The tightness of industrial chiller systems is usually an important indicator of the installation or manufacturing quality of refrigeration devices. The leakage of the chiller system not only causes refrigerant leakage or external air infiltration, affecting the normal operation of the refrigeration device, but also causes economic losses and environmental pollution. Due to the large number of welding points and connectors in the installation or assembly process of a large water chiller system, leakage is inevitable, which requires the commissioning personnel to carefully inspect the system for leakage, identify and eliminate each leakage point. System leak detection is the main project in the entire debugging work, and must be carried out carefully, responsibly, meticulously, and patiently.
The inspection methods include:
1. Pressure leak detection;
2. Vacuum leak detection;
3. Halogen lamp and halogen meter leak detection;
4. Soap water leak detection;
5. Water immersion leak detection;
Pressure leak detection in industrial water chiller refrigeration systems is the most effective method for checking and finding leakage points. The leak detection pressure in water chiller refrigeration systems is related to the type of refrigerant used, the cooling method of the water chiller refrigeration system, and the location of pipe sections. For high-pressure systems, the leak detection pressure is approximately 1.25 times the design condensation pressure; The leak detection pressure of the low-pressure system should be approximately 1.20 times the saturation pressure under summer temperature conditions. In this way, the refrigeration device can prevent refrigerant leakage during operation or shutdown. For some refrigeration systems, if acceptance or leak detection criteria are set in advance, leak detection should be performed at the specified pressure. Obviously, the leak detection pressure cannot be arbitrarily increased, otherwise it may damage the equipment and cause accidents. The leak detection pressure in the refrigeration system should be gradually increased. Every time it rises by 0.2 MPa to 3 MPa, the leak prone parts should be inspected. Once a leak point is found, the pressure increase should be stopped immediately. When removing a leak, it is usually necessary to release high-pressure gas from the leaking part. Especially in the case of repair welding, it is necessary to release high-pressure gas, and it is not allowed to weld under high-pressure conditions to avoid accidents.
For ammonia systems, refrigeration compressors can be used to gradually increase the system pressure; For Freon systems, nitrogen or dried air should be used to pressurize to prevent moisture from entering the system. Currently, there are several common leak detection methods:
1.1.1 Soap water leak detection
This is currently the most commonly used leak detection method, especially for medium and large water chiller refrigeration systems, which are basically used to find leakage points. Soap water is usually made with soap or soap powder. Soap water solution should not be too thick, otherwise it will be difficult to flow due to excessive viscosity, and the sensitivity of leak detection will be poor; However, the prepared solution should not be too dilute, otherwise it will be difficult to adhere to the surface of the equipment due to excessive fluidity, and it will be difficult to form bubbles. Soap water can be directly applied to the vulnerable area with a brush to observe whether the area is bubbling. For parts that are difficult to observe directly, mirror reflection and flashlight can be used for inspection. After the leak detection, the soapy water applied should be wiped dry to prevent corrosion.
1.1.2 Water immersion leak detection
The sensitivity of immersion leak detection is higher than that of soapy water leak detection. This method is usually used for small Freon water chillers. When using immersion leak detection, equipment in the system that is not allowed to contact water should be removed (such as various relays, electrical control equipment, etc.). It is best to use clean warm water for soaking, as the surface tension of warm water is less than that of cold water, which is prone to the formation of bubbles. If equipped with a strong light source for irradiation, the leakage site is easily found. After immersion leak detection, the surface should be immediately dried with compressed air to prevent corrosion of the metal.
1.1.3 Halogen lamp and halogen meter leak detection
These are two special devices for inspecting the Freon water chiller system. "Because Freon refrigerants contain halogen components such as fluorine (F2), chlorine (Cl2), and bromine (Br), when they encounter hot copper parts, they can generate different colors of flame, thereby identifying the leak location.".
Vacuum leak detection
After the industrial water chiller system has passed the pressure leak detection, it is also necessary to conduct a vacuum leak detection, as some components may have one-way leakage. Only after the pressure and vacuum leak detection meet the requirements can the tightness of the refrigeration system be ensured. In addition, system evacuation can also remove moisture, especially in the Freon system, as evacuation and drying are an important part of the unit commissioning process. Vacuum pumps are commonly used for system evacuation.
Vacuum Pump Evacuation: Refrigeration systems should be evacuated using a vacuum pump, especially for refrigeration systems with closed compressors. Vacuum pumps must be used for evacuation. This not only reduces the system to extremely low (i.e., extremely high vacuum), removes air and moisture from the system, but also protects the compressor and motor. The absolute pressure of the refrigeration system should generally be pumped below 700 Pa, and should remain basically unchanged after 24 hours. It should be pointed out that after long-term use of the vacuum pump, water vapor in the system may enter the lubricating oil of the vacuum pump, affecting its evacuation ability. Therefore, the lubricating oil needs to be replaced frequently.
OWADA water cooled and air cooled chillers