Pipe Wall Thickness

Pipes come with standard thickness. It is for you to consider mill tolerance allowance in thk calculations. The tolerances are specified in respective pipe standard. You can assume a safe tolerance of 12.5%

Refer to API 5L, Para 7.3 "Wall Thickness" and Table 9 "Tolerances for Wall Thicknesses".

Quoted

7.3 Wall Thickness

Each length of pipe shall be measured for conformance to the specified wall thickness requirements. The wall thickness at any location shall be within the tolerances specified in Table 9, except that the weld area shall not be limited by the plus tolerance. Wall thickness measurements shall be made with a mechanical caliper or with a properly calibrated nondestructive inspection device of appropriate accuracy. In case of dispute, the measurement determined by use of the mechanical caliper shall govern. The mechanical caliper shall be fitted with contact pins having circular cross sections of 1/4 in. (6.35 mm) diameter. The end of the pin contacting the inside surface of the pipe shall be rounded to a maximum radius of 11/2 in. (38.10 mm) for pipe of size 65/8 or larger, and to a maximum radius of d/4 for pipe smaller than size 65/8, with a minimum radius of 1/8 in. (3.2 mm). The end of the pin contacting the outside surface of the pipe shall be either flat or rounded to a radius of not less than 11/2 in. (38.10 mm).

Table 9 – Tolerances for Wall Thicknesses

Unquoted

As you see from Table 9, the min. tolerance for all type of pipe and its grades and NPS's is -12.5%, but the max. tolerance varies depends on the type of pipe and its grades and NPS's.

Note. You can use and apply the tolerances at Table 9 even you make your design calculations as per ASME B31.3.

Thanks guys for your reply and time.

The same your post #21 at Piping Class Materials and post #11 at Arabian Heavy Crude and Flow Rate .

uh ?

Hi Everybody,

What would be the effect on Mill tolerance for an API SPEC 5L pipe due to provision of both Diameter and Thickness Tolerances? Does specifying Thickness tolerance alone in the Pipe Wall Thickness Calculation and mentioning the OD of pipe to comply with ASME B 36.10 help?

Please suggest if any, and please correct me in case my interpretation on this is wrong.

Thanks in Advance,
VIV