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-   -   LPG plumbing - teflon tape? (http://www.sailnet.com/forums/gear-maintenance/80352-lpg-plumbing-teflon-tape.html)

MarkSF 11-01-2011 12:33 PM

LPG plumbing - teflon tape?
 
The day is nearly here to re-commission the LPG system.

I have new tanks that aren't rusted out, a new Trident regulator with pressure gauges for leak checking, the locker has been painted inside with bilgekote, and I have a new solenoid valve / leak detector unit.

The valve will go in the locker just after the regulator, and the leak detector sensor will go in the bilge.

There's an existing pre-made hose to the locker which I'm going to re-use.

So all I need to do is fit the solenoid valve to the regulator, and the hose to the valve. Is teflon tape still the thing? I ask because I've heard of better liquid sealants that set.

zboss 11-01-2011 02:15 PM

Use pipe dope for a permanent attachment and tape for semi-permanent.

Oh... also... if you use tape be sure to use the higher double thickness grade (yellow not white tape).

MarkSF 11-01-2011 02:36 PM

I looked at Loctite and they do 561 and 567, both are semi-setting compounds (can be dismantled again) that are claimed to replace tape and are approved for LPG use up to 150PSI. Should be fine for my low pressure side?

Has anyone used them?

hellosailor 11-01-2011 03:33 PM

Mark, I think you'd be fine either way. With teflon tape ust don't wrap the very end of the thread, so no tape slivers get sliced off and go downstream into the regulator or jets. With LocTite, you probably have to degrease the threads for best results, and of course it actually has a shelf life--you'll throw out most of the bottle two(?) years from now, or it won't seal properly.

But either one will work.

overbored 11-01-2011 03:45 PM

567 best stuff. good for years in the tube. I use it a lot. better then tape. can be undone. small tube is about $5 can be used for all plumbing on the boat even diesel.

JohnRPollard 11-01-2011 06:59 PM

Hi Mark,

Sounds like a good project you've got going there -- nice upgrade!

The answer to your question depends in part on what kind of fittings you are using. Many of the connections now used in propane systems have flanges that are sealed by compression or o-rings. In those cases, it's not necessary to use tape or other.

If compression flanges or o-rings are absent, and it's just threads doing the connecting, I've had very good luck with standard teflon tape. Make sure to wrap it in the same direction that the threads will be turned in. Otherwise, it will bind up as you screw the two pieces together. Also, be careful to make sure the tape doesn't make a flap over the opening of the hose -- I once spent a few hours troubleshooting a lack of flow through only to discover the tape was blocking the orifice.

Remember to always pressure test the system after making these connections, and on a regular basis throughout the season. Good luck!

deniseO30 11-01-2011 07:15 PM

Just a note about pipe threads, "NPT" The dope or tape helps fill microscopic gaps on the edges and valleys of the thread, NPT threads are tapered, the more you tighten the tighter they get, EXCEPT, you can go too far and stretch the receiving fitting, or split it (rare occurrence) If you have ever seen old dies cut threads (My dad was cheap sob plumber) the threads will be ragged, near impossible to seal, if you buy pipe nipples make sure the threads are smooth if they feel rough, don't use them.

funjohnson 11-01-2011 10:47 PM

When I was switching over the LPG, I was given a tube of Permatex 2A gasket by the supplier of the new stove orifices.


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