Brake Valve -
A hydraulic counterbalance valve is usually bolted to the hoist port of the hydraulic motor. It allows
oil to flow freely through the motor in the hoisting direction. When oil pressure tries to rotate the motor in the low-
ering direction, the brake valve blocks the flow of oil out of the motor until the internal static brake is released. It
then controls lowering speed based on the load and flow of oil to the motor. All the heat generated by controlling
the speed of the load is dissipated by the hydraulic system, not by the internal static brake.
Grooved Drum -
A cable drum with grooves on the barrel to ensure the first
layer of cable spools properly onto the drum. The grooves can be cast or
machined into the drum, or cast or machined into separate pieces that are
mechanically fastened to the drum.
NOTE:
Only one size cable can be used
on a grooved drum.
Sprag or Over-Running Clutch -
A mechanical one-way clutch on the input shaft of the hoist, between the input
shaft and the static mechanical brake. The clutch allows the input shaft to turn freely in the direction required to
spool cable onto the drum (i.e. lift a load), then immediately locks the hoist gear train to the mechanical brake when
the hoist is stopped, holding the load in place.
Static, Mechanical, or Load-Holding Brake -
A multi-disc, spring applied, hydraulically released brake that works
together with the sprag clutch to hold a suspended load. This brake is not designed to stop a load being lowered,
but holds the load in place when the hoist is not being operated.
First Layer Line Pull Rating -
The maximum rated line pull (in pounds or kilograms) on the first layer of cable.
The maximum rating for any particular hoist is based on maintaining an acceptable structural design factor and
service life. Certain combinations of drum, gear ratio, motor and hydraulic pressure, may reduce this rating.
First Layer Line Speed Rating -
The maximum rated line speed (in feet or meters per minute) on the first layer
of cable. Certain combinations of drum, gear ratio, motor and hydraulic flow may reduce or increase this rating.
D/d Ratio -
The ratio of cable drum barrel diameter (D) to wire rope diameter (d). Current ANSI standards require
a minimum of 17:1.
EXAMPLES:
If you know the cable diameter you want to use, multiply it by 17 to get the MINIMUM cable drum barrel diameter.
(i.e.
½
inch wire rope X 17 = 8.5 inches - this is the
minimum
hoist barrel diameter)
If you know the barrel diameter, divide it by 17 to get the MAXIMUM wire rope diameter.
(i.e. 10 inch barrel diameter / 17 = 0.588, or 9/16 inch - this is the
maximum
wire rope diameter)
Cable Drum Dimensions -
Fleet Angle -
The angle between the wire rope’s position at the extreme end wrap on a drum, and a line drawn
perpindicular to the axis of the drum, through the center of the nearest fixed sheave or load attachment point.
3
GLOSSARY OF TERMS
a
b
First sheave
or load
First sheave or load should be
centered between the drum
flanges, so that angle “a” and
angle “b” are equal.
Angles “a” and “b” should be a
minimum of
½
degree and a
maximum of 1
½
degrees.
Wrap -
A single coil of wire rope wound on a drum.
Layer -
All wraps of wire rope on the same level between drum flanges.
Freeboard -
The amount of drum flange that is exposed radially past the last layer of wire rope. Minimum free-
board varies with the regulatory organaization. ASME B30.5 requires
½
in. minimum freeboard.
Flange
Diameter
Barrel
Diameter
Distance
Between
Flanges
