Emergencies 2 Natural Gas emergencies and fires

Question 1

PROPERTIES OF NATURAL GAS

General Knowledge

Answer 1

2.
Natural gas is comprised mainly of methane but also contains ethane, propane and nitrogen.
 Colorless
 Odorless
o Mercaptan is added to natural gas giving it a distinctive rotten egg odor
 Lighter Than Air
 Explosive Range 5% - 15%
 Ignition Temperature - 1163 Degrees Fahrenheit
 Non-Toxic
 Asphyxiant

Question 2

It is regulated down to 300 psi for transmission gas mains and regulated to lower pressures for distribution mains. Distribution gas mains are run under the streets and deliver either high pressure (60 psi), medium pressure (3 - 15 psi) or low pressure gas (¼ psi). Gas service pipes branch off of these mains to deliver gas from the main to
individual customers. High and medium pressure gas is regulated down to __ psi before it passes through the customer’s meter.
Fill in the blank

Answer 2

4.

1/4

Question 3

GAS PIPE COMPOSITION
 Transmission mains: Steel
 High Pressure Mains: Steel, Plastic
 Medium Pressure Mains: Steel, Plastic or Cast Iron
 Low Pressure Mains: Steel, Plastic or Cast Iron
 Gas Service Piping: Steel, Plastic or Copper
What type of gas pipe composition is allowed into structures?

Answer 3

5.
Steel (plastic and copper gas pipes are not
allowed inside structures)

Question 4

GAS METERS
Gas meters can supply individual occupancies or entire buildings.
Gas meters supply gas to most customers at ¼ psi. Exception: A few commercial customers receive gas at __ to __ psi.

Answer 4

6.

1-3 psi

Question 5

NATURAL GAS SHUT OFF VALVES
Most gas shutoffs are of the ¼ turn variety and can easily be shut off using the fork end of a Halligan tool, vice grips or pliers to turn the wing cock valve ¼ turn counter clockwise. When the key operating nut is ________ to the piping, it is in the open position. When it is ____________to the piping it is in the closed position.
Fill in the blanks

Answer 5

7.
Parallel
Perpendicular

Question 6

When would you find a simple wheel handled gas valve at an older installation where large amounts of gas are used by the customer?
Hintsize of the gas supply main in the street.

Answer 6

7.
In older installations where large amounts of gas are used by a consumer and the piping from the supply main in the street into the consumer’s building is 3” or larger, a simple wheel-handled gate valve may be found as the main shutoff valve.
This would be located just inside the building walls where the service enters the building. Depending on the size of the supply pipe and manufacturer, the wheel handle can vary from approximately 3” in diameter to approximately 10” in diameter.
o Caution: Members should be aware that these older multiple turn wheel-handle valves resemble water valves, or open stem and yoke valves, in the closed position. Care should be exercised that one is not mistaken for the other.

Question 7

What is the priority Order of Gas Shut-Offs at Gas Emergencies?
“AM-HECS

Answer 7

7.
“AM-HECS”
Appliance- ¼ turn
Meter Valve- ¼ turn
Head of Service Valve- most are ¼ turn valves
Exterior Gas Riser- ¼ turn
Curb Valve- ¼ turn-some older valves require 7 ½ to 15 turns until resistance is met
Street Valve-Do not operate street valves except under extreme caution & only under the direction of the F.D. Incident Commander after consultation with the utility company Rep.

Question 8

In some older high pressure gas services (Con Ed System), the main shut-off valve will require approximately __ to __ turns of the operating nut, in a clockwise direction to shut off the gas flow.

Gas service main High pressure shut-off valves “OTHER” than B.U.G. How many turns?

Answer 8

7 NOTE:
4½ to 5
OTHER=5 letters=4 ½ -5 turns

Question 9

The curb valve is usually found on the sidewalk side
of the curb. It shuts the gas supply to the building. It is usually recessed in from the curb and is covered with a 4” by 4” square or round brittle concrete or steel cover which may be sitting on top of a plastic or wooden plate. It is shut using the gas key found on Department apparatus. To shut the valve, remove or break the cover and plate, insert either the “U” shape or the square end of the gas key, whichever fits, onto the valve and in most cases, turn the key ____ turn clockwise.
Fill in the blank

Answer 9

6.

