Q: In the routine maintenance of welded plate heat exchangers, why is it repeatedly emphasized to lock out/tag out and cool to ambient temperature?
A: During operation of a welded plate heat exchanger, high-temperature media or pressurized fluids may remain in the plates and flow channels. If the power is not completely cut off and lockout/tagout is not performed, accidental startup or release of residual energy may cause burns, splashing, or even equipment damage. At the same time, if the plate material has not cooled to ambient temperature, it is prone to deformation due to thermal stress during disassembly, affecting subsequent sealing performance. Therefore, before maintenance, it must be confirmed that the power supply has been disconnected and the operation tag has been hung, and work should only begin after the equipment has naturally cooled to ambient temperature.
Q: Besides safe operation, what medium-related parameters should also be noted during maintenance?
A: Maintenance records should be consistent with the selection parameters. During the selection stage, the medium name, concentration, and temperature range must be provided; these data determine the plate material and flow channel compatibility. For example, media containing chloride ions pose a corrosion risk to stainless steel plates, and the higher the concentration and temperature, the more obvious the corrosion tendency. If changes in medium parameters are found during maintenance, it should be promptly reviewed whether the plate material selection is still suitable, so as to avoid leakage or blockage caused by operating condition deviations. Recording medium parameters also helps determine the scaling rate and cleaning cycle.
Q: When disassembling and reassembling plates, what details are easily overlooked?
A: Before disassembly, the plate sequence and orientation should be marked to avoid misalignment during reassembly. The plate pack of a welded plate heat exchanger usually forms flow channels in a specific arrangement; arbitrarily changing positions will disrupt the designed flow channels and affect heat exchange efficiency. During reassembly, the gaskets should be checked for aging, cracking, or displacement, and the fastening bolts should be tightened evenly in stages in a diagonal sequence to avoid local overpressure causing plate deformation. If hard particles or scale are found on the plate surface, soft tools and suitable cleaning agents should be used; metal brushes should not be used for strong scraping.
Q: After maintenance is completed, how should the necessary operational confirmation be carried out?
A: First conduct an appearance and fastening status check to confirm that no tools or parts are left behind. Then restore power according to the operating procedure, slowly increase pressure and temperature, and observe for leakage, abnormal vibration, or abnormal pressure difference. During the initial operation stage, inspection frequency should be increased, and inlet and outlet temperature and pressure data should be recorded and compared with those before maintenance to determine whether heat exchange performance has recovered. If there is a continuous increase in pressure difference or the temperature does not meet the standard, the equipment should be shut down to recheck whether the flow channels are blocked or the plates are installed in reverse.
Q: In daily operation and maintenance, which habits help extend the service life of a welded plate heat exchanger?
A: Keep medium parameters stable and avoid operation above temperature and pressure limits; regularly check the condition of gaskets and bolt preload; formulate a cleaning plan according to the scaling tendency of the medium; and fully record the operation contents and replaced parts after each maintenance. These practices do not depend on a specific project or organization and belong to general technical management, helping to maintain stable operation of the equipment under design conditions.
