RE: pressure test thoughts

from JOhn Luc.
n general they cannot be re-rated (FEA has been used by some for this but frankly I am a strong dissenter in such practices... Dr. Bickfords' texts on bolted joints really makes you concerned about bolted joints and their assembly) and often time form the weak link, sometimes they are replaced by the class flange that is needed.

For an off the shelf piping component like flanges (probably those made in USA) as long as the PT rating has not exceeded, its properly fitted, material is compatible with the service, correctly tightened and the use of right gasket and bolts/nuts has been observed then I guess you'll be OK. In few cases, some will still leaked. Probably the reason why Maintenance are still around and so is TDW. Piping and components nearly makes up 30% of the capital cost - thats a big chunk of capital investment. Fixing leaks are big part of maintenance expense most especially if the plants are a bit old and being pushed to produce above its rated capacity. The reason why in some cases we dont use'em like in high pressure steam line (butt welded joints except of course at the equipment interface/ orifice/meter lenght). In the USA its my understanding that some refinery are about half century old and very few if any are being built.

FEA can only do so much (well actually so little) and if the modeling is not done right then leak continue. They're also made up by pipefitter who are overworked, bought by a buyer at lowest cost (what quality?), located at places thats too tight you could hardly move, etc, etc. Received on Mon Sep 12 00:15:00 2005