Fans

Question 1

List three (3) kinds of pressure found in operating fan ducts?

Answer 1

• Static
• Velocity
• Total Pressures

Question 2

What is a manometer used for?

Answer 2

Is a U shape tube connected to the fan for measuring pressures.

Question 3

How can you remove static electricity generated from a fan?

Answer 3

Ground the rotating element with a ground brush and cable assembly.

Question 4

Name two (2) major type of fans according to flow through the impeller?

Answer 4

• Radial Flow Centrifugal

* Axial Flow Propeller

Question 5

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

Answer 5

The Scroll.

Question 6

Name two (2) ways of placing bearings on a shaft in relationship to the fan wheel?

Answer 6

• The wheels can be mounted between bearings

* The wheels can be mounted overhung on the shaft

Question 7

How can control of air through fans be accomplished?

Answer 7

• Inlet Louvre
• Outlet Dampers
• Varying The Fan Speed

Question 8

Why are some fans mounted on a base with the aid of springs?

Answer 8

Fan base springs are used to dampen out fan vibrations to the base.

Question 9

What is the type of inspection 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 monitor?

Answer 10

A vibration analyzer.

Question 11

Fan overhaul is best accomplished by following what directions/instructions?

Answer 11

Original Equipment Manufacturer’s Overhaul Prints And Procedures.

Question 12

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

Answer 12

All part need to be inspected for off-specification sizes and fatigue (cracks).

Question 13

Why would the fan wheel hub be heated before installing it on a shaft?

Answer 13

The bore size is increased with heat, allowing easy installation onto a cold shaft?

Question 14

Explain the purpose of balancing a fan rotor in a dynamic balancer?

Answer 14

Dynamic balancing is performed to reduce the vibration of the fan to acceptable levels.

Question 15

What is the purpose of a cold rollover of the fan rotors?

Answer 15

A cold rollover is used to confirm that there are no rubbing metal parts and no cracking noises experienced after a fan overhaul.

Question 16

What is static pressure?

Answer 16

Is the pressure the air exerts on the inside of the duct walls or piping and what overcomes the resistance ducts, fuel beds, filters and grates.

Question 17

The pressure exerted on the vane is pressure due to air velocity is called?

Answer 17

Velocity Pressure.

Question 18

How is velocity pressure produced?

Answer 18

is produced by the impact of air flowing through a duct and is felt only by the surfaces that the air actually strikes.

Question 19

Velocity pressure is the pressure over and above what pressure?

Answer 19

Static Pressure.

Question 20

What is total pressure?

Answer 20

Is adding velocity pressure to static pressure.

Question 21

How is static electricity caused?

Answer 21

By stripping electrons off ductwork surfaces making the static charges built up to very high levels before they get to discharge and arcing the bearing.

Question 22

As air flow decreases, so does the system pressure (backpressure) and the fan respond by creating more flow, this action is known as?

Answer 22

Hunting or Surge

Question 23

Large single suction fans are generally mounted on?

Answer 23

Double Row Spherical Roller Bearing.

Question 24

What are the three variations of mechanical draft?

Answer 24

• Induced Draft
• Forced Draft
• Balanced Draft