Equipment Management and Maintenance Production and Use of Compressed Air in Tire Factory (±) Wang Qiying Kong Linghai Zhang Xiujun Wang Hongxun Li Tao 2 (1 Shandong Taishan Tire Co., Ltd. Shandong Feicheng 271600; 2 Shandong Feicheng Gas Company Shandong flB City 271600) Selection and operation control; The process of using compressed air in the tire factory and the matters needing attention are introduced. Finally, the method of measuring the compressed air by the vortex flowmeter is introduced.
Advised on how to produce compressed air at the lowest cost, use and manage compressed air for optimal results, and measure compressed air in the most scientific way.
Compressed air is now the most common power medium and production medium used in tire production. It is widely used in the tire factory for the control and drive of pneumatic components, the transportation of carbon black and powder, the drying of raw materials and semi-finished products, the shaping of inner and outer tires, and the post-inflation cooling of tire vulcanization.
Compressed air has the characteristics of colorless and odorless. Due to the simple production process, universal use, and difficulty in finding after leakage, there are some problems that are easily overlooked during the production and use of compressed air. In order to improve the management level of the tire enterprises, in addition to reasonable production and use of compressed air, it is also necessary to do a measurement of compressed air. Therefore, it is particularly important to produce compressed air at the lowest cost in the tire plant, to use and manage compressed air with the best effect, and to measure compressed air in the most scientific way. This article is the author's experience in equipment and power management for many years in the tire factory. It introduces and discusses the problems in the production, use and measurement of compressed air for peers.
1967-), male, senior engineer, graduated from Qingdao Institute of Chemical Technology in 1989, majoring in rubber machinery, mainly engaged in the design and management of rubber machinery and the organization and management of tire production. He has published 20 papers.
1 Compressed air production The production process of compressed air mainly includes air filtration, compression, cooling and removal of oil and moisture, storage and transportation.
The main component of the L1 compressed air system The compressed air system consists of two main components, the compressed air production and delivery system and the compressed air consumption system.
Parts and main functions of the LL1 production and conveying system (1) Compressor. Atmospheric pressure air is compressed and delivered to the pneumatic system at a higher pressure to convert mechanical energy into pneumatic energy. ) Motor. Convert electrical energy into mechanical energy and supply it to the compressor. )Pressure Switch. The two pressure limits of the compressed air in the air tank are used to control the stopping and starting of the motor. Adjust the maximum pressure. When this pressure is reached, the motor will automatically stop; adjust the minimum pressure. When it reaches this pressure, the motor will restart automatically.
(4) Check valve. Let the compressed air enter the air reservoir from the compressor and prevent the compressed air from flowing in the opposite direction when the compressor is turned off.
Page 49) Gas storage tank. The compressed air is stored in a size determined by the capacity of the compressor and the amount and pressure of the compressed air on site. The larger the volume of the gas tank, the longer the compressor running time interval.
(6) Pressure gauge. The pressure inside the gas tank is displayed. ) Automatic drainer. The water condensed in the gas tank is drained without manual operation.
(8) Safety valve. When the pressure in the gas tank exceeds the allowable limit, the compressed air can be discharged. ) Refrigerated air dryer. The compressed air is cooled to a few degrees above zero, causing most of the moisture in the air to condense, which reduces the moisture in the back system. ) Main pipe filter. Installed in the main pipeline, it has the minimum pressure drop and oil mist separation ability, which can remove dust, water and oil from the pipeline.
The components of the LL2 consuming system and the main functions) the output of compressed air. Compressed air is output from the top of the main pipe so that occasional condensate remains in the main pipe. When the compressed air reaches a low point, the water passes to the lower part of the pipe and flows into the automatic drain to remove the condensate. ) Automatic drainer. There should be a drain at the end of each lower joint that will be left in the pipeline and drained automatically by manually draining water. ) Air handling unit. Keep the compressed air clean and at the right pressure and deliver the lubricant to the parts that need to be lubricated to extend the life of these pneumatic components. ) Directional control valve. The direction of motion is controlled by alternately pressurizing and exhausting the two ports of the cylinder. )operating units. The pressure of compressed air is converted into mechanical energy, which can be a linear cylinder or a rotary actuator or a pneumatic motor. ) Speed ​​control valve. It is easy to realize stepless speed regulation of actuators.
