Working Principle and Applications of Multi-functional Water Pump Control Valves

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Working principle and applications of multi-functional water pump control valves: In feed water pumping stations, in order to enable centrifugal pumps to start under light load, it is usual to first close the pump’s outlet valve before starting the pump unit; once its speed reaches the rated value, the outlet valve is then gradually opened； To prevent backflow of the medium in the system, a check valve must also be installed at the pump outlet ； Since the instantaneous closure of ordinary swing check valves often causes water hammer incidents that threaten pump systems, an effective water hammer suppression device must also be installed. Currently, electric butterfly (gate) valves are often used in combination with micro-resistance slow-closing check valves to achieve the above objective. However, in practical use, electric butterfly (gate) valves frequently suffer from problems such as incomplete closure, motor burnout, and damage to the gear reduction mechanism. Micro-resistance slow-closing check valves have a narrow range of applicability; they cannot handle large variations in flow rate and pressure. Moreover, their control needle valves tend to get clogged, which prevents the damper from functioning properly, thus affecting the reliable and safe supply of water. I. Introduction to the Multifunctional Pump Control Valve: The multifunctional pump control valve is a new type of hydraulic control valve; one such valve can replace three different devices – electric butterfly (gate) valves, check valves, and water hammer arresters. It can automatically achieve a slow start when the pump is started, as well as a rapid and slow shutdown when the pump is stopped, without any electrical control or other forms of power or manual intervention, nor is a hydraulic system required. Main advantages of the multi-functional water pump control valve: (1) No operation control is required. It uses the pressure difference of water before and after the valve when the water pump starts or stops as the control power, enabling it to open and close automatically in response to the pump’s operation. (2) The opening and closing process of the valve can effectively prevent accidents caused by the rise in water hammer pressure waves. According to on-site usage surveys and actual measurements, the peak pressure of water hammer when the pump is stopped remains within 1.3 times the operating pressure. (3) No on-site calibration is required, and it has a wide range of applicable operating conditions. (4) Practically no maintenance required. With one valve replacing three, the amount of maintenance work is **reduced**. (5) Low resistance loss. With its streamlined and wide valve body design, the resistance loss is reduced by more than 50% compared to similar foreign products. For example, at an economic flow rate of v=2 m/s for the DN200 model, the loss of this multi-functional pump control valve is 0.7 m, whereas that of similar foreign products is 1.5 m. II. Structure and Working Principle of the Multi-functional Water Pump Control Valve 1. Structure: The structure of the multi-functional water pump control valve consists of the main valve and external accessories. The main valve consists of a valve body, a main valve plate, a slow-closing valve plate, a valve stem, valve seats, and a diaphragm controller (including a valve cover, diaphragm seat, diaphragm, and diaphragm pressing plate); the external accessories include a control valve, a filter, an exhaust valve, and a check valve. Among them, the micro check valve is a specially designed component, equipped with flow-limiting holes in its check direction. Refer to Figure 2 for the installation method. 2. Working principle: 1) Before the water pump starts, the pressure at the outlet of the valve acts on the main valve plate, keeping the valve in a closed position. Meanwhile, the upper chamber of the diaphragm controller is connected to the pressurized water, while the lower chamber is connected to the low pressure at the valve inlet. 2) After the water pump starts operating, the pressure at the valve inlet gradually increases; simultaneously, pressurized water enters the lower chamber of the diaphragm controller through the connection pipe at the valve inlet, thereby causing the main valve plate to open slowly. The opening speed can be adjusted using a control valve. 