Ch 12.5 + 12.6: pump types and curves Flashcards
what are the 4 main classes of pumps?
Centrifugal, rotary, reciprocating, airlift
what are the four main components of a centrifugal pumps?
- housing
- impeller
- shaft
- bearings
what does the housing incorporate?
-it incorporates the casing that encloses the rotating member (impeller) and directs water to the outlet.
what is the impeller?
consists of 2 plates and VANES attached to them, which direct the water in the pump chamver to the outlet.
what are the three types of impellers?
- 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.
what is the shaft?
a rod that connects the pumps motor to the impeller and keeps the impeller properly positioned.
where is mechanical energy converted to kinetic energy?
in the shaft
what is used to seal the shafts from fluid entering the motor chamber?
- sealed bearings
- non-sealed bearings
what is a mag drive pump?
where a magnetic is located on the impeller and another on the motor so as the motor rotates, the impeller rotates accordingly.
why would you use a mag drive pump? name an instance
for aggressive fluids
-aquarium
what does a rotary pump consist of?
- housing
- rotary member
what is the function of a rotary member?
forces fluid from the low pressure end of the housing (inlet) to the high-pressure end of the housing (outlet).
when would you use a rotary pump?
for low pressure pumping, as the pump experiences ‘slipping’ in high pressure situations
what is a reciprocating pump?
it pumps water as the member moves back and forth
what part does a reciprocating pump require?
check valves: prevents the water from moving backward along the line.
what type of flow does a reciprocating flow yield?
pulsating flow
what moving parts are associated with air pump?
none
how does an air pump work?
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.
what parameter governs the efficiency of an airlift system?
-bubble size.
the finer the bubble, the more consistent the mixture (highest efficiency)
how is the size of a bubble dictated, for airlift systems?
is dictated by the size of the orifice opening
name some pros and cons to airlift system
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
how high can airlift pumps lift water? also, explain.
10% of the submerged depth. the greater the depth, the higher the lift
what is required to inject air into a submerged line (air injection system)?
- a blower
- a compressor
what is the difference between a blower and a compressor?
- 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.
a pump curve compares what?
the head to the discharge for a specific pump.
when selecting a pump, consider the 7 following criteria:
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
