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Plate heat exchanger: the main factor of its failure

Views:1     Author:Site Editor     Publish Time: 2020-11-11      Origin:Site

As a kind of heat exchange equipment, plate heat exchangers are widely used in many fields in our country and have exerted huge economic benefits. However, the various failures and damages of the plate heat exchanger also cause certain economic losses to the user. The reasons are many. It is related to the short application history of the plate heat exchanger in my country and lack of experience in design, use, maintenance and maintenance .

1  Seal failure

1.1 pressure

When the detachable plate heat exchanger is used within the rated working pressure, the leakage is mainly related to the abnormal impact load in the system (water hammer, air hammer), in addition to the quality factors of the equipment in manufacturing and assembly. It is a phenomenon not easily observed by ordinary operators. The instantaneous pressure peak caused by the impact is often 1-3 times higher than the normal working pressure, which causes the rubber gasket installed in the plate heat exchanger to shift and cause the seal to fail. Because the heat transfer element of this kind of equipment is made of stainless steel sheet (thickness 0.5-0.8), its sealing rigidity is relatively poor and the sealing periphery is very long, so the impact pressure resistance ability is much lower than that of the shell-and-tube heat exchanger. Preventive measures: ①In view of the structural characteristics of the plate heat exchanger, depending on the operating pressure, increase the equipment design pressure by 1.5-2 times. ②The impact phenomenon in the system should be avoided as far as possible during use. ③In applications where such accidents have occurred, measures to increase the thickness of the plates can be taken as appropriate, and the effect is obvious.

1.2 Temperature

Rapid changes in temperature can also cause seal failure. When the temperature changes too quickly, the linear expansion coefficient of the rubber gasket does not match the elastic deformation and the seal pre-tightening force, which will reduce the sealing pre-tightening force and cause the equipment pressure capacity to be lower than the rated design pressure.

This can be solved by the following methods:

① When operating the equipment, the temperature rise should be as slow as possible.

②The compression pre-tightening spring can be designed on the clamping stud to effectively compensate the change of the sealing pre-tightening force and prevent leakage.

2  equipment blockage and scaling

2.1  blockage

The flow channel gap of the plate heat exchanger is small (2.5-6mm), and particles with a diameter greater than 1.5-3mm can easily block the plate passages, which will sharply deteriorate the pressure drop of the equipment and cause the equipment to fail due to blockage. A rough filter or backwashing device can be installed at the media inlet according to needs, which can effectively prevent equipment blockage.

2.2  scaling

Fouling can cause the heat transfer coefficient of the heat transfer equipment to decrease, and even block the plate passages in severe cases. The countermeasures are: ①Plate heat exchangers should not be used in dirty or fouling environments (unless other effective measures are added). ② When unsoftened cooling water is used as the cooling medium, the operating temperature should be controlled at about 50℃ or even lower to avoid the sensitive temperature of calcium and magnesium ions precipitation in the medium. For domestic hot water (bath water), it is necessary to design a special temperature control system to control the temperature of the outlet water (bath water is not allowed to be softened or treated with other chemical methods) before the equipment can be used normally.

The adhesive of chlorine element has proved to be effective in preventing stress corrosion.

3  Conclusion

With the knowledge and understanding of the main factors affecting the failure of the plate heat exchanger, the correct selection, operation and maintenance of equipment can safely and reliably give full play to the high efficiency and energy saving characteristics of the plate heat exchanger, thereby obtaining better economic benefits.

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