Electric Valves Manufacturers

Electric valves are simply electric actuators Control the valve to open and close the valve. It can be divided into upper and lower parts. The upper part is an electric actuator and the lower part is a valve. Electric valves are usually composed of electric actuators and valves. The electric valve uses electric energy as powElectric valve is the use of electric actuator to control the valve, so as to realize the opening and closing of the valve, such as electric ball valveer to drive the valve through the electric actuator to realize the opening and closing action of the valve. So as to achieve the purpose of switching the pipe medium. The voltage of the electric valve can be determined by the customer. The configuration can be equipped with a regulating electric actuator with analog signal, a module with 485 communication port, or even an electric valve actuator for diving.

Electric valve: it is used for analog adjustment of medium flow of liquid, gas and air system, and is controlled by AO. Electric valves can also be used as two position switch control in the control of large valves and air systems.

The electric device of the electric valve is one of the devices used to operate the valve and connected to the valve. The device is driven by electric power, and its movement process can be controlled by stroke, torque or axial thrust. The working characteristics and utilization rate of the valve electric device depend on the type of valve, the working specification of the device and the position of the valve on the pipeline or equipment. Therefore, master the correct selection of valve electric device; It is very important to prevent overload (working torque is higher than control torque).

The correct selection of electric devices shall be based on:

1. Operating torque: the operating torque is the most important parameter for selecting the valve electric device. The output torque of the electric device shall be 1.2-1.5 times of the maximum operating torque of the valve.

2. Operating thrust: there are two main structures of valve electric device. One is not equipped with thrust disc, and the torque is directly output at this time; The other is equipped with a thrust disc. At this time, the output torque is converted into the output thrust through the valve rod nut in the thrust disc.

3. Number of turns of output shaft: the number of turns of the output shaft of the valve electric device is related to the nominal diameter of the valve, the pitch of the valve stem and the number of thread heads, and is calculated as M = H / ZS (where: m is the total number of turns that the electric device should meet; h is the opening height of the valve, mm; s is the pitch of the valve stem drive thread, mm; Z is the number of thread heads of the valve stem.)

4. Valve stem diameter: for multi rotation rising stem valves, if the maximum valve stem diameter allowed by the electric device cannot pass through the valve stem of the matched valve, the electric valve cannot be assembled. Therefore, the inner diameter of the hollow output shaft of the electric device must be greater than the outer diameter of the stem of the rising stem valve. For Non rising stem valves in partial rotary valves and multi rotary valves, although the passage of valve stem diameter is not considered, the size of valve stem diameter and keyway shall also be fully considered in the selection and matching, so as to ensure normal operation after assembly.

5. Output speed: the opening and closing speed of the valve is fast, and water hammer is easy to occur. Therefore, proper opening and closing speed shall be selected according to different service conditions.

6. Installation and connection mode: the installation mode of electric device includes vertical installation, horizontal installation and floor installation; Connection mode: thrust disc; The valve rod passes through (rising stem multi rotation valve); Multi rotation of concealed rod; No thrust disc; The valve stem does not pass; Part of the rotary electric device has a wide range of applications, and is an indispensable equipment to realize valve program control, automatic control and remote control. It is mainly used in closed-circuit valves. However, the special requirements of the valve electric device must not be ignored – it must be able to limit the torque or axial force. Usually, the valve electric device uses a torque limiting coupling.

After the specification of the electric device is determined, its control torque is also determined. When it operates within a predetermined time, the motor will not be overloaded. However, it can be overloaded if:

1. The power supply voltage is low, and the required torque cannot be obtained, so that the motor stops rotating.

2. The torque limiting mechanism is wrongly set so that it is greater than the stopping torque, which causes continuous excessive torque and stops the motor.

3. The heat generated by intermittent use like inching is accumulated and exceeds the allowable temperature rise of the motor.

4. For some reason, the circuit of torque limiting mechanism fails, resulting in excessive torque.

5. The operating ambient temperature is too high, which will reduce the thermal capacity of the motor.

The above are some reasons for overload. The motor overheating caused by these reasons should be considered in advance and measures should be taken to prevent overheating.

In the past, fuse, overcurrent relay, thermal relay and thermostat were used to protect the motor. However, these methods have their own advantages and disadvantages. There is no absolutely reliable protection method for the variable load equipment such as electric device. Therefore, various methods must be combined. However, due to the different load conditions of each electric device, it is difficult to propose a unified method. However, in summarizing most cases, we can also find common ground.

The overload protection methods adopted are summarized into two types:

1. Judge the increase or decrease of motor input current;

2. Judge the heating of the motor itself.

In either of the above two methods, the time allowance given by the thermal capacity of the motor shall be considered. It is difficult to make it consistent with the heat capacity characteristics of the motor in a single way. Therefore, it is necessary to select a method that can act reliably according to the cause of overload – combined composite mode to achieve comprehensive overload protection.

For the motor of rotoc electric device, a thermostat with the same insulation level as the motor is embedded in the winding. When the rated temperature is reached, the motor control circuit will be cut off. The thermal capacity of the thermostat itself is small, and its time limited characteristic is determined by the thermal capacity characteristic of the motor, so this is a reliable method.

Basic protection methods for overload

1. Thermostat is used for overload protection of continuous operation or inching operation of motor;

2. Thermal relay is used for protection of motor locked rotor;

3. Fuse or overcurrent relay shall be used for short-circuit accident.

The correct selection of valve electric device is closely related to the prevention of overload and should be paid attention to.