Pneumatic Actuator Ball valve overview

A Pneumatic Actuated ball valve is a quarter-turn valve that controls the flow of a media by having a hollow rotating ball.

When the hollow portion of the ball is in line with the flow (pipe or hose), the valve is open and the media can flow through. The valve closes when the solid portion of the ball is in line with the flow, which is done with a 90-degree rotation (hence the name quarter-turn valve) of the ball.

It is also possible to position the valve between fully open and fully closed, which allows you to regulate the flow more precisely. Typical ball valves have two ports, one for an inlet and one for an outlet. However, three ports (L or T) are also available, and depending on how the valve is assembled and installed will determine how the 90-degree rotation of the ball directs the media flow. Four-port ball valves are possible but rare.

Ball valves have a valve stem, which is attached to the ball and controls its rotation.

Actuator overview

A valve actuator is a device that is used to remotely control a valve. If it controls a quarter-turn valve, the actuator is known as a quarter-turn actuator. Instead of a manual lever, you can mount an actuator on the valve to automatically and/or remotely control it. Actuators use a power source to generate the torque that is required to operate (rotate) a ball valve. For most actuators, the power source is either pneumatic, electric, or hydraulic.

Pneumatic actuators

Pneumatic actuators control ball valves by the conversion of compressed air energy to mechanical motion. A rotary mechanical motion is required in a ball valve for a 90 degrees turn. Pneumatic actuator ball valves can be single-acting or double-acting. A single-acting pneumatic actuator uses a single compressed air input to turn the valve and a spring to return the valve to the normal position. A double-acting pneumatic actuator has two compressed air inputs to turn the valve and return the valve to the original position.

Operating principle of Pneumatic Actuated Ball Valve

The most common mechanism for a pneumatic actuator for ball valves is the rack and pinion mechanism. This comprises of the rack (a linear gear) and the pinion (a circular gear). The rack is attached to a piston which is pushed by compressed air to achieve linear motion. This linear motion is converted to circular motion by the pinion. The pinion drives the stem of a ball valve to open and close positions.

To control the pneumatic actuator for ball valves, the compressed air is regulated by solenoid valves. Electrical signals from the controller energize the solenoid valve to either open or close positions allowing compressed air to flow through to both piston sides of the pneumatic actuator. The piston pushes the rack which turns the pinion connected to the stem of the ball valve.