Flashcards in Chapter # 10 Fire Pump Theory Deck (160):
Are the majority of water systems unable to maintain adequate pressure in the hydrant system for effective fire fighting.
Yes, that is why we need fire pumps.
What was the earliest type of pump used in the fire services?
Hand operated piston pumps.
A positive action takes place. All water and air are forced out of the pump body with each operating cycle.
Positive displacement pumps
Do modern apparatus have a positive displacement pump?
Yes, this allows drafting.
Does not use positive action; rather it depends on the velocity of water produced by centrifugal force to provide the necessary pressure.
What are two types of positive displacement pumps?
Piston and Rotary
The forward stroke causes water (or air) to be discharged, and the return stroke causes the pump to fill with water (or air) again. This is known as what?
Single action piston pump.
Adding additional valves to piston pumps can produce a usable fire stream. This is known as what?
Double acting piston pump. Because it both receives and discharges water on each stroke of the piton. (up and down).
What is the output capacity of a piston pump determined by?
The size of the cylinder and the speed of the piston travel.
It is more practical to build........... pumps than one large single cylinder pump.
What can help to minimize the pulsing of a piston pump fire stream?
A air chamber.
Name some reasons the piston pump has been faced out as a high capacity fire pump.
Pulsating stream. Prone to wear. Can not pump dirty water (unless bronze).
Although piston pumps are no longer used as high capacity fire pumps, are they still used to provide high pressure fire streams? In what applications?
Yes, Muticylinder, PTO driven pumps provide pressure up to 1,000 psi. for high pressure fog lines or to inject foam concentrate into a water line or manifold at a higher pressure then what the water pump is creating. All provide a dependable relief valve.
The simplest of all fire pumps from the standpipe of design.
Used in the past as the main fire pump. Used today as small capacity booster type pumps, low volume high pressure, and priming pumps.
Name two types of rotary pumps.
Rotary vane or Rotary gear.
Has two gears that rotate in a tightly meshed pattern inside a water tight case. Rotate from the intake to the discharge. Creates pockets of water or air when the tooth's come in contact with each other.
Rotary Gear Pump
What determines the amount of water that a rotary gear pump can produce?
The size of the pockets in the gears and the speed of rotation.
Are rotary gear pumps prone to damage? Can they pump dirty water.
Yes, Can wear very easily from pumping dirty water.
Constructed with movable elements that automatically compensate for wear and maintain a tighter fir as the pump is used. One of the most common types of priming pumps on apparatus. Rotor is mounted off center in a housing. As the rotor turns the vanes move against the casing. The intake side of the casing is larger then the discharge side of the casing.The self adjusting feature make it much more efficient in pumping air then a standard rotary gear pump.
Rotary Vane Pump.
How are Rotary Pumps powered?
Either a small electronic motor or through a clutch that extends off the apparatus drive shaft.
A nonpositive displacement pump because it does not pump a definite amount of water with each revolution. Rather, it imparts velocity to the water and converts it to pressure within the pump itself.
What are the two parts of a centrifugal pump?
Impeller and Casing.
Transmits energy in the form of velocity to the water.
Collects the water and confines it in order to convert the velocity to pressure. Then directs the water to the discharge of the pump.
What rpm does the impeller generally rotate at?
2,000 to 4,000 rpm.
To some extend the volume capacity of a pump is dependent on what?
Th size of he eye of the impeller. The larger the eye the greater the flow capacity.
Why is the impeller mounted off center in the casing?
Creates a water passage that gradually increases in cross-sectional are as it nears the discharge outlet of the pump. This section of the pump is called the Volute.
What are the three main factors that influence a centrifugal 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.
T or F In a centrifugal fire pump, the greater the volume of water being flowed, the lower the discharge pressure.
T or F In a centrifugal fire pump, the greater the speed of the impeller, the greater the pressure developed.
True. This increase is approx equal to the square of the change in impeller speed.
Doubling the speed of the impeller results in what?
Four times as much pressure if all other factors remain constant.
Because the incoming pressure adds directly to the pressure being developed by a centrifugal pump, incoming pressure changes are reflected where?
In the discharge pressure.
Name the two basic types of centrifugal pumps.
Single stage and Two stage.
What is a double suction impeller.
