Ch 12.5 + 12.6: pump types and curves

Question 1

what are the 4 main classes of pumps?

Answer 1

Centrifugal, rotary, reciprocating, airlift

Question 2

what are the four main components of a centrifugal pumps?

Answer 2

• housing
• impeller
• shaft
• bearings

Question 3

what does the housing incorporate?

Answer 3

-it incorporates the casing that encloses the rotating member (impeller) and directs water to the outlet.

Question 4

what is the impeller?

Answer 4

consists of 2 plates and VANES attached to them, which direct the water in the pump chamver to the outlet.

Question 5

what are the three types of impellers?

Answer 5

• open type: where the vanes are attached to one rotating plate
• semi-enclosed type: the vanes are attached to a circular disk
• enclosed type: the vanes are located between two circular disks.

Question 6

what is the shaft?

Answer 6

a rod that connects the pumps motor to the impeller and keeps the impeller properly positioned.

Question 7

where is mechanical energy converted to kinetic energy?

Answer 7

in the shaft

Question 8

what is used to seal the shafts from fluid entering the motor chamber?

Answer 8

• sealed bearings

- non-sealed bearings

Question 9

what is a mag drive pump?

Answer 9

where a magnetic is located on the impeller and another on the motor so as the motor rotates, the impeller rotates accordingly.

Question 10

why would you use a mag drive pump? name an instance

Answer 10

for aggressive fluids

-aquarium

Question 11

what does a rotary pump consist of?

Answer 11

• housing

- rotary member

Question 12

what is the function of a rotary member?

Answer 12

forces fluid from the low pressure end of the housing (inlet) to the high-pressure end of the housing (outlet).

Question 13

when would you use a rotary pump?

Answer 13

for low pressure pumping, as the pump experiences ‘slipping’ in high pressure situations

Question 14

what is a reciprocating pump?

Answer 14

it pumps water as the member moves back and forth

Question 15

what part does a reciprocating pump require?

Answer 15

check valves: prevents the water from moving backward along the line.

Question 16

what type of flow does a reciprocating flow yield?

Answer 16

pulsating flow

Question 17

what moving parts are associated with air pump?

Answer 17

none

Question 18

how does an air pump work?

Answer 18

by injecting air into a submerged line, resulting water has a lower density than the surrounding water. if air is continually injected the water will continue to rise drawing in more water from below.

Question 19

what parameter governs the efficiency of an airlift system?

Answer 19

-bubble size.

the finer the bubble, the more consistent the mixture (highest efficiency)

Question 20

how is the size of a bubble dictated, for airlift systems?

Answer 20

is dictated by the size of the orifice opening

Question 21

name some pros and cons to airlift system

Answer 21

P: can easily pump corrosive liquids or liquids with large amount of solids
-incoming water is aerated
C: limitation to how small the bubbles can be, limited by the orifice openings
-smaller bubble diameter requires a greater force to drive oxygen thru the stone.
-stones that create the bubbles require periodic cleaning

Question 22

how high can airlift pumps lift water? also, explain.

Answer 22

10% of the submerged depth. the greater the depth, the higher the lift

Question 23

what is required to inject air into a submerged line (air injection system)?

Answer 23

• a blower

- a compressor

Question 24

what is the difference between a blower and a compressor?

Answer 24

• blowers cannot move air if there is a pressure gradient between in inlet and outlet. So, low pressure air, but constant.
• compressors can inject air at a depth, but are limited by the amount of air stored in their reservoir.

Question 25

a pump curve compares what?

Answer 25

the head to the discharge for a specific pump.

Question 26

when selecting a pump, consider the 7 following criteria:

Answer 26

1: lowest initial cost
2: lowest energy requirement
3: running near its max efficiency
4: lowest maintenance
5: compatible with the liquid medium
6: input power requirements
7: generator size