1/4

Question 10

Before shutting the gas curb valve, look into the valve box and if the valve is white, close it gently. A white valve means that it is?

Answer 10

6.
A plastic valve and plastic valve stops are easily broken by excess force.
National Grid supplies a white plastic insert for shutting down plastic valves. Con Ed uses the gas key as is to shut plastic valves. A white operating nut indicates a plastic curb valve.

Question 11

On the National Grid system, the curb valve is sometimes located across the street from the building it supplies. It may be found in the
street. How are these curb valves identifiable?

Answer 11

6.
Long Service - These curb valves are identifiable by an arrow cast into the cover pointing to the building it supplies. These also require a ¼ turn clockwise to close.

Question 12

Some older curb valves are gated and will require multiple turns to close. If ¼ turn does not shut the gas off, continue to turn the valve until resistance is
met. This may occur at between how many full turns?

Answer 12

6.
7½ to 15 full turns.
-Do not turn the valve more than 15 times.
Note: Before turning the key, place chalk or some other mark near the valve to indicate your start point. This will enable you to note when ¼ turn is completed.

Question 13

When can FDNY personnel operate a gas street valve?

Answer 13

7.
CAUTION: Do not operate street valves except under extreme circumstances and only upon direction of the Fire Department Incident Commander after consultation with the utility representative supervisor.

Question 14

When a plastic gas pipe is leaking firefighters can stop the leak by easily folding the leaking pipe.
True or False

Answer 14

8.
False
Although easily folded, firefighters should not
approach or attempt to fold leaking plastic gas pipe.
Static Spark (Polyethylene Plastic Pipe) Gas flowing out of a broken plastic pipe generates static electricity which builds up on the outside and inside surface of the pipe. Coming near to or touching a leaking plastic gas pipe could result in a spark that ignites the escaping gas.

Question 15

On what type of gas system would you find a peck vent?

Answer 15

6.
Peck Vent - found on high pressure services. If the regulator fails, this safety valve vents excess gas to the exterior of the building.

Question 16

For a Major Indor gas leak how many exposures shall be checked on both sides of the occupancy with positive gas readings?

Answer 16

11.
Check at least three exposures on both sides of the occupancies with positive gas readings for the presence of a gas odor or leak including above and below the suspected leak. Evacuate and ventilate as necessary.

Question 17

For a Major Indor gas leak:
Ventilate if it is safe to do so. If gas levels are above the flammable limits, they will drop into the flammable range as you ventilate.Where shall we start venting the bldg. when possible?

Answer 17

11.
Start venting at the upper levels of the building when possible and work your way down to the first floor and then out of the building.

Question 18

What are 2 indicators of an outdoor high pressure leak?

Answer 18

11.
Dirt and debris may be seen blowing into the air from an excavation. This would indicate a high pressure leak.
A loud roaring sound indicates a high pressure leak.

Question 19

When arriving on the scene of a serious gas incident prior to the arrival of gas utility personnel and finding gas readings in an ELECTRIC MANHOLE, the following information shall be requested from the utility company via the FDNY dispatcher:

Answer 19

11.
o The identity of the buildings(s) being supplied electricity by the involved manhole(s).
o If you detect gas readings inside buildings where the electricity enters the building (Electric Point of Entry or POE) request the location of the manhole that supplies electricity to the building and any other building(s) it supplies.
o Utilize this information to prioritize the checking of buildings for the presence of gas.

Question 20

Removal of MANHOLE COVERS by FDNY personnel may reduce the infiltration of gas into surrounding properties and shall be done only in compliance with the following guidelines: Removal of SEWER MANHOLE covers can be performed by FDNY personnel with the approval of whom?

Answer 20

11.

An on-scene Chief Officer.

Question 21

Removal of MANHOLE COVERS by FDNY personnel may reduce the infiltration of gas into surrounding properties and shall be done only in compliance with the following guidelines: Removal of ELECTRIC MANHOLE covers by FDNY personnel may be performed only when requested and approved by whom?
(2 Answers)

Answer 21

11.
Requested by a utility company gas representative on the scene and approved by an on-scene Chief Officer.
o Prior to requesting FDNY personnel to remove a manhole cover, the utility company gas representative must test the cover for stray voltage. If the cover is found to be free of the stray voltage, FDNY personnel may remove the cover
upon the orders of an on scene Chief Officer in conjunction with the utility company gas representative.

