4 Constant Pressure Air Supply Control Scheme Design Screw-type transformer variable frequency control According to the motor theory, the magnetic flux density is kept constant to maintain a certain torque. This requires maintaining the stator voltage and stator frequency ratio to be substantially constant. Aiming at the problems existing in the original gas supply control mode, after the above analysis, the constant pressure gas supply should be realized by the frequency conversion speed control method. The actual pressure P is collected by the pressure transmitter and transmitted to the PID control center, the collected signal is compared with the initial pressure value P., and the obtained difference is operated according to the quota control mode, so that the generated control command The operating frequency and speed of the motor are controlled by the frequency converter VWF, so that the actual pressure value can be dynamically controlled without deviating from the initial pressure P... The system adopts a closed-loop pressure regulation method to add a pressure to the pressure gas storage tank. The sensing device converts the detected pressure signal into a current signal of 4 20 mA and sends it to the PID regulator of the core link of the frequency converter. The regulator compares the received signal with the pressure set value to output an output control command, and the frequency converter According to the output frequency of this command, the speed of the motor is changed to adjust the air supply pressure and keep it constant, so that the air compressor is always in the power-saving operation state, as shown.
At the same time, the scheme of the compressor energy-saving retrofit system can also change the power frequency and frequency conversion in addition to the original protection and control system. With this solution, the starting work of the air compressor can be controlled by the frequency converter to realize the soft start, which protects the impact of the starting current on the motor during the hard start process. The exhaust pressure after the transformation is compared as shown.
After the implementation of the screw air compressor frequency conversion energy-saving transformation, the specific application includes several aspects of operation. First, the screw air compressor system control is carried out, the system is set to the pressure closed loop, and the given pressure input is adjusted appropriately. When the negative feedback regulator causes the output frequency to be too low, the energy consumption can be reduced by the buck, but has its own rating. Pressure limit, when the actual pressure is small, it is easy to stabilize the pressure supply. Secondly, set the acceleration deceleration time that satisfies both the process requirements and the system reliability requirements. If the acceleration time is too small, the current will be too large due to the large slip rate during startup and acceleration. The deceleration time is too small because of the module capacitor voltage. Too high impact on system reliability, the operation of this step must be set in accordance with relevant specifications and engineering experience. Once again, the modified air compressor system must meet certain pressure values ​​before it can be started in order to operate normally. Finally, after the frequency conversion transformation, the motor energy consumption is reduced, and the corresponding motor shaft temperature is also reduced, and the wear consumption is reduced. On the one hand, the life of the equipment is improved, and the other (down to page 73) 3 integral installation and debugging of the water inlet ball valve Ball valve installation (1) Measurement and inspection of the upstream steel pipe outlet and the downstream volute inlet size, the Y-axis deviation is less than ±8mm, the center (elevation) deviation does not exceed 5mm; check the ball valve base wheel pit size to meet the design and ball valve installation requirements; (2) The center of the pressure steel pipe and the volute is welded to a centerline frame, and the pressure steel pipe and the center of the volute are used to determine the installation center and elevation of the ball valve; (3) the measurement point is determined, and the Y-direction coordinate of the ball valve is determined; (4) The measuring pressure point Y is used to cut the upstream pressure steel pipe to the coordinate, the lower part of the steel pipe is welded to the hanging pipe, and the tools such as the tensioner and the jack are prepared; and the welding ring is pre-buried on the lower part of the water machine floor floor. (5) hoist the ball valve base bolt and the foundation plate, and adjust the elevation of the ball valve base plate according to the pressure steel pipe and the volute center line and the measuring ball valve Y axis. (6) Grinding the upstream connecting pipe of the ball valve to weld the groove, lifting the upstream connecting pipe into the ball valve gallery and mounting it on the welding plate on the lower part of the penstock, and pulling the upper part with a tensioner; For example, the lower part of the connecting pipe is supported by the buttress and the jack. The upper part of the connecting pipe is hung on the floor sling ring of the water machine floor with the lt manual hoist; (7) the upstream line is adjusted according to the center line of the pressure steel pipe and the volute and the Y axis of the measuring point. The distance between the flange of the connecting pipe and the center line (1775mm), and adjust the verticality of the flange surface (0.2mm/m), the center of the connecting pipe (elevation) should not exceed 3mm; (8) According to the installation center of the ball valve, the inlet of the downstream volute Section; welding rings on the pre-embedded steel plate of the water machine floor slab in advance to prepare for lifting the downstream connecting pipe and expansion joint; (9) respectively hoisting the downstream connecting pipe and the expansion joint placed on the ball valve gallery floor, so as not to affect The ball valve should be hoisted; (10) lifting the ball valve and adjusting the verticality of the flange surface of the ball valve within 0.2mm/m, lifting the ball valve into the corridor and connecting with the upstream connecting pipe; (11) adjusting the center, elevation and verticality of the ball valve , reinforce the ball again (12) 10t manual hoist is mounted on the bottom sling of the bottom floor of the water valve floor of the ball valve layer, and the downstream connecting pipe is hoisted at the inlet end of the volute. The installation and adjustment method is the same as the upstream connecting pipe; ±20) is less than 760, and Check the parallelism of the two flange faces; lift the expansion joint and adjust the verticality to less than 0.2mm/m, the telescopic joint flange is connected with the downstream connecting pipe and the right valve body of the ball valve; (14) using a manual wrench and a hydraulic tensioner Tight ball valve and upstream connecting pipe, expansion joint, expansion joint and downstream connecting pipe flange bolt.
