Sealing Compound to use on 1/8" engine fittings?

I would use Permatex High Performance thread sealant, sold at NAPA. It comes in a tube. A little pricey, but it comes well recommended by a mechanic friend of mine.

Tom

I don't use that tape much any more. It does nothing to prevent issues from dissimilar metals, it often is pushed completely out of the area where it needs to be, it shreds up in little fragments and winds up in an air stream or fluid, and it doesn't help seal. In fact, I'm not sure what it *does* do.

I like RectorSeal or maybe Rector's. Any good hardware store or plumbing supply place or even (shudder) Homo Depot or Lowe's should have it.

GWE

Thanks Tom and Grant. I will use a proper thread sealing compound.

i

IIRC teflon tape is primarily for plumbers. I've used it very successfully on plumbing fittings, especially metal-to-plastic fits on swimming pool stuff.

--RC

"Sometimes history doesn't repeat itself. It just yells 'can't you remember anything I've told you?' and lets fly with a club. -- John W. Cambell Jr.

For stuff like that I've been using plain old Permatex #2 gasket sealer as long as I can remember... with zero leaks. Most any auto parts store should carry it. It's good stuff to have around.

Beware of Permatex #1 if you ever plan to clean up around the site... I don't even allow #1 in my shop anymore... horrible stuff to scrape off. I guess there are some applications where it's preferable, but couldn't imagine what they'd be.

Good Luck!

Erik

Hi Temp silicone sealant never fails me.

I used to rebuild air compressors for heavy trucks and buses and earthmoving equipment. One of the more common reasons for compressor failure was silicone sealant. If it managed to get into the oil feed port when it was used on the 1/8" NPT fitting, it would break off and get into the small oil passages in the crank, shut off the oil, and blow the compressor to bits. We heard of entire $40,000 engines shot because the compressor shattered and the engine oil went overboard and starved the engine. Guys would use silicone on the mounting gasket, through which the oil drain port passes, and this would plug up and cause similar failure. After 17,000 compressors, this was my advice: Use Loctite 242 (blue stuff) on pipe fittings, and Permatex Hi-Tack gasket sealant on gaskets. Silicone belongs around bathtubs, or in non-critical automotive applications.

Dan

This is the same reason I WILL NOT use teflon tape on air lines on CNC machinery. Ive pulled too many solenoids apart where the shuttles or even drip lubricators were plugged off with a bit of teflon tape. Some of those air holes are very small, and plugging them off will cause starvation some place in the system, and if the operator is not aware of, or doesnt know...will cau$e $omething expen$ive to fail.

I use teflon pipe dope paste. Works fine, tastes great, less filling

Gunner

"Gunner, you are the same ridiculous liberal f--k you ever where." Scipio

Grant Teflon tape is not a sealant it is a lubricant. It is used to lubricate tapered pipe threads so that they will tighten easily without galling and seal as designed. IN CASE SOME ONE MISSED THE POINT TEFLON TAPE IS A LUBRICANT! lg no neat sig line

Well, here's one vote for just plain 'ol teflon tape. I've used it for years, for all kinds of gas/water/vacuum applications, and never had any trouble with it.

Properly applied it will produce a helium mass-spec leak tight connection with NPT fittings - brass, stainless, copper, or any combination of the above.

The other kinds of pipe dope compounds work too, like the SWAK with PTFE particles in it. But I find the teflon tape to be neater and more reliable.

Jim

Except with stainless on stainless. It doesn't always prevent galling. The stuff for that is Loctite PST.

Pete Keillor

I've used it for stainless on stainless NPT fittings. You are correct that it is unwise to try to dismantle and re-use that combination - but a properly made-up fitting set like that will seal just fine with teflon tape.

Jim

I agree Jim, my day job is process instrumentation, mostly online GC's. It's all pretty much SS tubing, from 1/16" up to 1/2". All the NPT fittings get teflon tape, and properly applied easily seals 3000 psi He and H2. Galling is a problem with the regular teflon tape but lately we've been using a nickel impregnated type. That's all but eliminated galling for us. The teflon paste stuff works well, but as you say can be messy, and I find if one doesn't allow it to set up overnight one ends up with weepy joints.

Paul

Probably most of those fittings are swagelock, or VCR though, right? I do a fair amount of rough-n-ready vaccum work in my line (cryogenics) and there's almost always some NPT stuff somewhere along the line. The teflon tape has always worked fine. I've never come across nickel impregnated though, I'll keep my eyes out.

Jim

Even though most of what we use is tubing, and you're correct, Swagelock or equivalent compression fittings predominate, nearly all the regulators, filter housings, rotameters, and valves come with NPT porting. Inside most of the instruments themselves it's all compression fittings, but the sample transport and conditioning systems exterior to the instrument, while tubing, employ plenty of tube to NPT adapters. We also use a lot of instrumentation pipe fittings, tees, nipples etc. that are also NPT.

The nickel bearing teflon tape we use is made by Federal Process Corporation, Pt# SA26. There phone is 800-846-7325 and

I know this on Christmas day only because I happened to find a part roll in the pocket of my work coat.

Paul

That stuff sounds interesting. I work in a research and small scale production environment, so we use a lot of ss tubing. Something to watch out for with the tape as well is to avoid leaving any tendrils or scraps at the fitting ends that could get into your instruments. Since we reconfigure a lot, the galling is an issue that made me give up on regular teflon tape. The PST stuff works great, but can be messy. I've had no problems with leaks.

On the sanitary stuff (production and pilot scale), we use a sanitary rated white paste, but npt is rare on that due to being difficult to clean without disassembly. Most is orbitally welded polished tubing with triclamps. Most gauges and instrumentation are fitted on Wika seals, which are annular smooth bore flow through seals.

Pete Keillor