Sealant on Remote Oil Lines?

[John F.]

The DD 8.2s in Crows Nest have remote oil filters. I pulled the old (at least 18 years) lines running from the block to the cooler and filters on the starboard motor, and had new ones made. Its time to reinstall.

At least one of the lines looked like it had thread sealant or something on it. Should I use sealant? Thread tape or liquid? Any suggestions?

[Carl]

Permatex High Temp Thread Sealant on most everything that should seal.

NPT's I still like Teflon Tape

[Rawleigh]

It depends on the fitting type. NPT - yes. AN, JC, or flat faced oring - no

[Bruce]

Just for the general knowledge, npt is national pipe thread. It is a tapered thread and depends on the resistance of the male against female to seal. Always use a sealant or Teflon tape.

If you have a straight or running thread it will use a gasket, oring, or seat against a internal seat of some kind.

[EarleyBird]

Ah,something I might know a little bit about,especially after spending 30 years in Steamship Enginerooms..20 as Chief Engineer. Use a reliable thread sealant. I despise Teflon tape. Teflon tape if used/ wrapped excessively will cut threads. Oates “pipe sealant”is my choice. 4oz. Containerwith a brush all you need for any thread on your boat. Wipe off excess after tightening. Owning a 31, for 33 years on her 4th set of motors helps also.

[John F.]

Thanks for all the advice. These are the oil lines, and I don't know what these fittings are called. And yeah, I'll clean up the threads better before reassembly.

[EarleyBird]

Sir, that is a JIC fitting which requires no sealant. The seating/sealing surfaces are the angled surfaces and should be clean before assembly. Make sure there are no grooves, scratches etc. on these surfaces. Any sealant of any type could compromise a tight seal if gotten on those faces. If worn, replace. Good Luck. Pipe dope on NPT threads which are tapered, anti-seize on Machine threads Standard or Metric, makes life easier down the road.

[Bruce]

Many people do not like Teflon tape. I've seen it where it looks like a wad of toilet paper.

I've also seen thread sealer in injectors, pumps and such.

There is a proper way to use both. But we all have our go to.

[John F.]

OK. Clean everything up really good and no sealant. Thanks again.

[coolair]

on a side note. I always thought Tefgel was a good alternative but harder to come by.

Not to high jack the post. But whats the best to use for fuel lines?

I know normal teflon tape is not rated for natural gas, there is gray teflon tape.

[Carl]

Tapered fuel lines should be NPTF (National Pipe Taper Fuel) and are Dryseal threads.
As the name implies they are made to be installed without sealant, dope, lube or teflon tape.


NPT mating threads have slight voids between the two surfaces for sealing material to fill and pack in creating the seal.

NPTF mating threads are much closer to a perfect fit. The material itself deforms slightly to create a mechanical seal on both the thread flanks and diameter. They are made to be able to hold greater pressures without leaking.

[coolair]

learn something new everyday. Didnt know there was a NPTF fitting. I am guessing the fittings I have used are just NPT.

[Carl]

I make them both, aside from gauging them I have a tough time telling them apart when both are machined.