Use of Multiple Types of Thread Sealant for NPT threads 5

[Cervantis]

We are having leaks using pre-baked "VIBRASEAL" on NPT male parts. Is there a Standard for type, amount and acceptable application for the sealant? And are there any rules on using multiple or combination of sealants.

 

[DesignerGuy16]

Always had better luck with liquid thread sealant as it doesn't get pushed off/torn if it's overapplied. I've had issues with this on Festo pneumatic fittings in the past where their pre-applied thread sealant was so thick it made it very difficult to install the fittings.

Just my $.02

James Spisich
Design Engineer, CSWP

 

[Cervantis]

The nipple has a "small" amount of sealant that is prebaked. The coupling is an on the edge of tolerance failure by being "too large". The mating pitches are causing stacking tolerance failures, and to try and "fix" it, the production line is applying pipe "dope" on top of the VIBRASEAL. I know there is a standard on "amounts" of sealant that should be used, I just have not been able to find it to bring some rational to the table. Thank you for your time and input.

 

[doc1955]

We have found Teflon tape to work the best for us in our hydraulic systems they are running at 5000psi.

Doc

http://www.goodrich.com

 

[hydtools]

I know of no 'standard' as to amount of sealant to be used.
There has been a long discussion on another thread over in Piping and fluid mechanics engineering:

http://www.eng-tips.com/viewthread.cfm?qid=242884&page=1

Ted

 

[unclesyd]

Here is one article concerning the pros and cons of tape and sealant. As the article states tape isn't a sealant, only a lubricant even though by application it will block some fluid pathways.

The second site is Xpando, a little different type sealant that I've had very good results with.

http://www.plantengineering.com/article/180554-Guidelines_For_Choosing_A_Pipe_Thread_Sealant.php

http://www.xpando.com/pjc.html

 

[Cervantis]

Thanks to all for this valuable information.

 

[TBP]

Lubrication is indeed important, but the one thing that absolutely MUST happen is to fill the spiral clearance between the crests of one thread, and the root of the other. It's also important to read the manufacturer's instructions for service limitations, and even pipe size. There are a variety of thicknesses of Teflon tape. The thin white stuff to the much heavier orange colour. The heavy stuff is difficult to apply to pipe under 1/2". I've never had much problem with properly applied tape, even on 150 & 300# steam systems. Having said that, there are those "special" individuals who'll fail to start wrapping one or two threads back. However, these are typically the same morons that load-on pipe dope, including female threads, so that now instead of strings of tape inside the pipe, there are blobs of dope.

X-Pando is an awesome thread sealant, but it does have a couple of drawbacks. It makes it difficult (frequently VERY difficult) to disassemble, and it takes at least overnight to set. The time thing usually means it's unsuitable for many maintenance jobs, as production people want this thing back in service 15 minutes ago.