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Gas course > Combustion > Flashcards

Combustion Flashcards

1
Q

What Are The Components Of Natural Gas?

A

Methane - 90%

Ethane - 5%

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2
Q

What Are The Components Of Air?

A

Nitrogen - 78% (80%)

Oxygen - 21% (20%)

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3
Q

How Much Oxygen Is Required To Burn 1m3 of Methane (Gas)?

A

2m3 Of Oxygen Is Required

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4
Q

What Is The Complete Combustion Of Methane?

A

CH4 + 2O2 ~ CO2 + 2H2O
(Exothermic Reaction)
(Heat Given Off) (Blue Flame)

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5
Q

What Is The Incomplete Combustion Of Methane?

A

CH4 + 1.502 ~ CO + 2H2O

Lack Of O2) (Yellow Flame

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6
Q

What Is Carbon Monoxide?

A

1) Colourless, Odourless And Tasteless Gas
2) Very Hard To Detect
3) Poisonous
4) Accumulates In The Blood Stopping It’s Ability To Carey Oxygen
5) Carboxyhemoglobin - When Carbon Monoxide Is Carried By The Haemoglobin Instead Of Oxygen
6) Symptoms - Nausea, Headache, Exhaustion, vomiting and flu like symptoms

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7
Q

What Are The Signs Of Carbon Monoxide (CO)?

A

1) Staining Around Appliances( Black soot)
2) Yellow Flames On Burners
3) Condensation On Windows

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8
Q

What Is The Flammability Limit?

A

5% To 15% Gas In Air
5% Lower Explosive Limit (LEL)
15% Higher Explosive Limit (HEL)

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9
Q

What Is The Temperature Required To Ignite Natural Gas?

A

704*C

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10
Q

What Is The Rate At Which Gas Burns?(Flame Speed)

Linear Propagation

A

0.36m/s

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11
Q

Which Word Describes When The Flame Speed Is Too High?

A

Flame Lift (Overgassing)

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12
Q

Which Word Describes When The Flame Speed Is Too Low?

A

Lighback (Under-gassing)

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13
Q

Which Gas Goes Into Family 1?

A

Towns Gas (Manufactured Gas)

Used To Give Off Sulphur Which Is Poisonous And Wasn’t Very Efficient

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14
Q

Which Gas Goes Into Family 2?

A

Natrual Gas

Arrived During Mid 1960’s, Measured In Si, Mj, BTU/ft3, kw/m3) (10.76 kw/m3

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15
Q

Which Gas Goes Into Family 3?

A

Liquid Petroleum Gas (LPG) (Blowtorch)

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16
Q

What Is The Combustion Process?

A

Combustion Is An Exothermic Reaction Meaning It Gives Of Heat! In Order For It To Occur It needs The Following.

1) Fuel
2) Oxygen
3) Energy

The Fire Triangle

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17
Q

What Is A Calorific Value?

A

The Amount Of Energy Given Off When A Known Volume Of Gas Is Completely Combusted! (Burnt)

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18
Q

What Is The Calorific Value Measured In?

A

BTU/ft3 Or Mj/m3

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19
Q

What Is The Volume Of Natural Gas?

A

38.72 mj/m3

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20
Q

What Is A Wobbe Number?

A

The Figure Used To Indicate The Heat Produced From A Burner! (Burner Design)

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21
Q

What Does The Heat Produced From A Burner Depend On?

A

1) Gross Calorific Value Or The Gas
2) Specific Gravity
3) Size and shape of injector orifice
4) Gas Supply Pressure To The Injector

22
Q

What Is The Definition Of Stoichiometric Combustion?

A

Perfect Combustion

23
Q

What Are The Stoichiometric Air Requirements?

A

9.8 Gas : 1 Air

This Can Only Be Achieved Under Strict Laboratory Conditions

24
Q

What Is Natural Draught?

A

The Natural Movement Of Air

No Fan

25
Q

What Is Vitiation?

A

Contaminated Air Coming Back Onto The Burner

Products Of Incomplete combustion

26
Q

What Is Flamechilling?

