IRNDT
Patent
|
Ultrasonic Tubulars Inspection Device |
|
| Inventor: |
Girndt |
| Date Issued: |
November 13, 2007 |
| Application: |
10/971,860 |
| Filed: |
October 22, 2004 |
| Inventors: |
Girndt; Richard (Spring, TX)
|
| Assignee: |
|
| Primary Examiner: |
Chapman; John E. |
| Assistant Examiner: |
|
| Attorney Or Agent: |
Fulbright & Jaworski LLP |
| U.S. Class: |
73/622; 310/336; 73/628 |
| Field Of Search: |
73/622; 73/628; 310/336 |
| International Class: |
G01N 29/24 |
| U.S Patent Documents: |
4020688; 4106347; 4195530; 4217782; 4319490; 4404853; 4487072; 4718277; 5313837; 5600069 |
| Foreign Patent Documents: |
|
| Other References: |
Ultrasonic Testing of Tube-Phased Array Technique-No Mechanical Rotation, Sep. 26, 2003###. cited by other.
Piezo compsite Transducers-a Milestone for Ultrasonic Testing; G. Splitt, NDT.net, Jul. 1996, vol. 1, No. 07. cited by other.
First
Results of Composite Transducers Used in Automatic Rotating Ultrasonic
Inspection Units, Dr.-Eng. Roman Koch, NDT.net-Oct. 2002, vol. 2, No.
10. cited by other.
Improvements of Ultrasonic Inspections Through
the Use of Piezo-Composite Transducers, Gerard Fleury, Christian
Gondard-6th European Conference on Non Destructive Testing, May 1995.
cited by other.
Use of Flexible Ultrasonic Arrays in Inspection; Jocelyn Langlois, NDT.net, Mar. 1999, vol. 4, No. 3. cited by other. |
|
| Abstract: |
A system, method, and apparatus for ultrasonic detection of
flaws or defects in oil field tubulars utilizing composite
transducers. An array of composite transducers are utilized to
detect anomalies in the tubulars, such as transverse, wall or
longitudinal defects. The use of the composite transducers allow for
a greater inspection area over traditional transducers thereby
reducing the number of channels needed for inspection of the
tubulars. |
| Claim: |
What is claimed is:
1. A method for ultrasonic
inspection of tubulars, said method comprising: providing a first
circular array of composite transducers, said transducers having a
proximate curved surface; passing a tubular past said first array, said
tubular having an outer peripheral surface, wherein said outer
peripheral surface has a radii of curvature, and said proximate curved
surface has a radii of curvature greater than the radii of curvature of
the outer peripheral surface; and inspecting for abnormalities in the
tubular utilizing said transducers.
2. The method of claim 1,
wherein the step of passing includes moving the tubular in a
longitudinal direction past said first array without rotating the
tubular in a circumferential direction.
3. The method of claim 1, wherein the step of providing includes maintaining said first array in a stationary position.
4.
The method of claim 1, wherein said tubular has a wall thickness, and
the inspecting step includes determining abnormalities in the wall
thickness.
5. The method of claim 1, wherein the inspecting step includes determining abnormalities of a longitudinal flaw type.
6. The method of claim 1, wherein the inspecting step includes determining abnormalities of a transverse flaw type.
7.
The method of claim 1, wherein the inspecting step includes utilizing
shear waves for determining abnormalities of a longitudinal flaw type
and transverse flaw type.
8. The method of claim 1, wherein said transducers are each a length of equal to or greater than 2 inches.
9. The method of claim 1, wherein said transducers are each a length of between 0.25 inches and 2 inches.
10. The method of claim 1, wherein said passing step includes maintaining the proximate curved surface of each transducer equi-distant from said outer peripheral surface of the tubular.
11. The method of claim 1, wherein the pipe has a diameter ranging from equal to or greater than 2 3/8 inches.
12. The method of claim 1, wherein the first array is adapted to detect variations in wall thickness.
13.
The method of claim 1, further comprising the step of providing a
phase array longitudinal inspection system having individual phased
array channels and with multiple elements.
14. The method of claim 1, wherein the first array each include four or more transducers.
15.
The method of claim 1, further comprising: providing a second and
third array of composite transducers, said transducers having a
proximate curved surface; wherein relative to a central longitudinal
axis of the tubular, said transducers of the second and third array are
angled 19 degrees in water to produce a 45 degree refracted angle.
16. The method of claim 15, wherein the inspecting step includes determining abnormalities of a transverse flaw type.
17. The method of claim 15, wherein the second and third array each include four or more transducers.
18.
The method of claim 15, further comprising: providing a fourth and
fifth array of composite transducers, said transducers of the fourth and
fifth array having a proximate curved surface, the fourth and fifth
array adapted to inspect for longitudinal flaws.
19. A system for
ultrasonic inspection of a tubular, said system comprising: a first
circular array of composite transducers, said transducers having a
proximate curved surface with a radii of curvature greater than the
radii of curvature of the outer peripheral surface of said tubular,
wherein said circular array is adapted for inspecting for abnormalities
in the tubular utilizing said transducers.
20. The system of claim 19, wherein the curved transducers are piezo composite transducers.
21.
The system of claim 19, further comprising a phase array longitudinal
inspection system having individual phase array channels to form a
curve.
22. The system of claim 19, further comprising a second
and third array of composite transducers, said transducers having a
proximate curved surface.
23. The system of claim 22, wherein
said transducers of the second and third array are angled 19 degrees in
water to produce a 45 degree refracted angle.
24. The system of
claim 22, wherein the second and third array are adapted to inspect for
abnormalities of the transverse flaw type.
25. The system of claim 22, wherein the second and third array each includes four or more transducers.
26.
The system of claim 22, further comprising: a fourth and fifth array
of composite transducers, said transducers of the fourth and fifth array
having a proximate curved surface, the fourth and fifth array adapted
to inspect for longitudinal flaws.
27. The system of claim 26, wherein the fourth and fifth array each includes four or more transducers.
28. The system of claim 19, wherein the first array each includes four or more transducers.
29. The system of any one of claims 19, wherein the first array is adapted to detect variations in wall thickness. |
| Description: |
TECHNICAL FIELD
The present invention relates to a
system, method and apparatus for the detection of flaws or defects in
oil field tubulars. More particularly, the present invention relates to
a system, method, and apparatus for ultrasonic detection of flaws
or defects in oil field tubulars utilizing composite transducers.
