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Normally open and normally closed type and selection of pneumatic or hydraulic actuators 

There are two types of single-acting pneumatic actuators: normally open and normally closed. In which case should the normally open type be used, and in which case should the normally closed type be used? 

Normally open: the valve is opened under the tension of the spring when the air is lost; the valve is closed under the thrust of the compressed air when the air is in. 

Normally closed: the valve is closed under the tension of the spring when the air is lost; the valve is opened under the thrust of the compressed air when the air is in. 

Therefore, when choosing a single-acting actuator, we should select the type according to the actual working conditions. When the air source is lost and an emergency occurs, the single-acting pneumatic actuator can automatically reset to minimize the danger, while the double-acting is generally not easy to reset. 

Single-acting pneumatic actuators are generally divided into normally open and normally closed types.

Normally open: closed when ventilating and open when degassing.

Normally closed type: open when ventilating and close when degassing.

In general, more double-acting cylinders are used, and double-acting cylinders have no springs, so the cost is lower than that of single-acting pneumatic actuators.

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Post time: Jul-08-2022