Hey all,
I'm having a bit of an issue with what i believe to be a glaringly omitted requirement in D1.4: 2011 (as well as D1.1 and D1.6, and other codes as well). I recently qualified a procedure using A706 rebar to A572 Grade 50 per Figure 6.5(C), the qualification passed mechanical and macro tests and we had no issues until our customer's inspector showed up.
The inspector looked through my documentation and found something he didn't like (all documents were downloaded directly from
https://app.aws.org/technical/sample_forms and filled out accordingly, mind you). He said that the contact tip to work distance/electrode stickout (CTWD) isn't listed on the WPS or PQR, to which I replied that it's not listed as an essential variable in Table 6.2 nor is there a field on the documentation in which to specify it... Come to think of it, I've qualified a number of procedures and D1.1, D1.4, and D1.6 don't classify CTWD as an essential variable, in fact, the only mention of it i can find is in the D1.1: 2015 commentary:
C-4.8.1 SMAW, SAW, GMAW, GTAW, and FCAW.
Travel speed affects heat input, weld cooling rates, and weld metallurgy, which are important for the HAZ, for fracture toughness control, and for welding quenched and tempered steels. Proper selection of travel speed is also necessary to avoid incomplete fusion and slag entrapment. Electrode extension or contact tube to work distance is an
important welding variable which affects the amperage as well as the transfer mode. At a set wire feed speed, using a constant voltage power source, longer electrode extensions cause the welding current to decrease. This may reduce weld penetration and heat input and cause fusion discontinuities. Shorter extension causes an increase in welding current. A variation in electrode extension may cause a spray transfer to change to globular or short circuiting modes.
It is important to control electrode extension as well as other welding variables.I know it's important and is a big player in heat input, but I would like to assert that keeping the transfer mode is more important than the near impossibility of physically measuring each welder's CTWD to within a 1/16"(insert other tolerance) for any given pass. It baffles me that AWS doesn't list it as an essential variable, the closest AWS came to it is mentioned only by inference through the following variable tables:
D1.1: 2015 Table 4.5 Item 14
D1.4: 2011 Table 6.2 Item 6
D1.6:2007 Table 4.1 Item 3.2
So the inspector is requiring me to add CTWD to my documentation even through there is no spot on the AWS form or specific requirement in clause 4.
What are your thoughts, should this be listed as an essential variable and why would AWS omit this in D1.4's (and other codes) WPS and PQR's documentation?
Thanks,
Scott