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The choose and buy of electric valve device and pay attention to the problem
Source: | Author:zhongdeen | Publish time: 2016-01-04 | 1472 Views | Share:
Valve electric actuator is SPC, control valve and remote control of the indispensable equipment, its movement process can by travel, torque, or to control the size of the axial thrust. Due to the working characteristic of valve electric device and work efficiency depends on the type of valve, the device specification and the position of the valve in the pipeline or equipment, therefore, the correct selection of valve electric device, to prevent overload phenomenon (work torque is higher than the control torque) is very important.

Usually, the basis of correct selection of the valve electric actuator are as follows:

Operating torque: operating torque is the most main parameter selection of valve electric actuator, electric actuator output torque should be valve operation maximum moment of 1.2 ~ 1.5 times.

Operating thrust: the host structure of valve electric device has two kinds: one kind is not configured thrust plate, direct output torque; The other is a configuration thrust plate, the output torque by thrust plate stem nut into output thrust.

Output shaft rotation circle count: the number of laps valve electric actuator output shaft rotation with nominal diameter of the valve, the valve stem thread pitch, thread, according to M = H/ZS calculation (M for electric devices should satisfy the total number of rotating ring, H is height of valve opens, S for stem drive screw pitch, Z for the stem thread).

Stem diameter: for multi-turn rising stem valves, if electric device allows the largest stem diameter can't through the stem of the valve, cannot assemble into electric valve. As a result, the inner diameter of the hollow output shaft electric actuator must be greater than rising stem valves stem diameter. In parts of rotary valve and multi-turn valves non-rising stem valves, although need not consider stem diameter through the problem, but also should fully consider when selecting the valve stem diameter and the size of the keyway, after assembly to work properly.

Output speed: if the valve opening and closing speed too fast, easy to produce water hammer. Therefore, should be used according to different conditions, choosing the proper opening and closing speed. Valve electric device has its own special requirements that must be able to limit torque and axial force. Valve electric device adopts usually limiting torque shafts. When the electric actuator specifications was determined, the control torque is determined. Generally run in a predetermined time, the motor will not overload. But as the following conditions may lead to overload: one is the low voltage power supply and can not get the required torque, the motor stop running; 2 it is wrong to set torque limit, make its torque is greater than the stop, cause continuously produce too large torque, the motor stop running; 3 it is intermittent use, the heat generated by the savings, more than the allowed temperature of the motor to appreciate; Four is a torque limit institutions circuit for some reason fails, the torque is too large; Five is the use of the environment temperature is too high, the relatively decreased motor heat capacity.

In the past for motor protection method is to use a fuse, overcurrent relay, thermal relay, thermostat, etc., but these methods all have advantages and disadvantages. For this kind of variable load equipment, electric device is not absolutely reliable measures for the protection of. So we must take various combinations, induces has two kinds: one is the increase or decrease of the motor input current judgment; The second is the motor itself heating situations. These two approaches, both the heat capacity of the given time allowance to consider motor.

Usually, on the basis of the overload protection method is: continuous operation of motor or inching operation over load protection, using a thermostat; The protection of motor blocked, the thermal relay; For short circuit accident, adopt the fuse or over-current relay.
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