Hi, I am new here. I need some information regarding plug valves. Can they be used in compressed air pipeline (100NB, 8 bar)? Thanks in advance for the advice.
Depends where you want to use it.
Plug valves are normally not used in the main pipeline, because of their flow pattern and historic sticking problems.
They have found more service in lateral connections off the mainline where frequent use and finer flow control for blowdown or throttling is needed.
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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)
To elaborate, plug valves are a metal-to-metal seal so they are not expected to be bubble tight and they usually leak by. The hole in the plug is smaller than the nominal pipeline diameter so they are usually not piggable. They require regular maintenance or they will not operate. They may be a poor choice for main lines, but they are also a poor choice for laterals in gas lines. I cannot think of a single place in air service where I would prefer to use a plug valve over a ball valve or even a gate valve
Not all plug valves have metal to metal seats. Valves with PTFE sleeves are fairly common in the chemical and water treatment industries. Fully lined valves are also available. In many cases, they offer a price advantage over comparable ball valves, and are cast is a wide variety of alloys. They are also inherently cavity-free and come in a variety of multi-port configurations.
No - I'm not a plug valve peddler. Like zdas04, I also have a preference for ball vavles.
I also prefer ball valves, but that wasn't the question. I have used many smaller plug valves with elastomeric seats for high pressure blowdown apps. as was required at the time by the gas pipeline transmission company piping specs for that type of service. No problem with leaks and gave better control over blowdown flowrate when selected with the correct pattern, which is why they were speced over ball valves for that purpose.
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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)
I'm going to have to have a talk with my valve peddler. The only plug valve he shows has metal seats. I don't know why that is. The catalog I was looking at had a disclaimer that the valves must be serviced quarterly or risk seizing. I've never seen pipeline valves get annual service let alone quarterly.
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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)
They have been used extensively in the Danish NG network, e.g. at plants where extensions with parallel trains called for DBB. Here these valve can give true DBB but they have the same build length as a std. ball valve. Im not working for this outfit - or selling their product but they have been recommended to me by persons i trust.
But i think that you should remember that sometimes you get what you pay for - there are many manufactores out there and they service many markets. Some may be too expensive - some too cheap for your purpose.
Cute valve. It looks like the plugs are about half the diameter of the flow so I don't want to think about the permanent pressure drop across the valve.
In terms of "true double block and bleed" that term is not very well defined anywhere. My interpretation of such definitions as I've seen is that a Trunnion Ball Valve fits the definition at least as well as this valve and has resilient, spring-loaded seats.
I'm pretty sure that a large proportion of valve choices are based on policies instead of an analysis of the problem being solved. Far too many companies would rather have a policy than allow a decision. In that kind of environment this sort of discussion is just noise into the wind.
The large pressure drop makes them ideal for throttling and blowdown apps.
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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)
For the plug valves here shown the clearance is not fully symmetrical. There is no reduction on the vertical axis - but a larger reduction on the horz. axis compared to a ball valve (see drawing on page A3 in the catalouge). So im not sure its that bad. As i said i know a nomber of installations where they have been retrofitted because they have the standard size.
I think we have been over the DBB issues before ;-) and we apparently do not agree...
Try looking at MTS plug valves from Spain. These are lined valves. Usually used in desalination plants up to 100bar rating. Come with butt weld ends and made in super duplex stainless steel.
