What is the difference between single acting and double acting

What is the difference between single acting and double acting

There are kinds of penuematic actuator for sanitary valves,such as stainless steel actuator(vertical type).Aluminum actuator and Electric actuator(honrizontal type).All these actuators have single acting and double acting.

Double action cylinder drives the valve shaft by air.Put air in,the valve opens.Put air in again,the valve closes.When air out,the valve's open/close postion will stop in place.

Sinlge acting actuator has a inside spring. The open is controled by air.but close is by spring-return.There are two different models.

Normally Open(NO): air in-CLOSE.Air out-OPEN

Normally Closed(NC): air in-OPEN.Air out-CLOSE

As there is a spring inside of single acting actutor.So single acting actuator is a bit more expensive than double acting actutor.

How to tell a valve is a single actuated or double actuated?

If the valve with double acting actautor,when the valve goes wrong.the valve disc is at any postion.

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