A

When The Flame Cools Down Below 704*c Causing It To Not Burn Correctly Which Leads To Incomplete Combustion

27
Q

What does Pre- aerated Mean?

A

Air and Gas Mix Before Being Burnt!

28
Q

What Does Post - Aerated Mean?

A

Air And Gas Mix After Being Burnt

29
Q

What Are The Signs Of Combustion Problems?

A

1) A Report Of A Smell Spillage ( Aldehydes Cause Smell)
2) Soot (Yellow Or Brown Marks)
3) Soot Deposits On Heat Exchanger
4) Condensation
5) Flame Lift (Over-gassed)
6) Pilot Lights That Frequently Blow Out

30
Q

What Is The Definition Of Flame Impingement?

A

When Flames Keep Searching For Oxygen And End Up Connecting Together Which Can Lead To Incomplete Combustion

31
Q

What can Over Gassing And Under Gassing Lead To?

A

They Can Both Lead To Incomplete Combustion

32
Q

How Much Volume Of Air Does 2 Volumes Of Oxygen Need?

A

10m3 Of Air

33
Q

What are 5 causes of incomplete combustion?

A

1) Over-gassing
2) Under-gassing
3) Vitiation
4) Flame Chilling
5) Flame Impingement
6) Poor Flueing

34
Q

What Is The ECV Used For?

A

It is used to turn of the gas

35
Q

Where Should CO Detectors Be Installed?

A

1) 150 mm from the ceiling
2) 300 mm from the wall
3) 1.8 to 3.0 m from the appliance
4) 1.5 m from the floor

36
Q

What do you do If the CO detector activates?

A

1) Turn Of The Appliance
2) Ventilate the room
3) Evacuate The Property
4) Try repair of possible if not then disconnect it

37
Q

What are the 3 Classifications of flues?

A

1) Flueless (Type A)
2) Open (Type B) ( B1 & B2)
3) Room sealed (Type C)

38
Q

What Are The Four Components Of An Open Flue?

A

1) Primary
2) Down Draught Diverter
3) Secondary Flue ( Main)
4) Terminal ( Chimney Outlet)

39
Q

What type of pressure is created from downstream Fan?

A

Negative

40
Q

What type of pressure is created from an upstream fan?

A

Positive

41
Q

What is the minimum vertical measurement required for a chimney?

A

600mm

42
Q

How much degrees should any bend in a chimney be less than?

A

45*

43
Q

What should the minimum circular cross sectional area of a chimney be?

A

12,000 mm2 or 16,500 mm2

44
Q

How Do Your Perform A Let-by Test?

A

1) Test 7-10 mbar for 1 min (Let-by Test)
2) Read Gauge ( bottom of the miniscus at 0 line)
3) Check gauge ( test it by blowing in to it or hold it up)
4) Set up gauge ( Make it vertical tube must be straight) ( Can’t hold gauge because of body temperature)
5) Open the ECV 7-10 mbar for 1 min ( take reading on the left and right add them together then divide by 2) ( No movement is allowed on a let-by test)
6) Use air clamps ( bubbles occur if there’s a leak) ( Uncontrollable gas escape occurs you should cap it first, LDF it then call 0800 111 999)

45
Q

How do you perform a temperature stabilisation test?

A

Test for 1 minute at 20-21mbar

46
Q

How do you perform a Tightness Test?

A

Test at 20-21mbar for 2 minutes this is because at 22-23mbar the regulator locks up. After this you should

1) Disconnect The gauge
2) Put The Test Nipple Back In
3) Put The Gas On
4) LDF The Test Nipple
5) LDF The Anaconda, The ECV( Emergency Control Valve) and any other service pipe you can see

47
Q

What Is The Specific Gravity Of Natural Gas?

A

0.58

48
Q

What Is A Primary Flue?

A

It Is Part Of The Appliance Combustion Chamber

49
Q

What Is A Down Draught Diverter?

A

It Stops Air Going Back Onto The Burner And Has The ASD And VSD Connected To It

50
Q

What Is A Secondary Flue?

A

Assists In Preventing Down Draught, Rain Entering And Birds Resting In The Flue

Gas course (5 decks)

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