Chapter 9 Flashcards
Positive displacement pumps are?
Self priming, deliever a definite volume of water or air. And exhaust air from the pump and deliver water
Positive discharge pumps are called “constant flow machines” because?
They produce the same flow at a given speed regardless of discharge pressure. All the air and water are forced out of the pump with each operating cycle
What type of pump are modern fire apparatus equipped with as their main pump?
Centrifugal pump
How do centrifugal pumps create pressure needed to achieve proper drainage charge pressure?
Depends on the velocity of the water produced by the centrifugal force to provide the pressure
What are positive displacement pumps used for in modern apparatus?
They are used as priming devices to get water into the centrifugal pump during drafting operations
Piston pumps can provide pressures up to what psi 1000 psi?
Piston pumps?
What type of pump from the standpoint of design is the simplest type of pump?
Rotary pumps
What are rotary pumps used for in modern apparatus?
Confined to small capacity booster type pumps low volume high pressure pumps and priming pumps
How do rotary gear pumps work?
Consist of two gears that rotate in a tightly meshed pattern inside a watertight case. They are constructed to contact each other and are in close proximity to the case. This allows it to force air or water out of the pump with each gear creating airtight or watertight pockets
Rotary gear is what type of pump because each pocket in the gears contains a definite amount of water which is forced out of the pump each time the gears turn with a positive action
Positive displacement pump
What are most gear pumps gears are made of ___ and pump casing is made of?
Bronze or another soft metal for the gears, and a strong alloy such as cast metal for the pump casing
Rotary vane pumps are constructed by?
Moveable elements that automatically compensate for wear maintenaning a tighter fit with closer clearances as the pump is used.
What is one of the most common types of pumps used to prime a centrifugal fire pump?
Rotary vane pump
What feature makes the rotary vane pump much more efficient than the rotary gear pump at pumping air?
The self adjusting feature. When the vane that is in contact with the casing becomes worn, centrifugal force causes it to extend further causing it to maintain a tight fit
What is a centrifugal pump classified as?
Non displacement pump as it does not pump a definite amount of water with each revolution
The volume capacity of the pump is dictated by?
The size of the impeller
The increase in pressure is roughly equal to the square of the change in the?
Impeller speed. Double the impeller speed, will result in 4 times as much pressure
Is a centrifugal pump able to pump pump air and be self priming?
No, it is not able to do do either
What are the two basic types of centrifugal pumps used in the fire service?
Single stage and multi stage.
A double suction impeller is used to?
Minimize lateral thrust of large quantities of water entering the eye of the impeller. The double suction takes water in from both sides the reaction being equal and opposite cancels out the lateral thrust
Why is radial thrust cancelled out in double suction impellers?
Water is removed at two places and traveling in opposite directions.
This part helps create a hydraulically balanced pump that reduces stress on the pump, vehicle chassis, and helps lengthen the service life of the pump and apparatus.
Double suction impeller
What feature makes multi stage pumps more efficient?
The capability to connect the stages in series for maximum pressure, or in parallel for maximum volume by use of a transfer valve
Series means?
Maximum pressure
Parallel means ?
Maximum volume
The process between switching over from pressure and volume is known as?
Changeover
What should be done if making any changeover on the fireground?
Carefully coordinate with attack crews so that they will be prepared for a slight interruption during the transfer
If there is any question as to the correct position for the transfer valence it is best to operate in?
Parallel(volume) rather than series(pressure)
What is good to remember as far as your limitations for series(pressure) mode?
The volume of water available while operating in the pressure position is limited to the amount that one impeller can supply
How can you check the operation of a clapper valve?
Checked by removing the strainer from a large intake opening and reaching into the pump with a long wooden dowel or similar type of rod. The flapper valve must be able to swing freely
A very close tolerance must be maintained between the pump casing and the hub of the impeller. This opening is usually limited to?
.01 inch any increase in the opening lessens the effectiveness of the pump
What is an initial indication of wear on a pump?
During pump test when increased engine rpm is required to pump at the rated capacity
To restore the pumping capacity without replacing the entire pump what can be replaced?
Wear rings or clearance rings in the pump casing may be replaced to maintain the preferred spacing between the hub of the impeller and the pump casing.
In which pump will no harm result from shutting off all the pump
Discharges for a short period of time?
Centrifugal pump, in a positive displacement harm will occur
What should be done if the driver operator touches the pump panels and it is warm to the touch?
Open a discharge, tank fill, circulator valve or thermal relief valve if equipped
What type of seals should not be allowed to run waterless for any length of time or else they will overheat and become damaged?
Mechanical seals
The most common type of seal packing material is composed of?
Rope fibers impregnated with graphite or lead
Some centrifugal fire pumps are equipped with what type of seals that are not adjustable?
Ceramic or mechanical seals
In order to overcome the problem of hot packing rings coming into contact with the shaft, this part is used?
Latern or slinger ring used as a spaced, is supplied with the packing to provide cooling. A small amount of water leaks out around the packing and prevents the buildup of excessive amounts of heat that may score the shaft
The packing in the pump only receives lubrication when?
The pump is full and operating under pressure
What type of pump seal material provides superior resistance to warping, stretching, and corrosion?
Ceramic pump seals
Most common applications for auxiliary engine driven pumps are?
Airport rescue fire fighting, wildland fire apparatus, mobile water supply apparatus, trailer mounted fire pumps, portable fire pumps
Rear engine pto design has what advantages?
