Flashcards in TB Emergencies 2 Natural Gas Emergencies & Fires Deck (24):
The properties of Natural gas are?
Lighter than air
Explosive range 5-15%
Gas is delivered into NYC at ~700-1400 psi. It is regulated down to 300 psi for transmission mains and to lower pressures for distribution mains. Distribution mains are supplied at 3 different levels what are they?
High pressure 60 psi
Medium Pressure 3-15 psi
Low pressure 1/4 psi
Gas meters supply gas to most customers at 1/4 psi Except?
A few commercial customers receive gas at 1-3 psi
A peck Vent is found on High pressure services. Smelling gas from this vent is normal. TRUE OR FALSE?
FALSE it should only vent gas when the regulator fails. If odor is detected, you MUST investigate to determine the source
MOST gas valves are the 1/4 turn variety and require 1/4 turn COUNTER CLOCKWISE to shut off. In older installations where large amounts of gas are used and the main is 3" or larger you would expect to find what kind of shut off valve?
A simple wheeled gate valve may be found. Depending on the size of the supply pipe and manufacturer the wheel handle may be 3" up to 10" in DIAMETER
The priority order of gas shutdown is"
At My Home Every Good Child Succeeds
Head of Service
Exterior Riser Valve
Gas shut off key
The old head of service valves in high pressure systems require closing opposite the norm and are closed in the CLOCKWISE rotation. How many turns of the operating nut are required?
~4 1/2-5 turns CLOCKWISE
Curb valves are usually found on the SIDEWALK side of the curb and they require a 1/4 turn to close if you find a white valve this indicates?
That the valve is plastic and that the stops are easily broken by excess force.
Nation Grid has an insert for shutting these valves Con Ed does not.
On the Nation Grid system the curb valve is sometimes located across the street from the building it supplies. This is called a long service and requires 1/4 turn clockwise to close. Some older curb valves are gated and will require multiple turns to close. How Many?
7 1/2- 15 DO NOT turn the valve more than 15 times
Street valves are located on the street side of the curb. On the nation grid system these valve covers are identified by an ID number stamped on the NORTH side of the cover but these numbers may be obscured. What shape would you expect these covers to be?
Round or Square in a variety of sizes 9" or larger.
They are usually not present on low pressure gas systems
Have the utility company close all valves beyond the curb valve
DO not operate STREET valves EXCEPT under extreme circumstances and only under direction of the FDNY IC after consult with the utility supervisor TRUE or FALSE?
Firefighters should not approach or attempt to fold plastic gas pipe due to static spark. Units shall ALWAYS test for the presence of Natural gas with a combustible gas indicator and once you turn off a gas valve you shall NEVER turn it back on. When should you turn on your Fire Department issued intrinsically safe flashlight?
Before entering the building.
ALWAYS consider the possibility that leaking gas is migrating into buildings and other structures.
The star valve may be found between the head of service and the gas meter. Its rarely found today and is unreliable and should not be used. TRUE or FALSE?
Minor indoor gas leaks are minor but can escalate quickly. You should wear full PPE and wear your facepiece when operating in a gas atmosphere. If gas is leaking indoors and not burning the gas supply should be shut off and the area ventilated. Fog nozzles may be used however you should not us dept fans. Why?
They are not intrinsically safe
Major indoor gas leaks are not as common as minor indoor gas leaks. At least 3 exposures on both sides of the occupancies with positive gas readings INCLUDING above and below the leak should be checked. Where would you start venting if the levels are above the flammable range?
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
An outdoor gas leak may be indicated by an opaque cloud rising from the ground at the site of the leak. If a load roaring sound is heard or dirt and debris are seen blowing into the air from an excavation this would indicate?
A high pressure leak.
If gas readings are found in electric, gas or sewer manholes the surrounding structures MUST be checked. When arriving on the scene at a SERIOUS gas incident prior to the arrival of the gas company and finding readings in an ELECTRIC manhole. What info shall be requested?
The identity of the buildings supplied by the involved manholes.
If you detect gas at the Point of Entry (POE) request the reverse...what manhole supplies the electric to the building and what other buildings are serviced by same
Sewer covers may be removed with the approval of a CHIEF OFFICER. Electric manhole covers may only be removed when?
Approved by the GAS company rep and approved by the CHIEF OFFICER
Round covers should be removed by 2 members Do not remove rectangular or square covers
If in doubt as to which type of manhole cover is affected or there is obvious smoke under pressure or electric arcing DO NOT remove the cover. TRUE or FALSE?
If gas is burning do not extinguish it... protect exposures with fog streams and wait for the utility company to stop the flow. Shutting down construction equipment and vehicles is advised/ TRUE or FALSE?
False construction equipment being shut down can cause a spark and be a source of ignition
DCGI's and Altair currently used by FDNY sound an alarm at 10% LEL indoor level and 20% outdoor level. FDNY will begin evacuation at 10% if?
We are unable to reduce the LEL immediately via ventilation and shutting valves.
Remember the utility companies are calibrated differently than ours % gas in air vs % LEL
In the Nation Grid system you may see a tag hanging from the peck vent which may have the letters EFV or NC on the tag. What do they indicate?
That there is no curb valve present
The Altair is calibrated to methane. This meter should not be use to detect gases OTHER than natural gas. The self check takes about 40 seconds to complete. Upon completion the meter will emit a vibrating pulse and a flashing green LED every?
30 seconds to alert the operator that the meter is operating.
To zero the meter press and hold the rest button for 3 seconds