Discuss the reasons for slow temperature drop in the constant temperature and humidity testing machine and maintenance methods

The reasons for the slow cooling of the constant temperature and humidity testing machine and its maintenance method The constant temperature and humidity testing machine is also called the high and low temperature damp heat test box . It is used to test the adaptability of various materials in the environments of high and low temperature, high temperature, high humidity, and damp heat. reliability. The user may appear when using the device: What is the reason for the slow cooling of the constant temperature and humidity tester? Why does the constant temperature and humidity testing machine slow down? What can I do if the temperature drop in the high and low temperature test box does not go? Why can't the temperature reach -40 degrees? With regard to the series of problems in which the constant temperature and humidity testing machine is slow in cooling or unable to cool down, have you ever encountered it? The following reasons for the slow cooling of the constant temperature and humidity tester by Kevin are as follows:

Reason one:

Under normal circumstances, the constant temperature and humidity testing machine will reduce the temperature to the corresponding value according to the set time range. However, due to the long use time of the equipment or improper operation, it will cause the temperature and humidity testing machine to cool down slowly. Now how Solve this problem and conduct technical discussions.

1. The cause of the failure was not determined. The cause of the failure was further confirmed by the control process of the test chamber. The test chamber had two sets of refrigeration units.

2. One is the main unit and the other is the auxiliary unit. When the cooling rate is relatively high, the two units work at the same time. In the initial stage of the temperature maintenance period, the two units still work simultaneously. When the temperature is initially stabilized, the auxiliary unit stops working and the host group maintains the temperature stability. If the host group R23 is leaked, the cooling effect of the host group will be small. Since the two units work at the same time during the cooling process, there is no phenomenon that the temperature cannot be stabilized, and the indicated cooling rate is reduced. In the temperature maintenance phase, once the auxiliary unit stops working, the main unit has no cooling effect, and the air in the test chamber will slowly rise. When the temperature rises to a certain extent, the control system will start the auxiliary unit to cool down the temperature and set the temperature down. In the vicinity of the fixed value (-55°C), the auxiliary unit will stop working again. If so, the fault phenomenon will occur.

At this point, it was confirmed that the cause of the production failure was the leakage of refrigerant R23 of the low-temperature (R23)-class unit of the host group. The leakage of the refrigeration system was checked and checked by a combination of leak detector and soapy water. It was found that the valve stem of a hot gas bypass solenoid valve cracked approximately 1 cm. Replace the solenoid valve to recharge the system and the system is operating normally. As can be seen from the above, the analysis and judgment of this fault phenomenon is basically easy to difficult, first "outside" after "inside", first "electrical" after "cooling" context to analyze and judge, familiar with and Understanding the principle and working process of the constant temperature and humidity testing machine is the basis for analyzing faults to determine faults.

Reason two:

1. Because 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 wiring from the main power supply to each compressor is normal, and the electrical appliance There is no problem with the system.

2. There is no problem with the electrical system and continue to check the refrigeration system. First of all, it is checked that the exhaust and suction pressures of low-temperature (R23) compressors of the two sets of refrigeration units are lower than normal and the suction pressure is in a pumped-out state, indicating that the amount of refrigerant in the main refrigeration units is insufficient.

3. Touch the exhaust and suction piping of the R23 compressor of the main unit and find that the temperature of the exhaust pipe is not high and the temperature of the suction pipe is not low (unfrosted). This also explains the host group. The lack of R23 refrigerant.

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