The equipment failure of the
Plate Heat Exchanger in practical application will affect the operating efficiency of the enterprise in the slightest, cause economic losses in severe cases, and even cause personnel safety accidents. Therefore, it is very important to analyze and summarize the causes, prevention and solutions of the common faults of the equipment. The common faults of plate heat exchangers include three aspects: insufficient heat supply, external leakage, and liquid stringing.
1. Insufficient heating caused by channel blockage or plate scaling
Affected by the channel structure and clamping size of the detachable plate heat exchanger, when the size of the foreign matter exceeds a certain size, it is easy to stay in the channel during the process of flowing through the plate channel, forming an accumulated blockage over time, which increases the pressure drop of the equipment , reduce heat transfer efficiency, impact and wear plates, etc., which will eventually cause the equipment to fail to work normally. In the same way, due to the different components of the fluid, when the plate is fouled to a certain extent, the above failure can also be caused.
Solution: According to different process conditions and faults, backwashing, dismantling and cleaning, installation of filters, replacement of plates and gasket materials, and addition of scale inhibitors can be used to solve and prevent faults.
Second, the leakage caused by the failure of the sealing structure
Usually due to excessive temperature or pressure drop changes in process conditions, abnormal use, etc., the damage of the sealing gasket, the deformation of the plate, and the aging of the sealing gasket after long-term use are the main reasons for the failure of the sealing structure. Its manifestations mainly include internal leakage or external leakage between two media.
Solution: According to the different causes of the failure, it is necessary to reasonably adjust the control process of the process valve, repair the damaged parts of the process control, fasten the heat exchanger or disassemble the heat exchanger, and replace the damaged gasket or plate. In the case of insufficient spare parts, the damaged group (odd, even) plates and gaskets can be taken out at the same time to prevent internal leakage after assembly.
3. Liquid leakage caused by corrosion
The corrosion failure of the
Removable plate heat exchanger mainly comes from the corrosion of the plates. The light ones cause damage to the surface of the plate, and the severe ones cause internal leakage and stringing between the two fluids, which is one of the serious faults that affect product quality and normal use of equipment. Common corrosions include: Pore corrosion (porous or point-like corrosion), crevice corrosion (corrosion formed in crevices), stress corrosion (corrosion caused by stress and corrosive medium), intergranular corrosion (metal corrosion) Corrosion damage to material grain boundaries), etc.
Solution: Eliminate or reduce the residual stress of the plate in the design, processing, storage, assembly and other links; and reasonably select the plate material and corrugated shape according to the process conditions; or passivate the surface of the stainless steel plate; improve the durability Corrosion performance; add corrosion inhibitors and other methods to prevent and solve.
4. Dismantling and maintenance methods of plate heat exchangers and related precautions
When the flow channel is blocked, the plate is severely scaled, the heat transfer efficiency does not meet the process, and the sealing structure fails, etc., it is often necessary to disassemble and repair the detachable plate heat exchanger.
Before disassembly, relevant energy sources must be effectively isolated and released (such as disconnecting the power supply of the pump, closing the inlet and outlet valves of various fluids, opening the exhaust valve to empty the fluid, reasonably controlling the temperature of the body, etc.), and wearing relevant personal protective equipment. , to start working. In the process of disassembly, cleaning, replacement of parts, and assembly, there are many links that are likely to cause damage to parts or affect later use.
4.1. Disassemble and clean
Disassembly cleaning is the most common and thorough cleaning method for removable plate heat exchangers. It usually consists of physical cleaning method and chemical cleaning method. That is, the surface of the plate and sealing gasket is cleaned by means of pressure washing, wiping (brush) washing, and chemical immersion. During the cleaning process, try not to use sharp tools such as wire brushes and blades. The chemical immersion solution should be selected in combination with the material of the plate to prevent unnecessary damage to the cleaning parts.
4.2. Check the plates and gaskets
During the inspection of plates and gaskets, defective parts affected by deformation, corrosion, cracking, perforation, wear, aging, etc. can be replaced or repaired. Inspection and repair of plates are usually carried out by light transmission method and welding repair method. In the case of insufficient spare parts, according to the needs of the process conditions, a small number of groups of damaged plates can be taken off-line (the specific off-line quantity needs to be calculated according to the usage situation, or refer to the manual or consult the manufacturer).
4.3. Heat exchanger assembly
Before the plates are assembled, the movable compression plate should be pushed to the end of the other side of the fixed compression plate, and the fixed compression plate, movable compression plate, each nozzle and sealing surface should be cleaned, and the plates and After the sealing gasket is installed, push back the movable compression plate, hang the clamping screw, and gradually tighten it to the rated clamping size range (if the number of reinstalled plates and sealing gaskets remains the same, it needs to be replaced according to the The quantity, combined with the old and new and the degree of damage and aging, should be used to fasten the clamping size reasonably. Usually it is slightly smaller than the original clamping size on the manual or the data recorded before disassembly. In addition, when encountering shortage of spare parts, transformation, etc., it is necessary to When increasing or decreasing the number of plates and gaskets, the new clamping size = the original clamping size ÷ the number of original plates × the current number of plates). During the fastening process, it is necessary to use a tape measure or a steel ruler to measure the clamping size of each part, try to keep the movable compression plate, plate and gasket moving in parallel, and pay attention to the movement of the plate and gasket surface to prevent deformation of the plate, Faults affecting the use such as gasket out of groove occur. The selection of compression assembly tools should be based on the premise of safety, based on the principles of convenience, efficiency, and labor saving, and reasonable selection of tools such as ring wrenches, ratchet wrenches, and hydraulic tooling for related work.
4.4. Pressure test
After the detachable plate heat exchanger is assembled, a pressure test is required. During the test, the system pressure and temperature are slowly raised to the design value, and the pressure is maintained for at least 30 minutes according to the site conditions. During the period, observe whether there is leakage or abnormal sound. It is qualified if the pressure does not drop, and there is no obvious assembly defect in the gap between the plate and the gasket.
February 23, 2023
