The design of the water pumping house is Q=200,000 m3 /d, and 5 submersible pumps are installed. The maximum operating condition is 4 and 1 standby.

The pump operation schedule of the pump house is controlled according to the water level of the clean water tank of the water purification plant. Self-control process requirements: The water level of the clean water tank of the water purification plant can be displayed in the PLC station No. 1. When the water level of the clear water pool is below 2.30m, four water pumps run; when the water level of the clear water pool is between 2.30 and 3.20m, two water pumps run in water; When the water level of the clear water pool reaches 3.30m and the overflow delay is 5min, the water pump in the pumping station will stop running.

The pump unit of the pumping house should start the pump with a small number of running hours when starting up. When stopping the operation, stop the pump with more accumulated running time.

The data collected by the station: water source level of the Yangtze River, water temperature, pH value, raw water pipe pressure, submersible pump motor current, motor temperature, etc. The water level of the water source should be monitored in real time and recorded automatically. The pump cannot be started and stopped according to the program requirements, and the electrical parameters exceed the set value and the pump soft starter fault requires an alarm. When the alarm is called, the sound and the screen are required to appear at the same time, and the alarm part is displayed.

2 Dosing room, flocculation sedimentation tank No. 2 PLC station

2.1 automatic dosing system

The main equipment of the automatic dosing system is the flow current monitor, the metering pump and its associated variable frequency speed control device. The dosing room is designed according to Q=200,000 m3 /d, one flow current monitor and three diaphragm metering pumps.

The automatic control of dosing is feedforward control. According to the measurement, the flow current value in the water after mixing is compared with the set value, and this is used as a basis for controlling the dosage of the medicine. The feedforward water sample sampling port is set on the pipe between the tubular static mixer and the flocculation sedimentation tank inlet after the dosing. The set current value of the feedforward control is adjustable according to the measured value of the water plant test. The adjustment of the dosage of the liquid medicine is realized by a metering pump equipped with a frequency conversion speed regulating device, and the dispensing point is at the water inlet end of the tubular static mixer. The metering pump draws the liquid from the solution tank and adds it to the water. The three metering pumps need to be installed once in the long-term and will be used in the near future.

The dosing amount is controlled by the SCD meter. Under normal circumstances, the SCD controller directly controls the variable frequency speed control device to adjust the dosage. If the SCD meter fails, it is controlled by PLC No. 2.

There are a total of 3 compartments in the dosing solution pool. Each cell is equipped with an ultrasonic level gauge. When the first compartment level is reduced to half, the second compartment is full, and the third compartment is prepared for standby. When the working solution level drops to the set lower limit (-1.0m), the dosing metering pump should automatically switch to another cell.

The station system has the source water flow, turbidity, pH value and the flow current value of the SCD meter, the dosage of the three metering pumps, and the liquid level of the three grids of the solution tank can realize real-time monitoring.

When the working solution pool level is lower than the set lower limit (-1.0m), the other cell is not fully filled (up to 0.85m) and an alarm is required. The solution pool liquid level is lower than the set lower limit value and cannot be switched. The metering pump in operation does not absorb the liquid medicine, and the metering pump damper pressure drops or rises above the set lower limit or upper limit value and on the metering pump suction pipe. Electric ball valve failure, etc., in addition to automatic switching standby metering pump work, should be alarmed. The alarm request is the same as the No. 1 PLC station.

