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All the basic knowledge of screw air compressor

Author: ComeFrom: Date:2020/10/27 9:50:21 Hits:232
  The full name of an air compressor is an air compressor; a machine designed according to the working principle of a twin screw (also known as a yin and yang rotor) rotating to make the volume change of the gas. It can suck natural air in and go through several internal processes to complete the work. Discharge compressed air that meets the pressure requirements. This machine is called a screw air compressor.
   One, basic knowledge of screw air compressor
   1. The working pressure of the air compressor
   There are many ways of expressing pressure units. Here we mainly introduce the commonly used pressure units of screw air compressors;
  ① Working pressure, domestic users often call exhaust pressure. Working pressure refers to the higher pressure of the exhaust gas from the air compressor;
  ② The commonly used working pressure unit is: bar or Mpa, 1 bar = 0.1 Mpa;
  ③ Generally, users usually call the pressure unit: Kg (kg), 1 bar = 1 Kg.
  2, the volume flow of the air compressor
  ① Volume flow, domestic users often call exhaust. Volume flow refers to the volume of gas discharged by the air compressor per unit time under the required exhaust pressure, converted to the amount of intake state.
  ② The volumetric flow unit is: m³/min (cubic/minute) or L/min (liter/minute), 1m³ (cubic) = 1000L (liter);
  ③ Generally, the commonly used flow unit is: m³/min (cubic per minute);
  ④ Volume flow is also called displacement or nameplate flow in our country.
  3, the power of the air compressor
  ① Generally, the power of the air compressor refers to the power of the matching drive motor or the nameplate of the diesel engine;
  ② The unit of power is KW (kilowatt) or HP (hp/horsepower), 1KW ≈ 1.333HP.
  4. Selection guide for air compressor
   Selection of working pressure (exhaust pressure):
   When the user is preparing to purchase an air compressor, first determine the working pressure required by the air end, plus 1-2
  Bar margin, and then select the pressure of the air compressor, (the margin is to consider the pressure loss from the installation location of the air compressor to the actual gas end pipeline distance, according to the length of the distance between 1-2
  Bar, appropriately consider the pressure margin). 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; on the contrary, the greater the pressure loss.
   Therefore, when the distance between the air compressor and each gas end pipeline 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.
   Volume flow selection:
  When selecting the volumetric flow rate of an air compressor, you should first understand the volumetric flow rate of all air-consuming equipment, and multiply the total flow rate by one. Maintenance items. In addition to the three-level maintenance items, you also need:
   1. Check the joint 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 the equipment manual has parameters, the manual shall prevail;
  3. Clean the relief valve (intake valve);
  4. Clean the minimum pressure valve (pressure maintenance valve);
   5. Clean the oil return check valve;
   6. Clean the temperature control valve;
  7. Clean the cooler;
   8. Clean the water and gas separator;
   9. Correct all parameters.
  Note: The above maintenance should only be carried out after the equipment is confirmed to be without electricity and pressure.
   2. Operation method:
   1. Check the joint contact and insulation resistance of the electrical part of the screw air compressor:
   The electrical part of the air compressor is divided into the main circuit, the control circuit and the signal transmission (temperature, pressure sensor) circuit. Due to the vibration generated during operation of the air compressor, some wire joints will become loose after a long time. Loose wire joints may cause the unit to fail to start, and at worst, cause serious disasters such as protection function failure, arc short circuit, electric shock and so on. Therefore, the electrical part should be checked regularly.
   When checking, you can swing the wires one by one by hand, feel the tightness of the thread ends, and tighten the loose thread ends;
   In addition, a shaker should be used to test the insulation between the motor and the equipment and the ground. The insulation resistance should be controlled above 500 megohms, otherwise it should be dried or repaired.
   2. Replace the motor grease:
  The front and rear ends of the motor are installed, and the service life can be guaranteed under proper lubrication. Therefore, grease should be injected regularly. The type of grease should be selected according to the parameters provided by each manufacturer.
  3. Screw air compressor cleaning relief valve (also called intake valve):
   (1) Unloading valve composition: Unloading valve is composed of valve body, spool (piston), gas circuit manifold, solenoid valve and proportional valve (accommodating valve).
