Threaded Fittings in Burst Pressure Calcs 1

[BJFBama]

I'm trying to estimate the burst pressure of a relatively short section of pipe. The classical equations (Barlow, Lame, etc.) are simple enough to find but I haven't found any reference as to how to account for treaded connections on the ends. Is it really as simple as reducing the wall thickness by the depth of the threads?? On the surface (pardon the pun) it would seem more complex than that.

Thanks in advance for helping this CHEMe with limited mechanics background!

 

[kenmac777]

I would think that deducting the depth of the threads from the nominal wall thickness (minus the 12.5% tolerance) would give you a conservative burst pressure. Since the threads are tapered, the deepest threads are actually at the very ends of the pipe where they are restrained in the radial direction by whatever fitting they are screwed into.
I wouldn't expect the pipe to burst inside the fitting.

 

[BJFBama]

Thanks kenmac. I agree, it seems that rupture will occur at the one or two threads exposed outside of the fitting, just trying to quantify it. Your point about the taper is something I hadn't considered. I will search for some specs on NPT threads. Any leads would also be appreciated.

Thanks much.

 

[kenmac777]

Try the "Machinery's Handbook" which should be in Section 621.8 of any decent library.