“Is it a problem that welded steel pipes are not allowed to be used in pressure vessels?
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This post was last edited by MXYXY on 2011-5-14 at 14:50. Why are the statements “Welded steel pipes shall not be used in pressure vessels” and “Alkaline electrodes must be used for shielded metal arc welding on Class II pressure vessels” incorrect? Can you give an example? Basis?
Welded steel pipes can be used in pressure vessels, such as the butt welds of heat exchange tubes in heat exchangers, as well as the vessel shells made from butt-welded seamless steel pipes. In pressure vessel manufacturing, alkaline electrodes are required for Class A and Class B welds, as this helps to reduce the likelihood of welding defects. The difference between alkaline and acidic welding electrodes is that alkaline electrodes have a lower hydrogen content; in addition, they possess higher yield strength and tensile strength.
The first two are multiple-choice questions. Ask why the answer is wrong. The answer on the 2nd floor is not very accurate. Hope to continue participating in the discussion.
Welded pipes can be used in pressure vessels, but the pressure they can withstand is limited. Welded steel pipes of high quality possess better mechanical properties and corrosion resistance than seamless steel pipes. Some highly corrosive low-pressure pressure vessels prefer to use welded pipes
Reply 1# MXYXY: This thing is not absolute. By common sense, welded steel pipes refer to those welded carbon steel pipes made of Q235B material. Such pipes should of course be avoided for use in pressure vessels.
Alkaline welding electrodes are not necessarily required either. That flux-cored wire can be used too. Gas shielded welding can also be used. Mainly, it is because alkaline electrodes have a low hydrogen content.
The prescribed usage depends on the customer’s requirements; rules are fixed, but people are flexible.
It should be avoided as much as possible. Compared to seamless steel pipes, welded steel pipes are prone to stress concentration and corrosion at the welds, whereas such problems occur less frequently in seamless steel pipes.
None of them are mandatory requirements; they are merely industry conventions, or rather, a matter of caution.
The performance of welded pipes is inferior to that of seamless pipes, and low-hydrogen basic electrodes reduce hydrogen-induced cracks compared to acidic electrodes; therefore, an optimized approach must always be chosen in the manufacture of pressure vessels.
Welded steel pipes can be used as pressure vessel shells. However, it must be inspected or tested in accordance with the relevant requirements of GB150. If it meets the relevant standards, it can be used boldly.