Emergencies 2 Natural Gas emergencies and fires Flashcards
PROPERTIES OF NATURAL GAS
General Knowledge
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
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
4.
1/4
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?
5.
Steel (plastic and copper gas pipes are not
allowed inside structures)
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.
6.
1-3 psi
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
7.
Parallel
Perpendicular
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.
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.
What is the priority Order of Gas Shut-Offs at Gas Emergencies?
“AM-HECS
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.
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?
7 NOTE:
4½ to 5
OTHER=5 letters=4 ½ -5 turns
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
6.
1/4
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?
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.
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?
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.
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?
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.
When can FDNY personnel operate a gas street valve?
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.
When a plastic gas pipe is leaking firefighters can stop the leak by easily folding the leaking pipe.
True or False
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.
On what type of gas system would you find a peck vent?
6.
Peck Vent - found on high pressure services. If the regulator fails, this safety valve vents excess gas to the exterior of the building.
For a Major Indor gas leak how many exposures shall be checked on both sides of the occupancy with positive gas readings?
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.
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?
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.
What are 2 indicators of an outdoor high pressure leak?
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.
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:
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.
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?
11.
An on-scene Chief Officer.
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)
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.
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?
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.
Round Manhole covers should be removed by two firefighters utilizing manhole hooks. Where will we find these hooks?
11.
Battalion vehicles carry two manhole hooks for use in removing electric manhole covers.
The MSA Altair Digital Gas Meter will give us what 2 readings on the digital display?
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.
