IFSTA - Chapter 9 Flashcards
Positive Displacement Pump
- Self-priming pump that utilizes a piston or interlocking rotors to move a given amount of fluid through the pump chamber with each stroke of a piston or rotation of the rotors
- Used for hydraulic pumps on aerial devices’ hydraulic systems and for priming pumps on centrifugal fire pumps
TYPES: Piston pumps, rotary pumps, rotary gear pumps, rotary vane pumps
PG 296-298
Piston Pumps
- Positive-displacement pump using one or more reciprocating pistons to force water from the pump chambers
- Can provide pressures up to 1000psi for high pressure fog lines or to inject foam concentrate into a water line or manifold at a higher pressure than the water pump is creating
PG 296
Rotary Pumps
- Simplest of all the fire apparatus pumps
- Use of rotary pumps is confined to small capacity, booster-type pumps; low volume, high pressure pump; and priming pumps
PG 296
Rotary Vane Pumps
- Type of positive displacement pump commonly used in hydraulic systems
- A rotor with attached vanes is mounted off-center inside the pumping house
- Pressure is imparted on the water as the space between the rotor and the pump housing wall decreases
PG 298
Centrifugal Pumps
- Pump with one or more impellers that rotate and utilize centrifugal force to move the water
- Most modern fire pumps are this type
PG 298
Operation of Centrifugal Pumps
- Based on the principle that a rapidly revolving disk tends to throw water introduced at its center toward the outer edges of the disk
1. The IMPELLER acts as a disk receiving its water through the EYE in its center
2. This water is thrown out to the VOLUTE around the outside edge of the pump housing
3. The faster the disk is turned, the harder the water is thrown, giving the water more velocity
4. The velocity of the water is converted to pressure by confining the water within the container
PG 299
Impeller
Vaned, circulating member of the centrifugal pump that transmits motion to the water
PG 299
Impeller Eye
Intake orifice at the center of a centrifugal pump impeller
PG 299
Volute
Spiral, divergent chamber of a centrifugal pump in which the velocity energy given to water by the impeller blades is converted into pressure
PG 299
Three main factors influencing a centrifugal fire pump’s discharge pressure:
- Amount of water being discharged: if discharge outlet is large enough to allow water to escape as its thrown from the impeller and collected in the volute –> pressure build up will be minimal; If discharge outlet is small or closed –> high pressure build up
- Speed at which the impeller is turning: Increased impeller speed = greater pressure is developed; typically impeller speed squared (Ex. doubling speed of impeller –> four times as much pressure)
- Pressure of water when it enters the pump from a pressurized source (hydrant, relay, etc): water will flow through centrifugal pump even if impeller is not turning; movement of impeller increases both velocity and corresponding pressure build up of the water in the volute
PG 300
Two Types of Centrifugal Fire Pumps
- Single-Stage Centrifugal Fire Pump
- Multistage Centrifugal Fire Pump
PG 300
Single-Stage Centrifugal Fire Pump
- Pumps constructed with single impeller
- Provide flow capacities up to 2250 GPM
- To minimize lateral thrust of large quantities of water entering the eye of the impeller –> double-suction impeller may be used (takes in water from left and right side, to prevent any lateral thrust from having one sided intake)
PG 301
Multistage Centrifugal Fire Pump
- Centrifugal pumps have an impeller for each stage mounted in a single housing
- Feature that makes multistage pumps more efficient is the capability to connect the stages in series for maximum pressure or in parallel for maximum volume by use of a transfer valve
- Pumping in PARALLEL (volume) POSITION: Each of the impellers takes water from a source and delivers it to the discharge; each impeller delivers its rated pressure while flowing 50% of its rated capacity (Ex. two-stage pump rated @ 1000GPM, 150PSI –> each impeller supplies 500GPM (1000 total) at 150PSI; max flow rating is met but volume of the pump can increase with capability of the water source
- Pumping in SERIES (pressure) POSITION: All water from the intake manifold is directed into the eye of the first impeller; first stage increases the pressure and discharges 50-70% of volume capacity through the transfer valve and into the eye of the second impeller; series position greatly increases pressure discharged, but with a loss in corresponding volume
PG 302
Parallel (Volume) Pumping Mode capabilities
- When in doubt, it is best to operate in parallel (volume) mode rather than series (pressure) mode
- Parallel mode = pump is capable of supplying 100% of its rated capacity at 150PSI @ 10 feet of lift with 20 feet of suction hose while drafting
PG 303
Clapper (Check) Valves
- Hinged valve that permits the flow of water in one direction only
- Check Valve is automatic version of hinged valve
- Ex. The inline valve that prevents water from flowing into a foam concentrate container when eduction pressure is disrupted
PG 304
Wear Rings
Replaceable rings that are attached to the impeller and/or the pump casing to allow a small running clearance between the impeller and pump casing without causing wear of the actual impeller or pump casing material
PG 304
Auxiliary Engine Drive Pumps
- EX. Pumps powered by gasoline or diesel engines independent of the vehicle-drive engine
- Most common applications: ARFF vehicles, wildland fire apparatus, mobile water supply apparatus, trailer mounted fire pumps portable fire pumps
- Pump capacity of generally 500 GPM
PG 307
Power Take-Off Drive (PTO)
- Mechanism that allows a vehicle engine to power equipment such as a pump, winch, or portable tool
- Typically attached to the transmission
- Most common to initial attack, wildland or mobile water supply applications
- Allows pump-and-roll capability
- Pump capacity generally up to 500GPM, but some as large as 1250GPM
PG 307-308
Front-Mount Pumps
- Fire pump mounted in front of the radiator of a vehicle and powered off the crankshaft
- Typically up to 1250 GPM
- Disadvantage: susceptibility of pump and gauges to freeze in cold weather due to their exposed position
PG 309
Midship Pumps
- Mounted behind the engine and transmission
- Most common kind for modern pumpers; power can be diverted from rear axel and transmitted to fire pump
PG 309
What speed will show on speedometer when truck is idling, pump engaged?
