Fans Flashcards
(25 cards)
what are three kinds of pressure found in operating fan ducts?
static pressure
velocity pressure
total pressure
what is a manometer used for?
measuring pressures
how can you remove static electricity generated by fans?
ground the rotating element with a ground brush and cables
what are the two major types of fans according to flow through the impeller
radial flow - centrifugal
axial flow - impeller
what is the name of the circular collection chamber mounted around the fan wheel of a centrifugal fan?
scroll
what are two ways of placing bearings on a shaft in relationship to a fan wheel?
- wheel can be mounted between bearings
- wheel can be mounted overhung on the shaft
how can control of air through fans be accomplished
inlet louvres
outlet dampeners
varying shaft speed
why are some fans mounted in a base with the aid of springs?
springs absorb vibration
what is the plan called that allows periodic checking of fans on a routine basis?
preventative maintenance
troubleshooting of fans is best accomplished by using which type of monitors?
vibration analyzers
fan overhaul is best accomplished by following what directions?
manufacturers
why should all parts be inspected and measured during an overhaul?
check for wear and fatigue
why would the fan wheel hub be heated before installation on the shaft?
bore size will increase
explain the purpose of balancing a fan rotor in a dynamic balancer
reduce the vibration to acceptable levels
what is the purpose of a cold rollover of the fan rotor?
to make sure none of the parts are rubbing
what does the term draft refer to?
the pressure change required to produce the flow of gas “air”
what type of fan would be subjected to highly contaminated gas flow?
induced draft fan
what two blade styles would be found on an induced draft fan? why?
straight and forward, they are self-cleaning
what style of blade would be found on a forced draft fan? why?
backward, they create higher speeds, which create higher pressures to overcome the resistance to flow
what fans are used in “balanced” draft system?
forced and induced
what is the advantage of using a “balanced” draft system?
increase efficiency and control of pressures
what are the three methods of controlling radial fan output?
vary the speed of the driver
regulate the input (vanes, dampeners)
recirculation
what style of fan is commonly used on cooling towers and fin fans?
axial flow (propellers)
what are three methods for adjusting the flow rate through an axial fan?
change the speed of the driver
change the pitch of the blades
place louvers on the input
