The material being pumped using a pump with a stainless steel jacketed tube gets flattened; please help analyze this issue
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Due to low-temperature crystallization of the company’s materials, a double-walled tube is used for transportation; the inner tube is made of stainless steel with a diameter of DN50, while the outer tube is made of carbon steel with a diameter of DN80. The inside of the tubes contains ether-like substances and ethanol at around 80°C. Steam at 0.3 MPa and at around 130°C is used in the jacket surrounding these tubes. The materials are transported using magnetic pumps, with a flow rate of 25 cubic meters per unit time and a head of 20 meters. The inner tube gets compressed, as shown in the pictures. The company has always used this method for low-temperature crystallization processes, and such an issue has never occurred before. The newly installed pipes have been in use for just two days, and this problem has already appeared. I would appreciate it if experts could help analyze the reason for this. I think there’s a problem with the stainless steel material, but with a wall thickness of 3.5 mm, it shouldn’t be that weak under pressure
Is the sequence of operating the hot and cold media incorrect?
By testing the hardness, one can determine whether there is a problem with the 304 material~~~~ I suspect that there are blockages and areas of restriction inside the tube, and pumping will create negative pressure~~~~
The negative pressure wasn’t well controlled, and it’s hard to say anything about the material – we need to wait for the test results
There should be no negative pressure in the pipe at the outlet section of the magnetic pump. Even with negative pressure inside and positive pressure outside, such a small-diameter pipe should be able to withstand it, right?
The valves at both ends of the pipeline are closed, and a negative pressure is created once the medium cools down.
The material has a low boiling point; when the medium inside the inner tube cools down, a negative pressure is created. When restarting the system, the hot medium is introduced first and then the cold medium (the order of operation is incorrect), which results in an increase in the pressure difference between the inside and outside. Plus, there may be issues with the material. I have seen steam-heated storage tanks get flattened as a result of clogged relief valves during the cooling process. The poster’s situation can be used as a reference
This situation requires improvements in the design, with the addition of pressure control devices. Logically, the steam valve can only open once a certain positive pressure is established in the inner tube.