NPT thread strength

[ryanje]

Does anyone know how To find out the amount force is needed to strip a 1 1/2" NPT thread made from 304 Stainless steel assuming a made-up length of engagement of about 0.68"?

Thanks

 

[EdDanzer]

You will need to give more information. See thread378-49291
After reading this thread then post additional information.

 

[ryanje]

I am mostly interested in when the threads will shear off. I need to determine whether the pipe will burst before the threads fail. I used the formula for shear area:

A=0.5*pi*(Pitch Diam at hand tight engagement)*(Length of engagement fully tightened)


then I used the assumption that shear strength is about 0.62 that of 304 Stainless steel's tensile strength. (ASTM A 394)

Then I used F=Pressure*Shear Area to determing the force required to shear the threads from the NPT fitting.

Does this result make sense? I came up with about 90,000LBS. Also I am assuming that the fitting is coupled (ie a male is connected to a female at the time of shearing)