Pumps And Primers

Question 1

What is the definition of a pump?

Answer 1

A pump is a machine driven by some external power, used for transmitting energy to fluids

Question 2

All pumps fall into three categories, what are they?

Answer 2

Positive displacement
Ejector or jet
Centrifugal

Question 3

Centrifugal pumps are comprised of two main parts. What are they?

Answer 3

Impeller

Casing

Question 4

3 gauges - high pressure, low pressure & compound are found on the rear of the appliance. What are they for?

Answer 4

High pressure gauge - displays output of hose reel jets
Low pressure gauge - displays output of main jets
Compound gauge - displays positive pressure of incoming supply, and negative pressure of over drawing the supply.

Question 5

What are the characteristics of centrifugal pumps?

Answer 5

• At any given speed where there is no flow, (no delivery open) the pressure is at a maximum
• pressure decreases with an increase in discharge (opening of a delivery)
• pressure and flow increase as the pump speed is increased and vice versa
• when suction lift is increased pressure and flow decrease

Question 6

When working from a pressure fed supply (hydrant) what could cause the supply to fail?

Answer 6

Failure of the supply itself (fractured main or a burst hose between the hydrant and the pump)
Over running the supply

Question 7

What could be the cause of increased delivery pressure whilst at work? (This should be investigated at once as it implies a stoppage of some sort on the delivery side)

Answer 7

Kinks in the delivery hose
Vehicles standing on or debris fallen onto delivery hose
Blockage of jets by small stones which have passed through the pump
(Closing of the branch will also cause increased delivery pressure and gauges should be closely monitored to ensure other branches do not receive increased pressure)

Question 8

What could cause a decrease in delivery pressure whilst at work?

Answer 8

Delivery hose burst

Branches being opening up

Question 9

Pumps can be filled with water (known as priming) by three methods, what are they?

Answer 9

Elevated supply (water forced in by gravity, air pushes out)
Pressure supply (water forced in by hydrant, air forces out. Known as soft suction) 
Use of a primer (only used when working for open water. Air pumped out. Atmospheric pressure forces water up into the pump.

Question 10

What are the 3 types of primer?

Answer 10

Reciprocating (not used in modern appliances)
Exhaust gas ejector (used to prime portable pumps)
Rotary water ring (used on modern appliances to prime the centrifugal pump)

Question 11

When working from open water, the pump fails to prime and you have a no vacuum reading. What could’ve caused this?

Answer 11

Strainer not adequately submerged 
Loose or faulty suction joints 
A delivery valve not properly seated or closed
Air leaks in the suction hose 
Defective primer 
Air leak in the pipes to gauges 
Clapper valve on an exhaust ejector primer not seating 
Lack of water in the water ring primer.

Question 12

When working from open water, the pump fails to prime and you have a high vacuum reading. What could’ve caused this?

Answer 12

Blockage of the basket or metal strainer

Faulty suction hose (the inner walls have separated and collapsed)

Question 13

When working from open water, and whilst at work, you get decreased vacuum reading. What could this mean?

Answer 13

Level of static supply has risen

Less water being used by the branch (branch has been closed)

Question 14

Working from open water and whilst at work, you get an increased vacuum reading. What could this mean?

Answer 14

Drop in the level of the static supply
More water being delivered (branch opened)
Blocked suction strainer

Question 15

What is C in creft and what does it mean?

Answer 15

Creating the flow - a proportion of the atmospheric pressure is taken up in creating the flow

Question 16

What is R creft and what does it mean?

Answer 16

Raising the water - from its existing level to the pump outlet

Question 17

What is E in creft and what does it mean?

Answer 17

Entry loss - overcoming resistance due to the changes in direction as the water enters the pump impeller

Question 18

What is F in creft, and what does it mean?

Answer 18

Frictional Resistance - to the water on both entering and passing through strainers and hose

Question 19

What is T in creft and what does it mean?

Answer 19

Temperature of the water - the warmer the water the less lift can be attained as it tends to vaporise in the hose causing the pump to become unprimed.

Question 20

When working from open water what is the term used to describe the distance the water must travel from its source to the the inlet of the pump?

Answer 20

Lift

Question 21

What are the theoretical and expected lift distances?

Answer 21

Theoretical - 10m

Expected - 8m

Question 22

What are the duties of a pump operator?

Answer 22

Control of the discharge pressure carefully and make any changes gradually
Ensure water supply is maintained constantly
If it is necessary to cut off the water supply due to various reasons, every effort must be made to warn branch operators before this happens
Watch gauges constantly whilst pump operating. They will they will tell you what is happening with regards to supply of and delivery
Ensure the tank supply is full at all times so it is ready for use if necessary
Ensure that, as pump operator, you know exactly where all your deliveries are working

Question 23

What pressure should hose & main jets be?

Answer 23

Hose reel - 25 bar (high)
Main jet - 3/8 (low)
3 bar pressure if branch operator hasn’t given the bar
Changes 1 bar at a time

Question 24

What are the advantage of ejector pumps

Answer 24

No moving parts parts
They will in oxygen deficient atmospheres
Little attention is required while operating

Question 25

Who is responsible for calculating pressure required at the pump?

Answer 25

Branch operator

Question 26

Where is the HPVU based?

Answer 26

Sheldon

Question 27

Advantages of a centrifugal pump

Answer 27

Simple maintenance
They are small, light and compact relative to output
Can be run against closed deliveries without damage or danger
Can be driven directly from an internal combustion engine