Project Description

***The scale of the existing first-stage project of the waterworks is 100,000 m3/d. The scale of this second phase expansion is 100,000 m3/d. The automatic control system is constructed to meet the unattended operation mode, and it can operate normally without uninterrupted operation for no less than 72 hours. The factory's water quality, water pressure, and water volume meet the indicators, and the normal operation of the equipment is stable, reliable, safe, energy-saving, environmentally friendly, and a leading automation system for waterworks. The automatic control system is a comprehensive automation system with intelligent production process control, production information management and storage functions.

System Overview

The control system is integrated by programmable logic controller (PLC), communication network, human-machine interface, measurement and control instrument, video monitoring and peripheral equipment. The system design follows the principles of advancement, practicability, reliability, economy, and openness. It is designed around the guiding ideology of "improving the quality of water supply, improving the safety and reliability of water supply, reducing energy consumption, reducing leakage, and reducing medicine consumption." Using NA400PLC as the core of the control station.

Process flow

System structure and composition

1. Network structure

The control system is composed of the computer in the central control room, the on-site control station, the on-site instruments and the execution mechanism. The network adopts a multi-layer structure, which is divided into management layer, control layer and field equipment layer from top to bottom. According to the characteristics of scattered water plant equipment and more stations, the control station is designed with 6 substations. Among them, the core control station adopts the processor hot standby redundant configuration. Six stations are connected using redundant ring industrial Ethernet. The SCADA system adopts the data structure design of redundant server + client. See the network structure diagram for details.

2. Controller

• Adopt Intel Pentium M processor, main frequency 300MHz, high-performance redundant CPU, high reliability.
• Comes with Ethernet interface, supports Modbus TCP and OPC protocol.
• 32M memory space + 32M storage space.
• Comes with a real-time clock, used to record the current time and time control of the process.
• With Watchdog function, it can automatically reset and restart in case of failure.
• Support hot swap.
• Data power-off protection.

Control function

The system has man-machine interface interface, production process sequence control, equipment interlock protection, optimized life control, automatic adjustment, data statistics, accumulation, analysis and other basic control functions and video monitoring, security functions, office management functions. The following sections introduce the control functions of the process system of the water plant production process.

1. Water pump control function

The water pumping room unit realizes the one-step operation of the unit starting and stopping according to the scheduling instructions, the linkage of the water pump and the valve, the PID adjustment of the frequency conversion motor, the optimal operation of the water pump, the automatic operation of the drainage pump according to the water level, the pump fault protection and alarm, equipment maintenance prompts and other controls function. The collection of raw water quality parameters, through the field bus to the incoming line current, voltage, electric degree, power factor, pump motor current, active power, electric degree collection, etc.

2. Settling tank control function

The main control functions of reaction precipitation include automatic stirring and flocculation of the sedimentation tank. The mud suction machine automatically crawls and controls the mud suction, the pool bottom mud discharge valve automatically discharges mud periodically, and the slave suction station PLC communicates with the master station through wireless AP equipment to achieve linkage.

3. V-shaped filter control function

• The control of the V-shaped filter is the more difficult part in the process control of the water plant. The quality of the control strategy directly affects the effectiveness of the water purification automation process. The main control functions are:
• V-type filter water level adjustment control (outlet valve PID adjustment).
• V-type filter sequence control process control.
• The washing of the filter grid of the filter pool is lined up to coordinate the backwash of the filter grid.
• Equipment and electrical parameter collection, etc.

4. Control function in the dosing room

Dosing control is one of the keys to the water plant process. Directly affect water quality and production safety. In general, its control function has three aspects, including automatic adjustment control of metering pump adding alum, control of alum distribution process of alum (dilution) system, and control of adding function of chlorine adding machine (before and after filtration).

5. Control function of dehydration machine room

The dehydration system in the dehydration machine room is provided with a control PLC to independently complete the monitoring of the dehydration system and PAM filling system in the dehydration system. Access to the control system through communication, the control system gives the dehydrator start and stop signals. In addition, the control system completes the simple control of equipment such as the reuse water pump, sludge pump, and sludge balance tank mixer.

