U.S. patent application number 15/154509 was filed with the patent office on 2017-11-16 for distributed gas detection system and method.
The applicant listed for this patent is General Electric Company. Invention is credited to William Albert Challener, Niloy Choudhury, Jason Harris Karp, Ansas Matthias Kasten, Sabarni Palit.
Application Number | 20170328832 15/154509 |
Document ID | / |
Family ID | 58461509 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170328832 |
Kind Code |
A1 |
Challener; William Albert ;
et al. |
November 16, 2017 |
DISTRIBUTED GAS DETECTION SYSTEM AND METHOD
Abstract
A distributed gas detection system includes one or more hollow
core fibers disposed in different locations, one or more solid core
fibers optically coupled with the one or more hollow core fibers
and configured to receive light of one or more wavelengths from a
light source, and an interrogator device configured to receive at
least some of the light propagating through the one or more solid
core fibers and the one or more hollow core fibers. The
interrogator device is configured to identify a location of a
presence of a gas-of-interest by examining absorption of at least
one of the wavelengths of the light at least one of the hollow core
fibers.
Inventors: |
Challener; William Albert;
(Glenville, NY) ; Palit; Sabarni; (Niskayuna,
NY) ; Karp; Jason Harris; (Niskayuna, NY) ;
Kasten; Ansas Matthias; (Niskayuna, NY) ; Choudhury;
Niloy; (Glenville, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Family ID: |
58461509 |
Appl. No.: |
15/154509 |
Filed: |
May 13, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 2201/0826 20130101;
G02B 6/02 20130101; G01N 21/255 20130101; G01M 3/38 20130101; G02B
6/02304 20130101; G01N 21/3103 20130101 |
International
Class: |
G01N 21/31 20060101
G01N021/31; G01N 21/25 20060101 G01N021/25; G02B 6/02 20060101
G02B006/02; G02B 6/02 20060101 G02B006/02 |
Goverment Interests
GOVERNMENT LICENSE RIGHTS
[0001] This invention was made with Government support under
contract number DE-AR0000543 awarded by the Department Of Energy.
The Government has certain rights in this invention.
Claims
1. A system comprising: one or more hollow core fibers disposed in
different locations; one or more solid core fibers optically
coupled with the one or more hollow core fibers and configured to
receive light of one or more wavelengths from a light source; and
an interrogator device configured to receive at least some of the
light propagating through the one or more solid core fibers and the
one or more hollow core fibers, the interrogator device configured
to identify a location of a presence of a gas-of-interest by
examining absorption of at least one of the wavelengths of the
light in at least one of the hollow core fibers; wherein the one or
more hollow core fibers are disposed at different distances along a
length of an elongated sensing tube.
2. The system of claim 1, wherein the system includes plural hollow
core fibers and plural solid core fibers, with each of the hollow
core fibers connected to a single and different solid core
fiber.
3. The system of claim 1, wherein the one or more hollow core
fibers and the one or more solid core fibers are disposed at least
partially within the elongated sensing tube having openings through
which the gas-of-interest may enter into the sensing tube from a
source of the gas-of-interest.
4. (canceled)
5. The system of claim 3, wherein the sensing tube includes an
interior surface having one or more reduced throats with a smaller
cross-sectional area at a first end of one or more of the hollow
core fibers than a cross-sectional area of the interior surface at
an opposite, second end of the one or more hollow core fibers.
6. The system of claim 3, wherein one or more of the hollow core
fibers are coupled with a baffle outwardly extending from the
hollow core fiber, the baffle located closer to a first end of the
hollow core fiber than an opposite, second end of the hollow core
fiber, wherein the baffle reduces a cross-sectional area of the
sensing tube at the first end of the hollow core fiber relative to
the second end of the hollow core fiber.
7. The system of claim 3, wherein the sensing tube includes a
larger segment fluidly coupled with a smaller segment, the larger
segment having a larger cross-sectional area than the smaller
segment, wherein a first end of one or more of the hollow core
fibers is disposed in the larger segment of the sensing tube and an
opposite, second end of the one or more hollow core fibers is
disposed in the smaller segment of the sensing tube.
8. The system of claim 1, wherein the one or more solid core fibers
are disposed outside of an elongated sensing tube having openings
through which the gas-of-interest may enter into the sensing tube
from a source of the gas-of-interest, and wherein the one or more
hollow core fibers include first ends extending into an interior
space of the sensing tube and opposite, second ends optically
coupled with the solid core fibers outside of the sensing tube.
9. The system of claim 8, wherein a second solid core fiber is
attached to the end of at least one of the hollow core fibers which
extends into an interior space of the sensing tube.
10. The system of claim 1, wherein the one or more solid core
fibers are disposed outside of an elongated sensing tube having
openings through which the gas-of-interest may enter into the
sensing tube from a source of the gas-of-interest, and wherein the
one or more hollow core fibers include first ends extending into an
interior space of the sensing tube and optically coupled with the
solid core fibers outside of the sensing tube, and second ends that
are outside of the elongated sensing tube.
11. The system of claim 10, wherein a second solid core fiber is
attached to the end of the hollow core fiber located outside of the
sensing tube.
12. The system of claim 1, wherein the one or more hollow core
fibers are configured to be disposed at the different locations in
one or more of an underground mine, a mining platform, or a sensing
tube extending along a pipeline.
13. A system comprising: one or more hollow core fibers disposed in
different locations; one or more solid core fibers optically
coupled with the one or more hollow core fibers and configured to
receive light of one or more wavelengths from a light source; an
elongated sensing tube having openings through which a
gas-of-interest may enter into the sensing tube from a source of
the gas-of-interest, wherein the one or more hollow core fibers are
at least partially disposed inside the sensing tube; and an
interrogator device configured to receive at least some of the
light propagating through one or more of the solid core fibers and
one or more of the hollow core fibers, the interrogator device
configured to identify a location of a presence of the
gas-of-interest from the source by examining absorption of at least
one of the wavelengths of the light at one or more of the hollow
core fibers; wherein the one or more hollow core fibers and the one
or more solid core fibers are disposed within the sensing tube.
14. (canceled)
15. The system of claim 13, wherein the one or more hollow core
fibers are disposed at different distances along a length of the
sensing tube.
16. The system of claim 13, wherein the sensing tube includes an
interior surface having one or more reduced throats with a smaller
cross-sectional area at a first end of one or more of the hollow
core fibers than a cross-sectional area of the interior surface at
an opposite, second end of the one or more hollow core fibers.
17. The system of claim 13, wherein one or more of the hollow core
fibers are coupled with a baffle outwardly extending from the
hollow core fiber, the baffle located closer to a first end of the
hollow core fiber than an opposite, second end of the hollow core
fiber, wherein the baffle reduces a cross-sectional area of the
sensing tube at the first end of the hollow core fiber relative to
the second end of the hollow core fiber.
18. The system of claim 13, wherein the sensing tube includes a
larger segment fluidly coupled with a smaller segment, the larger
segment having a larger cross-sectional area than the smaller
segment, wherein a first end of one or more of the hollow core
fibers is disposed in the larger segment of the sensing tube and an
opposite, second end of the one or more hollow core fibers is
disposed in the smaller segment of the sensing tube.
