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.

Actually, the problem I always have is people throttling the purge outlet valve and the procedures I write strongly warn against that.  Of course you have to throttle the supply valve, I don't know why that left my tired brain.

I just reviewed the last pigging procedure I wrote and I have a purge-the-barrel step, so obviously I require throttling there too.  After the barrel is purged, I want each valve that has to be operated to be fully open or fully shut (although on the launcher, the last valve to be operated prior to the pig launching is the side valve and I say "slowly shut the side valve, if the pig passes the pig signal prior to the valve being fully shut, it can be reopened without fully shutting it" so maybe that is a throttle as well.

I don't see any difference in throttling a plug valve and a ball valve.  Both have very non-linear throttling characteristics and the ball valve tends to move easier.  If I was going to specify a preference, I call out a globe valve for thro 

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