A impeller that take water in from both sides. This was done to cancel out the reaction of only having water enter from one side. With it entering on both sides the reaction has no effect. It also provides a larger water way for the movement of water. Provides a hydraulically balanced pump. Used in high capacity pumps with large impellers.
What is series? What is parallel?
Both are stages of a muti-stage fire pump. Series = Pressure, Parallel = Volume
What is the capacity of a pump in parallel (volume) position?
Each impeller is capable of delivering its rated pressure while flowing 50% of the rated capacity; therefore, the total amount of water the pump can deliver is equal to the sum of each of the stages.
Front mount pumps, power take off, separate engine driven, and midship transfer pumps use a single intake impeller and a simple casing to provide capacities up to how many gpm?
When pumping in series (pressure), what is the increase in pressure that is provided by the first impeller before moving to the second impeller?
What is the total volume of water limited to when pumping in series (pressure)?
What one impeller can provide.
The process of switching between volume and pressure?
When do most manufacturers today recommend that a pump be switched to volume?
When it is necessary to flow more than 2/3 of the rated volume capacity.
In most cases, what is the maximum net pump discharge pressure that a transfer valve should be operated at?
Can provide 100% of the rated volume at 150 psi.
How is the transfer valve operated on many two stage fire pumps?
Manually. Especially on older apparatus.
How might a transfer valve be operated on a newer apparatus?
With a power operated transfer valve.
How can a power operated transfer valve be powered?
Electricity, Air pressure, Vacuum from the engine intake manifold (gas engine only), water pressure.
T or F Many power operated transfer valves operate at pressures as high as 200 psi.
What has been done in the past to gain higher pressures?
A series of four impellers to develop pressure as high as 1,000 psi. A single stage pump that takes from a multistage pump, when pressures higher then 250 psi are needed.
The pressure in the volute is much higher then it is in the eye of the impeller, so a very close tolerance must be maintained between the pump casing and the hub of the impeller. This opening is usually limited to what? Any increase in the opening lessens the pumps effectiveness.
.01 inch or less.
What is the first indication of wear to a centrifugal pump?
When increase engine rpm is required to pump the rated capacity in pump test.
What are some newer apparatus centrifugal pumps equipped with to prevent damage due to the build up of heat?
Thermal relief valve (sends water to tank or atmosphere).
If a driver places their hand on the direct pump intake pipe and it is warm, what should be done?
Open a discharge or a circulator valve.
What is used to maintain a semi tight seal at the point where the gear shaft passes through the pump casing?
What is the most common type of packing ring made of?
Rope fibers impregnated with graphite or lead.
What kind of packing rings are not adjustable?
Ceramic or mechanical.
What is used to provided cooling and lubrication to packing rings?
A lantern ring. A small amount of water leaks out around the packing to prevent heat build up.
If a pump has been keep dry for some time, what should be done before adjusting the packing rings?
It should be ran full.
What is a problematic situation for a mechanical seal over a packing ring?
If the freeze they may be damaged and have to be replaced.
What is the most important consideration when deciding on a pump mounting and drive system?
The use that the system receives.
Pumps that are powered by a independent gasoline or diesel engine .
Auxiliary Engine - Driven Pumps
What are the most common applications for auxiliary engine driven pumps?
ARFF. Wild land apparatus. Mobile water supply apparatus. Trailer mounted fire pumps. Portable fire pumps.
Max amount of flexibility. Ideal for pump and roll. May come as a skid mount unit that provides 500 gpm. ARFF and trailer mounted may be rated up to 4,000 gpm or more.
Auxiliary Engine Driven Pumps.
Pump is driven by a drive shaft that is connected to the power take off on the chassis transmission. Most common on initial attack, wild land, and mobile water supply apparatus. Have become increasingly popular on structural pumpers.
Power Take off Drive PTO
A PTO is powered by a idler gear in the transmission. The speed of the shaft is independent of the drive gear but is under control of the clutch. Does allow pump and roll but not as effective as a the separate engine unit. When the clutch is engaged to brake or change gears, what happens to the pump?
The pump also stops turning.
What is the pressure determined by when using a PTO?
The speed of the engine.
Drivers who are also pumping lines with a PTO should have a pressure gauge in the cab and drive according to what? and not the speedometer.
The pressure gauge.
