[TR] Thread Sealant Recommendation

[Randall]

> OK, I've got to screw a Spal fan temp sensor into an aluminum 
> bung and Spal says NOT to use Teflon tape. I also have a 
> petcock and an filler neck overflow fitting also going into 
> aluminum bungs. All bungs are NPT fittings.
> So two questions: do I even need any sealant with NPT threads 
> and, If I do, what's the recommendation?

Do they say why not to use Teflon tape ?  I would probably use PTFE sealing
compound, which is similar but cannot form 'strings' of tape to cause
problems elsewhere.  I've used it on both brass and steel NPT into aluminum,
and it seems to work fine.  It squeezes out of the tight places easily, so I
don't see how it could cause problems with either electrical or thermal
conductivity.

If there is a some reason to avoid PTFE/Teflon, then I'd probably use
Hylomar.  It might seal with nothing on it, but my experience is that it's
easier to seal (meaning less torque required) and less likely to start
leaking in the future, if you use something.

Randall