Ch 9. Fire Pump Theory Flashcards by George Carpenter

What is a 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 the piston or rotation of the rotors.

How well did you know this?

Not at all

Perfectly

Where are positive displacement pumps used?

Used for hydraulic pumps on aerial devices’ hydraulic systems and for priming pumps on centrifugal fire pumps

How well did you know this?

Not at all

Perfectly

Positive displacement pump’s produce the same flow at a given speed regardless of discharge pressure which makes them what type of machines?

Constant flow machines

How well did you know this?

Not at all

Perfectly

Modern fire department pumpers are equipped with what type of pumps as their main pump?

Centrifugal pumps

How well did you know this?

Not at all

Perfectly

How do centrifugal pumps produce pressure?

Centrifugal pumps rely on velocity of the water produced by centrifugal force to provide the pressure needed to achieve proper discharge pressure

How well did you know this?

Not at all

Perfectly

How are positive displacement pump’s still used in modern Apparatus?

because of their ability to pump foam and air they are still used as priming devices to get water into the centrifugal pump during drafting operations

How well did you know this?

Not at all

Perfectly

Where are piston pumps still used in firefighting operations?

These multicylinder PTO driven pumps can provide pressures up to 1000 psi for high-pressure fog lines, or to inject foam concentrate into a waterline or manifold at a higher pressure than the water pump is creating

How well did you know this?

Not at all

Perfectly

Where are rotary pumps still used today in modern Apparatus?

Rotary type pumps are the simplest of all apparatus pumps and are confined to small capacity, booster type pumps and low volume, high pressure pumps and priming pumps

How well did you know this?

Not at all

Perfectly

How are rotary pumps powered?

Rotary pumps are driven by either a small electric motor or through a clutch that extends from the apparatus driveshaft

How well did you know this?

Not at all

Perfectly

What are the two designs of rotary pumps?

Rotary pumps are either rotary gear or rotary vein construction

How well did you know this?

Not at all

Perfectly

How do rotary gear pumps operate?

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

How well did you know this?

Not at all

Perfectly

What determines how much water can be pumped by a rotary gear pump?

The amount of water that can be pumped depends on the size of the pockets in the gears and the speed of rotation

How well did you know this?

Not at all

Perfectly

Like piston pumps, the rotary gear pump is susceptible to damage from normal wear and tear as well as from __________?

Debris and sand laden water

How well did you know this?

Not at all

Perfectly

What is the most common type of pump used to prime a centrifugal fire pump

Rotary vein pumps. They are constructed with movable elements that automatically compensate for wear, maintaining a tighter fit with closer clearances as the pump is used

How well did you know this?

Not at all

Perfectly

What is a centrifugal pump

Pump with one or more impellers that rotate and utilize centrifugal force to move the water.

How well did you know this?

Not at all

Perfectly

A centrifugal pump does not pump a definite amount of water with each revolution so this pump is classified as a ______________?

Non-positive displacement pump

How well did you know this?

Not at all

Perfectly

How does a centrifugal pump move water?

The impeller disk receives its water through the eye and its center. This water is thrown out to the volute around the outside edge of the pump housing.

How well did you know this?

Not at all

Perfectly

What dictates the amount of pressure that is developed by a centrifugal pump

The speed of the impeller dictates the amount of pressure that is developed. The faster the disc is turned, the harder the water is thrown giving it more velocity

How well did you know this?

Not at all

Perfectly

In order to develop the revolutions per minute required for use of the centrifugal pump, what must be done with the vehicle transmission?

The transmission must be placed in the correct gear based on the manufactures recommendation

How well did you know this?

Not at all

Perfectly

In a centrifugal pump, as the water moves away from the impeller it enters a water passageway of gradually increasing size as it nears the discharge outlet of the pump. This section of the pump is called the __________?

Volute

How well did you know this?

Not at all

Perfectly

What three main factors influence a centrifical fire pumps discharge pressure?

Amount of water being discharged
Speed at which the impeller is turning
Pressure of water when it enters the pump from a pressurized source

How well did you know this?

Not at all

Perfectly

Why must a priming pump be used to prime a centrifugal pump

Centrifugal pumps are unable to pump air and is not self priming

How well did you know this?

Not at all

Perfectly

What are the two basic types of centrifugal pumps used by the fire service?

Single stage and multistage

How well did you know this?

Not at all

Perfectly

Where is the rotor mounted in a rotary vane pump?

The rotor is mounted off-center inside the housing

How well did you know this?

Not at all

Perfectly

What part of a centrifugal pump transmits energy in the form of velocity to the water?

The impeller

What dictates the volume capacity of the centrifugal pump

The size of the impeller

What type of centrifugal pump is constructed with a single impeller in may consist of front mount pumps, power takeoff, auxiliary engine driven and mid ship pumps?

