Pipe Tape vs Pipe Dope in High Pressure Hydraulics

[downsizingnow48]

When I added or changed quick connects they were all female NPT either 3/8 or 1/2. Need to use a male NPT-to-JIC fitting. I use Loctite 545 for that.

 

[aczlan]

What do all own that you use anything on your hydraulic fittings?

I have four tractors, plus a few other things with close to a hundred hoses combined on all of them, and every single one of them DO NOT use anything other then an o ring at the end to seal them. A lot of them don't even have that.

Are you talking about tractors? or something else? That might be why I'm so confused.

Oring or flare (think JIC) fittings don't need tape or pipe dope. NPT fittings generally do.

Aaron Z

 

[Ford850]

My Case IH remote kit specified Loctite 567 for the NPT's. I thought it was unusual for instructions to give a brand and product to use.

 

[woodlandfarms]

So as the OP I am going to ask something even more stupid. Is there a correct way to apply Pipe Dope? I know how to wrap pipe tape (and I am of the school less is more so no more than 2 wraps - but I get there is an argument about this).

 

[woodlandfarms]

Oh, and I just read an article about the difference between Loctite 545 and 567 as both were quoted. 567 is pipe dope, can be used immediately - Has Teflon. 545 is more of a glue, and needs 24 hours to cure but is wrenchable (not like loctite Red).

They suggest a coat around the fitting 2 to 3 threads down.

 

[Ford850]

You don't need much. The small Permatex or Loctite tubes produce a small bead. I think the instruction say something like "skip the first threads and apply to only 3/4 of a thread". In other words, very sparingly. The threads should mesh very close leaving very little room anyway, and you just want a thin film smeared in the threads as you tighten them.
I know threads are supposed to seal on their own, and pipe dope is a lube, but the high temp and hydraulic type is called sealant and per the instructions there is a set time before using.

 

[bigdeano]

NPT threads require a sealant because they have clearance between root and crest of thread.

NPTF (national pipe thread fuel) threads are supposed to dry seal because they have interference between root and crest.

On clean fittings I use blue Loktite 242 because I have a large bottle and it can be disassembled easily and never leaks if given time to harden.

On oily threads I use tape being careful not to let it get inside the system.

 

[CJONE]

Every power unit we build where there is NPT fittings will have both ptfe dope and Unasco pink tape or you may be looking for work somewhere else. Learned a couple of lessons quick when we were starting out with leaks with just dope. We had a couple of power units built where the customers employees helped me and refused to use tape, one unit cost them a whole weekend of teardown and using tape. [I was not there to help them as I told them once, so it was their choice] Another was 3 weeks ago, 3" suction line off of a 250 gallon res. Customer was helping, didn't use tape, fitting leaked, tightening didn't help, [imagine that!] Anyway correct use of tape, there will be no issue and no leaks. Incorrect use, ya you will have a mess. CJ

 

[300UGUY]

I've used the Loctite 545. Great stuff, but not cheap.

 

[Deere Dude]

Starting out as a good sized pipe-fitter apprentice, one journeymen rode me about tightening pipe fittings to hard and for using 242 or Teflon paste on air, oil, grease and water lines. He whined about not being able to get them apart. Eventually I caved in and started using tape and didn't crank the pipes in quite as much on this fairly big air job with a bunch of 2" pipe and lots of fittings.

The test came at the end of this few week project when I turned the air on. It sounded like a rattle snake pit with so much hissing. Needless to say I had to redo almost every joint only this time I used at least paste but 242 was my favorite to make it leak proof.