19. The system of claim 13, wherein the one or more solid core
fibers are disposed outside of an elongated sensing tube having
openings through which the gas-of-interest may enter into the
sensing tube from a source of the gas-of-interest, and wherein the
one or more hollow core fibers include first ends extending into an
interior space of the sensing tube and opposite, second ends
optically coupled with the one or more solid core fibers outside of
the sensing tube.
20. The system of claim 13, wherein the one or more solid core
fibers are disposed outside of an elongated sensing tube having
openings through which the gas-of-interest may enter into the
sensing tube from a source of the gas-of-interest, and wherein the
one or more hollow core fibers include first ends extending into an
interior space of the sensing tube which are optically coupled with
the one or more solid core fibers outside of the sensing tube and
opposite, second ends optically coupled with the one or more solid
core fibers outside of the sensing tube.
21. A method comprising: receiving light that has propagated
through one or more solid core fibers and one or more hollow core
fibers of several hollow core fibers disposed in different
locations; determining whether one or more wavelengths of the light
have been at least partially absorbed by a gas-of-interest inside
one or more of the hollow core fibers based on the light that is
received; determining a location of a source of the gas-of-interest
based on a location of the one or more hollow core fibers in which
the one or more wavelengths of the light was at least partially
absorbed by the gas-of-interest; and drawing the gas-of-interest
into the one or more hollow core fibers by generating a pressure
differential of the gas-of-interest between opposite ends of the
one or more hollow core fibers.
22. (canceled)
23. The method of claim 21, further comprising stopping a flow of
the gas-of-interest in a pipeline responsive to determining the
location of the source of the gas-of-interest.
Description
BACKGROUND
[0002] Various devices have been developed for sensing and
measuring the concentrations of different gases at man-made or
natural locations, such as oil wells, pipelines, mines,
manufacturing plants, refineries, and the like. Monitoring for the
presence and concentration of gases may be used for various
applications, such as to ensure that toxic gases (CO, H.sub.2S,
etc.) are not present in significant concentrations, to ensure that
explosive gases (CH.sub.4, H.sub.2, etc.) are below respective
explosive limits, to identify the gases in a mixture (for custody
transfer, heat content, etc.), or for various other reasons.
Spectroscopy may be used to provide highly sensitive and selective
sensors because each gas exhibits a unique spectroscopic
fingerprint, such that gases absorb and emit light energy at
specific wavelengths. Gases are relatively transparent, however, so
the absorption line strength of a gas may be relatively small and
hard to detect.
[0003] To accommodate for the small absorption line strength, light
used in spectroscopy is required to pass through long path lengths
in the gas in order to establish sufficient sensitivity for a
spectroscopic sensor to provide a measurement of a concentration of
a gas of interest in a test sample, for example. For example, a
light source of the spectroscopic sensor may be separated from a
detector of the spectroscopic sensor by a distance of one kilometer
or more to achieve a necessary path length, but such distances are
not practical in most applications.
[0004] Other known types of spectroscopic sensors define an optical
cavity with two mirrors and are referred to as optical cavity
sensors. The gas is contained within the optical cavity, and the
light is reflected between the two mirrors multiple times before
being detected. While this technique allows for a manageable device
size, it is problematic due to the need to maintain very exacting
alignment of the mirrors. Variations in conditions, such as
temperature changes, vibration, humidity, or the like, may misalign
the mirrors or otherwise interfere with the sensitivity and/or
accuracy of these optical cavity sensors. Therefore, this technique
is generally not used for remote, unattended measurements in
various field environments, such as an oil or gas well pad, a
pipeline, a mine, or the like. Moreover, optical cavity sensors are
generally quite expensive.
[0005] Some gas leak detection systems use a sensing pipe or tube
located near a pipeline through which the gas is conveyed. This
sensing pipe or tube may have openings to allow gas leaking from
the pipeline to diffuse into the sensing pipe or tube. A burst of
air or another gas may be introduced into the sensing pipe or tube
to move the gas leaking from the pipeline through the sensing pipe
or tube. The sensing pipe or tube may include a gas sensor at one
end to sense the leaking gas that is pushed through the sensing
pipe or tube by the air burst toward the sensor.
[0006] These types of leak detection systems may be unable to
accurately determine the location of the leak along the length of a
very long pipeline. The location of the leak is approximated based
on the concentration of the gas detected at the sensor and the time
delay between when the air burst is introduced into the sensing
pipe or tube. Because the gas may disperse along the length of the
sensing pipe or tube by the air burst, it can be difficult or
impossible to accurately determine where the gas first diffused
into the sensing pipe or tube if the gas must travel through the
tube for a very long distance before reaching the sensor at the end
of the tube.
BRIEF DESCRIPTION
[0007] In one embodiment, a distributed gas detection system
includes one or more hollow core fibers disposed in different
locations, one or more solid core fibers optically coupled with the
one or more hollow core fibers and configured to receive light of
one or more wavelengths from a light source, and an interrogator
device configured to receive at least some of the light propagating
through the one or more solid core fibers and the one or more
hollow core fibers. The interrogator device is configured to
identify a location of a presence of a gas-of-interest by examining
absorption of at least one of the wavelengths of the light at least
one of the hollow core fibers.
[0008] In one embodiment, a distributed gas sensing system includes
one or more hollow core fibers disposed in different locations, one
or more solid core fibers optically coupled with the one or more
hollow core fibers and configured to receive light of one or more
wavelengths from a light source, and an elongated sensing tube
having openings through which a gas-of-interest may enter into the
sensing tube from a source of the gas-of-interest. The one or more
hollow core fibers are at least partially disposed inside the
sensing tube. The system also includes an interrogator device
configured to receive at least some of the light propagating
through one or more of the solid core fibers and one or more of the
hollow core fibers. The interrogator device is configured to
identify a location of a presence of the gas-of-interest from the
source by examining absorption of at least one of the wavelengths
of the light at one or more of the hollow core fibers.
[0009] In one embodiment, a method includes receiving light that
has propagated through one or more solid core fibers and one or
more hollow core fibers of several hollow core fibers disposed in
different locations, determining whether one or more wavelengths of
the light have been at least partially absorbed by a
gas-of-interest inside one or more of the hollow core fibers based
on the light that is received, and determining a location of a
source of the gas-of-interest based on a location of the one or
more hollow core fibers in which the one or more wavelengths of the
light was at least partially absorbed by the gas-of-interest.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates an embodiment of a distributed gas leak
detection system.
[0011] FIG. 2 illustrates another embodiment of a distributed gas
leak detection system.
[0012] FIG. 3 illustrates a cross-sectional view of a segment of a
sensing tube and a hollow core fiber that may be disposed inside
the sensing tube according to one embodiment.
[0013] FIG. 4 illustrates a cross-sectional view of a segment of a
sensing tube and a hollow core fiber that may be disposed inside
the sensing tube according to one embodiment.
[0014] FIG. 5 illustrates a cross-sectional view of a segment of a
sensing tube according to one embodiment.
[0015] FIG. 6 illustrates a gas leak detection system according to
another embodiment.
[0016] FIG. 7 illustrates a flowchart of one embodiment of a method
for detecting presence of a gas-of-interest in a test location.
DETAILED DESCRIPTION
[0017] Various embodiments will be better understood when read in
conjunction with the appended drawings. To the extent that the
figures illustrate diagrams of the functional blocks of various
embodiments, the functional blocks are not necessarily indicative
of the division between hardware (including circuitry). Thus, for
example, one or more of the functional blocks (e.g., processors,
controllers or memories) may be implemented in a single piece of
hardware (e.g., a general purpose signal processor or random access
memory, hard disk, or the like) or multiple pieces of hardware.
