Acceptance Test - a test that all new pumpers should be required to pass before being accepted.

Aerial Ladder - a mechanically operated ladder on a turntable attached to a ladder truck chassis and manufactured in various lengths, generally from 65' to 100'.

Airlock - when the movement of any liquid is prevented by an air "pocket".

Air Chamber - a pump chamber filled with air, the air serving to cushion pulsations caused by the operation of pistons or gears used to displace water in a positive-displacement pump.

Alternator - an alternating current generator. The advantage of an AC generator over the DC generator is that it will charge at engine idle speed and can reach its maximum output when the vehicle is running at about 15 mph.

Apparatus - fire department vehicles

Atmospheric Pressure - the weight of the air, or atmosphere. At sea level atmospheric pressure is approximately 14.7 lbs. per sq. in. absolute. This is equivalent to 33.9 feet of head pressure. Pressure decreases one-half pound per sq. in. for each 1000 foot rise in elevation.

Auxiliary Cooling System - a manually controlled system can be used either independently of the main cooling system or to be interconnected with it. The purpose of the auxiliary system is to control the temperature of the cooling water in the engine during pumping operations.

Auxiliary Cooling Valve - the valve that activates and deactivates an auxiliary cooling system.

Auxiliary Pump - a pump of low capacity carried in addition to the regular pumping unit and used for booster tank or other low-capacity pumping. The low-capacity pump is powered by an independent engine.

Back Pressure - the same as head pressure: pressure generated by the weight of a column of water above the pump. This is usually figured as 0.434 psi per foot of elevation.

Baffle - a divider installed in fire apparatus water tanks to prevent massive shifting of the water load when the vehicle is in motion. Also, a hose bed divider.

Bleed - to drain fluid (water, oil, or air) from hose, piping, or pump.

Bleeder Cock - a drain cock installed on a pump.

Bleeder Valve - a valve located beyond the discharge shutoff of the pump. This valve is used to relieve pressure in hose lines after the discharge gates are closed.

Booster Lines - fire department hose lines, usually 3/4 or 1 inch in diameter, pre-connected to booster pumps or regular pumps and used to control small fires.

Booster Pump - small pump rated at less than 500 gpm.

Booster tank - see water tank.

Break a Line - (also break a connection). To uncouple a hose line to increase or reduce the length of the line, or to attach a nozzle or fitting.

Brush - (also booster apparatus). Lightweight vehicle that can go where larger heavier apparatus cannot.

Bypass - a method for diverting the flow of water from its natural direction. A bypass is usually controlled by one or more valves.

Bypass Valve - a valve intended to regulate around-the pump proportioning of a wetting agent. A pressure relief valve that may bypass water to prevent excessive build up of pressure.

Capacity Operation - operation of a pump at or near its rated capacity and pressure.

Cavitation - condition created by water vapor bubbles in the water in the pump.

Charge - to introduce water under pressure into a hose line or pipe.

Charged Line - a hose line filled with water under pressure and ready for use.

Check Valve - a valve that permits operation of a positive-displacement pump with discharge gates closed. This valve controls a passage between the discharge and suction sides of the pump.

Clapper Valve - a check valve.

Class "A" Pumper - a fire department pumper that under the NFPA rating tests will deliver 100 percent of its rated capacity at 150 psi, 70 percent at 200 psi, and 50 percent at 250 psi.

Class "B" Pumper - a fire department pumper that will deliver 100 percent of its rated capacity at 120 psi, 50 percent at 200 psi, and 33 1/3 percent at 250 psi.

Check a Nozzle - (also crack a valve) to open a nozzle or valve slightly to permit a small flow of water to prevent freezing or to clear the air from a hose line.

Dead end Main - a section of water main supplied from only one end.

Discharge Valve - a valve that controls the flow of water into hose lines.

Divided Hose Bed - a hose bed divided to permit the laying of more than a single line of hose or the laying of lines of different sizes.

Draft - an operation involving the removal of air from the intake side of the pump, thereby creating a pressure lower than atmospheric pressure within the pump. This permits the higher pressure exerted by the atmosphere to force water into the intake side of the pump.

Elevating Platform - a hydraulically raised platform designed for rescue and fire fighting and mounted on fire apparatus.

Engine - a fire department pumper.

Engineer - a grade established by some fire departments that provides status to individuals who meet certain standards for fire apparatus drivers and pump operators.

EP - abbreviation for engine pressure

Eye, Impeller - the opening through which water enters the impeller of a centrifugal pump.

FL - abbreviation for friction loss

Friction Loss - loss of pressure in hose, fittings, stand pipes, and other appliances because of the resistance between the water molecules and the inside surfaces of hose, fittings, stand pipes, and other appliances.

Flow Meter - a gauge that indicates flow in gallons per minute or liters per second.

Gauge, Bourdon - an instrument used to indicate pressure, vacuum, or both.

Gauge, Compound - a gauge designed to register both position pressure and vacuum.

Gauge, Pressure - an instrument used to indicate water pressure in pounds per square inch.

Gauge, Vacuum - a gauge used to register vacuum in inches of mercury.

Gallon, (U.S.) - a quantity of liquid occupying 231 cubic inches.

