Why Does the Electric Actuator Always Display the Torque?

For 90-degree turning valves (rotary valves), such as motorized electric ball valves, butterfly pump valves, spherical plug valves, it is best to obtain the corresponding valve torque from the valve manufacturer. Most valve manufacturers test the operating torque required by the valve at the rated pressure, and they provide this torque to their customers.

 

The situation is different for multi turn electric valves. These valves must measure the diameter of the stem. The size of the valve stem connection thread has determined the specifications of the motorised valve actuator.

 

When the specifications of the keystone electric actuator are determined, the control torque is also determined. When it runs within a predetermined time, the motor is generally not overloaded. However, it can be overloaded if the following conditions occur:

 

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

 

The torque limiting mechanism is set by mistake to make it larger than the stopping torque, which causes the continuous production of excessive torque, which in turn stops the motor from rotating.

 

It is used intermittently like jog, the heat generated accumulates and exceeds the allowable temperature rise of the motor.

 

For some reason, the circuit of the torque limiter mechanism fails, which makes the torque too large.

 

The use of the environment temperature is too high, relatively reducing the thermal capacity of the motor.

 

The above are some of the 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, the method of protecting the electric linear valve actuator motor was to use fuses, overcurrent relays, thermal relays, thermostats, etc., but these methods also have their own advantages and disadvantages. For equipment with variable loads such as electric devices, there is no absolutely reliable protection method. Therefore, a combination of various methods must be adopted. However, due to the different load conditions of each limitorque electric actuator, it is difficult to propose a unified approach. But generalizing most situations, you can also find common ground.

 

The overload protection methods adopted can be summarized into two types. One is to judge the increase or decrease of the input current of the electric actuator motor, and the other is to judge the heating of the motor itself. Regardless of the above two methods, the time margin given by the motor thermal capacity must be considered. It is difficult to make it consistent with the thermal capacity characteristics of the motor in a single way. Therefore, it is necessary to choose a method that can reliably operate according to the cause of the overload, that is, the combined compound method, to achieve a comprehensive overload protection effect.

 

There are three basic protection methods for explosion proof electric actuator overload. One is to use a thermostat for overload protection of the motor in continuous operation or inching operation. The second is to use thermal relays to protect the motor from stalling. The third is to use fuses or overcurrent relays for short-circuit accidents.