Pumping Flashcards
What is a pump?
A pump is a machine driven by some external power, for transmitting energy to fluids.
What type of pump does ACTFR use and how does it work?
Centrifugal Pumps: use centrifugal force which is the tendency of a body to move outwards from a rotating centre.
What are the two main parts of a centrifugal pump?
The Impeller and the casing.
What does the impeller do?
When it rotates, water is discharged from the periphery by way of centrifugal force. This also creates a vacuum at the centre and water is sucked into the inlet which in turn feeds the impeller.
Name three parts of an impeller
1 - Water inlet
2 - Vanes
3 - Periphery
From what energy does the impeller convert into another form of energy?
The impeller converts kinetic energy to pressure energy.
What happens if the pump operates without discharge, what can happen?
Heat energy can build up which can then damage the pump.
What are the five components of a casing?
1 - water inlet
2 - impeller
3 - guide vanes
4 - volute
5 - delivery outlet
What do the guide vanes do?
Help guide water along the correct path in the casing. Also help reduce turbulence. Allow for kinetic energy to convert to pressure energy.
What does the casing do?
Designed to reduce turbulence and friction by creating a smooth a flow as possible.
How is the kinetic energy converted to pressure energy?
When the water enters the casing via the impeller, the velocity is reduced converting into pressure energy.
What ratio does the high pressure pump work at?
2:1 ratio
What does the high pressure pump do and what kPA should it be operated at?
Supplies water to the high pressure hose reel only and requires atleast 2000kPa for atomisation of water. The high pressure pump spins at a higher rpm than main pump and also heats up quicker.
What sort of shaft seal does ACTFR employ and what does it do?
All pumps employ a mechanical seal, stop water leaking into gear casings.
What can damage a mechanical seal?
Heat Energy
What factors determine pump capacity?
Intake diameter, impeller eye diameter, outside diameter of impeller, width of impeller, shape and number of vanes on impeller, design of volute chamber.
What are the rated capacity of Darley pumps in ACTFR?
Old Darley LDMH 1000: 3,800 L/min @1000kpa
New LDMH 1500: 5700 L/min @1000kpa
How can you reduce or eliminate air in the pump?
Use the primer or open a valve.
What is the relationship between pressure and head?
Head effects pressure by changes in height.
P = H x 10
What is cavitation?
Water boils are lower temps in a vacuum. If pressure on suction side of pump falls below vapour pressure of water, bubbles form. These bubbles are carried into the inlet, implode and can cause damage by breaking away small parts of metal.
What are some causes of cavitation?
The lift is too high for the volume of water and pressure being discharged.
The suction hose diameter is too small for the volume of water being discharged.
Restriction of suction line
Temperature of water being pumped is too high.
Hydrant supply being overrun.
What are some indications of cavitation?
Sounds like small stones passing through pump.
Engine revolution’s will increase.
Compound gauge will show negative pressure and collector hose will go soft.
Decrease in delivery of flow.
When draughting, gauge will drop below -75kPa
How does and what can happen when there is air in the pump?
Through leaky suction joint, or run out of foam concentrate. Air bubble will compress then expand with explosive force when it leaves the nozzle. Does not damage pump cause it does not implode.
How do you find Litres per minute?
kPA divide 10, then take away 50
E.g 2000kpa divide by 10 = 200,
200 minus 50 = 150L/per minute
