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In the process of debugging the chiller group, many friends will encounter the oil running phenomenon of the unit many times. Most of the units with this fault are using the full liquid evaporator, so the small editor specially learned some practical experience and opinions from the old master, and took them out to discuss with you.
At present, there are many chiller units in the market according to the following idea structure: the refrigerant oil and refrigerant are confused, the refrigerant is separated by the oil separator, and the refrigerant is returned to the compressor through the full-liquid evaporator. Refrigeration effect is good, this kind of model for larger promotion, but there is a problem in its operation, it is easy to run "oil", namely when the cooling water temperature is low, the exhaust heat is not high, and oil and refrigerant were incomplete, confusing after entering the heat interchanger causes low voltage on the low side, moreover causes the expansion valve congestion caused the unit cannot be started.
The fault symptoms of the chiller are as follows:
1, oil respectively inside don't see any traces of oil, oil now did not accumulate in the condenser, but after the expansion valve into the evaporator, oil will stick to the evaporator heat exchange tubes, make evaporator evaporation effect is bad, causing the pressure in the evaporator is low, at the same time make the compressor suction superheat is low so that the refrigerant liquid suction directly, The discharge temperature of the compressor is very low, and the oil and refrigerant still cannot be separated. Such a vicious cycle will make all the oil gather in the evaporator. The compressor makes great noise because of insufficient oil supply, and even stops with the oil level alarm of the unit oil separator.
2. No trace of oil can be seen in the oil separator. All the oil reaches the condenser with the exhaust. If the water temperature continues to be low, all the oil will gather in the condenser and cause oil blockage in the expansion valve.
The above is the so-called oil running phenomenon. The main reason is that the temperature of chilled water is low and the exhaust temperature is low.
Solutions to such problems encountered in the boot process are as follows:
1. When it is found that the oil level in the oil content is decreasing, immediately adjust the chiller to manual control mode to limit the compressor load, such as limiting its energy to 50%.
2. Increase the condensing pressure
3. Reduce the low-pressure alarm value and low-pressure shutdown value of the chiller to the allowable range to ensure that the chiller can be in the running state as far as possible
4. If the oil level is still very low at this time, and the pressure in the evaporator is also very low, it is necessary to consider whether the oil is running into the evaporator. See from the evaporator liquid mirror whether there is a lot of white foam billowing, if there is, it means that the oil is in the evaporator, otherwise it may be in the condenser.
5. With the above steps, after half an hour or so, the temperature of cooling water and exhaust temperature should rise to normal, and the following oil collection begins:
A: The oil is in the evaporator. Close attention to the temperature of the chilled water at this time, to be suitable for reducing the flow first, make water temperature is reduced, and then rapidly increasing traffic, the evaporator outlet temperature rise quickly, and then the saturation temperature of refrigerant will be more than a lot of water temperature, and then the refrigerant boiling, frozen oil will foam as the troubled refrigerants are such as compressor, exhaust temperature should drop some at this moment, But it should also be far beyond the temperature of the oil and the refrigerant, and then bring the oil back to the oil separator and make them separate. Several times, the oil will be all back into the oil separator. Here pay attention to the time interval of each adjustment of water quantity, it is best to make the exhaust temperature rise to the most correct before adjustment after each adjustment.
B: The oil is in the condenser. At this time do not need to pay too much attention to the water temperature, as long as the unit can operate normally will not have a big problem. At this time, the expansion valve should be gradually opened to the maximum (the opening process is not too fast to prevent the damage of the copper tube in the evaporator by too much liquid supply), and wait for a few minutes until the high and low pressure of the unit is balanced. At this time, a large amount of white foam can be seen from the liquid mirror of the evaporator, which is that the oil has entered the evaporator from the condenser. Just repeat step A and the oil will come back quickly.