U.S. patent application number 09/851511 was filed with the patent office on 2003-01-16 for acoustic sensor for pipeline deposition characterization and monitoring.
Invention is credited to Amin, Rajnikant M., Birchak, James R., Fleyfel, Fouad, Han, Wei, Kalpakci, Bayram, Shah, Vimal V., Storm, Bruce H. JR..
Application Number | 20030010125 09/851511 |
Document ID | / |
Family ID | 25310949 |
Filed Date | 2003-01-16 |
United States Patent
Application |
20030010125 |
Kind Code |
A1 |
Han, Wei ; et al. |
January 16, 2003 |
ACOUSTIC SENSOR FOR PIPELINE DEPOSITION CHARACTERIZATION AND
MONITORING
Abstract
A method and apparatus for analyzing a deposited layer on the
inner surface of a fluid container wall having inner and outer
surfaces are disclosed. One embodiment of the method comprises (a)
transmitting an acoustic signal from a transmitter at a first
distance from the outer surface of the wall; (b) receiving a first
received signal A, comprising a reflection from the wall outer
surface; (c) receiving a second received signal B, comprising a
reflection from the wall inner surface; (d) receiving a third
received signal C from the wall inner surface; (e) calculating a
coefficient R.sub.wp from A, B and C, and (f) calculating a
coefficient R.sub.pd from A, B and R.sub.wp and calculating the
acoustic impedance of the deposited layer Z.sub.d from R.sub.wp,
R.sub.pd, and Z.sub.w, where Z.sub.w is the acoustic impedance of
the material between the transmitter and the wall outer surface. A
preferred embodiment of the apparatus comprises a piezoelectric or
ferroelectric transducer having front and back faces; a backing
member acoustically coupled to said transducer back face and
impedance-matched to said transducer element, said backing member
having proximal and remote faces; and a delay material disposed
between said transducer front face and the wall outer surface.
Inventors: |
Han, Wei; (Missouri City,
TX) ; Shah, Vimal V.; (Houston, TX) ; Birchak,
James R.; (Spring, TX) ; Storm, Bruce H. JR.;
(Houston, TX) ; Amin, Rajnikant M.; (Houston,
TX) ; Kalpakci, Bayram; (The Woodlands, TX) ;
Fleyfel, Fouad; (Katy, TX) |
Correspondence
Address: |
CONLEY ROSE & TAYON, P.C.
P. O. BOX 3267
HOUSTON
TX
77253-3267
US
|
Family ID: |
25310949 |
Appl. No.: |
09/851511 |
Filed: |
May 8, 2001 |
Current U.S.
Class: |
73/627 |
Current CPC
Class: |
G01B 17/02 20130101;
G01N 29/2468 20130101; G01N 29/28 20130101; G01N 29/2437 20130101;
G01N 29/041 20130101; G01N 2291/02854 20130101; G01N 2291/0422
20130101; G01N 2291/0421 20130101; G01N 2291/2634 20130101 |
Class at
Publication: |
73/627 |
International
Class: |
G01N 029/00; G01N
029/04 |
Claims
What is claimed is:
1. A method for analyzing a deposited layer on the inner surface of
a fluid container wall having inner and outer surfaces, comprising:
(a) transmitting an acoustic signal from a transmitter at a first
distance from the outer surface of the wall; (b) receiving a first
received signal A, comprising a reflection from the wall outer
surface; (c) receiving a second received signal B, comprising a
reflection from the wall inner surface; (d) receiving a third
received signal C from the wall inner surface; (e) calculating a
coefficient R.sub.wp from A, B and C using the equation 8 R w p = A
C A C - B 2 (f) calculating a coefficient R.sub.pd from A, B and
R.sub.wp using the equation 9 R p d = B A R w p ( 1 - R wp 2 ) 2 L
p p where L.sub.p is the thickness of the wall and .alpha..sub.p
the attenuation of the wall; and (f) calculating the acoustic
impedance of the deposited layer Z.sub.d using the equation 10 Z d
= Z w 1 + R wp 1 - R wp 1 + R pd 1 - R pd ,where Z.sub.w is the
acoustic impedance of the material between the transmitter and the
wall outer surface.
