ? Or could they also be included?
TIA
DKF