corrosion failure types of plate coolers
are mainly corrosion, crevice corrosion, stress corrosion cracking, intergranular corrosion, uniform corrosion, etc. Of these several types of corrosion failure, the first three are common, and the three types of dangerous corrosion failure are also dangerous. .
The pitting of the cooler means that the metal surface such as stainless steel plate is rusted or scaled, which results in poor thermal conductivity and reduced pH value of the medium, which results in the destruction of the passivation film on the local metal surface, causing local corrosion. It is also called occluded battery corrosion, and generally appears as a perforation or pit of less than 1mm.
crevice corrosion is a spot-like or ulcerated local corrosion caused by occluded battery corrosion, but this corrosion mainly occurs in the gaps of metal parts, so it is called crevice corrosion. This kind of corrosion is mainly It is caused by the electrochemical heterogeneity of the retention medium.
The stress corrosion cracking of the oil cooler refers to the residual internal stress of the cooler plate and other products during the manufacturing process. Under the combined action of static tensile stress and electrochemical media such as halogen ions, the metal is caused by the dissolution of the cathode. Corrosion cracks or fractures.
The intergranular corrosion of the oil cooler originates from the metal surface and penetrates into the interior along the grain boundaries. For example, stainless steel will corrode if it is in the temperature range of 400 ℃ -600 ℃, and this corrosion will cause the bonding force between the grains. Loss makes the strength of the material greatly reduced.
Uniform corrosion of the cooler: The improper material selection of the cooler plate or the long use time exceeds its service life, and most or all of the metal surfaces that can contact the medium will be corroded. This is uniform corrosion. In order to avoid this, Corrosion, the material of the cooler should be selected properly, and the service life should be replaced in time.
In addition to the above-mentioned cooler http://www.tzge.net corrosion failure types, there are other types of corrosion failure such as leak point corrosion, abrasion, and microbial corrosion. The dew point corrosion of the oil cooler is mainly caused by the contact between the hot steam containing acidic materials and the cold plate; the abrasion occurs due to the high flow velocity at the corner of the medium inlet of the plate and the diversion area, or the fluid contains sand particles Caused by particulate matter; microbial corrosion is mainly caused by algae, bacteria, and protozoa in seawater.
Plate heat exchanger Plate heat exchanger has high heat transfer coefficient, small pressure drop, compact structure, light weight, small footprint, convenient area and process combination, strong generality of parts, wide choice of materials, and easy scale production. Characteristics, has been widely used in food, machinery, metallurgy, petrochemicals and ships and other fields, and has become the main heat exchange equipment in urban central heating projects.
External leakage is one of the common failures of plate heat exchangers, which mainly manifests as leakage (small amount, discontinuous water droplets in plate heat exchanger) and leakage (large amount, continuous water droplets). The main parts of the leakage are the sealing place between the plate and the plate, the second sealing leakage groove of the plate, and the inside of the end plate and the pressing plate.
The main reasons for the leakage of plate heat exchangers and the treatment methods are:
1. The clamping size is not in place, the size of the plate heat exchanger is uneven (the size deviation should not be greater than 3mm), or the clamping bolts are loose.
Solution: In the no-pressure state, re-clamp the device according to the clamping dimensions provided by the manufacturer. The dimensions should be uniform and the deviation of the clamping dimensions should not be greater than ± 0.2N (mm) (N. is the total number of plates). The parallelism between the two clamping plates should be kept within 2mm.
2. Part of the gasket is detached from the sealing groove, the main sealing surface of the gasket is dirty, the gasket is damaged or the gasket is aging. Plate heat exchanger
Solution: Make a mark on the leakage area, then disassemble the heat exchanger to check and solve them one by one, reassemble or replace the gaskets and plates.
3. The plate is deformed, and the assembly of the plate heat exchanger is misaligned, causing the running pad.
Solution: disassemble the open heat exchanger, repair the deformed part of the plate or replace the plate. In the case of plate heat exchangers, when the plate spare parts are not available, the deformed parts can be temporarily removed and reassembled for use.
4. There is a crack in the plate sealing groove or in the second sealing area.
Solution: When reassembling the disassembled plate, clean the surface to prevent dirt from adhering to the sealing surface of the gasket.