Question 22

Removal of MANHOLE COVERS by FDNY personnel may reduce the infiltration of gas into surrounding properties and shall be done only in compliance with the following guidelines:
What 3 times do we NOT pull a manhole cover?

Answer 22

11.
o DO NOT pull rectangular or square electric manhole covers.
o DO NOT pull any electric manhole covers if there is a manhole fire in the area or if a smoking or arcing is observed in an electric manhole or transformer vault.
o If in doubt as to which type of manhole is affected or if there is obvious smoke under pressure or electric arcing DO NOT remove the manhole cover.

Question 23

Round Manhole covers should be removed by two firefighters utilizing manhole hooks. Where will we find these hooks?

Answer 23

11.

Battalion vehicles carry two manhole hooks for use in removing electric manhole covers.

Question 24

The MSA Altair Digital Gas Meter will give us what 2 readings on the digital display?

Answer 24

13 B.
Carried by all non SOC Support Ladder Companies. It will give a digital readout of LEL (Lower Explosive Limit) for combustible gas and also is an oxygen sensor. It is to be used in conjunction with the Tiff meter if available.

Question 25

The DCGIs and Altair currently in use by the Department sound an alarm at __% LEL, the indoor action level, and a different alarm at __% LEL, the outdoor action level.

Answer 25

13.
10%
20%

Question 26

The utility company’s meters are not calibrated the same as FDNY meters. The utility company’s meters display percent of gas in air. When given a reading from any meter, be sure you know if it is given in LEL or in % in air 1% LEL on our meters converts to .05% of gas in the air on the utility companies meters. Using that conversion what is the percent of gas in air at 10% LEL (indoor action level)?
What is the percent of gas in air at 100% LEL?

Answer 26

13. Note:
    .50% gas in air
    5.00% gas in air

Question 27

The location of the curb valve may be indicated on the peck/relief vents which are located on the exterior of the building in high pressure systems. The vent is a device that will allow excess gas to be vented to the outside air if a malfunction of the pressure regulator valve in the high pressure system occurs. There should normally be no odor of gas at a peck vent. If an odor is detected, you must investigate to determine the source. A series of code letters and numbers will be found on or attached to these vents indicating the location of the curb valve. If the code reads 5-R-25,on a Con Ed peck vent the following procedure should take place to locate the curb valve:

Answer 27

14.
Starting at the left hand front corner of the house, as it is faced from the street, 5 feet would be measured off to the right. At that point 25 feet would be measured off at right angles toward the sidewalk. The curb valve should be located at this point.

Question 28

The National Grid Peck Vent location coding
system differs from Con Edison’s system. National
Grid uses two different systems. One method is
used in the Rockaways and another in the rest of
Queens, Brooklyn and Staten Island. In the Rockaways, you will find the numerals and letters on the peck vent, or on a tag hanging on the piping in the immediate area of thegas meter. If it reads L-30, R-25, M-10 where would you locate the curb valve?

Answer 28

14.
Starting at the left corner of house (facing it from
street) an arc is inscribed with a radius of 30’.
The same would be done from the right corner with
a radius of 25’. Where these two arcs intersect, would be the location of the curb valve. Then, 10 feet at right angles from this curb valve, in the direction of the street, would be the location of the gas main pipe running in the street parallel to the curb.

Question 29

What do the letters EFV inscribed on the peck vent tag mean?

Answer 29

14.
If the letters EFV are inscribed on the tag then there is no curb valve and where the lines meet denotes the location of an Excess Flow Valve which will automatically shut down the flow of gas when it senses an excess flow of gas.

Question 30

What do the letters NC inscibed on the peck vent tag indicate?

Answer 30

14.

The Letters NC on the tag also indicate that there is no curb valve present.

Question 31

In the rest of the areas served by National Grid excluding the Rockaways, there is a different coding system. It will read as follows: 15RLBW and 10FFW. How will we locate the curb valve using this system?

Answer 31

14.
 15 RLBW indicates 15 feet right of the left building wall,
 10FFW indicates 10 feet from the buildings front wall.
Starting at the left building wall, measure off 15 feet to the right. From this point, measure 10 feet at right angles toward the street. This is approximate location of the curb valve.