Fans And Ventilation

Question 1

What instrument is used to measure fan pressure?

Answer 1

Manometer

Reads Three types of pressure developed by fans: static, velocity, and total pressure depending on which way it is connected to the outlet duct

Question 2

What is static pressure?

Answer 2

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

Question 3

What is velocity pressure?

Answer 3

The pressure over and above static pressure. It is created by the impact of air flowing through a duct and is felt only by the surfaces that the air actually strikes

Question 4

What is total pressure?

Answer 4

When you add velocity pressure and static pressure

Question 5

What are the two types of fans?

Answer 5

Centrifugal

Axial flow

Question 6

What are the tree types of axial fans?

Answer 6

Tube axial

Vane axial

Propeller

Question 7

What are the three variations of mechanical draft?

Answer 7

Induced draft - pressure in the furnace is below atmospheric pressure. Locate fan between boiler and chimney.

Forced draft - boiler is cooled

Balanced draft - has forced draft fan and induced draft fan.

Question 8

Where is the fan placed on a furnace to create induced draft?

Answer 8

Between the boiler and the chimney

Question 9

What are the four general approaches to pollution control?

Answer 9

Intermittent reduction

Wider dispersion

Reduction of pollutants

Change the industrial process

Question 10

What is the preferred approach of pollution control?

Answer 10

Change the process

Question 11

What organization sets the rules for Handling of dangerous materials?

Answer 11

WCB

Question 12

What types of equipment are used to control pollutants?

Answer 12

Filters

Electrostatic precipitators

Cyclones

Mechanical collectors

Scrubbers

Absorbers

Burners

Ultraviolet

Question 13

Describe the primary treatment of wastewater?

Answer 13

Screen out large debris
Skim off floating debris
Settle out suspended material

Question 14

What is secondary treatment of wastewater?

Answer 14

Biological treatment is used to breakdown organic matter then skimmed off

Question 15

What does advanced treatment remove?

Answer 15

Nutrients that promote algae growth

Industrial pollutants (heavy metals and non biodegradable organic materials

Question 16

Why are small particles so dangerous?

Answer 16

They can imbed deep into the lungs

Question 17

What are the four techniques to remove particles from the air?

Answer 17

Cyclone separator

Wet scrubber

Electrostatic precipitator

Bag-house

Question 18

What size particulates in oil smoke?

Answer 18

.01-1

Question 19

What mechanisms are used to collect solid pollutants from the air?

Answer 19

Wet and dry collectors

Gravity settling chambers

Gravity spray towers

Cyclones

Muti clone collectors

Centrifugal spray scrubbers

Question 20

Why special problems are present with wet particulate collectors?

Answer 20

Create water pollution

Subject to corrosion

Can freeze

Question 21

What are the advantages/ disadvantages of gravity settling chambers?

Answer 21

Very low energy cost
Low maintenance cost
Low installation cost
Excellent reliability
High efficiency

Very large
Only used for course particulate

Question 22

What is the advantage of a multi clone collector?

Answer 22

Collect more efficiently without using more power

Question 23

Is a bag house a primary or secondary filter?

Answer 23

Secondary small particles will always escape

Question 24

What is an advantage and disadvantages of bag houses?

Answer 24

Can remove 100percent of particles as fine as .4microna

Can be combustible
Bags are effected by humidity and chemicals
Expensive

Question 25

Industrial plant and building require efficient air and gas movement through fans. From shop ventilation to material handling to boiler applications, fans are necessary for process support and?

Answer 25

Human health

Question 26

How is static pressure converted to velocity pressure?

How is velocity pressure converted to Static pressure?

Answer 26

By gradually decreasing the cross sectional area of the duct(converging)

By increasing the cross sectional area of the duct (diverging)

Question 27

Fans can be used in series or parallel. Series fans are used to?

Parallel fans are used to?

Answer 27

Fans in series are used to increase outlet pressures

Parallel fan arrangements are used where a spare or backup fan is needed

Question 28

What are some advantages of mechanical draft fans?

Answer 28

• independent of atmospheric air temperatures
• they are independent of chimney temperature. Natural draft this is a very important factor
• can be regulated more accurately than natural draft.
• they have better draft regulation, which increases efficiency of combustion

Question 29

Three types of backward inclined blade fans?

Answer 29

Flat blade - most robust

Curved blade - more efficient than flat blade

Air foil - most efficient of all. Can exceed efficiency’s of 85%.

All backward inclined fans require less HP to driver specific air volume and are more efficient than forward curved fans.

Question 30

Forward blade fans (squirrel cage) are typically used in _______ fans?

Answer 30

Small fans

Residential heating, ventilation, HVAC applications

Question 31

Ideal fan blade for high pressure service?

Answer 31

Radial blade fans

• easy to maintain
• flat blade shape limits material build up and are capable of handling high particulate airstreams such as dust, wood chips and metal scrap.

Question 32

Open wheeled radial blade is meant for?

Answer 32

Handling air containing small wood blocks, silage(paper trim), or similar materials.

Question 33

Open wheel and backplate radial fan blades can handle air containing small wood blocks, silage(paper trim) and similar materials. What advantage does the back plate wheel have?

Answer 33

• adds strength and rigidity
• prevents long, fibrous, or stringy materials from wrapping around the wheel

Question 34

Open wheel and backplate radial fan blades can handle air containing small wood blocks, silage(paper trim) and similar materials. What advantage does the back plate wheel have?

Answer 34

• adds strength and rigidity
• prevents long, fibrous, or stringy materials from wrapping around the wheel

Question 35

Air flow in axial fans is parallel to the shaft axis. What are the three main groups?

Answer 35

Propeller fan - typically used in air-cooled condenser, unit heaters, exhaust fans for ventilation purposes

Tube axial fan - heavier duty can be mounted within ducting. Loose energy due to friction because of air swirl.

Vane axial fan - similar to tube axial fan but outlet guide games to eliminate most of the airflow swirl making it much more efficient

Question 36

How come induced fans require more maintenance then forced draft fans?

Answer 36

Induced fans run at significantly higher temperatures and are subjected to boiler ash that builds up on the blades, creating cracks and imbalance problems.

Question 37

Correct outlet duct length creates good _________ flow. Achieving good laminar flow is important before putting any bends in.

Answer 37

Laminar flow

Question 38

When performing maintenance on fans you would shut the fan down then ____ and lock it out electronically. Sometimes the inspection cover is removed and the fan wheel is blocked to prevent what?

Answer 38

Isolate

Prevent backward rotation due to reverse flow through ducts and dampers