Preparation and commissioning before starting the refrigeration dryer

（1） Prepare for startup

1. Open the electric control box and fasten all terminals to avoid looseness during transportation and installation; Check whether the power supply voltage is consistent with the nameplate, and the voltage fluctuation range cannot exceed 10% of the rated voltage;

2. Check the evaporation pressure gauge and condensation pressure gauge on the panel. The readings on the two pressure gauges should be balanced, and the readings should not be less than 0.4~0.55Mpa; If it is found that the value is lower than this value, it is not allowed to start the dryer, otherwise the compressor will be damaged, and it should be immediately reported to the service department for inspection of the refrigeration system;

3. Inspection of working condition requirements: whether the air inlet pressure, inlet temperature, processing air volume, cooling water pressure, and temperature are consistent;

4. For water cooled cold dryers, open the cooling water inlet and outlet valves;

5. Before starting the machine, the compressed air pipeline system must be purged to prevent debris from entering the dryer and affecting the use of the filter.

Method: Cut off the compressed air inlet and outlet valves of the drying and purification equipment, open the air bypass valve, start the air compressor, and allow the gas to bypass for about half an hour for purging.

（2） No-load commissioning

1. Reset the low voltage protection value to 0.1Mpa;

2. Close the hot gas bypass valve and hand valve to fully throttle the freon through the expansion valve;

3. Observe that the evaporation pressure should be maintained between 0.18-0.3 Mpa (determined by the opening degree of the expansion valve), allowing the compressor surface to freeze, and run for about 5 minutes;

4. Slowly adjust the hot gas bypass valve to slowly move the evaporation pressure upward to 0.4 Mpa, and then the compressor begins to defrost; The compressor temperature is about 10 ℃, and the exhaust temperature is about 50-80 ℃.

Note: If there is abnormal noise from the compressor or abnormal changes in the pressure gauge during startup, immediately shut down the machine for inspection and timely troubleshooting.

（3） Load Debugging

The no-load operation is normal for about half an hour, and the loading debugging is started.

1. Close the air outlet valve, slowly open the compressed air inlet valve (especially for small cold dryers), and keep the air bypass valve open (if there is an air bypass system) to slowly pressurize the dryer;

2. Check the air pipes, flanges, and drains for air leaks, and promptly eliminate faults;

3. After about 15 minutes of operation, slowly open the air outlet valve and close the bypass valve;

4. Adjust the hot gas bypass valve (hand valve), and adjust the expansion valve for small refrigerated dryers; Make the evaporation pressure within the range of 0.4~0.55 Mpa, observe and record the fluctuation of condensation pressure and evaporation pressure, check whether the action of the drainage device is normal, observe the operating interval of the fan, and compare it with no-load operation. Readjust the pressure switch setting to 0.2Mpa.

5. Adjust the condensation pressure, which should generally be 1.2~1.6 Mpa (up to 2.5 Mpa); If it is below this range, for air-cooled models, check and adjust the fan high and low pressure switch settings; For water cooled models, adjust the opening size of the water volume regulating valve.

Note: During loading and debugging, the evaporation pressure will fluctuate slightly upward.

It is sometimes normal for the cooling fan to keep on and off, and it should be determined according to the working conditions.

◆ Adjustment method for hot gas bypass valve: Rotate the bypass valve adjusting screw clockwise to increase the evaporation pressure; On the contrary, the evaporation pressure decreases. As shown in the figure:

◆ Adjustment method of expansion valve (small cold dryer): unscrew the lower end cap of the expansion valve, rotate the valve rod for 1/4-1/2 turns each time, and the evaporation pressure increases clockwise; On the contrary, the evaporation pressure decreases;

Note: 1. The expansion valve generally does not require adjustment. Only when the hot gas bypass valve cannot be adjusted, first close all the hot gas bypass valves, adjust the expansion valve to stabilize the evaporation pressure at 0.3 Mpa, and then adjust the hot gas bypass valve.

2. The regulation of the three valves is not independent, but interrelated; During adjustment, it is necessary to adjust the valve while observing the pressure change until the working pressure is within the normal range and stable.

（4） Shutdown steps: manually drain (or drain) water until it is clean before shutdown; When shutting down, first close the air inlet valve, then press the stop button to cut off the power supply; For water cooled type, close the cooling water inlet valve.

ARTICLE SOURCE: South Heating and Ventilation Society