spiral-wound gaskets

[farhad2474]

Please some body tells me ,it is necessary a spiral wound gasket have a inner ring. Our piping design pressure is 54 Bar and temp is 200 C.
Thank you
Farhad

 

[unclesyd]

No, it's not absolutely necessary to have an inner ring, but it's a very good idea.

First off it prevents in spiral buckling of the gasket spirals the most common listing for spiral wound gasket failure.

In some cases it fills the void where a spiral wound gasket without same would leave a void. We had a requirement for all spiral wounds gaskets to have have the inner ring which was essential in our polymer area to mitigate the formation of a Gel, highly cross linked polymer.

There are a couple other benefits like it helps when someone hangs the gasket on a peg and helps prevent the loss of filler in service.

 

[farhad2474]

thank you so much unclesyd
farhad

 

[ScottAO]

Another good reason to have the inner ring - If this is in a pipeline that is pigged, - the pig can snag the inner winding of gasket (if it doesn't have the inner ring) and literally pull the whole winding though the pipeline. Then eventually you get a ball of wire coming out the other end of the pipeline, - not a nice situation (not knowing where it came from).

 

[rneill]

The current version of ASME B16.20 requires that spiral wound gaskets have an inner ring unless otherwise specified by the Purchaser.

Based on published papers, buckling problems seem to be related to a number of variables including: pipe size, pressure, temperature, and gasket filler material.

In your OP, you provided the pressure and temperature but not information on the pipe size and filler material so it would be difficult to provide a full assessment (which is probably beyond the scope of these forums anyway) but in general, for the small extra cost, I typically just go with the inner rings.

 

[StevenHPerry]

rneill left out installation in causes of buckling (if we're talking about the same "buckling").

Especially on small bore flanges, fitters have a tendency to tighten the joint to the point where the inner windings separate, are "squished" into the flow path, and will give off flecks, bits, or actually unwind.

Maybe I'm over-specifying and over-spending on gaskets to compensate for incorrect practices in the field, but I think inner rings save money in the long run.

- Steve Perry