Pumps Flashcards
What is PTO
Power take off
Directs power away from the engine to the pump
Requirements of a pump (7)
Reliable
Self contained
Able to handle large quantities of water
Work on a closed delivery system
Easy to operate
Easy to maintain
Able to produce fairly high pressue
Types of pumps (2)
Positive displacement pumps; those that can displace liquids and gases.
Non-Positive displacement pumps; those that can displace liquids only (a primer is required to pump air from the system)
Centrifugal pump
What are the benefits
Simple maintenance
Can be run against closed deliveries without damage
Light and compact relative to their output
Can be driven directly from an internal combustion engine.
Centrifugal characteristics (3)
At any given speed where there is no flow, pressure is at a maximum
Pressure decreases as the deliveries are opened and flow increases
When the pump speed increases, pressure and flow increase.
What is impeller?
Water goes into the eye
Spins in the impeller
Centrifugal pushes it to the volute
Exits the shaft
What is a peripheral pump
Delivers high pressure
Ring of guide vanes
Prevents wear and tear to the centrifugal pump
What do Pump gagues do?
Fitted to allow the pump operator to control the intake and supply of water to branches and the supply of water is passing through to the pump efficiently
Low pressure gauge
§Indicates the pressure in ‘bars’ of the water in the pump and entering hose lines
It does not record the pressure at the branch unless the branch is closed down.
What is a high pressure pump
Black hose
§Indicates the pressure in ‘bars’ of the water in the pump & entering the high pressure hose reels
It does not record the pressure at the branch unless it is closed down.
What is a compound gauge
Records a negative pressure when working from an open source and a positive pressure when working from a pressure fed supply.
What are the failures of water from a pressure fed supply
Failure of the mains supply, such as a fractured main or burst delivery length of hose
Choked internal strainer in pump
Over-running the supply causing the soft suction to flatten.
Increased delivery pressure
Hand controlled branches being shut down
Sharp kinks in delivery hose
Vehicles parked or collapsed debris on delivery hose
Surge in mains pressure
Blockage of nozzle by stones when internal strainer omitted.
Decreased delivery pressure
Hand control branch being opened
Burst hose pipe
Drop on mains
What is cavitation
Bubbles form because of pockets of low pressure occurring around the centre of the impeller and this causes the water to vaporise
Trying to supply more water than is coming in to the pump – the remedy is to ease off the throttle
This is exaggerated when the water is hot.
