writing Bracket for Strain Sensor
TECHNICAL FIELD
t disclosure relates to an apparatus for mounting sensors on pipe
BACKGROUND
[0002] In connection with the recovery of hydrocarbons from the earth, wellbores are
generally drilled using any of a variety of different methods and equipment. According
to one common method, a drill bit is rotated against the subsurface formation to form
the wellbore. The drill bit may be rotated in the wellbore through the rotation of a drill
string attached to the drill bit and/or by the rotary force imparted to the drill bit by a
subsurface drilling motor powered by the flow of drilling fluid down the drill string and
through downhole motor.
[0003] The flow of drilling fluid can exhibit variations in pressure. These pressure
variations can cause dimensional changes in solid structures such as piping that carries
the drilling fluid to and from the drill string. Strain gauges are used for detection and
measurement of absolute dimensional changes of solid structures, such a piping for
drilling fluid, but such changes are generally very slow and difficult to observe with
known equipment and measurement methods.
DESCRIPTION OF DRAWINGS
[0004] FIG. 1 is a perspective view of an example optical sensor mount.
[0005] FIGS. 2 and 3 are exploded and perspective views of another example optical
sensor mount.
[0006] FIG. 4 is a conceptual representation of an example optical sensor mount in a
stressed condition.
[0007] FIG. 5 is a conceptual representation of an example optical sensor mount in a
stressed condition.
[0008] FIG. 6 is another conceptual representation of an example optical sensor
mount in a stressed condition.
DETAILED DESCRIPTION
[0009] This document describes systems and techniques for mounting sensor
attachments to drilling fluid (also referred to in the industry as drilling mud) piping on
drilling rigs. The assemblies described in this document can be used to mount several
different types of optical sensors, including temperature, pressure, and/or strain
sensors. Some of these sensors can be optical sensors and gauges based on the
operating principles of a Fiber-Bragg grating and/or Fabry-Perot interferometer.
[0010] In general, optical sensor mounts clamp, attach, or are otherwise affixed to an
outside surface of one or more pipes in the drilling fluid piping system. Fluid (for
example, drilling fluid) flowing through the pipe exerts a pressure force outward against
the pipe, which causes small changes in the diameter of the pipe that vary with the
pressure of the fluid within. The optical sensor mounts mechanically transfer, and in
some implementations, amplify or reduce, changes in pipe diameter to one or more
sensors. The signal outputs of such sensors can then be processed to observe
changes in the diameter of the pipe. The changes in diameter of the pipe diameter may
WO 2015/099763 PCT7US2013/077990
be processed using known physical characteristics of pressure pipes as described, for
example, in "Pressure Vessel Design Manual" by Dennis Moss. Detection of said
changes can allow for downhole pressure pulse detection whereas said pressure pulses
can convey the specific information or data content, examples of which are described in
Halliburton patents US7480207B2 and US7404456B2.
[0011] FIG. 1 is a perspective view of an example optical sensor mount 100. The
mount 100 is a generally circular mechanical clamp having an inner diameter 102 sized
to accommodate an outer diameter of a pipe (not shown) on which the mount 100 is to
be mounted. The mount 100 includes three main sections, including a bottom flexing
section 120, a first upper flexing section 140, and a second upper flexing section 160.
[0012] The bottom flexing section 120 is a generally semi-circular arcuate portion,
having a terminal end 122a in a mounting wing 124a, and a terminal end 122b in a
mounting wing 124b. The mounting wing 124a is formed generally perpendicular to the
terminal end 122a, and the mounting wing 124b is formed generally perpendicular to the
terminal end 122b. The mounting wing 122a includes a bore 126a, and the mounting
wing 122b includes a bore 126b, the bores 126a-126b for receiving a removable
connector (not shown) such as a bolt or other appropriate fastener.
[0013] The bottom flexing section 120 has a thickness 128. The bottom flexing
section 120 includes a subsection 130 that has a thickness 132 that is less than the
thickness 128. In some implementations, as the bottom flexing section 120 flexes, the
relatively lesser thickness 132 of the subsection 130 may cause distortion of the bottom
flexing section 120 to be at least partly concentrated along the subsection 130.
