Are pneumatic valves generally equipped with a single cylinder or a dual cylinder? What is the difference? ? ? Do they all need solenoid valves and positioners?

Single-cylinder! Solenoids and positioners are required

From a control perspective, there is no difference between single-cylinder and double-cylinder systems. The on/off valve is controlled by a solenoid valve, while the control valve is controlled by a positioner.

It shouldn’t be called single-cylinder or double-cylinder; for angular stroke pneumatic on-off valves, the terms single-acting and double-acting are used； The air source pressure requirements differ for the two methods; single-acting valves are commonly used for small valves, while double-acting valves are typically used for large valves. An electromagnetic valve is used as the on/off valve at the air source, and a valve positioner is used for the control valve.

This post was last edited by cjgj008 on 2017-8-31 at 13:42. Whether to use a single-cylinder or double-cylinder pneumatic valve depends on the actions and functions you want to achieve. Pneumatic valves have various functions, which can be achieved by pairing them with different solenoid valves (2/3 way, 2/5 way, etc.) as well as single or double air tanks. Additionally, single-cylinder and double-cylinder are common terms; the actual names are single-acting and double-acting

There are many single-acting types; the positioner is crucial

The so-called single or double cylinders are the actuators for controlling valves, and there are specific requirements regarding the force with which these actuators need to control the valves. It is specifically set based on the power required for the valve to operate. (Personal opinion, for reference only. ）

So, in what situations is a single-acting type used, and in what situations is a double-acting type used? ?

This post was last edited by Hariky on 2017-9-7 at 18:29. Pneumatic actuators are divided into linear and rotary types, and the main types include spring-diaphragm actuators, spring-return cylinder actuators, dual-cylinder actuators, and multi-cylinder actuators. 1. Spring-diaphragm actuator: It offers high control precision and good dynamic performance. However, the thrust is limited due to the size and material of the diaphragm; therefore, this type of actuator is preferred for control valves. 2. Spring-return cylinder actuator: It is easy to achieve a fail-safe position; its cost is higher than that of a dual-cylinder actuator, and its size is larger than that of a dual-cylinder actuator when the same thrust is required. It can be used in control valves and on-off valves. 3. Dual-cylinder actuator: Fault-safe positioning is achieved through a buffer tank that provides backup power; it offers high thrust at a relatively low cost, and can be used in control valves and on/off valves. Note: When selecting a cylinder actuator, safety considerations dictate that spring-return types are preferred. However, if calculations show that the length of the actuator is too large, such as over 1.8 meters, then dual-acting actuators are usually required. 4. Multi-cylinder actuator: When the required thrust is not very high, its size can be kept small, and it can be used to operate control valves. Note: Both spring-diaphragm actuators and dual-cylinder actuators come in gear-rack and fork-type transmission structures. The gear-rack type is suitable for medium to low thrust, while the fork type is suitable for high thrust. However, the fork-type type has a larger dead zone and lower precision. Multi-cylinder actuators only have the gear and rack type.