Basics of Hydraulics
Post on 21-Nov-2015
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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.
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