BACKGROUND OF THE INVENTION
Current
tube inspection technology utilizing ultrasonic technology consists of
units of three distinct types: 1) rotating head, 2) tube rotates in
place, head traverses the length of the tube, and 3) helical
advance--canted roller scheme. All three of these methods are restricted
by certain constants inherent to the use of ultrasound as a testing
medium on all types of products, equipment, and structures.
Few
industries require ultrasonic inspection at higher speeds, with greater
accuracy than in the inspection of oilfield tubulars such as tubing,
casing, and drill pipe. The required speeds and the constant quest to
increase the speeds are driven by competitive pressure, steel mill
production rates, and the desire to lower manufacturing costs which in
turn increase profits.
An article titled "Ultrasonic Testing of
Tube--Phased Array Technique" co-sponsored by NDT Systems of France and
Sandvik Steel AB of Sweden, goes into extensive detail regarding the
inherent problems and shortcomings of current tube testing technology as
well as the merits of encircling a tubular product with ultrasonic
probes. The co-authors have identified the fairly new technology of
phased array ultrasound as the best, cost effective approach to
accomplish full body ultrasonic inspection without the use of rotating
ultrasonic probes.
In fact, commercially available, non-rotating,
phased array tube testing systems are currently operating in production
environments at pipe manufacturing facilities. Phased array technology
is widely viewed by the next technological leap in the tube testing
industry.
It is important to note that the aforementioned
reference, published in 1996, has a defined set of "application fields,"
but it can be seen that the focus for the end use of the proposed
development is the nuclear field, where pipe diameters requiring critical
NDT inspections tend to be much smaller than of the most commonly
inspected products in the Oil Country Tubular Goods (OCTG) field, which
commonly exceed 40 feet in length and whose diameters range from 2 3/8''
through 20'' and beyond. The reference comments on the known
competition in 1996, in which "everybody is working according to
conventional technologies: this means single element probes, rotating
mechanically around the tube with very complex and expensive systems."
The reference also comments on a specific company called "Nukem." This
company is known to specialize in the inspection of smaller diameter
tubes at high speeds. Indeed, it can be reasoned that future
development is focused on using the costly phased array method to
ultrasonically inspect tubular products.
In addition to the
rotating probe approach, also outlined herein are the helical advance
conveyor system, the overhead gantry approach, and now the introduction
of phased array transducers encircling the pipe as commonly known and
accepted approaches to OCTG inspection. It should be noted that these
mechanical or technological approaches to ultrasonic tube inspection
apply not only to the oil industry, but wherever a cylindrical object
may be considered for ultrasonic NDT.
What is unique to the
ultrasonic inspection of OCTG is the large surface area needing
inspection, coupled with the need for high production rates, which in
turn require greater and greater numbers of ultrasonic channels to
achieve these goals. The article "Ultrasonic Testing of Tube--Phased
Array Technique" describes an electronics data management system to
handle between 1000 and 2000 individual ultrasonic transducers.
Currently
marketed phased array inspection systems for OCTG, require far more
than the contemplated one to two thousand channels, if the systems are
to comply with American Petroleum Institute (API) or end user customer
specifications for casing and tubing inspection, that require at a
minimum, inspection for longitudinal, transverse, and wall thickness
abnormalities or flaws. In fact, phased array transducers, covering
less than two inches of longitudinal or transverse surface area,
can contain up to 256 individual elements and individual channels.
To
achieve axial inspection of tubulars without rotation of the tube or
test transducers, by definition, the ultrasonic probes must encircle the
pipe as contemplated and in use in current phased array systems. Also
for minimum inspection requirements acceptable on OCTG, that inspection
coverage may require wall thickness measurement as well as transverse
and longitudinal flaw inspection. Furthermore, the inspection for
longitudinal and transversely oriented flaws, using ultrasonic
shear waves, should be conducted from both the leading and trailing sides
of a transversely oriented flaw and the counter and counter-clockwise
sides of a longitudinal flaw.
Many advances in OCTG ultrasonic
inspection have taken place since the first commercialization of the
technology in the mid seventies. Now computer controlled digital
electronics components allow for higher pulse repetition rates,
greater numbers of channels, and wide latitude in the collection and
dissemination of the resultant data. Further advances have been made in
the manufacture of ultrasonic transducers with the most common types
being made of quartz or ceramic materials as outlined and identified in
U.S. Pat. No. 4,404,853 to Livingston.
More recently, much
research has been done with piezo composite materials for the manufacture
of ultrasonic transducers. In the July 1996 Article "Piezo composite
Transducers--A Milestone for Ultrasonic Testing" by Dr. Gerald Splitt,
numerous advantages realized through the use of composite transducers are
discussed, including lower signal to noise ratio, high acoustic
efficiency, low acoustic impedance, and lower amplifier gain among
others. This article is. incorporated by reference herein for all
purposes. Of greater importance to the present invention has to do with
the method of manufacturing composite sheets that are in turn finished
to final transducer element characteristics. Notably, this method
described makes it possible to fabricate piezo composite plates with
dimensions of 50.times.50 mm square or bigger, which are used to produce
multiple transducers of smaller size by known methods as mechanical or
laser cutting or dicing. Also of note is that piezo composite can be bent
into a cylindrical or spherical shape. This allows one to build line
or point focus transducers without the need for an additional lens in
front of a crystal. The reference further comments that for arrays and
paintbrush probes the construction with piezo composite transducers
becomes substantially easier as here only a light backing is needed to
produce high resolution probes.
Those familiar with automated
ultrasonic testing will recognize the terms line focus, point focus,
arrays, and paintbrush probes as they relate to ultrasonic transducers,
and will further recognize the difference between these commonly
known probe types and the curved piezo composite probes outlined and used
in the proposed invention.
An additional technical paper of note
is "First Results Of Composite Transducers Used in Automatic Rotating
Ultrasonic Inspection Units," authored by Dr Roman Koch and presented in
June 2002. This paper goes into much detail regarding actual field
testing of composite transducers in automated tube testing machines,
specifically the rotating probe method mentioned previously. The
article speaks to the aforementioned advantages of piezo composite probes
over conventional transducer elements but is of importance in this case
as it relates directly to tube testing. The development of
piezo composite materials for ultrasonic transducers in the middle of the
nineties first for the medical probes and then for the standard contact
probes gave us the change also to optimize the probes of automatic
ultrasonic testing machines to improve the defect sensitivity and
resolution. This statement confirms the history of composite probes as
well as their short period of use in industrial tube
testing applications. The paper goes on to explain in detail the
optimization of the sound field and reduction of the lens losses when
curving the composite material itself. Again, as in previously
referenced articles, the curving addressed is for the sole purpose of
focusing the sound beam by curving the composite material in order to
improve on inherent shortcomings of using a lens to perform the focusing
function. Also of note is the statement that in automated ultrasonic
testing systems that in such units often array probes are used where the
crystal of the probe is divided in several individual elements, which
are connected to individual electronic evaluation channels, to increase
testing speed. The use of transducers in combination to
increase coverage and speed will be discussed later in detail to point
out the advantages of the present inventions improvement over current
techniques as well as to draw attention to the uniqueness of the present
invention.
