UCS-56(a), Table UCS-56-1, ASME Sec. IX

[sushildwivedi16]

Hello to Everyone.

This query is with respect to the requirement of PWHT mentioned in Table UCS-56-1 & qualification of the PQR for the same

We are manufacturing a vessel with 20 mm thickness, SA 516 Gr. 70 (P No. 1) material. No special service requirements, no impact requirements. Hence as per table UCS-56-1 of ASME Sec. VIII Div. 1, PWHT is not required.

We have a qualified PQR of SA 516 Gr. 70 to SA 516 Gr. 70 material, 70 mm thickness, GTAW+SAW processes, tested without PWHT (i.e in as-welded condition).

A WPS was prepared for GTAW+SAW processes, to weld the joints of the above vessel. A note is added in the WPS stating that "THE TOTAL WELD METAL DEPOSITED USING THIS WPS SHALL BE 38 MM MAX" to comply with Table UCS-56-1 requirements.

The client has rejected this WPS stating that since PWHT is not required for the vessel, the PQR (without PWHT) can be qualified in 32 mm max thickness only. 70 mm thick PQR (without PWHT) cannot be accepted for these joints. Client has quoted the QG-100(b) clause of ASME Sec. IX "Whenever the referencing Code, standard, or specification imposes requirements different than those given in this Section, the requirements of the referencing Code, standard, or specification shall take precedence over the requirements of this Section".

I looked up for some interpretation related to this but couldnt find any. However, for P No. 3, interpretation for similar case exists (Interpretation No. Vlll-1-04-73, Record No. BC05-032) but dont know whether same can be applied to P No. 1.

Request all to throw some light on this.

Thanks & Regards
SD.

 

[metengr]

What welding process or processes do you intend to weld the 20mm thick vessel? Based on what you stated I see no reason why what you have proposed would not be acceptable. You can edit the note on the WPS for compliance with UCS-56 for no PWHT up to 32mm max thickness if preheat is a minimum of 95 deg C. You qualified the WPS for no PWHT up to a maximum thickness of 70mm.

 

[sushildwivedi16]

Thanks for the response metengr.

We intend to use GTAW+SAW process. The WPS includes the following ranges

Base metal thickness range : 5 mm to 200 mm
Total Deposited weld metal thickness : 38 mm max (using both processes together)
Preheat temperature : thickness < 32 mm - 30°C, thickness ≥ 32 mm - 100°C (70 mm thick PQR qualified with minimum preheat of 75°C)

The client's rejection is based on the ASME Sec. IX clause mentioned in the original post. Looking for any interpretation that can support our stand.

Thanks & Regards,
Sushil Dwivedi

 

[pradipgoswami]

Your Client is Right with respect to Code. Sec-IX is only a qualification code. Sec VIII is the design code. Welding has to conform to the requirements of Sec-IX as well as Sec-VIII. Acc to UCS-56 CS welds/BM over 38 mm(1.5 inch) requires PWHT. Typically PQR on a 70mm thk plate should have been qualified with PWHT to be in complete conformance to Sec VIII.

In the present context as PWHT is not required by the code, this PQR may be used up to 38 mm thk(both BM and deposited WM)with a minimal preheat of 200 Deg F. Metengr also guided you with similar recommendation.

As per your query there's no impact, however do not get caught if client insists on hardness restrictions.
Thanks.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[sushildwivedi16]

The base metal thickness range in WPS cannot be reduced to 38 mm max. Since the same WPS will be used for a corner joints between Shell (20 mm) to Tubesheet (90 mm). Dissimilar joint thicknesses. However all the necessary requirements of UCS-56 has been adhered to in the WPS

nominal thickness : total weld metal deposited thickness 38 mm max
Preheat of 100°C min for thicknesses greater than or equal to 32 mm

Ironically the same PQR and same type of WPSs (WPSs are made project wise as per our QA system) have been accepted by authorized inspectors in the past and also by team leader during ASME U-Stamp renewal audits and till date no such rejection for this reason has been faced.

 

[david339933]

What you are doing is acceptable. No where in Sec. VIII does it state that you must limit PQR qualification to 38mm for PWHT. It states or "requires" you to use PWHT for thicknesses over 38mm. It also states to qualify to Sec. IX. The statement you put on the WPS limiting thickness is adequate, and in my opinion satisfies UG-100.


As you stated, how do you satisfy dissimilar welds when one member is over 38mm thick? Both must be within the qualified thickness of QW-451.1 and may not require PWHT.

Just because the Code doesn't state that you are allowed to do something, doesn't mean it is prohibited.

This happened at an ASME tri-annual Audit recently and after a few phone calls by the auditor, it was put to bed and never mentioned again.