Please find below, my best reply to your demand.
For pressure vessels, I use 3 times the material thickness between the edge of welds or 1/2", whichever is larger. To avoid this situation, I always excluded the option of extending the nozzle necks for any reason (that's the typical place to use the allowance of minimal distance between butt welds, when the fabricator made a mistake).
I'm not aware of any similar restrictions for butt welds on structural steel work.
Best regards,
gr2vessels
Here's anothe piece of related info. Per ASME IX, UW-9(d)... Except when the longitudinal joints are radiographed 4 in. (100 mm) each side of each circumferential welded intersection, vessels made up of two or more courses shall have the centers of the welded longitudinal joints of adjacent courses staggered or separated by a distance of at least five times the thickness of the thicker plate.
Hello, Thank you so much for your replies. I had a problem and couldn't check the replies until now.
All of the replies were great, but my problem is this: sometimes our subcontractors make some mistakes in cutting, ... and it causes the weld joint distance less than 30 or 40 mm. then they ask me to accept that and I don't know what to say, because there is nothing in AWS D1.1.
Can you help?
A classic case of, "I cut it twice and it’s still too short!"
AWS D1.1 (as do other AWS structural welding codes) lists prequalified joint details. Included are the root openings, both nominal and as fitted.
You add the nominal and the as fitted tolerances to find the minimum and maximum root openings.
If the root opening exceeds the maximum permitted, you are allowed to deposit additional weld metal on the root face, grind or machine the member to the proper shape and then fit the members together.
The maximum allowable "build up" on the groove face is twice the thickness of the member, not to exceed 3/4 inch (20 mm). That would give you 40 mm if you build up both members. See AWS D1.1, paragraph 5.22.4.
If the member is still too short, it is time to ask the contractor to replace the member or to consider UT or RT in addition to the required visual examination of the extra weld deposit.
For most applications the addition of weld deposit to the groove face prior to fit up is not going to be detrimental to the serviceability of the member or weldment. After all, the weld deposit will be as ductile and as strong as the filler metal used which is often better than the base metal being joined.
It would be wise to require the offending contractor to qualify the welding procedure he intends to use if he requests to exceed the limitations of AWS D1.1 for allowable root opening and correction by depositing additional weld metal to the face of the weld groove prior to fit up. The conditions of "prequalification" have been exceeded, thus qualification by testing is necessary. Charpy impacts may be warranted if the base metal had impact testing imposed as a supplementary test when it was ordered or if there is a concern because the member is a component of a non-redundant assembly. Make sure that the root opening used in the procedure qualification test is at least as great as that experienced in production. The testing should also be restrained to simulate the restraint encountered in production.
Do not allow the welder or the welding procedure to permit "closing" the excessive root opening once the joint is assembled by welding using the typical "layering" technique. In the case of T or corner joints, lamellar tearing can result. Assuming backing is employed, a better technique is to reduce the root opening by depositing the weld on one of the two groove faces until the root opening has been reduced to an acceptable dimension. Do not weld the backing to both members, only weld it to the member that is being built up to correct the root opening. Once the root opening has been corrected, allow the joint to cool (and contract) to the minimum preheat temperature and then complete the joint using the typical layering method.
