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Pumping Apparatus Driver/Operator Handbook 3 rd Edition Chapter 9 — Fire Pump Theory

Pumping Apparatus Driver/Operator Handbook 3rd Edition · 2020. 10. 26. · Driver/Operator Handbook 3rd Edition Chapter 9 —Fire Pump Theory. Distinguish among types of positive

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  • Pumping Apparatus Driver/ Operator Handbook

    3rd Edition

    Chapter 9 — Fire Pump Theory

  • Distinguish among types of positive displacement pumps.

    Learning Objective 1

    9–1

  • Positive displacement pump

    Replaced by centrifugal pump as main pumping unit on fire apparatus

    Used as priming devices to get water

    into centrifugal pumps during

    drafting operations

    Removes air trapped in centrifugal pump

    Water is forced into the pump by atmospheric

    pressure

    Positive displacement pumps continue to serve a vital role on modern apparatus.

    9–2

  • Piston pumps operate using a piston that moves back and forth in a cylinder.

    9–3

    Click image to play

  • Multicylinder

    PTO-driven

    Pressures up to 1,000 psi (7 000 kPa) for high-pressure fog lines

    Inject foam concentrate into a water line or manifold at a higher pressure than the water pump

    Piston pumps operate using a piston which creates pressure that operates the intake and discharge valves.

    9–4

  • Simplest design of all fire apparatus pumps

    In modern apparatus, use confined to small capacity, booster-type pumps, low volume high-pressure pumps, and priming pumps

    Most in use are either rotary gear or rotary-vane construction

    Rotary pumps are used on modern apparatus.

    9–5

  • Rotary gear pumps consist of two gears that rotate in a tightly meshed pattern inside a watertight case.

    9–6

    Click image to play

  • Total amount of water pumped

    depends on size of pocket gears

    and rotation speed

    Each pocket contains a

    definite amount of water that is forced out of

    pump each time gears turn

    Susceptible to damage

    from normal wear and

    tear

    A rotary gear pump is a positive displacement pump.

    9–7

  • Rotary vane pumps are constructed with movable elements that automatically compensate for wear.

    9–8

    Click image to play

  • NOTE

    Rotary pumps are prone to failure if not exercised regularly. These pumps should be operated during routine apparatus checks.

    9–9

  • REVIEW QUESTION

    What are some different types of positive displacement pumps?

    9–10

  • Summarize facts about the operation of centrifugal pumps.

    Learning Objective 2

    9–11

  • Classified as a nonpositive displacement pump

    Pump imparts velocity to water and converts it to

    pressure within pump itself

    Nearly all modern fire apparatus feature a centrifugal pump as their main pump.

    9–12

  • Centrifugal pumps are based on the principle that a rapidly revolving disk tends to throw water toward the outer edges.

    9–13

    Click image to play

  • NOTE

    In order to develop the revolutions per minute (rpms) required for full use of the pump, the transmission must be placed in the correct gear, based on the manufacturer’s recommendation.

    9–14

  • Discharge Pressure

    Amount of water being discharged

    Speed at which the impeller is

    turning

    Pressure of the water when it

    enters the pump from a pressurized

    source

    Three main factors influence a centrifugal fire pump’s discharge pressure.

    9–15

  • Ways to prime a centrifugal pump to draft water from a static source

    External priming pump may used to remove air and allow atmospheric pressure to force water into the pump

    The use of a device that employs air from the apparatus braking system to power a Venturi device that removes air from the suction side of the pump

    A centrifugal pump is unable to pump air and is not self-priming.

    9–16

  • NOTE

    Another option involves the use of a foot valve attached to the suction hose strainer.

    9–17

  • May experience a phenomenon of cavitation

    May consist of front-mount pumps, power take off, auxiliary engine driven, and midship pumps

    Use a single intake impeller and a simple casing to provide flow up to 2,250 gpm (9 000 L/min)

    High-capacity pumps require large impellers with waterways that present minimum amount of opposition

    Single-stage centrifugal pumps are constructed with a single impeller.

    9–18

  • Impellers are usually mounted on a single shaft driven by a single drive train

    Capability to connect stages in series for maximum pressure or in parallel for maximum volume by use of transfer valve makes pumps more efficient

    Multistage centrifugal fire pumps have an impeller for each stage mounted in a single housing.

    9–19

  • The pump transfer valves can be set in parallel (volume) position or pumping in series (pressure) position.

    9–20

    Click image to play

  • Multistage centrifugal fire pumps can be switched between volume and pressure positions.