The versatility of pump and roll capabilities, the mounting of the pump offers opportunity for a shorter wheelbase, additional room for compartments, as well as crosslays packed lower on apparatus body
If apparatus is used for pump and roll operations, and hose lines are in operations the driver operator should drive the vehicle using what gauges?
Pressure gauge rather than the speedometer
What is one major disadvantage of the front-mount pump?
The susceptibility of the pump and gauges freezing in cold weather due to their exposed position
The impeller turns faster than the engine, usually how many times as fast?
Usually 1 1/2 to 2 1/2 times as fast
What are some advantages of rear mount pumps?
More even weight distribution on the chassis, more usually compartment space.
NFPA 1901 requires all components of the piping system be made of?
Corrosion resistant materials, most are constructed of cast iron, brass, stainless steel, or galvanized steel, and may include rubber hoses.
The piping system and the fire pump itself must be capable of withstanding a hydrostatic test of what Psi before being placed in service?
500 psi before being placed in service
NFPA 1901 states pumpers with a capacity of 500GPM or less should have piping capable of flowing how many gpms?
250GPM
NPFA 1901 states pumpers with a capacity greater than 500 GPM should be able to flow at least how many GPMs?
At least 500 GPMs
Discharges greater than what diameter may not be located on the pump operators panel?
Greater than 2 1/2 inches
As a minimum all fire apparatus with a rated pump capacity of 750 GPM or greater should be equipped with at least how many 2 1/2 discharges
At least two
A minimum of what size piping, valves, and elbows must be used to supply the discharges where 1 1/2, 1 3/4, or 2” handlines are attached.
A minimum of 2 inch
All valves should be designed and maintained so that they are easily operable at pressures up to what psi?
Up to 250 psi
According to NFPA 1901 apparatus equipped with tanks of less than 1000gallons must have a tank full line of at least what diameter?
At least 1 inch diameter
According to NFPA 1901 tanks greater than 1000 gallons must have at least what size diameter tank fill line?
At least 2 inch diameter tank fill line
What is the most common type of valve that permits the full flow of water through a line with a minimum friction loss?
Ball type valve
According to NFPA 1901 all intakes or discharges that are 3 inches or greater be equipped with?
Slow acting valve controls.
This prevents the valve from open to closed in less than 3 seconds, to minimize the risk of damage by water hammer
According to NFPA 1901 all intakes or discharges that are 3 inches or greater be equipped with?
Slow acting valve controls.
This prevents the valve from open to closed in less than 3 seconds, to minimize the risk of damage by water hammer
According to NFPA 1901 some type of pressure control device must be apart of any fire apparatus pumping system. This device must operate within how many seconds after the discharge pressure rises and restricts pressure from exceeding what psi above the set level?
Must operate within 3-10 seconds after the discharge pressure rises and restricts pressure from exceeding 30 psi
What are the two basic concepts for pressure relief valves?
Those that relieve excess pressure on the discharge side of the pump, and those that relieve pressure on the intake side of the pump
What is the most common relief valve ?
Most common relief valve uses a spring controlled pilot valve
I take pressure relief valves are intended to ?
Reduce the possibility of damage to the pump and discharge hose lines caused by water hammer when valves or nozzles are closed too quickly.
The electronic governor also features cavitation protection by returning the engine to idle when pressure drops below?
Below 30 psi
What should the driver operator do to minimize wear on the mechanical clutch when attempting to obtain a draft?
Activate the primers with the engine at idle speed and then increase the throttle to the specified rpms
True or false: most new pumpers are equipped with oil less primers?
True
How do exhaust primers work?
In order to create this vacuum high rpm’s are required. Gases are converted into a chamber where their passing velocity creates a vacuum. The exhaust primer requires a great deal of maintenance in order to remove the carbon deposits accumulated in the primer
How do vacuum primers work?
A line is connected from the intake manifold o
What does a gradual increase in the amount of rpm required to pump the rated capacity indicate?
Indicates wear in the pump and possible need for repair
As an engine that operates too cool is? And an operating temperature that is too high may result in?
Too cool means not efficient.
Too high temperature means damage may result to mechanical parts.
If the oil level is too low, the oil pump will?
Be unable to maintain the proper amount of pressure
What does the voltmeter tell the driver operator?
The relative indication of battery condition. It measures existing voltage in an electrical system. Top voyage available when battery is fully charged and drop in voltage as electrical accessories are used.
What does the anmeter indicate to the driver/operator?
It indicates the status of the vehicles alternator and charging system. It indicates the amount of electrical current being drawn from and provided to the vehicles battery.
If the nozzle is shut down and the hose line being supplied, the individual pressure gauge for that discharge reads?
The same as the master pressure gauge because there is no flow through the valve to reduce the pressure. The gate valves should not be readjusted until water is flowing again.
What is another name for a throttle knob?
A vernier, it can be turned clockwise or counter clockwise to achieve desired pressure
What is the name of the throttle used on commonly on newer apparatus?
Automatic throttle controls, which use up and down arrows.
What are the two types of auxiliary coolers?
Marine cooler, and immersion cooler
Does water and coolant mix together or get contaminated when using either marine or immersion coolers?
No, they are both designed to not mix water and coolant.
If apparatus is equipped with radiator fill valves, When should it be used, and what must be done after using this feature?
It should be operated only in an emergency, as coolant will become diluted due to water from the pump being circulated to the radiator to cool the engine. The cooling system should be flushed and refilled with fresh coolant as soon as possible after this operation.
