Does LTCS Weld Joint with above 20mm thickness need PWHT?

[raf143]

As per ASME B31.3 Table 311.1.1 PWHT shall be performed for the Weld Joint with Base Metal P Number (P) 1, Weld Metal Analysis Number (A) 1, and above 20mm thickness. LTCS Pipe A333 Gr.6 Welded with Consumables ER80SNi-1 and E8018-C3 has P Number (P) 1 and Weld Metal Analysis Number (A) 10.

Please Confirm Whether PWHT is to be performed for LTCS weld joint above 20mm thickness with base metal P Number (P) 1 and Weld Metal Analysis Number (A) 10?

 

[pradipgoswami]

As per B-31.3, Table 331.1.1 PWHT would be required if the thickness of C-Mn steel weld exceeds 20 mm or 3/4".
Looking the welding consumables used it looks to me , the design requirements involve NACE,MR-0175, which calls for a maximum weld and HAZ hardness of 22HRC. If the above hardness levels can't be met in as welded condition, then PWHT is a must.
A combination of ER80SNi-1 and E8018-C3 welding consumables,would not give weld hardness of less than 22HRC in as welded conditon.
Hence looking at all the pros and cons, [highlight #FCE94F]welds should be subjected to PWHT[/highlight].

Thanks.

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

 

[raf143]

thanks Mr. padip Goswami for your reply

As per B-31.3, Table 331.1.1 PWHT would be required if the thickness of C-Mn steel weld exceeds 20 mm or 3/4".
this is only if 'A' number is 1. in this case 'A' number is 10. So what about the influence 'A' number in Table 331.1.1 of B31.3?

 

[stanweld]

Per B31.3, PWHT is based on base metal, base metal or deposited weld metal thickness. A-No. is inconsequential.

 

[sahavas]

thanks stanweld for your reply
you replied 'A' number is inconsequential. if it is inconsequential, then why B-31.3 table included 'A' number. how can I make sure 'A' number is inconsequential?

 

[pradipgoswami]

Governing Thickness(Clause 331.1.3) for PWHT in B31.3 code is the nominal thickness at the weld joint (Base Metal). Additionally, the intent of adding "A No" in Table 331.1.1, is to ensure the minimum chemical analysis of the weld metal to be used matches the base metal chemistry, i.e A No 1 matches P No 1

In many instances LTCS base metals are welded with Nickel containing fillers/electrodes. However the PWHT (Holding Time & Temp) criteria is based on the BM.

If you look though Table 331.1.1, the PWHT Temp range is almost same for both P1 base metal and A10 weld consumable, with minor variations in holding time.

Holding time could be important if the design specification calls for a hardness restriction or specific impact requirments.

Thanks

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

 

[birken]

Following B31.3 any P No.1 material having thickness greater than 20 mm requires heat treatment irrespective of which filler is used to weld. Like if you weld plain carbon steel with stainless steel with groove joint thickness greater than 20 mm, you have to perform PWHT (for the CS side) in order to meet the requirements of the construction code; although you would be using either E309 or ENiCrFe-3 as the filler.

Birken

 

[stanweld]

B31.3 does permit the Owner/Designer the ability to make exception to the PWHT requirements per 331.2.2.