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At my current role we have a hell of a time trying to get NPT threads to seal. We avoid them where we can but sometimes its just faster and cheaper to spec and buy parts with NPT threads.

We are using pipe dope and I fully trust in my techs skills. Is there any other methods or products out there that can help ensure a good seal ?

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  • $\begingroup$ I have to admit that I don't know the answer to your question -- but if you'll let us know what fluids you're sealing against, pressure, and what constitutes an unacceptable leak to you, then whoever can answer will have enough information. $\endgroup$ – TimWescott Oct 29 '19 at 17:50
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With good quality threads, 3 wraps of PTFE tape can seal NPT connections above 1,000 psi. SAE J1926 straight thread o-ring ports will seal a lot easier though. I've also used this company in the past: https://www.highpressure.com/

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NPT are not intended to hold very high pressure , but I do not remember a number. The oil/gas industry uses proprietary threads for wells with pressure above roughly 500 psi ( depending on the company). NPT requires dope to plug the spiral leak-paths at the thread roots ; API pipe dope contains metal powders ( copper, zinc, and formerly lead) to block the leak paths ( API threads are similar to NPT , but not identical). This assumes your NPT thread profile, pitch, diameter, taper, etc , conform to ASTM A 530. Common pipe dopes of teflon or traditional plumbers putty should be good to over 100 psi. Maybe a metal powder filled dope will help.

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