2. The method according to claim 1, further including providing an
acoustic delay material between the transmitter and the wall outer
surface.
3. The method according to claim 1 wherein the acoustic impedance
of the deposited layer Z.sub.d calculated in step (f) is a
longitudinal impedance.
4. The method according to claim 1 wherein the acoustic impedance
of the deposited layer Z.sub.d calculated in step (f) is a shear
impedance.
5. The method according to claim 1, further including receiving a
fourth received signal from the deposit/fluid interface and using
said received signals to estimate the thickness of the deposited
layer.
6. The method according to claim 1 wherein the signal transmitted
in step (a) comprises a shear wave, further comprising transmitting
a second signal that comprises a compression wave.
7. A method for analyzing a deposited layer on the inner surface of
a fluid container wall having inner and outer surfaces, comprising:
(a) transmitting an acoustic signal from a transmitter at a first
distance from the outer surface of the wall using a transmitter
acoustically coupled to a backing, said backing including a first
end proximal to the transmitter and a second end remote from the
transmitter; (b) receiving a first received signal A, comprising a
reflection from the wall outer surface; (c) receiving a reference
signal A.sub.ref, comprising a reflection from the backing second
end; (d) receiving a second received signal B, comprising a
reflection from the wall inner surface; (e) calculating an
impedance for the wall material using the equation 11 Z p = 1 - | A
A ref | 1 + | A A ref | Z w ; a n d (f) calculating the acoustic
impedance of the deposited layer Z.sub.d using the equation 12 Z d
= 1 - ( Z w + Z p ) 2 4 Z w Z p | B A ref | 1 + ( Z w + Z p ) 2 4 Z
w Z p | B A ref | Z p .
8. The method according to claim 7 wherein the length of the
backing between the backing first end and the backing second end is
at least six times the total of the first distance from the outer
surface of the wall plus the wall thickness.
9. The method according to claim 7, further including providing an
acoustic delay material between the transmitter and the wall outer
surface.
10. The method according to claim 7, further including receiving a
third received signal from the deposit/fluid interface and using
said received signals to estimate the thickness of the deposited
layer.
11. A method for analyzing a deposited layer on the inner surface
of a fluid container wall having inner and outer surfaces,
comprising: (a) providing a first piezoelectric or ferroelectric
transducer having front and back faces and transmitting a shear
wave into said container wall from said first transducer; (b)
providing a second piezoelectric or ferroelectric transducer having
front and back faces and transmitting a compression wave into said
container wall from said second transducer;
12. The method according to claim 11, further providing a backing
member acoustically coupled to the back face of at least one of
said transducers, said backing member having proximal and remote
faces, said backing member having proximal and remote faces.
13. The method according to claim 11, further including providing a
delay material disposed between the front face of at least one of
said transducers and the wall outer surface.
14. The method according to claim 11, further including, for at
least one of said transmitted signals, the steps of (c) receiving a
first received signal A, comprising a reflection from the wall
outer surface; (d) receiving a reference signal A.sub.ref,
comprising a reflection having a known delay period; and (e)
receiving a second received signal B, comprising a reflection from
the wall inner surface.
15. The method according to claim 14, further including the steps
of: (f) calculating an impedance for the wall material using the
equation 13 Z p = 1 - | A A ref | 1 + | A A ref | Z w ; a n d (g)
calculating the acoustic impedance of the deposited layer Z.sub.d
using the equation 14 Z d = 1 - ( Z w + Z p ) 2 4 Z w Z p | B A ref
| 1 + ( Z w + Z p ) 2 4 Z w Z p | B A ref | Z p .
16. An acoustic device for measuring buildup on a container wall
having inner and outer surfaces, comprising: a piezoelectric or
ferroelectric transducer having front and back faces; a backing
member acoustically coupled to said transducer back face and
impedance-matched to said transducer element, said backing member
having proximal and remote faces; and a delay material disposed
between said transducer front face and the wall outer surface.
