Introduction to Pneumatic Stop Valve
Pneumatic stop valves are generally fully open and closed. Considering the flow characteristics, the globe valve and ball valve are characterized by short opening and closing stroke, fast speed, reliable sealing, small opening and closing static torque, etc. Therefore, both types of products have been applied. However, considering the reliability, the mainstream product is still the pneumatic stop valve.
The cylinder of the pneumatic stop valve is a finalized product, which can be divided into single acting and double acting. The single acting product has a reset cylindrical spring and an automatic air loss reset function, that is, the cylinder piston (or membrane) drives the cylinder push rod to return to the initial position of the cylinder (the original position of the stroke) under the action of the spring. The double acting cylinder has no return spring, and the push rod must rely on changing the inlet and outlet positions of the air source of the cylinder. When the air supply enters from the upper chamber of the piston, the push rod moves downward. When the air source enters from the lower chamber of the piston, the push rod moves upward. Compared with the single acting cylinder with the same diameter, the double acting cylinder has greater thrust, but does not have the automatic reset function. Obviously, different intake positions make the push rod move in different directions. When the air intake position is at the back cavity of the push rod, the air intake will make the push rod move forward, which is called positive acting cylinder. On the contrary, when the air intake position is at the push rod side, the air intake makes the push rod backward, which is called reaction cylinder. As the pneumatic stop valve generally needs the loss of air protection function, the single acting cylinder is selected.
