Grunff wrote in message ...
Stanley Spanner wrote:

What's pukka for jointing fittings (compression and straight threads)
for heating oil? I heard that PTFE tape was not OK. My Purimachos
green stuff says it's OK for oil but I wonder if it'd be that
effective - I don't think it gets thick and sticky over time like the
white stuff.

Compression fittings (all of them, oil, air, water) are exactly
that - they work by compressing metal against metal. The olive
is the thing that makes the seal. There is no need for *any*
goop or tape.

In theory :-)

I usually put some green stuff on even new joints, and always on old
ones - belt & braces.

If you make a compression fitting and it leaks, it's because
either you didn't make it right, or you haven't tightened it enough.

- or there's [been] a bit of grit in the joint, which has scored the
metal surfaces so they don't seal perfectly. (That's with those of us
who don't plumb in clean-room conditions :-)

Huge wrote:

If you make a compression fitting and it leaks, it's because
either you didn't make it right, or you haven't tightened it enough.


.... or too much!

Good point, and it's more easily done with 8mm and 10mm fittings.

... and soft-as-butter fully annealed table Y tube grrr

All my oil compression fittings were made without any joining
compound or tape, and none have leaked.

As for tapers, then PTFE tape is absolutely fine.

What about parallel threads? (The filters and butterfly valves all
have these.)

Normally I'd use PTFE: the panel at Plumb Center reckoned that was out
for oil; but I've just checked Treloar who says "Petroleum resisting
compounds and PTFE tapes which remain slightly plastic make the most
satisfactory joints; hemp and hard-setting jointing compounds should
be avoided". I assume he means PTFE tapes in general, not 'Petroleum
resisting PTFE tapes' as I understand PTFE is pretty inert stuff and I
doubt it would be bothered by heating oil.

OTOH he also says soft soldered joints are out, which means I've got
more &%^* compression joints to make on soft tube :-(

cheers

Stan the Span