10-15mph
PG 310
Signs that truck is successfully in pump mode?
- Pump indicator light
- Speedometer reading
- Listening for sound of pump engaging
PG 311
Disadvantage of rear-mount pumps?
Driver/operator is more exposed to oncoming traffic than other pump locations
PG 312
Pump Pipes and Valves
- NFPA 1901: requires all components of piping system be of corrosion resistant material (cast iron, brass, stainless steel, galvanized steel)
- Must be capable of withstanding a hydrostatic test of 500 PSI
PG 312
Intake Piping
- NFPA 1901: pumpers with capacity of 500 GPM or less should have piping capable of flowing 250 GPM; pumpers with capacity of 500 GPM or more should have piping capable of flowing at least 500 GPM
PG 313
Discharge Piping
- NFPA 1901: All fire apparatus with a rated pump capacity of 750gpm or greater must be equipped with at least TWO 2.5” discharges; apparatus with a rated pump capacity of 750gpm or less only have to have ONE 2.5” discharge
- NFPA 1901: Apparatus equipped with tanks of less than 1000gpm must have a tank fill line of at least 1” in diameter; apparatus equipped with tanks greater than 1000gpm must have a tank fill line of at least 2”
PG 315-316
Valves
- Control most of the intake and discharge lines
- Most common is ball type valve that permits the full flow of water through a line with a minimum friction loss
- Most common actuator (handle) for ball type valve are either push-pull handles (T) or quarter-turn handles
- Gate valves - typically operated by hand wheel and control large diameter pipes
PG 317
Bleeder Valve
- Intake line is full of air when dry, so the water coming through the line would force air into the pump, which may cause a momentary loss of prime and fluctuation to nozzle pressure
STEPS:
1. Open bleeder valve on line side of intake vale
2. Air is forced out of the hose and passes through the bleeder as the hose fills with water
3. When all air has been evacuated from the line and bleeder is discharging steady stream of water, close bleeder valve
4. Open intake valve
5. Close tank to pump valve
PG 318
Automatic Pressure Control Devices
- NFPA 1901: Requires some type of pressure control device to be part of any fire apparatus pumping system
- Must operate within 3-10 seconds after the discharge pressure rises and restricts the pressure from exceeding 30psi above the set level
PG 318
Relief Valves
- Sensitivity to pressure change its ability to relieve excessive pressure within the pump discharge
- Most are set to be open when the intake pressure rises more than 10psi
- Two basic types:
1. Those that relieve excess pressure on the DISCHARGE SIDE of the pump –> controls pressure that is delivered to the hoseline nozzle from the pump
(EX. when the pump discharge pressure rises higher than allowed by the pilot valve setting, the spring in the pilot valve compresses, allows needle valve to move to left, causing water to dump back into pump intake. This reduces the pressure in the tube and behind the main valve. Main valve opens and permits water to return to the intake side, reducing discharge pressure)
2. Those that relieve excess pressure on the INTAKE SIDE of the pump - Permits the pump to continue operation when pressure rises above the working, or set, pressure
(EX. Pressure rises above the set pressure, pilot valve moves, compresses its spring until opening in the pilot valve housing is uncovered. Water flows through this opening and through the bleed line, and into pump intake. This reduces the pressure on the pilot valve side of the relief valve, allowing the higher pressure on the discharge side to force the valve open. Water flows from the discharge into the intake, relieving the excessive pressure)
PG 319
Pressure Governor
- Pressure control device that controls engine speed, eliminating hazardous conditions that result from excessive pressure
- Regulate engine speed to match pump discharge requirements
- Electronic governor features cavitation protection –> returns engine to idle when intake pressure drops below 30psi
PG 321
Cavitation
- Condition in which vacuum pockets form due to localized regions of low pressure at the vanes in the impeller of a centrifugal pump, causing vibrations, loss of efficiency, and possibly damage to the impeller
PG 321
Priming Device
Any device usually a positive displacement pump, use to exhaust the air from inside a centrifugal pump and the attached hard suction
- This creates a partial vacuum, allowing atmospheric pressure to force water from a static source through the suction hose into the centrifugal pump
PG 322
Venturi Effect
- Physical law stating that when a fluid, such as water or air, is forced under pressure through a restricted orifices, there is an increase in the velocity of the fluid passing through the orifice and a corresponding decrease in the pressure exerted against the sides of the constriction.