Classification of 12 air compressors There are various types of industrial compressors, and the following two methods are classified. According to the structural form, the compressor can be divided into two types: volumetric type and speed type. Among them, the volumetric compressor can be divided into two types: reciprocating and rotating. Speed ​​compressors can be divided into axial flow, centrifugal, eddy current, axial flow + centrifugal composite, and jet type.
(2) Classification according to working principle a. Positive displacement compressor: It relies on reciprocating motion or rotary motion to change the working volume, thereby reducing the gas volume and increasing the gas pressure, that is, the pressure is increased by directly compressing the gas volume.
b. Power compressor: It relies on the function of rotating the impeller at high speed to increase the pressure and speed of the gas, and convert the velocity of a part of the gas into the pressure energy of the gas, that is, the action of the high-speed rotating impeller, so that the gas molecules get a high speed. Then, the speed is lowered in the diffuser to convert the kinetic energy into pressure energy.
At present, the most commonly used air compressors are piston, screw, vane, axial and centrifugal. In the tire industry, piston air compressors are the most widely used, and screw and vane are being promoted and developed.
L3 common air compressor performance comparison Lil piston air compressor piston air compressor is divided into two categories: single-stage piston compressor and two-stage piston compressor.
The single stage piston compressor compresses the inhaled atmospheric air to the required pressure in a single process. When the piston moves down, the cylinder volume is increased, the cylinder pressure is less than atmospheric pressure, and air enters the cylinder from the intake valve â–¡. At the end of the stroke, the piston moves upwards, the intake valve â–¡ is closed, the cylinder volume is reduced, the air is compressed, and the pressure is increased. As the piston moves upward, the pressure of the air in the cylinder rises. When the pressure is higher than the pressure in the exhaust pipe, the exhaust valve is opened and the compressed air is discharged into the exhaust pipe to the top of the piston. The compressed air that is output enters the gas storage tank before proceeding to the next working cycle.
Single-stage piston compressors are typically used in systems with lower pressures. For systems with higher pressure requirements, two-cylinder two-stage, double-acting piston compressors are required. When the two-stage piston compressor is working, the air is compressed in the first-stage cylinder and then removed. After cooling by the intercooler, it enters the secondary cylinder and continues to compress to the rated working pressure and then discharges. After the cooler is cooled, it enters the storage. Gas tank.
Page 50 Piston air compressors are more noisy than other types of air compressors. The temperature of the compressed air entering the tank is high (up to 140C at the highest), the pressure has continuous pulsation, and the unit energy consumption. Higher, volumetric efficiency, thermal efficiency and overall efficiency are not ideal. However, because the piston air compressor is simple in structure, cheap in price, convenient in maintenance, and its shortcomings can be compensated to a certain extent, it is still the most commonly used in the current tire factory and other industries.
The screw compressor production technology of screw compressors was introduced in the 1930s. In the 1970s, the first batch of oil-injected screw compressors was designed and produced in China. After continuous improvement, screw compressors have been used more and more widely.
The key to the continuous promotion of screw compressors is that their combined operating costs are much lower than those of piston air compressors. Take LU250W-13 screw compressor (hereinafter referred to as screw compressor) and L3.5-15/12 piston air compressor (hereinafter referred to as piston compressor) as an example: screw air compressor The displacement is 32m3/min, the rated output pressure is 13MPa, the motor power is 250kW, the volumetric efficiency is around 0.93, and the air is cooled.
The rated output pressure is 12MPa, the motor power is 132kW, and the volumetric efficiency is about 0.82. It needs to be cooled by softened water or tap water. The water consumption of the main machine is 48m3/h, and the water consumption of the aftercooler is 4m3/h. One screw compressor is equivalent. The number of piston air compressors is: the same compressed air is produced by the platform. The annual electricity savings for the screw compressors compared to the piston air compressors are (1a for 300 working rafts, 3 shifts, and the electricity price is 0 52 yuan / kWh, power factor is 085) Under normal circumstances, the unit price of electric energy consumption of softened water is about 015 yuan / m3 (the ratio of the electric energy consumption price of softened water pump to the water output per hour). The labor cost of softened water is about 001 yuan / m3 (the ratio of the total amount of artificial wages related to softened water to the corresponding amount of water per day).
