Dear Mr. Stephen,
Your case is in accordance with Code Sec. IX. Just to brief about section QW-200.4(b), find below example.
To weld a pipe with thickness of 20mm, you can support two PQR like this, if notch toughness requirements are not imposed by other code sections.
1st PQR qualified in GTAW with 7.11mm and 2nd PQR with SMAW with 10mm thickness. Combining these two PQR(s), you can write a WPS with thickness range 1.6mm to 20mm as per QW-451.1 with GTAW at root and subsequent passes with SMAW, which is not acceptable as per above clause. As per QW-200.4(b), the thickness limit is 1.6mm to 13mm only.
It means that when you support PQR for root pass welding shall have minimum thickness of ½” or 13mm in order to weld any greater base metal thicknesses. Technically, the rate of cooling, residual thermal stresses etc. would be similar for greater base metal thicknesses if welding procedure qualified in 13mm and above for root welding purpose only, since root is considered to be critical and moreover it is wetted part in the weldment.
If it is a single coupon and combining with root welding process then the above clause is not applicable.
Hope it clarifies.
Regards,
L. Prabhu kumar,
Sr. Principal Engineer,
Equipments & Materials Dept.,
Saipem India Projects Limited,
Tel:+91 44 43906588, Ext.: 588, Fax:+91 44 66840345,
Mobile Ph. No.: +91 9003010978.
From:
Sent: Friday, June 25, 2010 6:55 AM
To:
Subject: [MW:5733] PQR Qualification
Hi,
Regarding ASME IX section QW-200.4(b) and reference to minimum 13mm is this relevant to our case as although we are combining two processes we are not combining two PQR’s or procedures. We are using GTAW & MMAW on a single WPS but do not separate the two and only have the one welder completing both processes off the WPS. We selected 150NB STD ASTM A 106 GB pipe with a wall thickness of 7.11 as the coupon for WPS & PQR qualification as this is the maximum size pipe we utilise and the WPS therefore qualifies 1.6mm to 14.22mm. Just like to confirm this coupon size is in accordance with the code.
Many Thanks
Stephen
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