U.S. patent application number 14/753423 was filed with the patent office on 2015-10-22 for systems, methods and devices for strengthening fluid system components using radiation-curable composites.
The applicant listed for this patent is Neptune Research, Inc.. Invention is credited to Jozef Bicerano, Christopher J. Lazzara.
Application Number | 20150299941 14/753423 |
Document ID | / |
Family ID | 45874140 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150299941 |
Kind Code |
A1 |
Lazzara; Christopher J. ; et
al. |
October 22, 2015 |
SYSTEMS, METHODS AND DEVICES FOR STRENGTHENING FLUID SYSTEM
COMPONENTS USING RADIATION-CURABLE COMPOSITES
Abstract
Methods are provided for strengthening (e.g., repairing,
structurally reinforcing, etc.) a fluid-system component by
installing, as a circumferential wrap or a patch, a
radiation-curable composite laminate. Kits including composite
repair materials and equipment for implementing the methods are
also provided. Examples of fluid-system components that may be
strengthened include pipework, pipelines, transmission pipelines,
distribution pipelines, gathering lines, oil risers, gas risers,
process piping, girth welds on pipelines or vessels, tanks,
vessels, elbows, tees, flanges, and high-pressure injection lines.
An approach where, prior to curing, the precursor to the composite
laminate comprises a glass fabric, a carbon fabric, or any
combination(s) thereof, pre-impregnated with an uncured epoxy
resin, an uncured epoxy acrylate resin, or a mixture thereof, is
used; curing is performed via electron beam irradiation; and the
installation and curing procedures can be automated to the maximum
extent possible, in exemplary embodiments of the present
disclosure.
Inventors: |
Lazzara; Christopher J.;
(Palm Beach Shores, FL) ; Bicerano; Jozef;
(Midland, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Neptune Research, Inc. |
Riviera Beach |
FL |
US |
|
|
Family ID: |
45874140 |
Appl. No.: |
14/753423 |
Filed: |
June 29, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13820806 |
Mar 5, 2013 |
9096020 |
|
|
PCT/US2011/052472 |
Sep 21, 2011 |
|
|
|
14753423 |
|
|
|
|
61386065 |
Sep 24, 2010 |
|
|
|
Current U.S.
Class: |
442/150 |
Current CPC
Class: |
B29C 71/02 20130101;
D06M 15/55 20130101; D06M 15/564 20130101; B29C 2035/0827 20130101;
Y10T 442/2746 20150401; F16L 55/16 20130101; F16L 1/00 20130101;
F16L 55/1683 20130101; B29C 2035/0877 20130101; B29C 2035/0855
20130101; B29C 2035/0844 20130101; B29C 73/10 20130101; B29C 70/30
20130101; B29C 2035/085 20130101; B29C 73/04 20130101 |
International
Class: |
D06M 15/55 20060101
D06M015/55; D06M 15/564 20060101 D06M015/564; F16L 55/16 20060101
F16L055/16 |
Claims
1-34. (canceled)
35. A composite laminate for repairing a section of a pipeline
assembly, the composite laminate comprising: a fabric carrier
including a continuous reinforcing fiber, the fabric carrier being
pre-impregnated with a reactive precursor chemically configured to
activate and harden upon exposure to artificial radiation but not
water, the reactive precursor being further chemically configured
to activate at water depths ranging from approximately 0.3 to 6,096
m (1 to 20,000 ft.), temperatures of approximately -15.degree. C.
(5.degree. F.) and higher, or both, wherein activating the reactive
precursor creates a load-bearing repair implement from the
composite laminate, the load-bearing repair implement exhibiting a
tensile strength of at least approximately 86.2 MPa (12,500 psi) in
at least one principal axis direction.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to pipes, pipeline
assemblies, and fluid systems. More particularly, this disclosure
relates to systems, methods and devices for strengthening fluid
system components using radiation-curable composites.
BACKGROUND
[0002] Fluid conduit assemblies, such as pipelines and hydraulic
circuits, are used to transport an assortment of fluids, such as
water, oil, various natural and synthetic gases, sewage, slurry,
hazardous materials, and the like. Similar structures are utilized
for transmitting electrical and fiber optic cabling across vast
expanses of land in establishing telecommunication networks. The
most commonly used conventional methods for repairing damaged fluid
system components, such as carrier pipes, include the replacement
of the component or the welding of a repair sleeve over the damaged
section of the component. Such conventional remediation methods
generally requires a costly interruption in system operation until
the repair is completed. Furthermore, repairs based on such
conventional remediation methods generally requires the costly and
difficult transportation and handling of heavy repair parts, such
as steel replacement components or steel repair sleeves for the
remediation of damage in a metal pipe.
