JPH08319982A - Two-stage unlubricated screw compressor - Google Patents

Abstract

PURPOSE: To feed dry air, containing no drain, to a two-stage compressor and to prevent drain from residing at the two-stage compressor after a stop by a method wherein when the compressor is stopped, after unload operation is forcibly effected for a given time, the compressor is stopped. CONSTITUTION: Compressed air the temperature of which is increased in such a way to be boosted by a one-stag compressor 1 is cooled by a cooler 3 (an intercooler). After the compressed air is compressed to a given pressure by a two-stage compressor body 2, it is discharged through a cooler 4 (a high precooler), a check valve 9, and a cooler 5 (an after-cooler). In which case, when an amount of using air is decreased and a pressure in a delivery piping is increased to a value higher than a given pressure, the increased pressure is detected by a pressure switch 10 to switch two three-way solenoid valves 12 and 13, a chamber A is pressurized, and an intake air throttle valve 6 is closed. Further, simultaneously, a gas release valve 7 is opened, and air in a delivery piping running between a compressor body and the check valve 9 is released (unloaded). After unload operation is performed for a given time, the compressor is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage oilless screw compressor.

[0002]

2. Description of the Related Art In the case of a two-stage oilless screw compressor, it is disclosed in, for example, Japanese Patent Laid-Open No. 63-61780.
The gas compressed by the first-stage compressor is cooled by the cooler and boosted by the second-stage compressor, then cooled by the cooler and discharged to the equipment used.When the pressure in the discharge pipe rises above a certain pressure, suction is performed. The valve at the inlet is closed and the discharge pressure is released to the atmosphere, and the unloading operation is performed. When the pressure in the discharge pipe drops below a certain pressure, the valve at the inlet is opened and the load operation is performed. When the operation was stopped, the intake valve was instantly closed, the gas in the discharge pipe was discharged, and the operation was stopped regardless of the load or unload state.

[0003]

In the above-mentioned prior art, in the two-stage oilless screw compressor, at the time of stop, the suction valve is closed, the gas in the discharge pipe is opened to the atmosphere, and the method is instantaneously stopped. Was used. This is the driving state loaded,
When the stop process was performed, it stopped instantly regardless of the unload status. This is because when the operating condition is the load condition, the intake air is pressurized to about 2 kg / cm ² (g) by the single-stage compressor, and the compressed air is cooled by the intercooler, which causes drainage and contains drainage. Compressed air had entered the two-stage compressor. If the compressor is stopped in this state, drainage may remain in the main body of the two-stage compressor, and if the compressor is not operated for a long period of time, it will cause rusting of the rotor and casing inside of the two-stage compressor body. I was afraid. A drain separator was installed between the intercooler and the main body of the two-stage compressor, but it was impossible to separate the drain 100%.

An object of the present invention is to solve these problems in the prior art.

[0005]

In order to solve the above problems, the present invention uses the following means as a method of stopping a compressor. That is, the circuit in which the auxiliary relay and the time delay relay are connected in parallel and the circuit in which the switch is connected in series are connected to the compressor operating power supply. A circuit is provided to disconnect the input line to the solenoid valve coil for unload switching when the switch of the auxiliary relay is turned on, and forcibly unload and stop for a limited time of the time delay relay.

[0006]

[Operation] By using the circuit described above and turning on the switch in this circuit, the unloading operation is forcibly performed for the set time,
Stop. When stopping the compressor for a long period of time, by performing this stopping process, a minute amount of atmospheric air is sucked in by the one-stage main body during unloading, and the discharge pressure is almost 0 kgf / cm.
^Since it is ² (g), the dry air containing no drain is supplied to the two-stage compressor, and the drain does not remain in the two-stage compressor after the stop.

[0007]

FIG. 1 is a system diagram of capacity control of two-stage oilless screw compression according to an embodiment of the present invention. The present compressor is composed of a one-stage compressor 1, a two-stage compressor 2 and other coolers. The compressors 1 and 2 are screw type rotary rotary compressors. When the one-stage compressor 1 operates, air is sucked through the suction throttle valve 6. Compressed air that has been heated up to a high temperature by the first-stage compressor 1 is a cooler 3 (intercooler).
The cooled compressed air is compressed by the two-stage compressor body 2 to a predetermined pressure, and is discharged through the cooler 4 (high precooler), the check valve 9, and the cooler 6 (aftercooler).

When the amount of air used decreases and the pressure in the discharge pipe rises above a predetermined pressure, the pressure switch 10 detects and disconnects the input lines of the coils of the three-way solenoid valve 12 and the three-way solenoid valve 13, Switching the three-way solenoid valves 12 and 13,
The chamber A is pressurized and the suction throttle valve 6 is closed. At the same time release valve 7
Opens, and the air in the discharge pipe between the compressor body and the check valve 9 is discharged (hereinafter, this operation is called unloading).