    9–21

    Manufacturers have recommendations for when transfer valve should be operated in volume or pressure positions

    Sudden changes in pressure can occur as water in pump changes its direction of flow

    Operation of transfer valve is performed manually on many older models

    Newer pumps use a power-operated transfer system

    Clapper (check) valves are essential to the operation of multistage pumps

  • NOTE

    Driver/operators should consult the manufacturer’s recommendation for the flow rate at which transfer should occur on the specific pump they are operating.

    9–22

  • CAUTION

    Switching from volume to pressure can result in the immediate doubling of the previous discharge pressure. This change may result in damage to the pump and hoselines as well as injury to firefighters.

    9–23

  • Velocity of the water moving through the impeller prevents most

    of the water in discharge from escaping back into intake

    Very close tolerance must be maintained

    between pump casing and hub of the

    impeller

    Any increase in opening lessens

    effectiveness of the pump

    Centrifugal pumps are susceptible to wear from regular use.

    9–24

  • Particles of sand pass between

    the impeller and pump casing

    Gaps increasePump is no

    longer able to pump at its

    rated capacity

    Sediment and dirt pass through the pump and cause wear on the impeller.

    9–25

  • Using wear rings or clearance rings to restore pumping

    capacity

    Shutting off all the pump discharges

    for short periods of time

    There are different ways to prevent wear and tear to the pump.

    9–26

  • Centrifugal pumps equipped with thermal relief

    valve

    Centrifugal pumps without thermal

    relief valve

    There are different ways to prevent overheating in different models of pumps.

    9–27

  • Seals are necessary to prevent air leaks that may interfere with the pump’s ability to conduct drafting operation.

    9–28

    Semi-tight seal must be maintained at the point where shaft passes through pump casing

    Transmission transfers required energy to spin impellers

    Pump impellers are fastened to shaft that connects to transfer case

    (Cont.)

  • Seals are necessary to prevent air leaks that may interfere with the pump’s ability to conduct drafting operation.

    9–29

    Mechanical seals

    Packing rings

    Ceramic seals

  • CAUTION

    If a pump is operated dry for any length of time, damage to the shaft may result. Any weakening may cause failure during future use.

    9–30

  • REVIEW QUESTION

    What is the difference between pumping in the parallel position and the series position?

    9–31

  • Distinguish among various pump mounting and drive arrangements.

    Learning Objective 3

    9–32

  • Factors in determining which pump would work best

    • Intended use• Cost• Appearance• Space requirements• Ease of maintenance

    Fire department pumps are available with many different pump drive systems.

    9–33

  • • Airport rescue fire fighting (ARFF) vehicles

    • Wildland fire apparatus• Mobile water supply

    apparatus• Trailer mounted fire pumps• Portable fire pumps

    Most common applications for auxiliary

    engine driven pumps

    Pumps powered by gasoline or diesel engines independent of the vehicle-drive engine are examples of auxiliary pumps.

    9–34

  • Most common applications

    • Initial attack• Wildland• Mobile water supply

    applications• Becoming widely used on

    structural apparatus pumpers

    Rear-engine PTO design

    • Used with success in construction and refuse industries

    • Offers versatility of pump and roll capability

    Power take-off driven fire pumps are useful in many different fire situations.

    9–35

  • Proper mounting is essential

    PTO unit is powered by idler gear in transmission

    Pressure developed determined by speed of engine

    In the past, conventional PTO units were limited to powering pumps up to approximately 500 gpm (2 000 L/min)

    Some manufacturers now provide full torque power take-offs

    PTO pumps are driven by the driveshaft and connected to power take-off.

    9–36

  • Front-mount pumps

    • Typically driven through a gear box and a clutch connected by a drive shaft to the front of the crankshaft

    • Specifications of pump and drive shaft must be matched to power source

    Some pumpers feature an extended bumper with a pump mounted between the bumper and the grill of the vehicle.

    9–37

  • Front-mount pump disadvantages

    • Pump and gauges are susceptible to freezing in cold weather

    • May obstruct airflow through vehicle’s radiator during warm weather

    • Position makes them vulnerable to damage• Location may put the driver/operator in a

    vulnerable position

    There are some disadvantages to using a front-mount pump.

    9–38

  • Pump mounted laterally across frame behind engine and transmission

    Power is supplied to pump through use of a split shaft gear case (transfer

    case)

    Power can be diverted from rear axle and transmitted to fire pump

    Midship pumps are used by most fire departments.

    9–39

    (Cont.)

