Service Manual

I
HYDRAULIC TERMS (cont’d)
Power
Power
is the rate at which work is done or
energy is transferred. Power is measured in foot
pounds per second (ft lbs/sec).
Power Work Time
One horsepower is equal to 550 ft lbs/sec.
Moving
55 pounds 10 feet in one second takes
one horsepower.
In hydraulics, to transmit power
two factors must
be present; pressure and flow.
Power Pressure X Flow
Pressure
Pressure provides the potential to transmit
energy. It is determined by the force across an
area. Pressure is measured in pounds per
square inch (psi).
Pressure Force Area
Ten pounds of force acting on one square inch
provides
10 psi of pressure.
Increasing the load on a hydraulic system will
increase the operating pressure of the system.
In a hydrostatic transmission, higher pressures
will be generated going uphill as compared to
going downhill.
Flow
Flow -measures the transfer rate (velocity) of a
liquid passing through a given cross-sectional
area. Flow is measured in gallons per minute
(gpm).
Flow Area X Velocity
Flow Volume Time
The flow rate of a hydraulic system determines
the speed at which the system operates.
Horsepower
55 Ibs
1 second
I I
3.4297.435
Productivity Series