About frost crack of Plate heat exchanger replacement steps and matters needing attention in order to keep the field replacement plate in meet the requirements, ensure the quality of the replacement process, prevent change again after the board in east of the crack problem, need to maintenance personnel in the maintenance board in strict accordance with the following steps to detect when frost crack unit, replacement and installation, at the same time pay attention to check the air conditioning water system and the unit itself protection device detection and maintenance.
1. System parts that need to be replaced for maintenance after freezing and cracking of board replacement
In the plate replacement after freezing crack, generally the whole air conditioning system will have water into, which will generally lead to compressor, drying filter, Plate Heat Exchanger failure, the three components must be replaced;At the same time, a large amount of water may gather in the vapor liquid separator, liquid storage tank, finned condenser and pipeline in the system, which need to be removed and dried during maintenance.
II. Steps for replacement and installation of maintenance parts
1. Clean the water in the air conditioning water system;
2, the failure of the compressor, plate Heat Exchanger, drying filter replacement;
3. Cleaning system pipelines, finned condensers, vapor-liquid separators, liquid storage tanks, throttling devices and other components in R22 system;(A small amount of sediment in the water system may enter the system because of the rupture of the plate heat exchanger, so we must clean the system during maintenance to ensure the cleanliness of the system)
4. Drying system pipeline, finned condenser, vapor-liquid separator, liquid storage tank, throttling device and other components in R22 system;
5, plate heat exchanger welding reducing diameter;
6, the compressor, plate heat exchanger, dry filter welding to the system;
7. Leak detection system;
8. Vacuum;
9. Fill the system with refrigerant according to the nameplate;
10, after the water system injection, check whether the unit components are normal;
11, and then test the operation of the unit.
Three, water system treatment
Before re-filling the air conditioning water system, please clean the system pipeline to ensure that there is no sediment, oil and other impurities in the water system.
IV. Matters needing attention during inspection, maintenance and installation
1. Check whether the Y-type water filter is installed before the water inlet of the unit, whether the filter screen of the Y-type water tachometer is 50 mesh, whether the filter screen is tightly installed and whether there is any damage, and the installation position of the filter is as close as possible to the water inlet of the unit;Y type water filter must be installed;
2. Check whether the water flow switch works normally. In normal conditions, the water flow switch can only be connected after the pump is opened.When the water pump stops, the water flow switch will be disconnected, and the whole unit will stop running.In addition, when adjusting the flow switch, the general action value is: in the standard water flow of 60%-70% below, the flow switch is disconnected, the flow switch is switched on in the standard of 80%-90%.
3. Before the unit is started, please check whether the inlet temperature and antifreeze protection temperature are set correctly. The inlet temperature is set at 12℃ and the antifreeze protection temperature is set at 5℃.
4, the system vacuum pressure 90-130Pa, must ensure that the vacuum time, so as not to dry completely residual water in the system, it is best to ensure that the vacuum pressure to the required to continue to pump for 12 hours, and then hold the pressure for 12 hours, to ensure that the system (including vapor, liquid storage tank no water);
5. Test rule of each parameter point when the unit starts trial operation, under standard working conditions:
The ambient temperature is 35 ° C, the inlet and outlet water temperature is 12 ° C/ 7 ° C, the standard water flow, the compressor suction temperature of the unit is generally about 8 ° C/85C, suction pressure is above 4BAR, the high pressure is about 18-19bar;Especially in the trial run pay attention to suction pressure, even in the minimum outdoor refrigeration temperature at 21℃, suction pressure should be more than 3.8BAR;If the pressure is too low and the return temperature is too low, it should be checked:
A. Whether the throttling device is normal;
B. Whether the water flow is within the standard flow range;
C. Whether the refrigerant filling of the system is in accordance with the nameplate;
D. Whether the inlet and outlet water temperature of the unit is normal;
E. Plate heat exchanger has no local blockage.
6. When installing the compressor, it is best to load the system within 30 minutes after the rubber plug of the compressor is opened.The drying filter should be installed at the end, and should be loaded into the system immediately after the protective cover is opened;
7, in the whole system welding, must be filled with nitrogen protection welding;When welding plate heat exchanger, it is necessary to protect the plate welding by water cooling so as not to damage the plate heat exchanger by welding.
8. Test whether the low voltage switch of the single cooling unit is above 2BAR;
9. Test whether the outlet temperature sensor is normal, whether it is damaged, and whether it is installed in the outlet of the plate heat exchanger;
10, Y type water filter filter must be cleaned and checked regularly;
11. Check whether the water quality in the air conditioning water system meets the requirements, whether there are impurities, and whether other acidity and alkalinity meet the operating requirements of the unit.
