NPT Coupling Bore Diameter

[DBreyer]

Hi all,

is there a guidance for the internal bore diameter of NPT couplings to ASME B16.11?
From the dimensions given in the standard (taper and thread length L2) I can calculate a maximum bore diameter but couldn't find anything on the minimum diameter required?


Thanks four your help

Kind regards
Daniel

Daniel Breyer
Inspection Engineer

http://lnkd.in/dFcQA-w

 

[racookpe1978]

Your question doesn't make physical sense - as least the way it is phrased.

A "coupling" joins two separate pipe stubs together, an NPT (pipe threaded coupling) has two female threaded ends on its "inside" diameter. Each female NPT tapped thread is tapered = The outside threads are larger than the inside threads. A NPT male threaded pipe is screwed into the female threads (usually tapped to 7x threads deep) and so the fluid flow is limited by the flow in the pipes, not the coupling. Coupling ID is always smaller than pipe OD, larger than pipe ID.

Your threads must match the nominal NPT taper and depth and individual diameter. Buy a NPT tap and run it through those threads - but be aware you will end up cutting new threads at some point.

 

[10mm]

Are you referring to the tap drill size? A tap size chart is fairly simple to find. Machinerys Handbook has a section on npt threads and minor dia of threads for a given depth. Good luck.

There is no situation so bad that you cant make it worse. Cmdr_Hadfield

 

[SnTMan]

I interpret the OP is referring to the center, un-tapped portion of the coupling. Per B16.11 I see no ID / thickness requirements on this feature. Presumably not larger than the tap drill size, but again, no specified dimension.

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand