Gasket questions
Gasket questions
(OP)
Hi all,
I recently started to work with maintenance at a refinery and I have a few thoghts and questions about gaskets.
1. Why does the outer ring of a spiral wound gasket (with inner and outer rings) sometimes get warped (like a satellite dish) when installed?
A manufacturer (not the same one who made the warped gaskets) told me that it had been wound too tight during manufacture... But I was thinking that perhaps it's more because the wound part needs to be compressed when installed, but it can't expand sideways because the inner and outer rings are stiff, so the outer ring gets deformed.
What do you think?
2. What type of glue is recommended to make a gasket with graphite tape stay in place during assembly of a heat exchanger? I have heard that most kinds of glue may cause problems with chlorides. And grease might make the gasket seal badly and might also damage the graphite when boiling/evaporating.
Is any of this true? What do you people use?
All ideas are greatly appreciated.
I recently started to work with maintenance at a refinery and I have a few thoghts and questions about gaskets.
1. Why does the outer ring of a spiral wound gasket (with inner and outer rings) sometimes get warped (like a satellite dish) when installed?
A manufacturer (not the same one who made the warped gaskets) told me that it had been wound too tight during manufacture... But I was thinking that perhaps it's more because the wound part needs to be compressed when installed, but it can't expand sideways because the inner and outer rings are stiff, so the outer ring gets deformed.
What do you think?
2. What type of glue is recommended to make a gasket with graphite tape stay in place during assembly of a heat exchanger? I have heard that most kinds of glue may cause problems with chlorides. And grease might make the gasket seal badly and might also damage the graphite when boiling/evaporating.
Is any of this true? What do you people use?
All ideas are greatly appreciated.





RE: Gasket questions
2) Use just enough masking tape to keep them in place.
RE: Gasket questions
For your first question I tend to doubt the "wound too tight" explanation. Does this happen at install or after being placed in service? What sizes of gaskets are involved?
Regards,
Mike
RE: Gasket questions
Mechanical damage as you describe with spiral wound gaskets in normally caused by the gasket being a little too large and the threads of fastener picking the edge of the gasket. The gasket needs a 1/16" diametrical clearance to alleviate this problem.
One other cause, rare, is that the flange is cupping due to fastener overload or the wrong style of gasket for the application.
As far a graphite tape or HE gaskets we use a tack adhesive to temporary hold the material.
Be very careful with masking tape or especially cloth tape around gaskets use in high temperature service. Make sure no tape crosses the gasket in the radial direction.
RE: Gasket questions
SnTMan,
The outer ring of the gasket gets deformed during installation, that is before start-up. I've seen it in sizes around 10", but it is possible that it happens on smaller and larger gaskets too.
Unclesyd,
It is quite possible that the fasteners are in the way. I haven't thought about this possibility before.
Which tack adhesive do you use?
RE: Gasket questions
RE: Gasket questions
Flexitallic, for one, has dimensional charts for the various sizes and ratings for B16.5 flanges. You might get your hands on one if you don't already have it and check things out.
Regards,
Mike
RE: Gasket questions
Thanks. However, I am quite sure that we use correct gaskets, both size and rating. But, maybe a vary low percentage of gaskets might have slightly larger outer ring from manufacture? Or they may have got compressed a little too much? Another possibility is that the two flanges were not completely centered or that the gasket was installed slightly off center.
RE: Gasket questions
In an emergency we have even send the gaskets to the sheet metal shop to punch segments on the periphery to accommodate the studs. For years the shop kept templates to accommodate all our major flanges.
RE: Gasket questions
The first time I saw this I consulted with flange and gasket experts. One of them told me it was normal and not to worry about it. The other one told me it was a defective gasket and it must be replaced. I replaced the gasket with a new one from a different source and it did the same thing. Since then, I have seen it many times and have started listening to the first expert. I don't worry about it. I have never had a leak or any other problem from one of these cupped rings. I know of examples running in our plant today in 400 psi steam, 1400 psi hydrogen, high pressure water, etc. Just make certain you have the right gasket, the right studs and use a proper tightening method (tightening order and torque) and you should have no problems.
Johnny Pellin
RE: Gasket questions
Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website: www.oil-gas-consulting.com
RE: Gasket questions
http://www.boltscience.com/pages/gasket.htm
RE: Gasket questions
Regards, Boser