Why would one use a lubricated plug valve over a ball valve for shutoff in natural gas service? Is it a temperature issue if the valve is located outdoors?Is there a fire safety issue?A lot of people have opinions on this, I'll give you mine: I cannot find a single place where I would prefer a plug valve to a ball valve.The problem I have with "lubricated" plug valves is that they don't get lubricated in the field (plants may be different, but I don't work in plants) and after a few months or years they can become impossible to operate. I've seen people try to operate them with a length of pipe tied to a rubber-tired hoe and not been able to budge them.With recommended maintenance, maybe they would have a proper place in the world, but field maintenance on small valves is spotty to non-existent.If you ignore a ball valve for a decade it will still most likely operate and there is a reasonable chance that it will hold pressure. Not so with a plug valve. Principally I agree with zdas04, but the real valve selection should be based on the full technical appplication set of data for any valve and service, for instance minimum pressure for and after, temperature (medium and surrounding), flow, purity and full descroption of fluid, on/off or regulation, manual or mechanical operated (with details), any design or safety requirements, any material or sertificate requirements, any material preferences, operation time and details, expected or required lifetime and operation dependabillity, price/lifetime cost, references for similar use, etc, etc, etc....And then you might well end up with a standard ball valve suitable for the service, but mind you, there are alternative constructions. But greased plugvalve? No!

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