welding process question

[alammint]

Dear all,

Can Any body tell how to select welding processes for different thickness range as per ASME sections IX ,
i mean to say whats is the thickness limit for all welding processes as per ASME sections IX

Pls help me to get proper selection guide


thanks
Alam

 

[Duwe6]

Fairly simple in theory - hard in practice.
First; review the WPS's - procedures - that are available, looking for the material types and thickness ranges. Compare to the engineering drawings detailing the weld joints that need to be weldede up.

Second, go talk to your welding Superintendant/General Foreman. The location of the welds tig/GTAW [or any other process that uses shielding gas] is very difficult, time-consuming, and thus expensive and frustrating when the weld is at the top of a structure. The wind will be blowing all day and [mostly] all night. 'Stick' SMAW is a much better option. The wall thickness of the metal is an issue for weld production time - on thick pipe, after GTAW of Root and 2nd layer [Hot Pass] it is best to switch to a faster, more productive process, like SAW - submerged arc, FCAW - flux-core, or even SMAW - stick. Tig is very pretty, fairly forgiving of poor fit-ups, very high-quality, and very slow. Terrible choice for completing thick welds. Excellent choice for small socketwelds.

ASME allows you to be as unproductive and expensive as you wish. As long as your WPS covers the 'essential variables' of the welding joint - thickness, basemetal, process , filler, etc. - it is 'legal' to use that WPS [procedure]. But it may be very unwise and/or expensive. Ask your welding supervision; use their decades of experience as to which WPS's are 'practical' and which ones will be a very bad idea. After you sort out which WPS's match the work at hand.

It is fairly common to have to qualify a new WPS to cover the specific requirements of the welding required for a specific job, especially when the Superintendant/General Foreman tells you what will be the most economical way to make good welds.

 

[gtaw]

I like the advice given: speak with the welding supervisor or the welder if you have any questions about the "best" welding process to use in your facility.

If you are not working for the company actually doing the work, it may be best to allow the contractor to select the process that best utilizes the equipment they have available.

If you don't know, don't make any recommendation.

ASME is not a "cookbook." The ASME codes will not tell you "how" to do anything. If you can make a weld by rubbing two sticks together and the resulting weld meets the requirements of Section IX and the applicable construction code, you're good to go.

As a rough guide:

GTAW - all positions, thin material or root beads on thick materials. Gas shielded, not conducive to working "outdoors."
SMAW and FCAW - all positions, intermediate thickness through thick sections.
SAW - flat grooves, horizontal grooves with the appropriate ancillary equipment, flat and horizontal grooves, intermediate to thick sections. Use mostly in the shop due to the physical size of the equipment involved.

Best regards - Al