17. The device according to claim 16 wherein the device
characterizes the buildup based on frequency-dependent phase and
amplitude information in the reflected acoustic waves.
18. The device according to claim 16 wherein the distance between
the proximal and remote backing faces is at least six times the
distance between the transducer front face and the wall inner
surface.
19. An acoustic device for measuring buildup on a container wall
having inner and outer surfaces, comprising: a first piezoelectric
or ferroelectric transducer having front and back faces; and a
second piezoelectric or ferroelectric transducer having front and
back faces; one of said first and second transducers being capable
of generating shear waves in the container wall and the other of
said first and second transducers being capable of generating
compression waves in the container wall
20. The device according to claim 19, further including a backing
member acoustically coupled to the back face of one of said
transducers and impedance-matched to said transducer.
21. The device according to claim 19, further including a delay
material disposed between the front face of one of said transducers
and the wall outer surface.
22. The device according to claim 19 wherein said first transducer
is disposed between said second transducer and said container
wall.
23. The device according to claim 22, further including a backing
member acoustically coupled to the back face of said second
transducer and impedance-matched to said second transducer.
24. The device according to claim 22, further including a delay
material disposed between the front face of said first transducer
and the container wall.
25. The device according to claim 22, further including an
elastomeric material disposed between the front face of said first
transducer and the container wall.
26. The device according to claim 19 wherein the device
characterizes the buildup based on frequency-dependent phase and
amplitude information in the reflected acoustic waves.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
BACKGROUND OF THE INVENTION
[0003] As the current trend in offshore oil and gas production
advances into deeper waters, it is becoming increasingly necessary
for the industry to develop cost effective solutions for developing
fields in deep and/or remote waters.
[0004] A typical solution for such cases is to keep the production
facilities on a "host platform" and connect the deep-water well(s)
to the platform with pipelines and risers. The supporting equipment
for the subsea tree control, such as hydraulic and electric power
units, chemical injection pumps and tanks, and a control console,
are also housed on the host platform. The subsea tree control is
accomplished via long umbilical(s) consisting of electric
conductors, hydraulic lines and chemical injection lines laid
alongside the pipeline. In addition, two parallel pipelines are
necessary to accomplish the roundtrip pigging operations. The
distance between the well and the host platform is known as the
tieback distance. The cost and technical challenges of this type of
conventional tieback system increase as the tieback distance
increases, and to a lesser extent as the water depth increases. In
most cases, 20 miles represents the practical limit for the maximum
tieback distance with the conventional tieback system.
[0005] One limit on the length of subsea tiebacks conveying crude
petroleum arises from flow assurance problems. Solids such as
asphaltene and paraffin deposit on the inner walls of the tiebacks
and partially, and in some cases completely, block the flow. The
longer the tieback is, the greater the length of pipe that must be
inspected and kept free of deposits.
[0006] At present, non-intrusive sensors that can adequately detect
and characterize such deposits are not available. The present
solutions require use of very expensive alternative methods for
flow assurance, including twin flowlines (for round-trip pigging),
heat traced or insulated tiebacks. These alternative methods
operate by attempting to prevent the deposition of solids on the
flowline wall, and do not provide means for detecting the presence
of solids in the event that deposits occur. The lack of continuous
monitoring can result in undesirable shutdowns. For example, a
flowline has been kept clear by pigging at a certain frequency,
e.g. once per month, and the composition of the fluid in the
flowline changes so that deposits begin to form at a greater rate,
the line will become clogged and possible shut down because the
previously established pigging frequency is now insufficient.
[0007] Guided acoustic waves similar those described in U.S. Pat.
No. 5,892,162, have been used to detect corrosion in pipes based on
reflections from corroded regions. Corrosion and scaling has also
been detected in insulated pipelines on surface using guided waves
and literature regarding this has been published from Imperial
College, University of London.