3
[0014] The upper flexing section 140 includes an arcuate portion 142 that is
generally quarter-circular in shape, terminating at a terminal end 143 in a mounting wing
144 and a terminal end 146 in a mounting wing 148. The mounting wing 144 is formed
generally perpendicular to the terminal end 143 and includes a bore 150 for receiving a
removable connector (not shown) such as a bolt or other appropriate fastener when the
bore 150 is aligned with the bore 126a to removably affix the upper flexing section 140
to the bottom flexing section 120.
[0015] The mounting wing 148 is formed generally tangent to the terminal end 146
and includes a pivot pin assembly 152 having a bore 153 that is formed parallel to a
central longitudinal axis 103 of the mount 100. The bore 153 is formed to receive a
removable connector (not shown) such as a bolt or other appropriate fastener.
[0016] A sensor mounting arm 154 extends generally perpendicular from the upper
flexing section 140. The sensor mounting arm 154 including at least one receptacle 156
sized to receive and retain an end 192a of a sensor 190, such as a strain gauge, an
optical sensor, a Fiber-Bragg grating, a Fabry-Perot interferometer etalon, or any other
appropriate sensor.
[0017] The upper flexing section 160 includes an arcuate portion 162 that is
generally quarter-circular in shape, terminating at a terminal end 163 in a mounting wing
164 and a terminal end 166 in a mounting wing 168. The mounting wing 164 is formed
generally perpendicular to the terminal end 163 and includes a bore 170 for receiving a
removable connector (not shown) such as a bolt or other appropriate fastener when the
bore 170 is aligned with the bore 126b to removably affix the upper flexing section 160
to the bottom flexing section 120.
[0018] The mounting wing 168 is formed generally tangent to the terminal end 166
and includes a pivot pin assembly 172 having a bore 174 that is formed parallel to the
central longitudinal axis 103 of the mount 100. The bore 174 is formed to receive a
removable connector (not shown) such as a bolt or other appropriate fastener when
aligned with the bore 153.
[0019] A sensor mounting arm 175 extends generally perpendicular from the upper
flexing section 160. The sensor mounting arm 175 including at least one receptacle 176
sized to receive and retain an end 192b of the sensor 190.
[0020] The mount 100 includes a collection of adjustment rods 180. The adjustment
rods extend through the mount 100 inwardly in a radial direction toward the longitudinal
axis 103 of the mount 100 through a collection of adjustment openings 181. The inward
end of each of the adjustment rods 180 terminates in a landing pad 182. The
adjustment rods 180 and the landing pads 182 form a collection of adjustment
assemblies 184 formed to move the adjustment rods 180 and the landing pads 182 into
adjustable contact with the pipe on which the mount 100 is to be mounted. In some
embodiments, the adjustment assemblies 184 can include female threads in each of the
adjustment openings, and the adjustment rods 180 can include at least a portion with
male threads adapted to be received in the female threads. In some embodiments,
compression pads can be affixed to the landing pads 182. In some embodiments, the
compression pads can include layers of vibration and acoustic noise absorbing material.
[0021] When assembled in a substantially unstressed or a predetermined prestressed
or strained configuration, the sensor mounting arms 154 and 175 are oriented
substantially parallel to each other. In such a substantially parallel configuration, the
sensors 190 are stressed to substantially the same degree. For example, two sensors
190 in the example parallel configuration can provide substantially the same outputs,
which can be used to cancel out common mode noise differential measurement
configurations.
[0022] In some implementations, the mount 100 can be removably affixed to a pipe
by placing a fastener though the bores 126a and 150, and by placing another fastener
through the bores 126b and 170, while omitting a fastener from the pivot pin assemblies
152, 172. In such an example configuration, as the pipe varies in diameter (e.g., due to
variations in pressure of the fluid within the pipe), the unfastened pivot pin assemblies
152, 172 can separate slightly, causing the sensor mounting arms 154 and 175 to move
away from their substantially parallel, unstressed configuration. As the sensor mounting
arms 154 and 175 diverge, the sensors 190 mounted at different radial positions on the
sensor mounting arms 154 and 175 will experience differing amounts of stress. In some
implementations, the differing amounts of stress can produce a differential signal by the
sensors 190 that can be processed to determine the absolute or change in fluid
pressure within the pipe.
