Preheat on Weld 1

[ajcousins]

Hello, I'm being asked if preheat is required to weld 5/8" thick CS beveled lifting lugs to the top of a 6" thick SA350-LF2 CS blind flange. My thoughts are no because it's just a bevel, full-pen weld on a 5/8" thick CS plate.

Can anyone give input on this? TIA!

 

[david339933]

What does your WPS say? For Sec. IX the WPS must be good for both the 5/8" and 6" thicknesses.

 

[r6155]

Requirements.
1) Preheat
2) WPQT shall include impact test
3) PWHT
Regards

 

[ajcousins]

@r6155, can you tell me where you got that information? ASME Section VIII Appendix R states that for P1 materials less than 1" join thickness that only a preheat of 50F is required. What is telling you to PWHT? This is for a 1/2" full pen weld.

 

What does "just a bevel" mean?

Follow the Code at a minimum.

Code also says use engineering judgment, and my engineering judgment says that the non-mandatory appendices for preheat give fairly light requirements that are non-conservative in some situations. Given the critical safety aspect of a lifting lug, some modest preheating would be prudent. Pay attention to moisture while you're at it.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[DekDee]

ajcousins,
Why do we preheat ?
The main reason is to slow the cooling to avoid adverse metallurgical changes.
Thicker the plate, faster the cooling.
It is not the 1/2" plate that needs the preheat - it is the 6" flange.
"just a bevel, full-pen weld on a 5/8" thick CS plate" - the Alexander L. Kielland oil rig disaster was caused by just a 6 mm (1/4") fillet.

 

[DekDee]

But it is only a small weld............

 

[r6155]

@ ajcousins
a) See SA-350 11.3 Repair by welding.
b) Can you send us a drawing?
c) I suggest preheat to 200F.

Regards

 

[Tmoose]

On our lifting lugs we also require some NDT throughout and after the welding process.

 

[weldstan]

Great post DekDee. That's why you preheat a 6" thick flange to 5/8" lug weld. Concentrate preheat on the 6" flang to prevent the quench effect from the thick flange.

 

But it is only a small weld...

Haha, famous last words! I've heard that one more than a few times.

On our lifting lugs we also require some NDT throughout and after the welding process.

The problem is that too many folks believe NDE is a mitigation for the risk of poor welding, in a similar way they think that stress relief cancels all the sins of bad welding. Just make a better weld in the first place.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[r6155]

Then a load test should be considered.

Regards

 

[SJones]

ISO/TR 17844

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.