- Because the surrounding fluid is under greater (atmospheric) pressure, it is forced into the area of lower pressure
PG 324
Tachometer
- Displays the engine speed in RPMs
- Provides an experienced driver/operator with a means to identify problems during a pumping operation
PG 326
Voltmeter
- Device used for measuring existing voltage in an electrical system
- Provides a relative indication of battery condition
PG 326
Ammeter
- Gauge that indicates both the amount of electrical current being drawn from and provided to the vehicle’s battery
- Indicates status of the vehicle’s alternator and charging system
PG 326
Auxiliary Cooling Devices
- Control the temperature of coolant in the apparatus engine during pumping operations
- Either MARINE or IMMERSION
Which type of valve is commonly used on large diameter intakes and operated by a quarter-turn handle?
Butterfly valve
PG 317
What is NOT indicated by a vacuum gauge connected to the intake side of the pump?
Net Pump Pressure
PG 324-325
What are correct uses of drain or bleeder valves?
- Provide a discharge for air trapped in supply lines
- Drain the pump and piping in freezing weather climates
- Relieve pressure in a hoseline when both the discharge valve and nozzle are closed
PG 317-318
What will be the result if a small amount of water is permitted to leak around the impeller shaft packing?
The water will prevent excessive heat buildup between the shaft and packing
PG 306
Because there is no mechanical obstruction between the intake and discharge sides of a centrifugal pump, ________ ?
Intake pressure directly affects discharge pressure
PG 300
Which statement about large diameter intakes piped to the front and rear of the vehicle is correct?
They may have a maximum flow capacity significantly less than side intakes of equal diameter
PG 314
What is the most common type of drive system for a priming pump?
Electric motor
PG 322
NFPA standards require that for a pumper with a rated capacity of 500gpm or less, the piping supplying the pump from the tank must be able to flow a minimum of ___________ GPM?
250GPM
PG 312
In addition to refilling the tank water, what can the tank fill line be used for?
Prevent overheating of the pump
PG 316
NFPA standards require that for a pumper with a rated capacity of 500gpm or greater, the piping supplying the pump from the tank must be able to flow a minimum of ___________ GPM?
500 GPM
PG 312
Pump water flows through tubing surrounded by a jacket through which engine coolant is circulated in a(n) ___________ ?
Immersion cooler
PG 329
If all other factors are constant, doubling the speed of the impeller of a centrifugal pump will result in approximately __________ times more pressure?
Four
PG 300
The NFPA requires that a pressure control device be activated when discharge pressure rises ________ PSI above the set pressure?
30 psi
PG 318-319
How does a vacuum primer operate?
Vacuum from the intake manifold is piped directly into the pump
PG 323
“Full torque” power take-off units limited pump capacity to about ________ GPM?
1250 GPM
PG 308
A gauge indicating pressure on the discharge side of a standard fire pump should be numerically calibrated zero to ________ psi?
600 psi
PG 324
Purpose of auxiliary cooler?
Prevent engine coolant overheating
PG 329
What is the power arrangement on an engine with a transfer case?
A gearbox directs power to either the drive axle or to the pump
PG 309
Which device is designed to protect the pump from damage due to water hammer?
Intake pressure relief valve
PG 320
Which part of the centrifugal pump imparts energy in the form of velocity to the water?
Impeller
PG 299
Which type of pump cannot prime itself?
Centrifugal
PG 300
NFPA requires slow-acting valve controls on intakes or discharges equal to or greater than _______ in diameter?
3”
PG 317
What is the advantage of a rotary vane pump over a rotary gear pump?