  (2) Unloading valve function: The unloading valve mainly controls the loading (screw air compressor heavy car), unloading (empty car), proportional (capacity adjustment) control function of the air compressor, and can also prevent the air compressor from lubricating when it stops. Oil sprayed from the host
  (3) Disassembly of the relief valve: 1 remove the hose connecting the relief valve and the air filter; 2 remove all other parts and the air pipe connected to the relief valve; 3 remove the solenoid valve coil; 4 remove the relief valve and assemble the host And remove the nut; 5 move the relief valve to the ground covered with clean paper or related clean paving.
   (4) Cleaning the relief valve: (screw air compressor cleaning agent should be soapy water, diesel, clean gasoline, thinner, etc. The above cleaning agents should be selected according to the degree of dirt, generally recommended to use soapy water or diesel for cleaning)
  Remove 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 write down the position of the removed component to avoid errors when reinstalling), If there is no need to replace, put the disassembled screws, O-rings, seals, electromagnetic rods, cores and other components into a pre-prepared container, and put in appropriate cleaning agent to soak (Note: Use gasoline and thinner for cleaning   Please do not soak rubber products such as O-rings for too long to avoid corrosion);
  Dismantle the proportional valve: remove the proportional valve from the valve body, then unscrew the adjusting nut (make a mark on the nut before screwing to avoid too large deviation of the proportional value when reinstalling), take out the valve core, O-ring, U-shaped And check whether the O and U-shaped rings need to be replaced (all the sealing rings and springs removed by the screw air compressor must be checked, which will not be repeated in the following description), and the removed components Soak in detergent.
Dismantle the manifold block of the gas circuit: remove the manifold block from the valve body, and there are air holes on the four sides of the manifold block (the hole of the screw air compressor is used to clear the air circuit when the integrated air circuit is blocked), and the air hole Unscrew the sealing nut and soak the integrated block in the cleaning agent.
  Dismantle the valve core of the relief valve: use a circlip pliers to remove the circlip at the connection between the spool and the valve body, and then use a pipe wrench to unscrew the spool, take out the cylinder, valve disc, O-ring, U-ring, and The spring is soaked in the cleaning agent, and then the air inlet on the valve body is removed, and the entire valve body is soaked. At this time, the disassembly process of the relief valve has been completed.
  Cleaning: If the dirt on the intake valve is serious, change a new cleaning agent when cleaning. During the cleaning process, wash the cleaner parts first and then wash the dirty parts. The cleaned parts should be rinsed again with water to avoid Corrosion shortens the service life of parts. Parts washed with clean water should be placed in a clean place to dry to avoid rusting of iron-containing parts.
  When cleaning the valve plate and the place where the valve body and the valve plate are in contact, pay attention to the smoothness of the surface, and it should be cleaned and replaced if necessary, otherwise it will cause the air compressor to start with load (the large screw air compressor unit starts with load Can not start phenomenon will occur).
  Install components: install the components according to the reverse steps of disassembly. It should be pointed out that when installing the components, the location of the sealing ring and the movable components should be coated with a proper amount of engine oil, so that the sealing ring can be installed better and the movable parts can be more flexible.
  Note: Due to the many parts of the relief valve, if you are not sure about the position of each part, you can remove each part and then install the part after cleaning, but do not install the part on the valve body first, wait for all parts to be cleaned Assemble to the valve body together.
   After the entire cleaning process of the relief valve is completed, put it aside to be loaded into the air compressor.
  4. Clean the minimum pressure valve (screw air compressor is also called pressure maintenance valve):
   (1) Minimum pressure valve composition: The minimum pressure valve consists of a valve body, a spool, an adjusting nut, a spring, and a sealing element.
  (2) The function of the minimum pressure valve: The minimum pressure valve is mainly used to establish the internal pressure of the unit, promote the circulation of lubricating oil, and meet the working pressure of the relief valve. In addition, the minimum pressure valve also functions as a check valve to prevent the unit from unloading. The compressed air in the air storage tank flows back to the air compressor during operation.
  (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 internal components. The minimum pressure valve spool of the small unit is built into the valve. Body, all the internal components can be taken out by disassembling the valve body cover.
