JPH0979160A - Two-stage type dry screw compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent usual time blowoff of air compressed up to intermediate stage pressure at full load operation time by closing a primary side passage part of intermediate stage drain piping, introducing positive pressure air to the secondary side of the drain piping, and arranging a drain trap in the intermediate stage drain piping. SOLUTION: A three-way solenoid valve 13 is installed in drain piping of an intercooler 6, and an intermediate stage drain trap 14 is installed. At full load operation time, the three-way solenoid valve 13 opens between A and B, and intermediate stage drain piping is put in a condition where drain is sent into the intermediate stage drain trap 14 since the primary side 17 and the secondary side 18 lead to each other. At no-load operation time, the three- way solenoid valve 13 is switched by receiving detection by a pressure switch 11, and a part between C and B is opened, and though the primary side 17 of the intermediate stage drain piping is put under negative pressure, blowoff air cooled by a blowoff cooler 16 is sent into the secondary side 18 of the intermediate stage drain piping by piping 19, and the intermediate stage drain trap 14 can be kept in a positive pressure condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drain discharge method for a two-stage dry screw compressor.

[0002]

2. Description of the Related Art In a two-stage dry screw compressor, in order to reduce the power during no-load operation to about 20% of the power during full-load operation, the suction throttle valve is closed and the air in the system inside the compressor is released into the atmosphere. It uses a capacity control system that opens to

The conventional two-stage dry screw compressor cannot use a drain trap because the pressure of the intermediate stage becomes a negative pressure during no-load operation, and the drain discharge of the intermediate stage is always discharged in a slightly open state. However, there is a drawback in that the compressed air up to the intermediate stage pressure must be constantly discharged as the drain is discharged.

As a solution to this drawback, Japanese Patent Laid-Open No. 60-1877.
Although it is described in Japanese Patent No. 88, it has a problem that high temperature air at the outlet of the main body of the two-stage compressor must be used.

[0005]

An object of the present invention is to close the primary side passage portion of the intermediate stage drain pipe at the time of no load operation and at the same time to introduce positive pressure air to the secondary side of the intermediate stage drain pipe. The purpose is to enable the installation of a drain trap in the intermediate stage drain pipe and prevent the constant discharge of air compressed to the intermediate stage pressure during full load operation.

[0006]

According to the present invention, the three-way solenoid valve is switched during no-load operation, the primary side passage of the intermediate stage drain pipe is closed, and the cooled system air is released to the atmosphere. By guiding the drain pipe to the secondary passage side, the intermediate-stage drain pipe section can be brought to a positive pressure state not only during full load operation but also during no load operation.

[0007]

[Operation] When the intermediate-stage drain pipe section has a negative pressure during no-load operation, the drain portion that is not discharged is sucked into the compressor body, so that a drain trap having a drain reservoir cannot be installed. There was a problem.

By installing the three-way solenoid valve, the intermediate stage drain piping section can always be maintained in a positive pressure state, and the drain trap can be installed in the intermediate stage drain piping section.

When the drain trap is not installed,
There was a problem that the air compressed to the intermediate stage pressure was constantly discharged during full load operation.

By installing the drain trap, it is possible to prevent constant discharge of compressed air during full load operation.

Since the positive pressure air used during no-load operation is the air in the system of the compressor which is open to the atmosphere during no-load operation, there is no restriction in releasing it.

[0012]

An embodiment of the present invention will be described below with reference to FIG.

The rotation of the electric motor 1 causes the first-stage compressor 2 and the second-stage compressor 3 to rotate to perform compression work. The suction air passes through the suction filter 4, and then the suction throttle valve 5,
It enters the first stage compressor 2 and is compressed to the intermediate stage pressure. After that, it enters the intercooler 6, is cooled, passes through the intermediate-stage drain separator 7, and is compressed to the discharge pressure by the two-stage compressor 3. The discharge pressure air enters the aftercooler 9 through the check valve 8 to be cooled, passes through the discharge stage drain separator 10 and is supplied as service air.

A pressure switch 11 is attached to the secondary side of the aftercooler 9, and when the demand amount of service air decreases, the pressure switch 11 detects it and closes the suction throttle valve 5 to close the air release valve 12. It is a capacity control system that discharges air in the system of the compressor, which is the primary side of the open check valve 8, to the atmosphere to perform no-load operation.

A three-way solenoid valve 13 and an intermediate stage drain trap 14 are attached to the drain pipe of the intercooler. A discharge stage drain trap 15 is attached to the drain pipe of the aftercooler, and a blower cooler 16 is attached to the primary side of the air release valve 12.

Next, the operation of this embodiment will be described.

During full load operation, the three-way solenoid valve 13 is A-
Between B is open, the primary side 17 and the secondary side 18 of the intermediate stage drain pipe communicate with each other, and the drain is sent to the intermediate stage drain trap 14.

During no-load operation, the three-way solenoid valve 13 is switched in response to detection by the pressure switch 11 to open between C and B, and the primary side 17 of the intermediate-stage drain pipe has a negative pressure, but a blow-off cooler. The discharge air cooled by 16 is pipe 1
By means of 9, the intermediate drain pipe 14 can be fed to the secondary side 18 of the intermediate drain pipe to keep the intermediate drain trap 14 in a positive pressure state.

By using the intermediate-stage drain discharge method of the present invention, a small amount of air is discharged only when the drain accumulated in the drain trap is discharged, without constantly discharging the air compressed to the intermediate-stage pressure. Can be done.

[0020]

According to the present invention, the drain trap can be attached to the intermediate stage drain pipe, and the drain of the intermediate stage can be smoothly discharged without constantly releasing the air compressed to the intermediate stage pressure. It was

[Brief description of drawings]

FIG. 1 is a diagram of a compressed air system and a drain discharge system in a two-stage dry screw compressor according to an embodiment of the present invention.

[Explanation of symbols]

6 ... Intercooler, 11 ... Pressure switch, 12 ... Exhaust valve, 13 ... Three-way solenoid valve, 14 ... Intermediate stage drain trap,
16 ... Blow-off cooler.

Claims (1)

[Claims] 1. An intermediate stage drain is closed by closing a primary side passage part of the intermediate stage drain pipe and guiding positive pressure air to a secondary side of the drain pipe during operation of the capacity control device in which the intermediate stage pressure becomes a negative pressure state. A two-stage dry screw compressor characterized by installing a drain trap in the pipe to prevent the constant release of compressed air.