Single stage centrifugal pumps

What is the impeller Eye?

The intake orifice at the center of a centrifugal pump impeller

What is an impeller

The vaned, circulating member of the centrifugal pump that transmits motion to the water

What type of centrifugal fire pump has an impeller for each stage mounted within a single housing?

Multi stage centrifugal pump

Multistage centrifugal pumps have an impeller for each stage mounted in a single housing. Generally, the impellers are identical and have the same ________ ?

Capacity

Multi stage centrifugal fire pumps can pump in two modes these modes are called?

Pumping in the parallel (volume) position Pumping in the series (pressure) position

How does a multistage centrifugal pump operate in the parallel or “volume”position?

Each impeller takes water from a source and delivers it to the discharge. Each of the impellers is capable of delivering it’s rated pressure while flowing 50% of its rated capacity

How does the multi stage centrifugal pump operate in the series or “pressure”position?

All water from the intake is directed into the eye of the first impeller. The first stage increases the pressure and discharges 50 to 70% of the volume capacity through the transfer eye into the second impeller. The second impeller delivers water at a higher pressure into the discharge

The process of switching between pressure and volume in a multistage centrifugal pump is often referred to as ____________ ?

Change over

What can occur when the transfer valve is operated on a two stage pump?

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 hose line as well as injury to firefighters

During firefighter operations, if there is any question as to the correct position for the transfer valve in a multi stage pump it is better to operate in what mode?

Parallel or “volume” mode

A multi stage centrifugal pump will be capable of slut supplying 100% of its rated capacity at ______ psi, at ______feet of lift with _______feet of suction hose while drafting.

150 psi, 10’ of lift 20’ of suction hose

Many new pumpers use power operated transfer valves to operate multi stage centrifugal pumps. These transfer valves me operate at pressures as high as _________ psi?

200 psi

What is a Clapper valve?

A hinged valve the permits the flow of water in one direction only

What is a check valve?

An automatic valve that permits liquid to flow in only One Direction

Clapper valves are essential to the operation of multistage pumps. Should a valve stick opened or closed, Or be hampered by debris the pump will not operate in what mode?

Series or “pressure mode”

What are 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 where of the actual impeller or pump casing material

What is the amount of space maintained between the pump casing and the hub of the impeller?

Usually limited to .01 inch or less

What happens to the water inside a centrifugal pump if the discharging hose lines are shut off for long periods of time?

The churning water creates heat which could damage the pump.

What valves are newer model centrifugal pumps open to allow overheated water to circulate between the pump in the main water tank or into the atmosphere?

Thermal relief valves

How should operators dissipate heat from the pump if not equipped with a thermal relief valve?

Operators should ensure water is moving to the pump at all times. The driver can manually place a hand line into the water tank or open a discharge, tank fill or circulator valve

what type of seal is used where the impeller shaft passes through the pump casing that forms a tight seal without dripping and do not require periodic adjustment?

Mechanical seals

Older apparatus use packing rings around the impeller shaft. As packing rings wear the ______________ can be tightened in order to control any leaks and allow the pump to draft

Packing glands

What are auxiliary engine driven pumps?

Pumps powered by gasoline or diesel engine independent of the vehicle Drive engine

What type of pump is commonly used for airport rescue fire fighting vehicles, wildland Apparatus, mobile water supply Apparatus, trailer mounted fire pumps and portable fire pumps?

Auxiliary engine driven pumps

What is a power takeoff or PTO system

Mechanism that allows a vehicle engine to power equipment such as a pump, Winc, or portable tool. It is typically attached to the transmission

What is “pump and roll” capability

The ability of an apparatus to pump water while the vehicle is in motion

When operating a power takeoff driven fire pump, maintaining balance between speed and pressure is generally easiest when using what gear?

The lowest gear

What type of pump is typically driven through a gearbox and a clutch connected by a drive shaft to the front of the crankshaft?

Front mount pumps

What type of pump has a major disadvantage of being susceptible to freezing in cold weather due to their exposed position

Front mount pumps

What type of pump is vulnerable to damage from even minor impacts

Front mount pumps

What type of pumps are supplied power through the use of a split shift gear case located in the drive line between the transmission in the rear axle?

Midship pumps

With a mid ship pump, The gear ratio is set so that the impeller turns faster than the engine, usually at ________ to ______times as fast?

1.5 to 2.5 times as fast

When using a midship pump, the pump is engaged from inside the cab. The transmission is shifted into the correct gear and the speedometer will indicate between _____and ______ mph.

10 - 15 mph

What pump mount location has the disadvantage of the driver/operator possibly being more directly exposed to oncoming traffic than other pump not in positions

Rear mount pumps

Before being placed into service, apparatus piping systems must be capable of withstanding a hydrostatic test of __________psi.

500

Pumpers with a capacity of 500 GPM or less should have intake piping capable of flowing ________GPM.