[0008] Monitoring devices such as that described in U.S. Pat. No.
4,490,679 identify paraffin by monitoring change in the resistance
of an electromagnetic coil. The monitoring device requires access
to the fluid and is housed in a recess in the pipe. It is desired
to provide monitoring without disrupting the flow of fluid through
the line and without requiring direct contact with the fluid.
[0009] In U.S. Pat. No. 4,843,247, an optical asphaltene sensor is
described. This sensor determines the content of asphaltene in
heavy oils, based on the absorption spectra of asphaltene. The
invention uses visible light in the region 500 nm to 1000 nm and
thus requires at least optical access to the fluid. Furthermore, it
does not distinguish between deposited and suspended asphaltene
solids.
[0010] Similarly, ultrasonic longitudinal wave measurements have
been used to characterize fluids using reflectance methods, as in
U.S. Pat. No. 4,571,693. Shear reflectance has been used in prior
art to monitor casting processes as in U.S. Pat. No. 5,951,163,
detect viscosity as in U.S. Pat. No. 3,903,732, or density as in
U.S. Pat. No. 5,886,250 and to monitor the rheology of fluids.
[0011] Hence, it is desired to provide a system that can operate
over greater tieback distances without the cost and technical
disadvantages that heretofore have prevented increasing the tieback
distance. It is further desired to provide a method and apparatus
for detecting and characterizing deposits of asphaltene, paraffin
or hydrates on the inside wall of a pipeline. It is further desired
to provide a system that can be installed on a conventional
pipeline and does not impede the flow of fluid through the
pipeline. The desired system should be able to compensate for drift
in the response of its components and should be capable of
operating for a period of years without service or calibration.
SUMMARY OF THE INVENTION
[0012] The present invention provides a method and apparatus that
allows non-invasive monitoring of longer tieback distances without
the cost and technical disadvantages associated with previous
methods. The system of the present invention measures the acoustic
properties of deposits on the inner surface of the pipe wall. One
object of the invention is to detect, characterize and determine
the extent of deposition and thus enable remedial procedures.
[0013] The present system detects deposits or deposition of
asphaltene and paraffin on the inside wall of a pipeline without
impeding the flow of fluid through the pipeline. Furthermore, the
present system compensates for drift in the response of its
components and is therefore capable of operating for a period of
years without service or calibration.
[0014] In particular, the present system includes an acoustic
sensor that is capable of detecting and characterizing deposits of
paraffin, asphaltene or hydrates on the inner walls of pipes, thus
enabling timely intervention and flow assurance. In one embodiment,
the sensor detects and monitors deposition in a section of the
pipe. In another embodiment, multiple installations of the system
allow the location of depositions to be determined with a desired
degree of precision.
[0015] The present apparatus is capable of self-calibration and is
not affected by drifts in equipment response that may be caused by
variations in temperature or pressure or by the passage of time.
The present sensors distinguish between types of deposition
material based on the frequency and phase response.
[0016] In one embodiment, the present system is used to monitor and
characterize the deposition and build-up of materials such as
paraffin, asphaltene and hydrates in subsea tiebacks.
Alternatively, the present system can be permanently installed in a
borehole to monitor deposition therein. The present sensor can also
be used on surface pipelines to monitor deposition of solids in
cases where solids deposition may occur, such as multiphase
flow.
[0017] In a preferred embodiment, the sensor distinguishes the type
of deposition material based on the compression and shear impedance
as well as signal arrival times.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] For a more detailed understanding of the invention,
reference will be made to the accompanying Figures, wherein:
[0019] FIG. 1 is a cross-sectional view of an apparatus according
to a first embodiment of the present invention mounted on a
pipe;
[0020] FIG. 2 is a schematic diagram showing propagation and
reflection of an acoustic signal through the components of the
apparatus of FIG. 1;
[0021] FIG. 3 is a representation of the signals received as a
result of the reflections shown in FIG. 2; and
[0022] FIG. 4 is a cross-sectional view of an apparatus according
to an alternative embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] Two methods of measuring acoustic impedance of deposits
based on acoustic reflectance (longitudinal or shear) are disclosed
here. In the first method, deposition impedance is computed from
the amplitude of reflected acoustic signals arriving from a delay
wedge/pipe wall interface and the wall-deposition interface. The
other method additionally measures acoustic reflection from the
remote end of the transducer backing and uses the reflected
amplitude as a reference.
