I have calculated for the Stress Area At for ACME from the Machinery Handbook 26th, pg 1794. and then inputed it in the Length of engagement formula Le on pg 1490.

It gives me a value but isn't this based on the minimum length of engagement so a bolt breaks before the thread strips?

How do you correlate this to the internal pressure?

If I calculate the force on the pipe cap wall, F=PxA where the internal pressure is 50000psi and the area is .506in^2. This gives me 25300 lbf.

Now, if I use the Load to Break formula on pg 1491. P=S*At where my Ultimate Tensile Strength is 195000psi and At for my ACME is 1.266 it gives me 246903 lbf. Does this mean that it would take 246903 lbf to strip off the threads but because the force on the cap is 25300lbf I have a safety factor of 9.75?!