Analysis of Pneumatic Control Principle of Single Screw Mobile Air Compressor for Coal Mine

The single-screw mobile air compressor for coal mine is a mine gas supply equipment developed according to the underground coal mine environment. It is used as a power source for underground tunneling and anchoring and spraying. It has stable operation, low sound and high reliability. Long life and low maintenance costs. Safety is the most important equipment used in underground coal mines. The safety protection measures shall be complete and considerate. The selected electrical appliances shall have an explosion-proof certificate and a safety mark certificate for coal mine products, which shall comply with the “Safety Regulations for Coal Mines” and “Safety Technical Inspection Specifications for Air Compressors under the Mines” > MT678-2009 Medium mine mobile air compressor>>etc.

2 Safety requirements The difference between single-screw air compressors for coal mines and general single-screw air compressors for civil use is reflected in the following aspects.

(1) In the selection of parts, parts that can be impacted externally or under maintenance and operation conditions should generally not be made of light alloy. When necessary, the light alloy material shall be in accordance with the provisions of GB 3836.1-2010, and the inspection shall be carried out by the designated inspection agency of the state. The tensile strength shall not be less than 120 MPa, and the light shall be qualified according to the friction spark test method specified in GB/T13813-2008. Made of alloy; or by mass percentage, the total content of aluminum, chin and magnesium is not allowed to be greater than 15%, and the total content of chin and magnesium is not more than 6%. It is also possible to take protective measures for light alloy parts so that they are not directly subjected to Impact. If non-metallic materials are used, they shall be flame retardant and antistatic, and have passed the inspection by the national designated inspection authority.

(2) The gas or liquid used in the indicator thermometer shall be non-toxic and non-combustible and explosive.

Automatic protection devices such as (or flow) should have a signal display, and the electrical part should be intrinsically safe.

The requirements of 3836.2-2010 and GB3836.4-2010 shall be "Explosion-proof certificate" and the safety mark certificate for coal mine products. A series of requirements, designed to ensure the safety of coal mines, the technology of the control system, the comparison of the control system, the control system of the single-screw air compressor, and the control part of the fuel injection single screw air compressor. The star triangle starts, the method of solenoid valve control. The control principle is as follows (the intake valve is an unloading valve and the air-cooled type is taken as an example).

(1) Before the start-up, the unloading valve is fully closed, the bleed valve is opened, and the solenoid valve is closed. Press the “Start” button to start the main motor. A small amount of air is drawn in from the intake check valve built into the unloading valve to establish the pressure required for lubrication to ensure the supply of lubricant for the compression chamber and bearings.

(2) Loading control After the cutting and loading operation, the control solenoid valve is energized to open, and the control signal of the bleed valve is closed. At this time, the pressure of the oil and gas tank is gradually increased, the unloading valve is gradually opened, and the unloading valve is fully increased with the pressure. When the compressor starts to run at full load, when the pressure rises to 0.45 MPa, the minimum pressure valve is fully open and the air is output.

(3) Unloading When the exhaust pressure reaches the unloading pressure setting value, the pressure switch signal is sent to the microcomputer controller for processing, the control solenoid valve is closed, the bleed valve is opened after the control signal is lost, and the unloading valve is closed. At this time, when the compressor is running at no load and the pressure of the pipeline system drops to the set value of the loading pressure, the microcomputer controller sends a signal to open the control solenoid valve, the control valve is closed, the unloading valve is fully opened, and the compressor is re-opened. Load run.

The venting valve control signal is turned on, and the electric cutting is stopped after 15s. 3.2 Coal mine fuel injection single screw air compressor control system Coal mine single screw air compressor control system Considering safety, the use of pneumatic valve control, explosion-proof and intrinsically safe magnetic starter direct start mode control principle For example, if the intake valve is a poppet valve, the working process of the single-screw air compressor for coal mine (taking the intake valve as the poppet valve and the rated pressure as 0.8MPa as an example), the poppet valve is closed, and the manual valve is 14-way. The state of the trace air enters the main engine through the intake port of the poppet valve through the throttle valve and the check valve. Then, the compressed small amount of gas is divided into two ways, one way to open the exhaust check valve to enter the oil separator to separate; the other to the oil shutoff valve, open it, and start to supply the gas for the main engine to be separated by the oil separator. Manually rotating the valve, one part of the valve to the intake valve against the valve stem of the intake valve, so that it is closed; the other part controls the vent valve. The vent valve is a normally closed two-way two-way valve, so when there is a gas source signal, the vent valve opens. Therefore, the gas in the system passes through the vent valve and enters the air filter to vent.

In this process, the minimum pressure valve is in the closed state. At this time, the compressor is vented while being compressed, and is in a light load start mode.

43 through, so that the air source for controlling the valve stem of the intake valve is discharged through the venting port of the manual rotary valve, and the intake valve is fully opened due to the pressure difference between the internal and external valves. The pressure signal for controlling the opening and closing of the vent valve disappears, the vent valve is closed, the venting is no longer emptied, and the compressor enters the full loading mode. When the system pressure exceeds 3.5 bar, the minimum pressure valve opens, the compressed air enters the gas supply pipe from now on, and the line pressure is controlled by the pressure switch.

(3) Unloading If the required air volume is lower than the rated exhaust volume, the exhaust pressure rises. When the supply line pressure exceeds 8.2 bar set by the pressure switch, the pressure switch opens, the intake valve is closed, and the vent valve is opened. The system enters the uninstall state.

When the pressure drops below 8.2 bar, the pressure switch is closed, the intake valve is opened, the vent valve is closed, and the system is loaded again. This cycle works.

Control technology air filter (4) stop turning the manual valve to the unloading state, the compressor is unloaded for 15s left stone, press the “stop” button to stop.

3.3 The two air compressors used in underground coal mines use pneumatic valves to control the system to load and unload. This is because if the solenoid valve is used to control the system to be loaded and unloaded, the explosion-proof solenoid valve must be used to prevent the solenoid valve. There are defects of large size and high price, and there are always security risks. Changing to pneumatic valve control avoids these problems and makes the control process safe and reliable. At the same time, the control button and emergency stop button used in the air compressor for coal mine must be mine explosion-proof to prevent the generation of electric spark. In addition to the safety valve between the separation core of the oil separator and the minimum pressure valve, the oil separator is installed. A safety valve is added between the coarse split cylinder and the cylinder to prevent the oil separator from clogging, and the pressure rises and an explosion occurs. In addition, the single-screw air compressor generally only has a temperature sensor at the exhaust port of the main engine, and the single-screw air compressor for coal mine has a temperature switch on the exhaust port of the main engine, and is added to the cylinder of the oil separator. An explosion-proof temperature switch is installed to ensure safe and reliable temperature control.

4 The product parts management materials are all controlled. The main zero (yuan) parts and important raw materials are divided into 4 categories, namely safety related parts (class A), safety standard parts (class B), and safety standard parts (class C). And in addition to the above Table 1 coal mine underground air compressor sequence parts (material) name specification model (material) safety standard number (or other certification number) validity period controlled category starter motor cable connection link box button connection pin association Equipment (temperature, oil pressure, level sensor) Pressure vessel Non-metallic parts Light alloy parts other major zero (yuan) parts (Class D).

Among them, when it is necessary to change the safety related components (Class A) and the safety standard components (C class), the application for change should be submitted to the Biaoyuan National Center, and the change procedure can only be changed.

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