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Book 29 - 2020 > Book 29 Gas Utilities > Flashcards

Book 29 Gas Utilities Flashcards

1
Q

Book 29 Gas Utilities

Pure natural gas is completely odorless.

odorant is added so that as little as ___-percent of natural gas in the air can be detected.

The common odorant is a ______ mix, which is used in solution of one pint per million cubic feet of gas.

A

one

Mercapitan/Thiophane

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2
Q

Book 29 Gas Utilities

Natural gas is non-toxic and is not considered hazardous when inhaled in limited concentrations.

However, in quantities large enough to displace oxygen,
asphixiation can occur.

A

reference

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3
Q

Book 29 Gas Utilities

Natural gas is _____ than air

A

lighter

escaping natural gas rising and rapidly dissipating.

This is a distinct safety advantage over heavier fuels such as butane and propane, which are heavier than air; and when escaping, it will collect in low areas.

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4
Q

Book 29 Gas Utilities

Natural gas also has an ignition temperature of ___ degrees

Flammable range between ___ and ___ percent.

A

1100

4 and 14

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5
Q

Book 29 Gas Utilities

Transmission lines maintain pressures up to ____ psi and use pressure booster compressor stations, at specific intervals, to maintain appropriate flow and pressures.

A

1000

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6
Q

Book 29 Gas Utilities

Transmission lines bring natural gas into the Southern California area and vary in diameter from ___ to ___ inches.

A

12 to 36”

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7
Q

Book 29 Gas Utilities

Natural gas is then distributed to Gas Company customers by distribution mains.

The gas is carried by service lines, as medium pressure, which normally does not exceed ___ psi.

A

60

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8
Q

Book 29 Gas Utilities

At the service meter (Meter Set Assembly), the pressure is reduced to a low pressure (approximately ___ psi.).

A

1/3

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9
Q

Book 29 Gas Utilities

Distribution mains are generally polyethylene and account for a high percentage of the mains in use today.

Older existing distribution mains are made of steel or copper, but are rare to find.

Polyethylene mains are color coded to identify the pipe as
transporting natural gas. These pipes are yellow, which is the national color code for newer installations. Older installations of plastic pipe can be pink (salmon beige), or orange in color.

Polyethylene will have a wire running the length of the pipe, for locating plastic gas lines, below ground.

Above ground gas lines must be made of steel and cannot be plastic.

Distribution mains are normally located underneath city streets, parallel to curbs, under grassy parkways, between the curb and sidewalk, and occasionally in alleys.

A

reference

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10
Q

Book 29 Gas Utilities

A ring on the stopcock valve indicates a ______.

A band on the stopcock valve indicates the service line is plastic.

A

branch service

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11
Q

Book 29 Gas Utilities

A flat washer on the stopcock valve indicates that the?

A

service line is a plastic pipe inserted inside an older metal pipe.

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12
Q

Book 29 Gas Utilities

Next, up the riser, is a flat circular device called a “regulator” that reduces medium gas pressure (up to 60
psi) to a relatively low level of approximately __ psi.

Next are pipes and fittings, leading to the gas meter. The meter measures the amount of gas that is used.

After the meter, gas flows through pipes and fittings into the structure.

A

1/3 psi

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13
Q

Book 29 Gas Utilities

A “G”, required by Cal-OSHA, marks the location where the
service line passes beneath the curb and indicates which side of the building the MSA is ocated.

A

reference

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14
Q

Book 29 Gas Utilities

Some MSA’s may be equipped with an emergency vibration-sensitive shut off device known as an earthquake
valve. These valves are marketed by private industry and are normally mounted on the discharge side, right side as you face the meter, of an MSA.

Personnel should recognize and understand that a swift-kick may possibly shut off the flow of gas, but only in the event of a damaged or frozen stopcock;

A

reference

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15
Q

Book 29 Gas Utilities

Industrial shut-off valves, known as Nordstrom valves, are used for high pressure applications.

Some industrial installations have gate valves with wheel handles that may be turned clockwise to close.

A

reference

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16
Q

Book 29 Gas Utilities

Meters under the sidewalk, called curb meters, are common in commercial areas. The lid over the curb meter space is made of lightweight concrete, or fiberglass set in a metal frame, and is easily identified by its gas company markings.

A

reference

17
Q

Book 29 Gas Utilities

BRANCH SERVICE

In some commercial areas, multiple structures may be commonly serviced by a single service pipe called a standard service main.

A metal ring identifies this branch service.

The occupancy that is further from the supply main is a standard service, and the other occupancies are branch services.