Similarly, any programs may be stand-alone programs, may be
incorporated as subroutines in an operating system, may be
functions in an installed software package, and the like. It should
be understood that the various embodiments are not limited to the
arrangements and instrumentality shown in the drawings. The sizes
of the components shown in the drawings may not be to scale and/or
may have different aspect ratios.
[0018] As used herein, the terms "system," "unit," or "device" may
include a hardware and/or software system that operates to perform
one or more functions. For example, a device, unit, or system may
include one or more computer processors, microprocessors, field
programmable gate arrays, integrated circuits, controllers, or
other logic-based devices that perform operations based on
instructions stored on a tangible and non-transitory computer
readable storage medium, such as a computer memory. Alternatively,
a device, unit, or system may include a hard-wired device that
performs operations based on hard-wired logic of the device. The
device or units shown in the attached figures may represent the
hardware that operates based on software or hardwired instructions,
the software that directs hardware to perform the operations, or a
combination thereof. The hardware may include electronic circuits
that include and/or are connected to one or more logic-based
devices, such as microprocessors, processors, controllers, or the
like. These devices may be off-the-shelf devices that are
appropriately programmed or instructed to perform operations
described herein from the instructions described above.
Additionally or alternatively, one or more of these devices may be
hard-wired with logic circuits to perform these operations.
[0019] As used herein, an element or step recited in the singular
and proceeded with the word "a" or "an" should be understood as not
excluding plural of said elements or steps, unless such exclusion
is explicitly stated. Furthermore, references to "one embodiment"
are not intended to be interpreted as excluding the existence of
additional embodiments that also incorporate the recited features.
Moreover, unless explicitly stated to the contrary, embodiments
"comprising" or "having" an element or a plurality of elements
having a particular property may include additional such elements
not having that property.
[0020] One or more embodiments of the inventive subject matter
described herein provide distributed gas leak detection systems and
methods. The systems and methods can detect the presence of a gas
leaking out of a pipeline and a location of the leak. For example,
methane can leak from oil and gas well pads or from pipelines.
Methane also is a troublesome source of explosions in underground
coal mines. Due to the large areas over which the gas may be
present, multiple sensing locations may be needed to determine a
location of the source of the leak.
[0021] The systems and methods described herein may use hollow core
optical fibers (HCF) for transporting infrared light (or other
wavelengths of light) along relatively long path lengths to
sensitively detect methane and other types of gas leaks. The HCF is
penetrated with holes from the side at different locations along
the length of the HCF so that leaking gases in the external
environment can diffuse into the hollow core of the HCF where the
light beam is propagating. Optical absorption measurements such as
tunable diode laser absorption spectroscopy (TDLAS) can be used to
make highly sensitive measurements of the gas concentration and
also to distinguish between different types of gases which exhibit
different absorption wavelengths based on the light that is
received through the HCF.
[0022] The systems and methods described herein may be used to
detect and measure concentrations of gases of interest in various
applications. For example, the gas sensing system may be used to
monitor gases at oil wells or well pads, along pipelines, in mines,
in manufacturing plants, at refineries, in factories, and the like.
One particular application is measurement of fugitive methane
emissions from oil and gas well pads. Methane is a strong
contributor to the greenhouse effect, which traps infrared
radiation within the earth's ozone layer. The low cost, but highly
sensitive (.about.10 parts per million, or ppm) gas sensing systems
described herein may be disposed at oil and gas well pads to
monitor methane emissions. The monitoring of methane emissions may
be in order to comply with regulations designed to reduce
greenhouse gas emissions, to reduce loss of methane that could be
sold as product, or the like. Although the gas sensing system is
located in the field at the oil and gas well pad, the gas sensing
system may be monitored remotely, allowing for remote monitoring of
multiple gas sensing systems at different oil and gas well pads,
for example.
[0023] Spectroscopy can be used for gas sensing by detecting the
wavelengths that gas samples absorb and emit light energy. These
wavelengths, referred to as absorption spectra, are specific or
unique to the types of gases. For example, methane has several
absorption bands at different wavelengths, such as an absorption
band at 1.65 microns in the near infrared (NIR) range. This
absorption band lies within the "window" of wavelengths used by the
telecom industry to transport data through conventional solid core
optical fiber, which extends from 1260 nm ("O" band) up to 1675 nm
("U/XL" band). Other gases with absorption lines in this wavelength
range include water, CO.sub.2, H.sub.2S, and ammonia.
[0024] Microstructured (or "holey") optical fibers have fiber
structures that are porous and make use of this porosity in several
different ways to confine light to the core of the fiber so that it
can propagate for long distances along the fiber. These types of
fibers may be used as the HCF described herein. U.S. patent
application Ser. No. 14/876,411 describes various hollow core
microstructured fibers that may be used as the HCF described
herein, and the entire disclosure of this application is
incorporated herein by reference.
[0025] FIG. 1 illustrates one embodiment of a distributed gas leak
detection system 200. The system 200 detects the presence,
concentration, and/or location of one or more gases of interest
along a remote test location 104. In the illustrated embodiment,
the remote test location 104 is a pipeline carrying the one or more
gases of interest, but optionally, the remote test location 104 may
be an underground mine, a landfill, a water treatment plant, a
platform of an oil or gas well, etc. The system 200 monitors for
the gases of interest along a length of the test location 104. The
test location 104 may be subject to environmental conditions that
may be damaging to certain electronic equipment, such as
thermocouples, LEDs or photodiodes, or may contain explosive
mixtures of gases or other substances for which it is not possible
to proximately locate electrical equipment. For example, the test
location 104 may be a geothermal well, oil and/or gas well, oil
and/or gas well pad, oil and/or gas pipeline, a mine, or the like.
The test location 104 in other examples may be an industrial
facility, such as a manufacturing plant, a refinery, or a factory.
As one more example, the test location 104 may be a wellbore used
in conjunction with hydraulic fracturing.
[0026] The test location 104 may be understood as being remote in
that the test location 104 is located at a distance from components
of the system 200 configured to generate and/or receive signals
conveyed through the test location 104. For example, parts of a
pipeline 102 that is included in or represents the test location
104 may be 100 kilometers away from components of the system 200.
Thus, signal generation and/or signal processing equipment, for
example, may be maintained under different environmental conditions
than the components of the system 200 along the remote test
location 104. Alternatively, signal generation and/or signal
processing components of the system 200 may be located at the
remote test location 104, and may be housed within protective cases
or housings to protect such components from the environmental
conditions of the test location 104, such as hot and cold
temperatures, moisture, debris, vibration, explosive gas mixtures,
and the like.
[0027] The system 200 includes an optical fiber assembly 206 that
extends along various lengths or the entire length of the test
location 104. The optical fiber assembly 206 may be formed from
plural HCFs 108 optically coupled with solid core optical fibers
210. In contrast to the HCFs 108, the solid core optical fibers 210
may be optical fibers that do not have a hollow interior. The HCFs
108 and solid core fibers 210 may be optically coupled with each
other when light can be transmitted along and within the HCFs 108
and solid core fibers 210.