[0023] Referring now to FIG. 4, a simplified version of the mount 100 is shown to
illustrate one example effect of stress upon the mount 100. In the illustrated example,
the upper flexing sections 140, 160 are removably affixed to the bottom flexing section
120 by a pair of bolts 410 and the restraining bolt (not shown here) is inserted in the
bores 153, 174. When the mount 100 is clamped about a pipe (not shown) that is
substantially unpressurized and therefore substantially unexpanded, the mount 100 can
take on the configuration shown in solid lines. When the pipe is pressurized, the walls
of the pipe will expand. This expansion will cause the sensor mount arms 154 and 175
to converge or otherwise move relatively closer, taking on the configuration shown in
dotted lines.
[0024] Referring again to FIG. 1, in some implementations, a linking plate 195 can
be removably affixed to the radially distal ends of the sensor mounting arms 154 and
175 with respect to each other, mechanically linking the sensor mounting arms 154 and
175 to each other. By linking the sensor mounting arms 154 and 175 to each other
through the linking plate 195, the movement of the sensor mounting arms 154 and 175
as the pipe expands and contracts can be modified. In some implementations, the
linking plate 195 may be used as an aid to assembly of the mount 100 about the pipe.
For example, the linking plate 195 may be used to temporarily affix the upper flexing
sections 140, 160 during assembly, and may be removed after the upper flexing
sections 140, 160 are affixed to the bottom flexing section 120.
[0025] Referring now to FIGS. 5 and 6, simplified versions of the mount 100 are
shown to illustrate the effects of the linking plate 195 on the flexure of the mount 100.
FIG. 5 is a conceptual example configuration 500 of the mount 100 without the linking
plate 195 and without the restraining bolt. In the example configuration 500, as the pipe
(not shown) expands within the mount 100, the sensor mounting arms 154 and 175
move from their substantially unstressed or pre-stressed configuration, as depicted in
dotted lines, relatively apart to the stressed configuration depicted in solid lines. In
general, without the linking plate 195 in place, the radially distal ends 510 of the sensor
arms 154 and 175 will move relatively further apart from each other than will more
radially proximal portions 520 of the sensor arms 154 and 175.
7
[0026] In some implementations, as the pressurized pipe's diameter D increases by
X, the strain can be expressed as a ratio X/D. The same displacement X applied over a
shorter distance L between expansion arms can lead to strain amplification because X/L
» X/D.
[0027] FIG. 6 is a conceptual example configuration 600 of the mount 100 with the
linking plate 195 affixed across the sensor mounting arms 154 and 175 and the
restraining bolt not present. In the example configuration 600, as the pipe (not shown)
expands within the mount 100, the linking plate 195 partly constrains movement of the
radially distal ends 510, causing the radially proximal portions 520 of the sensor
mounting arms 154 and 175 to move from their substantially unstressed or pre-stressed
configuration, as depicted in dotted lines, relatively apart to the stressed configuration
depicted in solid lines. In general, with the linking plate 195 in place, the radially
proximal portion 520 of the sensor mounting arms 154 and 175 will move relatively
further apart from each other than will more radially distal ends 510 of the sensor arms
154 and 175. When the linking plate 195 is used, the pipe diameter expansion, which
can be expressed as dD = X, can result in a minimal top gap increase Xmin at ends of
sensor mounting arms 154 and 175 near the linking plate whereas Xmin is close to zero
with additional and relatively larger Xmax increase in distance between arms at location
closer to the pipe whereas Xmax can be approximated as Xmax = ~PI * X.
[0028] Referring again to FIG. 1, in some implementations, a pivot pin (not shown)
can be inserted through the bores 148, 168 of the sensor mounting arms 154 and 175.
