Gasket SIGMA value explanation please

[timo888]

I would be grateful if one of our illustrious, industrious engineers could please take a moment to explain the meaning and relevance of the Sigma value of a boiler or flange gasket?

Regards
Timo

[egall]

I'm not a materials engineer, and it's been a while since I took the requisite intro Materials Engineering course, but my recollection is that sigma was modulus of elasticity - which indicates the degree that something deforms from a given stress.

Hopefully this is what you're talking about, and I'm not nerding it up in the completely wrong direction.

[egall]

Whoops, my text proved me wrong - modulus of elasticity says that stress and strain are proportional. Sigma is shown as engineering stress. If you have a link to point out what you're referring to, I'd be happy to try and confuse everyone more!

Elliott

[timo888]

The gasket for the boiler is specified as 155x120 Sigma 511.
Regards
Timo

[erics]

BTW, Flexitallic is a very reputable mfg.

http://www.flexitallic.com/pro_sigma_511.html

[timo888]

BTW, Flexitallic is a very reputable mfg.

http://www.flexitallic.com/pro_sigma_511.html

Thanks. If their distributors have my size I will order some in "fawn"
Regards
Timo

P.S. Which gives me a chance to tell an of-topic but funny (in a Reader's Digest sort of way) story. If you've ever been to a boys soccer game, middle-school or high-school, you may have noted that the referees are very simple-minded when it comes to color. If the jerseys of the opposing teams are black and silver, say, they will call the silver team "white". Or they may call orange "red". At a recent tournament, I was field marshal for a game played by 13-year-old girls. It was strange to hear soccer-moms yelling from the sidelines, "Go, teal!"

[bill]

Timo,
I think the use of 'sigma' in this case is just marketing hype and has nothing to do with gaskets. They're probably trying to build on the use of sigma as as measure of quality. Sigma is the symbol for standard deviation in statistical quality control with 'six sigma' meaning a process under very tight quality control. Or maybe the first-born daughter of the company founder was named Sigma? Who knows?
Bill

[timo888]

I had assumed sigma specified some value analogous to "duro" for elastomers. Did not suspect it had to do with branding.

Regards
Timo