Pump Theory

Question 1

What are the two basic types of positive displacement pumps?

Answer 1

Piston and rotary

Question 2

When air in the pump has been replaced by water the pump is said to be ___?

Answer 2

Primed

Question 3

All pumps in use today by the fire service fall into one of these two categories. What are they?

Answer 3

Positive displacement or centrifugal.

Question 4

How does a centrifugal pump produce a discharge of water under pressure?

Answer 4

By using the velocity of water created by centrifugal force to create pressure.

Question 5

What is the advantage of a rotary-van pump over a rotary gear pump?

Answer 5

It is less susceptible to wear.

Question 6

What pump has no mechanical obstruction between its intake side and discharge side?

Answer 6

Centrifugal

Question 7

What kind of pump is not self priming?

Answer 7

Centrifugal

Question 8

What are rotary type primers usually driven by?

Answer 8

Electrical motors

Question 9

What pump is a non-positive displacement pump?

Answer 9

Centrifugal

Question 10

The velocity created by the impeller of a centrifugal pump is converted to pressure how?

Answer 10

Confining water within the casing.

Question 11

In a centrifugal pump, water is introduced from the intake into what specific part of the pump anatomy?

Answer 11

The eye of the impeller

Question 12

The portion of the casing which forms a water passageway which gradually increases in size as it nears the pump discharge is called the ___?

Answer 12

Volute

Question 13

What are the three main factors that influence a centrifugal fire pump’s discharge pressure?

Answer 13

1) Volume of water being discharged
2) Pressure of water coming into the pump
3) Speed of the impeller

Question 14

What is the relationship between volume and pressure in a centrifugal pump?

Answer 14

They are inversely related. So the greater the pressure, the lower the volume, and the greater the volume, the lower the pressure.

Question 15

With all other factors being constant, doubling the speed of the impeller of a centrifugal pump will result in approximately __ times more pressure?

Answer 15

4 times more pressure

Question 16

Because there is no mechanical obstruction between the intake and the discharge sides of the centrifugal pump ___?

Answer 16

Intake pressure will directly effect discharge pressure.

Question 17

Why is an external priming pump needed in order fora centrifugal pump to draft?

Answer 17

Because centrifugal pumps can’t pump air, so an additional pump is needed to remove air from the system.

Question 18

What is the purpose of the double suction impeller?

Answer 18

Reduce wear on the pump by reducing lateral thrust.

Question 19

Define net discharge pressure.

Answer 19

Incoming pressure plus pressure created by the pump.

Question 20

In order to deliver maximum pressure, the imllers of a multistage pump should be run in _____?

Answer 20

Series/pressure

Question 21

In order to deliver maximum volume, the impellers of a multistage pump should be run in ___?

Answer 21

Parallel/volume

Question 22

The device which directs the flow of water between he impellers of a multistage pump is the ___?

Answer 22

Transfer valve

Question 23

What is the first sign of significant wear in a centrifugal pump?

Answer 23

Increased engine RPMS required for the pump to meet its rated capacity during testing.

Question 24

When operating “pump and roll” with a PTO driven pump, the driver/operator should ___?

Answer 24

Drive by the cab-mounted pressure gauge rather than the speedometer.

Question 25

Pump and roll operations are not possible with ___?

Answer 25

Most transfer pump driven systems.

Question 26

The NFPA requires that a pumper with a rated capacity greater than 500 GPM the piping supply in the pump from the tank should be adequate to supply pump discharge flow of at least ___ gpm.

Answer 26

500

Question 27

A leaky tank to pump valve may result in ___?

Answer 27

Inability to draft

Question 28

Why is centrifugal pump intake piping locate below the level of the eye of the impeller?

Answer 28

To prevent air from accumulating in the intake pipes.

Question 29

Why is it better to receive water through the side intakes instead of the front and rear intakes?

Answer 29

The maximum flow capacity is significantly less in the front and rear intakes.

Question 30

In addition to replenishing tank water, the tank fill line can be used to ___?

Answer 30

Circulate water to keep the pump cool when discharges are closed.

Question 31

The NFPA requires slow-acting valve controls on intake or discharge valves equal to or greater than ___ inches in diameter.

Answer 31

3 inches

Question 32

The NFPA requires that a pressure control device be activated when ___ PSI above the working pressure.

Answer 32

30 PSI

Question 33

What is the name of the device that is designed to protect the pump from excessive or surging pressure from an external water supply?

Answer 33

Intake pressure relief valve

Question 34

A governor regulates pump discharge pressure by ___?

Answer 34

Adjusting engine throttle

Question 35

Which type of pressure governor provides the fastest, most accurate regulation of discharge pressure?

Answer 35

Electronic

Question 36

In general, the correct engine speed for priming is about ___ rpm?

Answer 36

1000-1200

Question 37

What part of the pump determines the volume capacity of the pump?

Answer 37

The size of the impeller, because a larger impeller has a larger eye which allows for greater water flow capacity.

Question 38

To minimize corrosion of the priming pump, you should ___?

Answer 38

Operate it regularly

Question 39

On a gauge, vacuum is indicated in ___?

Answer 39

mm/hg or millimeters of mercury.

Question 40

Which type of gauge can indicate a vacuum?

Answer 40

A compound gauge

Question 41

On a gauge, pressure is indicated in what measurement?

Answer 41

PSI

Question 42

If the oil pressure gauge reads low, the first thing to check is ___?

Answer 42

Crankcase oil level

Question 43

What is the purpose of an auxiliary cooler?

Answer 43

Control engine coolant temperature

Question 44

A pump discharge pressure of ____ is required to overcome pressure in the radiator.

Answer 44

50