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Appendix — Glossary
cable stringing system — the group of steel rollers, bullwheel as-
semblies, strand sheave assemblies and fairlead which directs com-
munication cable or suspension strand from the reel it is stored on to
the working position of the operator.
calibrate — to check, adjust, or determine by measurement in com-
parison with a standard, the proper value of each scale reading or
setting on a meter or other device.
caliper — a measuring instrument with two legs or jaws that can be
adjusted to determine the distance between two surfaces.
cam — a rotating or sliding piece that imparts motion to a roller moving
against its edge or to a pin free to move in a groove on its face or that
receives motion from such a roller or pin.
candling — a method of inspecting lament wound berglass booms
by slowly passing a light through the inside of the boom in a darkened
area. Cracks, crazing, and other damage show up as dark spots or
shadows.
cap — a device located on the hand of a reel lifter that is used to
retain the arbor bar.
cap end — see base end.
cap screw — a cylindrical fastener with external screw threads at
one end and a head conguration such as hexagonal, hex socket, at
countersunk, round, or slotted at the other end, which conforms to the
dimensional and material specications published for cap screws.
capacitive coupling — the transfer of electrical energy from one
circuit to another through a dielectric gap.
capacity chart — a table or graph showing the load capacity, rated
capacity, or rated load capacity gures for a unit or accessory.
captive air system — a closed circuit, low pressure pneumatic system
used to actuate a pressure switch by means of a manually operated
air plunger.
cartridge — 1: the replaceable element of a uid lter. 2: the replace-
able pumping unit of a vane pump, composed of the rotor, ring, vanes
and side plates. 3: A removeable hydraulic valve that is screwed into
place in a cavity in a hydraulic manifold or cylinder.
catrac — see hose carrier.
caution — information that indicates a potentially hazardous situation
which, if not avoided, may result in minor or moderate injury. It may
also be used to alert against unsafe practices.
cavitation — the formation of gaseous voids in hydraulic uid caused
by a low pressure condition which typically occurs when inlet starvation
prevents the pump from lling completely with uid. The characteristic
sound of cavitation is a high pitched scream.
center mount — see behind cab mount.
center of gravity — the point in a component or assembly around
which its weight is evenly balanced.
centerline of rotation — the vertical axis about which the turntable
of a unit rotates.
centrifugal pump — a pump in which motion and force are applied
to uid by a rotating impeller within a housing.
chain — a series of identical rigid segments connected to each other
at joints which allow each segment to pivot with respect to adjacent
segments, used to transmit mechanical force.
chain extension system — a mechanical system consisting of a mo-
tor, gearbox, chains, and sprockets that is used to extend and retract
an extendible upper boom.
chain sling — an inverted Y-shaped length of chain used for lifting a
strand reel with an aerial device and placing it in a strand carrier.
chamber — a compartment within a hydraulic component that may
contain elements to aid in operation or control, such as a spring cham-
ber or drain chamber.
channel — a uid passage that has a large length dimension compared
to the dimension of the cross-section.
charge — to ll an accumulator with uid under pressure.
charge pressure — the pressure, above atmospheric pressure, at
which replenishing uid is forced into the hydraulic system.
charge pump — the hydrostatic hydraulic system pump that provides
uid at low pressure to make up for internal leakage, provides cooling
uid ow, and tilts the hydrostatic pump swash plate.
chassis — a vehicle on which a unit is mounted, such as a truck,
trailer, or all-terrain vehicle.
check valve — a valve that permits ow of uid in one direction, but
not in the reverse direction.
chip curtain — rubberized deection curtain attached to the infeed
chute.
chip deector — directs chip discharge.
circuit — the complete path of ow in a hydraulic or electrical sys-
tem.
circuit breaker — a form of electrical switch which opens (trips) to
interrupt a circuit when it senses excessive current ow that may be
caused by a short circuit, to protect wiring and components from damage.
Some types of circuit breakers reset automatically when the excessive
current discontinues and others must be reset manually.
clean out — clean out area under the lower feed roll.
clevis — a U-shaped fastening device secured by a pin or bolt through
holes in the ends of two arms.
closed center — a directional valve design in which pump output is
blocked by the valve spool(s) when the valve spool(s) is in the center
or neutral operating condition.
clutch — 1: the device on a reel lifter which allows the connection and
disconnection of the arbor bar and the driver. 2: controlled transfer of
rotational power from engine to output PTO shaft.
coaxial cable — a type of shielded cable used for conducting tele-
communication signals, in which the signal carrier is a single wire at
the core, surrounded by a layer of insulating material, which is in turn
surrounded by a metallic, conductive layer which serves as a shield,
with an overall outer layer of insulation.
combined digger derrick and platform use — the stability criteria
for a digger derrick mobile unit which indicates that the load capacity
chart and stability requirements apply to the use of the derrick for lifting
of loads with the winch line at the upper boom tip or material handling
jib tip, with the platform occupied.
come-along — a device for gripping and putting tension into a length
of cable, wire, rope, or chain by means of two jaws or attaching devices
which move closer together when the operator pulls on a lever.
communication cable — a copper wire, coaxial, or ber optic cable
used for conducting telecommunication signals.
compensating link — a mechanical linkage that serves as a connector
between the turntable and the upper boom drive mechanism. As the
lower boom is raised or lowered, this linkage causes the upper boom
to maintain its relative angle in relationship to the ground.
compensator — a valve spool that is used to maintain a constant
pressure drop regardless of supply or load pressure.
compensator control — a control for a variable displacement pump
that alters displacement in response to pressure changes in the system
as related to its adjusted pressure setting.
component — a single part or self-contained assembly.
compressibility — the change in volume of a unit volume of a uid
when it is subjected to a unit change in pressure.
conductive — having the ability to act as a transmitter of electricity.
Electricity will ow through metal, therefore metal is conductive.
conductive shield — a device used to shield the lower test electrode
system from capacitive coupling.
conductor — a wire, cable, or other body or medium that is suitable
for carrying electric current.
constant resistivity monitor — device used to continuously measure
the electrical resistance of the wash water in the tank of an insulator
washer.
contaminate — to render unt or to soil by introduction of foreign or
unwanted material.
continuous rotation — a rotation system in which the turntable is
able to rotate an unlimited number of revolutions about the centerline
of rotation without restriction.
control — a device, such as a lever or handle, which is actuated by
the operator to regulate the direction and speed of one or more func-
tions of a unit.
control bar — when manually activated, controls the movement of
feed roll(s) on a chipper.
control feed — a wood chipper which controls the infeed rate to the
cutting mechanism.
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