(3) The unit price of softened water is about 4 yuan/m3, recycled, calculated according to the loss of 6%. The loss of softened water is not depreciation of demineralized water equipment and other related expenses, and the piston air compressor uses softened water. The cost is the same as that of the screw compressor. The cost of using the softened water per year for the piston air compressor is: in general, the annual maintenance cost of the piston compressor and the cleaning of the cylinder and other parts. The cost needs about 30,000 yuan, and the maintenance of the screw compressor is small. The maintenance fee is 550,000 yuan per year. Therefore, the same compressed air is produced, and the screw-type compressor can save the maintenance cost: the 13-screw compressor produces the same compressed air. The annual cost savings of the L35-15/12 piston air compressor is: therefore, the screw Compressors use a much better overall benefit than piston compressors. Replacing the piston compressor with a screw compressor is the latest trend in the development of aerodynamic compressors.
When the screw compressor is in operation, the two meshing helical rotors move in opposite directions, and the volume of free space therein decreases axially, thereby compressing the air between the two rotors. Compared with piston compressors, screw air compressors can deliver continuous, non-pulsating compressed air with simple structure, less wearing parts and low energy consumption (the power consumed during unloading is only 15% of the power at full load). X volumetric efficiency, low exhaust gas temperature (12~24C higher than ambient temperature), thermal efficiency and overall efficiency are ideal. Although the current purchase price of screw compressor is higher than that of piston compressor, it is operated according to Cost and performance price ratios are still relatively cost-effective.
Screw air compressors are mainly available in two types, oil-injected and oil-free.
L-3 sliding vane air compressor page 51 vane air compressor is a compressor popularized in recent years. Compared with other compressors, this model has obvious advantages, high reliability and long service life. With a rotating slide design, the operation is particularly quiet. The moving parts have only one rotor, the speed is as low as 1000r/min, and the reliability is high. With a service life of more than 100,000 hours, there is no need to replace the main metal parts, and the life is long and the residual value is high. ) Excellent performance and high specific power. The sliding piece itself automatically compensates for the gap with the stator cavity wall by centrifugal force, and there is almost no secondary compression, and the volumetric efficiency is high. ) Low maintenance and energy saving. Consumables only need to prepare oil, oil core and air filter. With standard energy-saving control device, it consumes less power during unloading operation. )transfer method. The compressor and motor are connected by a maintenance-free, inert coupling, eliminating the need for belts or speed gears. ) Light weight and small size. The vane compressor is light in weight and low in center of gravity and can be used in the field. The oil and gas pipeline is installed inside the fuselage, and the outer shape is small, and the peripheral control pipeline is small. The gas supply has high purity and good quality. The vane compressor has oily exhaust and low water content. The residual oil is less than 2X10-6, and the exhaust temperature and ambient temperature are within 10C.
Although the vane type compressor has many advantages compared with the piston type compressor and the screw type compressor, the current stage vane type compressor is still under development due to the price and flow rate of the equipment.
The choice of 14 air compressors and the requirements for operating compressed air systems are continuous and stable, especially for tire companies. Therefore, the choice of air compressor, how to configure and control will have a relatively large impact on the production cost, quality and stability of compressed air.
L4.1 Air Compressor Selection and Configuration For piston, screw and vane compressors, which one is selected by each company, the choice of specifications, the number of configurations and accessories, etc., can be based on the economics of the enterprise. The condition, plant layout, amount of compressed air, pressure and quality are determined. However, no matter how you choose, you should generally do the following to ensure the continuous supply of compressed air; (2) to ensure that the flow, pressure and quality of the compressed air meet the requirements of use; at the same time, due consideration should be given to the characteristics of the compressor, such as the standard volume flow. , volumetric efficiency, thermal efficiency, total efficiency and unit energy consumption;) should be equipped with an appropriate amount of spare machine;) If the pressure levels of the compressed air used vary widely, air compressors of different pressure levels should be configured separately; The air filter is installed before the compressor;) The piston air compressor should be equipped with a suitable aftercooler to prevent the temperature of the compressed air from being too high, which affects safety and use;) The capacity of each air compressor or the entire compressed air station should be configured. Suitable gas storage tank to reduce the periodic fluctuation of the discharge flow of the piston compressor or the pressure fluctuation caused by the uneven gas volume;) configure the corresponding oil water separator, air dryer, waste oil collector, etc. to meet the compression Air quality requirements;) The location of the compressed air station should be set as far as possible at each point of use Center to reduce the pressure loss of compressed air during transportation; 0) The delivery line of compressed air should be determined according to the position of the compressed air station and the layout of each gas point. The layout of the pipeline should be short and straight. , based on the principle of the shortest effective distance. In general, there are three types of laying, namely single-tree technical piping system, annular piping system and double-tree technical piping system. The pipeline can be laid underground or laid overhead, which is determined according to the terrain, foundation, laying cost and ease of maintenance. Buried pipelines should be protected from corrosion on the outer surface, and the pipelines laid overhead should be guaranteed not to freeze due to stagnant water in winter.