3.2 Commissioning (1) The unit is tested with continuous operation for 72 hours at full load. After completing the above test project according to DL507 "Starting Test Procedure for Hydroelectric Generating Sets" and verifying the qualification, carry out a continuous operation test with full load 72h with the hydroelectric generating set. After the continuous operation test with load 72h is completed, the operation is normal, and it is considered that it is necessary to have no shutdown inspection and directly enter the reliability operation.
(2) Reliability operation. After completing the continuous operation test with full load for 72 hours, each billiard valve must be operated reliably to verify whether the ball valve and its ancillary equipment can be put into commercial operation.
4 Operation and evaluation of the inlet valve The Maerguei hydropower station was officially put into operation on October 24, 2011. The DN2700 super-caliber hydrodynamic double-sealed ball valve has withstood the test and achieved the design requirements. application.
Through the rigorous appraisal and evaluation by the experts of the appraisal committee and the judging committee, it is unanimously concluded that the DN2700 extra large diameter hydraulic turbine hydraulic double seal ball valve has novel design, reasonable structure and reliable performance, and the comprehensive technical performance has reached the international advanced level, which can completely replace the imported products.
5 Conclusion The successful application of DN2700 extra large ball valve in Maerguei Hydropower Station has promoted the development of China in the design and manufacture of large ball valves. At the same time, it is also inseparable from the meticulous organization of the construction unit, the optimization of the process, and the construction of high standards. Through the application of the Maerguei Hydropower Station, China has taken a solid step in the localization of large-scale ball valves, and has trained a high-level installation team and accumulated rich construction experience.
Hubei Hongcheng General Machinery Co., Ltd. Turbine Inlet Hydraulic Ball Valve QF265-WY-270 Instruction Manual, 2010 China Water Conservancy and Hydropower Seventh Engineering Bureau Electromechanical Installation Branch Maergai Project Department. The installation and construction measures for the ball valve of the inlet and outlet of the mechanical and electrical installation project of the Maergai Hydropower Station, 2010 (continued from page 71) also require that the operation sequence of the isolating switch and circuit breaker must be strictly operated.
5 Investment and return According to this method, two 250kW, 380V water-cooled box-type oil-injected screw compressors (Atlas Copco) are used in this mine: 24 hours a day, 320 days a year, the electricity bill is 0.6 yuan / kWh, motor working efficiency 80%, power saving effect calculated by 20%: 80% motor working efficiency x 20% power saving effect = 368640 yuan.
After the variable frequency energy-saving transformation of the screw air compressor, the air compressor system realized a number of energy-saving mechanisms, greatly reducing the maintenance and repair costs of the equipment, and performing well in practice. The operation results show that the modified system not only improves the reliability. And the energy saving effect is obvious, and significant direct and indirect economic benefits are obtained.
Zhang Yanbin. Frequency conversion application practice. Beijing: Mechanical Industry Press, 2000 Han Anrong. General purpose inverters and their applications. Beijing: Mechanical Industry Press, 2000 Cui Jian. Siemens Industry Network Communications Guide. Beijing, Mechanical Industry Press, 2004
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