THE PUMP! Flashcards
What is a pump?
A pump is a machine drive by external power to give energy to fluid!
The external power is the road engine!
The Fluid is the water!
CENTRIFUGAL PUMP
In the case of a pumping appliance’s centrifugal pump, the external power is the road engine and the fluid is the water. Centrifugal pumps cannot pump a gas and therefore cannot pump air.
POSITIVE DISPLACEMENT PUMP
A positive displacement pump works by moving a piston through a cylinder to put pressure into the fluid, a bicycle pump is an example. This type of pump can pump a gas.
What do centrifugal pumps rely on?
Centrifugal pumps rely on centrifugal force.
Centrifugal force is an outward force associated with rotation.
When an object is rotating i.e. a bicycle wheel it will throw anything m, not rigidly attach to its outside edge.
A single stage centrifugal pump has two parts:
What are they called?
1- The Impeller
2- The Volute
What is a impeller?
The impeller imparts kinetic energy (the energy of movement), to the fluid.
The impeller is the rotating component of a centrifugal pump.
The fluid enters at the impellers centre it transfers the energy from the motor that drives the pump to the fluid by accelerating the fluid outwards from the centre of rotation. The centre inlet is called the eye of the pump.
What is the Volute?
The Volute converts the kinetic energy to pressure energy.
The kinetic energy movement achieved by the impeller converts into pressure when the outward movement of the fluid is confined by the pump casing.
The pump casing is called the Volute.
How does the impeller and the Volute work together?
The speed at which the impeller rotates dictates the water pressure at the outlet. The faster it rotates the greater the speed at which the water moves towards the edge of the impeller and into the volute.
In the Volute the kinetic energy will be converted into the increased pressure obtained at the outlet.
What is PTO? (Power take off)
In a fire appliance pump the impeller is rigidly fixed to a driveshaft which is driven by the appliance road engine.
Power is diverted from the road wheels to this separate drive shaft by engaging the power takeoff. (PTO)
What is Multi Pressure pump?
Two stage pump
A major pumping appliance is able to produce water from delivery outlets and from hose reels at a much higher pressures.
For the hose reels to work effectively they require very high pressures. The pressure produced by the pump is limited by the speed of the road engine and the size of impeller that will fit on the appliance.
How do we overcome the limitation of a two stage pump, known as multi-pressure pump?
In a multi pressure pump a special type of impeller called a peripheral impeller is fixed to the same drive shaft as the low pressure impeller.
What can the peripheral impeller create?
The peripheral impeller can create pressures approximately five times greater than a low pressure impeller but because of its design the volume of water it can produce is reduced
What is the major pump used in LFB Mercedes appliances?
Godiva 3010 Prima Series multi-pressure.
It is a centrifugal two-stage pump and can therefore be used to:
- Supply high volumes of water at low pressure
- Low volumes of water at high-pressure
- Both high and low pressure simultaneously.
