Flashcards in OG 6.8 Natural Gas Emergencies Deck (54):
1
During a natural gas emergency, restrict vehicle and pedestrian traffic to outside a ____' radius.
300 foot
2
When checking a structure with a gas monitor, what two areas are the most important areas to check?
Basements
Upper areas
3
You should withdraw from a structure when a gas level reaches what percentage?
20% or greater
4
Natural gas has a lower explosive limit of what percentage?
5%
5
Natural gas has a flammable range of what percentage?
5 to 15%
6
What items should you never bring into the natural gas hot zone?
Cell phones
7
What is the vapor density of natural gas?
0.6
8
What are the three types of gaspipe found in Portland?
1. Steel
2. Buried polyethylene
3. Poly pipe inserted in a casing
9
Steelpipe is used for all gas pipelines of what type?
Transmission – pressure pipelines
10
How much pressure is the steelpipe able to maintain?
50 - 800 PSI
11
What is the standard pressure for steelpipe?
Less than 50 psi
12
What type of gas pipe is able to ground itself to the soil?
Steelpipe
13
What is the danger of buried polyethylene pipe or poly pipe in a casing, when it is damaged?
A static charge can build up causing ignition
14
What is the danger of Poly pipe to adjacent structures?
Little to no risk, usually localized
15
What is the most commonly used type of gaspipe found in Portland on new construction?
Poly pipe
16
What does Northwest natural use to upgrade existing gas service?
Poly pipe inserted into a casing
17
What are two situations when Northwest natural always uses steelpipe?
Transmission line
Soil conditions require it
18
What is the easiest way to identify poly pipe in a casing?
1. A white plastic sleeve over the steelpipe where the pipe enters the soil at the meter
2. A large metal ring placed around the pipe just below the shutoff valve
19
Is a static charge is deemed to be an issue, What might crews do to remedy the situation?
Dig down to the pipe greater than 10 feet away and soak pipe with water.
20
What is the primary danger when dealing with encased Poly pipe?
Natural gas can travel back to the casing to the main.
21
Where should you never direct the hose stream on natural gas emergencies?
Into the hole
22
If there is a serious natural gas leak escaping outside of the structure with no fire, and there is danger to personnel, where can you shut off the gas?
The valve located at the curb just on the customer side of the property line
23
You should never operate any gas valve that is located where?
In the street
24
A gas valve that is by the curb can be usually found at what three types of facilities?
1. Commercial
2. Institutional
3. Industrial
25
Is it okay to operate valves located on large complex gas meters at commercial locations?
Only if there is imminent life or property threat.
26
When approaching a residence on the natural gas emergency what should you never use at the front door?
The doorbell. Knock and enter
27
Is it okay to turn off the main circuit breaker to a building at a natural gas emergency?
no, this may cause a spark.
28
When ventilating at a natural gas emergency, what type of fans should you use?
Electric fans with explosion proof switches
29
When ventilating A structure at a natural gas emergency, Where should you start ventilating?
First, where the greatest concentration is, then from the top down
30
If ventilation cannot be done safely inside a structure, where should you ventilate?
From the outside until it is safe to go inside.
31
If it is necessary to extinguish a natural gas fire at a structure due to life safety issues, What should you used to extinguish the fire?
Dry chemical extinguisher
32
If a natural gas fire is burning inside a structure, is it okay to put out the fire?
It is okay to put out the structure fire, Not the gas fire.
33
When did Northwest natural begin placing excess flow devices on new construction?
January, 1999
34
Where are excess flow devices located on single-family dwellings?
Approximately 18 inches from the distribution line towards the house
35
An excess flow device will decrease gas flow by what percentage?
95%
36
Why does the excess flow device allow 5% leakage?
So that natural gas can be detected.
37
What can you look at to determine if there is an excess flow device on a single-family dwelling controlling natural gas?
Locate the metal washer on the riser, A hole shaped as a diamond will be stamped through this washer.
38
On natural gas vehicles, CNG is stored in high-pressure tanks at ____ psi.
3000
39
How quickly will a CNG fuel tank empty when there is a leak?
A few minutes
40
In the Portland metropolitan area, CNG is primarily used in _____ vehicles.
Fleet
41
Fleet vehicles powered with CNG can be identified by what marking?
Blue diamond shaped sticker with the silver border, with silver letters "CNG"
42
Will Northwest natural respond to CNG fires?
no
43
How do you extinguish a CNG fire?
CNG fires should not be extinguished unless jeopardizing life or property.
44
Where would you find a CNG tank on fleet vehicles?
In the trunk
45
LNG is an orderless cryogen stored at approximately____F with a vapor pressure of approximately ___ psi, and an expense ratio of approximately ____ to ____.
-260°F
15
620:1
46
LNG is a liquid that will flow, how should you contain it?
Diking
47
Where do LNG vapors usually travel?
They heat up and stay close to the ground.
48
When working with LNG, what ignition sources should you eliminate?
Low-level ignition sources
49
In the Portland Metro area, where is LNG normally used?
Tri-Met buses.
50
What markings Will identify a vehicle using LNG?
Blue diamond shaped sticker with a silver border, Silver letters LNG in the middle of the sticker.
51
Will Northwest natural respond to LNG emergencies?
Yes
52
why is it a bad idea to direct water at LNG?
This will cause LNG vaporize at an accelerated rate.
53
If necessary to extinguish a LNG fire, What should you use to extinguish the fire?
Dry chemical extinguisher
54