All basic knowledge of screw air compressor The full name of the air compressor is an air compressor; a machine designed according to the working principle of the rotation of the twin screw (also called Yin and Yang rotor) to change the volume of the gas, it can suck in natural air and then complete the work through several internal processes. To discharge compressed air that meets pressure requirements, this machine is called a screw air compressor.The core problem of compressor oper
Basic knowledge of screw air compressor 1. Working pressure of air compressor There are many forms of pressure units. Here we mainly introduce the pressure units commonly used in screw air compressors; ①Working pressure, domestic users often call exhaust pressure. Working pressure refers to the highest pressure of air discharged from the air compressor; ②The commonly used working pressure unit is: bar or Mpa, 1bar=0.1Mpa ③Generally, users usually call the pressure unit: Kg (kg), 1bar=1Kg 2. Volume flow of air compressor ① Volumetric flow, domestic users often call the displacement. The volumetric flow rate refers to the volume of the gas discharged by the air compressor per unit time at the required exhaust pressure, converted to the intake state. ② The volume flow unit is: m³/min (cubic/minute) or L/min (liter/minute), 1m³ (cubic) = 1000L (liter); ③General, the commonly used flow unit is: m³/min (cubic/minute); ④ Volumetric flow is also called exhaust volume or nameplate flow in my country. 3. Power of air compressor ①Generally, the power of the air compressor refers to the matching nameplate power of the driving motor or diesel engine; The unit of power is: KW (kw) or HP (hp/horsepower), 1KW≈1.333HP. 4. Selection guide for air compressor Selection of working pressure (discharge pressure): When the user prepares to buy an air compressor, first determine the working pressure required at the gas end, add a margin of 1-2 bar, and then select the pressure of the air compressor, (the margin is considered to be installed from the air compressor (The pressure loss of the distance from the location to the actual gas-end pipeline should be appropriately considered according to the distance between 1-2bar). Of course, the size of the pipeline diameter and the number of turning points are also factors that affect the pressure loss. The larger the pipeline diameter and the fewer turning points, the smaller the pressure loss; otherwise, the greater the pressure loss. Therefore, when the distance between the air compressor and the gas end pipelines is too far, the diameter of the main pipeline should be appropriately enlarged. If the environmental conditions meet the installation requirements of the air compressor and the working conditions permit, it can be installed near the gas end. Selection of volume flow; When selecting the volume flow rate of the air compressor, you should first understand the volume flow rate of all gas-consuming equipment, multiply the total flow rate by one, and maintain the items. In addition to the three-level maintenance items, you also need: 1. Check the street contact and insulation resistance of the electrical part of the screw air compressor; 2. Replace the motor grease (replace every 8000 hours of operation), if there are parameters in the equipment manual, the manual shall prevail; 3. Cleaning the load-reducing valve (intake valve); 4. Clean the minimum pressure valve (pressure maintenance valve); 5. Cleaning oil return check valve: 6 Cleaning the temperature control valve; 7. Clean the cooler; 8. Cleaning the water separator; 9. Correct all parameters. Note: The above maintenance should be carried out after the equipment has been confirmed that there is no electricity and no pressure.
2. Operation method: 1. Check the street contact and insulation resistance of the electrical part of the screw air compressor; The electrical part of the air compressor is divided into a main circuit, a control circuit and a signal transmission (temperature, pressure sensor) circuit. Due to the vibration generated during the operation of the air compressor, some of the wires will loosen after a long time. The looseness of the wires will cause the unit to fail to start, and will cause serious disasters such as the failure of the protection function, arc short circuit and electric shock. Therefore, the electrical part should be checked regularly. During the inspection, you can swing the wires one by one by hand, feel the tightness of the thread, and the loose thread should be tightened; In addition, the insulation of the motor, equipment and ground needs to be tested with a shaker. The insulation resistance should be controlled above 500 megohms, otherwise it should be dried or repaired. 2. Replace the motor grease; The front and back ends of the motor are installed to ensure life and proper operation under proper lubrication. Therefore, grease should be injected regularly, and the type of grease should be selected according to the parameters provided by each manufacturer. 