About a thousand years ago, during my college days, I worked as a plumber's helper summer job. At that time it paid about 25 cents/hr. Good pay back then!
At any rate, we used ONLY two products for sealing threaded pipes, be they steel, galvanized, black iron, or brass. IF the piping circuit was for gas or petroleum products, we ONLY used PERMATEX, the shellac-based GOO that stuck to your fingers & tools better than SUPER GLUE. And, for water, steam & drainage, we used this gray glop, called PRO-DOPE. Even though the printing on the can said it was OK for gas, we NEVER used it there.
So, I guess my question now is, "Why can't PERMATEX be used for this critical application?"
Even now in my adult life, I avoid teflon tape, both professionally when building pneumatic/hydraulic computer-controlled machines, OR personally, when dealing with plumbing problems at home. The "Stringiness" is one problem area that I've had to overcome. There are others.....
OK, I did not get that the sealant was teflon filled, from the article. There are a lot of types and chemistries of pipe sealers around, and many of them are both low performance and quite cheap, and not nearly as good. I have had good luck using the more reliable brand of the TFE filed sealer, but I am aware that poor quality products are always available and often sold for less.
I'll agree that it is a sealant not to be used by unskilled people, but the sealing dope that is the subject of the article was a teflon dope, brushed on from a can It would seem that the liquid carrier was soluble in the fuel. I was not told the brand, but I was told it listed avaitation fuels as compatible.
We have enough trouble hiring people who can read 5/8" on a ruler! and don't have to be told "rightie tightie"
Either way, our little tester is a simple way to detect leaks in suction pipe if there is a verticle lift.
gtp, of course it is possible for a skilled person to apply tape so that no shreds of teflon are created during assembly. During dis-assembly there would be shreds that could get into the system. In addition, the procedure that you describe would require a bit of skill and remembering to do the job just right. So while it could be done that way, the potential for problems is not woth the savings produced by using the teflon paste sealer. That was the decision by at least one of the large automakers.
The correct way to apply teflon tape is to not apply it to the first thread and not to apply it too thickly. On good threads, 1.5 wraps is enough, for pipe sizes under 1". We use more on larger pipe. This prevents "strings" from forming, they are the excess tape before the first thread.
This doesn't work is you are trying to prevent galling of, for example aluminum threads on aluminum threads.
It also must be applied under tension, to deform it into the threads. If just piled on, it will strip off.
Over the years we have had quite a few customers who forbid the use of teflon tape as a sealer just because of those little strings. They are quite real and they will certainly cause valves to leak, and they are incredibly difficult to completely remove feom a system. The recommended sealer has been teflon paste, applied per a fairly detaled specification. But one would need to use a teflon paste compatible with the particular fluid. Probably any rated for gasoline service would also work for jet fuel.
Teflon tape by its nature is kind of stringy. Sometimes the tread can cut a bit off which can get lodged in solenoid valves causing them to leak.
I recall that NASA once had found the root cause of some leaky valves to be tiny Teflon "threads" in the system. They had banned Teflon tape in favor of Teflon dopes or other dopes.
If Teflon tape was required they had to be able to visually inspected the inside of each connection. Obviously, very difficult or impossible to do.
Dopes are essentially, a sealing powder with a flowable liquid binder. If the powder somehow "escapes" it doesn't cause problems like the thin hairs of Teflon tape. Of course, all the components of the dope must be compatible with your application.
We have found an interesting trick with small straight thread connections that have flats. We twist tape into a rope, wrap it around the base of the thread and tighten the pieces together. The teflon flows into the area of the flats and makes a gasket of sorts. It takes the right kind of flats and the right amount of tape, You should not count on any particular application to work without testing, that is my CYA message. We have not used this on high pressure - Jim
I like the use of teflon tape as a sealant. I find I use it a lot, mostly in plumbing repairs, but sometimes in pressurized systems. It is wonderfully easy to work with and easy to "clean". I like the idea of the Vaseline to protect the tape. Great job.
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