BRIEF SUMMARY OF THE INVENTION
The present
invention relates to a system, method and apparatus for the detection of
flaws or defects in oil field tubulars. More particularly, the present
invention relates to a system, method, and apparatus for ultrasonic
detection of flaws or defects in oil field tubulars utilizing curved
composite transducers.
A system, method, and apparatus for
ultrasonic detection of flaws or defects in oil field tubulars utilizing
curved composite transducers. An array of curved composite transducers
are utilized to detect anomalies in the tubulars, such as transverse,
wall or longitudinal defects. The use of the composite transducers
allow for a greater inspection area over traditional transducers thereby
reducing the number of channels needed for inspection of the tubulars.
The
scope of the present invention involves using the large sheets of
composite material mentioned in the referenced article "Piezo composite
Transducers--A Milestone for Ultrasonic Testing," not to produce
numerous small individual composite transducers, curved to replace a
conventional focusing lens, but to produce much larger probes, up to
three inches and above, where the entire large single element is curved
to a set radius as opposed to the much documented practice of curving
smaller elements for focusing purposes. Unlike conventional transducer
piezoelectric materials, the new composites can be shaped over a large
area while still maintaining the effective beam properties required to
insure 100% coverage, while maintaining sensitivity to the detection of
small flaws as is required in OCTG inspection. These properties are
desired for the present invention: a) uniform beam characteristics, b)
equal sensitivity over the entire face of the composite probe, c) the
ability to produce transducers with a smaller radius than previously
possible, and d) the ability to curve a large sheet of composite
material to make a single element probe with unique properties critical
to the current invention as opposed to the common practice of curving
numerous smaller elements and using them in an array to provide coverage
and speed in tube inspection.
The present invention utilizes
probes or transducers that work in all three of the previously defined
defect detection minimum requirements, namely longitudinal, transverse,
and wall thickness measurement. The method and advantages of each
type of inspection is discussed in detail in the following text and
drawings.
In one aspect of the invention there is a method for
ultrasonic inspection of tubulars. The method includes providing a
first circular array of composite transducers, said transducers having a
proximate curved surface; passing a tubular past said first array, said
tubular having an outer peripheral surface; and inspecting for
abnormalities in the tubular utilizing said transducers. The step of
passing includes moving the tubular in a longitudinal direction past
said first array without rotating the tubular in a circumferential
direction. The step of providing includes maintaining said first array
in a stationary position.
The inspecting step may include
determining abnormalities of a longitudinal flaw type, determining
abnormalities of a transverse flaw type, and/or determining
abnormalities in the wall thickness.
The inspecting step may
include utilizing shear waves for determining abnormalities of a
longitudinal flaw type and transverse flaw type.
The transducers
may be of various radii and length. For example, the transducers may
each be a length of greater than 2 inches. Additionally, the
transducers are each a length of between 0.25 inches and 2 inches. The
transducers may be sizedappropriately for the particular OD of the
tubular being inspected.
In one aspect of the method, the passing
step includes maintaining the proximate curved surface of each
transducer equidistant from said outer peripheral surface of the
tubular.
In another aspect of the method, the outer peripheral
surface of the tubular has a radii of curvature, and said proximate
curved surface of the transducer has a radii of curvature greater than
the radii of curvature of the outer peripheral surface. The proximate
curved surface is the surface of the transducer directed at the tubular
during ultrasonic inspection.
In another aspect of the invention,
the method includes the step of providing a second and third array of
composite transducers, said transducers having a proximate curved
surface. Relative to a central longitudinal axis of the tubular,
the transducers of the second and third array are angled 19 degrees in
water to produce a 45 degree refracted angle. The inspecting step
includes determining abnormalities of a transverse flaw type.
In
one embodiment, the second and third array each includes eight
transducers. Different number of composite transducers may be utilized.
In
one aspect of the invention, the tubular (or pipe) has a diameter
ranging equal to or greater than about 2 3/8 inches. Although, the
diameter of the inspected pipe is not limited to that range, the
inventive system and method allow for inspection of larger diameter pipe
with fewer channels.
In one aspect of the invention there is the
step of providing a phased array longitudinal inspection system having
individual phased array channels aligned to form a radius.
In
another aspect of the invention, there is the step of providing a fourth
and fifth array of composite transducers. The transducers of the
fourth and fifth array having a proximate curved surface, the fourth and
fifth array adapted to inspect for longitudinal flaws.
The
invention also includes an improved system for ultrasonic inspection of
tubulars. In one embodiment of the inventive system, there is a first
circular array of composite transducers. The transducers have a
proximate curved surface and the circular array is adapted for inspecting
for abnormalities in a tubular utilizing said transducers.
In
another aspect of the system, the system. includes a phased array
longitudinal inspection system having individual phased array channels
with multiple elements.
In another aspect of the system, the
system includes a second and third array of composite transducers. The
transducers have a proximate curved surface that is angled toward a
tubular being inspected. The second and third array are angled
19degrees in water to produce a 45 degree refracted angle. The second
and third array are adapted to inspect for abnormalities of the
transverse flaw type.
The system include a fourth and fifth array
of composite transducers. The transducers of the fourth and fifth
array having a proximate curved surface adapted to inspect for
longitudinal flaws.
In one aspect of the invention, the first array is adapted to inspect for variations in wall thickness.
The
method and system of the present invention, may utilize varying length
and radii for inspection of tubulars. The tubulars include oil field
tubulars such as drill pipe, but may also include other types of
tubulars for inspection. The number of channels needed to inspect
tubulars is reduced over prior art inspection systems because of the
ability of the composite transducer to provide a much larger inspection
area.
The transducers may be maintained at a fixed position while
maintaining 100% coverage on increasingly smaller diameters of tubulars
thereby increasing the water path to the surface of the tubular with no
mechanical change over required.
