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The reason for heat exchanger plate leakage
Jan 28, 2019

(1)The clamping size is not in place, the dimensions are not uniform everywhere (the size deviation should not be greater than 3 mm everywhere) or the clamping bolt is loosened. Part of the plate heat exchanger gasket is separated from the sealing groove, the main sealing surface of the gasket is dirty, the gasket is damaged or the gasket of plate heat exchanger is aging. (3) The plate deforms and the misalignment of the assembly causes the running mat. (4) There are cracks in the plate sealing groove or the second sealing area. Examples: Many thermal stations in Beijing, Qinghai and Xinjiang all use saturated steam as primary side heat source for heating. Because of the high temperature of steam, rubber gaskets fail at high temperature and cause steam leakage when the system is unstable at the initial stage of equipment operation.


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(1)In the non-pressure state, the clamping equipment should be re-clamped according to the clamping size provided by the manufacturer. The size should be uniform and the deviation of the clamping size should not be more than (+0.2N(mm)(N). For the total number of plates, the parallelism between the two compacted plates should be kept within 2 mm. (2) Make a mark on the leakage site, and then the heat exchanger disintegrates one by one to solve, reassemble or replace the gaskets and plates. (3) Dismantling the heat exchanger and repairing or replacing the deformed part of the plate. When there is no spare parts, the deformed plate can be temporarily removed and reassembled for use. (4) When reassembling and disassembling the plate, the plate surface should be cleaned to prevent dirt from adhering to the gasket sealing surface.


(1)Cracks or perforations occur in heat exchanger plate corrosion due to improper selection of plates. (2) Operating conditions do not meet the design requirements. (3) Stress corrosion is caused by residual stress after sheet cold stamping and too small clamping size in assembly. (4) There is slight leakage at the plate leakage trough, which causes harmful substances (such as C1) in the medium to concentrate and corrode the plate, forming a series of liquids. Example: A BR03 plate heat exchanger with 254 SMo plate material in a sulphuric acid system of an aluminium industry limited company, after five months of operation, the corrosion leakage of carbon steel nozzle on the cooling water side occurred, and the acid leaked to the cooling water side.

 

Severe corrosion and cracking were found at the inlet and diversion area of plate acid solution. Field analysis shows that the operating temperature, flow rate and concentration of the system are beyond the design conditions, and the use temperature is far beyond the applicable range of materials. Plate heat exchangers with saturated steam as primary heat source are prone to plate corrosion during operation, which results in liquid crossing of products. This is because of the high steam temperature, the rubber gasket is easy to fail at high temperature during the operation of the equipment, causing steam leakage and rapid condensation in the secondary sealing area. With the continuous leakage, more and more condensate residues accumulate, and a high concentration area of CL is formed locally, which can destroy the corrosion condition of passive layer on the surface of plate. At the same time, due to the large internal stress formed by cold stamping in this area, stress corrosion occurs under the condition of the surface passivation layer being destroyed.

 


(1)Replace the plate with cracks or perforations, and find the cracks in the plate by light transmission method in the field. (2) Adjust the operating parameters to meet the design conditions. (3) The clamping size of heat exchanger during maintenance and assembly should meet the requirements, not the smaller the better. (4) Matching plate materials of plate heat exchanger reasonably.


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