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in-process NDE requirements question
- Thread starter eyec
- Start date
To maximize the full advantages of any NDT, it must remove unacceptable materials from the production stream as soon as possible. However, everything in life must consider the economic factors. It would be nice to utilize volumetric NDT at every stage of manufacturing, but it would be cost prohibitive.
Codes and standards specify the minimum level of NDT required. It may not be the optimum level of NDT; it is simply the minimum level of NDT required. It is good business for a manufacturer to institute a NDT system that utilizes resources wisely to maximize the profits earned on any single item produced. It the cost of materials and labor to manufacture a widget is low, the cost of expensive volumetric NDT is not cost effective. However, as the cost in time, materials, and labor increases, it becomes more cost effective to introduce various levels of NDT during production. Back to the basic concept of why invest time, money, and labor into a part that is not acceptable?
I had a project several years ago where I was called in by a client to perform a final inspection of a component that cost many thousands of dollars. I was called in because the client's engineer saw something that "didn't look right." The problem was the manufacturer failed to have complete fusion in the root bead of a groove weld. The incomplete fusion was only discovered when the completed weldment was heat treated and machined to very cloes tolerances. The bottom line was that there was no way to repair the deficient weld and still hold the tolerances required by the design. The unit was scrapped and a new one constructed. Again the same problem was identified after all construction, PWHT, and machining was completed. I suggested to the manufacturer that some in-process NDT, i.e., MT, be performed on the component that was causing the problem. I asked the manufacture how much time, material, and labor were invested in the component while it was on the bench being welded.
The manufacturer stated that it was worth about $50. I pointed out that at that stage, if a problem was identified, it could be easily repaired for minimal cost. His reply was that it was not required by the contract and he refused to do it.
Another unit was manufactured and it was rejected for the same reason as the first two units. Incomplete fusion in the root bead. I suggested that the welders be trained to use MT to inspect the root when they back gouged the groove. It inspection was not a required inspection, no report was required, the welder did not need to be certified to perform the in-process inspection.
Again the manufacture refused and another unit was manufactured and rejected at the final (required) inspection. Once again I made my suggestion and stated that the manufacture had produced several units at a cost of many thousands of dollars and not one was acceptable and in each case the cause of the problem was the same component. Finally he was in agreement that something had to be done before the company went broke. It was only after scrapping several completed units and the recognition that the manufacturer had lost nearly a million dollars were they receptive to in-process NDT. Sometimes there is no cure for "stupid".
Once in-process NDT was instituted at a cost of less than $25 per unit, there were no more rejects during the final inspection.
Best regards - Al
Codes and standards specify the minimum level of NDT required. It may not be the optimum level of NDT; it is simply the minimum level of NDT required. It is good business for a manufacturer to institute a NDT system that utilizes resources wisely to maximize the profits earned on any single item produced. It the cost of materials and labor to manufacture a widget is low, the cost of expensive volumetric NDT is not cost effective. However, as the cost in time, materials, and labor increases, it becomes more cost effective to introduce various levels of NDT during production. Back to the basic concept of why invest time, money, and labor into a part that is not acceptable?
I had a project several years ago where I was called in by a client to perform a final inspection of a component that cost many thousands of dollars. I was called in because the client's engineer saw something that "didn't look right." The problem was the manufacturer failed to have complete fusion in the root bead of a groove weld. The incomplete fusion was only discovered when the completed weldment was heat treated and machined to very cloes tolerances. The bottom line was that there was no way to repair the deficient weld and still hold the tolerances required by the design. The unit was scrapped and a new one constructed. Again the same problem was identified after all construction, PWHT, and machining was completed. I suggested to the manufacturer that some in-process NDT, i.e., MT, be performed on the component that was causing the problem. I asked the manufacture how much time, material, and labor were invested in the component while it was on the bench being welded.
The manufacturer stated that it was worth about $50. I pointed out that at that stage, if a problem was identified, it could be easily repaired for minimal cost. His reply was that it was not required by the contract and he refused to do it.
Another unit was manufactured and it was rejected for the same reason as the first two units. Incomplete fusion in the root bead. I suggested that the welders be trained to use MT to inspect the root when they back gouged the groove. It inspection was not a required inspection, no report was required, the welder did not need to be certified to perform the in-process inspection.
Again the manufacture refused and another unit was manufactured and rejected at the final (required) inspection. Once again I made my suggestion and stated that the manufacture had produced several units at a cost of many thousands of dollars and not one was acceptable and in each case the cause of the problem was the same component. Finally he was in agreement that something had to be done before the company went broke. It was only after scrapping several completed units and the recognition that the manufacturer had lost nearly a million dollars were they receptive to in-process NDT. Sometimes there is no cure for "stupid".
Once in-process NDT was instituted at a cost of less than $25 per unit, there were no more rejects during the final inspection.
Best regards - Al
......and the reason is because a final NDT is what is most important when the object is completed. Construction codes provide minimum design and fabrication requirements for safe service. How you choose to add process and NDT steps in between is up to you.
- Thread starter
- #8
FYI, i did look @ B31.3 344.7 and it says "when specified in the engineering design".
may original question remains.
gtaw, your post is why i asked this question. i cannot seem to get it thru to some that a little in-process NDE is cheap compared to rejects or failures or safety
may original question remains.
gtaw, your post is why i asked this question. i cannot seem to get it thru to some that a little in-process NDE is cheap compared to rejects or failures or safety
eyec,
gtaw gave you the reasons for "informational" NDE; primarily cost savings. You should be able to convince your management to add NDE by evaluating current repair costs/scrapped parts with the cost of NDE to mitigate it. We often perform low cost informational NDE to mitigate repair.
I once asked a vessel supplier to PT a small portion, twice daily, of the production weld overlay to verify that the welding process was producing a quality product. PT of the completed overlay was required. The supplier refused my request, stating that the requirement was not in the P.O. He was correct of course but his repair costs were in excess of $500,000, not including LDs.
gtaw gave you the reasons for "informational" NDE; primarily cost savings. You should be able to convince your management to add NDE by evaluating current repair costs/scrapped parts with the cost of NDE to mitigate it. We often perform low cost informational NDE to mitigate repair.
I once asked a vessel supplier to PT a small portion, twice daily, of the production weld overlay to verify that the welding process was producing a quality product. PT of the completed overlay was required. The supplier refused my request, stating that the requirement was not in the P.O. He was correct of course but his repair costs were in excess of $500,000, not including LDs.
If you have ASME Sec VIII, Div 2 you'll find some requirements for in process inspections such as VT of back gouges, MT of openings, PT, MT, UT of materials prior to their use. Not all are required 'across the board'. One has to look carefully at the requirements for specific material types, thicknesses, etc.
I'm not sure if you're just asking for interest sake, but, it's important to bear in mind that requirements found in various codes are minimum requirements and not necessarily enough to keep you out of trouble.
I'm not sure if you're just asking for interest sake, but, it's important to bear in mind that requirements found in various codes are minimum requirements and not necessarily enough to keep you out of trouble.
- Thread starter
- #11
stanweld - agree & have heard the PO reasons for not doing NDE, even informational
weldtek - agree on the Minimum requirements. seems butt welds are covered more than any other type of welds for NDE & i do not seem to have the same uphill battle with Sec VIII fabricators/buyers
weldtek - agree on the Minimum requirements. seems butt welds are covered more than any other type of welds for NDE & i do not seem to have the same uphill battle with Sec VIII fabricators/buyers
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