The foregoing has outlined
rather broadly the features and technical advantages of the present
invention in order that the detailed description of the invention that
follows may be better understood. Additional features. and advantages
of the invention is described hereinafter which form the subject of the
claims of the invention. It should be appreciated that the conception
and specific embodiment disclosed may be readily utilized as a basis for
modifying or designing other structures for carrying out the same
purposes of the present invention. It should also be realized that such
equivalent constructions do not depart from the invention as set forth
in the appended claims. The novel features which are believed to be
characteristic of the invention, both as to its organization and method
of operation, together with further objects and advantages is better
understood from the following description when considered in connection
with the accompanying figures. It is to be expressly understood,
however, that each of the figures is provided for the purpose of
illustration and description only and is not intended as a definition of
the limits of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
For
a more complete understanding of the present invention, reference is
now made to the following descriptions taken in conjunction with the
accompanying drawing, in which:
FIG. 1 is a drawing illustrating
problems associated with using a long conventional transducer element
for taking ultrasonic wall thickness measurements;
FIG. 2 is a
drawing illustrating how to overcome the restrictions of using a large
flat element for wall thickness measurements by using multiple
individual elements, or arrays, arranged in a curved case equidistant
from the curved surface;
FIG. 3 is a drawing illustrating an embodiment of the use of curved composite probes contemplated in the present invention;
FIG.
4 is a drawing illustrating the current methodology of using multiple
transducers in tandem, as a collection of overlapping effective beams;
FIG.
5 is a drawing illustrating a problem common to inspection for
transverse flaws from an ease and consistency of detection perspective;
FIG.
6 is a drawing illustrating that during transverse flaw inspection when
moving a transducer closer or further from the surface of the part
being inspected does not alter the incident inspection angle;
FIG. 7 is a drawing illustrating a multitude of transducer elements used in tandem in an array;
FIG.
8 is a drawing illustrating a sensitivity to change of the longitudinal
inspection transducer before drastically altering the desired incident
and refracted angles;
FIG. 9 is a drawing illustrating an
embodiment of a curved composite transducer can be developed for a range
of tubular diameters;
FIG. 10, is a drawing illustrating a smaller incident angle change over the prior art;
FIG.
11 is a drawing illustrating full 100% coverage of a tubular with a
13.325'' diameter can be obtained using only thirteen ultrasonic
channels and transducers;
FIG. 12 is a drawing illustrating the
use of prior art conventional technologies on tubular. with a diameter
of 13.325'' assuming an effective beam width of 0.500'';
FIGS. 13A-13E are drawings illustrating the use of five sets of transducers utilized in the current invention;
FIG. 14 is a drawing illustrating an embodiment of the present invention showing transducer beam coverage;
FIG. 15 is a drawing illustrating an embodiment of the present invention; and
FIG. 16 is a drawing illustrating a phased array transducer.
DETAILED DESCRIPTION OF THE INVENTION
As
used herein, the term "a" or "an" may mean one or more. As used herein
in the claim(s), when used in conjunction with the word "comprising",
the words "a" or "an" may mean one or more than one. As used herein,
"another" may mean at least a second or more.
As used herein, the
term "surface speed" means the actual speed of the tubular surface as it
passes the face of an ultrasonic transducer. Expressed in inches per
second (ips).
As used herein, the term "pulse repetition rate"
means the number of times per second an ultrasonic transducer is
electronically pulsed, resulting in. a sound wave of definable
parameters expressed in kilohertz (e.g. 2400 pulses per
second=2.4kilohertz).
As used. herein, the term "pulse gap"
means the distance between successive "pulses" of a transducer on the
surface of the tubular being inspected. Calculated by dividing the
surface speed in inches per second by the pulse repetition expressed in
thousands (e.g. 2.4 Khz-2400).
As used herein, the term
"effective beam" means the usable portion of the face of the ultrasonic
transducer expressed in thousandths (i.e. transducer crystal 0.500''
times 70% effective beam width=0.350'').
As used herein, the term "pipe diameter" means the outside or external diameter of the tubular being inspected.
As
used herein, the term "helical advance" means the distance an oilfield
tubular advances, expressed in inches, relative to a fixed set of
ultrasonic transducers, for each rotation of the tube or ultrasonic
head.
As used herein, the term "transducers per array" means the
number of individual transducer elements, used in conjunction as a sum
of individual effective beams, to form an area of 100% coverage at the
surface of the tubular being tested.
As used herein, the term
"tube length" means the overall axial length, from the leading to the
trailing edge of the tubular being inspected expressed in feet.
As
used herein, the term "cost per ultrasonic channel" means the average
cost per channel for the multi-channel ultrasonic instrumentation
required to pulse the individual transducers, and in turn, the arrays.
As
used herein, the term "forward advance" means the product of the
resultant revolutions per minute and the helical advance, based on not
exceeding the assumed constants.
The present invention, designed
to meet the American Petroleum Institutes (API's) Specification 5CT for
the detection of longitudinal, transverse, and wall thickness anomalies
or defects in Oil Country Tubular Goods (OCTG) using the
ultrasonic method, seeks to greatly increase the throughput speeds, while
simultaneously reducing the cost of the system by reducing the number
of ultrasonic channels needed to achieve 100% coverage, and making the
system a non-contact style (the shoes and/or transducers do not touch the
pipe which minimizes wear), leading to less maintenance.
Wall Thickness Inspection
Certain
drawings referred to herein depict the difference between conventional
ultrasonic probes and the curved composites used in the current
invention, both from a practicality standpoint and the associated. cost
benefits.
FIG. 1 depicts the problems associated with using a
long conventional transducer element for taking ultrasonic wall
thickness measurements. It can be seen that the sound emitted from the
center of the transducer strikes the tube perpendicular(90 degrees) to
the surface, which is a requirement for compression wave wall thickness
readings, while the beam from the outer edges strikes the pipe surface
at an incident angle of 69 degrees to the tangent of the circle, which
would result in no return of signal for wall measurement, as shear waves
would be induced in the part at the outer edges of the probe.
FIG.
2 shows how to overcome the restrictions of using a large flat element
for wall thickness measurements by using multiple individual elements,
or arrays, arranged in a curved case equidistant from the curved
surface. This is commonly done with conventional, composite, and newer
phased array systems, though it is apparent to anyone versed in the art
that the cost associated not only with the individual elements but to a
larger degree, the individual ultrasonic channels required to pulse the
multiple elements, that this method pales in comparison to the potential
to use a single element, though as we have shown, standard flat
transducers will not work for this application.
