what is a pump? 

• machine that transfers energy to fluids

result of a poor pump choice

• increase cost of running it and increase chance of pump failure

how are pump performance characteristics typically expressed?

• graphically

what are important characteristics to consider for pumps? 

• discharge, generated head, power requirements, efficiency

what is discharge in relation to pumps?

• pump capacity

what is generated head in relation to pumps?

• height that a pump can raise a fluid

what are power requirements in relation to pumps?

• brake power

what is efficiency in relation to pumps? 

• energy imparted to liquid / brake power

why do characteristics change as a pump ages? 

• parts wear down

what is a reciprocating pump? 

• uses a piston to move fluid

• pulls liquid into a chamber and pushes it out 

how does water move throughout a reciprocating pump?

• piston pulls back, creates low pressure area in chamber

  • opens valve, allowing water to flow into the chamber

• piston moves forward, pushing water out of the chamber

  • increases pressure, closes valve and opens up outlet valve, forcing water out of the pump

what is a “positive displacement pump”

• moves fluid by trapping fixed volume and then forcing it out 

• consistent flow

reciprocating pumps and suspended material

• handled reasonably well

how can the water discharge pulses be controlled in a reciprocating pump?

• can be reduced with multiple pistons

what are the three kinds of positive displacement pumps?

• reciprocating pump

• rotary pump

• diaphragm pump

how do rotary pumps operate?

• moving fluid from low-pressure side of the pump to the high-pressure side

what is a flexible vane pump?

• electronically placed rotor with flexible vanes that bend against the inside of the housing

what are vanes?

• blades that guide and move fluid through pumps

variation of flexible vane pump

• non-flexible vanes that maintain contact with walls as pump rotates

what is a peristaltic pump?

• has a flexible hose / tube inside a housing

• rotor turns, squeezes the tube, and forces fluid forward

what is a rotor inside a pump?

• rotating part that drives the movement of fluid through the pump

what happens as fluid moves forward in a peristaltic pump? 

• drop in pressure behind moving fluid, which draws in more fluid

what is a diaphragm pump?

• diaphragm moves up, pressure decreases, and fluid is drawn into the chamber

• when the chamber pressure increases from the diaphragm moving down, the fluid previously drawn in is forced out

what is another word for diaphragm pump? 

• membrane pump

what is the most common pump used in aquaculture? 

• centrifugal pumps

how do centrifugal pumps work? 

• when water enters the low pressure area, it is flung outward by an impeller

what is an impeller? 

• not the same thing as a propeller

• pulls water in, propeller pushes

what happens to the speed and potential energy in a centrifugal pump? 

• as water spins around housing, loses speed and gains potential energy

what head does a centrifugal pump generate? 

• static head 

• dynamic head

what does static and dynamic head address in a centrifugal pump? 

• static - gravitational potential energy needed to move fluid to a certain height

• dynamic - continuous energy input required to maintain fluid flow

what is a volute centrifugal pump? 

• impeller spirals out

why is the conversion from dynamic head to static head crucial in centrifugal pumps? 

• enables the pump to actually move fluid against resistance

how does the conversion from dynamic to static head occur in a volute centrifugal pump? 

• change in housing which slows the water

what are diffuser centrifugal pumps?

• attached to the housing that reduces turbulence and energy loss to fluid

three impeller designs

• open impeller 

• semi-open impeller

• closed impeller

what is an open impeller? 

• vanes on an incomplete disk, not too efficient, good if there are lots of suspended materials

what is a semi-open impeller? 

• vanes on a complete disk

what is the most common impeller type used in aquaculture? 

• semi-open impeller

what is a closed impeller? 

• vanes between two plates, very efficient but does not handle suspended material well

what is a propeller? 

• designed to convert rotational motion into forward thrust

what is cavitation? 

• formation of bubbles or steam by the propeller occurring at the blades

what are propeller pump seeds limited by at the blade tips? 

• cavitation

what makes water boil at low temperatures? 

• if the water pressure is very low

relationship between blade tip speed and propeller diameter

• speed at the blade tips increases with propeller diameter

what are mixed flow pumps? 

• use both centrifugal force and lifting action of a propeller 

what are mixed flow pumps primarily used for? 

• deep well turbines

what are fish pumps used for? 

• to pump large numbers of fish from a raceway / pond

what are fish pumps made of?

• soft and flexible hoses

what is an Archimedes screw? 

• moves water up an incline

how much head is generated in airlift pumps? 

• little head

what is aeration? 

• process of introducing air into a liquid 

• increases the oxygen content of the water 

what will happen if the top of tube of the airlift pump is too far above the water surface? 

• mixture won’t leave 

efficiency of airlift pumps is a function of: 

• volume of air injected

• depth of the tube

• height of the tube above the surface

• depth of the air injection

what size bubbles are more efficient in lifting water from airlift tubes? 

• small bubbles 

what circumstances should airlift pumps be in ponds? 

• should be on floats so top of pipe stays above surface water and depth of injection is kept constant

what do aquariums use? 

• small air compressors (diaphragm pumps)

what kind of pressure and volume do small air compressors deliver? 

• small volumes at high pressure

what do larger facilities use? 

• blowers

what kind of volume and pressure do blowers deliver? 

• high volumes at lower pressures

what is a regenerative pump? 

•  thought of as a centrifugal pump, but with performance as positive displacement pumps

what is the primary difference between centrifugal and a regenerative pump? 

• air only travels through centrifugal impeller once

• in a regenerative pump, it takes many passes

what method is used most often to measure water flow? 

• “bucket and stopwatch” method

what are head flowmeters based on and measured by? 

• based on a difference in pressure, usually measured by a manometer

what is another name for head flowmeter? 

• “differential pressure (DP) flowmeter”

what are two kinds of head flowmeters? 

• orifice and venturi flowmeter

how does an orifice flowmeter work? 

• plate constricts flow, offer a precisely measured obstruction that narrows the pipe and forces fluid to constrict

how does a venturi flowmeter work? 

• restriction is a gradually changing throat rather than a plate

difference in pressure lost in orifice flowmeter and venturi flowmeter

• venturi flowmeter has less pressure lost

what are venturi and orifice flowmeters connected to? 

• differential manometer

what else could a manometer be? 

• device that measures pressure

what is the most common use for a manometer? 

• most often refers specifically to a U-shaped tube filled with fluid

what is another name for a rotameter? 

•  variable area flow meter

what are two kinds of mechanical flowmeters? 

• rotameter and turbine flowmeter

what are the two main types of Ultrasonic flowmeters? 

• Doppler and transit time

what do ultrasonic transit time flow meters measure? 

• time difference of transit time of ultrasonic pulses flowing in and against direction of flow, the time difference is a measure for the average velocity of the fluid along the path of the ultrasonic beam 

what are Reynold’s numbers? 

• quantities used to predict similar flow patterns in different fluid flow situations

what is kinematic viscosity? 

• ratio of absolute viscosity to density

what is viscosity in general? 

• thickness of the fluid, therefore resistance to flow

• ex. honey has high viscosity, water has low viscosity