Seeking help with inspection methods for special equipment!
Thread Content
Dear colleagues, our facility has a 10m3 pressure vessel on which there are 3 pits with a diameter of 3 cm and a depth of 3–5 mm (the designed thickness is 12 mm). It appears that these pits were caused by collisions. Is there any way to assess the condition of these areas? It’s not possible to measure the thickness
Once it is polished flat, thickness can be measured. Then a magnetic particle test can be performed, or an ultrasonic test as well; if possible, an X-ray scan can also be done. You can’t achieve damage-free results without polishing
I remember you already asked this question. This depression cannot be assessed through simple non-destructive testing; the material in the depressed area undergoes cold working hardening, which leads to an increase in strength and hardness as well as a decrease in plasticity and toughness. The properties of this area become completely different from those of the unaffected areas, resulting in degradation. Moreover, from a structural perspective, when subjected to medium pressure, the recessed areas experience high edge stresses; it is simply impossible to calculate the stress levels in these recessed areas without conducting a stress analysis. From the perspective of simplicity, ease of implementation, safety, and conservatism, it is recommended to have the pressure vessel manufacturer carry out on-site patching.
Received. Thank you. This is the first time I’ve asked this question
We tried using magnetic powder, but the effect wasn’t very good; nothing could be seen
The simplest method is to use a thickness gauge; if that isn’t available, then UT can be used. As a last resort, photographs can also be taken, and the differences in wall thickness can be determined based on the darkness of the images. Regarding cold work hardening, it needs to be assessed based on the operating pressure and the medium used. If it is compressed air, no repair is necessary; it can be used as long as it is confirmed that there are no cracks on the surface.
Thickness measurement is done together with surface inspection; the surface must be polished until the metallic luster appears
For a regular air storage tank, it doesn’t matter; after all, the measurements you take yourself don’t have any legal validity