It is important
to realize that the use of the proposed curved composite probe
methodology for wall thickness measurement is on its own merits a viable
and valuable invention and product. The measurement of wall thickness
with ultrasound is commonly accepted as the most accurate measurement
system currently in use. A unique property of ultrasonic wall thickness
measurement is that to a large degree, increasing the distance from the
transducer face to the surface of the part being inspected does not
detract from the accuracy of the measurements taken.
As
demonstrated in FIG. 3, the use of the curved composite probes
contemplated in the present invention not only lend themselves to the
testing of multiple diameter tubulars, but in fact when the curvature is
designed for 100% coverage of the larger diameter range, and the
selected transducer radius is slightly larger than the largest diameter
to be inspected for wall thickness, the increase of the water path or
delay line also insures 100%+coverage on subsequent smaller diameters
passed through the fixed circular array without the necessity of changing
the probes or their position relative to the center of the circle.
This is possible because the incident angle for wall thickness
inspection is perpendicular to the tubular being tested and the relative
movement closer or further from the test specimen does not alter this
angle of incidence. The ability to inspect for wall thickness in this
manner reduces changeover time for varying diameters of tubes and
guarantees full coverage over a range of diameters. This is of
particular importance given upcoming changes to API specifications
(already in draft form) in the area of Product Specification Levels
(PSL's) that may require 100% wall coverage on tubulars historically
inspected with the gamma wall source found on electromagnetic (EMI) tube
inspection units. This feature of the current invention makes the wall
inspection component viable as a replacement for current gamma wall
measurement systems, in use worldwide, and well know to those familiar
with the currently available technology.
Transverse Flaw Inspection
In
the case of transverse flaw inspection, the same curved composite
probes envisioned above would entail two additional sets of probes of
similar physical dimensions as depicted in FIG. 3, though the transverse
flaw inspection portion would entail two rings of transducers, one
leading and one trailing, angled 19 degrees in water to produce a 45
degree refracted angle, pointing down the axis of the pipe with the
sound beams directed at the two respective pipe ends.
FIG. 4
depicts the current methodology of using multiple transducers in tandem,
as a collection of overlapping effective beams, to produce 100%
coverage at, in this depiction, a potential 2.8'' helix per revolution.
In other words for each revolution of a pipe the set of transducers can
move forward 2.873'' (helical advance). The leading end of the
transverse array is shown on the left and the trailing end of the
transverse array is shown on the right. Transducer elements having
a0.500'' diameter are shown, each transducer element encased in a
0.625'' diameter case and having an effective beam 0.35'' in diameter.
The solid arrows shown projecting from the transducer array indicate the
direction of the combined ultrasonic beam. To detect transverse flaws,
the prior art transducer array utilizes eight 0.500 inch element
transducers with an approximate 2.8 inch coverage. (Calculated by
0.625'' transducer case-0.500'' transducer element-0.350'' effective
beam times 8transducers=2.8'' array).
FIG. 5 illustrates a
problem common to inspection for transverse flaws from an ease and
consistency of detection perspective. The top portion of FIG. 5
illustrates a transverse transducer and the direction of its effective
beam (indicated by the solid arrow projecting axially). A longitudinal
transducer and the direction of its effective beam are illustrated
directly below the transverse transducer. The distance from the
effective beam to the flaw (illustrated as a horizontal line above
the transverse transducer) can vary only slightly without an adverse
impact on the probability of detection. Where the longitudinal
transducer can have an axial displacement of up to 1'' and still detect
the longitudinal flaw with the effective beam, the transverse transducer
with only slight axial movement either misses detection of the flaw, or
results in an amplitude decrease which would result in the signal
falling below pre-established alarm thresholds.
In the current
invention, this obstacle is of course negated with the tubular traveling
axially past a fixed curved transducer. This phenomenon is briefly
mentioned in the previously referenced article "First Results Of
Composite Transducers Used in Automatic Rotating Ultrasonic Inspection
Units," where discussing the results of sensitivity during a
transversal-test as follows: Here, the sensitivity is poor for standard
probes due to the small pulse response caused by the reason that
the focal line is perpendicular to the defect orientation to fulfill 100%
coverage. The article discusses that this is caused by the improvement
of bandwidth and additionally by the influence of the optimized sound
field of the piezo composite probe by curving the material itself. As
previously discussed, the curving is specific to small individual probes
used in an array of the type depicted in FIG. 4 above, and does not
consider the curving of a large single element to replace this entire
array, as is the focus of the present invention.
As with the wall
thickness inspection component depicted in FIG. 3, when performing
transverse flaw inspection, moving the transducer closer or further from
the surface of the part being inspected does not alter the incident
inspection angle as shown in FIG. 6.
This ability to sustain
movement closer or further from the pipe surface without impacting the
incident inspection angle is common only to the transverse and wall
thickness inspection methods and does not apply to the ultrasonic
inspection for longitudinally oriented flaws, as discussed in greater
detail in the following section.
Of merit however, is that just
as the wall thickness component of the proposed invention has commercial
applications as a stand alone inspection device, when the wall system
is coupled with the transverse inspection component, a far
superior method for the inspection of used drill pipe, which requires
only transverse and wall thickness inspection, can be realized.
The
most common methodology in use today for the inspection of used drill
pipe is a multi-part inspection, but for the purpose of the proposed
embodiment, only the tube body and critical (slip) end area inspections
are considered and discussed. In the inspection of used drill pipe, an
electromagnetic "buggy," is run down the tube body for the detection of
transversely oriented defects or fatigue cracks, which can be formed due
to the stresses involved in the drilling process. This technology has
not changed significantly in decades and is time consuming and does not
offer the superior detection possibilities associated with ultrasonic
inspection. For more critical applications, a secondary inspection is
often incorporated, using the ultrasonic method to locate transverse
flaws in the slip area of the drill pipe tube. This scanning is
currently performed by hand with either a single probe affixed to a
wedge, or through the use of a commercially available, hand held device
with the ultrasonic transducers mounted in a fluid filled wheel that
traverses the area of interest at a fixed helical advance, while the
tube is rotated in place. Both these methods are time consuming and
labor intensive, making this a costly, albeit necessary inspection on
used drill pipe. By combining the wall thickness and transverse
components of the current invention, and traversing the drill pipe
through a water filled "stuffing" box, or as mentioned later, alternate
coupling means such as lucite/rexolite wedges fluid filled wheels to name
examples, common to those versed in the industry, it is possible not
only to achieve a more critical ultrasonic inspection of the tube body
but at the same time and in a single pass, inspect the critical end area
and negate the need for a costly, labor intensive, secondary inspection
of this critical area.
