Frequency of Measuring Pipe Expansion Ratio 1

[tm0284]

I was wondering how often does API 5L require calculation of the sizing ratio? Is calculation of the sizing ratio the only requirement to verify the expansion? Since the sizing ratio is determined by taking measurements on the outer diameter, do the same rules apply for validation of expansion and determining the sizing ratio? Or does the sizing ratio need to be checked more often then the OD?
I would appreciate any insight or resources that could be pointed to as a useful reference.

below are some quotes from API 5L

8.2 Processes requiring validation
Final operations performed during pipe manufacturing that affect attribute compliance as required in this
Standard (except chemical composition and dimensions) shall have their processes validated.
Those processes requiring validation are the following: for SAW and COW pipe, expanded: pipe forming, seam welding, repair welding, expansion

10.2.8.1 The diameter of pipes shall be measured at least once per 4 hours per operating shift to verify conformance to the diameter tolerances (see Table 10).

Table 18 — Inspection frequency for PSL 2 pipe (continued)
Test Type: Pipe diameter and out-of-roundness for pipe with D ≤ 168,3 mm (6.625 in) SMLS, HFW, or SAW
Frequency: Once per test unit of not more than 100 lengths of pipe

Thanks

 

[PipeDream77]

Pipe Expansion is identified by API 5L as a process that requires validation. You need to implement a measurement frequency sufficient to maintain process control. Per API 5L, Table 18, most mechanical properties are based on a frequency of once per test unit having the same expansion ratio. Per Footnote A in that table, if your expansion ratio increases or decreases by more than 0.002, you are obligated to test the pipe as a new test unit. To avoid having to do additional testing, you need to validate your process to assure you measure often enough to avoid having pipe expanded outside the 0.002 allowance. If you find your expansion process is stable, you can decrease the number of measurements. If it is not stable, you have to do more measurements and/or possibly do additional testing to be in conformance with the specification.