[0003] It has been established over the last two decades that
composite repair system using a composite laminate can often
provide a reliable and cost-effective means for repairing a damaged
fluid system component. The installation of a composite laminate
can often be performed without needing to interrupt operation of a
fluid system. Furthermore, the materials that need to be
transported and handled in order to install a composite repair
system are lighter and less cumbersome than conventional repair
materials, reducing the cost of making a repair as compared with
replacing a damaged metal component or installing a metal repair
sleeve.
[0004] In general, there are four types of composite repair
systems. In one type of composite repair system, precured plies of
a composite material (such as a glass fabric or a carbon fabric in
a cured thermoset polymer matrix) are "glued together" ply-by-ply
by using an adhesive as they are wrapped around a fluid system
component that is being repaired. A commercial example of this
approach is provided by the Clock Spring.TM. Repair Composite
Sleeve manufactured by Clock Spring Company, L.P., of Houston, Tex.
Some disadvantages of this approach include the fact that precured
plies are generally quite rigid so that repairs can be difficult
(and sometimes impossible) to perform on fluid system components,
especially those possessing complex shapes.
[0005] In another type of composite repair system, a dry fabric
(such as a dry glass fabric or a dry carbon fabric) is wrapped
around the fluid system component that is being repaired. The
fabric is then impregnated with an uncured resin, and the resin is
cured. A commercial example of this approach is provided by the
Carbon-Ply Composite Repair System manufactured by Crosslink
Composites LLC of Wellsboro, Pa. One primary disadvantage of this
approach is that the wetting of a wrapped (and hence multilayer)
dry fabric in the field can incur the risk of poor final cured
composite quality as a result of a possible undetected failure of
an uncured resin formulation, especially if it does not possess an
extremely low viscosity necessary to completely "soak through" the
multiple layers of the dry fabric as required for proper
impregnation. Installations made by using this approach are, hence,
especially susceptible to quality variations related to field
technician performance.
[0006] In another type of composite repair system, an uncured resin
formulation is applied to a layer of a dry fabric before wrapping
this layer of fabric (now in a wetted form) around a fluid system
component. There are some inherent risks related to field
technician performance during the impregnation of the fabric since
the technician must start with a layer of dry fabric and impregnate
it in the field before wrapping it around the fluid system
component. This approach is used in many composite repair systems
comprising two-part (resin and hardener) epoxy resin formulations.
Many such formulations cure thermally at moderate temperatures once
the two parts are mixed. Consequently, the two parts must remain
unmixed until the product is ready to be installed in order to
prevent premature curing. A commercial example is provided by the
RES-Q.TM. Composite Wrap manufactured by T. D. Williamson, Inc of
Tulsa, Okla.
[0007] In another type of composite repair system, a fabric (such
as a glass fabric or a carbon fabric) is pre-impregnated in a
manufacturing facility with an uncured resin. The resulting "wet"
fabric (pre-impregnated with uncured resin) is packaged and
transported to a repair site in a manner that protects it from
premature curing. The wet fabric is subsequently removed from its
packaging, wrapped around the fluid system component that is being
repaired, and the resin is cured. When using a resin formulation
that can be protected reliably from premature curing, this approach
is preferable because it eliminates many quality risks associated
with impregnating the fabric with an uncured resin in the field by
performing the impregnation under controllable conditions in a
factory. Two commercial examples are provided by Syntho-Glass.TM.
XT and Viper-Skin.TM., manufactured by Neptune Research, Inc. of
Lake Park, Fla., both of which use a moisture-curable polyurethane
resin formulation. A bidirectional glass fabric is used in
Syntho-Glass.TM. XT, while a hybrid bidirectional fabric woven by
using a carbon fiber in one direction and a glass fiber in the
other direction is used in Viper-Skin.TM..
[0008] Existing composite laminate materials targeted for use in
repairing fluid system components are currently limited by the
availability of only thermal curing, moisture-activated curing, and
moisture-activated curing with thermal postcuring methods for
obtaining a load-bearing composite laminate. These composite
materials, however, are impractical in certain applications. For
instance, proper installation of a moisture-cured or
thermally-cured composite repair system may not be feasible in
sub-zero environments, such as repairing sections of the
Trans-Alaska Pipeline during the winter months. In another
non-limiting example, the mileage of installed deepwater pipelines
continues to grow rapidly. It is very cumbersome, as well as
expensive, to perform deepwater pipeline repairs based on
conventional repair approaches, some of which include installing
clamps and/or connectors, replacing damaged pipe sections, and, if
necessary, lifting a damaged pipe section to the surface rather
than repairing it in the deepwater environment. Some related
background information is provided by B. Povlovski, in "Deepwater
Pipeline Repair--Lessons Learned and New Advances", Proceedings of
the 20th Deep Offshore Technology [DOT] International Conference,
Houston, Tex., Feb. 12-14, 2008, which is hereby incorporated by
reference herein in its entirety.
