Re: Teflon tape
Posted by dick on January 27, 19100 at 10:23:56:
In response to Re: Teflon tape
I'm not terry, but i'll throw my two cent in anyway. Teflon tape is great stuff for filling in gaps and making pipe threads seal. that doesn't change with stainless. Teflon tape is a fairly good lubricant for pipe threads, again that doesn't change for stainless BUT: You may need something more than a fairly good lubricant especialy if you are screwing together two stainless pieces. Stainless has a tendency to gall under high loads, and pipe threads put a high point load on every minor iregularity in the threads.
Depending on conditions of assembly and use and the specific stainless alloys and heat treatment:
In addition to the teflon tape you may need too:
1: moly spray both parts before teflon tape
2: coat with high moly /graphite content grease after teflon tape.
3: bead blast both male and female threads.

4: copper plate one or both threads.
5: Ion nitride one (usualy male) thread.

I have had to do all of the above for different projects. And regardles of how much care is taken, there were still some galling problems.

For off the shelf 305 or 316 stainless pipe and fittings used in short term testing at under 350 deg and 5000 psi, moly spray, teflon tape, and a little grease seem to keep galling problems to a minimum.

When we test at higher temperatures and pressures we have to either take more precautions or accept that a lot of the fittings will be thrown away after the test.


: Terry,

: There is some debate where I work about wether teflon should be used on stainless steel pipe thread or not. What do you think?

:
: Thanks, Bill




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