The operation control of the L4.2 air compressor must be maintained after each compressed air system is used. When compressed air is used, the supply of compressed air is required to be continuous, but the amount of compressed air used in the system is not fixed. The instantaneous air volume of the pipe network varies, and the peak and valley of the gas are used between the average gas and the average gas. The difference in air flow is relatively large.
Usually, the compressed air station is composed of multiple air compressors, and each air compressor is dragged by one motor and controlled independently. Before pressing the air station on page 52, the following three methods are usually used to adjust the control of the exhaust volume: 1 vent the excess compressed air; 2 turn off the motor; 3 close the suction valve to make the motor idling.
There are corresponding problems in the three ways of adjusting the amount of exhaust gas: 1 venting the compressed air will cause a great waste of energy; 2 stopping the motor regulating pressure is only used in a small-capacity air compressor. Frequent start and stop of the motor not only consumes a lot of energy, but also shortens the service life of the air compressor. 3 Close the air compressor suction valve to make the motor idling to adjust the pressure, and the energy waste is large. Because the energy consumption of the piston compressor during unloading operation is about 30% of the full load operation, the energy consumption of the screw compressor when unloading can reach 15% at full load. The motor starts with a large moment of inertia load, the motor The power required for no-load start-up is roughly equivalent to 2~3 times of the power consumed by full-load operation, and the time is about 5~60s. When the motor is frequently started to control the exhaust volume, the impact on the power grid is also large, and the energy consumption is relatively large. More obvious. When the gas consumption is constantly changing, the gas supply pressure inevitably produces a large fluctuation, so that the gas supply volume cannot be continuously adjusted, which is easy to cause damage to the equipment, and has a considerable impact on the power grid and the air compressor.
The current common method for adjusting the exhaust volume is to use a frequency converter to control the pressure of the air supply system. The pressure value is preset in the gas supply system or the gas storage tank by the pressure switch, and the system automatically loads and unloads according to the lower and upper limits of the preset pressure value to meet the gas consumption requirement. According to the change of the instantaneous gas consumption of the gas supply pipe network, the rotation speed and the number of running air compressors of the air compressor station are automatically adjusted, so that the pressure of the pipe network is maintained at a constant set pressure, thereby achieving the energy saving and the improvement of the air compressor. The purpose of gas quality, at the same time, realizes the automation of the control process, and automatically protects the air compressor from overpressure, overload, overcurrent and undervoltage.
Taking the frequency converter to control the pressure of the gas supply system, the energy saving effect is obvious: after using the constant pressure gas supply frequency conversion automatic control, the smooth soft start and soft stop of the control system can be realized, reducing the impact on the power grid and prolonging the service life of the equipment. The variable frequency constant voltage control mode automatically adjusts the difference between the gas delivery volume and the set amount through the built-in PID (proportional integral/differential regulator) to make the pressure constant; the system pressure converts the pipe network pressure into an electrical signal through the pressure transmitter. The PID unit sent to the inverter is compared with the set value, and according to the difference value, the calculation is performed according to the predetermined control mode, so that the inverter outputs the corresponding rotation speed to control the motor of the compressor, so that the actual pressure is equal to the set pressure. The purpose of constant pressure is to achieve continuous adjustment of the gas supply to ensure the stability of the pipe network pressure.
The types of air compressors that can be used to control the pressure of the air supply system are: piston air compressor, screw air compressor, and vane air compressor.
The control system of the new air compressor is ideal, and it can basically meet the requirements of high efficiency and energy saving. But for most tire companies, traditional piston air compressors are still in use. In order to improve the efficiency of these air compressors, reduce energy consumption, and reduce the production cost of compressed air, it is necessary to carry out inverter control transformation or other corresponding transformation of the air supply system.
(To be continued)
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