2.2 flocculation sedimentation tank

The flocculation sedimentation tank is a joint of a grid flocculation tank and a inclined tube sedimentation tank, and is divided into four groups, each of which has a water quantity of Q=50,000 m3/d and can be operated separately. Each group of flocculation tanks is provided with 9 sludge discharge pipes. Each set of sedimentation tanks is equipped with a truss pump suction scraper and an ultrasonic mud level gauge. The mud level gauge is installed at the inlet end of the sedimentation tank. The mud scraper automatically controls the operation according to the mud level measured by the mud level meter, and the scraper can only stay at the water inlet end of the sedimentation tank. When the mud level reaches the set mud height (0.60m) or the flocculation sedimentation tank continuously does not discharge the mud for more than 12~24h (the value is adjustable), the mud is started. The mud discharging method is as follows: 9 pneumatic mud discharging valves of the flocculation tank are arranged to rotate mud by number, each row is 1~2min (the value is adjustable), the interval is 0.5min; the sedimentation tank scraper runs along the sedimentation tank for the whole time, starting from The end points are the inlet end of the sedimentation tank. Each group of mud discharge systems cannot work at the same time. If one set value is reached at the same time, one set of mud is discharged, and the other set is randomly waiting.

The station system can provide the following data: operating conditions and cumulative operating hours of the scraper, operating conditions of the flocculation tank pneumatic mud valve, sedimentation tank effluent turbidity (NTU), pH value, electrical equipment parameters.

When the scraper brakes (cannot run and stop according to the set stroke), the mud pump of the scraper is faulty, the mud level of the sedimentation tank is over-limit (Hh>0.6m), and the flocculation sedimentation tank continuously does not discharge mud timeout, flocculation tank If the mud valve is faulty and the electrical equipment is faulty, it should be alarmed. The alarm request is the same as the No. 1 PLC station.

3 gas water backwashing filter, chlorination room No. 3 PLC station

3.1 gas water backwash filter

The project uses a gas-water backwash filter, a total of 16 grids, two rows, the middle pipe gallery, and the backwash pump room is located in the middle of the filter. The automatic filter control system includes automatic filter control, automatic backwash control and automatic operation control of the air compressor station.

The filter is required to reach the constant water level constant speed filtration automatic control. The target monitors the water level change in real time through the ultrasonic level gauge, controls the opening of the filter clear water outlet valve according to the water level change, adjusts the water output and adjusts the filter water level height to change in a small range. achieve.

The backwashing of the filter is carried out by air blasting, combined washing with gas and water, and rinsing in three stages. The filter tank meets any of the following conditions: backwashing: the head loss of the single filter is 1.8m (adjustable); the continuous running time is over 48h (adjustable); when the clean water valve is fully open, the water level in the pool exceeds the highest control Water level (elevation 3.20m); forced flushing of a certain grid or grid by filter according to the operation requirements. Only one filter can be backwashed at a time. When several filters meet the backwashing conditions at the same time, they are ordered in sequence. The flushing interval of each two grids is 10min.

1) Valve opening and closing procedure during backwashing. Close the filter inlet valve, delay 1~1.5min, open the drain valve; close the filter outlet valve; open the blower outlet valve, open the blower, open the filter inlet valve for air punching, and the air stroke lasts 3min (adjustable Start; backwash water pump, turn on the backwash pump outlet valve in turn, filter backwash inlet valve (air pump valve does not close, continue to air intake), gas and water combined backwashing, lasting 4min (adjustable); turn off the blower Close the filter backwashing intake valve, separate water rinsing for 4min (adjustable); close the filter backwash inlet valve, backwash water pump outlet valve, backwash water pump, close filter backwash drain valve; Open the filter inlet valve, open the filter clear water outlet valve; open the DN50 solenoid valve on the filter intake pipe to release residual air for about 10s.

2) Automatic operation control of air compressor station. The engineering filter and the flocculation sedimentation tank mud valve are all pneumatic valves, and the gas source is provided by an air compressor station located beside the filter tank. The air pressure of the compressed air storage tank of the air compressor station needs to be stabilized within a certain pressure range to ensure the normal operation of the pneumatic valve. When the pressure of the gas storage tank is lower than the minimum pressure, the air compressor is automatically started to work, and when the pressure of the gas storage tank reaches the set pressure, the air compressor is automatically shut down.

The filter flushes the water pump, and the blower requirements can be operated in regular rotation. The air compressor can automatically rotate and start and stop, so that the working time of the equipment is even.

