Light Aircraft Association

Any recommendations for the most suitable sealant for alum. NPT pipe thread brake fittings?

There seem to be dozens of Loctite and Permatex products, but which might be best for my application?

I know that, ideally, sealant shouldn't be needed, but more viewing of the web has sown doubts about that and some very convincing arguments are made suggesting that a (modern) sealant is indeed needed and will ensure a good seal, without arm wrestling the fittings and overstressing them in an attempt to stop them leaking.

Any help would be appreciated!

Ian

Liquid PTFE.

Many thanks Bill and I'll give that a go!

Ian

Ian, I know you asked about hydraulics but for fuel fittings, LAS do this http://www.lasaero.com/site/products/ar ... =N01E57JV9 which I've found to be very effective.
regards, Mike

Thanks for the link Mike - that will be useful for certain threads on my carb; something similar was mentioned somewhere on the web.

Regards.

Ian

A licensed engineer warned me never to use PTFE tape in a fuel system; the fuel attacks the tape, turning it into sludge.

Harry Hopkins

Thanks Harry for the warning - I was aware of that but am sure it bears repeating.

I'm sure I saw an excellent video on the EAA Hints for Homebuilders a few weeks ago, in which Brian Carpenter clearly explained the reasoning behind using a thread sealer with AN pipe fittings, but I'm darned if I can find it now. Don't think he mentioned a specific sealer tho'., but wanted to check it again.

Regards.

Ian

Following on from the previous post & for the benefit of anyone who may find it useful, the item by the esteemed Brian Carpenter covering all things to do with pipe thread fittings was in the July 2015 Sport Aviation ( Page 2 of "The Experimenter" section. ). There is no video...
No specific sealant/ sealer is mentioned. I'll go for a suitable Loctite or Permatex product.

Ian

To be clear
Pure PTFE is totally resistant to all aircraft fuels and other liquids. PTFE thread sealing tape is totally resistant. The problem is that if not carefully applied parts of the PTFE tape could detach and cause a problem down stream, this mainly arises when a threaded joint is dismantled and rejoined a number of times and PTFE tape swarf is produced. This is applicable to other sealants as well of course.
My opinion is that PTFE tape is an excellent joint sealant with aluminium and other threads.

Liquid PTFE sealants are not pure PTFE and the PTFE particles are dispersed in a binder. This binder may well be dissolved by the fuel, rendering the sealant useless for our purposes.

The key question to ask is the sealant PURE PTFE.

Pat Thody

Many thanks Pat and I'll bear your comments in mind.

The item in Sport Aviation does also discuss the merits or otherwise of PTFE tape and warns against careless overuse/misuse of both tape and sealants.

Ian

There is a leakage path at the tip of the male thread through NPT fittings no matter how tight you screw them in, so a sealant is always necessary. Don't use PTFE tape on fuel lines as swarfe can clog things downline. I use Fuel Lube from LAS, but tere are probably suitable automotive products.

John

Many thanks John and I'll try both the Ez Turn(LAS) and maybe Wellseal, as alternatives to the Loctite/Permaseal offerings.
The Ez Turn is useful stuff, by the look of it, for lots of things, including my carb and Essex primer although it may not be best as a sealant in brake systems, perhaps. Wellseal may be better for that?
Having trawled through the archives etc at EAA and LAA I can't find much about brake or carburettor plumbing and set up, as it might apply to the likes of me, who may have little practical background in these matters!
Ian

Ian

Fuel Lube is good for fuel, oil, and brake fluid. The large tin from LAS would do a couple of 747s, get the 5oz tube as you only want to smear it on the fitting. Use a cocktail stick to apply it, scraping it level with the thread but no more. Sadly, I use new sticks as we don't drink cocktails any more and have no used ones. Cellulose thinners will clean it up but don't get the stuff on your clothes as it won't come off.

John

That sounds good, John and I guessed I maybe only need a teaspoonful. I'll follow your advice.

All suggestions are much appreciated & thanks again.

Ian