How can the balance between speed and pressure be maintained with a PTO?
Drive in lower gears.
Traditional PTO's allow what GPM at what horsepower?
500 gpm at 95 horsepower.This is the max.
Mounted on a extended front bumper. Its max rated capacity depends on the limitations of the apparatus engine, typically can go as high as 1250 gpm. Can be used in the same manner as PTO pumps for pump and roll operations.
Front mount pumps
What are some disadvantage of a front mount pump?
Gauges and pump are susceptible to freezing. Can obstruct air flow through the apparatus radiator causing over heating. Vulnerable position in the event of a collision. Operator is in a bad position (lock should be provided for the transmission controls).
Pump is mounted laterally across the frame behind the engine and transmission. Power is supplied to the pump through the use of a split shaft gear case (transfer case) located in the drive line between the transmission and the rear axle. Most fire departments use this arrangement.
What is the typically ratio of the impeller turn to the engine?
1 1/2 to 2 1/2 times as fast.
What is the maximum capacity of a midship pump determined by?
The engine horsepower and the size of the pump.
What do most apparatus (not newer ones) register on the speedometer when the pump is in gear?
What may happen if a transmission is not in neutral when engaging the pump on a midship pump?
The transmission may lock up and the engine may stall.
Driven by a shaft from the front of the vehicles engine. Turns a hydraulic pump that drives a midship mounted or rear pump up to 1,000 gpm. Can be used for stationary or pump and roll. Speed of engine don't affect pump output. Pump can reduce power available for driving.
What are advantages of a rear mounted pump?
Weight distribution. More compartment space.
What are the disadvantages of a rear mounted pump?
Operator may be exposed to traffic. (can be offset by placing control on the rear side).
How is a rear mount pump powered?
Either a spit shaft transmission or a PTO.
NFPA 1901 requires that pump piping be of corrosion resistant material. What materials or combination of materials may be found in a pump?
Cast Iron, Brass, Stainless Steel, Galvanized Steel. And sometimes Rubber.
The pump and piping system of a apparatus must be able to with stand a hydro-static test of what, before being put into service?
What are the primary components of a piping system on a apparatus?
Intake piping. Discharge piping. Pump drains, Valves.
What are the two ways water can enter a fire pump?
Piping from the tank. Piping that is used to connect to a outside source.
NFPA 1901 requires that piping from a water tank be sized so that a pump with a capacity of 500 gpm or less can flow how much gpm? And pumps with a capacity greater then 500 gpm can flow what?
500 or less = 250 gpm
Greater than 500 = 500 gpm
Why is a primer tapped into the pump at a high point on the suction side of the impeller eye? Where are the intake line located in relation to the eye of the impeller?
Make it possible to get all the air out of the pump. The intakes are located below the eye of the impeller so that prime is not lost. (Except for a tank to pump line, it may be above, but gravity is moving the water under natural pressure.
Why is a intake line square in shape as it enters the pump.
To eliminate the vortex that may occur in circular pipe.
What intakes may not be able to meet the rated capacity of a pump?
Rear and front intakes on midship pumps.
NFPA 1901 requires that enough 2 1/2" discharges be provided to flow what gpm?
The rated capacity of the pump.
As a minimum all fire apparatus with a rated capacity of 750 gpm or more must be equipped with how many 2 1/2" discharges? What about a pumper rated lower then 750 gpm?
750 gpm or greater = 2
Less then 750 gpm = 1
Where can discharges larger than 2 1/2" not be located?
On the pump panel.
Discharges that you can connect 1 1/2", 1 3/4" or 2" pipe to must be plumed with what size of pipe?
All pump valves should be designed to be easily operable at up to what psi?
What is another name for the pump-to-tank line?
Tank fill line
NFPA 1901 requires that apparatus with a water tank that is less then 1,000 gallons in size to have a tank fill line that is how big?
NFPA 1901 requires that apparatus with water tank that is 1,000 gallons or larger have a tank fill line that is how big?
Why can overheating still be a issue in a mutistage pump even if the tank fill line is open? What is a better option to control heat build up?
Because it pulls water from the first stage. A circulator valve.
Same function as a circulator valve. Diverts water from the discharge into the tank. Piping is cooper and small. Flows are only 10-20 gpm. May not be sufficient in prolong incidents, high pressures.