Governor - two types of governors are in use in fire department pumps: (1) a top-speed governor, which is required to prevent the engine from being run at a speed greater than that recommended by the engine manufacturer, and (2) a pressure regulating governor, which (when correctly set), by controlling the engine speed when one or more hose lines are shut down, acts as a safety device to prevent the pump pressure from increasing.

Governor Shutoff Valve - a valve that controls water flow from the discharge side of the pump to the governor.

Ground Jack - a type of stabilizer for aerial apparatus.

Ground Throttle Control - a hand throttle located on the operator's control panel and used to control engine speed.

Hard Intake - a flexible, rubberized length of hose with a built-in reinforcing helix. The hose is used to connect a pump to a source of water, such as a pond or lake, that requires suction (vacuum) to bring the water to the pump.

Head Pressure - back pressure.

Hookup - a pumper (or hose) connected to a source of water, and hose lines connected to discharge outlets of a pump.

HG - chemical symbol for mercury.

HP - abbreviation for horse power

Hydrant and Draft Control Valve - a shutoff valve located in the line between the pump and the primer. This valve must be in the open position when priming and in the closed position when working from a hydrant or at a draft.

Impeller - the part of a centrifugal pump that spins and places pressure on the water.

Inlet - an intake connection on a fire department pumper, to which the intake or supply hose is connected.

Intake Hose Strainer - a metal unit of either basket or flat design attached to the inlet end of a non-collapsible intake hose. It is provided with perforations small enough to exclude foreign matter, yet large enough to permit the free flow of water.

ISO - Insurance Services Office. Formerly, American Insurance Association.

NFPA - National Fire Protection Association. A non-profit educational and technical association founded in 1896. The organization is devoted to the protection of life and property against fire through the development of fire protection standards and through public education.

NP - abbreviation for nozzle pressure.

Operator's Control Panel - a panel, located on the outer body of the apparatus, upon which are mounted gauges and operating and controlling devices for the pumper. These devices complement the controls located within the driver's compartment.

Parallel Operation - an operation in which each impeller of a centrifugal pump discharges into a common outlet, thereby producing high volume at low pressure.

Pitot Tube - as used in the fire service, a curved tube that is inserted into a water stream as to direct the velocity pressure of the stream to a pressure gauge for calculation of the gpm flow.

Pressure Governor - on a centrifugal pump, a device used to maintain a constant, pre-determined pump pressure by regulating the speed of the engine.

Pressure Operation - an operation in which water passes consecutively through the impellers of a centrifugal pump, which increases the pressure on the water. (Series Operation)

Primer Control Valve - a valve installed between the main pump and the priming device.

PSI - abbreviation for pounds fer square inch.

PSIA - abbreviation for pounds per square inch absolute. Pressure above absolute.

PSIG - abbreviation for pounds per square inch gauge. The pressure above atmospheric pressure.

Pump Drain Valve - a valve, located at the bottom of a pump, through which the water is drained from the pump.

Pump Shift Lever - a lever used to engage and disengage a fire pump. It can be manual, electric, air, or hydraulic.

Pump Packing Glands - an arrangement used to form a newr watertight seal around the pump shaft where the shaft enters the pump casing.

Pump Strainer - a device placed in each pump inlet to prevent foreign matter from entering the pump.

Pump Transmission - a set of gears housed in a gear box and used to drive the pump.

Pump Transmission Cooler - a cooling unit through which water is circulated to cool the pump transmission oil.

Quad - a piece of fire apparatus equipped with a rated pump, a water tank, hose, and the ground ladders of a ladder truck. If the apparatus is to be designated as a "pump-ladder", NFPA Standard # 1901 requires that the apparatus carry the basic equipment for both a pumper and a ladder truck.

Quint - a quad equipped with an aerial ladder or elevating plat form.

Radiator Fill Valve - a valve installed to permit water from the pump to be used for filling the radiator.

Relief Valve - a device installed between the discharge and intake side of a pump, used to channel excessive pressures on the discharge side back into the intake chamber.

Residual Pressure - pressure remaining on the intake side of a pump while water is being discharged. Residual pressure can be compared with initial static pressure to indicate the additional relative volume of water available from a water supply.

Road Transmission - a set of gears housed in a gear box and used to drive the apparatus.

RPM - revolutions per minute

Series Operation - pressure operation.

Slippage - when the impeller turns faster than the water moving through it.

Soft Intake - (large) a short length of hose used to connect a pumper to a hydrant.

Supply Line - (also feeder line) a hose line leading from a source of water to a pump.

Tachometer - an instrument for indicating the revolutions per minute (rpm) of an engine.

Tanker - mobile water-supply apparatus.

Transfer Valve - a valve that permits either directing the water through the pump impellers in "series" to deliver less water at a higher pressure or through the impellers in "parallel" to deliver more water at lower pressure.

Trunnion - used to hold the cylinder rods on an aerial device to the turntable.

Triple Combination Pumper - a piece of fire apparatus equipped with a rated pump, a water tank, and hose.

Vacuum - space devoid of matter - A space entirely devoid of matter is under specific absolute vacuum. A space within a closed vessel that is exhausted to the highest degree possible by an air pump or other artifical means is under specific partial vacuum.

Volume Operation - parallel operation

Volute - wall of the pump housing as it increases toward the discharge outlet.

Water Hammer - impact energy resulting from the sudden closing of nozzles or valves on charged lines.

Water Tank - a tank that supplies the pump with water or other liquid extinguishing agent.