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Home > News > Industry News > Routine maintenance of refrige.....


Routine maintenance of refrigerated unit of refrigerator truck

  • Author:Changjie
  • Release on :2016-08-23

1. Dehumidification and drying of refrigerator truck unit: After pressure leak detection qualified, the next step is drying and dehumidification for unit. There are two dehumidification drying methods: one for the vacuum drying method, the other is in the dry gas displacement method. Vacuum
drying method is efficient vacuum pump, pressure inside the unit is evacuated to 666.6 ~ 1333.2Pa (5 ~ 10mmHg) absolute pressure, the boiling point of water at this time dropped below 10 ℃, far below the boiling point of water so that the local temperature, resulting in the unit full vaporization of water remaining, and a vacuum pump. Specific method of drying gas displacement law: the use of a vacuum pump inside the unit into a vacuum state, the people filled with dry nitrogen, the inner unit contributed the remaining moisture vaporization, by observing the U-shaped mercury manometer mercury column height
increases status, repeatedly evacuated 2 to 3 times with nitrogen, in order to achieve the purpose of dehumidification.
2. Pressure leak test: pressure leak refers to a dry nitrogen gas man centrifugal refrigeration compressor systems, by the process of applying pressure to check for leaks. The specific methods of operation are:
 ① filled with nitrogen before closing all valves to the atmosphere.
 ② Open all connecting pipe, pressure gauge, exhaust valve recovery.
 ③ into the system filled with nitrogen. 
People filling nitrogen process can be divided into two steps. When the first step filled with nitrogen to a pressure of 0.05 ~ 0.1MPa stop, check whether the unit large leak. Confirming that no large leak, then pressurized. The second step is for the use of R134a refrigerant unit may be pressurized to about 1.2MPa. If the unit is equipped with a rupture disc device, the nitrogen pressure should be less than the disk operating pressure. After purged with nitrogen work, soapy water applied each unit the joint, flange, filler cap, welding, check for leaks, if any doubt should be well marked leak, when used for maintenance. Check for the evaporator and condenser tube plate flange, the water chamber cover should be removed for inspection. During the inspection, if found to have micro-leakage phenomenon; to determine whether the leak can be made to the system charged with a small amount of freon refrigerant freon refrigerant and nitrogen so thoroughly mixed, then an electronic leak detector or leak halogen lamp confirmatory leak detection. After confirming the sensing unit for leaks after the leak test should be carried out packing work, the requirements are: dwell in the leak testing of 24h. Pressure drop
before 6h unit should not exceed 1%, and the remaining 18h should keep the pressure stable.
3. Vacuum leak detection test for refrigerator truck: According to "centrifugal chillers technical conditions" (JB / T3355-91) standard provisions, the vacuum unit should be maintained at 1333Pa (10mmHg) level. Vacuum leak test method of operation are: the internal unit evacuated to an absolute pressure of 2666Pa state, the vacuum pump stops working, turn off the
vacuum pump unit communicating bellows valves, wait l ~ 2h after, if the pressure rise within the unit, you can start again 2666Pa vacuum evacuated to an absolute pressure or less, in order to remove residual moisture inside the unit or a refrigerant vapor. If after so
repeatedly, still increased pressure within the unit, the unit may suspect there is a leak somewhere, should redo pressure leak test. Last run timed from the vacuum pump is stopped, if the unit within 24h after pressure is no longer rising, the unit can be considered
substantially leak-free, can be maintained for 24h. If more holding 24h, the difference between the total decline in the degree of vacuum within the unit does not exceed 1333Pa, the degree of vacuum units can be considered qualified. If the decline in the degree of vacuum inside the unit exceeds 1333Pa, we need to continue to do a pressure test
until the compliance date.