Hydraulic Power

basics

Pascals Law

Pressure exerted at any point on a confined liquid is transmitted undiminished in all directions.

Hydraulic Terms

Hydraulic

Piston Shaft PSI

Pneumatic Stroke Check valve Spool valve

Pump Seal Rockshaft

Cylinder

Hydraulic

motor

Single-

acting

Double-

acting

Input /

Output

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

Pressure applied to piston A is transferred equally to a piston of the same

size B because PSI is the same throughout the system.

Basic

principle

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.

hydraulic

advantage

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:

PISTON

GEAR

VANE

INTERNAL ROTOR

Piston Pumps

Work well at PSIs 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.

Hydraulic Cylinder

Single-acting

Refers to a hydraulic

cylinder that works in one

direction only. Double-acting

Refers to a hydraulic

cylinder that pushes and

pulls.

Single-acting

cylinder

Double-acting

Cylinder

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.