Water hammer effect of valve Introduces the reason and solution of overload of valve electric actuator!

Water hammer effect of valve Introduces the reason and solution of overload of valve electric actuator!

“Water hammer Effect” refers to that when the open valve is suddenly closed, due to the inertia of pressure Water flow, Water shock wave will be generated and damage will be produced. This is the “Water hammer effect” in hydrology, also known as the positive Water hammer. On the contrary, after the closed valve is suddenly opened, it will also produce water hammer, called negative water hammer, and there is a certain break
Water Hammer Effect
It refers to when the open valve is suddenly closed, due to the inertia of pressure water flow, the shock wave of water flow will be generated, and the destruction effect will be produced. This is the “water hammer effect” in hydrology, which is the positive water hammer.
On the contrary, after the closed valve is suddenly opened, it will also produce water hammer, called negative water hammer, which also has a certain destructive power, but not as big as the former.
Usually, the closure element is suddenly drawn into the seat as the valve approaches closing, known as the solution cylinder latching effect.
The cylinder latching effect is caused by a low-thrust actuator that does not have enough thrust to remain close to the seat, resulting in a sudden shutdown of the pump or the valve, resulting in a water hammer effect. For control valves, in some cases, fast-opening flow characteristics can also lead to water hammer effect.
Although the water hammer makes a lot of noise, the real damage is caused by mechanical failure. Because of the rapid change from kinetic energy to static line pressure, the water hammer can break through the line or damage the pipe support and damage the line joint. For valves, the water hammer can cause severe vibration through the spool, which can cause failure of the spool, gasket or packing.
For valves, protection against water hammer is to prevent any sudden pressure change in the system.
This includes slowing the closing of the valve itself or providing a greater degree of tension and rigidity as the closing element approaches the seat. To prevent pressure fluctuations, the valve should be closed at a uniform speed. In some cases, when using the fast open feature, you can ask for the equal percentage feature to be changed. For control valves that must be throttled when close to the seat, actuators with sufficient output thrust should be used, such as piston pneumatic actuators or hydraulic actuators, or special notches on the stroke sleeve of manually rotating operators that will reduce or prevent cylinder locking. Some type of anti-wave protection on the piping system can also reduce water hammers. This can be done using a pressure relief valve or buffer barrel. In addition, gas can be injected into the system, which reduces the density of the fluid and provides some compressibility to handle any sudden fluctuations.
Valve electric actuator overload reasons and solutions! Valve electric actuator overload reasons: first, the power supply is low, not the required torque, so that the motor stops rotating; Second, it is wrong to adjust the torque limit mechanism, so that it is greater than the stopped torque, resulting in continuous excessive torque, so that the motor stops rotating; Three is intermittent use, the heat savings, more than the motor allowed
Reasons for overload of valve electric actuator:
First, the power supply is low, not the required torque, so that the motor stops rotating;
Second, it is wrong to adjust the torque limit mechanism, so that it is greater than the stopped torque, resulting in continuous excessive torque, so that the motor stops rotating;
Three is intermittent use, heat savings, more than the allowable temperature rise of the motor;
Fourth, for some reason the torque limiting mechanism circuit failure, so that the torque is too large;
Fifth, the use of ambient temperature is too high, relative to the motor heat capacity decline.
In the past, fuses, overcurrent relays, thermal relays and thermostats have been used to protect motors, but these methods have advantages and disadvantages. There is no safe and reliable way to protect electric equipment with variable load. Therefore, it is necessary to take a variety of combination, summed up in two ways: one is to judge the increase or decrease of the motor input current; The second is to judge the motor itself. These two ways, no matter which way to consider the motor heat capacity given time margin.
In general, the basic protection against overload is:
1. For motor continuous operation or point operation of overload protection, using thermostat;
2. Thermal relay is used for motor blocking protection;
3. For short circuit accident, use fuse or overcurrent relay.
Valve electric actuator is an indispensable equipment to realize valve program control, automatic control and remote control. Its motion process can be controlled by stroke, torque or axial thrust. Correct selection of valve electric device is very important to prevent overload phenomenon (working torque higher than control torque).