250 gpm

Pumpers with the capacity greater than 500 GPM should have intake piping that is able to flow at least _______ GPM.

500 gpm

What occurs to atmospheric pressure when the priming pump removes all or most of the air from the pump?

A lower atmospheric pressure is created

In order to remove all air for drafting, all intake lines in a centrifugal pump are normally located _________ the eye of the impeller and no part of the piping is above this point.

Below

According to NFPA 1901, a sufficient number of 2 1/2 inch discharge openings must be provided in order to flow:

The rated capacity of the fire pump

All discharge valves should be designed and maintained so they are easily operable at pressures up to _______ psi

250 psi

Apparatus water tanks greater than 1000 gallons must be provided with at least a ________ inch tank so line.

2”

What allows the Apparatus water tank to be filled without making any additional connections when the pump is being supplied from an external source?

Tank fill line

What valve is connected to the discharge side of the pump in enables water to be dumped into the tank or outside the tank onto the ground?

Circulator valve

What type of valve permits for flow through the lines with a minimum of friction loss?

Ball type valves

Gate valves are most often operated by a?

A hand wheel

Butterfly valves are most often operated by?

Quarter turn handles

What is the purpose of having slow acting valve controls?

Minimize risk of damage caused by water hammer with large volumes of water are being moved

NFPA 1901 requires that all intakes or discharges that are _______ inches or greater be equipped with slow acting valve controls. This feature prevents the valve movement from open the closed in less than ________ seconds.

3 inches 3 seconds

On discharge fittings, drain valves provide a way to drain the hose side of the valve:

After the discharge valve and nozzles are both closed

What valve allows change over to the supply line to be made without interrupting fire streams?

Bleeder valve on gated intake

Automatic pressure control devices must not allow the pressure to exceed:

30 psi above the set level

Per NFPA 1901 pressure control devices must operate within how many seconds after the discharge pressure rises?

3-10 seconds

What type of automatic pressure control devices are sensitive to pressure change and have the ability to relieve excessive pressure within the pump discharge?

Relief valves

There are two basic concepts for pressure relief valves. Where are the two types of pressure relief valves located on the fire pump?

On the discharge side of the pump to control pressure delivered to the hose line. On the intake side on the pump to relieve excess pressure from the water supply.

What is the most common type of relief valve

Spring controlled pivot valve

Intake relief valves are set to open when intake pressure rises by what psi?

10 psi above set pressure

What type of valves are intended to reduce the possibility of damage to the pump and discharge hose lines caused by water hammer with valves or Nozzles are opened or closed too quickly?

intake pressure relief valves

What is a Pressure governor

Pressure control device that controls engine speed, eliminating hazardous conditions that result from excessive pressures

What type of automatic pressure control device is a pressure sensing element connected to the discharge manifold that controls the action of an electronic amplifier?

Electronic governor

What feature protects from cavitation by returning the engine to idle when the intake pressure drops below 30 psi?

Electronic governor

What type of priming device uses an oil supply or other type of fluid to seal the gaps between the gears in the case and fill any irregularities in the housing caused by sediment or debris?

Positive displacement primers

In general what is the preferred rpm range for activating the primer?

1000 to 1200 RPM

What type of primer is more environmentally friendly and does not require lubrication

Oilless primers

What type of primer uses the same principle as foam eductor so that exhaust gases from the engine are prevented from escaping to the atmosphere by an exhaust deflector

Exhaust primer

What type of primer prime the pump by connecting a line from the intake manifold of the engine to the intake of the fire pump with a valve connected in the line to control it?

Vacuum primers

What type of primary uses a compressor to supply in airline to a jet pump, which creates a Venturi effect the prime the pump using no moving parts or lubricants?

Air primers

Which pump panel instrument provides an indication of the vacuum present at the intake of the pump during priming?

Master intake gauge

Which pump panel instrument displays engine speed in revolutions per minute?

Tachometer

Which pump panel instrument shows that an adequate supply of oil is being delivered to the critical areas of the engine there’s power in the fire pump?

Pumping engine oil pressure indicator

Which pump panel instrument provides a relative indication of battery condition?

Voltmeter

Which pump panel instrument indicates actual pressure supplied the hose lines after the discharge valve

Master pump discharge pressure

Which pump panel instrument is used to increase or decrease the speed of the engine that is power in the fire pump?

Pumping engine throttle

Which pump panel instrument is used to operate the priming device when the pump or draft from a static water supply?

Primer control

Which auxiliary cooling device is inserted into one of the hoses used in the engine cooling system so the engine coolant must travel through it as it circulates through the system?

Marine cooler

Which auxiliary cooling device has water supplied by the fire pump pass through a coil or tubing mounted inside the cooler so it is immersed in coolant?

Immersion type auxiliary cooler