What is the Governing thickness? 1

[bmoorthy]

Hello All

SA 350 LF2 flange (At the forging shop) is found to have discontinuity (16" 900 #) on the Flange OD. The Discontinuity cannot be left un attended. The forging has to be saved (Insted of rejection) by repair welding.

The location of the defect is 17mm from the OD and the depth of the defect is 13mm.

What should be considered as governing thickness "T" for the purpose of qualifying the weld procedure? Which clause of ASME SEC VIII and ASME Sec IX address such repair issues.

Governing thickness for the purpose of repair of Material is not found in ASME Sec VIII Div 1. UW 40 addresses weld repair and not the base material repair.

 

[metengr]

The governing thickness in a component repair is the excavation depth to remove the defect, not the thickness of the component or pressure boundary. In this case, this is a partial penetration weld repair. SA-350 addresses weld repairs (See section 10) and reverts to ASME B&PV Code, Section IX guidelines for qualification of a procedure and welder.


For weld procedure qualification, I would use a 1.5" thick coupon to allow for 8" base metal and 8" weld deposit thicknesses. Otherwise, you could use a 1.5" thick coupon and limit the weld groove depth to the depth of the defect.

 

[bmoorthy]

Thanks Metengr.

What you said is common sense. But which clause of Sec IX deals with the repair "T"

Now the Forging shop would certainly want to have the PQR done before hand and keep it ready so that when ever and where ever repair occurs they can start the repair.

If the repair had occured at 10mm from OD and the excavation is till 13mm then, qualifying a procedure in a 1.5" plate would not support the repair, if we perform PQRT with 1.5' plate.

Does it mean the manufacture shall have 3 PQRs, one for 1mm to 5mm and one for 5 to 16 and one for thickness from 16 till 8"? to attend the full range of thickness.

 

[metengr]

Section IX does not deal with specifics on weld repair only requirements for welder and weld procedure qualification. Most material Specifications like to reference Section IX for qualification of welding procedures and welders. Specifics about repairs, regarding permissible depth based on wall thickness are addressed in ASME Section VIII, Div 1 for pressure retaining items.

Getting back to your original post, the 1.5" thick coupon used for weld procedure qualification will allow for qualification on base metal up to 8" in thickness. This is why I suggested using a 1.5" thick, butt welded coupon. This way, your base metal thickness and weld deposit thickness are both good to 8" qualification with this WPS.

 

[metengr]

As a side note, if your repair depth exceeds 1.5", go to a thicker coupon like 2" to qualify the procedure in acrodance with ASME Section IX. The mm conversion always throws me off base.

 

[bmoorthy]

The governing thickness for repair is not addressed in ASME Sec VIII Div 1.

There is only 1 place in ASME sec VIII Div 1 that deals with the governing thickness for repair, which is in UW 40, which deals with PWHT.

Hence i was checking whether there are any interpretations in Sec 2 or in section VIII.


Thanks

 

[bmoorthy]

If the depth of the repair is the depth to be considered for "T" then consider the following situation

if there were a 100mm thick plate and if there is suface flaw say 2mm deep and the purchaser agreed for repair, then is it necessary for the plate manufacturer to qualify in 5mm thick plate. Does it not look funny.

I think the matter is not addressed by either sec 2 or in section VIII div 1.

 

[metengr]

Let me try this approach to help you, IF the depth of the flaw and removal exceed the minimum wall thickness of the pressure boundary, weld repair is required. Weld repair is required to assure compliance with the material Specification requirements for defect removal and Code of Construction requirements for minimum wall thickness.

The WPS for weld repair should be developed based on the base metal thickness (100 mm) AND the weld deposit depth (any thickness at or below 100 mm). All you must do is to assure that during qualification of the welding procedure (using ASME Section IX requirements), the actual base metal thickness you are welding on falls within the range of the qualified base metal thickness in the WPS AND your depth of weld repair falls within the range qualified for weld deposit thickness in the WPS. PWHT or other essential variables like preheat must be included based on the Code of Construction (ASME Section VIII, Div 1).

 

[GenB]

You will have to run test which covers the intended thickness of the material welded, in you case the range of say 1/2 in through 8 in can probably be common, so you may need to do 2 or possible 3 test plates.

You are not addressing the need of ASME certification/stamping to be allowed to weld on forgings. you have to look at the ASME specification for the type of flg you are forging toi see about repaiors by welding and if you are allowed to weld on the finished flange (repair by welding). at one time China mfrs were sending repaired flanges not only welded by filled with plastic/epoxy so they are banned from using this flanges in ASME construction... careful...
genb

 

[stanweld]

ASME Section IX does not deal with the repair depth in terms of procedure qualification. For impact tested materials the thickness T referes to to the base metal thickness; not the deposited weld metal thickness. Per QW-403.6 the 5/8" to 2T limits pertains to the base metal thickness. If the flange thickness is greater than or equal to 5/8" (16mm) qualification on 1 1/2-inch thick coupons will qualify you to weld on flanges having a thickness range from 5/8" to 8-inches. All repair weld depths up to 8" are qualified.

 

[bmoorthy]

Thank You all of you.

 

[Tmoose]

We have been struggling through the manufacturing of some large cylindrical parts made of 2214 aluminum and similar sized and shaped parts made of fancy Nitronic stainless steel.

We had a lot of weld testing and qualification done using weld coupons thinner than the actual parts, but with thickness that is "permissible" according to codes.

Now that we are having problems the bigh priced consultants are saying "well, sometimes your weld tests must match the thickness and restraint of the real parts."

 

[metengr]

Time to hire other less pricey consultants!