   (4) Clean the minimum pressure valve: Clean the minimum pressure valve according to the method of cleaning the relief valve.
  (5) Assembly of minimum pressure valve: Assemble the components according to the reverse steps of disassembly. Since the structure of the minimum pressure valve is very simple, the assembly process will not be described one by one, but note that if there is a U-shaped ring inside, pay attention to U The direction of the ring.
   (6) The minimum pressure valve of the screw air compressor is put aside after the entire cleaning process is completed to be loaded into the air compressor.
   5. Clean the oil return check valve
  (1) The composition of the one-way valve: the one-way valve is composed of valve body, steel ball, steel ball seat, spring and other elements.
(2) The role of the oil return check valve: the oil and gas mixture compressed by the main engine is first separated by centrifugal force in the oil and gas tank. Because the weight of the oil is greater than air, most of the oil in the solid oil and gas mixture falls to the oil by centrifugal force. The tank and screw air compressor return to the main engine for a lubrication cycle under the action of internal pressure, and the compressed air containing a small amount of oil is separated again by the oil-air separator. At this time, the lubricating oil separated by the oil-air separator will fall off. To the bottom of the oil and gas separator, in order to prevent this part of the oil from being carried away with the compressed air, the unit is designed with an oil pipe inserted into the bottom of the oil and gas separator, and this part of the oil is directly introduced to the main engine for lubrication through internal pressure. There is a check valve on the oil pipe, and the screw air compressor is called the oil return single valve.
   Its function is to smoothly recover the oil from the oil and gas separator to the main engine without allowing the oil from the main engine to flow back to the oil and gas separator.
   (3) Disassembly of the oil return single valve: There is a connection point in the valve body, unscrew the spring, steel ball, and steel ball seat.
   (4) Cleaning the oil return check valve: clean the valve body, spring, steel ball, steel ball seat with cleaning agent, and some check valves have filters inside, and clean them together if any.
   (5) Assembly of oil return check valve: Install the check valve according to the reverse steps of disassembly.
  (6) After the entire cleaning process of the one-way valve is completed, put it aside to be loaded into the air compressor.
  6, screw air compressor cleaning temperature control valve
   (1) Composition of temperature control valve: The temperature control valve is composed of a valve body, a valve core, a temperature sensing element, a spring, etc.
  (2) The function of the temperature control valve: the temperature control valve plays the role of constant temperature control. When the oil temperature measured by the temperature sensing element of the temperature control valve is lower than the action value (the action value of the temperature sensing element is generally 71 degrees), the lubricating oil is directly When the oil temperature measured by the temperature sensing element of the temperature control valve is higher than the action value, the thimble of the temperature sensing element of the temperature control valve will act to push the valve core to open the bypass valve of its own equipment, and the lubricating oil will enter the cooling The device is cooled (the higher the temperature measured by the temperature sensing element, the greater the opening of the bypass valve), and the cooled lubricating oil returns to the host.
  (3) The disassembly of the temperature control valve: the screw air compressor has a cover on the surface of the temperature control valve, and the cover has screw holes. Find a suitable nut to screw in the cover, and then use circlip pliers to remove the fixed cover The circlip, and then use the pliers to pull the nut just screwed in to remove the cover and all the internal parts.
   (4) Cleaning the temperature control valve: Clean all parts of the temperature control valve according to the method of cleaning the relief valve.
   (5) Assembly of temperature control valve: Install the temperature control valve according to the reverse steps of disassembly.
   (6) After the entire cleaning process of the temperature control valve of the screw air compressor is completed, put it aside to be installed in the air compressor.
  7. Clean the cooler:
   (1) There are two types of coolers: air-cooled and water-cooled. 7.2 Cleaning of cooler:
   Air-cooled cooler
   Open the air duct to clean the cover, or remove the cooling fan.
   Use compressed air to blow the dirt down, and then take the dirt out of the air deflector; if it is dirty, spray some
   Blow on the degreaser. When the screw air compressor cannot be cleaned by the above methods, 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 soak or circulate flushing with a pump (recoil effect is better).
   Rinse with clean water.
   Install the cooling water inlet and outlet pipes.
