In excavation of deep foundation pit and other deep excavation projects, due to the seepage of foundation pit, a large amount of stagnant water must be pumped to the lower reaches of the riverbed by pumps to control the water accumulation at the lowest water level (bottom valve Office) above. If more pumping, the pump body will be filled with a large number of gas and idling can not be on the water, which will endanger the safe operation of the pump, resulting in energy loss. In construction practice, in order to ensure the control of the minimum water level, you must: ①adjust the pump valve to control the flow, to prevent water pumping body pump; ② close the pump valve, the water level below the minimum water level when the man-made shutdown . Based on the above two situations, in the existing equipment, only add some accessories and circuits, so that light-duty pump can run at full capacity, so as to achieve the purpose of reducing labor intensity can automatically control, but also reduce energy consumption and reduce engineering investment. 1 pump automation control components 1.1 Magnet float water level signal Magnet float water level signal is basically composed of a float, conduit, reed pipe and the outer tube and other components. Reed switch is the two pieces of iron-nickel alloy reed closed in the glass tube, the normally open reeds were fixed at both ends of the glass tube, the role of the permanent magnetic field, the reed is magnetized, the free end of the magnetic Just the opposite, the use of "the opposite sex phase suction" principle, to overcome the reed moment, reed action, so that the circuit is closed, when the permanent magnet away from the reed pipe, the reed is disconnected. Float is a built-in permanent magnet floating plastic ball. The water level rises and falls to make the float change correspondingly, the magnetic force of the permanent magnet causes the reed contact in the conduit to act, send out the corresponding water surface signal, the water level annunciator principle sees Fig. 1. 1.2 shows the annunciator shows the annunciator principle shown in Figure 2. When the tube flow is greater than the signal flow rate of the provisions of the action, the target and the target rod force and drive the micro switch, so that normally closed contacts open, normally open contacts closed, the normal signal; when the tube water flow decreases , The moment of action on the target rod also decreases. When the flow rate is lower than the setting value of the annunciator, the normally closed contact of the micro switch is closed, and the normally open contact is disconnected to give an alarm signal. 1.3 automatic water level detection and display circuit 1.3.1 water level detection circuit diagram If the corresponding changes in water level can be displayed by the signal light, the water pump to stop providing a good monitoring. Figure 3 is the automatic control of water level and display circuit. 1.3.2 Automatic water level detection and display circuit principle When the water level changes in the water level signal to the float to move to the lower water level position, the float near the lower limit of the magnet reed 0G, reed pipe in the nickel-iron alloy sheet Affected by the magnetic force, normally open contacts closed. See Figure 1 and Figure 3. Road, OZJ relay coil power, the relay pull, OZJ normally open contact closed, normally closed contact open, the current through the A point → 1ZJ normally closed When the water level reaches a low water level, the float magnet close to the low water level Reed 1G , 1G normally open contacts closed. Current through the A → 1C signal light indicates that the water level is at a low water level. And so on, 2G closed, 1XD signal light off, 2XD water level signal light, said the water level in the water level. 3G closed, 2XD signal light off, 3XD high water level signal light, remind operators to pay attention to equipment safety. 2 automatic water level control 2.1 submersible pump automatic, manual drainage diagram (see Figure 4). (1) submersible pump automatic control circuit, shown in Figure 5. Submersible pump automatic drainage simple and reliable, unattended guard operation can be achieved for water seepage, water volume is not large low-lying areas. (2) submersible pump automatic, manual drainage principle of control circuit shown in Figure 5. Close the HK switch, open the ZK switch is manually drained, the principle is simple, not repeat them. 2.2 bottled valve irrigation centrifugal pump automatic control (1) at the end of the valve centrifugal pump automatic irrigation diagram shown in Figure 6. Make a water tank for centrifugal pump irrigation, so that the pump body is always filled with water. Pump suction diameter of 300 mm below the small pump can be set in the suction pipe at the end of the valve, open the pump before the pump to start irrigation, equipment and methods are relatively simple. As the water pipe head loss greater, and the end of the valve is easy to impurities, sediment and other