diameter tolerances

Date 03-03-2013 13:55

Check the base metal specification, i.e., ASTM A53, ASTM A106 for carbon steel pipe, ASTM A312 for stainless pipe, etc.

The construction code; ASME B31.3, B31.1, etc. may provide some additional guidance.

Al

By Joey

Date 03-04-2013 07:37

Out-of-roundness ; you get the difference between the max and min inside diameters at any cross section, the difference should not exceed 1% of the nominal diameter at the cross section.

But how will it pass the dimensional check when you can visually confirm the pipe is in "oval shape". Surely, there will have a misalignment during fit-up assembly.

~Joey~

By G.S.Crisi (****)

Date 03-04-2013 22:44

As Joey said, the out of roundness tolerance is 1% of the nominal diameter. For a 30 inches (762 mm) diameter, the tolerance will be 7,6 mm, more than 1/4 of an inch.
You don't need to reject anything. Using strongbacks and wedges you'll drive up the two ends until they face perfectly each other and the joint can be welded.
In the case of pipe and elbows, the pipe is the weakest piece and it will conform to fit the elbow shape.
Giovanni S. Crisi
Sao Paulo - Brazil

By maxilimiano (**)

Date 03-06-2013 12:10

Hello brother,

you can reject that by "missalignment". because of that shape, you will get difficulty to weld with normal pipe.

regards

By G.S.Crisi (****)

Date 03-07-2013 22:51

Max,
The standards to which the pipes are made (A 53, A 106, API 5L, etc.) allow an out of roundness of 1%. This means nothing in a 2 inches pipe, but means a great deal in a 30 inches pipe, as the one we're talking about. As I said in my first posting, it means that the out of roundness may be 7,6 millimeters, more than 1/4 of an inch.
If scirocco's 30 inches pipe shows an out of roundness of, say, 7,5 millimeters, it can not be rejected because it is within standard. What he (scirocco) should do is to employ the usual strongbacks and wedges to match the two pipe ends, and then weld them.
Giovanni S. Crisi

By WELDICCAWSCWI (**)

Date 03-08-2013 05:13

dearman clsamps and the heavy steel basket clamps will work wonders .you weld a a dog on a pipeline

its anm automatic cutout weld outside weld groove,. so calif gas requires backwelding on all pipe fittings over 12" due to

mis,match between pipe and fittings