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Cause analysis of low pressure alarm of chiller
Water chillers are widely used in industries, such as food, laboratories, electroplating industries, etc. What is the reason for the low-pressure alarm during the use of the chiller?
Let us learn together.
Fault 1: Leakage in the system
Reason: There are leaks in the connecting pipes of the refrigeration system, such as welding problems, corrosion problems caused by the environment, fracture problems caused by mechanical vibration, human factors, etc.
Treatment method: First of all, you must use a leak detector (soap water, or detergent with water) or a halogen leak detector to find the leak point. When the leak point is found, use welding equipment to weld and do the necessary vacuum treatment. After the specified amount of refrigerant is charged by the factory, the equipment can resume normal operation.
Fault two, the system is blocked
There are probably four reasons for the blockage of the refrigeration system:
a. Sundries are blocked;
b. Ice block;
c. The solenoid valve is broken;
d. The expansion valve is broken, etc.
Clogging by debris: Because the refrigeration system has strict requirements in all links of production and manufacturing, it is necessary to ensure that each link is cleaned. However, most of the cold water (refrigeration) machine manufacturers currently purchase parts and then assemble them. In this way, it is inevitable that some systems will be impure, which will cause system blockage in severe cases (generally blockages occur in filters or expansion valves). Entrance) Therefore, the manufacturers of cold water (refrigeration) machines have installed "filters" in the refrigeration system to filter out impurities in the system. When the impurities in the pipes of the refrigeration system accumulate to a certain extent, the filter will be blocked, which will affect the refrigerant throughput of the system. In severe cases, a low pressure failure will occur.
Recognition: If the filter is clogged due to a dirty system, it will only cause the cooling capacity of the equipment to decrease, and you will not even feel the impact. When the "filter" is slightly clogged, there will be a temperature difference between the inlet and outlet of the "filter", which can be felt when you hold the inlet and outlet with your hand. In severe cases, the filter will appear dew or frost. If the filter is condensed or frost (when the machine is running, the dew will not be counted when the machine is stopped), it can be judged as a clogged filter.
Treatment: Replace the filter of the same model.
Ice blockage: Ice blockage is essentially the presence of water in the system pipes. The water in the system runs together with the refrigerant until the throttle valve (expansion valve) undergoes throttling expansion, and forms a low temperature and low pressure state at the throttle valve outlet. When the temperature (the outlet temperature of the throttle valve) drops below the freezing point, the moisture in the refrigerant will form ice here, which will block the throttle valve (expansion valve) and cause a low-pressure fault. The ice block occurs at the outlet of the throttle valve (expansion valve).
Treatment: It is best to use a detachable filter, which is equipped with "calcium chloride" (a powerful water-absorbing material) to filter the water in the system thoroughly for many times, and then replace it with a disposable of the same model filter.
Solenoid valve‘s broken: Solenoid valve is an indispensable part of the refrigeration system, which has the function of protecting the safety of the system (when the compressor stops working, the refrigerant is cut off, and the refrigerant does not continue to flow to the evaporator. A large amount of refrigerant, when the compressor is restarted next time, it is easy to cause the compressor valve plate to smash and damage the compressor). When the solenoid valve is damaged, the flow of refrigerant is blocked, causing a low pressure failure. At present, most manufacturers have omitted solenoid valves in order to reduce costs, but this also left hidden dangers to the equipment.
Recognition: It is better to distinguish if the solenoid valve is broken, and there are two cases when the solenoid valve is broken:
1. The solenoid valve coil cannot be opened due to the burning of the solenoid valve coil. Use a multimeter to measure the solenoid valve coil to determine whether the solenoid valve is burned out;
2. The valve body of the solenoid valve itself is broken, causing the membrane inside the valve to fail to open. When there is a temperature difference between the inlet and outlet of the solenoid valve, it indicates that the solenoid valve is defective.
Expansion valve damaged: Expansion valve is one of the four major components of the refrigeration system and is an indispensable component. The condensed low-temperature and high-pressure refrigerant flows through the expansion valve and is throttled by the expansion valve. It expands and evaporates at the outlet of the expansion valve to form a low-temperature and low-pressure gas-liquid mixed refrigerant, thereby taking away heat from the system and forming a refrigeration process.
Expansion valves are divided into mechanical expansion valves and electronic expansion valves. The mechanical expansion valve is affected by the environment during use. Some environments have corrosive gases that will corrode the liquid and cause the expansion valve to corrode. Most of the expansion valve’s temperature sensing bulb leaks (the connecting pipe connecting the temperature sensing bulb and the valve body is corroded) ). Although the electronic expansion valve has the advantages of large temperature control range and high precision that the mechanical expansion valve cannot surpass, it has an independent control system, which also virtually increases the failure rate.
Treatment: If the expansion valve is damaged, only replace it.
Fault three, the heat exchange of the evaporator is seriously insufficient
There are probably two reasons for insufficient heat exchange in the evaporator:
a. Insufficient water flow in the evaporator,
b. Blockage of foreign matter in the evaporator (or scaling on the surface of the evaporator tube in the evaporator, or insufficient heat exchange due to crystallization)
Insufficient water flow in the evaporator: The main factors that cause this phenomenon are the failure of the water pump or the entry of foreign matter in the impeller of the water pump, or the leakage of the water inlet pipe of the water pump (which is difficult to check and requires careful analysis), resulting in insufficient water flow.
Treatment: Replace the water pump, or disassemble the water pump to clear the foreign matter in the impeller, then the fault can be eliminated.
The evaporator is blocked or the evaporator tube is fouled: To determine whether the evaporator is blocked or the evaporator tube is fouled, the problem of the water pump must be eliminated first, and the water pump and the water inlet pipe can be determined after the normal condition. The evaporator blockage or structure has a common and very obvious feature (only applicable to medium temperature units): when the equipment is normal, there will be no large amount of condensate or frost or ice on the surface of the compressor. When you see a large amount of condensate or frost on the surface of the compressor, it can basically be judged that the evaporator is blocked.
Treatment: If the evaporator is blocked or the evaporator tube is fouled, the evaporator should be disassembled, and the evaporator tube should be removed and rinsed with a high-pressure water gun or soaked in a special chemical liquid.
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Shanghai Kubao Refrigeration Equipment Co., Ltd. is a comprehensive enterprise integrating refrigeration equipment, product development and technical services. The company's main products are: wholesale foreign and domestic compressors and their spare parts; production of various outdoor silent units and complete sets of chillers; cold storage body, unit, installation and commissioning one-stop service; joint production of condensers and evaporators. Based on the tenet of "Quality First, Credit First", the company wholeheartedly provides users with high-quality products and excellent services, and cooperates with users to create a brilliant future for the refrigeration industry.
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