stainless steel sealing problem

[eski1]

hi
we have just put in a stainless steel bsp threaded 2" ring main into a factory and after pressurizing the system with 2 bar of cold water i walked round and spotted 25 out of the 150 joints leaking , most were small leaks but this was far from exceptable i need to get to the bottom of this quickly .
the process we used was to cut thread as usual with pipe threader ( new jaws ) then cleaned thread with cloth, put on loctite 55 about 20- 25 wraps then put on loctite 5331 smeared over thread tape and done up the fitting as per normal . this joint would then be left for at least 24 hours before pressurizing .
The 2 sealing products were given to us by the factory engineer at we were told we had to use these as pipeline products had ensured these would be fine.
now i have heard that the problem could be that the threads on stainless are so smooth that when you do them up the thread tape will just wind out unless you roughen up the thread with a special tool ?

is this true or is there another reason
also how do other people seal stainless pipe ?

 

[tickle]

From my experience 20-25 wraps seems a little high.

Some thread sealing compounds can be put straight onto the metal.

Have you had a look at the manufacturers website? Have you installed the sealing compounds in accordance with the manufacturers recommendations?

Some of my mechanical contractors (that work mainly in the water industry) used a yellow resin type thread solution. It was called SureSeal or something. They said it was the bees knees.

I thought that stainless was a hard material and that it did not form a smooth surface and "locked up" a major headache for fitters and stainless bolting. Stainless breaks off as platelets to give the rough surface.

Generally stainless pipe would be thinner than its carbon steel counterpart. Is there any distortion on the pipe diameter casued by threading or attachment?

I have also had the same problem with leaking threaded stainless joints and had to resort to seal welding the threads.

I would imagine that you are going to need to remake those joints and more and because, 2 bar does not seem like a high pressure - water systems are usually rated to PN16. I guess that you are taking the pressure higher therefore you are going to experience more leaks.

 

[quadtracker]

Try using loctite 565 thread sealant alone with no tape it should work fine. Do not cut more threads than the width of the dies, on the pipe, otherwise you will have lost the taper fit with those extra threads extending on the pipe. Those extra threads would be cut as straight threads (with no taper) and won't seal properly in the fittings. I hope this info is useful.