Pumps Flashcards
What is the definition of a pump?
A pump is a mechanical device driven by an external source used for transmitting energy to fluids.
What is the definition of a primer?
Removing the air from the hard suction so you can create flow and lift water.
How would you deal with a branch out of control?
Shout ‘branch out of control’
Pump operator will immediately reduces the revs on the pump OR if multiple hose lines are in use start closing the effected delivery.
Two firefighters, with visors down, will crawl along the hose line to the branch keeping their hands on the hose line as they proceed.
Once at the branch it can be held in position and closed down.
If ‘A’ type branches are in use then either lay on the branch until it is shut down at the pump OR carefully pick the branch up and assume the normal working position.
What features must a fire service pump have?
Self-contained
Light in weight
Able to handle large quantities of water
Able to produce high pressures
Reliable
Easy to operate and maintain
What are the features of a positive displacement pump?
Pumps both liquids and gases
Highly efficient 85%
No priming required
What are the features of a centrifugal pump?
Pumps only liquid
Provides a constant flow
Required a priming device to remove air from the system
What different types of pumps are used in the fire service?
Positive displacement (stirrup) pump
Centrifugal pump
Peripheral pump
Exhaust Gas Ejector pump
What does the PTO button do?
Directs engine power away from the road wheels to drive another piece of equipment such as the fire pump.
What are examples of centrifugal pumps?
Main pumps
Light portable pumps
How do centrifugal pumps work?
Water is thrown to the outside of a pump casing (volute) by the central spinning wheel (impeller). The faster the impeller rotates, the higher the pressure created.
What are the spokes called on the impeller?
Vanes
What does the volute do?
Channels water from the periphery of the impeller to the outlet.
Reduces the velocity of the water as it passes through
Reduces the turbulence of water created by the impeller
How does water flow through a pump?
Water enters through the eye of the pump in the centre
Spinning impeller imparts energy driving the water towards the edge
Water enters the volute increasing in pressure
Lost water in the centre is resupplied by either pressure fed or suctioned water.
What are the characteristics of a centrifugal pump?
At any given speed where there is no
flow ie closed delivery, pressure is at a
maximum
Pressure decreases as the delivery
valves are opened and the flow increases
When pump speed increases pressure and flow increase
When suction lift increases pressure and flow decrease.
What are the advantages of centrifugal pumps?
Simple to maintain
Can be run against closed deliveries without damage
Light and compact relative to their output
Can be driven directly from an internal combustion engine
What are the disadvantages of centrifugal pumps?
Require a separate priming device to work from open water
Have a lower efficiency than a positive displacement pumps
What do peripheral pumps do to pressure?
Allow greater pressures based of a smaller centrifugal pumping unit
What are peripheral pumps used for?
Hose reel pumps
What is the duty point of a peripheral pump?
227 Litres per minute at 24 bar
What are the benefits of a peripheral pump?
Produces high pressures at relatively low running speeds, saving on wear and tear.
Can be mounted on the same shaft as the centrifugal pump
How do peripheral pumps work?
Water enters a tube surrounding
the guide vanes, drops down to
the base and is thrown out
several times to the periphery
With each spiral action adding
force and pressure to the water
prior to it leaving via the outlet.
How would you overcome a defective primer?
Blanking cap or collecting head
Bucket and water
Secondary pump
What is the flow rate for a high pressure hose reel?
110 LPM
What is the flow rate of a 45mm hose?
300 LPM
What is the flow rate of a 70mm hose?
600 LPM
What is the friction loss of a high pressure hose reel jet?
3 bar per 20m length
What is the friction loss of a 45mm hose?
0.4 bar per length
What is the friction loss of a 70mm hose?
0.2 bar per length
What is the friction loss per 1m vertical rise?
0.1 bar
What is the pressure of a hose reel jet?
30 bar
What is the pressure of a main jet?
4 bar
When are pump hand signals not to be used?
Two or more pumps in use
More than 2 branches working from the same pump
Poor visibility/at night.
What could cause increased DELIVERY pressure?
- Closing down of branches
- Debris on top of delivery hose
- Vehicle parked on delivery hose
- Bad kink in delivery hose
- Stones blocking the nozzle.
What could cause decreased DELIVERY pressure?
- A burst length of delivery hose
- A branch being opened / flushed out.
- Vehicle moving off of delivery hose
- Debris being removed from delivery hose
- Bad kinks being straightened out.
What could cause a failure of water from a pressure fed supply?
- Failure of supply - fractured main or burst supply length (hose)
- Choked conical strainer
- Over running the supply.
What could cause an increasing vacuum reading?
- A drop in water supply level
- Partially blocked strainer
- Pump working harder (more water delivered)
What could cause a decreasing vacuum reading?
- A rise in water supply level
- Pump working easier (less water
delivered)
What could cause a very high vacuum reading but no water?
- A blocked metal or basket strainer
- A collapsed/blocked suction hose.
When working from open water, what could cause no vacuum reading?
- Strainer not adequately submerged
- Loose or faulty suction joints
- Open drain cocks
or deliveries incl hosereel - A defective primer
- Air leaks in suction hose.
What is cavitation?
Cavitation is the appearance of vapour bubbles
within the pump casing.
What causes cavitation?
a) There is a reduction of incoming pressure
caused by over running the supply, or
b) When water within the casing is allowed to boil
How would you identify and overcome cavitation?
Cavitation can be identified by a rattling noise
within the pump, or crackling jets. The pump
operator should ease back slightly on the throttle to
correct this.
What would happen if you don’t submerge the suction strainer sufficiently?
A vortex will occur and air will be entrained into the pump (losing your prime)
What would cause a cracking jet?
- Strainer insufficiently submerged
- Slight leak on suction side of pump.
What would cause a failure to prime and a high vacuum reading?
- A blocked metal or basket strainer
- A collapsed/block suction hose
What would cause an increase in vacuum reading (open water pumping)?
- Falling level of static water
- Increase in water being delivered
- Partial blockage of strainer
What would cause an decrease in vacuum reading (open water pumping)?
- Rise in level of water supply
- Less water being delivered
What would cause an increase in delivery pressure?
- Blockage in hose, may be caused by vehicle parking on
hose - Blocked jet, caused by small stones
- Hand controlled branch closed
- Kinks in hose
What would cause a decrease in delivery pressure?
- Burst in delivery hose
- Coupling disconnected
- Hand controlled branch opened.