[0024] Transmitter-Receiver Arrangement
[0025] Referring initially to FIG. 1, a preferred embodiment of the
present transducer system includes a piezoelectric or ferroelectric
transducer block 10, the wall of the pipe 30, and a layer of
deposited solid or semi-solid material 35, as shown in FIG. 1.
Transducer block 10 preferably comprises an impedance matched
backing solid 12, piezoelectric or ferroelectric element (PZT) 14,
and a delay wedge 16, which is preferably impedance matched with
PZT 14. The outer end 13 of backing 12 is exposed to a fluid medium
(such as air or water), while the inner end 15 is fixed to the
outer face 17 of PZT 14. In one preferred embodiment, backing solid
12 is designed so that the distance between ends 13, 15 is great
enough to ensure that reflections from outer end 13 will not
overlap with the reflected signals from other interfaces, including
the wedge 16/pipe wall 30 interface, and the pipe wall 30/deposit
35 interface. The inner end 18 of PZT 14 is acoustically coupled to
delay wedge 16, which preferably has an acoustic impedance close to
the acoustic impedance of PZT 14. The function of wedge 16 is to
produce a reflection at the wedge-pipe wall interface, which helps
in characterizing the pipe wall, as discussed below. The delay
wedge 16 preferably comprises of titanium or alloys of titanium
with acoustic impedance close to the acoustic impedance of PZT
14
[0026] It is necessary to calibrate reflection coefficients in
order to accurately measure the impedance of the deposit 35
(longitudinal and/or shear). In particular, temperature and
material property variations that cause pipe wall impedance
variations must be compensated for. An implicit compensation method
is discussed in the following paragraphs.
[0027] Delay wedge 16 is preferably constructed of an elastic
material. Its temperature-dependent longitudinal and shear
impedance are known, e.g. from lab measurements. The deposited
materials 35 are typically visco-elastic in nature.
[0028] A clamp or retaining device 50 is used to maintain good
acoustic coupling between transducer block 10 and the pipe wall 30.
One or more Belleville springs 52 or other biasing means may be
positioned between clamp 50 and transducer block 10 to urge block
10 toward pipe 30. Clamp 50 may be held together with the pipe by a
threaded sleeve 54, wherein the end of the clamp 50 mates with the
rising section of sleeve 54. Sleeve 54 clamps circumferentially on
the outside of the pipe. Clamp 50 could be designed to allow
pressure balancing.
[0029] Referring now to FIGS. 2 and 3, PZT 14 emits an incident
acoustic signal P.sub.0. A portion of the signal P.sub.0 is
reflected back from each of the interfaces across which it travels.
Thus, PZT 14 measures several reflections from various interfaces.
These signals are labeled in FIGS. 2 and 3 as A--reflection from
the delay wedge 16/wall 30 interface, B--first reflection echo from
the wall 30/deposit 35 interface, and C second reflection from the
wall 30/deposit 35 interface. If Z.sub.w and Z.sub.p are the
(either longitudinal or shear) impedances of the wedge and wall,
respectively, the reflection coefficient of the wedge/wall
interface R.sub.wp can be written as 1 R w p = Z p - Z w Z p + Z
w
[0030] R.sub.wp can also be written in terms of the three reflected
signals A, B and C, as 2 R w p = A C A C - B 2
[0031] The impedance Z.sub.w of delay wedge 16 is known and depends
on the selection of the wedge material. Hence, the coefficient
R.sub.wp can be determined from A, B and C and used to compute
Z.sub.p.