obstruction and lax, affecting the irrigation started, need to be cleaned often, it is only applicable to small pumps. Each centrifugal pump outlet pipe generally placed on the check valve, when the head is below 20 m, no check valve. (2) automatic water tank water control circuit design shown in Figure 7. To ensure that there is a sufficient amount of water in the tank for the centrifugal pump to irrigate, the volume of the tank should be filled with at least one centrifugal pump, and an anti-corrosion treated open tank can be used. Working principle: current through the C phase → TA button → ZK switch → C1 → C normally closed → ZJ1 coil → A phase, the relay ZJ1 energized normally open contacts closed after closing, connected to the contactor C coil, the current through the C phase → TA button → ZJ1 normally open (closed) → ZJ0 normally closed → C coil → RJ normally closed → A phase. At the same time, the contactor normally open contact closed self-protection, locking self-protection circuit; contactor normally closed contact is disconnected, cut off the ZJ coil loop, ZJ1 relay power, normally open, normally closed contacts back to the home position. It is not difficult to see that the contactor C normally closed role is to avoid the ZJ1 normally open contact to start the contactor C time is too long to set, so as not to stop at this time when the button is released and then start again. (3) The automatic control and display circuit design of the centrifugal pump with bottom valve is shown in Fig.8. (4) The automatic control circuit principle of centrifugal pump with bottom valve is shown in Fig.9. And 0XD signal power, the relay power, convergence back to the original position, the lower limit signal light off. 1ZJ normally closed contacts off, making No. 2 motor circuit 2C coil loop off, No. 2 motor can not run. 1ZJ normally open contact closed the following actions: (a) current through A point → 1ZJ normally open (closed) → 0ZJ normally closed → 2ZJ normally closed → 1SJ normally closed → 1ZJ coil → 0:00, low water level control circuit from Lock; (b) No. 1 motor control loop current through the C point → 1TA button → 1ZJ normally open (closed) → 0ZJ normally closed → 1C coil → 1RJ normally closed → A point. 1ZJ normally open contact to start No. 1 motor, 1C contactor after closing, self-protection contact closed, self-locking loop, (Note: 1ZJ normally open contacts will be disconnected after 1 s, therefore, 1ZJ normally open contacts closed only 1 s). 1SJ time relay power delay 1 s, 1SJ normally open contacts closed, self-locking loop; 1SJ normally closed contact disconnect the 1ZJ coil loop. And so on, the dry reed pipe normally open contact 2G closure, similar to the above, respectively, will make 2XD signal light shows the water level and start 2 centrifugal pump motor operation. In summary, when the water level reaches the lower limit of water level stop motor No. 1; water level reaches the low water level when the pump motor No. 1, stop No. 2 pump motor; water level to reach the water level when the pump motor No. 2 started. In addition, from the circuit diagram can also be seen, when the pump on the 1st small amount of water or traffic interruption, the normally closed signal flow indicator 1SLX closed contacts. Current through the A point → 1C normally open (closed) → 1SLX normally closed → 1DL → 0:00 bell 1DL alarm, tweet. 2 pump flow is small or not on the water, bells 2DL alarm call. (5) Centrifugal pump with the end of the valve failure of automatic control can be changed to manual operation. At this time just pull down the HK switch, according to the conventional method of manual operation. 2.3 Bottomless Valve Centrifugal Pump Drainage Automation 2.3.1 Analysis of vacuum suction pipe The suction pipe is not provided with a bottom valve, and the head loss is small, and the vacuum pump is used to start. Vacuum pumps start water quickly, high efficiency, suitable for all sizes of pumps. Especially for large pumps and pipes with longer pipes. Pumping time is generally 3 to 5 min. According to statistics, there are many large-scale feedwater pumping station, drainage pump station is a water ring vacuum pump water diversion. This method uses a vacuum tank, water seal cans, water separator, automatic exhaust valves, vacuum gauges and other electrical contacts equipment. It is easy to see through their analysis, the higher the degree of vacuum, the higher the water level in the diversion pipe is raised. In spite of this, due to centrifugal pump body, inlet pipe inevitably leaks, in fact, is not very satisfactory. The author believes that the removal of the vacuum tank, water sealed cans, automatic exhaust valve vacuum pump can still maintain the original exhaust flow, to maintain its gas, water mixture in the centrifugal pump body ratio. In order to detect the gas, water flow, produced a gas, water detector. The detector saves investment, easy installation, suitable for site drainage. Structure diagram shown in Figure 10. Figure 10 tracheal, water pipes have a certain