Stainless windings give strength and springback while graphite or PTFE filler between them does the sealing. A carbon steel outer ring centers the gasket inside the bolts and stops it being crushed too far, and an inner ring protects the windings from buckling into the bore. Color codes on the outer ring show winding metal and filler, so a fitter can read the gasket at a glance.
Grab four 6 inch 300 spiral wound gaskets, 316 and graphite, with inner rings, they're the green and gray ones.
Also heard as
- spiral wound
- SWG
- spiral
Related terms
Raised face
A flange facing where the gasket surface stands slightly proud of the bolt circle area, concentrating gasket load.
RTJ
Ring type joint: a flange face with a machined groove that holds a solid metal ring gasket for high pressure.
Pressure class
The standardized rating step, such as 150, 300 or 600, that sets a valve or flange's allowable pressure at each temperature.
Hot bolting
Replacing or retorquing flange bolts one at a time while the line stays in service.