Tolerance for Pipe Schedule per ASME B36.10 1

[cadbrowser]

We had some 1" piping come in (X-Strong or Schedule 80) that measured

O.D. = 1.315
I.D. = .980

Our drawing indicated that we needed a .957 I.D. (by default if we indicate a 3 place decimal there is a tolerance of +/- .010).

According to some literature referencing ASME B36.10 the allowable tolerance is +/- 12.5%. I want to confirm this with anyone that can, so we can pass the piping and not have to send it back.

Thanks in advance.
Jeremiah

 

[deanc]

12.5% is a wall thickness tolerance. There are also diameter and roundness tolerances.

You need to go to the actual pipe spec. such as ASTM A-53
also make sure you review the general standards as listed on the front page.

 

[NozzleTwister]

cadbrowser,

Pipe is specified by O.D. and wall thickness.

Per ASTM A106, the variation on the O.D. of 1" NPS pipe is +/-0.015" (1/64") and the variation on the wall thickness is +/-12.5%. ASME B36.10 lists O.D.'s and wall thicknesses to 3 decimal places but the tolerances mentioned above apply. There is no default accuracy of +/- .010 because of the 3 decimal place designation.

You asked for an I.D. of 0.957" and that's exactly the nominal I.D. for a 1" NPS sch. 80 pipe. You're O.D. is right on the money and your wall thickness is well within tolerance and only differs from the nominal wall by only O.0115"

If you needed a 0.957" maximum I.D. then you needed to be very specific about that when you ordered and make sure the vendor knows that that is a requirement by his own written acknowledgement.

If you needed machine shop tolerances, that's where you needed to get the pipe made instead of a mill.


NozzleTwister
Houston, Texas

 

[cadbrowser]

NozzleTwister said: "There is no default accuracy of +/- .010 because of the 3 decimal place designation."

You need to re-read my statement which was:

Our drawing indicated that we needed a .957 I.D. (by default if we indicate a 3 place decimal there is a tolerance of +/- .010).


The default accuracy comes from OUR drawing as a general note in the titleblock.

Inspection goes by our drawing, and since we were unaware of the 12.5% tolerance from ASTM 53, inspection was liable to return this pipe because according to our drawing it was out of tolerance.

That is the reason I posed the question, since ASTM 53 over-rules our drawing, we now know that when we send out a drawing for piping we will include the 12.5% within the dimension so inspection knows what to expect from a "mill".