By placing the pivot pin in the bores 148, 168, as the pipe expands and contracts, the
divergence of the sensor mounting arms 154 and 175 will pivot about the pivot pin. For
8
example, as the pipe expands, the sensor mounting arms 154 and 175 can be caused
to diverge from their substantially parallel, unstressed configuration and the arms will
move inwardly at an angle toward each other.
[0029] In some embodiments, the pivot pin can be compressible or otherwise
deformable, or can include a compressible or otherwise deformable coating about a
substantially non-compressible core rod. In some implementations, the use of selected
compressible or deformable components for the pivot pin can provide selectable
modification of convergence or divergence of the sensor mounting arms 154 and 175.
For example, by including a compressible pivot pin in the pivot pin assemblies 152, 172,
separation of the pivot pin assemblies 152, 172 can be permitted in a reduced manner
relative to movement that may occur with or without the use of a non-deformable pivot
pin.
[0030] In some embodiments, the linking plate 195 can be formed to have a selected
spring coefficient. For example, the stiffness of the linking plate 195 can be selected to
selectably modify the divergence of the sensor mounting arms 154 and 175 under
various stress configurations. In some embodiments, one or more sensors can be
mounted on the linking plate 195. For example, sensors can be configured to provide
signals that indicate tensile, compressive, or bending stresses at the linking plate 195.
In some embodiments, one or more sensors can be mounted between inner surfaces of
the sensor mounting arms 154 and 175 and/or in any other suitable section of 120, 140,
and/or 160. For example, a load cell can be mounted between the sensor mounting
arms 154 and 175 to provide a signal in response to relative inward and outward
movements of the sensor mounting arms 154 and 175.
9
[0031] While the present example is shown and described as including four sets of
the adjustment assemblies 184, various implementations can include any appropriate
number of the adjustment assemblies 184 mounted through corresponding ones of the
adjustment openings 181. For example, one of the adjustment assemblies 184 can be
mounted on the upper flexing section 140, and another one of the adjustment
assemblies 184 can be mounted in the adjustment opening 181 located in the bottom
flexing section 120 approximately 180 degrees away. In another example, one of the
adjustment assemblies 184 can be mounted in each of the upper flexing sections 140,
160, and a third one of the adjustment assemblies 184 can be mounted in the
adjustment opening 181 located in the central section of the subsection 130.
[0032] FIGS. 2 and 3 are exploded and perspective views of another example optical
sensor mount 200. In general, the mount 200 is removably or permanently affixed to a
pipe 201 to mechanically transmit variations in the diameter of the pipe 201 to a
collection of sensors 202, such as a strain gauges, optical sensors, Fiber-Bragg
gratings, Fabry-Perot interferometers, or any other appropriate sensors.
[0033] The mount 200 includes a pair of mounting blocks 210 each having a
proximal surface 212 and a distal surface 214. The proximal surfaces 212 are
positionable adjacent to an outer surface 203 of a wall 204 of the pipe 201, and spaced
about 180 degrees apart from each other.
[0034] The mount 200 includes a pair of sensor mounting arms 220. One of the
sensor mounting arms 220 is removably affixed to each of the distal surfaces 214 by a
collection of fasteners 222, such as bolts, screws, or other appropriate connectors. The
sensor mounting arms 220 each includes a receptacle 224 configured to receive and
10
retain an end 232 of a stem rod 230. The ends 232 are further retained by fasteners
231, such as nuts, retaining pins, or other appropriate connectors. In some
embodiments, the ends 232 and the fasteners 231 can form a tension adjustment
mechanism for the stem rod 230. For example, the adjustment mechanism can include
male threads on at least one of the ends 232 of the stem rod 230, and the fasteners 231
can include female threads adapted to engage the male threads of the stem rod 230. In
such examples, the fasteners 231 can be threaded along the ends 232 to adjust the
tension along the stem rod 230.
[0035] The stem rod 230 includes at least one longitudinal receptacle 234 in an outer
surface of the stem rod 230. Each of the longitudinal receptacles 234 is formed to
receive and retain one of the sensors 202. The stem rod 230 has a first cross sectional
area 236 at a central portion of one of the longitudinal receptacles 234, and a second
cross sectional area 238 at a central portion of another one of the longitudinal
receptacles 234. As discussed later herein, the cross sectional areas may be the same
or different.
