Pump Theory

Question 0

Positive displacement pumps are mechanical devices capable of?

Answer 0

Increasing the volume of the chamber. Water is drawn into the chamber as the volume is increased and in turn is forced out as the volume is decreased

Question 1

What is the theory of positive displacement based on?

Answer 1

That water is a non-compressible fluid and will, therefore, occupy a volume directly proportional to the weight

Question 2

Slip is?

Answer 2

Leakage between internal parts of the pump

Question 3

True or false
Air as well as water can be drawn into and expelled by a positive displacement pump. These pumps are, therefore, capable of producing sufficient vacuum prime themselves

Answer 3

True

Question 4

Piston pumps are used for?

Answer 4

Pumping small volumes of water at extremely high pressures

Question 5

Rotary type positive displacement pumps consist of

Answer 5

A casing divided into separate suction and discharge chambers by a rotor

Question 6

In a positive displacement pump, as speed increases

Answer 6

The amount of water pumped increases proportionately

Question 7

Rotary pumps take pressure advantage of

Answer 7

Hydrants

Question 8

Displacement factors:

Theoretical displacement is?

Answer 8

Every time the pump turns over once, it moves a certain amount of water from the suction side to the discharge side of the pump

Question 9

Displacement factors:

Actual displacement is

Answer 9

Pressure on the discharge side pushes some water back into the suction. Water slips back through pump clearances.

Question 10

Displacement factors:

Volumetric efficiency

Answer 10

= Actual displacement x 100

Theoretical displacement

Question 11

Rotary pumps are not good for high-pressure; most manufacturers do not recommend pressures higher than?

Answer 11

300 psi

Question 12

Rotary gear pumps

Answer 12

Two intermeshing gears or cams revolving in opposite directions within a close fitting casing.
Rotors move away from each other on the suction side and toward each other on the discharge side.

Question 13

Rotary vane pumps

Answer 13

Consists of a single rotor within, and eccentric to, a casing. A series of slots in the rotor permit sliding vanes to move in and out, maintaining contact the surface of the casing by means of centrifugal action in rotation of the rotor.

Question 14

Centrifugal means

Answer 14

To proceed away from the center, to develop outward; the energy to impel an object outward from a center rotation.

Question 15

Diffusion impellers

Answer 15

Diffusion: water directed toward the discharge outlet by means of a series of stationary diffusion vanes fastened to or part of the inner wall of the pump casing.

Question 16

Volute impeller

Answer 16

Spiral shaped casing

Question 17

Combination impeller

Answer 17

Spiral shaped casing with stationary diffusion vanes

Question 18

The volute principle

Answer 18

To enable the pump to handle the increasing quantity of water, at the same time permitting the velocity of the water to remain constant

Question 19

The impeller

Answer 19

creates a velocity in the water which is converted into pressure as it approaches the confining space of the discharge pipe.

Question 20

Displacement factors in centrifugal pumps

Answer 20

1. When pumping at constant pressure, the quantity of water is directly proportional to speed of the pump

New quantity = new pump speed
——————— X old quantity
Old pump speed

Question 21

Displacement factors in centrifugal pumps

Answer 21

2 when pumping at constant quantity, pressure is directly proportional to the square of the speed
2
New pressure = (new pump speed)
———————- X old pressure
(Old pump speed )

Question 22

Has the priming line discharge above the eye of the impeller

Answer 22

Waterous pump

Question 23

Has the priming line discharge at the eye of the impeller

Answer 23

Hale pump