Dear Sir,

General Information

Base metal - SA 387 Gr 11 CL 2
P No. 4 & Gr No 1
Test Coupon thickness = T= 85 mm
Welding Processs = GTAW + SMAW (Root GTAW and rest SMAW)

I like to ask one simple thing which i cant find in ASME Section VIII Div (1) but the same is the requirement of PQR.

Post weld heat treatment (QW-407) mentioned in my PQR is as follows:
a) Temperature = 680 deg. C
b) Time = 16 hrs

I have checked table UCS-56, for P No. 4 and Gr.1 (my base metal), minimum normal holding temperature is 650 deg. C and Over 2 in to 5 in, minimum holding time at normal temperature is 1 hr/ 25mm.

Question 1:
How to PQR stated temperature i.e. 680 deg C and time i.e. 16 hr.

Similarly Preheat (QW-406) mentioned in PQR is as follows:

a) Preheat temperature = 250 deg C
b) Interpass temperature = 300 deg C Max
c) Intermediate Postheating = 350 deg C for 4 hr (Cooling under insulation)

Question 2:
How to review above a,b and c points according to ASME Sections as i have checked Appendix R i.e. R3 (ASME Section VIII Div 1), it only mentions 121 deg C preheat temperature for P No.4 and Gr.1.

Where can i find below mentioned information:

1) To review 250 deg C is right or wrong
2) How to confirm interpass temperature range for P No. 4 and Gr. 1
3) How to confirm Postheating = 350 deg C for 4 hr

Lastly is it recommended to review Carbon Equivalent of Electron with Base Metal compositions and if Yes can you please advice me the correct method to do the same?

Osama

_________________
Syed Osama Nusrat Ali
Exective Engineering (Project)
Fauji Fertilizer Company Limited
Pakistan
email: osama_ali@ffc.com.pk
Cell # +92-3025252018

Please reply

As the matter is urgent

_________________
Syed Osama Nusrat Ali
Exective Engineering (Project)
Fauji Fertilizer Company Limited
Pakistan
email: osama_ali@ffc.com.pk
Cell # +92-3025252018

Osama,
A PQR is a record of the qualification test done.
The only way of checking it's correctness is winessing the welding and testing of the coupon and verify by measurement and observation the correctness of the values.

Checking records from the welding is an indirect method, still gives you some information.

The way you are asking sounds like you are preparing for an ASME Joint Review. In this case consult your Authorized inspector for advice.

DK

Osama,

Acc. to ASME IX:
-250 °C preheating in the PQR is o.k. provided that in the WPS is indicated min preheat temperature 195°C (see QW-406.1)

-300 °C max. interpass temperature in the PQR is o.k. provided that in the WPS is indicated max. interpass temperature 355 °C (see QW-406.3).

-The required PWHT acc. to UCS-56 is min. 204 minutes at min. 650 °C. That means the above stated PWHT meets the requirements of the design code and QW-407.1. Please note the above PQR (85 mm) qualifies the base metal thickness up to 200 mm. For this maximum thickness PWHT min 5 hours and 45 minutes at min 650 °C is required. For the above thickness impact test are required and therefore in addition QW-407.2 is applicable. In the case of repair after PWHT an additional PWHT is required. But acc. to QW-407.2 the PWHT of the PQR has to have min. 80% of the aggregate holding times. Some manufactures performed therefore a PQR with 3 times of the required holding times to qualifies two repairs (some client specification to). A longer holding time has an influence of the toughness. But if the impact values of the PQR meet the code requirements of UG-84 you have evidence that this PQR is o.k.

But this is only the formal answer to meet the requirements of the code.

Here some technical aspects:
Appendix R is only a recommendation. But according to my experience and in compliance with steel and consumables manufactures recommendation the temperatures are to low especially for higher thicknesses ( http://www.boehler-welding.com/english/files/Weldingguide_ENG.pdf e.g. search for 13CrMo45 which is similar to Gr.11 ). Your preheating of 250 °C is the common used preheating temperature for Gr. 11 and Gr. 12 steels. The interpass temperature is also o.k.

Your postheating (350 deg C for 4 hr) is a heat treatment for hydrogen effusion (soaking) immediately after welding and is recommended in case of increasing thicknesses and high restraint welds to avoid cracks (acc. to my experience for the thickness above it is absolute required). This heat treatment is also required after each welding stop in which case the preheat temperature will not maintained. There are no code requirements in the design code for this postweld heat treatment. The above parameters are common used.

_________________
Kind regards,
Juergen Fleischfresser

Osama,

”Question 1:
How to PQR stated temperature i.e. 680 deg C and time i.e. 16 hr.”

Answer: UCS-56(b): "Except where prohibited in Table UCS-56, holding temperature and/or holding times in excess of the minimum values given in Table UCS-56 may be used". This means, you can do this 680 deg C 16 hr. heat treatment on your production weld joints.

However, the most important thing is to determine if you need to do impact testing. I understand that your material needs to be impact tested per UCS-66. Your PQR needs to be impact tested as well. If so, you need to follow all essential and supplementary essential variables listed in Sect. IX, including QW-407.2 which means that PWHT of your PQR coupon needs to be essentially equivalent to that of the production weld. So, you not only can, you need to do that 680 deg C 16 hr PWHT on production welds.

Question 2:
How to review above a,b and c points according to ASME Sections as i have checked Appendix R i.e. R3 (ASME Section VIII Div 1), it only mentions 121 deg C preheat temperature for P No.4 and Gr.1.

Answer: Appendix R is nonmandatory. Section IX is more important.
Again, as soon as impact testing is required, you need to follow Section IX, QW-406.2: “A change in the maintenance or reduction of preheat upon completion of welding prior to any PWHT”. This means, you need to do substantially the same pre-heat and post-heating as indicated on the PQR.

So, I would say, the core problem is impact testing. There is one more potential problem, per UG-84(i), you may need to do production impact testing as well, and this is not a good thing. Also, people are not stupid and may be they have chosen that high temperature pre-heat and post-heating to prevent Hydrogen cracking after welding of this thick part. In general, this is not a simple situation, you are facing metallurgy and welding science.
A competent technical advice from experience professional is highly recommended.
Good Luck.

Nick, AI from Oregon

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AI-OR-US

Osama,

In addition, because you are talking about PWHT of P-4 material, it is very important to follow UCS-85, HEAT TREATMENT OF TEST SPECIMENS.

Thanks,

_________________
AI-OR-US