height difference. Trachea to the height of the water surface should be greater than the suction pump suction to ensure the normal separation of gas and water. When the gas and water mixture from the centrifugal pump passes through the gas and water detectors, the gas has a lighter specific gravity and most of the gas passes through the gas pipe according to the principle of gas and water separation. The water has a relatively large specific gravity and passes most of the water from the water pipe . The current detector in the airway detects the gas flow; the current detector in the waterway detects the flow of water. The gas flow plus water is the total flow of gas and water mixture. The gas flow rate critical value refers to the minimum percentage of gas in the gas-water mixture when the centrifugal pump is filled with water and gas, and the centrifugal pump can rotate the blades to pump water. Different types of pumps have different gas flow thresholds that need to be determined in practice. Gas, water detector principle is the gas flow greater than the set action flow, the flow indicator 1SLX electrical contacts closed or disconnected, the signal, the water flow is greater than the set action flow, 2SLX electrical contacts closed or disconnected, issued The signal is shown in Figure 11. Their combined contact circuit open, broken will be issued to open the centrifugal pump signal. 2.3.2 vacuum pump hanging diagram (see Figure 12) This circuit and the previous section is about the same, but added two solenoid valve coil. Before starting the centrifugal pump, the vacuum pump is turned on to extract the air from the centrifugal pump. When the mixture of air and water is pumped up, the gas and water are separated in the gas-water detector because the suction of the vacuum pump is lower than the height of the gas pipe. Gas through the gas pipeline, water through the water pipe was pumped into the gas separator vacuum pump. The water in the gas separator is designed for vacuum pump sealing and cooling purposes. The solenoid valve in Figure 12 opens only when the vacuum pump is running, and when the centrifugal pump is running. After the vacuum pump is turned on, the solenoid valve 1DCF power open the valve, vacuum pump hanging water, gas, water through the gas, water detector issued a No. 1 centrifugal pump signal, No. 1 centrifugal pump start running. Similarly, when the water level reaches the water level, 2ZJ normally open contacts close the vacuum pump, solenoid valve 2DCF open, gas, water, gas, water detector issued a signal to open centrifugal pump No. 2, No. 2 centrifugal pump start Run, see Figure 13. When the automatic control fails, you can pull down the HK switch, close 1SK, open the vacuum pump hanging water, and finally open No. 1 centrifugal pump. Similarly, close the 2SK, open the vacuum pump hanging water, and then turn on the 2nd centrifugal pump to achieve the purpose of manual control. 2.3.3 automatic control of vacuum pump hanging and centrifugal pump No. 1, No. 2 centrifugal pump automatic control circuit design (see Figure 14) When the water level reaches a low water level, 1ZJ normally open contact closed to open the vacuum pump, as in 3 to 5 Bell No. 1 pump is not open bell alarm. After the vacuum pump is turned on, the solenoid valve 1DCF energized open the valve, vacuum hanging water, gas, water through the gas, water detector issued a No. 1 centrifugal pump signal, No. 1 centrifugal pump started. Similarly, when the water level reaches the water level, 2ZJ normally open contacts close the vacuum pump, solenoid valve 2DCF open, gas, water, gas, water detector issued a signal to open centrifugal pump No. 2, No. 2 centrifugal pump start Run, see Figure 13. When the automatic control fails, you can pull down the HK switch, close 1SK, open the vacuum pump hanging water, and finally open No. 1 centrifugal pump. Similarly, close the 2SK, open the vacuum pump hanging water, and then turn on the 2nd centrifugal pump to achieve the purpose of manual control. Site drainage is an indispensable site for each important process, energy consumption, manpower and more, the drainage control circuit requires a simple and reliable. The automatic control principle introduced above can save labor input and can be conveniently changed to manual operation when the control circuit fails. Therefore, the drainage work is uninterrupted, so the energy-saving effect is obvious. For example, a pump has an 8 (20.3 cm) pump with a flow rate of 400 m³ + 3 / h, a head of 40 m and a motor power of 55 kW. Typically, the output of the control valve is 24 h running. Pit seepage water volume of 150 m \ +3 / h. As the valve is closed, the load on the pump is reduced. The actual running current of the motor is about 60 A, which is equivalent to the power. According to this calculation, each 8 (20.3 cm) pump can save 13 500 kW · h per month. Annual savings of 162 000 kW · h. Energy-saving effect is obvious, substantial economic benefits.
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