   When the oil cooler is severely scaled and the above method is not ideal for cleaning, you can remove the oil cooler separately, open the two end covers, and use a special cleaning steel brush or other tools to remove the scale. When cleaning the medium side of the cooler cannot effectively reduce the temperature, the screw air compressor needs to clean the oil side. The method is as follows:
   Disassemble the inlet and outlet tubing.
  Inject cleaning solution to soak or circulate flushing with a pump (recoil effect is better).
   Rinse with clean water.
   Dry with dry air or use dehydrated oil to remove water.
   Install the inlet and outlet tubing
   8. Clean the water and gas separator
  The structure of the water-gas 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 the solid shape is centrifugal force. Due to the weight of water and gas, it can effectively separate the water in the compressed air.
  Cleaning of the water-gas separator: Open the cover of the water-gas separator, and then it can be cleaned by soaking with detergent.
   9. Correct all parameters
   After all the above components are cleaned and dried, they will be installed on the air compressor. After all components are installed on the air compressor, check again for omissions and clean up 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 starting the screw air compressor:
  Belt (coupling) correction: If the air compressor is driven by a belt, the belt tightness should be between 10 and 20 mm. If the air compressor is driven by a coupling, the motor should be turned by hand after installation. Host and check the balance of the coupling when it rotates. The couplings of screw air compressors basically use elastic couplings, which can be ignored when the deviation of solid balance is not large.
  (1) Screw air compressor main engine steering correction: If the main power supply has been removed during the maintenance process, pay attention to the forward and reverse rotation of the motor after the power supply is connected. The steering of the motor should be based on the steering of the main engine. For the correct steering of the main engine, please check the label The turn icon on the host.
   Calibration method: Exchange any two power lines in the three-phase power supply.
  (2) Loading, unloading, and proportional value validity: When setting these three parameters, the unloading value should be determined first, and the unloading value should be determined according to the combination of the rated pressure of the air compressor and the required pressure at the gas end to determine the unloading value Then, set 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. Compressor example: If a factory needs the air compressor supply pressure of 0.8Mpa, and the air supply requirement is 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 and 0.75Mpa.
  Screw air compressor calibration method: set this parameter in the microcomputer controller (if 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 in the proportional valve on the unloading valve. Adjust the value at the adjusting nut).
   (3) The internal pressure effect of the unit is positive: the internal pressure of the unit should be between 0.2~0.45Mpa.
  Correction method: The pressure value should be carried out when the unit is unloaded, and the value should be adjusted on the adjusting nut of the minimum pressure valve. In order to facilitate the reading of the adjusted value, the pressure detection point should be taken before the minimum pressure valve and the pressure should be installed. Gauge (some microcomputer controllers have internal pressure parameter display function, if there is no such function, a pressure gauge should be installed before the minimum pressure valve).
   (4) The high temperature protection value is valid: When the screw air compressor is working normally, its temperature should be between 65~98℃. The automatic shutdown temperature of 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 margin by 20%);
  The new project can be selected according to the flow value provided by the design institute;
   Learn about the volumetric flow parameters of the gas-consuming equipment from the gas-consuming equipment supplier for selection;
   Air compressor station reconstruction can refer to the original parameter values ​​and actual gas consumption for selection;
   Appropriate selection is beneficial to both the user and the air compressor equipment. Excessive selection is wasteful, and too small selection may cause the air compressor to be in a long-term loading state or insufficient air or pressure can not reach the disadvantages.
  The relationship between power, working pressure and volume flow
In the case of constant power, when the speed changes, the volumetric flow and working pressure also change accordingly; for example: a 22KW air compressor, the working pressure is determined to be 7bar at the time of manufacture, calculated according to the main compressor technical curve Speed, displacement is 3.8 m3/min;
   When it is determined that the working pressure is 8bar, the speed must be reduced (otherwise the drive motor will be overloaded). At this time, the exhaust volume is 3.6 m3/min; because the speed is reduced, the exhaust gas is also reduced, and so on.
  The selection of power is to meet the working pressure and volume flow conditions, and the power supply capacity can meet the power of the matched drive motor.
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copyright:LIXI REFRIGERATING EQUIPMENT(SUZHOU)CO.,LTD. Record No:Su ICP Bei no.11063255-1 Technical support: shidewei Technology