All MSA’s that are served from the branch main will be identified by a ring at the stopcock.

A

reference

18
Q

Book 29 Gas Utilities

Stuck tangs can be approached in EMERGENCY CONDITIONS as follows:

  1. Use two wrenches, one on the tang and the other on the backing nut. Holding the tang steady, loosen the backing nut one ____ only! If the backing nut is loosened too far, the core can fly out, leaking medium pressure gas, 40 to 60 psi.
  2. Give the backing nut a tap with a non-metallic hammer, freeing the core.
  3. Turn the tang, one-quarter turn, to stop the flow of gas; a half-turn will continue to let the gas flow.
  4. Tighten the backing nut to lock the core in the “OFF” position.
A

one-quarter turn only!

19
Q

Book 29 Gas Utilities

The ___ Valve is a larger version of a residential stopcock. It is used on high-pressure risers and piping, at industrial/ commercial sites, and comes in various sizes to fit different diameter pipes.

A

Nordstrum Valve

20
Q

Book 29 Gas Utilities

CURB VALVES

Also referred to as an Emergency Shutoff Valve. These valves can be installed in addition to stopcocks at public assembly occupancies such as schools, hospitals, churches, etc. They are ___ to ___ feet underground and under a small metal, concrete or fiberglass lid; with “Gas Company” markings in raised letters.

A

They are two to three feet

21
Q

Book 29 Gas Utilities

The greatest danger results from gas leaks inside structures, due to the potential for ignition and explosion.

A

reference

22
Q

Book 29 Gas Utilities

For faint odors, always check the condition of pilot lights as a first action.

A

reference

23
Q

Book 29 Gas Utilities

Tactical considerations at an inside leak should include the following considerations:

Determining necessity and extent of evacuation.

Remove all sources of ignition. Avoid operating electrical switches. Turning a switch “ON” or “OFF”, can cause sparking. Also, avoid walking on carpets in dry weather to prevent sparks from static electricity.

Turn off appliance valve located at the connection from the appliance to the customer house line.

Open windows after all sources of ignition have been eliminated. This ventilation can bring the gas into the proper explosive mixture with air.

Searching for occupants who may be overcome by gas.

If it is determined to be unsafe to enter the structure, consider the following:

Turn off gas at the meter.

Spot apparatus in safe zones.

Establish a water supply and prepare for fire suppression operations.

A

reference

24
Q

Book 29 Gas Utilities

Leaks outside structures

The Fire Department’s role at the site is to maintain public safety. This usually means eliminating potential sources of ignition until the leak is stopped.

A

reference

25
Q

Book 29 Gas Utilities

Previously, The Gas Company used to teach its members a technique, known as the bend-back method, for controlling the flow of gas in small diameter pipes. This method is now against The Gas Company’s policy, due to a recognized danger to their employees. There is an extremely high potential for creating a static charge that usually accompanies the increased pressure of gas flowing from the restricted opening as the pipe is bent over.

Crimping plastic pipe is acceptable as long as all tools used to work on plastic pipe are grounded.

Redwood plugs can be driven into various diameter steel pipes with a rubber mallet. This method, redwood plugs, does not work with polyethylene pipe.

A

reference

26
Q

Book 29 Gas Utilities

if any liquid flows from a natural gas pipe, do not let it touch your body. Treat the liquid as a hazardous material and notify a Hazardous Materials Company.

A

reference

27
Q

Book 29 Gas Utilities

Fog down the plastic pipe with a wetting agent such as wet water to prevent ignition from static electricity. Water alone tends to bead up and run off of polyethylene pipe, thus reducing the effectiveness of water.

A

reference

28
Q

Book 29 Gas Utilities

Considerations at a natural gas fire should include:

A

–Protect exposures.

–Generally, let the gas burn until the supply is shut off.

–If necessary, control evacuation and maintain site security.

–Notify The Gas Company.

Small fires may be extinguished with dry chemical, or CO2 if necessary, to approach a shut off valve.

For larger fires, fog streams can be used to approach any valves.

29
Q

Book 29 Gas Utilities

HYDROGEN SULFIDE

A toxic gas that, on rare occasions, is present in leaks at natural gas compressor stations or at underground storage fields.

A

reference

30
Q

Book 29 Gas Utilities

A ___ on the stopcock valve indicates a branch service.

A _____ on the stopcock valve indicates that the service line is a plastic pipe inserted inside an older metal pipe.

A ____ on the stopcock valve indicates the service line is plastic.

A

ring

flat washer

band

Book 29 - 2020 (9 decks)

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