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The Principle of Handwheel operation

Source:http://www.flowxgroup.com/Update Time:2014-04-22Hits:

Handwheel operation is to control the valves or electric actuators through the handles. It is one of the most common ways to handle the valves. It is widely believed that handwheel operation should be in complying with the hydrodynamic properties, that is, the flow resistance should be smaller. Under this condition, Handwheel operation will reduce the noise and cavitations because it can control the flow accurately. This is very meaningful, for with this advantage the flow control could be repeated within a wide range.

The hand wheel for handwheel operation usually emply the double eccentric gear design. The first eccentric gear enforces the rotation axis to be estranged to sealed plane. There is a complete seal between the valve disc and seat when handwheel operation is applied, which makes the valve stem seals have no way to leak. When it is in the close position, the entire sealed ring would be pressed evenly; when it is in the open position, the entire rings are not under pressure at all. There is no permanent indentation exist on the rubber sealing ring. The second eccentric gear is that the eccentric shaft center axis is deviated from the valve centerline, so you can quickly release the pressure of the valve stem sealing parts to reduce the abrasions. What you need to do is just turn the valve disk to an small angle, so that you could take it off from the valve seat.

The pneumatic actuators , on which the handwheel operation is applied, possess a device which could adjust torque or a limit travel switch. The limit travel switch is very flexible when you start the handwheel operation. When the valve hand wheel is in full open position or in a full close position, and at the same time there is an obstacle on the pros and cons of the transmission direction, the limit travel switch could cut two secondary control circuit powers of the pneumatic actuators. In the processing of handwheel operation, the torque switch must be installed by the manufacturer, and still, it should meet the calculated value of the maximum operating torque.

The handwheel operation should be implemented nimbly. To put it in another way, the handwheel should be made in accordance with human body engineering principle. The length of the hand wheel should be less than 320mm for single operation. If it needs two people to do the handwheel operation, the length of the hand wheel should be within 0.5m.

The quality of the hand wheel is very important for handwheel operation. If you get a poor quality hand wheel, not only that you will not implement the handwheel operation fully wheel, but the whole system will be affected. So, buy your pneumatic actuators from a seller who enjoys a long time good reputation, and you will have a better experience when you begin the handwheel operation.

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