[0028] In the illustrated embodiment, the optical fiber assembly
206 extends through a perforated sensing tube 120 that extends
along the test location 104. The sensing tube 120 may be a plastic
tube or a volume of space in which the fiber assembly 206 is
disposed (e.g., between a plastic sheet and the pipeline 102). The
sensing tube 120 includes openings 122 through which gas in the
test location 104 (e.g., leaking from the pipeline 102) can diffuse
into the interior space of the tube 120 and into the HCFs 108.
Although only a few openings 122 are shown, many more openings 122
may exist at different locations along the length of the sensing
tube 120. The sensing tube may also be covered with a membrane that
is permeable to the gases of interest but which resists or impedes
in the ingress of water or other liquids and/or gases that are not
of interest or which could clog the tube.
[0029] The fiber assembly 206 includes several different solid core
fibers 210 separately coupled with different HCFs 108. Each HCF 108
may be connected with and disposed between solid core fibers 210 on
opposite sides of the HCF 108. The HCFs 108 may be disposed at
different locations along the length of the sensing tube 120 to
provide for distributed sensing of gas leaks. For example, the
lengths of the solid core fibers 210 extending from the light
source 114 to the HCFs 108 may be different for different HCFs 108,
as shown in FIG. 1. Alternatively, the fiber assembly 206 may
include a string of a series of solid core fibers 210 separated
from each other by HCFs 108.
[0030] The system 200 includes an interrogator device 212 that
detects the presence and/or location of one or more gases of
interest along the length of the fiber assembly 206. The
interrogator device 212 includes a light source 114 that is
optically coupled with the fiber assembly 206. As used herein, two
components are "optically coupled" when there is a sufficient
amount of light being emitted from one of the components to be
detected at the other component. The light source 114 generates
light that is transmitted to the fiber assembly 206. The light
source 114 may be a laser that emits light in the infrared range,
such as the near-IR range. The light generated by the light source
114 enters into and propagates through the solid core fibers 210 to
the HCFs 108. The hollow cores of the HCFs 108 receive the light
from the solid core fibers 110.
[0031] The HCFs 108 may include port holes that extend from an
exterior surface of the HCFs 108 into the hollow cores of the HCFs
108. The port holes are sized to allow for gas in the external
environment (e.g., which may be leaking from the pipeline 102 or
another source) to diffuse into the hollow core, where the gas can
interact with the light propagating through the core. As used
herein, "interaction" of a gas with the light involves the
absorption and emission of light energy by the gas at various
wavelengths, which affects and/or alters the characteristics of the
light energy propagating through the hollow core of the fiber.
[0032] In the illustrated embodiment, the light source 114 emits
the light into one or more solid core fibers to a multiplexer 228
("10:1 MUX" in FIG. 1), which divides the light and conveys the
divided light into the solid core fibers 210 that are optically
coupled with different HCFs 108. The multiplexer 228 may convey the
light received from the light source 114 into different solid core
fibers 210 at different times. The light propagating through the
core of the HCFs 108 continues to propagate through the solid core
fibers 210 on the other sides of the HCFs 108 to a beam combiner
230. The beam combiner 230 receives the light from the different
solid core fibers 210 before conveying the received light to the
detector 116.
[0033] A detector 116 measures the received light. The detector 116
may be an optical sensor, an optical camera, or the like,
configured for use in infrared gas-phase spectroscopy. One or more
processors 118 of the interrogator device 212 represent hardware
circuitry that includes and/or is connected with one or more
microprocessors, field programmable gate arrays, or integrated
circuits. The processors 118 determine a presence, concentration,
and/or location of one or more gases in the HCFs 108 based on the
light received by the detector 116. For example, the processors 118
can analyze the reflected light to identify various gases of
interest within the HCFs 108 that interacted with the light to
detect the presence of such gases. The processors 118 may analyze
the light using gas-phase IR spectroscopy. For example, the
processors 118 may compare the detected wavelengths of absorption
bands in a test sample to known absorption band wavelengths of
known gases in order to identify one or more gases in the test
sample. In addition to identifying the gases, the processors 118
may also determine the concentrations of the gases. The processors
118 may determine that the gas in the HCFs 108 includes water
vapor, carbon dioxide, methane, and ethane, for example, and may
also detect the concentrations and/or relative concentrations of
these identified gases.
[0034] The processors 118 may be configured to generate a control
signal in response to detecting a leak, such as to send an alert.
The processors 118 may also generate other control signals
responsive to detecting one or more gases of interest, such as for
automatically scheduling additional inspection, to initiate a
shutdown of the well, to activate a system that stops gas leaking
or egress, or the like. For example, the interrogator device 212
may include a communication device 126 that communicates a signal
to another location, such as a signal that notifies others of a
detected leak and/or the location of the leak, a signal that causes
one or more valves to close and stop the gas conveyed through the
pipeline 102 from being pumped through the pipeline 102, etc. The
communication device 126 can represent one or more antennas,
modems, and/or associated transceiving circuitry.
[0035] In one embodiment, the solid core fibers 210 and HCFs 108
convey the light generated by the light source 114 in a variety of
modes, and are not limited to propagating the light along the
fibers 210 and HCFs 108 in only one mode. Light may propagate
through optical fibers such as the solid core fibers 210 in a
vertical polarization mode, a horizontal polarization mode, and/or
a combination or mixture of vertical and horizontal polarizations
of the light. The fibers 210 and HCF 108 may not be limited to
propagating or conveying only a single mode of light. For example,
the light propagating through the solid core fibers 210 and the
HCFs 108 may propagate through the solid core fibers 210 to the
HCFs 108 (and optionally through one or more the HCFs 108 before
reaching one or more other HCFs 108) in a vertical polarization,
horizontal polarization, and/or a mixture of vertical and
horizontal polarizations. The light may continue or be reflected
back to the detector 116 in the same or different polarization. For
example, the fibers 108, 210 may not restrict propagation of light
either to or from an HCF 108 to a single polarization or mode.
[0036] In one embodiment, the system 200 includes a control gas
source 124 (e.g., "pump" in FIG. 1) that provides a burst of gas or
air into the sensing tube 120. The gas or air provided by the
source 124 may be different from the gas of interest being detected
by the system 200 to prevent confusion between detection of a leak
versus the gas or air provided by the source 124. The source 124
may be a pump or fan that pushes ambient air through the sensing
pipe 120. The source 124 may push air or another gas through the
sensing pipe 120 on a periodic, irregular, or on-demand basis to
move gas leaking in the test location 104 through the sensing pipe
120. The leaking gas will have a greater local concentration in the
sensing pipe 120 when compared to other locations. The localized
concentration of the leaking gas can be moved through the sensing
pipe 120 by the pushed air or gas from the source 124. As the
leaking gas moves through the sensing pipe 120, the interrogator
device 212 can emit light and measure reflected light to identify
locations in which the leaking gas concentration is located, as
well as track movement in the sensing tube 120, to assist in
identifying where the leak is located along or in the test location
104.
[0037] As described above, the remote test location 104 may
represent an area or volume around or along a pipeline carrying the
one or more gases of interest, but optionally may be around, along,
or within an underground mine, a platform of an oil or gas well,
etc. The systems described herein may include the HCFs 108 in
different locations within an area sought to be monitored for the
presence of one or more gases of interest, such as but not limited
to methane. The HCFs 108 may be positioned at different locations
along the length of a pipeline, in different locations of an
underground mine, in different locations on a mining platform, or
the like, to detect the presence of a gas. While the descriptions
and illustrations shown herein relate to HCFs 108 disposed along
the length of a pipeline, not all embodiments of the inventive
subject matter are limited to pipelines.
[0038] In contrast to using a single HCF 108 to detect the presence
and/or location of a gas leak along the test location 104, the
system 200 may include several HCFs 108 in different locations
along the test location 104 to detect the presence and/or location
of the gas leak. The HCFs 108 may be spaced apart from each other
by relatively large distances, such as ten kilometers or another
distance, to provide for leak detection along the test location 104
that extends over a very large area or distance. The solid core
fibers 210 may allow for propagation of light through the fibers
210 over larger distances than the HCFs 108. As a result, the solid
core fibers 210 may be spliced with the HCFs 108 to allow for the
HCFs 108 to be spaced far apart from the light source 114 and/or
the detector 116.
[0039] Additionally, the solid core fiber or fibers 210 that
connect the fiber assembly 206 with the interrogator device 212 can
allow for the interrogator device 212 to be located relatively far
from the test location 104. The interrogator device 212 may be
placed far from the test location 104 such that the risk for
explosion from leaking gas in the location of the interrogator
device 212 may be very low or nonexistent. This can permit the
interrogator device 212 to operate without having reduced power
restrictions and/or without being located within explosion-proof
packaging relative to interrogator devices that are close to the
test location 104.
[0040] FIG. 2 illustrates another embodiment of a distributed gas
leak detection system 300. Similar to the system 200 shown in FIG.
1, the system 300 detects the presence, concentration, and/or
location of one or more gases of interest along the test location
104. The system 300 includes an optical fiber assembly 306 that
extends along various lengths or the entire length of the test
location 104. The optical fiber assembly 306 may be formed from
plural HCFs 108 optically coupled with solid core optical fibers
310. In contrast to the HCFs 108, the solid core optical fibers 310
may be optical fibers that do not have a hollow interior. The HCFs
108 and solid core fibers 310 may be optically coupled with each
other when light can be transmitted along and within the HCFs 108
and solid core fibers 310. The fiber assembly 306 may be at least
partially disposed within the sensing tube 120. Although the
openings 122 (shown in FIG. 1) in the sensing tube 120 are not
visible in FIG. 2, the sensing tube 120 may include the openings
122 to permit gas outside of the sensing tube 120 to reach the HCFs
108. The sensing tube may also be covered with a membrane that is
permeable to the gases of interest but which resists or impedes in
the ingress of water or other liquids and/or gases that are not of
interest or which could clog the tube.
[0041] In contrast to the fiber assembly 206 shown in FIG. 1, the
fiber assembly 306 includes several different solid core fibers 310
separately coupled with different HCFs 108. Each HCF 108 may be
connected with one solid core fiber 310 on one side of the HCF 108.
The solid core fibers 310 have different lengths such that the HCFs
108 are disposed at different locations along the length of the
sensing tube 120 to provide for distributed sensing of gas leaks.
The HCFs 108 can include reflectors inside, at, or near the ends of
the HCFs 108 that are opposite the ends that connect with the solid
core fibers 310 to reflect light.
[0042] The system 300 includes an interrogator device 312 that
detects the presence and/or location of one or more gases of
interest along the length of the fiber assembly 306. The
interrogator device 312 includes the light source 114 that is
optically coupled with the fiber assembly 306 on one end of the
fiber assembly 306. The light source 114 generates light that is
transmitted to the fiber assembly 306. In the illustrated
embodiment, the light source 114 emits the light into one or more
solid core fibers to the multiplexer 228 ("MUX" in FIG. 2), which
divides the light and conveys the divided light into the solid core
fibers 310 that are optically coupled with different HCFs 108. The
light propagating through the core of the HCFs 108 is reflected
back to the detector 116 of the interrogator device 312.
[0043] The multiplexer 230 receives the reflected light from the
different solid core fibers 310 before conveying the received light
to the detector 116. As described above, the detector 116 receives
the light and the processors 118 examine the light to determine the
presence and/or location of a gas leak along or within the test
location 104.
[0044] FIG. 3 illustrates a cross-sectional view of a segment of a
sensing tube 420 and one of the HCFs 108 that may be disposed
inside the sensing tube 420 according to one embodiment. The
sensing tube 420 may represent one or more of the sensing tubes
described herein. As shown in FIG. 3, the HCF 108 may have a hollow
core 432 radially surrounded or encompassed by a cladding 433, as
described in U.S. patent application Ser. No. 14/876,411. Not shown
in FIG. 3 are the solid core fibers 210, 310 (shown in FIGS. 1 and
2) that may be optically coupled with the HCF 108, as described
above.
[0045] In order to measure the presence of gas leaking from the
source 102 (shown in FIG. 2), the gas typically enters the sensing
tube 420 through one or more openings 122 (not shown in FIG. 3 but
shown in FIG. 1) and gradually moves into the hollow core 432 of
the HCF 108. Movement of the gas into the hollow core 432 may take
a considerable amount of time, such as several hours or days, due
to the relatively low concentration of gas that may leak from the
source 102 and the corresponding rate of diffusion. As a result, a
gas leak detection system using the HCFs 108 to detect the leaking
gas may not have sufficient gas inside the hollow core 432 of one
or more HCFs 108 to detect the leak for a considerable amount of
time following commencement of the leak.
[0046] The sensing tube 420 includes an interior shape that
increases the rate at which gas leaking from the source 102 may
enter into the hollow cores 432 of one or more of the HCFs 108
inside the sensing tube 420. This can result in more gas entering
into the HCF(s) 108 sooner after a leak begins relative to other
sensing tubes. The sensing tube 420 generates a pressure
differential across opposite ends 434, 436 of the HCF 108 that
causes the gas to be drawn into the hollow core 432 of the HCF
108.
[0047] The sensing tube 420 includes an interior surface 438 that
radially extends around or encompasses an interior space 440 of the
tube 420. The openings 122 that permit leaking gas to enter into
the tube 420 extend through an outer body 442 of the tube 420 to
provide access to the interior space 440 of the tube 420.
Consequently, the gas leaking from the source 102 can enter into
the interior space 440 of the tube 420. The interior surface 438
may have a reduced throat 442 at or closer to one end 436 of the
HCF 108 than the opposite end 434 of the same HCF 108. The reduced
throat 442 is a section of the tube 420 where the cross-sectional
area of the interior space 440 of the tube 420 is smaller than in a
location at or closer to the opposite end 434 of the HCF 108. For
example, a cross-sectional area 421 of the tube 420 (measured in a
plane that is perpendicular to the flow direction 442 and/or a
center axis of the tube 420) that is at the end 434 of the HCF 108
may be larger than a cross-sectional area 423 of the tube 420
(measured in a plane that is perpendicular to the flow direction
442 and/or a center axis of the tube 420) that is at the end 436 of
the HCF 108. The smaller area 423 restricts the flow of gas and air
through the tube 420 relative to the larger area 421.
[0048] The difference in cross-sectional areas in the sensing tube
420 at different ends 434, 436 of the HCF 108 causes a pressure
differential in the leaking gas between the different ends 434,
436. This pressure differential can cause the gas to be drawn,
pulled, or otherwise sucked into the interior core 432 of the HCF
108. For example, the pressure of gas leaking from the source 102
inside the sensing tube 420 may be lower in the volume of the
interior space 440 of the tube 420 within the reduced throat 442 of
the tube 420 than in other volumes of the interior space 440 of the
tube 420. This lower pressure at the end 436 of the HCF 108 may
cause the gas to be drawn, pulled, or sucked into the interior core
432 of the HCF 108 through the end 434 of the HCF 108. The end 434
of the HCF 108 in the volume of the sensing tube 420 where the
leaking gas pressure is higher than the volume in which the
opposite end 436 of the HCF 108 is located can be referred to as
the higher pressure end while the opposite end 436 may be referred
to as the lower pressure end.
[0049] This pressure differential forces the leaking gas into the
hollow core 432 of the HCF 108 faster than a smaller pressure
differential. The interior shape of the sensing tube 420 can create
the pressure differential to cause the concentration of leaking gas
inside the hollow core 432 to become larger in shorter time periods
than a smaller pressure differential. Greater concentrations or
amounts of the gas within an HCF 108 can result in the presence of
the gas to be more likely to be detected than smaller
concentrations within an HCF 108. As a result, the leaking gas may
be detected sooner than in systems without the pressure
differential.
[0050] While only a single reduced throat section of the sensing
tube 420 is shown in FIG. 3, the sensing tube 420 may include
several reduced throat sections. For example, several or all of the
HCFs 108 may each be located in the sensing tube 420 with one end
of the HCF 108 within a respective reduced throat area of the tube
420 and the opposite end of the HCF 108 within a larger area of the
tube 420.
[0051] FIG. 4 illustrates a cross-sectional view of a segment of a
sensing tube 520 and an HCF 508 that may be disposed inside the
sensing tube 520 according to one embodiment. The sensing tube 520
may represent one or more of the sensing tubes described herein.
The HCF 508 may be similar to the HCF 108 described above. For
example, the HCF 508 may have a hollow core 532 radially surrounded
or encompassed by a cladding 533 and may allow light to propagate
through the interior core 532 to detect the presence of gas, as
described in U.S. patent application Ser. No. 14/876,411. Not shown
in FIG. 4 are the solid core fibers 110, 210, 310 (shown in FIGS. 1
through 2) that may be optically coupled with the HCF 508, as
described above.
[0052] Also as described above, in order to measure the presence of
gas leaking from the source 102 (shown in FIG. 1), the gas
typically enters the sensing tube 520 through one or more openings
122 (not shown in FIG. 4 but shown in FIG. 1) and gradually moves
into the hollow core 532 of one or more of the HCFs 508. In order
to increase the rate at which the gas enters into the hollow core
532 of one or more HCFs 508 and reduce the time needed for
detecting presence of the gas (also referred to as a detection
time), one or more of the HCFs 508 may include a baffle 544. The
baffle 544 can generate a pressure differential within the sensing
tube 520, similar to the reduced throat 442 of the sensing tube 420
shown in FIG. 3. This pressure differential can draw, pull, or suck
the gas in the sensing tube 520 into the HCFs 508.
[0053] In the illustrated embodiment, the baffle 544 is a
cone-shaped body with the smaller diameter cross-sectional area of
the body attached or disposed closer to one end 536 of an HCF 508
than an opposite end 534 of the same HCF 508. Optionally, the
baffle 544 may have another shape, such as a pyramidal shape, a
frustoconical shape, a spherical shape, or the like, or may be
formed from planar bodies extending from the HCF 508. The baffle
544 is oriented at an obtuse angle with respect to the portion of
the outer surface of the cladding 533 of the HCF 508 that is
outside of the baffle 544 (e.g., upstream of the baffle 544 along
the flow direction 442) and at an acute angle with respect to the
portion of the outer surface of the cladding 533 of the HCF 508
that is inside the baffle 544 (e.g., downstream of the baffle 544
along the flow direction 442).
[0054] The baffle 544 may be disposed closer to the end 536 of one
HCF 508 to generate a pressure differential in the gas being sensed
between the ends 534, 536 of the HCF 508. Similar to the reduced
throat 442 in the tube 420 shown in FIG. 3, the baffle 544 may
reduce the cross-sectional area of an interior space 540 of the
tube 520 at or near the end 536 of an HCF 508 relative to the other
end 534 of the same HCF 508. The gas and/or air flowing in the
interior space 540 of the tube 520 (e.g., due to the flow of air
along the flow direction 442) has a reduced cross-sectional area
523 in which to flow between the baffle 544 and the interior
surface of the tube 520 relative to a cross-sectional area 521
between the HCF 508 and the interior surface of the tube 520 in
locations of the tube 520 that are farther from or that do not
include the baffle 544. As a result, a pressure differential is
generated, with the pressure of the gas in the tube 520 being lower
at, near, or closer to the end 536 of the HCF 508 than the opposite
end 534 of the same HCF 508.
[0055] This pressure differential can cause the gas to be drawn,
pulled, or otherwise sucked into the interior core 532 of the HCF
508. For example, the pressure of gas leaking from the source 102
inside the sensing tube 520 may be greater in the volume of the
interior space 540 of the tube 520 within the reduced
cross-sectional area between the baffle 544 and the interior
surface of the tube 520 than in other volumes of the interior space
540 of the tube 520. This lower pressure at the end 536 of the HCF
508 may cause the gas to be drawn, pulled, or sucked into the
interior core 532 of the HCF 508 through the end 534 of the HCF
508.
[0056] The pressure differential forces the leaking gas into the
hollow core 532 of the HCF 508 faster than a smaller pressure
differential. Greater concentrations or amounts of the gas within
an HCF 508 can result in the presence of the gas to be more likely
to be detected than smaller concentrations within an HCF 508. As a
result, the leaking gas may be detected sooner than in systems
without the pressure differential.
[0057] FIG. 5 illustrates a cross-sectional view of a segment of a
sensing tube 620 according to one embodiment. The sensing tube 620
may represent one or more of the sensing tubes described herein.
The sensing tube 620 includes a larger diameter stage or segment
646 and a smaller diameter stage or segment 648. As shown in FIG.
5, a cross-sectional area 621 through which gas leaking from the
source 102 and/or air flows in the larger segment 646 of the
sensing tube 620 may be larger than a cross-sectional area 623
through which gas leaking from the source 102 and/or air flows in
the smaller segment 648 of the sensing tube 620.
[0058] In contrast to the sensing tube 120 shown in FIGS. 1 through
2, the sensing tube 620 may extend from one end 652 to an opposite
end 654, with the opposite ends 652, 654 disposed closer together
(e.g., at the same end of the test location 104 shown in FIG. 1)
than the tube 620 without the bend 650 (e.g., the tube 120 shown in
FIG. 1). Placing the ends 652, 654 of the tube 620 closer together
can allow for more components of the gas leak detection system to
be co-located than if the ends 652, 654 were located farther apart.
For example, the pump 124 (shown in FIG. 1) can be coupled with the
end 652 and co-located with the interrogator device 212 (shown in
FIG. 1), instead of at opposite ends of the sensing tube 120.
[0059] The segments 646, 648 are fluidly coupled with each other.
In the illustrated embodiment, the segments 646, 648 are fluidly
coupled by a bend 650 in the tube 620. Optionally, another conduit
may be used to fluidly couple the segments 646, 648. The fluid
coupling of the segments 646, 648 allows air flowing from the pump
124 at or coupled with the end 652 of the tube 620 to flow (with
gas leaking from the source 102 in the event of a leak) through the
larger segment 646 of the tube 620 along the flow direction 442,
through the bend 650 or other fluid coupling between the segments
646, 648, and through the smaller segment 648 (e.g., in a direction
that is opposite the flow direction 442 in the larger segment
646).
[0060] Several HCFs 108 may be coupled with the sensing tube 620.
Not shown in FIG. 5 are the solid core fibers 110, 210, 310 (shown
in FIGS. 1 through 2) that may be optically coupled with the HCF
108, as described above. In the illustrated embodiment, one end 656
of each of the HCFs 108 extends into the larger segment 646 of the
sensing tube 620 (e.g., through one or more openings in the sensing
tube 620) and an opposite end 658 of the same HCF 108 extends into
the smaller segment 648 of the same sensing tube 620.
[0061] In order to measure the presence of gas leaking from the
source 102, the gas typically enters the sensing tube 620 through
one or more openings 122 (not shown in FIG. 5 but shown in FIG. 1)
and gradually moves into the hollow core of one or more of the HCFs
108. The pump 124 may be fluidly coupled with the end 652 of the
larger segment 646 of the sensing tube 620 to generate air flow
along the flow direction 442. This air flow may move the leaking
gas through the sensing tube 620, as described above.
[0062] The different cross-sectional areas 621, 623 of the segments
646, 648 of the sensing tube 620 can generate a pressure
differential in the leaking gas across the opposite ends 656, 658
of one or more of the HCFs 108. The larger cross-sectional area 621
in the larger segment 646 of the sensing tube 620 causes the
pressure of the leaking gas at the end 656 of one or more of the
HCFs 108 to be higher than the pressure of the leaking gas at the
end 658 of the same HCF(s) 108 in the smaller segment 648 (e.g.,
due to the smaller cross-sectional area 623). The gas and/or air
flowing in the smaller segment 648 of the sensing tube 620 has a
smaller cross-sectional area 623 in which to flow relative to the
cross-sectional area 621 of the larger segment 646 of the sensing
tube 620. As a result, the pressure differential is generated, with
the pressure of the gas in the tube 620 being lower at, near, or
closer to the end 658 of the HCF 108 than the opposite end 656 of
the same HCF 108.
[0063] This pressure differential can cause the gas to be drawn,
pulled, or otherwise sucked into the interior core of the HCF(s)
108. The pressure of gas leaking from the source 102 inside the
sensing tube 620 may be lower in the smaller segment 648 than the
larger segment 646. This lower pressure at the end 658 of the HCF
108 may cause the gas to be drawn, pulled, or sucked into the
interior core of the HCF 108 through the end 656 of the HCF 108.
Greater concentrations or amounts of the gas within an HCF 108 can
result in the presence of the gas to be more likely to be detected
than smaller concentrations within an HCF 108. As a result, the
leaking gas may be detected sooner than in systems without the
pressure differential.
[0064] FIG. 6 illustrates a gas leak detection system 700 according
to another embodiment. FIG. 6 also illustrates a magnified view 701
of a portion of the system 700. The system 700 includes a sensing
tube 720, which may be similar or identical to the sensing tube 120
shown in FIG. 1. Although not shown in FIG. 6, the sensing tube 720
may include openings 122 (shown in FIG. 1) to allow gas leaking
from the source 102 (shown in FIG. 1) to enter into the interior of
the sensing tube 720.
[0065] One or more HCFs 108 are optically coupled with an
interrogator 212 or 312 (not shown in FIG. 6, but shown in FIGS. 1
through 2) of the system 700 by one or more solid core fibers 710,
which may be similar or identical to the solid core fibers 110,
210, or 310. In contrast to the gas leak detection systems and
sensing tubes shown in FIGS. 1 through 4, the solid core fibers 710
and part or most (e.g., at least a majority) of the HCFs 108 are
disposed outside of the sensing tube 720 in the system 700. The
solid core fibers 710 may be attached to an exterior surface of the
sensing tube 720, and may be connected with one or more HCFs 108 by
a mechanical splice or connector 760. The splice 760 optically
couples the solid core fiber 710 with the end 658 of the HCF 108 to
permit light propagating through the solid core fiber 710 to enter
into and propagate through the hollow core of the HCF 108. In one
embodiment, the splice 760 may be used to optically couple the
solid core fibers and HCFs of one or more other embodiments
described herein. The splice 760 may be open to atmospheric
pressure outside of the sensing tube 720.
[0066] A segment of the HCF 108 that includes the end 656 of the
HCF 108 may be disposed inside the sensing tube 720 while a
remainder of the HCF 108 is disposed outside of the sensing tube
720. In one embodiment, the segment of the HCF 108 that is inside
the sensing tube 720 is shorter than the segment of the HCF 108
that is outside of the sensing tube 720. The sensing tube 720
includes one or more sensor openings 762 through which the HCF(s)
108 extend into the interior of the sensing tube 720. The sensor
openings 762 may be openings in the sensor tube 720 in addition to
the openings 122 through which gas leaking from the source 102
(shown in FIG. 1) enters into the sensing tube 720. Alternatively,
one or more of the openings 122 through which the gas enters the
sensing tube 720 may be used as one or more sensor openings
762.
[0067] The end 656 of the HCF 108 is inserted into the interior
space of the sensing tube 720 through or via the sensor opening
762. A seal 764 is provided over the sensor opening 762 with the
HCF 108 extending through the seal 764. The seal 764 may be a
hermetic seal that does not allow gas or air inside the sensor tube
720 from flowing into or out of the sensor tube 720 through the
sensor opening 762. The seal 764 may be formed from a rigid or
elastic material, such as a thermoplastic material, a rubber
material, etc.
[0068] As described above, gas leaking from the source 102 may
enter into the interior of the sensing tube 720 through one or more
openings 122 in the tube 720. This gas may enter into the hollow
core of one or more HCFs 108 through the end(s) 656 of the
respective HCFs 108. Light propagating outside of the sensing tube
720 in the solid core fiber(s) 710 may enter into the HCF 108 and
optionally be reflected by a reflector at or near the end 656 of
the HCF 108 to detect the presence of the gas in the hollow core of
the HCF 108, as described above.
[0069] Placing the solid core fiber(s) 710 and at least a segment
of the HCFs 108 outside of the sensing tube 720 allows for the
system 700 to be added to an existing sensing tube 720 without
having to replace or significantly alter the sensing tube 720. For
example, while additional holes may need to be created in the
sensing tube 720 to form the sensor openings 762, other alterations
to the sensing tube 720 (including changes to the interior of the
sensing tube 720) may not need to be made. This can allow for the
embodiment of the system 700 shown in FIG. 6 to be used to easily
retrofit an existing sensing tube with the system 700.
[0070] The end of tube 720 at which the flowing gas exits may
additionally have a flow restriction or a relief valve. When air is
pumped into tube 720 from the other end, the pressure inside tube
720 increases due to the restriction or relief valve. This
generates a pressure differential across the HCF and causes gas
within tube 720 to be forced into the opening 656 of the HCF
because the other end of the HCF 658 is outside the tube and is at
the lower atmospheric pressure.
[0071] FIG. 7 illustrates a flowchart of one embodiment of a method
800 for detecting presence of a gas-of-interest in a test location.
The method 800 may be performed by one or more embodiments of the
systems described herein to detect the presence of a
gas-of-interest, such as but not limited to methane, leaking from a
pipeline, in an underground mine, on a mining platform, or in
another location.
[0072] At 802, air is optionally directed through a sensing tube
having plural hollow core fibers disposed in different locations in
the sensing tube. This air may be pushed through the sensing tube
to move the gas-of-interest through the sensing tube to aid in
detection of the gas. The air may be forced through the sensing
tube at periodic intervals, at selected or on-demand times,
continuously, or at other times. For example, the air may not be
continually forced or pumped through the sensing tube.
[0073] At 804, the pressure inside the sensing tube is optionally
altered. The pressure may be altered to generate a pressure
differential across or between opposite ends of one or more of the
hollow core fibers, as described above. This pressure differential
may be created in order to draw, pull, or suck air and/or gases in
the sensing tube into the one or more HCFs to reduce the time
period needed to detect the potential presence of a
gas-of-interest. Alternatively, 804 may not be performed.
[0074] At 806, light is directed toward the plural hollow core
fibers. The light may be directed toward the hollow core fibers
with one or more designated or operator-selected wavelengths. These
wavelengths may be selected based on the gas-of-interest. For
example, different gases may absorb different amounts of different
wavelengths of light. Controlling the wavelength(s) of light
propagating to and into the hollow core fibers allows for
determination of which gas(es) are detected. The light may be
directed to the hollow core fibers through one or more solid core
fibers, as described above.
[0075] At 808, at least some of the light is received after passing
through one or more of the hollow core fibers. For example, the
light may pass through the hollow core fibers and a portion of the
light may be absorbed by gas(es) in one or more of the hollow core
fibers. Optionally, the light may pass through one or more hollow
core fibers and be reflected back by reflectors in or connected
with the hollow core fibers.
[0076] At 810, the light that is received is examined to determine
whether one or more wavelengths of the light were absorbed in one
or more of the hollow core fibers. A reduction in amplitude of one
or more wavelengths of the light (e.g., in terms of numbers of
photons detected, intensity, or other measurement) relative to
other wavelengths of light may indicate that the reduced wavelength
or wavelengths of light were absorbed by a gas within one or more
of the hollow core fibers.
[0077] At 812, a determination is made as to whether the absorbed
light indicates the presence of a gas-of-interest. For example, if
one or more wavelengths of the light were reduced, then a
determination may be made as to whether the wavelength or
wavelengths that were reduced are the wavelengths of light absorbed
by the gas-of-interest. If the gas-of-interest does not absorb
these wavelengths of light, then the gas-of-interest may not be
present at the hollow core fiber (from which the light being
examined was received). As a result, flow of the method 800 can
return toward 802 or optionally, toward 804, toward 806, or may
terminate. But, if the gas-of-interest does absorb these
wavelengths of light, then the gas-of-interest may be present at
the hollow core fiber (from which the light being examined was
received). As a result, flow of the method 800 can proceed toward
814.
[0078] At 814, a location of the gas-of-interest is determined. For
example, based on the location of the hollow core fiber that
reduced the one or more wavelengths of light that are absorbed by
the gas-of-interest and the rate of flow of the air through the
sensing tube, the location of a leak of the gas or a source of the
gas can be determined. The location may be determined by
calculating the time for the air to flow to the hollow core fiber
before the gas signal is detected, and by calculating the distance
from the source of the gas based on this time.
[0079] At 816, one or more responsive actions may be implemented.
For example, responsive to detecting a gas leak or source of gas,
the processors 118 may generate and communicate an alarm signal
that causes an output device (e.g., a light, a speaker, etc.) to
warn of the presence of the gas and the location of the gas.
Optionally, the alarm signal may be communicated to a pump that is
moving the gas through a pipeline to shut off the pump and stop
moving the gas through the pipeline. Alternatively, one or more
other actions may be implemented.
[0080] It should be noted that the particular arrangement of
components (e.g., the number, types, placement, or the like) of the
illustrated embodiments may be modified in various alternate
embodiments. For example, in various embodiments, different numbers
of a given module or unit may be employed, a different type or
types of a given module or unit may be employed, a number of
modules or units (or aspects thereof) may be combined, a given
module or unit may be divided into plural modules (or sub-modules)
or units (or sub-units), one or more aspects of one or more modules
may be shared between modules, a given module or unit may be added,
or a given module or unit may be omitted.
[0081] As used herein, a structure, limitation, or element that is
"configured to" perform a task or operation is particularly
structurally formed, constructed, or adapted in a manner
corresponding to the task or operation. For purposes of clarity and
the avoidance of doubt, an object that is merely capable of being
modified to perform the task or operation is not "configured to"
perform the task or operation as used herein. Instead, the use of
"configured to" as used herein denotes structural adaptations or
characteristics, and denotes structural requirements of any
structure, limitation, or element that is described as being
"configured to" perform the task or operation.
[0082] It should be noted that the various embodiments may be
implemented in hardware, software or a combination thereof. The
various embodiments and/or components, for example, the modules, or
components and controllers therein, also may be implemented as part
of one or more computers or processors. The computers or processors
may include a computing device, an input device, a display unit and
an interface, for example, for accessing the Internet. The computer
or processor may include a microprocessor. The microprocessor may
be connected to a communication bus. The computer or processor may
also include a memory. The memory may include Random Access Memory
(RAM) and Read Only Memory (ROM). The computer or processor further
may include a storage device, which may be a hard disk drive or a
removable storage drive such as a solid state drive, optic drive,
and the like. The storage device may also be other similar means
for loading computer programs or other instructions into the
computer or processor.
[0083] It is to be understood that the above description is
intended to be illustrative, and not restrictive. For example, the
above-described embodiments (and/or aspects thereof) may be used in
combination with each other. In addition, many modifications may be
made to adapt a particular situation or material to the teachings
of the invention without departing from its scope. Dimensions,
types of materials, orientations of the various components, and the
number and positions of the various components described herein are
intended to define parameters of certain embodiments, and are by no
means limiting and are merely exemplary embodiments. Many other
embodiments and modifications within the spirit and scope of the
claims will be apparent to those of skill in the art upon reviewing
the above description. The scope of the invention should,
therefore, be determined with reference to the appended claims,
along with the full scope of equivalents to which such claims are
entitled. In the appended claims, the terms "including" and "in
which" are used as the plain-English equivalents of the respective
terms "comprising" and "wherein." Moreover, in the following
claims, the terms "first," "second," and "third," etc. are used
merely as labels, and are not intended to impose numerical
requirements on their objects. Further, the limitations of the
following claims are not written in means-plus-function format and
are not intended to be interpreted based on 35 U.S.C. .sctn.112(f),
unless and until such claim limitations expressly use the phrase
"means for" followed by a statement of function void of further
structure.
[0084] This written description uses examples to disclose the
various embodiments, and also to enable a person having ordinary
skill in the art to practice the various embodiments, including
making and using any devices or systems and performing any
incorporated methods. The patentable scope of the various
embodiments is defined by the claims, and may include other
examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims if the
examples have structural elements that do not differ from the
literal language of the claims, or the examples include equivalent
structural elements with insubstantial differences from the literal
language of the claims.
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