Weld defects - how much is too much?
Weld defects - how much is too much?
(OP)
I have a tank currently underconstruction, which has had about 35% of the Radiographed welds fail. These failures are only small in nature (but still large enough to be a failure obviously) so not huge gaping holes etc.
I have scoured API650 and some of ASME IX but can not find if there is anywhere that states how much failure is too much.
I 'feel' a third is too much, but I can't state that to the contractor...
Anyone got any suggestions?
I have scoured API650 and some of ASME IX but can not find if there is anywhere that states how much failure is too much.
I 'feel' a third is too much, but I can't state that to the contractor...
Anyone got any suggestions?





RE: Weld defects - how much is too much?
As an aside, how are you calculating the weld repair rate? As a percentage of the number of welds, or as a percentage of the total weld length? I suspect the former. Try the latter and see what rate you get then - your 'feel' might be assuaged somewhat.
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Weld defects - how much is too much?
The weld defect rate was simply calculated by a pass/fail rate on the x-ray, so not a percentage of total length. I will get someone to check out the % as a weld / x-ray length.
Most of the failures are inclusions, so will bring it up with the Contractor along the lines of quality improvement.
(Let's not get in to the whole woolly thing. It's NZ's West Island that has a Swagman jumping up with glee after a Jumbuck (in their 2nd national song)...)
Thanks
Dave
RE: Weld defects - how much is too much?
Joe Tank
RE: Weld defects - how much is too much?
While the owner may have the option of doing additional radiography, this should be included in the contractural requirements if applicable. Increasing the degree of weld inspection is normally an extra-cost item, even if the actual inspection is done by others.
RE: Weld defects - how much is too much?
When the Purchaser refers to API-650 in the bid documents, that already includes the provision for extra RT by the Purchaser. It's been in the Standard for quite a while now. It's nothing new. As you already know, things have gotten pretty bad by the time the Purchaser looses confidence in the weld quality being provided.
Joe Tank
RE: Weld defects - how much is too much?
What I meant by win -win was that both Owner & Contractor should have the mutual aim of maximising weld quality. If the Owner expresses dissatisfaction, a quality driven organisation should react to that situation in some way, perhaps by more preventive action. If the Contractor doesn't care, then the wrong Contractor was selected.
Repeated volumetric defects are indicative of two things:
1. Welder(s) with marginal skills
2. Poor welding inspection
So, the first thing I would be discussing with the Contractor is: which welders are producing the most defects and what is the Contractor going to do about getting them back on track or replacing them. Then I would ask why the welding inspector(s) is/are not picking up slag before more weld metal is deposited over it.
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/
RE: Weld defects - how much is too much?
I see your point, but too often the RT is done late in the job and it's sometimes too late to fix the problem and get to the win-win situation. At that point the Purchaser sometimes has to grab the bull by the horns and invoke his priviledge to conduct further NDE on the poor workmanship he now suspoects in in-place.
Joe Tank
RE: Weld defects - how much is too much?
RE: Weld defects - how much is too much?
Check out
7.3.2.3 Responsibility for starters. We also write an allowance of further testing in to our contract docs to make it clear.
(In fact we are actually performing 10% radiography of vertical welds, and 5% of horizontals in line with our Client's global specifications)
At this point in time we have 2 horizontal welds completed in one tank out of 6 times 3 tanks - so now if the opportune time to iron this out with the Contractor.
Thanks for your input guys - much appreciated.
Dave
RE: Weld defects - how much is too much?
The dreaded 7.3.2.3 is pasted below...
7.3.2.3 Responsibility
The Manufacturer shall be responsible for making radiographs and any necessary repairs; however, if the Purchaser’s inspector requires radiographs in excess of the number specified in Section 6, or requires chip-outs of fillet welds in excess of one per 30 m (100 ft) of weld and no defect is disclosed the additional inspections and associated work shall be the responsibility of the Purchaser.
Joe Tank
RE: Weld defects - how much is too much?
Your use of 10% radiography of vert seams may not be sufficient to meet API-650 rules. For example, all thicknesses greater than 1" required full RT
Joe Tank
RE: Weld defects - how much is too much?
RE: Weld defects - how much is too much?
These tanks are only babies - 30m (100')diameter & 16mm thickest strake (11/16"), so no probs with the full RT.
Ta
Dave