Best way to seal steam boiler threads 1

[bigalanc1]

In my past experiance we have used teflon tape and teflon paste for best results in sealing steam boiler threads up to 100psi. Is thier any spec. that states the best way to seal pipes that are heated and cooled down on a regular basis? We have a new QC guy in that is trying to go to a paste product only. and in doing so we are springing leaks all over. ( don't touch what's not broken) I was just wondering if there was a tape and dope spec. as a standard out there.

 

[dtn6770]

I'm familiar with using FELPRO C5A / NICKEL-EASE in steam & condensate service up to class 600 (flange) systems. I'm not aware of any movements to change so it must work okay.

 

[bigalanc1]

I was also hoping if you new of any spec. that will validate us using the tape and dope theory.

 

[dtn6770]

I'm working off of company and facility specific piping specifications. Industry wise, both ASME B31.1 and B31.3 have sections (135.5.1 and 335.3.1, respectively) that state thread compounds need to be suitable for the service, that is, compatable with the the pipe and what's in the pipe.

I know of no Industry Code or Standard that goes so far as to say what thread compound or tape or lubricant should be used. That call is pretty much up to the end user or someone in the end users' employ.

 

[stanlsimon]

Be careful when threading into brass fittings with teflon containing products because the teflon lubricates to such an extent that the female fitting will split.

I've always used rectorseal #5. It conforms to TT-s1732.

 

[moltenmetal]

"teflon paste" is a misnomer. What you want is an anaerobic pipethread sealant, aka a "pipe dope", applied either as a top-dressing on a full-density teflon tape or in the absence of teflon tape.

The anaerobic thread sealants such as those made by Henkel "Loctite" are flexible to handle the thermal expansion/contraction problems that tape alone may not seal reliably long-term.

 

[kbs]

If the threads are on a reused nipple or length of pipe, cotton wick and pipe dope has never failed me. Teflon tape acts as a lubricant not a sealant.

 

[moltenmetal]

Teflon tape acts as both a lubricant and a large void filler/sealant. In some services it's all you need, but steam isn't one of those. Teflon tape is not a true elastomer, and is subject to creep, and hence doesn't handle thermal cycling very well.

 

[bigalanc1]

Thanks for your response. The dope alone (lictite) does not work well with the steam application. We have tried and started to have leaks. Even when calling Lictite themselves they will not guaranty any of thier products for steam. That is why we always used tape and dope. We are running different test on different dopes with little or no progress. All dopes leak after being heated and cooled on a countinuous basis. That was the reason for using tape and dope, all through testing no leaks on this sample.

 

[TedLinsle]

You should use either/or but not both. Dope & tape will lubricate and seal threads, but not each other.

 

[bigalanc1]

Are you sealing threads on steam, TedLinsle?

 

[nosabe]

We use only Fel-Pro copper based pipe dope for steam and condesate piping so far so good

 

[moltenmetal]

TedLinsle: I originally thought the same thing. But we've been using paste over tape for ten years in a wide range of industrial threaded pipefitting, including LP steam, and we find that the combination is superior in both initial and long-term leak sealing versus paste alone, and vastly superior to tape alone.