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Appendix — Glossary
Glossary
2nd stage boom — see intermediate boom.
3rd stage boom — see upper boom.
A-frame outrigger — an extendible outrigger having two diagonal
members which are connected at the top and joined near the midsection
by a horizontal cross piece. Resembles a broad based “A.”
above rotation — in reference to a position on or about a unit that is
vertically above the rotation bearing.
absolute — a measure having as its zero point or base the complete
absence of the item being measured.
absolute pressure — a pressure scale with the zero point at a perfect
vacuum.
access hood ― hinged part of the disc housing used to access the
cutter disc.
accumulator — a container used to store uid under pressure as
a source of hydraulic power or as a means of dampening pressure
surges.
actuator — a device for converting hydraulic energy into mechanical
energy, such as a motor or cylinder.
adapter — a device used to connect two parts of different type or
diameter.
adhesion promoter — surface prepping solvent for UV coating.
adjusting stud — a component of a cable drive system that is threaded
on both ends and has a hex adjusting at in the center. It secures the
drive cable to the cylinder rod and can be used to adjust the tension
of the drive cable.
aeration — the entrapment of air in hydraulic uid. Excessive aeration
may cause the uid to appear milky and components to operate errati-
cally because of the compressibility of the air trapped in the uid.
aerial control valve — the control valve on the turntable of an elevator
unit which operates the movement functions of the aerial device.
aerial device — a vehicle-mounted device with a boom assembly
which is extendible, articulating, or both, which is designed and used
to position personnel. The device may also be used to handle material,
if designed and equipped for that purpose.
Allen wrench — a six-sided wrench that ts into the hex socket of a
cap screw or set screw.
American National Standards Institute (ANSI) — a self-governing
body of professionals whose primary objective is to prevent accidents
by establishing requirements for design, manufacture, maintenance,
performance, use and training for manufactured goods including aerial
devices and digger derricks.
anaerobic adhesive — a bonding agent or adhesive that cures in
the absence of air.
analog signal — an electrical signal that communicates information
by the continuous variation of voltage or current level within a dened
range, in proportion to an input parameter such as pressure or control
lever position.
annular area — a ring shaped area. Usually refers to the piston area
minus the cross-sectional area of the rod of a hydraulic cylinder.
ANSI — see American National Standards Institute.
anti-two-block (ATB) system – the system that helps prevent dam-
age to the winch line or boom by preventing a two-blocking condition
from occurring, by shutting off certain functions when the load hook,
overhaul ball, hook block, or other lifting component that is attached
to the winch line approaches near the boom tip.
antirotation fork — a two-pronged retainer which is fastened to the
inside of the turntable and used to prevent movement of the rotary
joint outer housing.
antifoam additive — an agent added to hydraulic uid to inhibit air
bubbles from forming and collecting together on the surface of the
uid.
antiwear additive — an agent added to hydraulic uid to improve
the ability of the uid to prevent wear on internal moving parts in the
hydraulic system.
anvil — The stationary blade on a chipper cutting mechanism.
arbor bar — the shaft or spindle that is used to support a cable reel.
arbor bar collar — a cylindrical device that is used to secure a cable
reel on an arbor bar.
arm — 1: the primary load-carrying structure of an articulating arm. 2:
the primary load-carrying structure of a single elevator. 3: the articulat-
ing structure which supports the arbor bar for reel lifting.
arm cylinder — the hydraulic cylinder that moves the arm of a single
elevator up and down.
articulating arm — a system located between the turntable and lower
boom of an aerial device which is used for lifting the boom assembly
to increase the platform working height. This system includes the arm,
link(s), riser and articulating arm cylinder.
articulating arm cylinder — the hydraulic cylinder that moves an
articulating arm up and down.
articulating-boom aerial device — an aerial device with two or more
boom sections that are connected at joint(s) which allow one boom to
pivot with respect to the adjacent boom.
ASTM — American Society for Testing and Materials.
atmosphere (one) — a pressure measure equal to 14.7 psi.
atmospheric pressure — pressure on all objects in the atmosphere
because of the weight of the surrounding air. At sea level, about 14.7
psi absolute.
atmospheric vents — a vacuum prevention device designed to allow
air to enter a hydraulic line that has encountered an internal pressure
below that of the atmosphere (vacuum).
attention — information that must be followed to reduce the likelihood
of property damage. Property damage could include structural damage
to the unit, component failure, or damage to nearby property.
auger — the hole boring tool of the digger, consisting of a hollow tube
with hardened teeth attached at one end to dig into and break up soil
and/or rock as the auger is rotated. Several turns of ighting are welded
to the tube to carry the loose material away from the teeth.
auger extension shaft — a shaft which ts into the auger tube to
connect the digger output shaft to the auger.
auger rotation hydraulic system — the hydrostatic system on a pres-
sure digger which operates the auger transmission gearbox.
auger stow bracket — the bracket on a digger derrick lower boom
which stores the digger and auger assembly when it is not in use.
auger stow switch — a limit switch which is actuated by the auger
to shut off digger operation in the stowing direction when the auger
reaches its fully stowed position in the auger stow bracket.
auger transmission gearbox — the gearbox mounted on the mast
weldment of a pressure digger that is used to rotate the kelly bar.
auger tube — the hollow tube at the centerline of an auger to which
the auger ighting is welded.
auger windup sling — the cable or strap attached to the auger stow
bracket which is used to store the digger and auger.
auxiliary engine — a separately mounted engine that is used to provide
power for the unit’s hydraulic system.
auxiliary hydraulic system — the secondary hydraulic system of a
pressure digger that operates all the hydraulic functions except auger
rotation.
AWS — American Welding Society.
back pressure — pressure existing in the discharge ow from an ac-
tuator or hydraulic system. It adds to the pressure required to operate
an actuator under a given load.
backlash — the clearance at the tooth contact point between the
adjacent gear teeth of two or more meshing gears.
bafe — a device, usually a plate, installed in a reservoir to separate
the return line inlet from the suction line outlet.
band of arrows — decals used on extendible and articulating upper
booms to dene the boom tip area and the insulating portions of the
upper boom and lower boom insert.
bare-hand work — a technique of performing live line maintenance on
energized conductors and equipment whereby one or more authorized
persons work directly on an energized part after having been raised
and bonded to the energized conductors or equipment.
barrel — the hollow body of a hydraulic cylinder into which the piston
and rod are assembled.
base boom — see lower boom.
base end — 1: the closed end of a hydraulic cylinder, opposite from the
end that the rod extends from. 2: the end of an extendible boom that is
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