Gas Leak Pinpointing - Western Regional Gas Conference

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WRGC
Pinpointing Underground
Gas Leaks
Ron Six, Instructor
Senior Utility Consultant
AEGIS Insurance Services, Inc.
201/417-2487
[email protected]
A
AE E GG II S S
ssociated
lectric
as
nsurance
ervices
AEGIS
Background Information
• Utility Mutual Insurance Company
(member owned)
• Formed in 1975 by 22 gas utilities
• Electric Utilities began joining in 1977
• 375 members – 95% utilities and related
energy
Our main job is not
finding & fixing leaks
Our main job is
public safety
Pinpointing
Is not an exact science.
It is a developed skill which
is learned and perfected
through your mistakes
and your successes.
Major Causes of Leaks
• Corrosion
• Mechanical failure
• Improper installation
• Improper design
• Faulty materials
• 3rd Party Damage - “Dig-Ins”
#682
#686
4” Plastic Main 45 PSI
ASH ST
Dead Cast Iron Gas Main
Water Main
The
“Find and Fix Syndrome”
The cure for this is to ask yourself a
question “Where is the gas”? If you can
answer the question that the gas is not
affecting people and it is not affecting
property you are cured. You must ask
yourself this question on every leak
before you get into the “repair” mode.
Our main job is not
finding & fixing leaks
Our main job is
public safety
Detect
Pinpoint
Repair
Evaluating The Leak
Where is the gas?
gas?
r
w
h
e
e
is
the
Evaluating The Leak
•
•
•
•
•
W here is the gas?
How much is there?
Extent of hazard (migration)
Relation to other structures
Evaluate/evacuate
Factors Affecting Gas Migration
• Soil type
• Soil moisture
• Surface cover
• Line pressure
• Depth of burial
• Leak size and age
• Change in elevation=slope
• Path of least resistance
• Centering = Where is the gas?
• Pinpointing = Where is the leak?
• The leak must be centered
before it is pinpointed
Centering The Leak
• Probe holes must be of sufficient depth
• Test all available openings
• “Zero out” N-S-E-W
• You must have sufficient information
to make a good judgement
Be Careful – “Don’t make a leak, looking for a leak.”
Recent Natural Gas Incidents
Springfield, MA
Methods Of Locating The Line
• Maps
• Records
• System experience
• Electronic locators
1. Basic principles of operation
2. Inductive vs. Conductive
3. Overcoming problems
Consistency = Success
• Exact location of main, services etc.
• Size of test hole (aeration is the key)
• Depth of test hole (must be consistent)
• Location of test holes (same side of main)
• Instrument use (consistency in testing)
PLACEMENT OF DRILL HOLES
• Where and how
many?
• What size test
holes?
• How deep?
• How far apart?
19
Size of the Test Hole
½” Test Hole
1” Test Hole
Size of the Test Hole
½” Test Hole
1” Test Hole
4x’s the Aeration
From the 1” Test Hole vs.
the ½” Test Hole
The Size of the test hole is critical
Pinpointing with a ½” test hole
Pinpointing using a 1” test hole
22
Minnich Hornet Drill
SAVE
ANOTHER
MISSED
EXCAVATION
#404
#402
Concrete Sidewalk
90% Gas @ Curb
4” Bare Steel
45 PSI
OLD MAIN STREET
#400
30% Gas @
Foundation Wall
Use Of Soil Purger (cont’d)
• The soil purger is your best friend
or worst enemy, depending on
where and how it is used
Types of Soil Purgers
#404
Never purge
#402
near foundation
#400
30% Gas @ Foundation Wall
Concrete Sidewalk
90% Gas @ Curb
Purge Away From
Foundation
8” CI UP
OLD MAIN STREET
This will draw the gas away from
the building and block the gas from
migrating to the foundation wall
Grade 1 Leak Repairs (Did you find “a”
leak or did you find “the” leak?)
• You must not leave a Grade 1 Leak
indication as long as the conditions that
got you there are still present. If the
readings went from 30% gas to 3% gas
at the foundation it is still a technical
Grade 1 leak. Purge the soil, get the
readings to 0%, wait and make sure that
the readings do not return.
60% Gas
Curb
8” Steel UP CWP
Maple Street
15% Gas
60% Gas
8-10’
8-10’
Curb
8” Steel UP CWP
70%
50%
75%
Maple Street
15% Gas
Service Line
60% Gas
Curb
35%
8” Steel UP CWP
0%
10%
40%
45%
50%
15%
50%
50%
45%
Maple Street
15% Gas
Slope
Service Line
0%
Using The Soil Purger In
The Pinpointing Process
• Purge from a hole where you know
that the leak is not
• Plug holes near purge point
• Dense soil or moisture –
time the purge/purge each hole
• Use it only when all other methods
have failed
Test Methods
• Combustible gas indicator
1. Top & bottom of hole
2. Time the readings
• Natural ventilation
1. Wait…let holes vent
• Blow pipe – vapors/soap top of hole
• Odor
Use Of Soil Purger
• Should not be used on every leak
• Operation:
1. In the pinpoint process
2. As a safety tool –
Never use near foundation of building
3. Residual gas
• Choosing a purge point is the key
• Techniques
CURB LINE
ASH STREET
6” Steel UP
10% Gas In Sewer Manhole
Gas Readings In Manhole
• Is gas in the sewer or
just using the manhole
as a venting point?
Manhole
CGI Test
• Test top and bottom
• Percent gas readings will
generally not be sewer gas
CGI Test
“Make Your Mark”
Using Your Experience
Using Test Results
Using System Design
Remember: It is much cheaper to drill than to dig.
Do you have enough holes to give you
enough information about the leak?
The Dry Hole
• Probe along the pipe
• Expose all of the pipe, not just the top
• Learn from your mistakes
• Use the hole to your advantage…
no one “hits” them all
• Is it our gas?
High School
4” High Pressure Steel
25% gas in sewer manhole
K-Street
6” Low Pressure Cast Iron
15% gas @ curb
65
67
69
71
Checking After The Repair
• Did we find “the” leak?
• Residual gas – when will it go away?
• Cleanup/plugging the test holes
• Importance of proper documentation
Stray Gas
• Is it lighter or heavier than air?
• Is there ethane in the sample?
• Is it a hazard?
• What is sewer gas/decomposition gas?
• Natural gas vs. stray gas
• Use of charcoal filter
• Use of collection bottles/bags
• Responsibilities regarding stray gas
• “Reasonable person concept”
Chromatographic Analysis
Comparison
No Ethane
Sewer Gas
CO2
Ethane
Natural Gas
Methane
Nitrogen
Remember:
The Job Is Not Completed
• Until all paperwork/documentation
is completed:
– Neatly
– Thoroughly
– Accurately
• You may do everything right, but you
may be judged by what is or is not
documented
Be Alert
Be Prepared
Be Safe
AEGIS Insurance Services, Inc.
Thank You
Please visit our website @
www.aegislink.com
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