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Heat exchanger causes stress corrosion cracking

Views:2     Author:Site Editor     Publish Time: 2021-03-24      Origin:Site

How do you deal with common abnormalities of heat exchangers?

Plate heat exchanger is a kind of efficient heat exchange equipment, it has the advantages that other heat exchange equipment can't compare: it has high heat transfer coefficient, less heat loss, small footprint, compact and lightweight structure, convenient maintenance and cleaning, and wide application range However, the plate heat exchanger also has its own shortcomings. For example, the pressure cannot exceed 2.5Mpa, the temperature cannot exceed 250 degrees Celsius, and it cannot exchange heat for larger particles and long fibers. For extremely corrosive Can not be used under working conditions, easy to block, etc. The following will analyze some common abnormal phenomena of heat exchangers:

central-heating-unit

One:Leak

1 Leakage during shutdown is mainly due to frequent start and stop of the heat exchanger, which can restore normal working conditions and availability;

2 The main reason for internal leakage is the damage of the gasket and the corrosion and perforation of the plate;

3 Leakage is mainly due to misalignment, extrusion, damage of the gasket, corrosion and deformation of the plate, and it is not compressed to the specified clamping size;

4 Leakage between the blind plate and the clamping plate The main reason is that the blind plate is pierced by a hard object.

Two: Abnormal pressure drop The pressure drop is greater than the design value. 

1 The actual flow rate is greater than the design value; 

2 The plate is blocked;

3 The plate inlet is blocked.

Three:abnormal heat transfer 

1. The outlet temperature of the hot side is higher than the design value, mainly due to the selection problem, the flow rate of the hot side is larger than the design value, the plate is blocked or the flow rate of the cold side is small, etc.; 

2 The outlet temperature of the cold side is too low, the main reason is The hot side flow is small or the temperature is lower than the design value, the plate is blocked, etc.

Four:Tell everyone that in addition to using special ZS ceramic anticorrosive coatings for heat exchangers and heat exchangers, other methods can be used to extend the service life:

1. Reduce residual stress: According to actual experience, the stress that causes stress corrosion cracking is mainly residual stress, and the residual stress is mainly composed of internal stress caused by cold working and welding. Heat treatment of cold-worked parts and welded parts helps to eliminate residual stress, which also helps prevent stress corrosion.

2. Improve the structure of the heat exchanger: In order to avoid the retention of residual liquid and deposits, double-sided butt welding and continuous welding should be used as much as possible during welding to avoid lap welding and spot welding. The working principle of the heat exchange unit net tells everyone that the welding wire should be 100% filled in the welding process to ensure that the weld is formed well.

3. Cleaning heat exchangers and heat exchangers: the heat exchangers and heat exchangers can be cleaned by circulating cleaning. The cleaning liquid is pumped into the circulating water system through the pump to circulate. This method has the effect of cleaning the plates after scaling better. The cleaning of the heat exchanger generally chooses cleaning agents with strong penetration, peeling, cleaning and corrosion inhibition capabilities. The cleaning treatment before putting it into operation can greatly reduce the corrosion accidents.

4. Reduce the corrosiveness of the medium: The stress corrosion can be controlled by removing the dissolved oxygen and oxidant in the medium, and the mass concentration of Cl- in the medium can be reduced. Strictly controlling the mass concentration of sulfur in the medium is also an effective measure to control stress corrosion.

5. Electrochemical protection method, stress corrosion fracture is the anodic dissolution process under stress. Therefore, it can be controlled by electrochemical protection.


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