Test Coupon for Procedure Qualification

At first, the following study is based on an assumption that the pipe sizes are DN 15 (1/2" NPS) and DN 150 (6" NPS).

Also, I'd like to declare that DN 15 doesn't mean OD is 15 mm (actual OD is 21.3 mm) & also, DN 150 doesn't mean OD is 150 mm (actual OD is 168.3 mm), see the attached Table 1 of ASME B36.10M.

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♣ With Respect to the Diameters:

• For pipes with size DN 15 (1/2" NPS) (actual OD is 21.3 mm < OD 25 mm), from Table QW-452.3 of ASME IX, this size shall be qualified by the size itself as a min. up to unlimited dia. for max.

• For pipes with size DN 150 (6" NPS) (actual OD is 168.3 mm > OD 73), and from the same Table QW-452.3, this size shall be qualified by the size 2-1/2" NPS as a min. up to unlimited dia. for max.

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◊ From above, we find that such a test coupon with:

• Size DN 15 (1/2" NPS) can be used to qualify both diameters DN15 & DN 150 (1/2" & 6" NPS), [and this is only imply in case of thicknesses within the limits of the code].

• Size DN 150 (6" NPS) can't be used to qualify DN 15 (1/2" NPS), although the thicknesses within the limit of the code.

♣ With Respect to the Thicknesses:

• For pipe with DN 15 (1/2" NPS) Sch. 10 (thickness 2.11 mm), from Table QW-452.1(b) of ASME IX, this thickness shall qualify its t = 2.11 mm up to 2t = 4.22 mm.

• For pipe with DN 150 (6" NPS), Sch. 40 (7.11 mm), from Table QW-452.1(b), this thickness can qualify its t = 7.11 mm up to 2t = 14.22 mm.

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◊ From above, we find that such a test coupon with:

• Size 1/2" NPS (DN15), Sch.10 can be used to qualify both sizes (but shall not qualify both thicknesses).

• Size 6" NPS (DN150), Sch.40 shall not qualify the size nor the thickness of DN 15 (1/2" NPS) Sch. 10.

Therefore my recommendation is:

A separate WPS & PQR shall be used to qualify each size alone, i.e. there must be at least 2 WPS's and 2 PQR's to execute that project.

Note. If the outside diameters as derived at your post are OD 15 mm and OD 150 mm, please make a check and repeat the prescribed study by yourself.