Compressor and operation method

Abstract

The present invention provides a compressor and its operating method. An on-off valve is provided on the suction side of the compressor main body, and the amount of gas pushed out to the discharge side of the compressor main body and the amount of gas leaked to the suction side are set in a control device. Roughly the same as the lower limit speed of the motor. In the range where the motor speed is above the lower limit speed and below the maximum speed, the control device determines the control speed for eliminating the deviation of the detected pressure from the preset target pressure, and when the control speed is greater than the lower limit speed Open the on-off valve, and close the on-off valve when the controlled speed is lower than the lower limit speed. According to such a configuration, the range of rotation speed control versus capacity control can be expanded, and the problem of backflow of oil to the suction side can be avoided.

Description

technical field [0001] The present invention relates to a compressor and a method of operating the same. Background technique [0002] In general, in a screw compressor, the rotation of the screw rotors pushes out gas on the discharge side, but the gas leaks to the suction side due to gaps formed between the screw rotors or between the screw rotors and the casing. As the rotational speed decreases, the leakage of the gas to the suction side becomes more obvious. [0003] In order to avoid an increase in the leakage of compressed gas to the low-pressure side of the compressor body due to an excessive reduction in the rotational speed of the motor driving the main body of the oil-free screw compressor, for example, the following method is described in JP-A-2002-054578: When the speed is higher than the preset value, the suction regulating valve on the suction side of the compressor body is opened to control the motor speed, and when the speed reaches the preset value, the spe...

AI Technical Summary

Problems solved by technology

The control using the suction control valve has the following problems: the suction control valve must be frequently opened and closed, the mechanical parts such as the valve body of the suction control valve are worn out a lot, and the pressure pulsation is easy to occur.

[0007] However, in an oil-cooled screw compressor, the gas leaked to the suction side moves with the oil, and when the speed drops to a very low speed, the amount of gas leaked to the suction side will be larger than the amount of gas pushed out to the discharge side. As the amount of gas increases, the oil flows back to the suction side, and the suction filter installed in the flow path on the suction side becomes contaminated with oil, resulting in a decrease in the function of the filter and a reduction in the suction volume.

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