Why is the heat exchanger in the synthesis tower a low-pressure device
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A few days ago, during maintenance work, the synthesis tower was disassembled and the heat exchangers inside it were subjected to a hydrostatic pressure test; however, the pressure reached only 1.0 MP. During normal operation, the pressure inside and outside the tubes of the heat exchangers is over 200 kilograms per square centimeter. I would appreciate any advice from those with more experience
"The pressure inside and outside the tubes of the heat exchanger is over 200 kilograms – that’s the answer
Reply to 2# shujiang622: In our company, amounts of over 200 kilograms fall under the category of high-pressure pipelines
Reply to 3# xuyanhui198610: What I mean is that equipment weighing over 200 kilograms is already considered high-pressure equipment. But why is the pressure only raised to 1.0 MP? Aren’t they worried about leaks after it’s reinstalled?
A pressure reduction of ten kilograms is sufficient, as the pressure difference between the internal components and the outer wall should not exceed two kilograms; only in areas with higher pressure will there be leakage to areas with lower pressure. Do you understand?
Inside and outside the tower tubes of the heat exchanger in the tower, there is high-pressure gas; the pressure difference between the inside and outside under normal operation is the operating pressure of the heat exchanger in the tower, that is, the pressure it has to withstand. Only if the resistance inside the tower increases does the pressure it bears rise. In ammonia synthesis and glycol production plants, some facilities experience damage to the spiral plate heat exchangers located at the bottom of the glycol tower; this occurs because these devices are designed for low-pressure conditions, and damage arises as a result of improper operation. . .
The testing pressure inside the heat exchanger tubes of the synthesis tower is primarily determined based on the pressure difference between the inside and outside of the tubes. It is not based on system pressure.
The situation you mentioned is also a common problem in chemical engineering; it’s just called by a different name. It seems there’s no exact standard either. You say it’s a high-pressure device, but its pressure difference is quite small; you say it’s a low-pressure device, yet it still operates in a high-pressure environment. So it also can’t be strongly named. Such as catalyst baskets, cooling coils inside the tower, and so on. It is not as obvious as in the boiler air vessel section or the evaporator liquid ammonia section.
It seems that here we need to understand the concepts of pressure (strictly speaking, stress) and pressure difference
The reason why the heat exchanger inside the tower only needs to withstand the pressure difference between its interior and exterior is that it is necessary to control this pressure difference within the tower
This post was last edited by TH373637 on 2011-9-28 at 19:33. Although it is a high-pressure device with a pressure of 200 kgf, the pressure difference is only 2 kgf; thus it becomes a low-pressure section within a high-pressure device