By Lawrence 
Date 05-14-2010 23:20
Edited 05-14-2010 23:25
Last question first.... A weld becomes a failure when the governing code says the discontinuity is large or severe enough to be recorded as a defect. It can be that simple.
There are codes and standards aplenty!
It is alot easier to simply hold the welder to a published code criteria or curriculum standard... At least in my opinion.
If a student learner can *repeatedly* perform welds that pass a code criteria I can't see any justification to hold that student back because they dont make welds pretty enough.
For Carbon steel above 1/8" I use AWS D1.1 For steel below that thickness I use either D1.3 or D9.1 depending on the process.
For Aluminum I use AWS D1.2 or D9.1 depending on the process.
For Stainless AWS D1.6 or D9.1 depending on the process.
Now... When you say "...This numercial mark is presently based on a subjective visual exam by the instructors... " Are you saying this as an instructor or as a student??????... Because it makes a big difference... If you are a student it may only appear subjective from your perspective... It may be that your flaws are so severe that the instructor has not introduced code compliance and is only dealing with gross trends... This usually changes as the learner begins to improve.
If you are a teacher than we can have a real discussion about objective evaluations and how much easier your life will become if you find a way to get your inspections to comply to a code.
Edit:
I keep the code book, steel rule, 10 Power, optical comparitor, fillet gauge and undercut gauge on my inspection desk with the code books right next to them. I quit being the bad guy a long time ago... Its the dirty, mean code book that says you have to do it again. Their can be no arguments if student learners do the inspections and measurements right along side the instructor.
In my experience, some type of subjective grading system is used during training last school I was at it was a 100 point scale. When doing actual destructive testing for welder qualification it was pass/fail. Either the weld MET the criteria and passed the destructive tests or it failed the criteria. no wiggle room, and out in the real world no one is gonna pay extra time to go make the weld bead look pretty if it's already passed all the code requirements (unless of course this is a cosmetic weld)
The grading system was used to set a standard higher than code criteria such that a 100% weld would without a doubt pass a qualification test every time. The qualification tests were merely the official side, and didn't need to be double graded.
As far as formal criteria, none existed at where i was. It was subjective to the teachers but as it was only an internal teaching tool it had no weight outside of the classroom. Therefore we didn't need any documentation that went as far as showing weights for different types of deductions, severity of defect etc, the teacher used their own judgement and knowledge to determine the grade. under our system a student would have to repeat the weld until the instructor thought it was sufficient to pass this usually equaled around an 80% grade. A set of crown height and fillet gauges were provided so welders could check their own bead dimensions, and they were supposed to be within code tolerance to pass.
the point of training wasn't to split hairs in terms of what passed/failed but hold students to a standard higher than the codes such that when code work was done the goal posts seemed wide. We couldn't get away with cold lap, or undercut on any welds even though they would easily be code compliant. If
Depends on how training is set up.
I grade go / no go on individual welds. However the "go" standard is simply "my statisfaction" for about the first year.
Even though we are a welder training program, initially the welds themselves are somewhat incidental to other assignment tasks such as cutting and bevelling with a torch, measuring, locating and drilling bolt holes, prepping and fitting connections on beam and tubes, looking up operating parameters on the internet, setting up and operating the common manual and semi-autmatic welding processes, gouging and backgouging with an air arc, and operating various equipment like saws, an iron worker, clamp on pipe beveler, etc. This is all first quarter stuff.
The assignments are challenging right off the bat. Among other things the first quarter includes a beam column connection, AC TIG, 2G open root pipe, and butt welding square tubes 5G and 6G with V and bevel grooves. All of those except the AC TIG are done outside, and the students have an overhead crane to move their assignment components around.
The main emphasis early on is on the ability to prep and fit the joints properly.
During this time the standard for the welds may start out as simple as fill the joints completely, to the size specified, without visible slag inclusions, and with a reasonable profile for the current level of experience. As a student advances in the program the "go" criteria becomes more and more demanding, eventually reaching welder qualification standards. Training eventually includes assingments on the D1.1 visual acceptance and WABO welder qualification testing criteria.
I wouldn't want to get into "grading" welds myself other than pass / fail.