[0032] The reflection coefficient of the wall 30/deposit 35
interface R.sub.pd, can be given by 3 R p d = B A R w p ( 1 - R wp
2 ) 2 L p p
[0033] where, L.sub.p and .alpha..sub.p are the thickness and
attenuation of the pipe wall, respectively. Once R.sub.wp and
R.sub.pd are determined, the acoustic impedance of the deposited
layer 35, Z.sub.d is preferably determined by 4 Z d = Z w 1 + R wp
1 - R wp 1 + R pd 1 - R pd
[0034] where, Z.sub.w is the impedance (longitudinal or shear) of
delay wedge 16.
[0035] In this manner, the longitudinal and/or shear impedance of
the deposited material (e.g. wax) can be determined from the
measurable amplitude of the reflected delay wedge 16/wall 30 echo A
and the amplitudes of the first and second reflected echoes B and
C.
[0036] One advantage provided by the present invention is that, in
determining the acoustic impedance of deposition, it avoids the
need to use reference signals that may be generated by acoustic
delay lines with notches, slots and holes as reflectors such as are
commonly used in the prior art, such as U.S. Pat. No. 4,571,693.
Notches and slots introduce undesirable non-uniform scattering of
the acoustic waves. In addition, the notched or slotted delay lines
used in the art require careful handling during construction
because of their reduced strength.
[0037] In an alternative approach, reflected acoustic waves from
the outer end 13 of backing 12 are used as a reference signal
A.sub.ref (FIG. 2). This method is useful in the circumstances
where the second wall/deposit reverberation signals are either weak
or overlap with the first wall/deposit echo. In this approach,
backing solid 12 is preferably relatively long. For instance, the
length of backing solid 12, L.sub.b, preferably equals at least six
times the total length of delay wedge 16 L.sub.w plus the wall
thickness L.sub.p, i.e. L.sub.b.gtoreq.6(L.sub.w+L.- sub.p). This
enables the reference signal to arrive later compared to
reflections from other interfaces. The far side of the backing may
be exposed to an unchanging media, preferably air, in order to
maintain a constant reflection coefficient. The pipe wall impedance
Z.sub.p is given as 5 Z p = 1 - | A A ref | 1 + | A A ref | Z w
[0038] where A is the reflection from the delay wedge/wall
interface, and A.sub.ref is the reference signal from the outer
face of the backing solid. Then, deposition impedance can be
calculated from the absolute values of B and A.sub.ref, for small
attenuation of pipe wall material, as 6 Z d = 1 - ( Z w + Z p ) 2 4
Z w Z p | B A ref | 1 + ( Z w + Z p ) 2 4 Z w Z p | B A ref | Z
p
[0039] where B is the first reflection echo from the wall
30/deposit 35 interface,
[0040] ). Therefore, from the above two approaches, when a
longitudinal-wave or a shear-wave transducer is used, longitudinal
or shear impedance of the deposition, i.e.,
density.times.longitudinal (or shear) speed of sound, can be
measured. Deposition material (as paraffin, asphaltene, hydrates)
are usually regarded as visco-elastic material with both bulk
module and shear module. The shear impedance consists of a real
part and an imaginary part. The real part (density.times.shear
speed of sound) can be determined from the above approaches. The
imaginary part of the shear impedance, which is a product of the
viscosity and density of the deposited material and the wave
frequency, can be determined separately from measurement of the
phase shift of the reflection coefficient due 7 R i = Z p s - Z p s
+
[0041] where,
[0042] to the deposit as follows; .phi. is the phase difference
between the the incident and reflected signals,
[0043] R is the absolute reflection coefficient,
[0044] Z.sub.ps is the shear impedance of the pipe wall
[0045] These measurements provide the acoustic longitudinal and
shear impedance, and phase shift of the acoustic waves due to
visco-elasticity of the deposition. This information is combined to
characterize the type of deposit based on the measured longitudinal
(and shear) impedance of the deposit.
[0046] The present invention provides several advantages over prior
art systems. These include but are not limited to:
[0047] non-invasive and non-intrusive detection, identification,
characterization and monitoring of deposits in real-time.
