API 5L Out of roundess and ovality

[shattersys]

Hey all

I have 24" pipe (610 mm) and I am trying to figure out (out of roundess) spec. According to API 5L, it is 0.020D and 0.015D for pipe end. How do I calculate ovality % that the pipe needs to be within.

Thanks

 

[tankman64]

So I think what you are asking is how the out-of-roundness is measured? First draw the smallest circle that encloses the pipe shape. Then measure the distance from the circle to the inner most edge of the pipe shape. This distance is your deviation and should be less than 2% D or 1½% D as applicable. Lets assume that you have a perfect oval or ellipse, then the deviation would be (major dia - minor dia) / 2. Ovals or near perfect ovals are pretty common on large dia. thin wall cylinders. Watch out for flat spots at longitudinal weld seams.
When checking the diameter you generally first measure the pipe circumference in order to establish the actual diameter.

 

[shattersys]

Thanks for the reply. The client spec says the ovality cannot be more than 4.9% for 24"(610mm) pipe and refers to API 5L. 5L states the tolerance for 24" pipe is 0.015D for the pipe ends and 0.020D for everything but the pipe ends. Any idea how the 4.9% ovality would be calculated from API 5L tolerances? Thanks!

 

[tankman64]

Just tell him that you're complying with API and everyone should be happy.

 

[Duwe6]

shattersys, you are overthinking the problem.
A - API sez "0.02D" which equals 2%. And the client [only] wants 4.9% So the pipe is fine.
B - To actually measure 24" pipe, you need 30"(+) calipers. Then take the least diameter found, and at that same place get the max. diameter - should be 90° out from least. tankman64 has already given you the formula. Use it. Send the client a report of your findings.
Simple.