Further discussions of curving composite
probes are referenced in two additional technical papers, the first of
which is "Improvements Of Ultrasonic Inspections Through The Use OF
Piezo-Composite Transducers" authored by Gerard Fleury and Christian
Gondard in May of 1995. Specifically in the area of reference to array
probes, the article speaks to the regrouping of the transducer elements
in the form of long and curved electrodes, but again is referring only
to a multitude of individual elements used in tandem in an array, as
shown in FIG. 7, which accompanied the technical paper. The left hand
portion of FIG. 7 shows a completed transducer with cabling and black
face material while the right hand portion shows an artists rendering
of the multiple curved composite elements use to manufacture the finished
product.
And the second being the Article "Use of Flexible
Ultrasonic Arrays in Inspection," published in March 1999 and authored
by Jocelyn Langlois, outlines forming a flexible transducer array by
using a multitude of small elements as contemplated in the Splitt
publication. Specifically, in the Langlois article an ultrasonic array
is discussed with 1024 0.250''.times.0.250 transducer elements arranged
in an 32.times.32 element matrix, vacuum coupled to a 12 inch diameter
pipe. Although the application contemplated in this article differs
vastly from OCTG tubular inspection, the desire to curve probes using
multiples single elements and the advantages that can be realized are
noteworthy.
Longitudinal Flaw Inspection
The inspection
for longitudinal defects, oriented along the axis of the tube presents a
whole new set of parameters and problems as opposed to wall thickness
and transverse inspection, as were previously discussed and depicted in
FIGS. 3 and 6. This is due to the relationship of the incident angle of
the ultrasonic wave striking the curvature of the tube, and the adverse
effects that slight movement of the probe in relation to the part being
tested has on the incident angle and in turn the refracted inspection
angle of the desired 45 degrees.
In the case of longitudinal flaw
inspection, where the tube radius becomes a factor, this is not the
case as shown in FIG. 8. FIG. 8 shows the sensitivity to change of the
longitudinal inspection transducer, with an associated upward movement
of only 0.100'', before drastically altering the desired incident and
refracted angles. In this example, the 19 degree incident angle would
result in the desired 45 degree refracted angle, while the 12 degree
incident angle would alter the refracted angle by 17 degrees with a
resultant refracted angle of 28 degrees, which would effect such a
drastic change to inspection amplitude results that this is not only
undesirable, but unacceptable to OCTG tube inspection. In fact, this
phenomenon negates even the possibility of encircling the tube with, for
example, 0.500'' elements as we have used for demonstration on both the
wall thickness and transverse inspection methods. This has been a major
factor to the advent and maturing of phased array technology, which uses
much smaller probes and actually "steers" the sound beam to compensate
for this attribute of the ultrasonic longitudinal defect inspection
method.
U.S. Pat. No. 4,195,530 to Ross et al. (the "'530
patent") describes an ultrasonic device for the inspection of a
longitudinal weld in a tubular product. The transducer technology
discussed in detail in the current invention, namely piezo composite
probes, was not in existence in 1980 when the '530 patent was issued.
Given the advances in transducer manufacturing and the beam
characteristics that are possible with curved composite probes, the
theory of the '530 patent can now be applied to full body ultrasonic
inspection as opposed only the inspection of a small area of a tubular
as previously envisioned, namely a weld seam.
As is shown FIG. 9,
a curved composite transducer can be developed for a range of tubular
diameters (in this example, one length and radius transducer capable of
inspection of sizes from 9.625 to 13.375) with various transducers being
fabricated based primarily on radius and length to cover identified size
ranges of OCTG for optimum coverage with a minimal number of transducer
configurations. As the drawings of FIG. 9 depicts, on diameters of
13.375 and 9.625 pipe, a transducer with a radius of7.188 inch and a
length of 3.758 inch, the incident angles of 19 degrees in water, which
in turn produces a refracted 45 degree angle in the pipe being
inspected, provide 3.497 inches of surface coverage on the large pipe
and a 2.516 inch of surface coverage on the smaller 9.625 inch pipe. For
each pipe diameter there can be determined an optimum transducer as
defined by radius and length that is best suited for a specific pipe
diameter when inspecting for longitudinal flaws. As demonstrated in the
top drawing of FIG. 9, it is possible to select transducer properties
that can apply to a range of diameters while still achieving the desired
properties including incident angle, water path, etc.
Any
changes to the incident ultrasonic beam angle effects the refracted
inspection angle in the part being tested. FIG. 10 illustrates that the
current invention incorporates a method much better to the prior art
method described in FIG. 8, int hat comparable changes in the incident
angle in the proposed method do not result in near the adverse effects
inherent to the current technology. FIG. 8 demonstrated that a
displacement of 0.100 inch with a conventional probe caused 7 degree
variance in the incident angle. However, in the present invention an
identical movement of the ultrasonic probe results in only a 1 degree
incident angle change. The present invention is more forgiving relative
to the pipe centering and inherent shoe wear during the ultrasonic
inspection process.
While it is taught in the '530 patent that
"any dimension beyond this minimum (length) is excess and serves no
useful function. Since the cost of fabricating the ultrasonic
transducer surface increases as the size of the transducer increases, the
minimum dimension should not be exceeded."
As is demonstrated in
FIG. 9, when considering full 100% coverage of the tube body, this
excess which in the '530 patent is deemed undesirable, in the current
invention, excess length can actually work as an advantage as it allows
for a single radius and length of curved element to be used over a range
of diameters, thereby actually reducing the overall cost and number of
transducers needed for the final full body inspection unit.
As
the current invention's goal is 100% coverage of the tubular being
inspected, in all the required inspection orientations including wall
thickness, transverse, and longitudinally oriented defects, the theory
outlined in '530 patent for the isolated inspection of a small segment of
the tube circumference for longitudinal flaws, must be expanded upon to
achieve the desired 100% coverage necessary for full body ultrasonic
inspection for longitudinal defects. The current invention
addresses this shortcoming in the following manner, as depicted below in
FIG. 11.
FIG. 11 illustrates that by using the inspection method
of the current invention, full 100% coverage of a tubular with a
13.325'' diameter can be obtained using only. thirteen ultrasonic
channels and transducers. This number would then be doubled, to insure
coverage in both the clockwise and counterclockwise directions. The
transducers are shown with a radius of 7.187''.
