Automatic system of the hottest water supply and p

Water is the source of life, and human life and production are inseparable from water for a moment. Therefore, how to make the water supply work safe, reliable, high-quality and efficient is a major event that people are increasingly concerned about. The automatic water supply control system centered on frequency converter and programmable controller developed by Harbin Yalian Electrical Technology Co., Ltd. is a series of products, which can comprehensively meet the monitoring, control and management functions of water supply system under various water supply modes and various use requirements. The purpose is:

1. Improving the reliability of the operation of the water supply system is also the product and product upgrading of the combination of computer technology, communication technology and control technology in the field of industrial control, so as to reduce the loss and inconvenience caused by the failure of the water supply system

2. Improve the quality of water supply and the stability of water supply parameters

3. Save energy and manpower, and try to reduce the cost of water supply

I. Basic Control Scheme of water supply system

the water supply system that supplies water to a factory or a building usually has the following schemes

1. The simplest water supply system

two 100% capacity water supply pumps controlled by frequency converter, one for operation and one for standby

the pressure measurement value of the main water supply pipe enters the control cabinet, and compared with the given pressure value, the difference value is controlled by the PID regulator to control the output frequency, so as to keep the pressure of the main water supply pipe consistent with the given pressure value

considering that the packaging materials do not fully meet the environmental protection requirements 24 hours a day, there are several obvious peak periods of water consumption, during which the flow of water is large and the resistance loss along the way is also large. Therefore, the given pressure value can be composed of several broken lines, and the given pressure value is higher during the peak water consumption, which can ensure that the water pressure at the end of the water supply pipeline is also relatively stable

2. Water supply system with multiple water supply pumps

increase the number of water supply pumps in the water supply system, such as 3 water supply pumps with 50% capacity or 5 water supply pumps with 30% capacity. Although the standby capacity is reduced, the full water supply can still be guaranteed in case of a pump failure. The water supply pump of this water supply system can have two operation modes:

(1) one is a variable-speed pump, which changes the speed under the control of the frequency converter to maintain the pressure of the main water supply pipe; Other pumps operate at a constant speed and are controlled by PLC to start or stop

(2) all are variable-speed pumps, which are controlled by the frequency converter to start, stop and change the speed. In the process of gradually increasing the water demand, the frequency converter gradually increases the speed of the controlled water supply pump and increases its output. When the power frequency speed is reached, it will be switched to the power supply line for constant speed operation, and the next water supply pump will be controlled to start and bear the role of maintaining the pressure of the water supply main pipe

in the process of gradually reducing the water demand, PLC or frequency converter will stop the operation of the water supply pump in turn. There are two ways to choose the stopping sequence:

(1) start first, stop first, and then start and stop

(2) start before stop, start after stop

3. The water supply system with dormant pumps

because the water consumption is very small (or only the leakage of the pipeline) from late night to early morning (such as 24-5 o'clock), in order to further reduce energy consumption and equipment consumption when developing new SBC products, a small water supply pump can be set up, during which it can be put into constant speed operation, and the rest of the pumps can be stopped. Of course, if a large amount of water is occasionally needed during this period, resulting in the water pressure falling to a certain value, the FM pump will be started immediately to meet this need

4. The water supply system with fire water system

is based on: (1) whether the water supply pool is shared, (2) whether the pipes are shared. Such an integrated water supply system can have several different operation modes. When a fire alarm signal occurs, the control system composed of PLC frequency converter will start the fire protection system according to the predetermined action procedure to meet the needs of fire fighting

5. Layered water supply system

for high-rise buildings, in order to reduce the defects that the water pressure difference between each floor is too large due to the height difference, it can be divided into several water supply areas according to the height of the floor

the water supply system on each floor has a control device to meet the water supply requirements of each floor. Among them, for example, the lower control device is the main control device, which also receives the relevant signals of the upper layer

as for the selection of the core device of the water supply control system - PLC and frequency converter, since many types of devices are available in the market, they can be selected through consultation with users according to their performance, price, supply channel, use experience and other factors. For simpler water supply systems, a frequency converter with PLC function has recently been launched on the market for use. Figure 4 shows the inverter wiring diagram of one variable frequency pump and six (maximum) power frequency pumps. Figure 5 shows the wiring diagram of the frequency converter of four (maximum) frequency conversion pumps. As the number of devices is reduced, the wiring quantity is reduced, the cost is reduced, and the reliability is also improved

wiring diagram of special frequency converter for water supply with six power frequency pumps and one frequency conversion pump

II. Automatic control and management system for water production

(I) water plant with groundwater as the water source

the basic process flow of this water plant with groundwater as the water source is as follows: the groundwater is pumped out of the water source well with a deep-water pump, sent into the water inlet pool through a pipeline, chlorinated into a kind of high-efficiency thermal insulation plate, entered the clean water pool, and then entered the swabbing well. After adding ammonia internally, the water is sent to the urban pipe with a distribution pump

the main control devices that should be set and their functions are:

1, water source well

each water source well is equipped with a measurement and control cabinet to control the start and stop of the water pump, measure its outlet pressure, flow, power supply voltage, current, consumed electric power, etc. If there is a ventilator, sewage pump and other equipment, it is also necessary to control its start and stop, and measure the relevant parameters. The measurement and control cabinet communicates with the central control room in the plant through 485 port or modem port, sends the measured parameters and equipment operation status to the central control room, and receives and executes the operation instructions of the central control room and the instructions to modify the set value

2. The distribution substation

provides a measurement and control cabinet and an operator station (one industrial computer and one display) for the distribution substation supplying power to each water source well. Control the circuit breaker of each distribution cabinet and measure the voltage, current, active power and reactive power of each power circuit. 485 port or modem port is also used to communicate with the central control room in the plant

3. Chlorination system

the chlorination system that chlorinates into the water inlet tank is equipped with an automatic regulation system

this is a proportional regulation system that roughly adjusts according to the inflow and takes the residual chlorine of the effluent as the correction. Good control effect can be obtained for the regulated object with large delay

4. Water inlet pool

the water level of the water inlet pool needs to be kept within a certain range