Message Board Thread - "Thermography and Natural Gas .."

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Thermography and Natural Gas .. thermoimagen 3/5/2004
Some gas natural piping runs over the city in underground routes.

generally the main pipes at my city are 4" diameter and are 3 feet into ground, above the piping area is the asfalt due the most pipes runs under pavement roads.

if there are a leak, this gas should cold the leaking area?..

if this is true, then i should i need to inspect at end of day when the asfalt was heavy sun loaded?..

Re:Thermography and Natural Gas .. Gary Orlove 3/12/2004
Take a look at this....

Technology Status Report on Natural Gas Leak Detection in Pipelines
Thermal imaging detects natural gas leaks from pipelines due to the differences in
temperature between the natural gas and the immediate surroundings. This method can be used
from moving vehicles, helicopters or portable systems and is able to cover several miles or
hundreds of miles of pipeline per day. Usually, expensive thermal imagers are required to pick
up the small temperature differential between the leaking natural gas and the surroundings. In
addition, thermal imaging will not be effective if the temperature of the natural gas is not
different from that of the surroundings.

Greg Stockton reports...
"We have flown over known leaks on natural gas pipelines and not been able to measure any temperature difference on the pipe or the sounding surfaces. Usually, color IR (CIR) and not thermal IR is more effective. CIR is used to look at the damage to vegetation around the natural gas pipeline leak"

Testing needs to be performed on areas of known leakage, buried at a known depth, in different environmental conditions to provide confidence in your IR results. I would highly recommend at least one other detection method to verify IR findings.

Gary Orlove
Infrared Training Center
Re:Thermography and Natural Gas .. thermoimagen 3/13/2004
excelent paper & information.
thanks Gary ..

Re:Thermography and Natural Gas .. Jose L 4/1/2004
I am working on a mine detection project. Please send me any experiencies and results of this type of application (if any)

Thank you.
Re:Thermography and Natural Gas .. Thermoimagen 5/22/2004
i found this about leaks..(no thermography means)

Technology Status Report on Natural Gas Leak Detection in Pipelines Prepared for U.S. Department of Energy National Energy Technology Laboratory 3610 Collins Ferry Road, P. O. Box 880 Morgantown, WV 26507-0880 by Yudaya Sivathanu En’Urga Inc. 1291-A, Cumberland Avenue West Lafayette, IN 47906
Contract Number: DE-FC26-03NT41857

Attn: Daniel Driscoll, NETL
Jongmook Lim, En’Urga Inc.
Vinoo Narayanan, En’Urga Inc.

1.0 Introduction

Natural gas consumption in the US is expected to increase 50% within the next 20 years
(Anderson and Driscoll, 2000). At the same time, the gas delivery infrastructure is rapidly
aging. The Department of Energy has stated that ensuring natural gas infrastructure reliability is
one of the critical needs for the energy sector. The largest component of the natural gas
infrastructure is the approximately 400 thousand miles of delivery pipelines. Therefore, the
reliable and timely detection of failure of any part of the pipeline is critical to ensure the
reliability of the natural gas infrastructure. This report reviews the current status of the
technology for leak detection from the natural gas pipelines. The first part briefly reviews
various leak detection methods used in the natural gas pipelines. The second part reviews the
optical methods used for natural gas leak detection, and the final part reviews the potential
sensors that can be used with optical methods.

2.0 Review of Leak Detection Methods

There are a variety of methods that can detect natural gas pipe line leaks, ranging from
manual inspection using trained dogs to advanced satellite based hyperspectral imaging (Carlson,
1993; Scott and Barrufet, 2003). The various methods can be classified into non-optical and
optical methods. The primary non-optical methods include acoustic monitoring (Hough, 1988;
Klein, 1993); gas sampling (Sperl, 1991), soil monitoring (Tracer Research Corporation, 2003),
flow monitoring (Turner, 1991; Bose and Olson, 1993), and software based dynamic modeling
(Griebenow and Mears, 1988; Liou and Tain, 1994).

Acoustic monitoring techniques typically utilize acoustic emission sensors to detect leaks
based on changes in the background noise pattern. The advantages of the system include
detection of the location of the leaks as well as non-interference with the operation of the
pipelines. In addition, they are easily ported to various sizes of pipes. However, a large number
of acoustic sensors is required to monitor an extended range of pipelines. The technology is also
unable to detect small leaks that do not produce acoustic emissions at levels substantially higher
than the background noise. Attempts to detect small leaks can result in many false alarms.
Gas sampling methods typically use a flame ionization detector housed in a hand held or
vehicle mounted probe to detect methane or ethane. The primary advantage of gas sampling
methods is that they are very sensitive to very small concentrations of gases. Therefore, even
very tiny leaks can be detected using gas sampling methods. The technique is also immune to
false alarms. The disadvantages of the technology are that detection is very slow and limited to
the local area from which the gas is drawn into the probe for analysis. Therefore the cost of
monitoring long pipelines using gas sampling methods is very high.

In soil monitoring methods, the pipeline is first inoculated with a small amount of tracer
chemical. This tracer chemical will seep out of the pipe in the event of a leak. This is detected
by dragging an instrument along the surface above the pipeline. The advantages of the method
include very low false alarms, and high sensitivity. However, the method is very expensive for
monitoring since trace chemicals have to be continuously added to the natural gas. In addition, it
cannot be used for detecting leaks from pipelines that are exposed.

Flow monitoring devices measure the rate of change of pressure or the mass flow at
different sections of the pipeline. If the rate of change of pressure or the mass flow at two
locations in the pipe differs significantly, it could indicate a potential leak. The major
advantages of the system include the low cost of the system as well as non-interference with the
operation of the pipeline. The two disadvantages of the system include the inability to pinpoint
the leak location, and the high rate of false alarms.

Software based dynamic modeling monitors various flow parameters at different
locations along the pipeline. These flow parameters are then included in a model to determine
the presence of natural gas leaks in the pipeline. The major advantages of the system include its
ability to monitor continuously, and non-interference with pipeline operations. However,
dynamic modeling methods have a high rate of false alarms and are expensive for monitoring
large network of pipes.

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