Constant temperature and humidity box does not cool / can not reduce temperature failure analysis - Database & Sql Blog Articles

Constant temperature and humidity box does not cool / can not reduce temperature failure analysis

Because customers often encounter

Humidity Chamber

The situation is not cooling, so I will study and study with you here today. The following comments are for reference only.

Analysis 1: Since the temperature is not maintained, observe whether the refrigeration compressor can be started during the operation of the test chamber, and the compressor can be started during the operation of the environmental test equipment, indicating that the electrical circuit from the main power supply to each compressor is normal. There is no problem with the electrical system.
There is no problem with the electrical system and continue to check the refrigeration system. Firstly, the exhaust and suction pressures of the low-temperature (R23) compressors of the two groups of refrigeration units are lower than the normal values, and the suction pressure is evacuated, indicating that the refrigerant capacity of the main refrigeration unit is insufficient.

Touching the exhaust and suction lines of the R23 compressor of the main unit by hand, it is found that the temperature of the exhaust line is not high, and the temperature of the suction line is not low (not frosted), which also indicates the R23 of the host group. Lack of refrigerant.

Analysis 2: The cause of the failure was not determined, and the cause of the failure was further confirmed in conjunction with the control process of the test chamber. The test chamber has two sets of refrigeration units.

One is the main unit and the other is the auxiliary unit. When the cooling rate is large, the two sets of units work at the same time. In the initial stage of the temperature maintenance stage, the two units still work at the same time. When the temperature is initially stabilized, the auxiliary unit stops working, and the host group maintains the temperature stability. If the host group R23 leaks, the cooling effect of the host group will be small. Because the two units work at the same time during the cooling process, there is no temperature stability, and the cooling rate is indicated to decrease. In the temperature maintenance phase, once the auxiliary unit stops working, the main unit has no cooling effect, and the air in the test box will rise slowly. When the temperature rises to a certain level, the control system will start the auxiliary unit to cool down and lower the temperature to the setting. After the fixed value (-55 °C), the auxiliary unit stops working again. If it is repeated, the fault phenomenon shown in Figure 3 will appear.

At this point, the cause of the production failure has been confirmed to be that the refrigerant R23 of the low temperature (R23) stage unit of the main unit leaks.

The leak detection of the refrigeration system was carried out by a combination of a leak detector and soapy water, and it was found that the stem of a hot gas bypass solenoid valve cracked a slit of about 1 cm. Replace the solenoid valve, refill the system with fluorine, and the system is operating normally. As can be seen from the above, the analysis and judgment of the fault phenomenon is basically easy and difficult. First, the "outside" and "inside", first "electrical" and then "refrigeration" are analyzed and judged, familiar and Understanding the principle and working process of the test chamber is the basis for analyzing faults to determine faults.

According to the above analysis, only by deep understanding of the working principle and working process of the test box can the problems of the test box during operation be quickly solved. I hope this article can be more effective in environmental equipment management operation and maintenance personnel, and jointly promote the development of environmental engineering in China.