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Old 06-07-2007, 11:15 AM
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Sealing NPT fuel fittings

I'm installing an electric fuel pump with 1/4" NPT fittings. The directions say that if I use any sealant on the threads it will break the pump. How do I get NPT to seal without any dope on the threads? They refer to it as "dry-seal" fittings and if I use any teflon tape or paste it will void the warranty.

Its a marine pump going in a boat, so it absolutely can't leak or *boom*
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Old 06-07-2007, 11:25 AM
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The problem with tape voiding the warranty is that people use too much of it and it gets into the pump. If the fittings have enough thread engagement you should need no tape or sealer.

Vince
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Old 06-07-2007, 11:26 AM
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Hmm, not sure how it would break the pump. On a fuel pump with pipe fittings, I'd use teflon tape. Any liquid type sealer would most likely dissolve when the gas hits it. You could try it dry and see what happens, but the fittings will need to be pretty tight! (could break it too!)

Mark
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Old 06-07-2007, 11:47 AM
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I never heard of dryseal fittings so, I googled up this description.

NPTF dryseal fittings : Dryseal threads have roots that are more truncated than the crests, so an interference fit causes the roots to crush the crests of the mating threads. The theory behind this thread concept is that when the crest, root and flank of the threads are engaged, there is always mating contact, creating a seal without lubrication. Unfortunately, due to inherent properties of some metals such as carbon steel and stainless steel, galling will occur in this type of seal without lubrication, making initial installation difficult and remake impossible.

Maybe it's the marine application but I never take a chance on pipe threads sealing without teflon tape. If it's done correctly teflon is fine. Here is the proper taping procedure from the same web page


The following factors are important to consider when using tape to lubricate or fill voids in the thread crest, root and flanks:

When applying tape to the threads, two to three wraps of the male threads is sufficient with most tapes.

Never wrap tape over the end of the first thread, as tape will eventually splinter and enter into the fluid handling system, which may damage the internals of system components.

Wrap tape in a clockwise direction as you are viewing the thread from the end of the fitting. If not wrapped in the correct direction, the tape will not properly lubricate, potentially causing leaks.

Cut off excess tape and draw the free end of the tape around the threads tautly to conform to the thread. Then, press on the tape firmly with thumb and index finger at the overlay point. If the crests of the threads protrude through the tape, galling may occur, so additional tape will be required.

That's pretty much how I do it and never had a problem at work or home.
What is the manufactuer of the pump, just curious. Ed.
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Old 06-07-2007, 12:10 PM
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Try A Drop Of Oil On The Threads For Lubrication
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Old 06-07-2007, 05:58 PM
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Thanks for all the info. Sounds like I have to ruin the fittings if I use it without teflon in the hopes that it might seal

I'll give it a shot with just some oil or anti seize first and see how it works.
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Old 06-08-2007, 09:48 AM
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Quote:
Originally Posted by curtis73
I'm installing an electric fuel pump with 1/4" NPT fittings. The directions say that if I use any sealant on the threads it will break the pump. How do I get NPT to seal without any dope on the threads? They refer to it as "dry-seal" fittings and if I use any teflon tape or paste it will void the warranty.

Its a marine pump going in a boat, so it absolutely can't leak or *boom*
Is the part of the pump that the fitting screws into plastic or metal? If it's plastic, the plastic itself will deform enough to seal the threads. Teflon tape will reduce the friction and can lead to over torquing of the fitting, which will split the plastic.
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Old 06-08-2007, 10:00 AM
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i used a holley fuel pump (mechanical) with 3/8 NPT fittings and didnt use any teflon tape of sealant or anything and it is working just fine. i just got them really tight! there is no leaks at all !!! idk maybe try it???
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