100% Xrays
100% Xrays
(OP)
Does any one have experience with a change in NDT for pipe welding in a contract by changing the % x rays from initial 15% to 100% aasked by the client.
In our case due to the diameter of 48" and 36" the hidrostatic tests were not practical and the client decided this change. But... for us, the contractors, I feel this will increase our probability of finding more refused welds, and of course bring more costs?
Would you charge more if you were to do 100% instead of initial 15%, (ASME B31.1). Not by the price of Xrays but because of the probability of more refusals?
In our case due to the diameter of 48" and 36" the hidrostatic tests were not practical and the client decided this change. But... for us, the contractors, I feel this will increase our probability of finding more refused welds, and of course bring more costs?
Would you charge more if you were to do 100% instead of initial 15%, (ASME B31.1). Not by the price of Xrays but because of the probability of more refusals?





RE: 100% Xrays
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: 100% Xrays
36" and 48" sounds more like transport pipeline than process - however:
Cuyanausul, what stage of fabrication are you at? If completed then this could cost you plenty, not just in increased inspection costs but also in additional repairs that the client contractually was prepared to allow go undetected by stipulating 15% random radiography. If the pipework is still being fabricated, then let all involved know that 100% radiography is going to take place and revise your inspection and test plan to include review of all fit-ups, tacks, and roots. At least you will minimise further repairs.
The client's designer must have known beforehand the pipe diameters and the feasibility (or otherwise) of the hydrotests. If B31.3 para 345.1(c)(1) or (2) is applicable then para 345.9 applies. This clearly states that circumferential, longitudinal and spiral groove welds not subjected to hydrostatic or pneumatic leak tests shall be 100% radiographed or 100% ultrasonically tested. Plus all structural attachment welds shall be either penetrant or magnetic particle tested. The client should have contracted the fabricator for this work prior to fabrication start-up and allowed for the increase in quality costs concomitant with a change from 15% random to 100% radiography and the extra surface NDT.
15% random examination acts as an aid to quality control but it does not pretend to guarantee that all welds will be radiographically acceptable. The owner should realise that there is potential for significant discontinuities to exist in welds that were not radiographed. Also random radiography is intended as a feedback mechanism to allow the fabricator to take corrective action on discovering weld quality is not meeting the acceptance criteria. It is not intended that random radiography be performed after completion of all welding, as no corrective action to improve continuing welding will have taken place. If random radiography at this point shows that repairs are required it can only throw doubt on the quality of the remainder of the welds. In addition each welder is only allowed 2 repairs. On discovery of a 3rd rejectable weld all 100% of his work will have to be radiographed - a costly process compared to pulling a welder off production work on receiving his second repair and not being able to demonstrate his ability to produce sound welds.
I think the answer to your question is "yes". Extra repairs of defective welds will obviously involve extra costs for which the fabricator was not contractually responsible. However if you are fairly confident of your fabrication, welding and inspection procedures with a skilled and committed work force, I would be more worried about the cost of the 6 fold increase in radiographic coverage - especially on the size pipes you are talking about. X-ray film does not come cheap!
RE: 100% Xrays
I apreciate both replys, I came to this project at 80% completion, and I worry about the quality, the inspector we have is not what I am used to have, I even had to dismiss a 50 years old welder!
One more question, is it that dangerous to do an air pressure test instead of hydro?
Some pictures at:
www.geocities.com/simanmecanica
RE: 100% Xrays
RE: 100% Xrays
RE: 100% Xrays
RE: 100% Xrays
.... hidrotest wasn´t feasible because the pipe was designed for steam, not water so the supports won´t stand more weight,
RE: 100% Xrays
RE: 100% Xrays
Tough one for US soccer team tonight against a Ghana team revitalised by their last win!
Nigel Armstrong
Karachaganak Petroleum
Kazakhstan
RE: 100% Xrays
RE: 100% Xrays
RE: 100% Xrays
On other diameters, we are Xraying 1st stage 15% acording to B31.1 ........