Lifting From Open Water

Question 1

What is a primer?

Answer 1

The function of a primer is to remove air from the pump and create a partial vacuum

There are three ways to prime a centrifugal pump:

•Use a gravity fed supply (on-board tank)

•Use a pressure fed supply (hydrant or another pumping appliance)

By using a priming device to remove the air from the pump.

Question 2

3 types of primer?

Answer 2

The air in the hard suction and pump casing must be expelled so that atmospheric pressure will force water into the pump
Water ring primer
Reciprocating primer
Exhaust gas ejector

Question 3

3 characteristics of lifting from open water

Answer 3

•The height to which water can be lifted is referred to as head

•The maximum practical lift is generally considered to be 8 meters. This is the distance measured from the eye of the pump to the surface of the water source.

•The maximum theoretical lift is 10 metres which equates to 1 bar of atmospheric pressure.

Question 4

What is CRESTA

Answer 4

Creating the flow
Resistance to the suction pipe
Entry loss as the water enters pipe
Strainer
Temperature
Atmospheric pressure

Question 5

What does the compound gauge do?

Answer 5

Records negative pressure when drawing water
Positive pressure when working from a pressure fed supply (hydrant)

Question 6

What happens if the pumps fails to achieve a prime

Answer 6

If the pump fails to prime, the compound gauge will show either no vacuum reading or very high vacuum reading

Question 7

No vacuum reading means

Answer 7

•The strainer may not be adequately submerged

•Loose or faulty suction hose joints

•An open drain cock, or loose drain plug in the pump casing

•Delivery valves not seating properly.

•Air leaks in the suction hose

•Defective seal

A serious leak in one of the pipes leading to

Question 8

Very high vacuum reading

Answer 8

•A blockage around the strainer

•Faulty suction hose (the hose may have collapsed, or the internal lining may have come apart)

Strainer sinking into mud or debris.

Question 9

Complete loss of vacuum reading

Answer 9

•Strainer rising too near to the surface

•Water level has dropped too low

In either case, plenty of warning would be given to the pump operator by fluctuation in gauge readings and possibly engine speed.

Question 10

Decreased vacuum reading

Answer 10

•Branches being closed

•The water supply level rising (tidal etc.)

Slight leak on the suction side of the pump.

Question 11

Increased vacuum reading

Answer 11

•Branches being opened

•The water supply level has dropped (tidal etc.)

•Strainer partially or completely blocked

Burst length of delivery hose