Fans

Question 1

what are three kinds of pressure found in operating fan ducts?

Answer 1

static pressure
velocity pressure
total pressure

Question 2

what is a manometer used for?

Answer 2

measuring pressures

Question 3

how can you remove static electricity generated by fans?

Answer 3

ground the rotating element with a ground brush and cables

Question 4

what are the two major types of fans according to flow through the impeller

Answer 4

radial flow - centrifugal
axial flow - impeller

Question 5

what is the name of the circular collection chamber mounted around the fan wheel of a centrifugal fan?

Answer 5

scroll

Question 6

what are two ways of placing bearings on a shaft in relationship to a fan wheel?

Answer 6

• wheel can be mounted between bearings
• wheel can be mounted overhung on the shaft

Question 7

how can control of air through fans be accomplished

Answer 7

inlet louvres
outlet dampeners
varying shaft speed

Question 8

why are some fans mounted in a base with the aid of springs?

Answer 8

springs absorb vibration

Question 9

what is the plan called that allows periodic checking of fans on a routine basis?

Answer 9

preventative maintenance

Question 10

troubleshooting of fans is best accomplished by using which type of monitors?

Answer 10

vibration analyzers

Question 11

fan overhaul is best accomplished by following what directions?

Answer 11

manufacturers

Question 12

why should all parts be inspected and measured during an overhaul?

Answer 12

check for wear and fatigue

Question 13

why would the fan wheel hub be heated before installation on the shaft?

Answer 13

bore size will increase

Question 14

explain the purpose of balancing a fan rotor in a dynamic balancer

Answer 14

reduce the vibration to acceptable levels

Question 15

what is the purpose of a cold rollover of the fan rotor?

Answer 15

to make sure none of the parts are rubbing

Question 16

what does the term draft refer to?

Answer 16

the pressure change required to produce the flow of gas “air”

Question 17

what type of fan would be subjected to highly contaminated gas flow?

Answer 17

induced draft fan

Question 18

what two blade styles would be found on an induced draft fan? why?

Answer 18

straight and forward, they are self-cleaning

Question 19

what style of blade would be found on a forced draft fan? why?

Answer 19

backward, they create higher speeds, which create higher pressures to overcome the resistance to flow

Question 20

what fans are used in “balanced” draft system?

Answer 20

forced and induced

Question 21

what is the advantage of using a “balanced” draft system?

Answer 21

increase efficiency and control of pressures

Question 22

what are the three methods of controlling radial fan output?

Answer 22

vary the speed of the driver
regulate the input (vanes, dampeners)
recirculation

Question 23

what style of fan is commonly used on cooling towers and fin fans?

Answer 23

axial flow (propellers)

Question 24

what are three methods for adjusting the flow rate through an axial fan?

Answer 24

change the speed of the driver
change the pitch of the blades
place louvers on the input

Question 25

what four methods of removing atmospheric contamination from a flow of air or gas?

Answer 25

bag filters
scrubbers
dry filters
cyclones
precipitators/ electrostatic charges