flange gasket sealing

[QCnTraining]

Hi everyone, in the past 6 months I've branched out from a post weld heat treat technician into a QC inspector. This past week I've been inspecting flanges for proper parts, assembly and bolt torque. I have one in question right now where as the outer edge of the gasket is raised for approximately 120 degrees of the gasket. This is a result of the gasket being in contact with the studs and as the studs were tightened, the gasket was pulled up the treads. Will this affect the sealing ability of the gasket?

18" line
Inconel 718 studs and nuts, torqued to 1267 Nm
Thermiculite gasket

thank you

 

[ricklts]

QCnTraining

If this gasket has an outer metal ring, this ain't good. The gasket sealing surface will be in contact with the flange faces, but the 'lifting' of the outer ring will tend to separate the windings from the ring, allowing for additional compression distortion of the gasket, reducing it's ability to withstand internal pressure. If not outer solid metal ring, same thing, only more so.

A properly made SWG with an outer ring will tend to push the studs to the outer side of the bolt hole, but it shouldn't be bound up in the threads.

Try looking at one of the manufacturer's technical handbooks - I use both Lamons and Flexitallic's.

Good luck

 

[geesamand]

"Thermiculite" is a product line and is not specific enough to give you an answer.

I agree with ricklts - unless the gasket easily bends and deforms under finger pressure just like you see in the assembled example, then it's likely that there are undesirable stresses in the gasket. Consult Engineering for more detailed acceptance criteria in that case. I should hope you don't have to work out such questions by yourself.