12.5 Pipe wall thickness tolerances

[msen]

Dear All,

İS this tolerance valid only for standard sketches or is it applicable also for wall thicknes definitions such as 4" 6,35 wt which is not among standard dimensions.

Even if I specify wall thickness of the pipe directly (4" and 6,35 wt) in my purchase order, instead of defining it with standard sketch dimensions ( 4" sketch 40), does manunfacturer still has right to manufacture between this (0,875 x tn) tolerance limits?

 

[metengr]

Per ASTM A 999 specification, when ordering pipe

tn × 0.875 = tm
where:
tn = nominal (average) wall thickness, in. [mm], and
tm = minimum wall thicknesses, in. [mm],

10. Permissible Variations in Wall Thickness
10.1 Seamless and Welded—Except as required by 10.1.1,
the minimum wall thickness at any point shall not be more than
12.5 % under the nominal wall thickness specified. The minimum
wall thickness on inspection is shown in Table X1.1.
10.1.1 Minimum Wall—If the wall thickness of the pipe is
specified as minimum wall in the purchase order, there shall be
no variation under the specified wall thickness.

 

[msen]

thank you metengr for your answer.

Even if I specify wall thickness of the pipe directly (4" and 6,35 wt) in my purchase order, instead of defining it with standard sketch dimensions ( 4" sketch 40), does manunfacturer still has right to manufacture between this (0,875 x tn) tolerance limits?

if so thats bad for me

 

[Mr168]

As metengr noted, you can order by min wall per the spec, which will guarantee a wall thickness equal to or greater than that specified. Any tolerance beyond this is a commercial issue, and would need to be specified and agreed upon in your purchase order with the supplier. Expect it to be priced accordingly.

If I am the supplier and do not see the words "min wall" or "minimum wall" on your PO somewhere, then I am going to assume that the standard specification tolerances apply. Just stating a given wall thickness with no tolerance does not imply that minimum wall thickness is being requested in my opinion.

 

[KevinNZ]

You can order to another pipe code. e/g API5L allows 10% under. There is also a weight/length tolerance.

If you are after only a small stocked length of pipe, you can have it measured before purchasing.

We welded pipe we often spec %5 under. This is not costly as the plate they use for the pipe is within this tolerance anyway.