  • Usual arrangement provides control of transfer case from inside cab

    Some power transfer arrangements are provided with a manual override in case of difficulty with power unit

    Not possible to transmit power to rear axle while pump is engaged

    Midship pumps are used by most fire departments.

    9–40

    (Cont.)

  • NOTE

    The driver/operator should know how to manually shift the pump into gear in the event of a malfunction with the transfer case.

    9–41

  • A lock is provided on transmission or shift lever to hold it in gear for pumping

    Possible to operate pump shift control without gears

    completing their travel

    Most apparatus equipped with an indicator light in cab

    Midship pumps are used by most fire departments.

    9–42

  • NOTE

    If the shift lever is moved from neutral during the process, the transmission may lock up and the engine may stall.

    9–43

  • • More even weight distribution on chassis• More usable compartment space

    Rear-mount pump advantages

    • Driver/operator may be more exposed to oncoming traffic

    Rear-mount pump disadvantage

    • May be powered by either a split-shaft transmission or power take-off

    Rear-mount pump power

    Rear-mount pumps are becoming increasingly popular.

    9–44

  • REVIEW QUESTION

    What are the differences between a front-mount pump, midship pump and a rear-mount pump?

    9–45

  • Describe intake and discharge piping.

    Summarize facts about valves used in a piping system.

    Learning Objectives 4-5

    9–46

  • NFPA® 1901 requires all components of piping system be of corrosion

    resistant material

    Capable of withstanding hydrostatic testing of 500 psi (3 500 kPa)

    before being placed into service

    All piping and hose must be designed to

    minimize pressure loss

    The piping and valves attached to a pump are integral components of the fire pump system.

    9–47

  • Many fires are initially fought

    with water from onboard tank

    Pumps must be capable of

    being supplied from external

    pressurized and static sources

    When using a static source, pump must be

    primed by removing all of

    the air

    Water may enter a fire pump from piping that connects to either an onboard water tank or an external water supply.

    9–48

  • NOTE

    If flow requirements will allow, refill the booster tank and keep it maintained as an emergency water supply during pumping operations. Air from the tank will be drawn back into the pump.

    9–49

  • The primary intake into the fire pump is through large-diameter piping and connections.

    9–50

  • A sufficient number of 2 ½ inch (65 mm) discharge openings must be provided to flow rated capacity of pump.

    9–51

    (Cont.)Discharge openingPreconnected attack line

    arrangement

  • A sufficient number of 2 ½ inch (65 mm) discharge openings must be provided to flow rated capacity of pump.

    9–52

    When multiple attack lines are being operated, the driver/operator must set engine discharge to highest pressure level needed

    A tank fill line should be provided from the discharge side of the pump

  • Must be constructed to be airtight and wear resistant

    Debris allowed to circulate through lines can cause damage

    The most common type of valve is the ball-type valve

    Some apparatus feature hydraulically, pneumatically, or electrically controlled valves

    Gate or butterfly valves are commonly used on large-diameter intakes and discharges

    Valves control most of the intake and discharge lines from the pump.

    9–53

  • CAUTION

    Driver/operators must ensure that intake valves are open or fully closed by the visual indicator on the pump panel.

    9–54

  • • Draining hose side of a valve

    • Making changeover without interrupting the fire streams

    • Removing all the water in cold climates

    Drain valves

    Most pump connections are equipped with drain valves on the line side of the control valve.

    9–55

  • REVIEW QUESTION

    What are some main characteristics of intake piping and discharge piping?

    9–56

  • Explain the operation of automatic pressure control devices.

    Learning Objective 6

    9–57

  • Firefighters operating nozzle may be endangered when working with unexpected and significant pressure changes

    When pump is supplying multiple attack lines, sudden changes in flow on one line can cause a pressure surge in another

    Some pressure relief valves are design to expel excess water out of pump

    NFPA® 1901 requires some type of pressure control device to be part of any fire apparatus pumping system.

    9–58

  • Two basic concepts for pressure relief

    valves

    Those that relieve excess pressure

    on discharge side of pump

    Those that relieve excess pressure on intake side of

    pump

    The main feature of a relief valve is its sensitivity to pressure change and its ability to relieve excessive pressure.

    9–59

  • Excessive pressure generally caused by shutting down one or more operating hoselines

    When drafting or pumping from the tank, the closed (draft) position is used; therefore, the water returns to the intake

    When pumping from a hydrant, the hydrant (or open) position is used so that water is discharged onto the ground

    Newer pumpers are often equipped with electronic governors

    The pressure governor is designed to regulate the engine speed to match the pump discharge requirements.

