The pipe spec I'm using calls our Flexitallic (sp?) spiral wound gaskets for natural gas piping systems.

The gas supplier recommends using fiber gaskets.  I have no problem with following the supplier's recommendations, but we have an existing system with the spiral wound gaskets installed that's been in service about 5 years.  There has been some reports of flanges leaking, but there are no NDE reports on the system, so I don't know how well the system was installed.

There are two higher pressure systems --- one at 50# the other at 150#.

Spiral wound (316 or 304 w/graphite filler) is the gasket of choice at 3 facilities I'm familiar (2 refineries & 1 natural gas compressor packager).  It should work fine.  Specifically what fiber gasket is the gas supplier recommending?

Are you the spec "owner?"  If not, don't just deviate without getting approval.

Most all refinery and chemical plants would use the spiral wound gasket - it is fire resistant.  The former asbestos sheet gaskets were also fire resistant.  Most of the fiber gaskets with elastomer binder will not be fire resistant.

Another item to be concerned with the fiber gasket versus spiral wound gasket would be the pipe flange and the bolt material.  Steel flanges are able to compress either gasket.  If there are cast iron plug valves, the cast iron has concerns of low strength.  Fiber sheet gaskets would seal with low bolt loads.  Spiral wound gaskets require more bolt loading that could crack cast iron flanges.  A controlled bolt torquing procedure with A307 B bolting might possibly seal a spiral wound gasket without cracking cast iron flanges, but is it worth the risk? Most refineries don't allow A307 B bolting in the plant, they are afraid low strength bolting would be installed where high strength B7 alloy bolts are required,  have a flange joint failure, and a fire.

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