It self-adjusts to compensate for wear
PG 298
TRUE/FALSE: Pump and Roll operations are not possible with transfer pump drive systems?
True
PG 310
What is the most common actuating mechanism of a relief valve?
A spring loaded pilot valve
PG 319
Multistage centrifugal pump differ from single stage centrifugal pump?
In the number of impellers
PG 301
Most common application for rotary pumps in the fire service?
Priming pumps
PG 296
To deliver maximum pressure, the impellers of a multistage pump should be configured for _________ operation?
Series
PG 302
Where are bleeder valves located on the control valve?
Line
PG 317
When operating Pump and Roll with a PTO driven pump, what should the driver/operator do?
Drive by the cab-mounted pressure gauge rather than the speedometer
PG 308
How is vacuum indicated on a gauge?
Inches of mercury
PG 324
Vernier
Rotating throttle knob
PG 327
Prior to being put into service fire apparatus pump and piping must be tested to _________ psi?
500 PSI
PG 312
Correct engine speed for priming is about _______ RPM?
1000-1200 RPM
PG 322
The master pump discharge pressure gauge registers water pressure as it _________ ?
Leaves the pump
PG 324
With a straight 3” pump intake pipe, incoming flow may be as much as _________ GPM?
450 GPM
PG 450
In a two-stage pump, water from both stages is being directed into the discharge. Which mode of operation is this?
Parallel
PG 301
What type of pump contains two tightly-meshed gears inside a closely fitting case?
Rotary Gear
PG 296
In a centrifugal pump, what part of the casing forms a water passageway that gradually increases in size as it nears the pump discharge?
Volute
PG 299
With a positive displacement pump, the amount of fluid pumped __________ ?
Is constant at a given pump speed
PG 295
When in doubt, which mode of operation should you select for multistage pump?
Parallel
PG 303
What is one of two basic types of positive-displacement pumps commonly used in the fire service?
Piston
PG 296
Why is centrifugal pump intake piping located below the level of the eye of the impeller?
To prevent air from accumulating in the intake pipes
PG 313
Centrifugal pumps with a single impeller are rated for capacities up to __________ ?
2250 GPM
PG 300
What is the first indication of significant wear in a centrifugal pump?
Higher engine speed is required for the pump to meet its rated capacity
PG 304
When should you operate a multistage pump in its parallel (volume) configuration?
Anticipated discharge volume exceeds a figure specified by the apparatus manufacturer
PG 302
Which part of a centrifugal pump channels water to the discharge?
Casing
PG 299
Which type of valve is used on large diameter intakes and is operated by a handwheel?
Gate
PG 317
Front mount pumps are driven by __________ ?
The front of the crankshaft
PG 308
Rotary type primers are usually driven by _________ ?
An electric motor
PG 296
What type of pump uses rotating gears to trap water against the pump casing and move it to the discharge outlet?
Rotary Gear
PG 296
Which type of gauge indicates vacuum?
Intake
PG 324
Inoperative clapper valves in a multistage pump cause improper operation while __________ ?
In series mode
PG 304
When not in operation, water can pass through the intake side and discharge side of which pump type?
Centrifugal
PG 300
A properly adjust impeller shaft packing gland should __________ ?
Drip water when the pump is operating under pressure
PG 306
How does a relief valve prevent the pump discharge pressure from exceeding the set pressure?
Bypassing water from the discharge to the intake side of the pump
PG 319
How does a pressure governor regulate pump discharge pressure?
Adjusting engine throttle speed
PG 321
Conventional power take off units limit pump capacity to about _________ GPM?
500 GPM
To deliver maximum volume, the impellers of a multistage pump should be configured for _________ operation?
Parallel
PG 301
What happens when a centrifugal pump is run with all the discharges closed?
The energy of the spinning impeller is dissipated in the form of heat
PG 306
The exhaust primer operates by using exhaust gas to __________ ?
Create a venturi effect
PG 323
Which type of primer relies on the venturi effect?
Air primer
PG 324
Which device directs the flow of water between the impellers of a multistage pump?
Transfer valve
PG 302
TRUE/FALSE: Exhaust primers are typically found on skid-mount pumps
True
PG 323
What is the minimum complement of pump pressure gauges that a fire service pump must have?
A master intake pressure gauge and a master discharge pressure gauge
PG 324
Which priming system operates best at low engine RPM?
Vacuum
PG 323
Engine coolant flows through small tubes surrounded by a jacket through which cool pump water is circulated in a ________ ?
Marine-type cooler
PG 329
PTOs used on apparatus with automatic transmissions are driven by ____________ ?
The flywheel
PG 308
Which pump type is non-positive displacement?
Centrifugal
PG 298
