Weknow that at moderate bolt load very high gasket pressure can be generated in RTJ gasket and reliable seal can be easily attained for high pressure piping.

But, both flange grooves & oval/octagonal gaskets are costly and oval gasket can be only used once, octagonal ones a few more times.

People have used spiral wound gaskets at temperature upto 1000C and pressure upto 350 bar.

My question is for moderate pressure piping if one uses spiral wound gaskets with proper bolt stress, is it a less reliable seal against leak compared to RTJ ?

regards,

sam

One of the most critical issues surronding the performance of bolted joints is their assembly... This issue is seldom adequately adressed by the designer. The AISC code provides much more specific guidance and requirements concerning assembly than do the ASME DESIGN codes.

The ASME PCC codes attempt to adress this issue.

"My question is for moderate pressure piping if one uses spiral wound gaskets with proper bolt stress, is it a less reliable seal against leak compared to RTJ ?" Yes both require consistent precise assembly.

Many refinery operating companies use RTJ flange for steam & hydrogen service above 600 psig & hydrocarbon above class 600 & for all other services class 900 and higher. But, the concern is that RTJ is expensive, when done in field and requires flexibility in connecting piping for gasket installation & removal.

regards,

sam

"Standard" RF flanges and 1/8" thick gaskets became standard for that reason: low leakage, relatively inexpensive, and ease of use combined with "reliable " installation in the field. Today, as experienced hands retire from all industries - to be all too often replaced with youngsters NOT "good" with their hands practiced by years of "backyard mechanics" - but who've only played Nintendo and video games - the simple installation of standard gaskets is going to become even more important.

A RF flange lets you pull the valve or flange away from the other face easily and quickly, and the size of the standard gasket lets you hold the gasket in place with the lower (loosened) bolts across the bottom of the flange as the gasket slips back in place from above. So the gasket isn't too likely to get misaligned and block flow or leak.

My recommendation? Whenever you can, use the simpler installation. The more complex gasket & face (grooved face or single use gaskets) are more likely get screwed up by the field up on a scaffolding or in a manlift. What's more likely? A twisted, deformed or scarred gasket getting "reused" because nobody will know? Or the guy who screwed up going back down to grade level, walking back to the warehouse, filling out the forms again (accepting blame for the wasted first gasket!) walking back to the site, back in the man-lift, and back to the face of the flange?

Thank You,Sir. I, too, vote for simplicity wherever I can.

It can be easy to buy a complex object, but very difficult & costly to maintain. Very often we don't look at the big picture with a holistic life cycle cost(LCC) approach! Just for example, initial acquisition cost of a chemical processing pump can be as low as 5% of life cycle cost of the installation.

regards,

sam