Let’s discuss this issue
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The shell side of the heat exchanger operates at 1.67 MPA, with a flammable fluid as the medium (the specific type was forgotten); the tube side operates at 0.67 MPA with water as the medium. The drawings specify that the tube sheet and shell should be made of PT or MT material, with 20% A/B radiographic inspection required. Question: 1. Since it is a product under inspection, when carrying out the manufacturing process, we added PT inspections for the welds between the heat exchange tubes and the tube sheet, as well as for the welds in the tube box (between the short sections and the type A flanges), is that correct? 2. Are gap tests generally performed on the welds between short sections and type A flanges? If so, what type of gap test should be carried out? 3. In terms of the preceding conditions, are the requirements regarding gap testing specified fully in the drawings?
PT inspections have been added for the welds between the heat exchange tubes and the tube sheet, as well as those in the tube box (welds between the short sections and the type A flanges)…. In my opinion, the first part is reasonable, but the second part is unnecessary. Water flows through the tube side, so there’s no need for inspections on those welds; since flammable materials flow through the shell side, it’s necessary to inspect the surface of the tube ends, and if possible, conduct ammonia leak testing (or other more advanced testing methods such as helium leak detection) on those tube ends…
It is reiterated that, as it is a product under inspection, the designers may not be very familiar with it; please refer to the three points mentioned in the original post – the person above only covered one of them.
Based on the conditions, this is a Class II heat exchange vessel, and 20% inspection is reasonable. As for the weld between the tube sheet and the shell, in my understanding it is a Class C weld; it doesn’t matter whether flaw detection is carried out or not. Of course, it would be better if the drawings specified surface inspection requirements. So: 1. Whether surface inspection is required for the welds between the heat exchange tubes and the tube sheet still depends on the requirements specified in the drawings. You say the design party is not familiar with these requirements – but are you, the manufacturer, more familiar? If the manufacturer adds surface inspection, I guess no one will disagree: lol ； 2. Surface inspection should originally be carried out on the welds between the flanges and the splices, as specified in clause 6.6.1.3 of the container flange standards ； 3. Are the requirements for flaw detection not fully specified in the drawings? I assume you are referring to the welds between the heat exchange tubes and the tube sheet, as well as those between the flanges and the stubs; the designer should specify these in the drawings. There is no error if such specifications are not provided for the former. Also, don’t make a big deal out of it just because it’s a monitoring container; as long as you follow the specifications, there will be no problems.
It is certainly possible to add surface inspection for the pipe end welds as part of the manufacturing process, but it is not mandatory; however, surface inspection must be carried out on the welds between the tube box and the type A flanges. The drawings generally specify the inspection of weld joints of types A and B in the shell; inspections for weld joints of types C and D are indicated on the drawings only when the designer deems it necessary, such as the Type D welds between large-diameter nozzles and the shell, as well as the Type C and D welds that are required to be inspected per standards. Welds between the tube box and type A flanges, as well as those between the tube sheet and the shell, are generally not specified in the drawings; those responsible for the manufacturing process need to take these issues into account. So I think there’s nothing wrong with the non-destructive testing requirements specified in the drawings; of course, this is just my personal opinion. Usually, I’m also the one who designs the drawings for the manufacturing processes of the products I work on, so I’m well aware of them.
I am quite satisfied with what everyone has said. But I think the markings on the diagram should be more comprehensive.
If the shell side contains flammable media, ammonia leak detection at the pipe connections should be added; other inspections are also necessary.
It is not necessary to list all requirements on the drawings; as long as standards are referenced, the work should be carried out in accordance with those standards.
The inspection standards for pipe ends do not specify this in detail; unless it is a heat exchange tube made of special material, inspection requirements will be specified in the drawings. If it isn’t mentioned in the drawings and the manufacturer is concerned, an additional inspection can also be carried out ； The welding of the equipment flange to the cylinder should be carried out in accordance with the provisions of JB/T4700-2000; the standards specify this clearly. As long as the flanges on the drawings are of types JB/T4701~JB/T4703, they must comply with the provisions of JB/T4700-2000. It is not necessary to specify everything in the drawings.
For designers, ensuring the safety of the product is the first priority; however, it isn’t necessary to specify all types of inspections. As an important part in the production process, the manufacturing unit is responsible for guaranteeing the overall safety and reliability of the equipment. For example, the design may specify 20% RT testing, but the manufacturing unit is responsible for ensuring the welding quality of the remaining portion. If the manufacturing unit is unable to guarantee the welding quality, this percentage can be increased to 100% RT. I believe the design agency won’t object; it’s just an example.