Double-acting
Double-acting turns up in 2 fields: valves, mechanical. Here is what it means to the people in each one.
Double-acting in valves
Describes an actuator that uses air or oil pressure to drive in both directions, with no return spring.
Supply pressure goes to one side of the piston to open and to the other side to close, so all the force is available for moving the valve and the unit is compact. On loss of air the valve simply stays where it was, called fail-last or fail-in-place, unless a volume tank or accumulator and check valve are added to give a defined fail position.
"Those big pipeline ball valves are double-acting with a volume bottle, there's no room for a spring that size."
Double-acting in mechanical
Capable of applying force in two opposing directions.
A design feature of cylinders or pistons where fluid pressure can be applied to either side of the piston. This allows the component to power both the extension and retraction strokes. It requires ports at both ends of the cylinder barrel.
"We need a double-acting cylinder for the press so we can power the die back up instead of relying on gravity."