API 650

Date 01-06-2011 21:05

I really appreciate your interest. We are building three identical carbon steel (A516 gr.70) sulphuric acid storage tanks. The design metal temp is -10 degrees Celsius. However, I'm not sure how this applies to the question so I will provide the code material from API 650: Number and location of radiographs- 8.1.2.2 The following requirements apply to vertical joints:
a) For butt joints in which the thinner plate is less than or equal to 3/8" thick, one spot radiograph shall be taken in the first 10 ' of completed vertical joint of each type and thickness welded by each welder.
b) For butt joints in which the thinner plate is greater than 3/8" thick, but less than or equal 1"in thickness, spot radiographs shall be taken according to item a.

Each welder must be "qualified" to each thickness of metal he welds, not? Seems pretty simple, but I am notorious for missing the forest for the trees. Not to mention the previous inspector did not cover his bases(10 shots missing by my count) and the first tank is complete and supposedly ready for testing(luckily it's - 30 degrees celsius here), in the spring now apparently.

By dbigkahunna (****)

Date 01-07-2011 00:33

Be sure you have API 650 11th edition. Figure 8.1 shows the number and location of the required radiographs.
Each welder has to have a shot taken in the vert on the first 10 feet of weld they complete. This only applies to welders qualified for butt welds. Some tank welders only weld on the floor. So their inches are not included. Only welders welding on the shell. If you have 4 welder doing verts, 4 of the random shots are to be taken in the first 10 feet. After that, radiograh 3 is just taken. If you have 10 verts in the tub ring with the thickness you stated, you have 2 butt shots and one intersection. Shot 5 is fixed at the bottom, and shot 4 is fixed at the intersection. Shot 3 is where you get your random shot. On the horizontal, shot 2 is a random shot based on length of the weld. It is random again based on one shot for the first 10 feet for each welder then one shot in each 200 feet. And that is not for each welder.

By azphiks (*)

Date 01-07-2011 12:39

I agree with everything you said, however each coarse(ring) of the shell is thinner as we go up. Therefore, as I read it, each welder must again be qualified in the first ten feet of each thickness. Yes? And thank you

By dbigkahunna (****)

Date 01-07-2011 14:02 Edited 01-07-2011 14:15

Maybe it is the way you are defining it, but the welder is NOT qualified by the thickness. A random radiograph does not equal qualification.
Under 8.1.2.2(a) <3/8 inch one shot is to be taken in the first 10 feet for each welder for each thickness. This applies to the thickness 3/8 and less. and only applies to the verts. You do not apply this to the thicker courses.
For the courses >3/8 inch you go to (b)
Do not read into (a) to apply it to (b)
The shots for the welders 10 feet are NOT in addition to the 3 random shot. You do not take a random in the vert plus the shots for the welders. You shoot your randoms to satisfy the 10 feet per welder
On the courses that are thicker than 3/8 you radiograph all the intersections, PLUS the twp additional places one right above the bottom and a spot in the vert
If the tub is 3/4 and the second ring is 5/8 you do not shoot additional spots for the 10 feet per welder. As I understand this because the thinner plate does not have the additional spot shots (3 and 5) that are taken on the thicker plates. When going from 3/8 to 5/16 with say 3 welders you would shoot 3 additional for the first 10 feet per welder but when going from 3/4 to 5/8 you would not because you have the additional two shots. The intersection and a random spot in each vert or the bottom shot on the tub.

By azphiks (*)

Date 01-07-2011 14:39

I'm making a mountain out of a mole hill here. I have done everything required, possibly a bit more but our NDE get paid if they are working or sitting in the truck. One last thing, not to pick but to be sure. You say "Do not read into (a) to apply it to (b)" but my code says "b.For butt-welded joints in which the thinner plate is greater than 3 / 8 " but less than or equal to 1 " in thickness, spot radiographs shall be taken according to item a. In addition..." To be clear, we are only taking three random shots in the bottom coarse, but we have two coarses above the foor-to-shell that are 1 / 2 " -I think we are on the same page. Thanks

By dbigkahunna (****)

Date 01-08-2011 01:06

On the 3/4 tub you will be taking spot randoms on every vert. If you have 6 verts you will be taking a random on each vert. Plus a shot on each vert above the shell to bottom weld plus the intersection.
You will then take a random on each vert in the second course and the intersections and third course and intersections. Additional vert randoms are based on (a) one additional spot radiograph in each additional 30m(100ft) plus all the intersections
When you get into the courses =< 3/8" you go to (a).
Are you the fabricator or the owner rep?
If you are the fabricator and do not have a correct shot sheet for the project, you need to be about 6 feet up your engineering department and project managers backside, If you are the owner rep and the fabricator has not supplied you with a correct shot sheet you need to be 6 feet up the project managers backside to get you one. Some contractor want to play reindeer games with this. I can calculate the number of shots needed, but I want to see the fabricators shot sheet. This is part of the QC package that the fabricator should supply with the pre-construction package.