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Appendix — Glossary
gripper tool — a component used for grasping an object or electrical
lines through the use of an articulated mechanism.
ground — 1: a large conducting body with a potential of zero volts
used as a common current return for an electric circuit. 2: an object that
makes an electrical connection with a ground or with the earth.
ground fault interrupter (GFI) — a fast acting form of circuit breaker
that opens to interrupt an electrical circuit if it senses a very small
current leakage to ground, to protect personnel against a potential
shock hazard from defective electrical tools or wiring. It does this by
monitoring for any difference in current ow between the hot and neu-
tral wires in the circuit. An imbalance exceeding a very small preset
value indicates that current is nding an improper path to ground, and
causes the breaker to trip.
guard ring — see conductive shield.
hand — an extension of the reel lifter arm that allows for loading the
arbor bar.
hand control — a hand operated control lever or handle located at a
control station used to regulate a function of a unit, where the speed of
the function is proportional to the distance the control is moved.
hand latch — mechanical device used to retain the arbor bar in the
reel lifter or strand carrier hand.
heat — the form of energy that has the capacity to create warmth or
to increase the temperature of a substance. Any energy that is wasted
or used to overcome friction is converted to heat. Heat is measured in
calories or British thermal units (Btu). One Btu is the amount of heat
required to raise the temperature of one pound of water one degree
Fahrenheit.
heat exchanger — a device that transfers heat through a conducting
wall from one uid to another or into the atmosphere.
hertz (Hz) — a unit of frequency equal to one cycle per second.
high tooth — the individual tooth out of all the gear teeth on a rotation
bearing at which the minimum backlash occurs with the rotation pinion.
This is because of a slight difference between the actual and theoretical
tooth pitch lines due to manufacturing tolerances.
HLIW — hot line insulator washer.
holding valve — see load holding valve.
hood pin — in conjunction with bolts, secures the two top halves of
the disc housing together.
HOP — see hydraulic overload protection system.
horsepower (HP) — the power required to lift 550 pounds one foot in
one second or 33,000 pounds 1 foot in one minute. One horsepower
is equal to 746 watts or to 42.4 British thermal units per minute.
hose carrier — a exible component which contains hydraulic, elec-
trical, and/or air lines, usually mounted inside or along the side of an
extendible boom. As the boom is extended, the hose carrier unfolds in
a rolling motion to allow the lines to extend with the boom.
hose carrier tube — a rigid, enclosed tube which contains hydraulic,
electrical, and/or air lines, and may contain components for upper
controls. It is usually attached to a hose carrier on the side of an
extendible boom.
hot line insulator washer (HLIW) — a vehicle-mounted device which
is designed and used for cleaning pole and structure mounted transmis-
sion and distribution insulators.
HTMA — Hydraulic Tool Manufacturer’s Association.
Huck bolt — a bolt-like fastener that is placed in position and then
stretched while an end tting is swaged on. Commonly used to attach
a pedestal, subbase, and/or outriggers to a vehicle frame.
hydrant — a discharge pipe with a valve and spout at which water
may be drawn from a water main.
hydraulic control — a control that is actuated by hydraulically induced
forces.
hydraulic leveling system — an automatic hydraulic control system
which keeps the bottom of a platform parallel to or at a xed angle to
the turntable base plate as the boom is raised or lowered. One means
of accomplishing this is by transferring hydraulic uid between a master
cylinder actuated by movement of the lower boom and a slave cylinder
mounted between the platform and the upper boom.
hydraulic overload protection (HOP) system — the system on a
digger derrick that shuts off certain functions to help prevent damage
to the digger derrick structure when an overload is applied to the boom
in the downward direction.
ange — on a ange and lug pin retaining system, an end plate that is
welded to one end of the pin. The purpose of the ange is to position
the pin in the connection.
ange and lug pin retaining system — a connecting pin retention
system in which an end plate is welded to one end of the pin and a
retaining plate is attached with cap screws to the other end to hold
the pin in position.
ashover — a disruptive electrical discharge at the surface of electrical
insulation or in the surrounding medium, which may or may not cause
permanent damage to the insulation.
ats from nger tight (F.F.F.T.) — a method of counting the number
of wrench ats when tightening a hydraulic adapter to establish a
torque value.
at-shoe outrigger — an outrigger which has a shoe that is xed in
a horizontal position.
ighting — a curved plate or series of curved plates welded together,
spiraling along the axis of an auger tube or screw anchor rod.
ow — the movement of uid generated by pressure differences.
ow control valve — a valve that regulates the rate of uid ow.
ow rate — the volume, mass or weight of a uid passing through any
conductor per unit of time.
ow straightener — a component part of a nozzle used to straighten
or remove any swirling motion of uid going through the nozzle.
owmeter — an instrument used to measure the ow rate of uid in
a hydraulic tube or hose.
uid — a liquid that is specially compounded for use as a power
transmitting medium in a hydraulic system.
fold — to move a pivoting structure such an articulating upper boom
toward its stowed position.
fold-up shoe outrigger — an outrigger which has a shoe that pivots
into a vertical position when the outrigger is fully retracted.
force — any push or pull measured in units of weight.
forged pin retainer — a pin retainer made from forged steel, consisting
of a slender, cylindrical body with a attened, circular head at one end,
with a mounting hole through the head perpendicular to the body. The
body is inserted through a hole in the pin to be retained, and the head
is fastened to the adjacent structure with a cap screw.
four-way valve — a valve having four ports for direction of uid ow.
FPS — Fluid Power Society.
frequency — the number of times an action occurs in a unit of time.
gasket — a packing made of a deformable material, usually in the
form of a sheet or ring, used to make a pressure tight t between
stationary parts.
gate valve — see shutoff valve.
gauge pressure — a pressure scale that ignores atmospheric pres-
sure by establishing atmospheric pressure as its zero point. Its zero
point is 14.7 psi absolute.
gauge snubber — see snubber valve.
gearbox — an assembly with internal speed changing gears; a transmis-
sion. Gearboxes are commonly used to transmit power from a hydraulic
motor to operate a function through an output shaft.
gelcoat — a protective coating used on berglass components to
prevent the wicking of moisture into the berglass strands and to retard
the degrading effect of ultraviolet light on the berglass.
GFI — ground fault interrupter.
gib assembly — secures cutter knives in place on drum chippers.
gin pole — a vertical phase-holding apparatus which is attached to a
platform or upper boom tip.
gpm — gallons per minute.
gradient control device — a device at the upper end of an insulating
boom that reduces electrical stress level(s) below that considered to
be disruptive.
gravity leveling system — a system which uses the force of gravity
to keep the bottom of a platform parallel to level ground as the boom
is raised or lowered. One means of accomplishing this is by allowing
the platform to pivot freely about a horizontal shaft attached above the
platform’s center of gravity.
grease tting — a small tting that acts as the connection between a
grease gun and the component to be lubricated.
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