3. Cleaning and reducing valve of screw air compressor (also called intake valve): (1) Composition of load-reducing valve: The load-reducing valve is composed of valve body, spool (piston), manifold block, solenoid valve and proportional valve (capacity regulating valve). (2) The function of the load-reducing valve: the load-reducing valve mainly controls the loading (screw air compressor heavy vehicle), unloading (empty vehicle), and proportional (capacity adjustment) control functions of the air compressor, and can also prevent lubrication when the air compressor is stopped. Oil sprayed from the host (3) Disassembly of the load-reducing valve: 1. Remove the hose connecting the load-reducing valve and the air filter; 2. Remove all other components and the air pipe connected to the load-relief valve; 3. Remove the solenoid valve coil; 4. Remove and remove the nuts assembled with the load-relief valve and the host; 5. Move the load relief valve to the ground covered with clean paper or related clean paving. (4) Cleaning the load-reducing valve: (Screw air compressor cleaning agent should use soapy water, diesel, clean gasoline, Tianna water, etc., the above cleaning agent should be selected according to the degree of dirt, it is generally recommended to use soapy water or diesel for cleaning) Dismantle the solenoid valve: remove the solenoid valve and check whether the O-ring and sealing piece in the solenoid valve need to be replaced (reminder: if you are not familiar with the intake valve, please also remove the position of the component to avoid errors when reinstalling), If there is no need to replace, put the disassembled screws, O-rings, sealing pieces, solenoid rods, cores and other components into the container prepared in advance, and put them in a suitable cleaning agent to soak (Note: When using gasoline and Tianna water for cleaning Please do not soak the O-ring and other rubber products for too long to avoid corrosion); Dismantle the proportional valve: remove the proportional valve from the valve body, and then unscrew the adjusting nut (it is best to make a mark on the curtain before screwing to avoid too large deviation of the proportional value when reinstalling), take out the valve core and O-ring , U-rings, springs and check whether O, U-rings need to be replaced (all sealing rings and springs removed by the screw air compressor must be subject to this inspection, which will not be repeated in the following description). The lower components are put in cleaning agent and soaked. Dismantling the manifold block: remove the manifold block from the valve body, there are air holes in the four measurement of the manifold block (the hole of the screw air compressor is used to unclog the gambling plug in the integrated air circuit), and the air hole Unscrew the sealing nut and soak the integrated block in the cleaning agent. Disassembly of the load-reducing valve spool: Use the circlip pliers to remove the circlip located at the link between the spool and the valve body, then use the pipe wrench to unscrew the spool, take out the cylinder, valve plate, O-ring, U-ring, Put the spring into the cleaning agent and soak it, then remove the air inlet on the valve body and put the whole valve body into the soak. At this time, the disassembly process of the load-reducing valve has been completed. Cleaning: If the intake valve has serious dirt, it should be replaced with a new cleaning agent. During the cleaning process, the cleaned parts should be washed first and then the parts with more dirt should be washed. The cleaned parts should be washed again with clean water to avoid Corrosion shortens the service life of parts. The parts cleaned by washing should be put in a clean place to dry to avoid rusting of iron parts. When cleaning the valve plate and the place where the valve body and the valve plate are in contact, pay attention to the flatness of the surface, and clean it, and replace it if necessary, otherwise it will cause the air compressor to start under load (the screw air compressor large unit starts under load) It will cause the phenomenon of unable to start). Installation of components: The installation of components is carried out in the reverse step of disassembly. It should be mentioned that when installing components, the location of the sealing ring and the moving component should be coated with an appropriate amount of engine oil, so that the sealing ring can be better installed and the moving parts can be replaced. flexible. Note: Due to the many parts of the load relief valve, if you are not sure about the location of each part, you can disassemble and clean each part before installing the part, but do not install the part on the valve body, wait for all parts to be cleaned Assemble to the valve body together again. After the entire cleaning process of the load-reducing valve is completed, it is put aside to be loaded into the air compressor.
