Natural Gas

Question 1

What is Natural gas?

Answer 1

a. Found underground in a gaseous form
b. 85% methane and 11% ethane as well as other trace gases
i. 2% Nitrogen
ii. 1% Carbon Dioxide
iii. 1% other (sulfur, propane, butane, oxygen, helium, etc.)
c. Colorless, odorless, non-toxic
d. Ethyl Mercaptan is added to give the gas a rotten egg smell

Question 2

Physical properties of CNG

Answer 2

a. Vapor Density - .65 (lighter than air)
i. Propane – 1.55
ii. Butane – 2.0
iii. Ether – 2.55
b. Ignition Temperature – 1200F
i. Propane – 950F
ii. Butane – 900F
iii. Ether – 365F
c. Flammable limits (range) – 4-14%
i. Propane – 2.4-9.5%
ii. Butane – 1.8-8.4%
iii. Ether – 1.9-48%

Question 3

Vapor Density of CNG

Answer 3

.65

Question 4

Vapor density of other gases

Answer 4

i. Propane – 1.55
ii. Butane – 2.0
iii. Ether – 2.55

Question 5

Ignition Temperature of CNG

Answer 5

1200F

Question 6

Ignition Temperatures of other gases

Answer 6

i. Propane – 950F
ii. Butane – 900F
iii. Ether – 365F

Question 7

Flammable range for CNG

Answer 7

4-14%

Question 8

Flammable range for other gases

Answer 8

i. Propane – 2.4-9.5%
ii. Butane – 1.8-8.4%
iii. Ether – 1.9-48%

Question 9

Delivery of CNG

Answer 9

a. SWF distributes natural gas to customers in AZ, CA and NV
b. High pressure mains carry gas up to 1000psi (SWG calls any line over 60psi “high pressure”)
c. Regulation stations reduce high pressure from mains down to 30-60psi.
d. Typically distribution lines to homes flow at 30-60psi.
e. Residential regulators (gas meters) drop pressure down to .25psi as gas enters home.
f. Some appliances then regulate the pressure down to .125psi.
g. Gas pipes may be different sizes and can be steel or polyethylene. May also be different colors or use a sheath to protect the actual line.

Question 10

TFD response to gas leaks

Answer 10

a. SWG and TFD have a good working relationship
b. TFD has the ultimate authority in an incident involving a gas leak.
c. Notify SWG via Fire Alarm of
i. Actual address
ii. Nature of emergency (leak, broken pipe, fire, explosion, etc.)
iii. Location of command post
iv. Directions for entering area
d. Evacuate downwind occupants
i. As a general rule, hot zone should be defined as any area where the odor is present
ii. All personnel in the hot zone shall be in full PPE and with and SCBA
iii. Clipping in is situationally dependent. Try to stay upwind of the leak. Clip in when necessary.
e. Pull 1.75in line, wet down the area with fog patter to reduce static electricity risk (SWG uses dry chem extinguisher for protection).
f. If damage is distal to shut off valve, TFD can shut down the gas supply but must remain on scene until SWG arrives.
g. If gas is burning, don’t attempt to extinguish the fire.

Question 11

What should you notify SWG about during a gas leak?

Answer 11

i. Actual address
ii. Nature of emergency (leak, broken pipe, fire, explosion, etc.)
iii. Location of command post
iv. Directions for entering area

Question 12

What are some evacuation guidelines for CNG leaks?

Answer 12

i. As a general rule, hot zone should be defined as any area where the odor is present
ii. All personnel in the hot zone shall be in full PPE and with and SCBA
iii. Clipping in is situationally dependent. Try to stay upwind of the leak. Clip in when necessary.

Question 13

What are some facts about LPG gas?

Answer 13

a. Liquefied petroleum gas (LPG) is also used to fuel homes, businesses and vehicles. (usually propane)
b. Heavier than air.
c. Stage upwind and uphill.
d. As with CNG, vehicles running on these fuels are not required to have any markings indicating an alternative fuel is being used.