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Reason Of Liquid Hammer And Compressor Overheating In Chiller Compressor

Jan 12, 2021

Reason of liquid hammer and compressor overheating in chiller compressor


       Low-temperature chillers generally use original imported scroll compressors. Therefore, many customers also call them scroll chillers. During the operation of the chiller, various problems will often cause the compressor to burn out and liquid strike.


     The liquid hammer of the compressor of the cryogenic chiller can cause damage to the scroll. The liquid hammer failure is generally manifested as the obvious metal impact sound inside the compressor. This is the metal fragments after the scroll is crushed. The sound of impact with the compressor housing.


     There are three main situations for liquid shock: one is that a large amount of refrigerant liquid enters the compressor at the moment of startup; the other is that the flow of the evaporator is insufficient (the saving load is reduced), and the compressor has liquid back phenomenon; the third is that the unit heat pump is running except The frost is not good, a large amount of liquid refrigerant enters the compressor without evaporating, or the liquid in the evaporator enters the compressor when the four-way valve is switched.


  So, how do we solve the problem of liquid strike or liquid return?


   1. The piping design should avoid liquid refrigerant entering the compressor when starting up, especially for refrigeration systems with a relatively large charge. Adding a gas-liquid separator to the compressor suction port is an effective way to solve this problem, especially in heat pump units that use reverse cycle hot gas defrosting.


   2. Before starting the machine, preheating the oil cavity of the chiller compressor for a long time can effectively prevent a large amount of refrigerant from accumulating in the lubricating oil. It also has a certain effect on preventing liquid shock.


  3. Water system flow protection is indispensable, so that when the water flow is not enough, it will protect the compressor, and the evaporator will be damaged if the unit has liquid back phenomenon or severely freezes.


  What is the reason for the overheating of the compressor of the chiller equipment? We analyze it from three aspects:


   First, the compressor is overloaded and runs over current. The possible factors are: the cooling water temperature is too high, the refrigerant is charged too much, or there is non-condensed gas such as air in the refrigeration system, which causes the compressor to be overloaded, which manifests as overcurrent and is accompanied by high pressure problems.


  Second, the electrical fault caused the overcurrent operation of the compressor of the low-temperature refrigerator. If the three-phase power supply voltage is too low or the three-phase is unbalanced, the current or one phase current is too large; the communication contactor is damaged, the contact is ablated, and the contact current is too large or the current is too large due to lack of phase.


   Third, the overheating maintenance module SSM of the low-temperature refrigerator is damp or damaged, the central relay is damaged, and the contacts are bad. The performance is overheating when the machine is turned on, and the compressor cannot be started. If the unit electronic board is faulty or communication fault, it may also falsely report the overheat fault.