Ptfe

[terrie73]

changed a semi-hermetic copeland over the weekend and the engineer/ technician i was working with started pulling out some ptfe to use on thread for couplings and fittings

i looked in shear digust and asked him what he was doing as i,ve only been there a few weeks and he's been there over 10 years i just let him get on with it

whats the take on ptfe is it all right to use on old refrigerants (poe) but not the blends (ester)?

as ive always used some form of paste or specific locktite

anyway it turned out to be a poxy job as the shell of compressor has a crack in it and we must return new one ( i doubt the service manager is going to be pleased monday morning

compressor rewinder took more care in painting the compressor than leak testing it in house

still nice bit of overtime i aint complaining

[MarcoM]

Hi Terrie,

I work in a Commercial Display Case Manufacturer and we use PTFE in all TEV's ODF connections. We use blend refrigerants and we've never had any problems... I've even asked Danfoss Engineer (our supplier) and he said that besides PTFE, locktite was the other possible solution.

Cheers

MarcoM

[Johnny Rod]

In my limited pipe-fitting knowledge you should only be using PTFE tape on tapered threads like BSPT or NPT, but that aside PTFE (Teflon) is one of the most inert materials around, so you could use it in contact with pretty much anything, certainly all refrigerants and oils.

[Argus]

.

PTFE was the universal replacement for all sorts of thread sealants.

Before PTFE we used Litharge and Glycerine mixed to a paste. A legacy from the old days of steam, it was perfect on all threads once it had set off. All of us old fogies will remember that stuff.

Don't ask where you can get it - you can't. Litharge is Lead oxide, so it's BANNED.

For a while, after that, I used some imported stuff called OSOTITE (Honest!).
A long defunct wholesaler in Wandsworth used to sell it. Its principle use was in the motor trade as a sealant for diesel lines; it worked just as well on refrigerants and would withstand discharge heat; you can't find that anymore.

Locktite sounds a better idea to me than PTFE because I have never considered PTFE a permanent solution, it usually leaks after a few years, but what sort of Locktite compound? Is there anything in the Locktite armoury to deal with refrigerants, oils and the extremes of temperature?
Are there any readers of this forum at Locktite Inc who can explain?

Johnny's right about tapered threads, PTFE being naturally slippery, tends to slide along the treads, in my experience. There always seems to be a hint of oil around PTFE joints.

Along with flare joints and schrader valves, I would like to see PTFE banned for use on refrigerants because it is a potential source of leaks, so what?s the accepted replacement?


.
________
Rolls-Royce Camargue

[US Iceman]

Hi Argus,

Here is a general purpose catalog for Loctite products...

http://www.loctite.com/int_henkel/lo...ullCatalog.pdf

Here is a link I found to a refrigerant thread sealer...

http://tds.loctite.com/tds5/docs/554-EN.pdf

Here is something I have used for thread sealant with refrigerants. I have first hand knowledge of this (the blue material, I have not used the gold variety). Any place where I have used the blue Leak Lock sealant I have not had any problems with leaks.

It is similar to Locktite. Leak Lock is a thick liquid that is applied to the threads. When it sets up, it is hard. It can be removed from the female joint, but it may be difficult.

http://www.highsidechem.com/leaklck.html

Before PTFE we used Litharge and Glycerine mixed to a paste. A legacy from the old days of steam, it was perfect on all threads once it had set off. All of us old fogies will remember that stuff.

Ahhh, the good old days. I remember this stuff.

Along with flare joints and schrader valves, ... a potential source of leaks, so what’s the accepted replacement?

I like the Parker or Swagelok compression fittings, in lieu of the flared connections. These fittings are also used on hydraulic lines, so no problem with pressure ability. A straight square cut, deburr the tubing ID, and slip into the fittings and tighten. You're done.

Swagelok fittings...
http://www.swagelok.com/search/find_....aspx?DBID=N02

Parker fittings...
http://www.parker.com/tfd/cat/pdffiles/open.pdf

You have to make sure you use the proper fittings and ferrules for the tubing, but they work very well. Also, these can work for R-410, so no need for special tools or additional materials.

My two cents...

[TXiceman]

Wow, I did not think that I was that old, but I still remember some of the old timers using litharge and glycerine. One thing I remember about this was that once you made up a pipe thread joint with it, it did not leak and you were not getting it apart again.

In more recent years, we used mostly a refrigerant grade Loc-tite of thread sealant with PTFE (Teflon). This works very well.

Best design of all is to eliminate screwed connection where ever possible. Wher you have to make up a tubing joint, Parker-Hannifien and Swagelok make a triple lock type tubing fitting that is good in refrigerant and oil service for SS, steel and other hard tubings.

Ken

[frank]

Here is something I have used for thread sealant with refrigerants. I have first hand knowledge of this (the blue material, I have not used the gold variety). Any place where I have used the blue Leak Lock sealant I have not had any problems with leaks.

It is similar to Locktite. Leak Lock is a thick liquid that is applied to the threads. When it sets up, it is hard. It can be removed from the female joint, but it may be difficult.

We've been using Leak Lock since they introduced R407C and we've never had any leak related problems since

[Temprite]

We use Leak lok on all split installs. (Definetely reverse cycle.)

Mitsubishi Electric are not big fans of the stuff.

Also use teflon and leak lock on suction connections to TX valve.