I would like to ask: How is the pass rate for ultrasonic testing of welds calculated?
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Radiographic testing is determined based on the total number of non-conforming specimens relative to the total number of specimens tested. I would like to ask: How is the pass rate for ultrasonic testing of welds calculated?
One approach is to divide the defect length by the total length of the weld; this results in a much higher pass rate compared to the pass rate calculated based on the number of inspection films used for testing
If the films taken are genuine and valid, then everything is fine based on those films. However, due to various factors at the site, the welding quality of pressure pipelines varies, and random inspections are also selective in nature.
I’ve heard that some design institutes have carried out 100% flaw detection on all pipes, ensuring no blind spots and no missed inspections
If the design is set in this way, it poses a huge challenge to the construction party. The cost expenses for users will increase exponentially. In many cases, the client will ask the designer to meet **the minimum requirements; if that’s not possible, they might choose another designer. It will be a huge test for all parties involved.
Now it’s the other way around; the construction party prefers to do it this way. It is also to avoid missed detections. At the same time, full inspection also incurs mailing costs; this amount is a small sum when it comes to the security of the entire system
That’s how you make money, right! It’s fine to do this for the first time, but the costs for regular inspections will be higher, and may even exceed what is expected. One requires shutdown for testing, which takes a considerable amount of time and incurs high costs. Second, this is how it should be done from now on. Third, the pass rate will drop rapidly, to the point where it becomes impossible to meet the requirements and replacement is necessary.
Number of defective units/Total number of welds inspected; Defective length/Total inspected length; Sampling length * Sampling level * Total number
This actually has little to do with making money. The original intention was to save money, as inspection costs are high; for those pipelines and equipment that are considered less important, only partial inspections are carried out, thereby reducing the inspection costs. Of course, this also has some drawbacks. Nowadays, quality is of paramount importance – the losses caused by even the slightest leakage exceed the amount saved on inspection costs
In that case, the pass rate for ultrasonic testing is much higher than that for RT
This is not necessarily the case; taking 100% testing as an example, there is also a passing standard associated with it. Those who understand it calculate it based on the number of defective units/total number of welds inspected; those who don’t understand it opt for the second method to make the numbers look better, while the third method is used to deceive laypeople by presenting things as meeting standard specifications