    9–60

  • NOTE

    Driver/operators must be familiar with the specifications of electronic governors installed on their fire pumps. These devices may have slightly different cut-in or cut-off ranges. If the discharge pressure is reduced below a certain point for a specified period of time, the governor will return the pump to idle mode and cancel out the original pressure setting. The driver/operator must reselect the setting to resume pumping the discharge.

    9–61

  • REVIEW QUESTION

    What is the purpose of automatic pressure control devices?

    9–62

  • Summarize facts about priming methods and devices.

    Learning Objective 7

    9–63

  • • Lower pressure will result in water being forced up into the intake hose and fire pump

    • Modern centrifugal fire pumps are unable to create this condition

    • A priming device is needed to create the vacuum that makes drafting possible

    Priming methods and devices

    • Positive placement• Exhaust• Vacuum• Air primers

    Primer types

    Successful drafting depends on creating a lower pressure within the pump and intake hose than in the atmosphere.

    9–64

  • Small versions of both the rotary vane and rotary gear type pumps are commonly in use

    Rotary vane primers require relatively high rpms as compared to rotary gear primers

    An electric motor is the most popular means of powering rotary vanes priming pumps

    Primer pump inlet is connected to a control valve that is in turn connected to the fire pump

    Most modern pumpers use positive displacement primers.

    9–65

  • Many conventional primers use an oil supply or other types of fluid.

    9–66

    As the pump wears, the clearance between the gears and the pump case increases

    A thin film of oil/fluid is drawn into the pump and seals the gaps between the gears and the case

  • Oil-less primers

    Exhaust primers

    Vacuum primers

    Air primers

    There are several other types of primers other than positive displacement primers.

    9–67

    (Cont.)

  • REVIEW QUESTION

    What are the main categories of primers?

    9–68

  • Identify characteristics of pump panel instrumentation.

    Learning Objective 8

    9–69

  • The driver/operator must be familiar with all of the instrumentation located on the pump operator’s panel.

    9–70

    Some instrumentation is specific to the operation of the fire pump

    Most devices listed as indicators may be found as gauges or electronic indicators providing a digital display

  • Used to determine water pressure entering and leaving the pump

    Intake gauge is connected to intake side of the pump and measures either positive pressure or a vacuum

    Intake gauge also provides a reading of residual pressure

    Even a slight error in the zero setting of the gauge can result in a large error in measuring vacuum on the intake side

    Discharge pressure gauge also required on a pumper

    The master intake and discharge gauges are the two primary gauges used by the driver/operator.

    9–71

  • Tachometer

    Displays engine speed in revolutions per minute

    Pumping engine coolant temperature indicator

    Displays temperature of coolant in the engine that powers the fire

    pump

    There are several devices used to measure and monitor the pump.

    9–72

    (Cont.)

  • Pumping engine oil pressure indicator

    Shows if an adequate supply of oil is being

    delivered to critical areas of the engine

    Pumping overheat indicator

    Pump operator’s panel may be equipped with an

    audible or visual indicator and warns

    when pump will overheat

    There are several devices used to measure and monitor the pump.

    9–73

    (Cont.)

  • Voltmeters and ammeters

    Voltmeter provides a relative

    indication of battery condition

    Ammeter indicates status of vehicle’s

    alternator and charging system

    Pump pressure indicators (Discharge gauges)

    Must be connected to the outlet side

    of the discharge valve so

    pressure being reported is pressure

    actually supplied to hoselines

    There are several devices used to measure and monitor the pump.

    9–74

    (Cont.)

  • Pumping engine throttle

    Used to increase or decrease speed of engine that powers

    fire pump

    Primer control

    Used to operate the priming device when the pump drafts from a static water supply

    There are several devices used to measure and monitor the pump.

    9–75

    (Cont.)

  • Water tank level indicator

    Displays quantity of water held in

    onboard water tank

    Verify accuracy of water level gauge

    during routine daily inspection

    Foam systems

    Gauges and other controls related to foam systems are usually located on

    the pump operator’s panel

    There are several devices used to measure and monitor the pump.

    9–76

  • REVIEW QUESTION

    What are three examples of pump panel instrumentation?

    9–77

  • Describe types of auxiliary cooling devices.

