pumps and motors Flashcards
Distribution 1
stores energy and consists of a pair of metallic plates that are separated by an insulating material called a dielectric
Capacitor
condition that occurs when pumps are run too fast or water is forced to change directions quickly-can cause pitting of the impeller and reduce pump efficiency
Cavitation
theoretical angular velocity that excites the natural frequency of a rotating object, such as a shaft
Critical speed
used to measure the average power of a load over a specific time interval as well as recording the peak power consumption during the period
demand meter
used on large equipment to check whether all the current entering a system comes out of the system-will shut down a system that is losing current as a safety precaution
differential relay
used when power is generated locally to respond to changes in the frequency of an AC power supply-also used on synchronous motor starters to sense when the motor has reached synchronizing speed
frequency relay
amount of energy in feet required to overcome resistance to flow in a pipe
friction head
energy possessed by water in a hydraulic system measured in feet
head
the study of fluids in motion
hydraulics
rotating set of vanes that forces water through a pump
-heart of the pump
impeller
prevent air leakage along the pump shaft when it is operating under suction lift conditions-also called a seal cage
lantern ring
seal placed on pump shaft to prevent water from leaking out along the shaft-also prevents air from entering the pump
mechanical seal
rings of graphite impregnated cotton, flax, or synthetic materials used to control pump shaft or valve stem leakage
packing
a follower ring that compresses the packing placed in the stuffing box
packing gland
two or more pumps whose discharges are entering a common pipe to increase volumetric flow rate
parallel operation
measure of the amount of energy in water due to water pressure
pressure head
amount of energy in feet that a pump supplies to a fluid
pump head
a condition where a pump is subject to frequent on/off cycling due to pressure surges that effect the pump controller
racking
a load acting at a right angle to the shaft
radial load
a piece of electrical equipment that changes alternating current to direct current by allowing the electric current to flow in one direction but blocking flow in the opposite direction
rectifier
one pump discharging into the suction line of another pump to increase the overall discharge head
series operation
recirculation within a centrifugal pump casing around the impeller due to a blockage of the pump discharge
slip
houses the packing and lantern ring in a centrifugal pump
stuffing box
a load that acts parallel to the axis of rotation
thrust load
an overcurrent protection device placed on each phase of a power supply to open up a control circuit and stop a motor, if the current becomes excessive
thermal overload relay
electrical device used to detect power loss and initiate an automatic switchover to another power supply
voltage relay
rings made of brass or bronze placed on the impeller and/or casing of a centrifugal pump to separate the suction side of the pump from the discharge side
wear ring
uses an impeller or propeller to accelerate water to a high velocity within the pump casing-high velocity (low pressure) converted to high pressure (low velocity) as casing volume increases
velocity pumps
most commonly used pumps in water systems-water thrown outward from the center of the impeller and into the volute or diffusers
-velocity is converted to pressure
radial flow pump
referred to as a propeller pump-no volute or diffuser vanes
- propeller shaped impeller increases head by lifting action of the blades
- water moves parallel to the pump shaft
- pump can move large volumes of water but adds little head
- shaft rotates between 9000 and 15000 rpm
axial flow pump
- combination of radial flow and axial flow pumps
- impeller is shaped so centrifugal force will impart some radial force
- used where water contains a high solids concentration
mixed flow pump
most commonly used volute-type pump
- can achieve various flows and pressures
- can develop as much as 250ft of head per stage
- efficiency between 75%-85%
- inexpensive and little maintenance
centrifugal pump
- impeller rotates within a channel of constant cross-sectional area
- flow velocity is converted to pressure by a diffuser guide vanes
- most efficient of all velocity pumps and generates the highest head
- efficiency between 90%-95%
- expensive and difficult to maintain
vertical turbine pump
vertical turbine pump with very long pipe column housings and drive shafts
- drive unit remains above ground
- piping, shaft sections, and multiple stages are lowered into the ground
deep-well pump
multistage mixed flow centrifugal pumps or turbine pumps with a close-connected motor
-designed to operate completely under water
submersible pump
referred to as a “can pump”
-motor and pump usually close-coupled and pump draws suction on water collection sump
booster pump
used for metering treatment chemicals into the system
-deliver a fixed volume of liquid for every stroke or revolution regardless of discharge pressure
positive-displacement pump
piston moves in and out of a cylinder and liquid is discharged through check valves
-creates a pulse in discharge minimized by use of multiple cylinders or pulsation dampeners
reciprocating pump
use closely meshed vanes, gears or lobes rotating within a tight chamber to move liquid
rotary pump
uses a flexible diaphragm to vary the size of a chamber
-check valves allow flow in and out with each stroke of the drive unit
diaphragm pump
what are the three types of single phase motors?
1) split phase motor
2) repulsion-induction motor
3) capacitor-start motor
draws high current when starting and has low starting torque
split phase motor
draws a lot of current on start up
repulsion-induction motor
high starting torque and starting current
-good when needed to be brought up to speed quickly and not cycled on and off
capacitor-start motor
What are the classifications for three phase motors?
1) squirrel cage induction motor
2) synchronous motor
3) wound rotor induction motor
simplest type of all AC motors
- current flowing through stator winding establishes a magnetic field which induces a voltage in the rotor windings-causes motor to turn
- can be used for high starting torque without special starting circuitry applications
squirrel cage induction motor
used in applications requiring constant motor speed
-rotating magnetic field rotates as a synchronous speed
synchronous motor
easy to start, variable speed options and low starting current
- motor is similar to squirrel cage induction motor
- uses variable frequency drives to control speed
wound rotor induction motor
