properties of rubbers.. 1

[ramakant]

i have an equipment where i have to use rubber as gasket.
inside atmosphere is nitric acid fumes. and temperature is ambient and vacuum of 2 m water column is maintained in side.

my problem is that i have to calcutate bolt loads required to get a prefect seal. please suggest me the type of rubber i can use.

will nitrile rubber do? The gasket has to be in position for more than 5 years.

if some body can help me in getting the properties of rubbers (shore hardness 'A' from 5 to 75) i.e. percent compression vs stress generated in...


Thanks and regards
Ramakant

 

[Metalguy]

I think you can forget about just about all elastomers for this application-use a solid teflon gasket instead.

 

[ramakant]

thanks Metalguy for the reply.
can you help me in getting properties of teflon gasket and other elastomers (percent compression wise ...)

is teflon stable in radioactive atmosphere.


ramakant

 

[Metalguy]

Teflon doesn't resist compression-set too well, and it is just about the very worst material for rad. resistance. Interesting that such a chemically-resistant material is unravelled so easily by radiation. If your rad. dose is over ~100,000R, Teflon breaks down to release F--not usually good.

There may be another way for you-use graphite-filled spiral-wound gaskets. Flexitallic and others make them. Reg. ol' 304 SS should be OK for the rest of the gasket. If you can spec. the flange design, get the gasket to compress ~25-35% of it's orig. thickness, and then have the flange go solid metal-to-metal. These gaskets are also avail. with a solid metal flat area of the correct final gasket thickness, so you can tighten the bolts "way up" and not crush the sealing part.

The 5 year req. is the toughest part for rubber gaskets. My books indicate that only Viton will resist HNO3, but there are newer comps. that may also resist it (Kalrez?).

 

[arto]

Look in the ASME Code Sec VIII Div 1 Appendix 2 for flange/gasket seating design.
The Garlock Gasket Catalog has a lot of info too:

http://www.garlock-inc.com/upload/catalogs/Engineered_Gasketing_Catalog.pdf

 

[niblick]

ramakant:

try

http://www.parker.com/o-ring

they should be able to help you

good luck

regards,

niblick