Tubing Pup Joint Coupling,Api-5ct Seamless Steel Pup Joint,Coupling 2-7/8 Tubing Henan Dongfanglong Trade Co.,Ltd , https://www.tjdflpetro.com
Keywords: Hekang frequency conversion, screw air compressor, energy-saving transformation I. INTRODUCTION Screw air compressors are devices that provide compressed air. Their motor capacity is large, and they operate continuously for years. The cost of electricity for general air compressors accounts for Use more than 70 percent of the cost. Because of the change in production conditions and the alternation of workers, the uncertainty in the use of gas causes frequent loading and unloading of air compressors, resulting in wasted energy. When the frequency converter and air compressor are used together, the supply pressure of the air compressor will be more stable, reducing the unloading time and saving the production cost. 
Figure 1: Hekang inverter application site
II. Operation of Air Compressor Before the Conversion Hikvision Inverter was invited by the energy-saving renovation to carry out the energy-saving transformation of the air compressor network consisting of four air compressors of Henan Hannai Group Co., Ltd. Yannai is the largest supplier of refractory products for the steel industry in China. The air compressor station that was transformed was composed of four air compressors, one 250kW Ingersoll-Rand and three 110kW Sullair screw-type air compressors. press.
Before the transformation of the equipment, the four air compressors all work in the power frequency state. The pressure adopts two-point control (upper and lower limit control), that is, when the air pressure in the air compressor reaches the upper limit of the set value, the air compressor closes the air intake valve through its own hydraulic pressure, and when the pressure drops to the lower limit of the set value The air compressor opens the intake valve. This leads to frequent unloading and loading of the air compressor, often with less air for the evening shift and the air compressor running at full speed, at which time this part of the electrical energy is wasted. Therefore, it is very necessary to reform the screw air compressor to make it energy-saving, improve equipment stability, reduce maintenance costs, and reduce noise pollution.
III. Design requirements for frequency conversion energy-saving retrofitting schemes According to the problems existing in the original working conditions and in combination with the production process requirements, the system must meet the following requirements after the air compressor is reformed:
1. According to the actual production volume of gas used to adjust the air compressor gas production, both to meet the production requirements, while reducing energy consumption.
2. The system has two sets of frequency control and power frequency control loops, and can effectively control the air compressor oil leakage problem when the air compressor fails.
3. After the original system adopts the inverter for speed regulation, the original main loop and the secondary loop control method of the air compressor cannot be changed.
4. Reduce operating noise, especially at startup and at full load, with significantly reduced noise.
4. The implementation of air compressor frequency conversion transformation The main motor of the air compressor is a 250kW motor with a rated current of 450A. According to the actual situation on the site, the Honda inverter provides a HID600A series high-performance inverter to control the air compressor. Remote pressure gauge to feedback the pressure of the gas tank. When the feedback pressure is higher than the production demand pressure, the frequency converter runs down until the set lower limit frequency. When the lower limit frequency continues to run for 300s, the frequency conversion sleeps; when the feedback pressure is lower than When the pressure is required, the inverter frequency rises and the compressor is loaded and operated. The electrical system adopts the frequency conversion bypass design. When the frequency converter fails, it can be switched to the original power frequency operation by rotating the frequency conversion bypass switch to improve the stability of the system. The main electrical circuit diagram is as follows: 
Figure 2: Schematic diagram of constant pressure gas supply
The main motor before the transformation has been running at full speed. During the operation, the pressure is always rising (even if the production process does not require so much pressure). When the pressure of the air tank rises to the upper limit pressure, the air compressor will stop. load. Usually when setting this parameter value, generally consider the use rate of the equipment and the need of the production process. The upper limit value will generally set the pressure 2 bar greater than the actual required value as the upper limit. The increase of exhaust pressure will generate power consumption. In effect, the power consumption increases by about 6% for every 1 bar increase in pressure.
After adopting the inverter PID constant voltage control system, the frequency conversion speed regulation system takes the pipe network pressure as the control object, and the pressure transmitter installed in the gas storage tank converts the pressure of the gas storage tank into an electrical signal and transmits the PID inside the controller. The regulator compares the pressure setpoint with the setpoint PID control mode according to the magnitude of the difference, generates a control signal to control the output voltage and inverter frequency of the inverter, and adjusts the speed of the motor so that the actual pressure Always maintain the set pressure, resulting in a constant air pressure.
Hekang Inverter applies the optimized SPWM algorithm to the current and equipment impact when the main motor is started, which enables the motor to start smoothly, increase the starting torque, and reduce the impact of the inrush current on Other equipments; it adopts advanced technology in the acceleration process. The multi-point acceleration curve reduces the wear of the bearing and the main screw of the head due to the quick start, which can greatly increase the service life of the equipment and the maintenance period of the mechanical equipment. In addition, if the frequency converter fails, the production process does not allow the air compressor to stop. Therefore, the system sets the power frequency and frequency conversion function, so that when the frequency converter fails, the power supply directly through the power frequency contactor, so that the air pressure The function works as usual.
V. The energy-saving 250kW ordinary unit runs for 8759 hours a year, of which loading time is 2442 hours, unloading time is 6317 hours, and electricity is calculated at 0.7 yuan/kWh.
1, no-load loss:
Unloading time × No-load current loss during unloading (1.732 × 0.38 × 175 × 0.85) × 6317 hours/year = 618,442 kWh; but taking into account the screw air compressor at low frequencies to ensure that the oil does not leak, generally required The frequency conversion lower limit frequency is set to 30Hz, and the frequency conversion power saving is: 618442×40%=247377 degrees.
2, pressure loss:
Load time × Loss from 1 bar differential pressure 0.6 × 7% × 250 kW × 2442 hours / year = 25641 degrees.
In summary, the frequency conversion unit is 247377+25641=273018 kWh lower than the average unit.
Annual savings in electricity costs 273,018 × 0.7 yuan / degree = 19,111 yuan.
Sixth, the system should pay attention to the problem of transformation 1, the screw unit can not be reversed operation, the transformation must pay attention to the direction of motor operation.
2. Adjust the loading pressure equal to the set pressure (because the frequency converter has a lower limit frequency), so as to prevent the inverter from accelerating for useless work in the unloaded state.
3, need to pay attention to the problem of heat dissipation of the motor, the motor uses frequency conversion to speed, the speed is reduced, the cooling effect of the motor fan must also be reduced.
4, need to pay attention to the air compressor lubrication problem, the lower the speed of the air compressor, the smaller the consumption of lubricants, the worse the lubrication effect.
5. System pressure setting problem Under the requirements of the production process, the lower the pressure setting is, the better, because the higher the exhaust pressure of the air compressor is, the higher the required motor shaft power is, and the more the motor consumes power. .
7. The small combination of HID600A series of high-performance vector inverters has been running well on energy-saving reform of air compressors, effectively reducing the power consumption of air compressors, improving system stability and reducing maintenance costs. Screw air compressor as a long-term supply of the power source of the compression equipment, the frequency conversion energy-saving transformation of the market prospect is considerable, Hekang converter in the air compressor on the energy-saving transformation worthy of widespread promotion and use.
The Application of Hekang Frequency Conversion in Energy Saving Reform of Air Compressor
Abstract : Screw air compressors are prone to frequent loading and unloading during operation, which not only affects the production efficiency due to the unstable supply pressure, but also leads to high production costs due to large energy consumption. Therefore, the energy-saving renovation of air compressors is imperative. Hekang Inverter, with excellent control performance and high-quality after-sales service, carried out energy-saving renovation of air compressors for Henan Hannai Group, with stable control performance and significant energy saving effect.