To achieve
similar coverage using current conventional technologies, on the same
diameter pipe and assuming an effective beam width of 0.500'' the
transducer configuration would be as depicted in FIG. 12. Though as
previously discussed above, the sensitivity to change of incident angle
relative to longitudinal flaw inspection negates even the possibility of
encircling the tube with, for example, 0.500'' elements as we have used
for demonstration on both the wall thickness and transverse inspection
methods.
It would require a total of seventy-five channels and
transducers, with the associated costs, to achieve the 100% overlapping
coverage achieved with only 13 channels and transducers as embodied in
the current invention. To re-iterate, this 75channel total would be
doubled to achieve the required the coverage in both clockwise and
counterclockwise directions. At the conservative cost of $3,000.00 per
ultrasonic channel listed in the chart, this results in a cost reduction
of $186,000.00which in turn would be doubled for both clockwise and
counter-clockwise inspection.
Thus far, all calculations and
discussions surrounding the current invention envision the transducers
being mounted inside a water "stuffing" box with the tubular being
transferred axially through the center of. the circular rings of
probes. It will be apparent to those versed in the art that the embodied
invention will also work using the contact method whereby the curved
transducers are affixed to a wedge, the opposite dimension of which is
machined to a radius to match the curvature of the tube being inspected.
This is true for the wall thickness, transverse, and longitudinal
portions of the present invention.
To summarize, the totality of
required transducer rings envisioned in the current invention consist of
the five sets pictured in FIGS. 13A-13E. FIG. 13A is a set of
transducers to monitor the transverse leading portion of the pipe. FIG.
13B is a set of transducers to monitor the wall thickness of the pipe
providing 100% coverage. FIG. 13C is a set of transducers to monitor
the transverse trailing edge of the pipe. FIG. 13D is a set of
transducers to monitor for longitudinal in the clockwise direction. FIG.
13E is set of transducers to monitor for flaws in the counter-clockwise
direction.
It is also important to note that the specially
designed curved composite transducers contemplated for use in the
current invention also apply to the currently used technologies, namely
helical advance, overhead gantry, and rotary head ultrasonic systems. If
the probes outlined herein are incorporated into a conventional
inspection unit, the same advantages relative to fewer channels and
higher speeds still apply.
As an example of these inherent
advantages, the transducer depicted in FIG. 14 will be used for
calculation purposes, specifically the beam coverage at the 9.625
diameter pipe surface that is measured at 2.261''. For calculation
purposes, a2.00'' coverage at the pipe surface will be used to determine
coverage per array. It should be noted that the transducer face, is
mounted close to the pipe surface to capitalize on the increased
coverage capabilities at the "base" of the triangle. The delay line
(water, rexolite, lucite, etc.) from the top edge to the bottom edge of
the embodied transducer ranges from 0.443'' to 1.188'', well within the
range of conventional units currently in use that employ the varied
methods of coupling the transducer to the tube, common to those in the
industry.
An inherent shortcoming of the embodied invention is
that by utilizing the described method for longitudinal flaw detection,
the location of a flaw indication, relative to the internal diameter
(ID) or outer diameter (OD) surface of the tube, cannot be determined as
it can with the currently used technologies previously outlined, which
typically use separate flaw "gates" to monitor the internal and external
surfaces and help identify the location within the tube body wall,
relative to the ID and OD surface. This shortcoming is due to the
variance in the delay line between the face of the transducer and the
surface of the tube being tested which in turn cause signal return time
differences across the face of the probe.
The increased
productivity and lower cost of the embodied ultrasonic inspection system
substantially offset the disadvantage of not being able to achieve
ID/OD differentiation. Most importantly, this minimal variance in water
path does not detract from flaw detectability or unit performance
overall, from a quality of inspection perspective.
If however
this ability to differentiate ID and OD indications is a requirement in a
particular environment, another aspect of the current invention is the
ability to use the transverse and wall thickness sub-systems of the
overall unit to make use of the advantages these methods have as stand
alone components in terms of production levels and lower costs. It was
previously outlined how these two sub-systems could perform as viable
products on their own merits, in the areas of wall thickness measurement
and used drill pipe inspection. The transverse and wall system could be
coupled with, for instance, a rotating head ultrasonic inspection
scheme, but with the added advantage of having all the ultrasonic
channels associated with the rotary head focused solely on longitudinal
flaw inspection. By using this approach, and depending on the number of
available channels and the associated channel configuration, the speed
of a rotary UT head could be increased dramatically as further
outlined below.
Rotary heads common to the industry typically use
four inspection sensor holders positioned equidistant around the tube
circumference. As shown by the helically sectioned pipe in FIG. 15, a
transducer in each inspection shoe has a corresponding complementary
transducer with the same properties and position within the individual
shoes. The rotational speed and axial feed rate are adjusted to achieve
the desired and required effect of 100% overlapping coverage when the
multiple inspection sensor holders work in concert as the tube is
inspected.
If one takes a typical rotary head unit with a
plurality of transducer arrays as described in FIG. 4 and further in
FIG. 16, the resultant rotary head unit would have two leading and two
trailing transverse arrays as in FIG. 4, each capable of producing a
2.873'' helical advance mounted in opposing test shoes 1 and 3. When
the rotation head speed and the pipe forward line speed are set to
produce the desired 100% coverage, these two opposing shoes would
produce a combined helical footprint or advance per revolution of 2.873''
times 2, or 5.746'' per revolution.
To perform the entire test
as dictated by the API specifications longitudinal and wall thickness
flaws must also be detected with additional test transducers and
electronic channels. For longitudinal inspection, this scheme would be
identical to that used for the transverse inspection, with two primary
differences, the two 8 channel clockwise and counterclockwise arrays
would be positioned to look around the circumference of the pipe and
would be located in opposing shoes (as in FIG. 16) two and four with the
resultant helix for the longitudinal also being 5.746'' per revolution.
For
the remaining wall thickness inspection, the arrays are typically
spread evenly among the test shoes 1 through 4, as unlike transverse and
longitudinal, wall inspection is performed with the transducer sound
beams directed perpendicular to the pipe surface, negating the need for
leading and trailing probe in the case of transverse inspection, or
clockwise/counterclockwise opposing arrays in the case of longitudinal.
