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Gas > Chapter 1-2 > Flashcards

Chapter 1-2 Flashcards

1
Q

Natural gas has a boiling point of approximately what ?

A

-258f

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2
Q

Odourant added to natural gas to give it a “rotten eggs smell” ?

A

Mercaptan

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3
Q

Natural gas is approximately what % of methane ?

A

85-90%

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4
Q

The specific gravity of natural gas is approximately what ?

A

0.60

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5
Q

The specific gravity of air is equal to what ?

A

1.0

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6
Q

What do flame characteristics indicate ?

A

The quality of combustion that is taking place

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7
Q

Required air/gas ratio is what ?

A

The cubic feet or cubic metres required to burn one cubic foot of natural gas without having any excess air found in the products of combustion

10/1
10 being air 1 being natural gas

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8
Q

What does a yellow flame indicate ?

A

Indicates there is no premixing of natural gas with the required air for combustion

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9
Q

What does a blue flame indicate ?

A

A higher temperature and is the result of some premixing of the fuel with the required air for combustion

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10
Q
  1. What is primary air ?
  2. What is secondary air ?
A
  1. Air mixed with the fuel prior to its ignition (no flame)
  2. Air mixed with fuel around the flame as in the yellow flame
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11
Q

What is excess air ?

A

Air supply above the ideal or theoretical amount

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12
Q

What is the composition of air ?

A

20% oxygen
80% nitrogen

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13
Q

What is the heating value for natural gas ?

A

1000 BTU/cf

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14
Q

How is the gas consumption of an appliance indicated ?

A

Rated on a hourly basis
1. Flow Rate = CFH
2. Heat Rate or Input Rate = Btuh

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15
Q

What is the Input Rate/Hear Rate formula ?

A

Input Rate (Btuh) = heating value of the gas x gas flow rate

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16
Q

Flow Rate formula ?

A

Flow Rate (cfh) = Input Rate / Heating value of the gas

17
Q

What is the flame temperature for Natural Gas ?

A

3500f

18
Q

What is the flame speed for natural gas ?

A

1ft/sec

19
Q

What is the ignition temperature for natural gas ?

A

1200f

20
Q

What are the limits of flammability?

A

Upper and lower limits percentage of air/gas mixture that will support combustion
Lower limit = 4%
Upper limit = 14%

21
Q

When the combustion of the fuel is not controlled within the confines of a burner system, the limits of flammability can be called the what ?

A

Explosive limits
Lower and upper explosive limits
L.E.L = 4%
U.E.L = 14%

22
Q

Pressure of a gas is determined by what two significant factors ?

A

Volume and Temperature

23
Q

What is Boyles Law ?

A

The volume of a gas varies inversely to the pressure, provided the temperature of the gas remains constant

24
Q

What are Charles laws 1 and 2 ?

A
  1. The pressure of a gas varies directly with the temperature, provided that the volume of the gas remains constant
  2. The volume of a gas varies directly with the temperature provided that the pressure of the gas remains constant
25
Q

Definition of flow

A

Movement of gas from a high pressure area to a low pressure area

Relative to the pressure difference between two area

26
Q

Definition of pressure drop

A

A partial loss of total energy or type of “resistance”

27
Q

Pressure drop depends on what 5 factors ?

A
  1. Length of run of gas pipe
  2. Size of the gas pipe
  3. Number of fittings
  4. Size of the flow rate
  5. Specific gravity of the gas
28
Q

What is absolute pressure ?

A

Pressure measurement of a gas from a perfect or complete vacuum.

29
Q

What is atmospheric pressure ?

A

Pressure the atmosphere exerts on the earths surface.

Measured in pounds per square inch absolute
(PSIA)

30
Q

What is gauge pressure ?

A

Pressure measurement taken by a pressure gauge in which zero is calibrated at local atmospheric pressure

31
Q

How to determine pressure drop in a gas line

A

Working pressure at gas meter outlet - working pressure at appliance

Gas (3 decks)

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