Utility Emergencies Flashcards
What should color coded surface marks indicate?
- Name, initials, or logo of the company that owns or operates the line and the width of the line if it is greater than 50 mm (2 inches).
- Locations and route of buried lines.
APWA
American Public Works Association
Red
Electric, cable, conduit, and lighting cable
Yellow
Gas, oil, steam, petroleum, or gaseous materials
Orange
Communications, alarm, or signal lines, cable or conduit
Blue
Potable water
Purple
Reclaimed water, irrigation and slurry lines
Green
Sewer and drain lines
Pink
Temporary survey markings
White
Proposed excavation
What is methane
A simple hydrocarbon consisting of hydrogen and carbon
Define vapor density
The weight of a given volume of gas compared to the weight of the same amount of air at the same temperature and pressure.
What is the vapor density of methane?
0.55
What will heavy concentrations of natural gas do?
Displace the oxygen, causing drowsiness and suffocation from asphyxiation.
What are some hazards of natural gas?
Colorless and odorless. Mercaptan is added to it to give it a detectable scent. Natural gas in transmission pipelines and rail cars is not odorized, so leaks that do occur can go undetected creating a significant danger to first responders.
What is the flammable range for natural gas (methane)?
5% - 15%
What is the ignition temperature for natural gas (methane)? What can it be ignited by?
The ignition temperature for natural gas is about 1200° F and can easily be ignited by something as simple as a doorbell or a cell phone.
What is the expansion ratio of natural gas (methane)? What is a potential associated risk when in a container?
The expansion ratio of liquefied natural gas to a gas is 600:1. When liquefied gas cylinders are exposed to heat from fire impingement there is a potential for a BLEVE to occur.
What is the operating pressure of gas lines vs transmission lines?
Gas lines typically have operating pressures of 0.25 to 55 pounds per square inch (psi). The transmission lines range in size from 6” to 30” and have pressures up to 450 psi. These lines can generate 2,000 to 24,000 volts of static electricity.
What is the safest way to move natural products?
Pipelines remain the safest, most efficient, and economical way to move these natural resources.
What are some indicators of a pipeline leak?
- A hissing or roaring sound.
- Any unusual odor near the pipeline.
- Dead or discolored vegetation in an otherwise green location.
- Fire coming from the ground or appearing to burn above the ground
- Dirt being blown or appearing to be thrown into the air.
- Water bubbling or being blown into the air at a pond, creek, or river.
- A dry spot in a moist field.
What is the proper sequence for shutting off gas?
- At the appliance (if can be safely done).
- At the meter.
- At the curb box.
What is the general rule for positioning on a gas leak?
The general rule for apparatus positioning is no closer than 100 feet for the first arriving unit and a minimum distance of 300 feet for all other incoming fire apparatus
What is an outside gas leak and when should it be upgraded to a Hazmat response?
An outside gas leak is any flammable gas leak that has originated outside a structure and the gases have not migrated into the building of origin or exposures nearby. The call should be upgraded when the break is in a line that is reported to be over 2” in diameter.
When should you operate street valves?
Never
After turning off a gas valve should you turn it back on? Explain.
If a gas valve has been turned off, do not turn it back on, this could cause an explosion.
How far from the hot zone should people evacuate?
The DOT Emergency Response Guide (ERG) suggests an evacuation distance of 330 feet. This may include evacuating buildings located within or near the zone.
When should clamping or crimping a leak be considered? On what sized line?
Only in extreme cases. This should only be considered for lines that are 3⁄4” or smaller.
What steps should be taken when crimping a line?
1.Several feet from the leak, dig a hole to expose the leaking line away from any gas readings. Gas lines are buried around 24” below the surface but it is not uncommon to find them only several inches to several feet deep. With plastic pipe, the gas company lays a yellow-coated wire over the gas line so their detectors can find the metal; the detectors cannot pick up the plastic pipe.
2.Once this gas line is exposed, use a grounding spray or grounding device such as a wet towel over the pipe to ground and then safely clamp the line.
What things should be taken into consideration when using a dry chem or 1 3/4” line?
The wind direction, humidity, weight of the gas, and any other factors pertaining to the migration of the vapor cloud.
What should be done when a gas line is on fire?
Protect exposures; a burning gas fire is not explosive, but if the fire is extinguished without shutting off the gas an explosive condition has been created.
When should intrinsically safe equipment be turned on?
All intrinsically safe equipment should be turned on prior to entering a gaseous atmosphere.
How should you monitor a room with a closed door? Why?
Closed doors should be cracked slightly to insert the probe and a reading obtained before opening the door. Opening a door or venting an atmosphere that is above the Upper Explosive Limit (UEL) could cause an explosive atmosphere and subsequent explosion.