So for wall thickness inspection, each shoe 1 through 4 would have
four wall thickness transducers with the resultant helical advance being
equal to the longitudinal and transverse arrays, or 4 transducers per
shoe with an ultrasonic footprint or effective beam area per 4
transducers of 2.873 divided by 2, or 1.437'' per shoe each of the test
shoes one through 4, for a total wall thickness coverage area of 1.437''
times 4, or 5.746'' per revolution, identical to the longitudinal and
transverse combined arrays.
A marked improvement in productivity
and pipe throughput to this standard rotary style ultrasonic unit can be
obtained by combining this standard technology with components from the
proposed invention, namely the circular wall thickness and transverse
arrays, which as discussed, are not as sensitive to variances in
distance from the pipe surface as in the case of the longitudinal
inspection system. This would be accomplished by adding a non-contact,
non-rotating encircling transverse and longitudinal inspection ring
immediately prior to the existing rotary head mechanics in a water
"stuffing" box, or other industry accepted method of ultrasonic coupling
previously discussed. The test heads 1 through 4 remaining on the
standard rotary head would be modified whereby all previous transverse
and longitudinal transducers would be dedicated only to longitudinal
inspection, with all ultrasonic transducers in the rotary head, a total
of 64 channels or 16 per shoe, positioned to inspect around the pipe
circumference to detect longitudinal oriented defects.
So for
transverse inspection, portions of the array depicted in FIG. 4 would be
split among the four surrounding, equidistant shoes as follows, 4 per
shoe (2 leading and two trailing). This assumes a total number of
transducers being dedicated to transverse flaw inspection to be double
the amount in FIG. 4, to allow for leading and trailing inspection. In
this configuration, a typical rotary head unit, with the addition of two
components from the proposed invention, would be capable of inspection
speeds twice as fast as before due to an increase in helical advance
from 5.746'' up to 11.492'' with only an incremental increase in
channels as described with reference to FIGS. 13A, B, and C.
The
novelty of this approach is that this can be achieved with no increase
in the rotary head speed, (which is the limiting factor for production
on this type of unit, i.e. the mechanical mass can only be spun so fast)
could then be devoted to strictly longitudinal arrays as previously
described.
Perhaps of even greater interest would be to couple a
phased array longitudinal inspection system with the transverse and wall
components of the current invention, but mount the individual phased
array channels within a curved transducer case to duplicate the
ultrasonic "wave front" as the composite transducers embodied in the
present invention. One of the features of phased array ultrasound is
numerous ultrasonic channels per transducer case or housing. As
previously mentioned, a single transducer housing could contain up to 256
individual transducer elements, all requiring individual electronic
channels. As shown in FIG. 16, a phased array transducer, formed in
this way and used in the described manner, provide not only the
consistent angle of incidence as contemplated by the current invention,
but also provide the ability to differentiate between ID and OD flaws,
as modern phased array systems track flaw signal return on a per element
basis, and can then perform calculations to make the determination of
flaw location within the body wall possible.
Even though the
benefits of using the proposed transverse and wall thickness components
with, for example, a rotary head unit are obvious to one versed in the
art, they pale in comparison to the advantages that these stand-alone
systems can yield to a phased array full length tube inspection machine.
By their nature, phased array systems are very expensive due to the
high number of ultrasonic channels required to obtain 100% coverage, the
high cost of related transducers, and high cost of coaxial signal cable
among other factors. In fact, to date, the only axial feed (as
contemplated by the current invention) phased array inspection system
for large diameter pipe addresses only longitudinal and wall thickness
inspection, with the inspection for transverse flaws being performed with
an after market flux leakage system common in the industry. This
course of action was due in part to the technological obstacles
associated with phased array technology for the detection of
transverse flaws, as well as the excessive costs associated with the
number of channels that would be required to inspect for transverse
flaws were the phased array method used.
Comparison of Old Technology and Present Invention
For
calculation and comparison purposes, we will consider that no time is
lost due to loading or unloading, gaps between successive tubes,
mechanical breakdown, or paused in production of any kind. In essence,
the tubes are run through "end to end."
It should be noted, that
from a cost per channel perspective, a comparison of the embodied
invention to currently used technologies is not feasible as the number
of channels required in a conventional testing machine, to match the
production rates of the described invention, are a moot point as
mechanical restrictions preclude current methodologies from obtaining
equal production possibilities.
Table 1 identifies certain parameters utilized for comparison of the present invention with prior technology.
| | TABLE 1 | | | | | | Pulse repetition rate | 2.5 khz | | | Transducer element size | 0.625″ | | | Effective beam 70% | 0.438″ | | | Acceptable pulse gap | 0.040″ | | | Number of transducers per array | 8 | | | Tube length | 50 ft | | | Coverage per array 8 X .438 = 3.50″ | | | Average cost per ultrasonic Channel | $3,000.00 | | | |
|
The following
Table 2 demonstrates a significant increase in productivity were it
possible to design and manufacture such a system, requiring no rotation
of the tube or test head.
| TABLE 2 |
| |
| | Crystal diameter | Effective beam | Pulse rate | surface speed |
| |
| Pulse Gap Calculator | 0.625 | 0.438 | 2500 | 100 |
| |
| | | | | helical |
| | Rpm | Pipe diameter | pipe circ. | advance |
| |
| Surface Speed | 199 | 9.625 | 30.22 | 3.5 |
| |
| | Forward advance | | |
| | Feet per Minute | Tubes per hour | Tubes per 12 hour |
| |
| Prior Technology | 58 | 69 | 834 |
| |
| | Feet per minute | | |
| Present Invention | Potential axial speed | Tubes per hour | Tubes per 12 hour |
| |
| | 500 | 600 | 7200 |
| |
| | Current tubes | Potential tubes | Percent production |
| | per 12 hr turn | Per 12 hr turn | Improvement |
| |
| Production Comparison | 834 | 7200 | 863.5% |
| |
Although
the present invention and its advantages have been described in detail,
it should be understood that various changes, substitutions and
alterations can be made herein without departing from the invention as
defined by the appended claims. Moreover, the scope of the present
application is not intended to be limited to the particular embodiments
of the process, machine, manufacture, composition of matter, means,
methods and steps described in the specification. As one will
readily appreciate from the disclosure, processes, machines, manufacture,
compositions of matter, means, methods, or steps, presently existing or
later to be developed that perform substantially the same function or
achieve substantially the same result as the corresponding embodiments
described herein may be utilized. Accordingly, the appended claims are
intended to include within their scope such processes, machines,
manufacture, compositions of matter, means, methods, or steps.
* * * * * |
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