|
Hi cmbb, Depends on who's spec's your testing for AWS or API and the job requirement spec's. Both qualification requirements are close with subtle differences so I will include general information that apply's to both specifications. Although I'm a AWS CWI, I never certified thru API as an inspector and I'm lacking through knowledge of there codes.
Qualification Overview:
The most common test position is the 6G, ie; 6" pipe fixed at 45º +/-5º, with a 60º opening, with either a open root or backing plate, as it qualifies the welder for all positions on both grove and fillet weldments. This also quickly weeds out the "crack of dawn" welders as welder skill is shown at the root pass that is visual inspected after compleation. After tack up has been completed, a visual inspection is done of the joint prepration, ie; correct root opening, land thickness, tack placement and joint cleaness. If you pass the visual root test, then your allowed to proceed to complete the test too the cover pass. Once the cover pass is completed then once again a visual test is preformed and there it is decided if you will be allowed on too the inspection stage of destructive testing (ie; cupon bend testing) or nondestructive testing (ie; X-ray, ultrasonic, dye penterant or magnetic particle).
Test Overview Requirements 6G test:
Test pieces shall be cleaned of all forgien material (ie; oil, grease, rust, scale, paint) from 1" of either side of the center line of the weldment. No more than 1/16" of base metal shall be removed during base metal preperation. (Notes:) If allowed by the WPS (Welding Procedure Specification) a 60grit x 1" emery paper wheel (flapper wheel) on a die grinder works well for this task. Watch using a air die grinder that oil does not get on or close too the weld zone. Code does not specifiy what tools are to be supplied other than normal tools that are required in normal field use. I've had great tools supplied during the testing phase (there "if" you ask) but not supplied at the jobsite and then I've been on tests where only a grinder was supplied at the testing stage with very little more available to work with at the job site. Do NOT forget to clean the inside of the plate/pipe or the backing plate collar. For open root weldments, test pieces shall have a land thickness of 1/8" maximum with a maximum 1/8" root opening. No root opening shall exceed 3/16" in width.
(Notes:) What has worked well for me is a 1/16" land with a 3/32" root opening with using 1/8" 6010 or 7018 electrodes with the correct heat setting of approx. 110amps. 3/32" electrodes will not be allowed for root passes as AWS specifiys a welder requallification is needed for a change in electrode diameter increase of more than 1/32" but not vice versa. Most welder qualification procedures will detail what electrodes are allowed for the root, inner and cover pass welds. For a root opening with a backing plate, shall a maxmimum land of 1/8" and maximum root opening of 1/8" for 3/8" plate thickness. No root opening shall exceed 3/16" in width. (Notes:) What has worked well for me is a 3/32" land with a 3/32" root opening with using 1/8" 7018 electrodes with the correct heat setting of approx. 125amps. 3/32"electrodes will not be allowed for root passes as AWS specifiys a welder requallification is needed for a change in electrode diameter increase of more than 1/32" but not vice versa. Test pieces shall be tacked welded at the 3, 6, 9 and 12 o'clock positions with each tack being under 1/2" in total length. (Notes:) At this time a visual inspection is preformed of the test piece. Minor flaws of the code will be allowed to be fixed during the test by most weld inspectors, however there are inspectors that are on there own "head trip" and will "look" you out (stop the test). If that happens ask to see the inspection supervisor as most of us will give some lee way as we all know how difficult the test enviroment can be. We also are aware of the job market demands of the contractor so we will be (slightly) more lenient at times than at other times. The best way to handle any inspector is to treat them like you want to be treated, don't ask for favors nor expect them but don't kiss up either as this makes most inspectors watch closer. AWS code requires one CWI (Certified Weld Inspector (4yr requirement)) on the jobsite with numerous associate (two year requirement) weld inspectors working under the CWI. (Notes:) Preclean all tacks and passes very well paying close attention to total slag removal. On the only test I failed (1/3 of the test) was because I failed to clean the slag completely on the root pass and that slag trail went clear thru the weld zone to the cover pass. Looked kinda of neat when it broke on the edge as it gave great detail of the slag entrapment. I was allowed to retest as my root and cover pass looked well. (Notes:) It is very critical to hold a stable arc length. The more stable arc length the easier the root and other passes will be. Start each pass two to three rod diameters staggered as this allows for any missed minor flaws to be corrected by the next hot pass. To make a smooth transistion between stops and starts, start the rod back about 1/4" from the end of the weld in two quick 360º circles then move into the weld zone.
(Notes:) Open root is best done buy starting two rod diameters back on to a tack or previous weld as this lets the electrode heat stablize before entering or making the "keyhole". It's called a keyhole as thats just what it looks like, a old time lock key hole or tear drop. Hold the rod in the keyhole until the bottom of the keyhole is filled then more forward. Now you can see where correct electrode amps are required with a stable arc length. Too hot and the keyhole size increases and can't be filled. Too cold and you can't form the keyhole or lack of penatration. A straight steady forward bead I found is best under most conditions. Your a little nervous, no problem, just grab ahold of the electrode close to the end where it's hot and you will soon smooth out.
On open root welds you are allowed 1/16" concave and 1/8" convex of the root face front and back when comparred to the base metal. A 1/64" undercut is allowed at the toe of the weld and on both the root and cover pass.
(Note:) It's best too not make a inspector take out a gauge to measure this defect! On root welds using a backing plate I like holding a steady arc length without weaving while paying close attention to the land edges for complete weld metal fill. (Notes:) Now that the root pass been completed, I usually add approx 15amps to complete the inner pass welds as well as the cover pass. Stagger all stops and starts as this helps prevent cold lap and slag entrapment. Watch the base metal groove edges for a cover pass guide line. I like using 1/2 of electrode diameter overlap on the edge as this makes for a good tie in without undercut. On a test weldment I strongly urge stringer beads for the cover pass as theres less chance for a defect. On the other hand if theres a bunch of experienced pipe welders present then your gonna get laughed at running stringer beads for a cover pass. The test cupons, if required, are cut out of the 2, 4, 8 and 10 o'clock positions being 1-1/2" finished width. That being said, then on destructive testing, make sure these areas are flawless as possible. T_Bone
| 