Booster line cooling valve (bypass)
Most common type of pump valve. Permits full flow through the pipe when open with minimal friction loss. Operated by push-pull handles ( T-handles) or quarter turn handles.
A valve most commonly used on large intake or discharges.
Gate or butterfly valves.
NFPA 1901 requires all valves on intakes or discharges that are 3" or larger be equipped with slow acting valve controls. What does this do.
Prevents the movement from fully open to fully closed or vice versa in less then 3 seconds.Minimizes water hammer risk and damage.
Where are drain valves located for most connection to the pump?
On the line side of the control valve.
All drain lines are connected to it. When activated it drains all lines and the tanks.
Master drain valve.
When draining a pump why should a discharge valve be opened?
Because the vacuum in the pump will hold water in.
NFPA 1901 requires some type of pressure control device to be part of any fire apparatus pumping system. The device must operate within 3-10 seconds after the discharge pressure rises and must not allow the pressure to exceed what psi?
30 psi above the set level.
Why is some type of automatic pressure regulator essential?
To ensure the safety of personnel operating hoselines.
What must illuminate on the pump panel when the pressure control system is in control?
A yellow indicator light. (except on apparatus with automatic governors).
What are the to basic concepts of pressure relief valves?
Those that relief pressure on the discharge side, and those that relief pressure on the intake side.
A discharge pressure relief valve uses a adjustable spring loaded pilot valve that bypasses water from the discharge to what?
The intake chamber of the pump.
Uses a diaphragm and a spring that can be adjusted to meet a certain pressure. As long as the water pressure on the diaphragm is less then the spring the valve stays closed. When the water pressure on the diaphragm exceeds the springs setting the valve opens. This causes water to dump back into the pump intake.
Spring controlled pilot valve.
A discharge relief valve that uses a pilot valve, but also uses a churn valve. The churn valve opens allowing water to move from the discharge side to the inlet side of the pump. These types of relief valves are quick to react but slow to reset.
Discharge pressure relief valve.
Intended to reduce the possibility of damage to the pump and discharge hoselines caused by water hammer.
Intake pressure relief valves.
What are the two basic types of intake relief valves?
One is supplied by the manufacturer and is an integral part of the pump. The other is a add on device that is screwed onto the pump intake connection.
What is the recommended setting of a intake pressure relief valve?
10 psi above the desired operating pressure.
What are two other features of a add on type intake pressure relief valve?
Manual shut off valve. Bleeder valve.
Regulate the power output of the engine to match the pump discharge requirements.
Pressure can be regulated on a centrifugal pump by a mechanical or electronic governor that is pressure activate to adjust the what?
What should a piston assembly governor be set at when drafting or pumping from a tank?
Draft (closed). Causes water to discharge to the intake side of the pump.
What should a piston assembly governor be set at when pumping from a hydrant or external pressurized source?
Hydrant (open). Water is discharged to the ground or the tank if a check valve is in place.
Uses a pressure transducer. Controls the action of a electronic amplifier that compares pump pressure to a electrical reference point. Changes throttle setting when necessary by adjusting the amount of fuel supplied to the engine. Will maintain any pressure that is set on the control knob above 50 psi. If pressure drops below 50 psi it returns the engine to idle speed. Cavitation protection mode returns the engine to idle when the pressure drops below 30 psi. Very accurate and very quick. Eliminates the need for discharge relief valves but not intake relief valves.
What is a disadvantage of a mechanical governor?
A closed discharge line can reduce the rpm of the engine to lower the pressure. This in turn lowers all discharge line working pressures. This does not occur with electronic governors. Electronic governors adjust the rpm, but maintain the same discharge pressure on the lines that are still flowing.
Name the three categories of priming devices.
Positive displacement. Exhaust. Vacuum.
The type of primer used by most fire apparatus. Small versions of rotary vane and rotary gear pumps.Most rotary vane type are powered by electronic motors but can be powered by the pump transfer gear.
Positive displacement primer.
Why do most primers use a oil/fluid?
Seals gaps between the gear and case. Acts as a preservative and minimizes deterioration of the metal parts by inhibiting corrosion when the pump is not in use.
What should be checked in the oil/fluid line that goes from the reservoir to the pump?
What is the general engine rpm that the primer should be operated at?
