With the development of people in the military, aerospace and navigation fields, many equipment will work in the environment of high temperature, low temperature and high humidity. The equipment will face greater challenges in this environment. The stability of the equipment has an important impact on the work of the equipment.
The high and low temperature humidity test chamber (hereinafter referred to as the high and low temperature humidity chamber) is used to inspect the performance of materials in aerospace and navigation products under high temperature, damp heat and other environments. Its structure and working principle have certain particularity.
1.Use of high and low temperature humidity chamber
Before the environmental experiment, it is necessary to master the performance of the tested sample, the experimental procedure, the experimental conditions, and the experimental technology. At the same time, it is necessary to master the technology of using the equipment, clearly understand the structure of the equipment, especially master the performance and operation of the controller. At the same time, the staff must read the operation manual in detail for many times to avoid mistakes in operation, As a result, the equipment cannot operate normally, resulting in errors in the test data and damage to the samples in the experiment. In order to ensure the accuracy of the experimental data in the experiment, it is necessary to select reasonable equipment for use in the experiment. The selection of the high and low temperature humidity chamber should be based on the actual situation of the experimental sample. The volume between the experimental chamber and the test object should always maintain a reasonable proportion. When conducting the experiment on the heating test article, its volume should be less than 10% of the effective volume of the experimental calibration. The proportion of the non heating test article to the effective volume of the experimental chamber should be 20%.
During the experiment, the position of the test object should be correctly placed. The position between the test object and the chamber wall should be kept above 20 cm. If multiple samples need to be placed during the experiment, all samples should be placed on the same plane as far as possible.
The position where the sample is placed shall not cause the drawing air outlet and air outlet to be blocked, and at the same time, a certain distance shall be kept from the humidity sensor to ensure the normal temperature during the experiment. In the use of the high and low temperature wet chamber, the following points shall be noted:
(1) During use, ensure that the high and low humidity heat chamberes are safely grounded to avoid casualties due to electrostatic induction.
(2) The chamber shall not be touched by hand during operation.
(3) Unless the chamber door cannot be opened for special reasons during the operation of the equipment, the following adverse consequences may occur:
1) The temperature inside the door is still very high
2) High temperature and humidity will rush out of the chamber.
3) High temperature may cause fire alarm.
4) Unless necessary, the lighting shall be turned off.
5) Try to avoid repeated opening within 15 minutes during use.
6) When the high and low temperature humidity chamber is running at low temperature, it is better to dry the equipment for 30 minutes at 60 ℃, and then open the door to avoid icing on the evaporator or affecting the measurement time of subsequent experiments
7) During operation, in order to ensure the safety of equipment and operators, the overtemperature protector and circuit breaker shall be checked regularly.
8) In addition to full-time personnel, professional electricians are also required to participate in the maintenance and inspection of equipment.
2.Repair and maintenance of common problems
Maintenance of common problems of high and low temperature humidity chamber
During the high temperature test, if the test temperature cannot reach the temperature value required by the test, the electrical system shall be inspected, and the causes of the faults shall be eliminated one by one.
If the temperature rises slowly, the air circulation system shall be inspected, and the opening state of the regulating plate in the air circulation system shall be observed.
If the temperature rises too fast, the rotation of the air circulation runner shall be detected, If the temperature rises rapidly, the PID setting parameters need to be adjusted.
If the temperature rises directly to the overtemperature protection, it can be concluded that the controller has a fault, and the control instrument should be replaced in time.
When the low temperature fails to meet the experimental requirements, it is necessary to observe the temperature change. Whether the temperature rises after falling to a certain value or whether the temperature drops slowly. The former is generally caused by the poor environment of the dry equipment. The location of the equipment and the ambient temperature should be observed. If the working requirements of the equipment are not met, timely adjustment should be made. If it is the latter, the equipment shall be checked to see if the laboratory has been dried before the low temperature test. If the working room is dry, and the test articles are put into the laboratory, whether there are too many test articles stacked in the laboratory, which causes the ventilation cycle in the laboratory to fail to meet the requirements. After the above fault causes are eliminated, if the cooling rate is still slow, it can be determined that there is a problem with the refrigeration system, The refrigeration system should be overhauled!
2.2 Equipment maintenance contents
The main contents of equipment maintenance include preventive maintenance and predictive maintenance. Among the two types of preventive maintenance, the maintenance that needs to be carried out once a week includes: cleaning the laboratory body of the water collection tray and condensate. The maintenance that needs to be carried out by customers in special quarters includes: washing the humidification water pipe, flushing the system or medium cooling water pipe. The maintenance that needs to be carried out every six months includes cleaning the air cooling equipment (condenser), and the maintenance that needs to be carried out every year, Clean the scale inside the humidifier, remove dust from the maintenance electrical control cabinet of the AC (high current) contactor. At the same time, the lubricating oil used by the compressor should be replaced every 2-3 years. Predictive maintenance mainly includes weekly maintenance, monthly maintenance and quarterly maintenance.
Weekly maintenance includes: check the balance pressure and suction and discharge pressure of the compressor, check the color of the oil in the compressor, and check the oil body. Monthly maintenance includes. Check the exhaust and suction temperature of the compressor, the liquid mirror in the condenser and the discharge temperature, and the temperature difference between the water in and out of the cold water pipe. Check the heating rate and cooling rate of the equipment. Check the working current of the compressor motor every quarter.
Regular maintenance of the equipment can not only improve the stability of the equipment during operation and the accuracy of the experiment, but also extend the service life of the equipment to a certain extent. Therefore, attention should be paid to the maintenance of the high and low temperature humidity chamber in the future.
High and low temperature wet heat chamber is a special refrigeration equipment, so its use, maintenance and repair should start from refrigeration, electrical control, thermal engineering and other aspects. In the process of use, attention should be paid to the use specifications. During maintenance, the faults that may be caused by operation should be eliminated first, and then the faults that exist in the equipment itself should be repaired. After the equipment fails, maintenance should be carried out on the basis of mastering the equipment structure and working principle. In addition, the maintenance of the equipment must be carried out on time, and the maintenance of the equipment cannot be ignored because the equipment has not failed for a period of time