Water Hammer Protection Features and Application of Multipurpose Pump Control Valve

[Abstract] Water hammer damage is very destructive, so water hammer protection is the key factor in the normal operation of the pumping station. Introduced the multifunctional pump control valve against water hammer principle, according to the actual conditions described multifunctional pump control valve work process and debugging points. [Key words] Water Hammer Multifunctional Pump Control Valve Pumping Station Water Supply Pipe Water hammer control is an important part of the design of water supply pipe system. The formation of the water hammer is related to the rapid closing / opening of the valve. Due to the difference between the valve closing / opening time Ts and the water hammer wave length T, there are two forms of direct water hammer and indirect water hammer. When TsT, during the valve closing process, the reflected negative water hammer wave arrives at the valve, the valve has not been fully closed, negative pressure water hammer caused the pressure increase has been interfered with (ie reduced), the water hammer peak is reduced, the water Hammer is called an indirect water hammer. Under the same conditions, the direct water hammer is more harmful than the indirect water hammer, and the hardest one is to break the water flow to close the water hammer. First, the theoretical calculation of water hammer pressure value Water supply system shut-off valve water hammer pressure peak P is the pump steady-state working lift P1 and the valve water hammer pressure value △ P superposition value namely: P = P1 + △ P (1) 1.1 Close direct water hammer pressure increase △ P According to the RKS formula, you can calculate the water supply system occurs when the valve closing the direct water hammer pressure increase △ P: (2) where △ P - off valve direct water hammer Υo - Average flow rate in pipe before water hammer, m / s; υ - Average flow velocity in pipe resulting from water hammer in m / s; γ - Water weight, whichever is 9.8KN / m3g - Gravitational acceleration, m / s2; C - Wave velocity of water hammer wave, m / s (3) Where Co is the velocity of sound in a boundaryless liquid medium with density ρ and elastic modulus K, Co =, for water, Co = 1425m / s; K - elastic modulus of water, take 2.04 × N / C ?; D-- diameter of the water supply pipe, mm; δ-- wall thickness of the water supply pipe, mm From equation (2), it can be seen that when the pipe material and the medium it delivers are determined, the pressure increase ΔP of the direct water hammer mainly increases with the increase of the flow rate υo Large and increase, so in engineering design can be properly reduced flow rate υo, increase the diameter of the pipe to reduce the harm of water hammer. 1.2 close the valve indirectly water hammer pressure value △ P "close the indirect water hammer pressure value is more complicated [2 ~ 3], can be approximated by (4): △ P" = T / Ts • △ P When indirect water hammer occurs, Ts> T, we know from the formula (4) that △ P "<△ P, that is, the indirect water hammer under the same conditions is smaller than the water hammer pressure peak of the direct water hammer.When Ts and T are determined, (4) can approximate the calculation of indirect water hammer pressure increase in the actual selection of pump multi-function valve, when the diameter is greater than 800mm, the general Ts = (1.3 ~ 1.5) T, and not more than 2. OT is appropriate. When the pipe diameter is small, the pipe is not long, Ts can be appropriately increased, Ts can be 2 to 10 times the T, the actual water hammer pressure limited to a safe range.Through regulating valve opening and closing action time (3 ~ 120s), so that the calculation of water hammer pressure peak is less than 1.5 times the pump working pressure.This point is different from the liquid controlled slow closing valve, liquid controlled slow closing valve is achieved by fast off, slow off the two stages in the fast off phase, the closing angle Large, about 60% to 80%, while the time is very short, 1--2s; in the slow stage, the closing angle is small. If the closing time is too long, it is easy to cause a large amount of backflow of water in the pressure pipeline, causing the water pump reverse rotation speed to exceed the allowable value, or causing the water column in the pressure pipeline to be rapidly pulled off, causing vacuum in some pipe sections and even cutting off the water hammer. Second, the multi-function water pump control valve water hammer control process Multi-function pump control valve is a new type of hydraulic control valve, a valve can replace the current water pump on the electric butterfly (valve), check valve and water hammer Canceller and can automatically achieve the slow open when the pump (quasi-soft start), stop the pump when the fast closing / slow closing, basically can achieve the current function of slow closing valve hydraulic control, that is, two-stage shutdown process, effectively Prevent the occurrence of water hammer accidents, and it does not have any electrically controlled power or external hydraulic system in the body design also uses a wide valve body streamlined design, effectively reducing the water flow resistance. Multifunctional water pump control valve water hammer protection Process: Before starting the pump, the pressure at the outlet of the valve acts on the main valve plate, the main valve plate is in the closed position, meanwhile the upper chamber of diaphragm controller is connected with pressure water, the lower chamber is connected with The inlet of the valve is connected to the low pressure.After the pump is started, the inlet pressure of the valve is gradually increased, meanwhile, the pressure water slowly enters the lower chamber of the diaphragm controller through the connection line of the inlet of the valve to realize the slow opening of the main valve plate, and the opening speed can be controlled by the control valve When the pump (accident) down, the valve inlet pressure decreases (see Figure 1), when near zero flow, the main valve plate under its own gravity quickly closed due to the valve inlet pressure is reduced (the valve outlet pressure water through The connecting pipe enters the upper chamber of the diaphragm controller), the lower chamber water is pressed back to the valve inlet through the connecting pipe at the inlet of the valve, the slowly closing valve plate is slowly closed, and the slow closing time can be adjusted by the control valve. And slowly closing valve plate in line with the closure of the water supply system closed two-stage rule, it can effectively reduce the water hammer pressure peak.Accessories design: micro check valve is to ensure that the valve opening time is greater than the motor start-up time, the motor light load Start; valve opening time pressure conditions can be set according to the scene. The control valve can adjust the water flow speed between the upper and lower chambers of the diaphragm controller so as to adjust the slow closing time. The valve can also be manually operated during the normal operation of the water pump to open and close the valve. The filter is to ensure the cleanliness of the water in the upper and lower chambers of the diaphragm controller. The opening of the main valve plate of the multifunctional pump control valve is determined by the impact force of the water flow in the pipe. When the flow velocity is high, the opening degree of the main valve plate is large, and the valve plate opening degree is small when the flow velocity is reduced; when the flow velocity approaches zero, shut down. The whole process is consistent with the two-stage closing principle of eliminating water hammer, so removing the water hammer works well. Multifunctional pump control valve slow closing valve plate is closed in the diaphragm controller after the pressure difference between the lower chamber to achieve, that is, after the main valve plate is closed, the slow closing valve plate can only be closed, so there will be no slow closing and Speed ​​closed synchronization phenomenon.