    Learning Objective 9

    9–78

  • Older apparatus contain one of two auxiliary

    coolers

    • Marine cooler• Immersion type cooler

    • Both types designed so coolant in the radiator does not mix with water from the fire pump

    Dramatic failure of radiator hose of other

    cooling element

    • A water stream may be used to maintain some form of cooling while interior crews withdraw to safety

    • Once crews are safe, engine should be shut down immediately

    The primary function of an auxiliary cooling device is to control the temperature of coolant in the apparatus.

    9–79

  • REVIEW QUESTION

    What are two types of auxiliary cooling devices?

    9–80

    Slide Number 1�Learning Objective 1Positive displacement pumps continue to serve a vital role on modern apparatus.Piston pumps operate using a piston that moves back and forth in a cylinder.Piston pumps operate using a piston which creates pressure that operates the intake and discharge valves.Rotary pumps are used on modern apparatus.Rotary gear pumps consist of two gears that rotate in a tightly meshed pattern inside a watertight case.A rotary gear pump is a positive displacement pump.Rotary vane pumps are constructed with movable elements that automatically compensate for wear.NOTEREVIEW QUESTION�Learning Objective 2Nearly all modern fire apparatus feature a centrifugal pump as their main pump.Centrifugal pumps are based on the principle that a rapidly revolving disk tends to throw water toward the outer edges.NOTEThree main factors influence a centrifugal fire pump’s discharge pressure.A centrifugal pump is unable to pump air and is not self-priming. NOTESingle-stage centrifugal pumps are constructed with a single impeller.Multistage centrifugal fire pumps have an impeller for each stage mounted in a single housing.The pump transfer valves can be set in parallel (volume) position or pumping in series (pressure) position.Multistage centrifugal fire pumps can be switched between volume and pressure positions.NOTECAUTIONCentrifugal pumps are susceptible to wear from regular use.Sediment and dirt pass through the pump and cause wear on the impeller.There are different ways to prevent wear and tear to the pump.There are different ways to prevent overheating in different models of pumps.Seals are necessary to prevent air leaks that may interfere with the pump’s ability to conduct drafting operation. Seals are necessary to prevent air leaks that may interfere with the pump’s ability to conduct drafting operation. CAUTIONREVIEW QUESTION�Learning Objective 3Fire department pumps are available with many different pump drive systems.Pumps powered by gasoline or diesel engines independent of the vehicle-drive engine are examples of auxiliary pumps.Power take-off driven fire pumps are useful in many different fire situations.PTO pumps are driven by the driveshaft and connected to power take-off.Some pumpers feature an extended bumper with a pump mounted between the bumper and the grill of the vehicle.There are some disadvantages to using a front-mount pump.Midship pumps are used by most fire departments.Midship pumps are used by most fire departments.NOTEMidship pumps are used by most fire departments.NOTERear-mount pumps are becoming increasingly popular.REVIEW QUESTION�Learning Objectives 4-5The piping and valves attached to a pump are integral components of the fire pump system. Water may enter a fire pump from piping that connects to either an onboard water tank or an external water supply.NOTEThe primary intake into the fire pump is through large-diameter piping and connections.A sufficient number of 2 ½ inch �(65 mm) discharge openings must be provided to flow rated capacity of pump.A sufficient number of 2 ½ inch �(65 mm) discharge openings must be provided to flow rated capacity of pump.Valves control most of the intake and discharge lines from the pump.CAUTIONMost pump connections are equipped with drain valves on the line side of the control valve.REVIEW QUESTION�Learning Objective 6NFPA® 1901 requires some type of pressure control device to be part of any fire apparatus pumping system.The main feature of a relief valve is its sensitivity to pressure change and its ability to relieve excessive pressure.The pressure governor is designed to regulate the engine speed to match the pump discharge requirements.NOTEREVIEW QUESTION�Learning Objective 7Successful drafting depends on creating a lower pressure within the pump and intake hose than in the atmosphere.Most modern pumpers use positive displacement primers.Many conventional primers use an oil supply or other types of fluid.There are several other types of primers other than positive displacement primers.REVIEW QUESTION�Learning Objective 8The driver/operator must be familiar with all of the instrumentation located on the pump operator’s panel.The master intake and discharge gauges are the two primary gauges used by the driver/operator.There are several devices used to measure and monitor the pump.There are several devices used to measure and monitor the pump.There are several devices used to measure and monitor the pump.There are several devices used to measure and monitor the pump.There are several devices used to measure and monitor the pump.REVIEW QUESTION�Learning Objective 9The primary function of an auxiliary cooling device is to control the temperature of coolant in the apparatus.REVIEW QUESTION