4. Clean the minimum pressure valve (screw air compressor is also called pressure maintenance valve): (1) Composition of minimum pressure valve: The minimum pressure valve is composed of valve body, valve core, adjusting nut, spring, sealing element, etc. (2) The function of the minimum pressure valve: The minimum pressure valve mainly plays the role of establishing the internal pressure of the unit, promoting the circulation of lubricating oil, and meeting the working pressure of the load relief valve. In addition, the minimum pressure valve acts as a check valve to prevent the unit from being unloaded again During operation, the compressed air in the air storage tank flows back to the air compressor. (3) Disassembly of the minimum pressure valve: The structure of the minimum pressure valve is very simple. Unscrew the nut of the screw air compressor between the valve core and the valve body to take out the components inside. The minimum pressure valve core of the small unit is built into the valve The body can be removed by disassembling the valve body cover. (4) Clean the minimum pressure valve: clean the minimum pressure valve according to the method of cleaning the load reducing valve. (5) The assembly of the minimum pressure valve: the components are assembled in the reverse step of disassembly. Since the structure of the minimum pressure valve is very simple, the assembly process will not be described one by one, but it needs to be paid attention to. The direction of the ring. (6) The minimum pressure valve of the screw air compressor is put aside to be loaded into the air compressor after the entire cleaning process is completed. 5. Cleaning the oil return check valve (1) Composition of one-way valve: The one-way valve is composed of valve body, steel ball, steel ball seat, spring and other components. (2) The function of the oil return check valve: the oil and gas mixture compressed by the main machine is initially separated by centrifugal force in the oil and gas tank. Because the weight of oil is greater than air, most of the oil in the solid-air mixture is dropped to the oil tank by centrifugal force, and the screw air compressor is returned to the host under the action of internal pressure for a lubrication cycle process, and the compression containing a small amount of oil The air is separated again by the oil and gas separator. At this time, the lubricating oil separated by the oil and gas separator will fall to the bottom of the oil and gas separator. In order to prevent this part of oil from being taken away with the compressed air, the unit is inserted into the oil and gas separation by an oil pipe during design At the bottom of the compressor, this part of the oil is directly introduced into the main engine for lubrication by the action of internal pressure, and there is a check valve on the oil pipe. The screw air compressor is called the oil return check valve. Its function is to smooth the oil of the oil and gas separator. Recovered to the host without letting the oil of the host flow upside down to the oil and gas separator. (3) Disassembly of the oil return check valve: There is a joint at the valve body, unscrew from this place, and take out the spring, steel ball and steel ball seat. (4) Cleaning the oil return check valve: use a cleaning agent to clean the valve body, spring, steel ball, and steel ball seat. Some of the check valves also have a filter screen, and if they are cleaned together. (5) Assembly of oil return check valve: install the check valve according to the reverse steps of disassembly. (6) After the whole cleaning process of the one-way valve is completed, put it aside to be loaded into the air compressor. 6. Cleaning temperature control valve of screw air compressor (1) The composition of the temperature control valve: the temperature control valve is composed of the valve body, the valve core, the temperature sensing element, the spring, etc. (2) The role of the temperature control valve: the temperature control valve plays a role of constant temperature control. When the oil temperature measured by the temperature sensing element of the temperature control valve is lower than the operating value (the operating value of the temperature sensing element is generally degrees), the lubricating oil directly from The oil and gas barrel returns to the host machine. When the oil temperature measured by the temperature control valve temperature sensing element is higher than the action value, the temperature control valve temperature sensing element thimble moves, pushing the valve core to open the bypass valve equipped by itself, so that the lubricating oil enters the cooler Cooling (If the temperature measured by the temperature sensing element is higher, the bypass valve is opened more), the cooled lubricating oil is returned to the host. (3) Disassembly of the temperature control valve: the side of the temperature control valve of the screw air compressor is covered by one side, there are screw holes on the side cover, find a suitable nut to screw into the side cover, and then use the circlip pliers to take out the fixed side cover Snap the spring, and then pull the nut just screwed in with the pliers to remove the side cover and all the components inside. (4) Cleaning the temperature control valve: cleaning all components of the temperature control valve according to the method of cleaning the load reducing valve. (5) Assembly of temperature control valve: install the temperature control valve in the reverse step of disassembly. (6) After the entire cleaning process of the screw air compressor temperature control valve is completed, put it aside to be loaded into the air compressor. 