[0048] low assurance monitoring and assessment of intervention
based on deposit characteristics.
[0049] quantitative monitoring of deposits in critical areas.
[0050] compensation for variation in signal amplitude over a
prolonged period of time (signal drift).
[0051] potential for use with existing tubing (retrofitting).
[0052] In a preferred embodiment, a primary application of the
present system is to monitor and characterize deposition and
build-up of materials such as paraffin, asphaltene, hydrates and
infiltrated sand in subsea tiebacks. The present system can also be
used to advantage in smart wells, where it is permanently installed
in a borehole and interfaced with a microprocessor to monitor
deposition. This sensor can also be used on surface pipelines to
monitor deposition of solids in multiphase flow.
[0053] Compression acoustic impedance is a function of the layer
density and speed of sound. Shear acoustic impedance is a function
layer density and viscosity. The phase of the acoustic reflections
depends on the damping properties (viscosity in oil and
visco-elasticity in asphaltene, paraffin, etc.) of the deposit.
Thus, based on the effect of the deposition layer on the
compression and shear wave reflectance, an inverse solution
calculates the deposition layer properties and identifies
composition.
[0054] In an alternative embodiment shown in FIG. 4, the acoustic
sensor comprises both a compression-piezoelectric element 24 and a
shear-piezoelectric element 34. A pressure clamp like clamp 50 of
FIG. 1 is preferably used, but is not shown in FIG. 4.
Piezoelectric elements 24, 34 are preferably bonded together and
have a common-ground electrode. The relative positions of the shear
and compression elements can be reversed from those shown in the
Figure. The back of the upper element is preferably coupled to
impedance-matched backing 12. An elastomer 26 preferably
acoustically couples the element to the pipe wall. This
construction is advantageous because the probe interrogates the
same layer of deposition with both compression and shear waves.
[0055] The following are some preferred embodiments of the
invention:
[0056] an acoustic transducer that can be clamped on the exterior
of existing pipe, consisting of impedance-matched backing solid, a
piezoelectric or ferroelectric transducer element, and a delay
wedge. The far end of the backing is exposed to a fluid medium,
while the near end is fixed to the frontal face of the
piezoelectric element. The transducer system is capable of
compensating for the pipe wall material property variations by
measuring multiple reflections from the pipe wall and far end of
the backing solid.
[0057] an acoustic device capable of generating and detecting
compression and/or shear acoustic waves, which reflect from several
reflecting interfaces including the interface between the pipe wall
and deposits on the inner walls of pipes that are transporting
crude petroleum.
[0058] an active acoustic sensor capable of characterizing the type
of deposition on the inner wall of pipes, based on
frequency-dependent phase and amplitude information in the
reflected acoustic waves.
[0059] an active acoustic sensor capable of estimating thickness of
the deposition and thus monitoring the layer buildup, based on the
arrival time of the reflected wave from the deposit/fluid
interface.
[0060] an acoustic sensor capable of monitoring deposition layer
buildup and triggering alarms for remedial action in case the
deposition thickness exceeds a predetermined thickness.
[0061] an acoustic wave sensor that is capable of compensating for
variation in signals over a period of time by using reflections
from the far end of the backing material as a reference.
[0062] While preferred embodiments of the present invention have
been disclosed and discussed herein, it will be understood that
various modifications can be made to these embodiments without
departing from the scope of the invention. For example, the
principles described herein can be used to determine the presence
and nature of buildup or deposits on walls other than pipeline
walls, including but not limited to container walls. The present
apparatus can be used to detect buildup or deposits on inner or
outer walls, depending on how the apparatus is used. The dimensions
and/or relative proportions of the components of the apparatus can
be modified, as can the number and frequency of signals that are
emitted, detected and/or analyzed by the apparatus. In the claims
that follow, any recitation of steps is not intended as a
requirement that the steps be performed sequentially, or that one
step be completed before another step is begun, unless explicitly
so stated.
* * * * *