6. Control function of the secondary pump room

The main control of the secondary pump room is similar to that of the water intake pump room. It mainly completes the one-step operation of starting and stopping the unit through the program according to the scheduling instructions, including the linkage of water pumps, valves, vacuum forming devices, and variable pressure PID adjustment of the water supply for set pressure. The collection of factory water quality parameters and the communication interface with the Environmental Protection Bureau, the signals collected by the integrated protection unit on the high and low voltage switchgear, etc.

7. Key highlights

The control system is an automatic control product tailored according to the process of the water plant, which realizes the automatic management and control of the water treatment process. The system has the following prominent functions.

(1) Realization of grand linkage

With the improvement of equipment and the improvement of automatic control technology, the water plant has achieved "small linkage". That is, the system automatically adds functions such as automatic dosing, automatic sludge discharge, automatic filtration, automatic start and stop of the drainage pump, and automatic frequency conversion adjustment of constant pressure. But to realize the full-automatic operation of the whole plant, it is necessary to connect all links and realize the "big linkage" of the whole plant. To achieve "large linkage" needs to solve the problem of dynamic balance between the water supply and water supply of the intake pump. This problem was solved, and the "Grand Linkage" was solved. Through the analysis and research of the process of the water plant, we calculated the output of the water intake pump by using the feed water flow value of the outlet pump and the level value of the water collection well, successfully solved this problem, and realized the whole plant automatic operation of the system.

(2) Motor maintenance reminder

According to the instructions of motor equipment such as water pump and blower, through the analysis of the abnormal state such as the accumulation of the use time of the motor, the abnormal temperature of the motor, and the electrical three-phase unbalance. As far as possible, the maintenance personnel should be notified to carry out inspection and maintenance before the equipment is damaged or before the maintenance period, which saves the maintenance cost and maintenance cost.

(3) Memory of operating parameters

The water outlet pressure of the waterworks often needs to be set according to the operating personnel's experience according to the time period. The outlet pump adjusts the outlet water at a constant pressure according to the set pressure. The control system has a memory function to analyze and refine the operating parameters of the operators. According to the process requirements, the target value of the outlet water pressure in different periods can be automatically determined, avoiding the long and tedious pressure setting.

Functions of the man-machine interface

1. Process flow chart display

Really reflect the production process, the picture is simple and smooth, and the process flow produces a vivid image. The system consists of an overview picture and multiple pictures. Each screen is provided with a traction key related to the screen, which can conveniently browse and control the equipment.

2. Report display and printing function

The system historical data is stored in a standard database format, supporting dBASE VI, ACCESS, ODBC format, etc. The report supports the calculation and processing of data. It not only has basic processing capabilities such as average, maximum, and cumulative values, but also supports the calculation of devices by time zone. The report is flexible and can generate daily, monthly, quarterly, and annual reports according to user requirements.

3. Alarm function

The alarm function reminds the operating personnel to immediately understand the operation status of the equipment related to the alarm parameters, and to handle it when necessary, which is an important measure to ensure continuous and stable operation of production. View the alarm list at any time, and can confirm the single alarm, full screen alarm and all alarms.

4. Real-time trend graph and historical trend graph

Real-time trends can be directly obtained by right-clicking, and multiple trends can be displayed on the unified interface. The historical trend graph collection period is 10 seconds, and N collection points are displayed at the same time in the table, which is convenient for comparative analysis. The historical trend graph supports the function of displaying by system according to time period. The default storage time of the historical database is 2 years, which supports the saving and backup of database files. Powerful historical data automatic and historical event query function.

5. Operation authority management and operation record function

Provide different operation login rights for visiting/browsing personnel, operating personnel, maintenance engineers, etc. It has operation record and operation event record function, and supports powerful data query function, and supports partition and sub-site query function according to time period.

Features

• The system adopts domestic brand PLC products of independent brands.
• The control unit adopts hot standby redundant configuration and high-performance processor.
• For the dosing room, filter tank and other environments, the hardware equipment performs three-proof treatment.
• The product provides a universal standardized communication interface, supports PROFIBUS/HART/MODBUS/OPEN CAN and other common field buses, and has good scalability and openness.
• Adopt Ethernet architecture, high-speed communication and reserve bandwidth.
• Fiber optic self-healing 100M industrial Ethernet self-healing ring network connection, standard TCP/IP protocol.
• Good versatility and user-friendly design.
• According to customer needs, tailor-made products and control procedures to meet the needs of the process.
• Quick after-sales service and strong technical team.