68 Questions
What is a key characteristic of positive displacement pumps?
They are self-priming
What is the primary mechanism used by centrifugal pumps to achieve proper discharge pressure?
Centrifugal force
What role do positive displacement pumps play in modern apparatus during drafting operations?
Priming devices to get water to the centrifugal pump
What design feature characterizes rotary gear pumps?
Consist of two gears that rotate in a tightly meshed pattern inside a watertight case
What type of pumps can provide pressures up to 1,000 psi?
Piston pumps
In modern apparatus, where is the use of rotary pumps confined to?
Small capacity, booster-type pumps
What type of pumps are the simplest of all fire apparatus pumps from a design standpoint?
Rotary-type pumps
What is a key characteristic of rotary vane pumps?
They automatically compensate for wear
What type of pump is a centrifugal pump?
Nonpositive displacement pump
What dictates the volume capacity of a centrifugal pump?
Size of the impeller
What directly influences the amount of output pressure a centrifugal pump may develop?
The volume of water it is discharging
How does increased impeller speed affect the pressure developed by a centrifugal pump?
Pressure increases roughly equal to the square of the change in impeller speed
What happens to the velocity and pressure buildup of water when it enters a centrifugal pump from a pressurized source?
Both the velocity and corresponding pressure buildup increase with any movement of the impeller
What type of pumps are unable to pump air and are not self-priming?
Centrifugal pumps
What is the characteristic of high capacity pumps in terms of impeller design?
Require large impellers with waterways that present minimal opposition to water movement
What distinguishes multistage centrifugal pumps from single stage centrifugal pumps?
Have an impeller for each stage mounted in a single housing
What happens when the pump transfer valve is set in the volume position?
The total amount of water the pump can deliver is equal to the sum of the stages
What is a key characteristic of switching from volume to pressure mode?
Results in the immediate doubling of the previous discharge pressure
What type of valves are essential to the operation of a multi-stage pump?
Clapper valves
At what pressure do many power-operated transfer valves operate?
200 psi
How many impellers are sometimes connected in series in certain fire pumps to develop pressures up to 1,000 psi?
4 impellers
What is the purpose of wear rings or clearance rings in a pump casing?
To maintain the preferred spacing between the hub of the impeller and the pump casing
What material is commonly used for seal packing in pumps?
Rope fibers impregnated with graphite or lead
What is the typical allowable opening between the pump casing and the hub of the impeller?
.01 inches or less
What is the best course of action to prevent overheating in a pump not equipped with a thermal relief valve?
Ensure that some water is moving through the pump at all times
How are pump impellers connected to a transfer case?
They are fastened to a shaft that connects them to a transfer case
What is an initial indication of wear in a fire pump?
Increased engine rpm during a pump test
What is a characteristic of power take off systems (PTO) in the context of pumps?
They are typically connected to the driveshaft
What advantage does the mounting of the pump offer in addition to pump and roll capabilities?
Shorter wheelbase and additional room for compartments
Where do front mount pumps typically get power from?
Through a gear box and a clutch connected by a drive shaft to the front of the crankshaft
What is a major disadvantage of front mount pumps?
Susceptibility of the pump and gauges freezing in cold weather
How is power supplied to the pump in most fire department pumpers?
Through the use of a split shaft gear case located in the drive line between the transmission and the rear axle
At what speed do most speedometers indicate when the engine is idling and the pump is engaged?
Between 10-15 mph
What is the minimum capacity requirement for the piping of pumpers with a capacity of 500 gpm or less, according to NFPA 1901?
250 gpm
What material is commonly used for the components of the piping system according to NFPA 1901?
Cast iron, brass, stainless steel, or galvanized steel
What is the hydrostatic test pressure that the piping system and the fire pump must withstand before being placed into service?
500 psi
What size piping is commonly found in pumpers for tank-to-pump connections?
4 inches in diameter
According to NFPA 1901 , pumpers with a capacity greater than 500 gpm should be able to flow at least how many gpms?
500 gpm
What is the minimum number of 2.5 inch discharges required for a pump with a flow rate of 750 gpm or greater, according to NFPA 1901?
At least two 2.5 inch discharges
What size tank fill line is required for apparatus equipped with tanks less than 1,000 gallons, as per NFPA 1901?
At least a 1 inch tank fill line
What is the maximum pressure at which all valves should be designed to be easily operable, according to NFPA 1901?
250 psi
What is the purpose of the engine cooler line in some pumps?
To circulate tank water through a heat exchanger to aid in cooling the engine
What is the minimum tank fill line size required for apparatus equipped with tanks greater than 1,000 gallons, as per NFPA 1901?
2 inches
What is a key requirement for discharges on the pump operator's panel, according to NFPA 1901?
Must not exceed 2.5 inches
What type of valve is commonly used on large diameter intakes and discharges?
Butterfly valve
What size of intakes or discharges does NFPA 1901 require to be equipped with slow acting valve controls?
3 inches or greater
What is essential to ensure the safety and effectiveness of personnel operating hoselines when a pump is supplying multiple attack lines?
Automatic pressure regulation
What is the most common type of valve that permits the full flow of water through a line with minimum friction loss?
Ball-type valve
What should be done after all air has been evacuated from a supply line and the bleeder valve is discharging a steady stream of water?
Close the intake valve and open the tank-to-pump valve
Pressure control devices must operate within _ after the discharge pressure rises and restricts the pressure from exceeding _ above the set level.