7. Cleaning the cooler (1) There are two types of coolers: air-cooled and water-cooled. (2) Cleaning of the cooler; Air-cooled cooler Open the air hood to clean the cover, or remove the cooling fan. Blow the dirt back with compressed air, and then take the dirt out of the air hood; if it is dirty, spray some degreaser before blowing. When the screw air compressor cannot be cleaned by the above method, the cooler needs to be removed, soaked or sprayed with cleaning fluid and cleaned with the help of a brush (wire brush is strictly prohibited). Install the cover or cooling fan Water-cooled cooler Disassemble the cooling water inlet and outlet pipes. Inject cleaning solution to immerse or circulate flushing with pump (backwashing effect is better). Rinse with clean water. Install the cooling water inlet and outlet pipes. When the scale of the oil cooler is serious and the cleaning by the above method is not ideal, you can remove the oil cooler separately, open the two end covers, and use a special cleaning brush or other tools to remove the scale. When cleaning the media side of the cooler cannot effectively reduce the temperature, the screw air compressor needs to clean the oil side, as follows: Disassemble the inlet and outlet pipes. Inject cleaning solution to immerse or circulate flushing with pump (backwashing effect is better). Rinse with clean water. Blow dry with dry air or remove water with dehydrated oil. Install the inlet and outlet tubing 8. Cleaning the water separator The structure of the water separator of the screw air compressor is similar to that of an oil and gas tank. The air inlet is designed against the wall and solidified into a centrifugal force. Due to the weight of water and air, it can effectively separate the water in the compressed air. Cleaning of water-gas separator: Remove the cover of water-gas separator, soak and clean with cleaning agent. 9. Correct all parameters After all the above components are cleaned and dried, they are installed in the air compressor. After installing all the components in the air compressor, check again for omissions and clean the tools and other items used during installation. The operating parameters of the air compressor can be adjusted according to the following data: () Preparation before the screw air compressor is turned on: () Belt (coupling) correction: If the air compressor is driven by a belt, the tightness of the belt should be between 10 and 20 mm. If the air pressure is driven by the coupling, after installation, you should manually crank the motor and the host and check the balance of the coupling when it rotates. The coupling of screw air compressor basically adopts elastic coupling, which can be ignored when the deviation of solid balance is not large. (1) Steering correction of the screw air compressor host: if the main power supply is removed during the re-maintenance process, pay attention to the positive and negative rotation of the motor after the power supply is connected back. The steering of the motor should be based on the steering of the host. The turn icon on the main unit. Correction method: exchange any two power lines in three-phase electricity. (2) Positive effect of loading, unloading and proportional value: When setting these three parameters, the unloading value should be determined first. The unloading value should be determined according to the rated pressure of the air compressor and the pressure required by the gas end to determine the unloading value After setting the loading value, the pressure difference between the two should be between 0.1 and 0.2Mpa. After setting the unloading and loading values, finally set the proportional value. The proportional value should be set between the unloading value and the loading value. The screw is empty Examples of compressors: If a factory needs an air compressor with a supply pressure of 0.8Mpa and the gas supply requirements are relatively stable, three parameters should be set as follows: unloading pressure setting 0.8Mpa, loading pressure setting 0.65Mpa, proportional control The pressure is set between 0.73~0.75Mpa. Positive method of screw air compressor: Set this parameter in the microcomputer controller (if the control of the air compressor is controlled by a button, the loading and unloading parameters should be adjusted from the pressure switch, and the proportional value should be on the proportional valve on the load relief valve. Adjust the value at the adjusting nut). (3) Unit internal pressure correction: the unit internal pressure should be between 0.2~0.45Mpa. Correction method: The pressure value should be carried out when the unit is unloaded and the value is adjusted on the adjustment nut of the minimum pressure valve. In order to facilitate reading the adjusted value, the pressure monitoring point should be taken before the minimum pressure valve and the pressure should be installed. Table (some microcomputer controllers have the function of displaying internal pressure parameters, if there is no such function, a pressure gauge should be installed before the minimum pressure valve). (4) The high temperature protection value is positive: when the screw air compressor is working normally, its temperature should be between 65~98℃. The temperature of automatic shutdown for over-temperature protection shall not exceed 105℃ Correction method: Adjust the high temperature automatic shutdown temperature value in the controller. Take 1.2 (that is, enlarge the 20% margin); New projects can be selected based on the flow value provided by the design institute; Consult the gas equipment supplier to understand the volume flow parameters of the gas equipment for selection; Air compressor station transformation can be selected with reference to the original parameter value and actual gas consumption; Appropriate selection is beneficial to the user and the air compressor equipment. Too much selection and waste, and too small selection may cause the air compressor to be in a long-term loading state or insufficient gas or pressure can not hit the disadvantages. The relationship between power, working pressure and volume flow In the case of constant power, when the speed changes, the volume flow and working pressure also change accordingly; for example: a 22KW air compressor, the working pressure is determined to be 7bar during manufacturing, calculated according to the technical curve of the compressor host Speed, exhaust volume is 3.8m³/min; When it is determined that the working pressure is 8 bar, the speed must be reduced (otherwise the drive motor will be overloaded). At this time, the exhaust volume is 3.6m³/min; because the speed is reduced, the exhaust is reduced accordingly, and so on. The selection of power is that the power supply capacity can meet the power of the matched drive motor under the conditions of working pressure and volume flow. Therefore, the steps to select an air compressor are: first determine the working pressure, then determine the corresponding volume flow, and finally the power supply capacity.