[0036] In some implementations, a magnet 240 is located in a receptacle 242 formed
in each of the proximal surface 212 of the mounting blocks 210. The magnets 240
include a first surface 244 positionable adjacent to the outer surface 203 of the wall 204
of the pipe 201, and a surface 246 positionable adjacent to the mounting blocks 210. In
some embodiments, the mount 200 can be mounted to the pipe 201 by the magnets
240. In some embodiments, the mount 200 can be mounted to the pipe 201 by welding,
gluing, or otherwise adhering the mounting blocks 210 to the pipe 201.
n
[0037] The mount 200 is assembled in a predetermined strain condition in which the
sensor mounting arms 200 are generally parallel to each other and the stem rod 230 is
mounted generally perpendicular to a longitudinal axis of each of the sensor mounting
arms 220. The pressure of fluid flowing through the pipe 201 exerts pressure on the
wall 204, causing variations in the diameter of the outer surface 203. As the diameter
changes, the distance between the mounting blocks 210 changes as well. Since the
mounting blocks 210 are connected to each other though the sensor mounting arms
220 and across the stem rod 230, as the pipe 201 expands and contracts the stem rod
230 is caused to expand or contract and/or flex. The sensors 202, mounted in the
receptacles 234, are caused to expand or contract and/or flex along with the stem rod
230 and provide signals that vary as a function of the flexure and the compressive or
tensile stress in the rod.
[0038] In some embodiments, the first cross sectional area 236 can have a different
cross sectional area than the second cross sectional area 238. In such embodiments,
the first cross sectional area 236 will expand or contract or flex at a different rate than
the second cross sectional area 238 relative to the expansion and contraction of the
pipe 201, and the differing rates of expansion or contraction and flexure can produce
differing amounts of stress among the sensors 202. In some implementations, the
differing amounts of stress in the sensors can produce a differential signal that can be
processed to determine the absolute or changes in fluid pressure within the pipe. In
some implementations, the thicknesses of the stem rod 230, the first cross sectional
area 236, and the second cross sectional area 238 can be formed to selectively
12
determine the amount compression, tension or flexure that occurs along the stem rod
230, and/or between the sensors 202.
[0039] Although a few implementations have been described in detail above, other
modifications are possible. For example, logic flows do not require the particular order
described, or sequential order, to achieve desirable results. In addition, other steps
may be provided, or steps may be eliminated, from the described flows, and other
components may be added to, or removed from, the described systems. Accordingly,
other implementations are within the scope of the following claims.

WHAT IS CLAIMED IS:
1. A system for mounting a strain sensor on a tubular pipe, the system comprising:
a mechanical clamp having a central longitudinal axis, said mechanical clamp
having a plurality of sections including:
a bottom flexing section having an arcuate portion terminating at a first
terminal end in a first mounting wing and said bottom flexing section terminating at a
second end in a second mounting wing, each of said mounting wings including an
opening through the wing for receiving a removable connector;
a first upper flexing section having an arcuate portion terminating at a first
terminal end in a mounting wing and said first upper flexing section terminating at
second terminal end in a pivot pin assembly having a bore parallel to the central
longitudinal axis of the clamp, the mounting wing having an opening through the wing
for receiving a removable connector;
a second upper flexing section having an arcuate portion terminating at a
first terminal end in a mounting wing and said first upper flexing section terminating at
second terminal end in a pivot pin assembly having a bore parallel to the central
longitudinal axis of the clamp, the mounting wing having an opening through the wing
for receiving a removable connector;
a first sensor mounting arm disposed outwardly on the first upper flexing
section, said sensor mounting arm including at least one receptacle sized to receive and
retain a first end of a first strain gauge; and
a second sensor mounting arm disposed outwardly on the second upper
flexing section, said sensor mounting arm including at least one receptacle sized to
receive and retain a second end of a first strain gauge.