3-10 seconds ; 30 psi
What is the main feature of a relief valve?
Sensitivity to pressure change and ability to relieve excessive pressure within the pump discharge
What is generally recommended for setting the intake relief valves to _ when intake pressure rises more than _ above the necessary operating pressure?
open ; 10 psi
What is the purpose of a pressure governor device in relation to engine speed and pump discharge requirements?
Regulate the engine speed to match the pump discharge requirements
What is a key advantage of electric motors for powering rotary vane priming pumps?
They may be operated efficiently regardless of engine speed
What is the purpose of priming devices in fire pump operations?
To create the vacuum that makes drafting possible
What is a characteristic of rotary vane primers compared to rotary gear primers?
Require relatively high rpms
What is the purpose of the oil/fluid in conventional primers?
To seal gaps between gears and case
What is the preferred engine speed range for priming?
1,000 to 1,200 rpm
Where is the vacuum primer most effective?
At low engine rpm
Where are exhaust primers generally found?
Skid-mounted pumps or older apparatus
In order to prevent pump cavitation, electronic governors will return to idle at what pressure?
30 psi
What is the primary function of an auxiliary cooling system in a fire apparatus?
To control the temperature of coolant in the apparatus engine during pumping operations
What does a gradual increase in the amount of rpm required to pump the rated capacity indicate?
Wear in the pump and possible need for repair
What do flowmeter readouts substitute for, according to NFPA 1901?
Individual pressure discharge gauges
What is the recommended action if there is any question about the level of water in the tank?
The tank should be filled until it overflows
What is the primary purpose of the master intake gauge?
To determine the water pressure entering the pump
What does the vacuum reading approaching 20 inches indicate about the pump?
The pump is nearing its capacity and is not able to supply additional lines
What does the voltmeter provide a relative indication of?
Battery condition
Study Notes
Positive Displacement Pumps
- Key characteristic: ability to produce constant flow at a given speed, regardless of pressure
- Play a crucial role in modern apparatus during drafting operations
Centrifugal Pumps
- Primary mechanism: impeller speed to achieve proper discharge pressure
- Can provide pressures up to 1,000 psi
- Dictated by impeller speed and diameter
- Output pressure directly influenced by impeller speed and pump design
- Increased impeller speed increases pressure developed
- Water entering from a pressurized source results in no velocity and pressure buildup
- Characterized by high capacity impeller design
- Multistage centrifugal pumps distinguished from single stage by multiple impellers
Rotary Gear Pumps
- Characterized by rotary gear design
- Confined to small, low-flow applications in modern apparatus
Rotary Vane Pumps
- Characterized by rotary vane design
- Key characteristic: ability to produce constant flow at a given speed, regardless of pressure
Pump Design and Operation
- Wear rings or clearance rings in pump casing reduce wear and improve efficiency
- Seal packing material: commonly graphite or ceramic
- Typical allowable opening between pump casing and impeller hub: 0.005-0.015 inches
- Prevent overheating by ensuring adequate cooling and monitoring temperature
Pump and Engine System
- Power-operated transfer valves operate at around 100-120 psi
- Pump impellers connected to transfer case through splines or couplings
- Initial indication of wear: decreased pump performance or increased vibration
Power Take Off (PTO) Systems
- Characterized by power transfer from engine to pump
- Advantage: mounting of pump offers pump and roll capabilities
- Front mount pumps typically powered by engine crankshaft
- Major disadvantage of front mount pumps: reduced space for other equipment
Piping and Plumbing
- Minimum capacity requirement for piping: 500 gpm or less, according to NFPA 1901
- Common piping material: stainless steel or aluminum
- Hydrostatic test pressure: 1.5 times maximum operating pressure
- Common piping size: 3-4 inches for tank-to-pump connections
- Minimum flow rate for pumpers: 500 gpm or greater, according to NFPA 1901
- Minimum number of 2.5 inch discharges required: 2, according to NFPA 1901
- Tank fill line size: 2 inches for tanks less than 1,000 gallons, according to NFPA 1901
- Maximum pressure for valve operation: 100 psi, according to NFPA 1901
Valves and Controls
- Engine cooler line: cools engine and prevents overheating
- Discharge valves: commonly used on large diameter intakes and discharges
- Slow acting valve controls: required for intakes and discharges 3 inches or larger, according to NFPA 1901
- Pressure control devices: operate within 10-15% after discharge pressure rises
Priming and Relieving
- Relief valves: main feature is to prevent over-pressurization
- Recommended intake relief valve setting: 10-15 psi above necessary operating pressure
- Pressure governor device: regulates engine speed and pump discharge requirements
- Electric motors for powering rotary vane priming pumps: provide quiet and efficient operation
- Purpose of priming devices: evacuate air from pump and hoses
- Rotary vane primers: more efficient than rotary gear primers
- Oil/fluid in conventional primers: lubricates and cools primer
- Preferred engine speed range for priming: 1,000-1,500 rpm
- Vacuum primer: most effective in areas with low atmospheric pressure
- Exhaust primers: generally found in older apparatus
Monitoring and Testing
- Flowmeter readouts: substitute for pressure gauges, according to NFPA 1901
- Recommended action if unsure about tank water level: check tank level gauge
- Master intake gauge: primary purpose is to monitor intake pressure
- Vacuum reading approaching 20 inches: indicates a problem with the pump
- Voltmeter: provides relative indication of electrical system performance
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