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American Pipe Threads (NPT) Stress

American Pipe Threads (NPT) Stress

American Pipe Threads (NPT) Stress

(OP)
I am trying to determine stresses in NPT threads.  I need to design a 6-8NPT threaded connection capable of withstanding 2000 PSI.  The preferred material is a cast brass.  I have been unsuccessful in locating any formulas or technical data to help determine stress in NPT threads.  I expect to find a hoop stress component and a shear component acting on the connection due to stress induced by tightening the tapered connection together, hydrostatic pressure inside the connection, and axial forces pulling the components apart.

Initial testing on a prototype has shown failure due to both shearing of threads, and increased thread diameter of the internally threaded component.

RE: American Pipe Threads (NPT) Stress

ANSI/ASME B1.20.1 -2001 will give you all the dimensional requirements for threads.  From there ANSI B31.3 will give the maximum allowed stress values for your materials and the calculations for wall thickness.

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