3) When the water pump stops, the pressure at the valve inlet decreases; as the flow rate approaches zero, the main valve plate closes rapidly due to its own gravity. As the pressure at the inlet side of the valve decreases, the pressurized water at the outlet side of the valve enters the upper chamber of the diaphragm controller through the connecting pipe, while the water in the lower chamber is pushed back to the inlet side of the valve via the connecting pipe there, causing the valve plate to close slowly. The time taken for this slow closure can be adjusted using a control valve. The rapid closing of the main valve plate and the gradual closing of the slow-closing valve plate follow a two-stage closing pattern, which enables effective elimination of water hammer. III. Application of multi-functional water pump control valves in safe water supply: (Several technical issues) 1. Design of components in the connection pipes: 1) The function of the micro-check valve is to ensure that the valve remains open for a longer period than the time it takes for the motor to start, thereby allowing the motor to start under light load ； At the same time, avoid pump start-up water hammer caused by too fast valve opening speed. The valve opening time can be set by the control valve based on the pressure conditions at the site. 2) The control valve can adjust the water flow rate in the upper and lower chambers of the diaphragm controller, thereby regulating the slow-closing time ； The diaphragm controller can be serviced when it is turned off ； The valve can also be manually operated to open and close while the water pump is running normally. 3) The filter ensures the cleanliness of the water in the upper and lower chambers of the diaphragm controller. Since the water flow moves back and forth during the opening process of the valve, which provides a self-cleaning effect, it can also be used in conditions with poor fluid quality. 2. Valve characteristics for eliminating water hammer: 1) Based on the principles behind the formation of destructive water hammer, there are two main factors for reducing the pressure rise caused by water hammer: (1) Closing the main valve gate when the flow velocity v just before cutoff is as low as possible (approaching zero) ； (2) The time required to close the valve is t, which is given by the water hammer phase u = 2L/α (where α is the speed of propagation of pressure waves, in m/s) ； L--the length of the pipe in meters), multiplied by 5-10, can keep the actual water hammer pressure h within a safe range, thereby eliminating the destructive effects of water hammer. 2) The degree of opening of the main valve plate of the multi-functional water pump control valve is determined by the force exerted by the water flow in the pipeline; when the flow velocity is high, the main valve plate opens more widely; as the flow velocity decreases, the degree of opening of the valve plate decreases; and when the flow velocity approaches zero, the main valve plate closes. The entire process is in line with the quick-closing principle for eliminating water hammer, thus achieving a very good effect in removing water hammer. 3) The closing of the slow-closing valve plate of the multi-functional water pump control valve can only occur after a pressure difference is established between the upper and lower chambers of the diaphragm controller; that is, the main valve plate must close first before the slow-closing valve plate can close. As a result, it is not possible for slow closing and rapid closing to occur simultaneously. 3. Resistance characteristics of the valve: To reduce water flow resistance, the weight of the main valve plate was reduced in the design, and a streamlined and spacious valve body design was adopted. According to tests conducted by the Hunan Province Hydromechanical Quality Supervision Authorized Station, the resistance coefficient of the DN200 multi-functional pump control valve is approximately 3.8, whereas the resistance coefficient of the swing check valve used in pipes of the same specification is 5.5. 4. Diaphragm design: The quality of the diaphragm is a key component that directly affects the performance and service life of the valve. After various evaluations, neoprene was chosen as the raw material, with a nylon fiber mesh used for reinforcement in the middle ； As tested by the Hunan Rubber Quality Supervision Authorized Station, it does not crack after 650,000 cycles of fatigue bending, and can be used for over 10 years. 5. Maintenance: Without any additional hydraulic or electric components, it requires little maintenance. Moreover, the wide valve cover allows all internal components of the valve to be removed, facilitating maintenance. III. Conclusion: As proven through actual use, the multi-functional pump control valve is capable of effectively eliminating destructive water hammer. It offers significant advantages in enhancing the safety and reliability of water supply systems. It is easy to adjust and install, simple to operate and manage, and requires minimal maintenance. It meets the requirements outlined in the \"2000 Development Plan for Technical Progress in the Urban Water Supply Industry\" regarding the automation, mechanization, and modernization of water supply equipment; it represents a new type of valve product suitable for upgrading pump stations.