Using PLC and InTouch to realize double valve automatic control in waterworks
**Abstract:** This paper presents the implementation of SLC500 and InTouch to achieve full automatic control of the four-company dual-valve filter system at Hangzhou Waterworks. The study focuses on the features of the dual-valve filter, the process flow, the structure of the control system, program architecture, and the realization of control functions through InTouch. It details the successful transformation of a 30,000-ton dual-valve (six-valve) filter system using Rockwell’s SLC500 products, along with the networking control of two sets of filters. Two main challenges were encountered: first, achieving centralized control of four filters within a single PLC, which required careful planning of the program structure; second, ensuring stable communication between the host computer and the 30,000-ton filter system, avoiding issues such as read/write interrupts or data loss.
The dual-valve filter operates in three stages: backwashing, finishing, and normal filtration with PID regulation. A key challenge is determining the siphon condition, which is crucial for automation. Instead of relying on pressure transmitters or contact switches, the system uses relative changes in water level to detect siphon formation, proving effective in practice.
The control system includes two parts: one for the 40,000-ton filter with six units and another for the 30,000-ton filter with four units. Each filter has its own PLC, except for the shared backwash tower, which uses a common PLC. Communication is via DH485 industrial LAN for the 40,000-ton system and KTX cards for the 30,000-ton system. The water level is monitored using E+H ultrasonic sensors, and PID control adjusts the valve based on measured levels.
The program structure consists of a main program and subroutines for each filter, allowing for easy debugging and maintenance. The system also supports manual, local, and automatic control modes, with options for forced backwashing. The InTouch software provides real-time monitoring, alarm logging, and parameter adjustment, enhancing operational efficiency.
In conclusion, the system successfully maintains water levels within ±3 cm, achieves automatic filtration, and ensures smooth operation of multiple filters. The design meets production requirements and improves the company's technical capabilities. The use of domestic valves combined with SLC500 and InTouch demonstrates an efficient and reliable solution for automated water treatment systems.
**Keywords:** SLC500, InTouch, dual-valve filter, PID control, automation, water treatment, PLC, communication protocol, real-time monitoring.
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