1,000 to 1,200 rpm. Activate at throttle then increase speed.
Still found on some small skid mounts and older apparatus. Operates on the same principle of a foam educator. Exhaust gas is diverted to a chamber where the velocity of the gas passing through causes a venturi. Requires high RPM's. Not very efficient. High maintenance.
The simplest type of primer makes use of the exiting vacuum in the intake manifold of a gasoline engine. Can cause water to enter the intake manifold causing engine damage (can be prevented with a check valve). Engine vacuum is max near idle speed, the primer works best at low RPM's.
NFPA 1901 requires these controls and instruments to be located on the pump panel as a minimum.
Master intake pressure indicator. Master discharge pressure indicator. Tachometer. Coolant temp. Engine oil pressure. Voltmeter. Pump pressure controls (discharge valves). Engine throttle. Primer. Water tank to pump valve. Tank fill valve. Water level indicator.
What gauge / gauges are recommended to be on the pump panel but not required by NFPA 1901?
Fuel gauge. Auto transmission temp gauge.
What are two other names for a master intake gauge?
Vacuum or compound gauge.
A intake gauge must be able to measure positive pressure or a vacuum. What are the calibration points on the gauge?
Positive pressure = 0-600 psi
Vacuum (negative side) = 0-30 inches of mercury.
At what point in a vacuum reading has a pump neared its capacity and no more lines should be added?
What is a master discharge indicators calibration points?
Standard = 0-600 psi
Pumper that supplies high pressure fog streams = 0-1,000 psi.
Where is the master discharge taking its reading?
As the water leaves the pump but before it reaches the individual lines gauge.
Why are external connections to the master intake and discharge gauge requires?
To allow for testing and calibration for service testing of the pump.
Where would you find the RPM's that where required to get the pump to its rated capacity when it was initially tested?
On a identification plate on the pump panel.
What does a increase in the required RPM's to meet pump capacity indicate?
Pump wear and a possible need for repairs.
What is bad about a engine that operates to cool?
It is not efficient.
What is a indication of pending engine problems?
A significant change in the oil pressure indicator reading.
The pump panel may be equipped with an audible or visual indicator that warns the operator when the pump overheats. What is this indicator called?
Pump overheat indicator
When is the top voltage available indicated to the operator on a voltmeter?
Before the engine is started.
Where are Pump pressure indicators (Discharge gauges) installed?
The outlet side of the discharge after the valve.
If a line is shut down what pressure will be indicated on the Pump pressure indicator (discharge gauge)?
The same as the master discharge gauge.
NFPA allows flowmeters to replace some gauges. What are some gauges that must remain?
The master intake and discharge gauge.
A engine throttle on a pump panel that turns is called what?
throttle knob (vernier)
What form may the primer control come as?
Push button. Toggle switch. Pull lever.
What should interior crews do if the pumper water supply is exhausted prior to an external water supply being established?
What is the most common type of water level indicator?
A series of lights that shows tank level in 1/4 increments.
What are other water tank level indicators other then the lights?
A sight tube. Digital readouts.
What is the most reliable way to ensure a full tank at the begging of each day?
If a pumper has a foam or CAFS system where are the controls for the system typically located?
On the pump panel.
What is the primary function of auxiliary coolers?
To control the temp of coolant in the engine during pumping operations.
Name the two types of auxiliary coolers commonly found on older apparatus.
Marine type. Immersion type.
Inserted into a hose in the cooling system, forcing coolant to travel through it. Contains a number of small tubes that are covered by a water jacket provided by the pump. Water flows past the tubes, carrying heat with it. A valve is provided at the pump panel to control the amount of water that is sent to pass over the tubes.
Marine type auxiliary cooling device.
Coolant passes through the body of the cooler. Water, supplied by the pump, passes though a tube that is immersed in the coolant. A valve is also provided on the pump panel to control the flow of water to the cooler.
Immersion type auxiliary cooling device.
Some manufacturers also prove on of these on a auxiliary cooling device. It should only be used in emergencies due to the fact that water in the pump will enter the radiator when used.
A radiator fill valve.
Why should a radiator fill valve be opened a very small amount when used?
Excess pressure could result in bursting.
What should be done ASAP if the radiator fill valve is used.
Cooling system serviced.