Heat Exchanger Technology Q&A IV

1. Q: What are the commonly used heat exchanger gaskets?

A: Oil-resistant asbestos, iron-clad, corrugated tooth, and metal.

2. Q: What should we pay attention to in the selection of small floating head bolts for floating head heat exchangers?

A: Length; wet H2S stress corrosion; temperature.

3. Q: What is the function of the baffle in the tube heat exchanger?

A: The baffle plate can change the flow direction of the fluid in the shell side, increase its flow rate of the fluid, increase the degree of turbulence of the medium, improve the heat transfer efficiency and support the tube bundle.

4. Q: Why do tubular heat exchangers have single-pass, two-pass, four-pass, six-pass, and eight-pass?

A: When the total number of tubes of the HE is the same, increasing the number of passes can make the flow velocity in each tube larger, so it can increase the heat supply coefficient and reduce the required heat transfer area. But at the same time, the pressure drop is also increased, and the fluid cannot be heat exchanged in a countercurrent manner, and the structure of the heat exchanger is more complicated. Therefore, the number of tube passes generally used is not less than 2 and not more than 8, which should be selected according to the actual process requirements.

5. Q: What are the reasons for the internal leakage of the tubular heat exchanger?

A: The tube is corroded, perforated, or broken;

Leakage due to corrosion and thinning of the nozzle;

The expansion joint between the heat exchange tube and the Tube Sheet is loose;

Cracks, pores or corrosion perforations at the welding place between thetube and the tube sheet;

Small floating head bolts are loose or broken;

Damaged small floating head gasket;

Damaged small floating head or floating tube sheet seal.

6. Q: Why should the water pressure be tested after the heat exchanger is overhauled?

A: The purpose is to check whether the heat exchanger has the ability to safely withstand the design pressure, tightness, the quality of the interface or joint, the welding quality and the tightness of the sealing structure degree. In addition, it is also possible to observe the residual deformation of the base metal weld of the container and the pipeline after pressure, and find out the problems of the material in time.

7. Q: Why are some tubular heat exchangers installed vertically and some horizontally?

A: Production process requirements: If some reboilers require a certain medium liquid level, the horizontal heat exchanger cannot meet the requirements of the liquid level, so a vertical heat exchanger must be selected;

Large-scale: If the heat exchange area of a process unit requires thousands of square meters, the horizontal heat exchanger with a heat pipe length of 6 meters require several ones, which covers a large area and is not conducive to the effective arrangement of the device space. If you choose a vertical heat exchanger with a heat exchange tube length of 12 meters, one set is enough.

Reduce the pressure drop: Some production processes require to minimize the pressure drop during the medium conveying process. Select a vertical heat exchanger and arrange it in parallel with the tower to shorten the connecting pipeline with the tower and reduce the pressure drop.

8.Q: Why do some choose casing tube heat exchangers or water immersion heat exchangers, while others choose tube heat exchangers?

A: At present, most of the heat exchange equipment selected for oil refining and chemical production plants are shell and tube heat exchangers, but in some production plants, there are still a small number of casing tube heat exchangers and water immersion heat exchangers.

Although the tubular heat exchanger has a compact structure and high heat exchange efficiency, due to the small heat exchange tube, if it is used in a medium containing solid particles, it is easy to cause blockage. Therefore, where the medium containing solid particles is generally used, a casing heat exchanger or a water immersion heat exchanger is generally used.