Introduction to Shanghai Innovation Constant Pressure Variable Frequency Water Supply Equipment / Secondary Water Supply Equipment / Non-negative Pressure Water Supply Equipment

The water supply system is an indispensable and crucial part of national production and daily life. Traditional water supply methods occupy a large area, are prone to water pollution, require substantial infrastructure investment, and most importantly, cannot maintain constant water pressure, causing some equipment to malfunction. Variable frequency speed control technology is a new and mature AC motor stepless speed regulation technology. It is widely used in speed control fields, especially in the water supply industry, due to its unique and excellent control performance. Because of the special requirements for safety production and water supply quality, there are strict demands for constant pressure water supply, leading to deeper application of variable frequency speed control technology. The actual pressure of the pipeline network is fed back and compared with the set pressure. When the pipeline network pressure is insufficient, the frequency converter increases the output frequency, the water pump speed accelerates, the water supply volume increases, forcing the pipeline network pressure to rise. Conversely, the water pump speed slows down, the water supply volume decreases, and the pipeline network pressure drops, maintaining constant pressure water supply.

Constant pressure water supply can achieve the following functions in pump station water supply:

(1) Maintain constant water pressure

(2) The control system can operate manually/automatically

(3) Automatic switching operation of multiple pumps

(4) System sleep and wake-up: when water usage stops externally, the system enters sleep mode and automatically wakes up when there is a demand for water

(5) Online adjustment of PID parameters

(6) Pump group and circuit protection detection alarm, signal display, etc.

Advantages of the constant pressure water supply system:

The constant pressure water supply system uses pressure sensors, PLC, and Swiss ABB frequency converters as the central control devices to achieve the required functions. Source: Power Transmission and Distribution Equipment Network. The pressure sensor installed on the main pipeline of the network is used to detect the water pressure of the pipeline network, converting the pressure into a 4～20 mA current or 0~10V voltage signal, which is provided to the Swiss ABB frequency converter. The Swiss ABB frequency converter is a control device for the water pump motor, capable of supplying a 0～50 Hz frequency signal to the water pump motor according to the constant pressure requirement, adjusting its speed. The Swiss ABB frequency converter is powerful, with pre-programmed parameter sets that minimize the number of parameters that need to be set during use. The default values of the parameters vary depending on the application macro selected. Shanghai Innovation's constant pressure water supply system uses the PID control application macro for closed-loop control. The Swiss ABB frequency converter, based on the voltage set value corresponding to constant pressure and the feedback current signal from the pressure sensor, uses the PID control macro to automatically adjust and change the frequency output value to regulate the speed of the controlled water pump motor, ensuring the constant pressure requirement of the pipeline network.

Compared with other water supply methods, the variable frequency constant pressure water supply system not only has significant energy-saving effects but also the following obvious advantages:

1. Constant pressure water supply technology uses a frequency converter to change the motor power frequency, thereby adjusting the water pump speed and changing the water pump outlet pressure. Compared to methods that control the water pump outlet pressure by adjusting valves, it significantly reduces pipeline resistance and minimizes throttling losses.

2. Since the variable pump operates under variable frequency conditions, when its outlet flow is less than the rated flow, the pump speed decreases, reducing bearing wear and heat, and extending the mechanical life of the pump and motor.

3. The water pump motor adopts a soft start method, accelerating according to the set acceleration time, avoiding current impact during motor startup that affects grid voltage fluctuations, and also preventing sudden acceleration of the motor from causing surge in the pump system. It completely eliminates water hammer phenomena.

4. It achieves constant pressure automatic control, eliminating the need for frequent operation by personnel, reducing labor intensity, and saving manpower.