Hydraulic Power basics
Pascal’s Law Pressure exerted at any point on a confined liquid is transmitted undiminished in all directions.
Hydraulic Tool or equipment powered by the movement of fluid under pressure. Examples are brakes, jacks & tractor lifts.
Pneumatic Tool or equipment powered or supported by the movement of compressed air.
PSI Pounds per Square Inch determines amount of force GPM Gallons per Minute determines speed of action
Basic principle Pressure applied to piston “A” is transferred equally to a piston of the same size “B” because PSI is the same throughout the system.
hydraulic advantage If the surface area of piston “B” is 10 times the surface area of piston “A”, then the force applied to piston “A” is multiplied 10 times as the force exerted on piston “B”. PSI is equal throughout the system.
Input / Output Force input on a hydraulic system or component results in transfer of power to output of force by the system or component.
Pump Functions in a hydraulic system by pressurizing and moving fluid from one part of the system to another.
Hydraulic pumps are usually one of four types:PISTONGEARVANEINTERNAL ROTOR
Piston Pumps • Work well at PSI’s of 2000 or more • Single piston pump used in bottle jacks • Require several pistons working together to generate enough volume for tractor applications • Necessarily involve many moving parts
Gear Pumps • Work well at 1500 PSI and below • Work with a minimum of moving parts • Less expensive to manufacture than piston type pumps
Gear Pump driven gear idler gear
Hydraulic Motor Receives power from moving fluid to transfer hydraulic power to mechanical rotating force.
Cylinder Piece of equipment that transfers hydraulic power into mechanical movement in one or two directions only.
Single-acting Refers to a hydraulic cylinder that works in one direction only. Double-acting Refers to a hydraulic cylinder that pushes and pulls.
Piston Internal component of a hydraulic cylinder that is moved in a linear motion by the action of fluid introduced into the cylinder.
Shaft The polished round bar that is extended from and retracted into a hydraulic cylinder.
Stroke The length of movement that a hydraulic cylinder is capable of producing.
Seal Found in hydraulic components; function is to keep fluid from leaking between moving and non-moving parts
Check Valve Restricts flow of fluid to only one direction; allows pressure to build up or be maintained.
Spool Valve Controls direction of flow of fluid in a hydraulic system to cause the different parts of the system to function.
The first hydraulic power lift for a tractor was introduced in 1935 by John Deere. This unit only had two positions, up and down, but the hydraulic action cushioned the lowering of the implement.
Rockshaft Rotating shaft on a modern tractor powered by an internal hydraulic cylinder; used to transfer power to the implement lift.