After that, when the amount of air used increases and the pressure in the discharge pipe decreases to a predetermined pressure or less, the pressure switch 10 similarly detects and the input wires of the coils of the three-way solenoid valves 12 and 13 are connected to each other, and the three-way solenoid valves are connected. The solenoid valves 12 and 13 are switched to pressurize the B chamber, and the suction throttle valve 6 opens. At the same time, the release valve 7 returns to normal operation (hereinafter, this operation is called load).

Normally, when the stop processing is performed, the three-way solenoid valve 1
The coils of 3, 14 are energized, the three-way solenoid valve is switched, A
The chamber was pressurized, and the suction throttle valve closed and the air release valve opened instantaneously, stopping the compressor.

For example, when air having a temperature of 20 ° C. and a humidity of 85% is compressed to a one-stage compressor of 2 kgf / cm ² (g), cooled to 35 ° C. by an intercooler, and compressed to a predetermined pressure by a two-stage compressor, If the amount of intake air during loading is 8.0 g / m ³ , 13.6 g / min of drain is generated at the intercooler outlet. After that, even if the drain component is separated by the drain separator 8, the separation efficiency is not 100%, so the drain flows into the two-stage compressor. On the other hand, during unloading, a small amount of air is sucked in, and the pressure at the outlet of the first-stage compressor is about atmospheric pressure, so air that does not contain a drain is pumped to the second-stage compressor.

FIG. 2 is a control circuit diagram showing an embodiment of the present invention.
Shown in The auxiliary relay 17 and the time delay relay 18 are connected in parallel, the contact 19 ′ of the Δ magnetic contactor 19 is provided above the auxiliary relay 17, and the switch 20 is provided above the contact. During Δ operation (when the Δ electromagnetic contactor 19 is energized), the switch 20 is closed to interrupt the energization of the coil 12 ′ of the three-way electromagnetic valve (1) 12 and the coil 13 ′ of the three-way electromagnetic valve (2) 13. like,
Contact 1 of the auxiliary relay 17 above the coil of the three-way solenoid valve
7 ′ and via the contact 19 ″ of the Δ electromagnetic contactor 19 to the upper side so that the coil of the three-way electromagnetic valve is energized only during Δ operation, and the Δ electromagnetic contactor 19 is set at the set time of the time delay relay 18
A circuit for stopping the compressor after a set time is provided above the contact 18 'of the time-relay 18 so as to cut off the energization of the compressor. A circuit for detecting the pressure with the pressure switch and turning on and off the energization of the coil of the three-way solenoid valve is omitted here.
By providing this circuit, when the switch 20 is pressed,
The compressor is stopped by unloading for the set time of the time delay relay.

A second embodiment of the present invention will be described.

In addition to the usual stopping method, the stopping method of the first embodiment is provided.

[0015]

According to the present invention, in the two-stage oil-free type oil-free compressor, the compressor is stopped while the compressed air containing no drain is being sent to the two-stage compressor, and Since the drain does not remain on the stage compressor and other devices, it is possible to avoid rusting of the rotor in the two-stage compressor and the inside of the casing due to the drain. This is an effective means especially when the compressor is not operated for a long period of time.

[Brief description of drawings]

FIG. 1 is a system diagram of capacity control of a two-stage oilless screw compressor according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of an embodiment of the present invention.

[Explanation of symbols]

1 ... One-stage compressor, 2 ... Two-stage compressor, 3 ... Intercooler, 4 ... High precooler, 5 ... Aftercooler, 6 ... Suction throttle valve, 7 ... Exhaust valve, 8 ... Drain separator, 9 ... Check valve 10 ... Pressure switch, 11 ... Control piping filter,
12, 13, 14, 15, 16 ... Three-way solenoid valve, 12 ',
13 '... A coil of a three-way solenoid valve.

Front page continuation (72) Inventor Yoshiro Nagata 390 Muramatsu, Shimizu City, Shizuoka Prefecture, Hitachi, Ltd.

Claims (1)

[Claims] 1. A structure in which a gas compressed by a one-stage compressor is cooled by a cooler and further compressed by a two-stage compressor, and a valve at an inlet port is opened and closed and a gas in a discharge pipe is discharged. In a two-stage oilless screw compressor that repeats loading and unloading operations by interlocking with opening and closing of a valve, it has a function of forcibly stopping after a certain time as a means for stopping the compressor. A two-stage oil-free screw compressor.