3) Data collection and alarm requirements. The parameters that the station can provide are: head loss of each filter, filtration time, filter water level height; pneumatic valve opening and closing state of each filter, water outlet valve opening degree; flushing pump operating conditions (including flushing water pump pressure pipe) Upper pneumatic butterfly valve open and close state), and accumulate timing; blower operating conditions and cumulative timing; air compressor operating conditions and cumulative timing; electrical parameters.

The following faults in the system should be able to alarm: flushing pump failure (including failure of pneumatic butterfly valve on flushing water pump pressure pipe); blower failure (including its valve failure); air compressor failure; pneumatic valve failure of each filter; filter backwashing process The parameter control value (head loss, maximum limit water level and running time) exceeds the value; the water level of the clear water tank exceeds the limit (3.3m) alarm, and the filter clear water outlet valve is closed; the electrical parameter exceeds the limit alarm. The alarm request is the same as the No. 1 PLC station.

3.2 chlorination system

After filtering, the chlorine is added once, and the dosing point is set on the filter to the clear water pipe. The chlorination system uses compound loop control, which is the filter water flow ratio and residual chlorine feedback control. The inflow water flow signal of the clear water pool is provided by an electromagnetic flowmeter provided on the inlet pipe, and the residual chlorine feedback sampling point is set at 10 times the diameter of the pipe after the chlorination point. The composite loop controller automatically drops to flow ratio control when the residual chlorine feedback signal is lost.

The system is equipped with 3 chlorination machines, 2 for 1 preparation, and rotation for use. Each chlorinator can automatically switch after running for a period of time; the chlorinator in operation should also be able to automatically switch. Two groups of gas sources, 1 with 1 standby, when the working gas source runs out of chlorine bottle pressure drops to the set value, stop its work and can automatically switch to the standby gas source to continue working.

The parameters that the station can provide are: operating conditions of the chlorinator and accumulating timing; automatic switching signals of two sets of chlorine bottles; set value and measured value of residual chlorine in the factory; and residual chlorine in the sampling point after chlorination ; the amount of chlorine added per hour.

The system should be able to alarm when the following faults occur: the chlorinator in operation is faulty, automatically switch the standby machine into operation, and alarm at the same time; if the switch fails, it will also alarm; when the working air source is used up, the standby air source will be automatically switched into operation and alarm If the switch fails, the alarm will also be given; the chlorine content in the air between the chlorine bottle or the chlorination room exceeds the set value alarm; the excess chlorine of the factory water should be alarmed (above 20%) compared with the set value.

4 pumping station, No. 4 PLC station

There are 5 pumps in the pump room, and the maximum operating condition is 4 for 1 unit. When the water level of the clear water pool is below 1.0m, two pumps will run; when the water level of the clean water tank drops to 0.5m, the pump will stop running; when the pressure of the factory water pipeline suddenly drops sharply, the pump will stop running; 5 pumps need to be able to rotate evenly.

The station can provide the following parameters: instantaneous and cumulative values ​​of factory water flow, factory water pressure, turbidity, residual chlorine, pH value, real-time monitoring and record storage; pump operating conditions (open, stop), And the accumulated number of hours; the water level of the clear water pool; the electrical parameters of the pump unit operation; the electrical parameters of the high and low voltage switch cabinet.

The following fault alarms appear in the system: the factory water pressure is lower than the set value, the turbidity exceeds the set value (set value is 1NTU), and the residual chlorine exceeds the set value (set value is 0.5~0.8mg/L); Can not automatically open and stop according to the program; electrical equipment failure. The alarm request is the same as the No. 1 PLC station.

5 Conclusion

The third water plant in Huanggang City was put into operation in 1999. The practice of production and operation for more than 10 years shows that the use of automatic control has enhanced the rational operation of various production links, reduced energy consumption, reduced drug consumption and reduced production costs. The water plant automatic control system is running well and the effluent water quality has reached the national standard.

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