fans

Question 1

What is the primary purpose of preventative maintenance?

Answer 1

To ensure the proper functioning and longevity of equipment through regular inspections and maintenance

Question 2

How often is preventative maintenance typically scheduled?

Answer 2

Once every six months

Question 3

What should be done to the fan before starting preventative maintenance?

Answer 3

The fan should be shut down, isolated (dampers closed), and locked out electrically

Question 4

What method is used to prevent backward rotation of the fan during maintenance?

Answer 4

The fan wheel is blocked with wooden blocks and wedges

Question 5

What items should be inspected when a fan is shut down for preventative maintenance? List at least three.

Answer 5

• Clean and inspect bearing elements for wear, cracks, pitting
• Check babbitt bearing oiling systems for operation
• Inspect fan wheel and scroll for visible cracks

Question 6

What action should be taken if excess clearance is evident in bearing clearances?

Answer 6

Reduce internal clearance

Question 7

What should be done with old grease during maintenance?

Answer 7

Clean out old grease and repack the bearings with the recommended grease

Question 8

What should be checked in the cooling water jackets?

Answer 8

Check for deposits and buildup; acidize if necessary

Question 9

What tool is used to check the shaft for cracks?

Answer 9

Ultrasonic equipment

Question 10

What should be inspected regarding the fan wheel?

Answer 10

• Check for missing balance weights
• Check for dirt buildup
• Check the fit between the hub and shaft

Question 11

What should be done to the bolts or set screws holding the fan hub to the shaft?

Answer 11

Check to make sure they are tight

Question 12

What should be checked on the inlet bell and guide vanes?

Answer 12

Check for cracks or looseness

Question 13

What is required if the inlet screen is found to have broken welds or damaged fasteners?

Answer 13

Remove and repair

Question 14

What should be inspected regarding outlet dampers?

Answer 14

Check for broken or cracked parts and remove and repair as necessary

Question 15

What should be checked for wear during maintenance?

Answer 15

Vibration isolators mounted between the fan and base

Question 16

Why is it important to check the fan base during maintenance?

Answer 16

To ensure it is level on the foundation and adjust if necessary

Question 17

What should be traced to ensure functionality?

Answer 17

All ground straps

Question 18

What should be done with mechanical fan control linkages during maintenance?

Answer 18

Remove, inspect, and repair or replace as necessary

Question 19

What components should be inspected in the drive mechanism?

Answer 19

• Coupling
• Motor
• Sheaves
• Belts
• Tension adjusters

Question 20

What is the last step to perform before removing locks and tags?

Answer 20

Perform a cold rollover check

Question 21

How often are preventative maintenance checks required?

Answer 21

Every 12 or 24 months.

Question 22

What do some refineries and petrochemical companies do regarding fan unit inspections?

Answer 22

Shut fan units down for inspection only during plant turnarounds.

Question 23

What method do plants depend on to monitor their equipment?

Answer 23

Vibration analysis.

Question 24

What is the purpose of vibration analysis in equipment monitoring?

Answer 24

To predict when a failure will happen.

Question 25

What can operational personnel request if vibration levels increase?

Answer 25

A more detailed inspection of the unit using vibration analysis equipment.

Question 26

What is done once vibration readings are taken?

Answer 26

They are compared to vibration guidelines to establish the source of the problem.

Question 27

What is the goal after establishing the root cause of a fan problem?

Answer 27

To make a repair that prevents a similar failure from happening again.

Question 28

What do some plants rely on instead of vibration equipment?

Answer 28

Maintenance personnel to troubleshoot fan problems.

Question 29

What senses should be used to locate fan problems when equipment is not available?

Answer 29

Listening and other senses.

Question 30

What device can be used to listen for unusual noises in fan components?

Answer 30

Mechanical stethoscopes.

Question 31

True or False: Vibration monitoring is only effective when equipment is offline.

Answer 31

False.

Question 32

Fill in the blank: Vibration analysis allows plants to ________ when a failure will happen.

Answer 32

[predict]

Question 33

What must be done once the hub is placed onto the shaft?

Answer 33

The set screws must be locked over the key.

Question 34

What tool should be used to place the set screws under load?

Answer 34

A torque wrench should be used to place the set screws under load without cracking or splitting them.

Question 35

What type of set screws may need to be used in some applications?

Answer 35

High torque set screws with extending square heads may have to be used in some applications.

Question 36

What should be used on the set screw threads?

Answer 36

Use an anti-seize component on the set screw threads.

Question 37

How should the fan wheel be mounted?

Answer 37

Mount the fan wheel onto the hub and shaft using the approved size and grade of fitted bolts.

Question 38

What should be done after mounting the assembly?

Answer 38

Mount the completed assembly on a dynamic balance machine and proceed to correct any imbalances.

Question 39

Why is balancing the fan important?

Answer 39

This procedure is done to reduce running fan vibration levels to the surrounding areas.

Question 40

How can the fan be balanced in place?

Answer 40

The fan can also be balanced in place using portable balancing instruments.

Question 41

What should be done after balancing the rotating assembly?

Answer 41

Place the balanced rotating assembly back into the inspected scroll and stand, and replace the scroll side plates.

Question 42

How should the rotor be lifted into its running position?

Answer 42

Lift the rotor up into its running position using nylon slings in a basket configuration on both ends of the shaft.

Question 43

What should the slings be attached to?

Answer 43

Attach the slings to a come-along that is attached to the lifting lugs welded onto the scroll.

Question 44

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

Answer 44

* Static * Velocity * Total pressure

Question 45

What is a manometer used for?

Answer 45

Most accurate way of measuring pressures in fan systems

Question 46

How can you remove static electricity generated by fans?

Answer 46

Using a grounding brush

Question 47

Name the two (2) major types of fans according to flow through the impeller.

Answer 47

* Axial * Radial

Question 48

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

Answer 48

Scroll

Question 49

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

Answer 49

* Wheel can be mounted between bearings * Can be mounted overhung

Question 50

How can control of air through fans be accomplished?

Answer 50

* Inlet louvers * Outlet dampers * Varying the fan speed

Question 51

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

Answer 51

To reduce vibrations

Question 52

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

Answer 52

Preventive maintenance

Question 53

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

Answer 53

Vibration analyzer

Question 54

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

Answer 54

Original equipment manufacturer's overhaul prints

Question 55

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

Answer 55

Inspect for cracks, make sure it's still to spec. ## Footnote Ensures reliability and safety of the equipment.

Question 56

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

Answer 56

The bore size is increased allowing easy install on cold shaft. ## Footnote Heating the hub expands it, facilitating easier installation.

Question 57

What is the purpose of balancing a fan rotor in a dynamic balancer?

Answer 57

To reduce vibration. ## Footnote Balancing helps maintain smooth operation and extends equipment life.

Question 58

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

Answer 58

Confirm there are no rubbing parts, no cracking sounds after fan overhaul. ## Footnote This step ensures that the fan rotor operates smoothly without interference.