2. The mounting system of claim 1, wherein when the mechanical clamp is
assembled in a predetermined strain condition, the first sensor mounting arm is parallel
to the second sensor mounting arm.
3. The mounting system of claims 1 further including a second receptacle in the first
mounting arm sized to receive and retain a first end of a second strain gauge and a
second receptacle in the second mounting arm sized to receive and retain a second
end of a second strain gauge.
4. The mounting system of claim 1, wherein the strain gauge is a Fiber-Bragg
grating strain gauge.
5. The mounting system of claim 1, wherein the strain gauge is a Fabry-Perot
interferometer.
6. The mounting system of any of claims 1 to 5 further including linking plate
connected to a distal end of the first mounting arm and connected to a distal end of the
second mounting arm.
7. The mounting system of claim 1 further including a pivot pin with a compressible
coating, wherein said pivot pin including the compressible coating is sized to be
received in the bore of the pivot pin assembly.
8. The mounting assembly of claim 1, wherein the bottom flexing section further
includes at least one adjustment opening there through disposed inwardly in a radial
direction toward the longitudinal axis, said opening sized to receive a first adjustment
rod; and
wherein the first upper flexing section further includes at least one adjustment
opening there through disposed inwardly in a radial direction toward the longitudinal
axis, said opening sized to receive a second adjustment rod; and
wherein the second upper flexing section further includes at least one adjustment
opening there through disposed inwardly in a radial direction toward the longitudinal
axis, said opening sized to receive a third adjustment rod; and
wherein the first, second, and third adjustment rods each include a landing pad
affixed to an end of each adjustment rod positioned toward the longitudinal axis.
9. The mounting system of claim 8 further including an adjustment mechanism for
each rod adapted to move the rod and the landing pad mounted thereon into contact
with the pipe on which the mounting system is to be mounted.
10. The system of claim 8 further including a compression pad affixed to each of the
landing pads.
11. The mounting system of claim 10, wherein the compression pad includes layers
of vibration and acoustic noise absorbing material.
12. A method of mounting a strain sensor to a pipe comprising:
positioning a mechanical clamp circumferentially around an outer surface of a
pipe wall, said mechanical clamp having a central longitudinal axis, said mechanical
clamp having a plurality of sections including:
a bottom flexing section having an arcuate portion terminating at a first
terminal end in a first mounting wing and said bottom flexing section terminating at a
second end in a second mounting wing, each of said mounting wings including an
opening through the wing for receiving a removable connector;
a first upper flexing section having an arcuate portion terminating at a first
terminal end in a first mounting wing and said first upper flexing section terminating at
second terminal end in a pivot pin assembly having a bore parallel to the central
longitudinal axis of the clamp, the mounting wing having an opening through the wing
for receiving a removable connector;
a second upper flexing section having an arcuate portion terminating at a
first terminal end in a first mounting wing and said first upper flexing section terminating
at second terminal end in a pivot pin assembly having a bore parallel to the central
longitudinal axis of the clamp, the mounting wing having an opening through the wing
for receiving a removable connector;
a first sensor mounting arm disposed outwardly on the first upper flexing
section, said sensor mounting arm including at least one receptacle sized to receive and
retain a first end of a first strain gauge; and
a second sensor mounting arm disposed outwardly on the second upper
flexing section, wherein when the mechanical, said sensor mounting arm including at
least one receptacle sized to receive and retain a second end of a first strain gauge;
and
positioning a strain sensor with a first end in the receptacle of the first sensor
mounting arm and a second end of the strain sensor in the receptacle of the second
sensor mounting arm.
13. The method of claim 12 further comprising:
inserting one or more individual adjustment rods inwardly in a radial direction
toward the longitudinal axis in one or more radial openings in one or more of the bottom
flexing section, the first upper flexing, and the second upper flexing section;
and
contacting the outer surface of the pipe with a landing pad affixed to an end of
each adjustment rod positioned toward the longitudinal axis of the pipe.
14. The method of claim 12 further comprising:
positioning the first sensor mounting arm parallel to the second sensor mounting
arm when the clamp is in an unstressed condition.
