Natural Gas Gasket Type Recommendations??? 2

[UtilityLouie]

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#.

Recommendations? Can I make the flexitallic gaskets work?

What should I specify for future?

Thanks!

 

[dtn6770]

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.

 

[dcasto]

If a flexitallic is not sealing at the low pressures you are quoting, the operator has an installation problem. I suggest you get on Flexitallics web site and download their recommend installation methods.

At 50# or even 150#, a fiber gasket is fine for clean natural gas.

 

[STYMIEDPIPER]

I am currently reviewing piping specifications for a fortune 500 company
The specification depicts flexitallic stnls stl insert gasket for natural gas service

 

[dcasto]

It's a wonder they get to stay a fortune 500 if they continue to over specify, oh well.....

 

[zdas04]

I've used flexitallic gaskets in every service from vacuum up to thousands of pounds. They're forgiving, don't require gasket compound, and are easily installed (hard to install incorrectly).

The only reason I can think of not to use them is in situations where the spacing is critical (like the side flange on an ejector) and the design calls for some other kind of gasket. If the spacing is not critical I'll always use flexitallic gaskets.

David

 

[ApC2Kp]

UtilityLouie,

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.

 

[dcasto]

We have a wall full of every flexitallic we use as spares, and a little itty bitty corner for fiber. We use the fiber on low pressure and specialty areas, it's nice sometimes to ball peen out a gasket, and cheep too.

 

[nosabe]

Why does the gas supplier recommends fiber gaskets? as an experienced oil refinery maintenance man I recommend to go with flex gaskets for this application,they are very reliable and maintenance friendly

 

[tothepoint]

In a class 150 piping system, your problem with spiral wound gaskets is more than likely low bolt load. There are many sizes of class 150 flanges (especially NPS 3, 8 and 12)where even A193-B7 bolts will not develop sufficient compressive stress on a SW gasket- especially if it has an inner ring.

If your spec allows, switch to a non-asbestos fiber gasket. Make sure to check the binder to make sure it's compatible- Nitrile binder would be best.