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Analysis of high temperature shutdown of screw compressor

After the host arrived at the user's place, after careful installation and inspection, the test conditions can be reached, and the relevant personnel decided to debug on the ground. After completing a series of preparations, first start the compressor twice, and only after there are no abnormal conditionsstart up.


The compressor is operated at a pressure of 0.4MPa for about 10 minutes. Check that the moving parts of the equipment operate normally without any abnormal sound. Then adjust the pressure to the rated pressure of 0.7MPa. After running for about 30 minutes, the compressor will stop automatically.


The personnel present quickly cut off the power supply and inspected the equipment.

    

First check the main unit, touch the main unit casing with your hands, and feel that the temperature is a bit high; the motor temperature is normal, and the rotor and the motor are flexible by hand, without jamming. No abnormal vibrations and noises were found during operation, which can basically exclude the host andThe problem with the motor. Next, continue to check the oil and gas separator, and found that the temperature meter on the oil and gas separator shows that the exhaust temperature is about 105 ℃.

    

This model is designed for underground coal mines, so its manufacturing standards are implemented in accordance with the MT 687-1997 "Mobile Air Compressors Underground Coal Mine" standard. The standard stipulates that "under specified operating conditions, the temperature of the fuel injection rotary exhaust shall not exceed 100℃"; "During normal operation, the operating temperature of the oil injection rotary temperature control device should not exceed 120 ℃." Because the machine is equipped with a temperature control switch, and the set operating value is about 105 ℃, so you can be sure of this The second shutdown is the action of the temperature control deviceUp.

    

As for how the high temperature phenomenon occurs? First of all, we doubt whether it is caused by the high ambient temperature. At that time, the ambient temperature was about 32℃~33℃, the maximum suction temperature of the compressor was generally limited to below 40℃; and the compressor .It is well ventilated in the open air environment, so there is no possibility of too high suction temperature.

    

In addition, we consider whether the cooling airflow is not cooled according to the designed flow direction because the chassis door is not closed.

    

After discussion, we decided to completely close the case and try again. After starting the machine, it was found that the temperature rose quickly, and the high temperature shutdown occurred again after about 10 minutes of starting the machine. Although it has no effect after closing the case, it can be ruled out that it is cooling airFlow causes.

   

Next, we consider whether the main engine is insufficiently lubricated due to clogged oil filters. It can be seen from the system flow chart of Fig. 1: the lubricating oil inside the oil-gas separator first enters the cooling for cooling, and then is filtered through the oil filter Spray into the inside of the host to achieve the purpose of reducing the exhaust temperature.

    

Although the "three filters" are new after the equipment is repaired, due to the high exhaust temperature of the compressor, after excluding the host and environmental problems, it must be related to the lubricant, so we decided to replace it with a new oil filter try it. In replacement


After the oil filter, there is no improvement, and the same high temperature shutdown phenomenon occurs again.

    

After the shutdown, we carefully checked the oil circulation line: the temperature of the oil filter line is almost the same before and after, which proves that there is no problem of oil filter clogging. When we checked the oil cooler, we found that the temperature of the two pipes of the oil cooler and the oil cooler are different.


A few times, there is almost no temperature difference between the two pipes when touched by hand. This abnormal phenomenon shows that the oil cooler has no cooling effect at all. When this happens, either the outside of the cooler is heavily dusted; or there is a blockage inside, but it is actually cold


However, the outer surface of the cooler is relatively clean, and it is certain that a blockage has occurred inside the cooler, resulting in insufficient oil supply.

    

The cooler is a high-efficiency aluminum finned radiator. The internal cross-sectional area of the lubricating oil is very small. Once the lubricating oil is contaminated, it is easy to block. Since the lubricating oil that has not been cooled is continuously compressed, the temperature of the compressed air does not increase with it,


So it will reach high temperature in a short time.


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