15. The method of claim 12 further comprising:
positioning a second strain sensor with a first end in a second receptacle of the
first sensor mounting arm and a second end of the second strain sensor in a second
receptacle of the second sensor mounting arm.
16. The method of claim 12 further including connecting a rigid linking plate to a
distal end of the first mounting arm and to a distal end of the second mounting arm.
17. The method of claim 12, wherein the pivot pin includes a compressible coating
thereby providing additional flexibility to the mechanical clamp.
18. The mounting system of claim 13, wherein each of the landing pads include a
compression pad having at least one layer of vibration and acoustic noise absorbing
material affixed to each of the landing pads; and
the method further includes dampening vibration and acoustic noise from the
pipe.
19. A system for mounting strain gauges on a tubular pipe, the system comprising:
a first mounting block having a proximal first surface positionable adjacent to a
first portion of an outer surface of a wall of the pipe, said first mounting block having a
distal mounting surface;
a second mounting block having a proximal first surface positionable adjacent to
second portion of an outer surface of a wall of the pipe, said second portion of the pipe
wall being displaced from the first portion, said second mounting block having a distal
mounting surface;
a first sensor mounting arm connected to the distal mounting surface of the first
mounting block, said sensor mounting arm including at least one receptacle configured
to receive and retain a first end of a stem rod;
a second sensor mounting arm connected to the distal mounting surface of the
second mounting block, said sensor mounting arm including at least one receptacle
configured to receive and retain a second end of the stem rod; and
wherein the stem rod includes a first longitudinal receptacle in an outer surface of
the rod, said first receptacle configured to receive and retain a first strain gauge.
20. The mechanical mounting system of claim 19, the stem rod having a first cross
sectional area at a central portion of the first longitudinal receptacle and wherein the
stem rod includes a second longitudinal receptacle in the outer surface of the stem rod,
said first receptacle configured to receive and retain a second strain gauge, said stem
rod having a second cross sectional area at a central portion of the second longitudinal
receptacle.
21. The mounting system of claim 19, wherein when the mechanical clamp is
assembled in a predetermined strain condition the first sensor mounting arm is generally
parallel to the second sensor mounting arm and the stem rod is mounted perpendicular
to a longitudinal axis of each mounting arm.
22. The mounting system of claim 19 further comprising:
a first magnet received in a receptacle of the first surface of the first mounting
block, said magnet having at least a first surface positionable adjacent to a first portion
of the outer surface of the wall of the pipe and at least a second surface positionable
adjacent to the first mounting block; and
a second magnet received in a receptacle of the first surface of the second
mounting block, said magnet having at least a first surface positionable adjacent to a
second portion of the outer surface of the wall of the pipe and at least a second surface
positionable adjacent to the second mounting block.
23. The mounting system of claim 19, wherein the strain gauge is a Fiber-Bragg
grating.
24. The mounting system of claim 19, wherein the strain gauge is a Fabry-Perot
interferometer.
25. The mounting system of claim 19 further including a tension adjustment
mechanism for the stem rod.
26. A method of mounting a strain gauge to a pipe comprising:
positioning a first mounting block having a proximal first surface adjacent to a
first portion of an outer surface of a wall of the pipe, said first mounting block having a
distal mounting surface;
positioning a second mounting block having a proximal first surface adjacent to
second portion of an outer surface of a wall of the pipe, said second portion of the pipe
wall being displaced from the first portion, said second mounting block having a distal
mounting surface;
connecting a first sensor mounting arm to the distal mounting surface of the first
mounting block;
connecting a second sensor mounting arm to the distal mounting surface of the
second mounting block;
connecting a first end of a stem rod to the first sensor mounting arm;
connecting a second end of a stem rod to the second sensor mounting arm;
positioning a first strain gauge in a first longitudinal receptacle in an outer surface
of the stem rod, said stem rod having a first cross sectional area at a central portion of
the first longitudinal receptacle.
27. The method of claim 26 further including adjusting the tension in the stem rod
prior to taking measurement with the strain gauges using a tension adjustment
mechanism on the stem rod.
28. The method of claim 26 further comprising: