A discussion on whether to conduct flaw detection
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A batch of reaction tanks was manufactured at the company; these tanks have jackets, with the liquid flowing inside the inner cylinder. The design pressure is -0.1 Mpa, while the operating pressure is less than -0.1 Mpa. Steam flows inside the outer jacket, with a design pressure of 0.45 Mpa and an operating pressure of less than 0.4 Mpa. The drawings require that the AB seams inside the inner cylinder and the jacket meet the RT 20% III-grade standard. However, since the upper part of the inner cylinder as well as the upper head are located outside the jacket, there is discussion regarding whether RT 20% testing is necessary for the ring seam between the upper head and the inner cylinder. Indeed, the drawings specify that the AB seams inside the container and the jacket must meet the RT 20% standard, but since the upper part of the inner cylinder and the upper head are outside the jacket, could it be considered a device operating at atmospheric pressure, thus eliminating the need for RT testing? Is it because of the schedule issue? Can this circumferential seam be examined without taking X-rays? I hope everyone can offer some suggestions and have a discussion; I really appreciate it!
Since the design requirement is for the inner cylinder to be at 20% RT, it should be carried out in accordance with that requirement. How much work is involved in taking one set of photos? How much cost can be saved?
The design drawings don’t specify whether it’s an inner cylinder; it’s divided into the interior of the container and the interior of the jacket, with 20% radiography required in each case. As a result, there is debate regarding whether the part of the inner cylinder outside the jacket is not under pressure and therefore doesn’t qualify as a pressure vessel, meaning radiography might not be necessary. I’m quite confused, so I’d like to ask everyone whether radiography is indeed required and if there is any basis for this requirement It’s not a cost issue; the factory has few welders whose skills are not up to par. With dozens of pieces of equipment to be processed in a tight deadline, there are many cases where repairs are needed due to issues detected through X-ray inspections after submerged arc welding, and manual welding results in too slow repair times. That’s why they consider skipping the X-ray inspections
The design drawings don’t specify whether it’s an inner cylinder; it’s divided into the interior of the container and the interior of the jacket, with 20% radiography required in each case. As a result, there is debate regarding whether the part of the inner cylinder outside the jacket is not under pressure and therefore doesn’t qualify as a pressure vessel, meaning radiography might not be necessary. I’m quite confused, so I’d like to ask everyone whether radiography is indeed required and if there is any basis for this requirement It’s not a cost issue; the factory has few welders whose skills are not up to par. With dozens of pieces of equipment to be processed in a tight deadline, there are many cases where repairs are needed due to issues detected through X-ray inspections after submerged arc welding, and manual welding results in too slow repair times. That’s why they consider skipping the X-ray inspections
There must also be regulations regarding the inspection rate and methods for welds in atmospheric-pressure vessels.
According to the scope of application specified in GB/T150, with such a high vacuum level in the reaction tank, it is considered a pressure vessel, and flaw detection is essential.
From a classification perspective, the inner cylinder is not subject to pressure vessel regulations, but it meets the requirements of GB150; therefore, it should be designed, manufactured, and inspected in accordance with the requirements of GB150. What does this have to do with whether it is surrounded by a jacket or not?
Don’t go through the trouble; if the inspection officers or the owner disagree at that time, and the equipment has already been manufactured, it will cause a huge problem.
As a technician, don’t create trouble for yourself by leaving safety hazards in the equipment. Submerged arc welding does not require high skills from the operator; the quality of welding is primarily ensured by the welding process and the equipment used. So why would the success rate be low?
If the pass rate for submerged arc welding is so low, that’s an even bigger problem.
Since the drawings require a 20% RT-Grade III inspection, it is necessary to follow those requirements; there is no need to consider whether the welds are enclosed or covered. If such equipment is designed in accordance with GB/T150, 20% RT inspection is required for all Class A/B welds of the inner cylinder and jacket here; if there are welded joints on the head, 100% RT inspection is necessary as well ； In some cases, the welds that are enclosed by a jacket may also undergo 100% RT inspection ；