[0009] Composite laminates have not yet made many inroads into
deepwater pipeline repairs, mainly because of aspects related to
how the composite laminates are cured. Many thermally-curing
composite laminates require threshold curing temperatures to obtain
an acceptable level of cure at an acceptable rate. These threshold
temperatures are oftentimes costly and difficult or otherwise
impossible to achieve in deepwater environments and/or subzero
temperatures. On the other hand, the use of a moisture-activated
curing composite laminate in a deepwater environment is often
hampered by its inherent tendency to cure prematurely upon exposure
to the water in which a deepwater pipeline is submerged. The
opportunity to expand the range of applications of composite
laminates to include deepwater and cold pipeline repairs is just
some of the many possible examples of why there is ongoing
development of new methodologies for the repair of fluid system
components by using composite laminate compositions that do not
rely on thermal or moisture-activated curing as their primary
curing mechanism.
SUMMARY
[0010] According to one aspect of the present disclosure, a method
is provided for strengthening (i.e., repairing, structurally
reinforcing, or combinations thereof) a fluid system component by
installing, externally to it, as a circumferential wrap or as a
patch, a radiation-curable composite laminate. In this context, a
"radiation-curable" composite laminate may be defined as a
composite laminate where chemical reactions induced directly by the
radiation play an important role in the curing process. As a
non-limiting comparison, some uncured composite laminates are
placed under direct sunlight to increase its temperature. A
composite laminate that is cured primarily by thermal curing
reactions that could have been obtained by heating it to the same
temperature by some other means (e.g., placing it in an oven) is
not considered to be "radiation-curable" since sunlight has merely
provided a means for heating it so that thermal curing can take
place. On the other hand, if the ultraviolet component of sunlight
interacts with the uncured composite laminate and induces
photochemical reactions that provide a primary mechanism for
curing, then it is considered to be "radiation-curable".
[0011] Non-limiting examples of fluid system components that may be
strengthened include pipework, pipelines, transmission pipelines,
distribution pipelines, gathering lines, oil risers, gas risers,
process piping (for chemicals, oil, gases, water, or steam), girth
welds on pipelines, tanks, vessels, girth welds on vessels, elbows,
tees, flanges, and high-pressure injection lines. In an exemplary
embodiment, prior to curing, the precursor to the composite
laminate comprises a glass fabric, a carbon fabric, or combinations
thereof, that is pre-impregnated with an uncured epoxy resin, an
uncured epoxy acrylate resin, or any mixtures thereof. Curing is
performed via electron beam irradiation. The installation and
curing procedures can be automated to the maximum extent possible,
in various exemplary embodiments. Repair kits including composite
repair materials and equipment for implementing the method are also
provided.
[0012] The American Society of Mechanical Engineers (ASME)
published "Repair of Pressure Equipment and Piping," Part 4
(Non-Metallic and Bonded Repairs), Article 4.1, "Non-Metallic
Composite Repair Systems: High Risk Applications," (2006), which is
hereby incorporated by reference herein in its entirety. This
standard defines a circumferentially wrapped composite repair
system and its components, describes tests to qualify such a
composite repair system, provides computational methods for
designing optimum composite repair systems for specific classes of
repair situations, and provides general guidelines for system
installation and installer qualification. To date, there are no
legal or regulatory requirements for a manufacturer to qualify a
composite repair system based on Article 4.1. Nevertheless, it may
be desirable to voluntarily subject new composite repair products
to the testing required for qualification under this standard.
[0013] Article 4.1 provides criteria for the qualification of a
composite repair system in making repairs for (a) external and/or
internal wall losses that often occur in fluid system components as
a result of corrosion, and (b) leaks of fluid system components.
There is, however, ongoing research to define the best practices
for the safe and reliable use of composite repair systems for the
repair of additional types of damage; such as but not limited to
dents, gouges, and combinations thereof. For example, Dr. Chris
Alexander describes some of the ongoing research in "Repairing
Mechanically-Damaged Pipelines," PipeLine and Gas Tech., Vol. 8,
No. 7, pages 52-57, August 2009, which is hereby incorporated by
reference herein in its entirety.
[0014] It may be both impractical and unnecessary to wrap a
composite laminate around the entire circumference of a fluid
system component possessing a large diameter and/or inordinate
geometry. It is often more practical in terms of ease of
installation, less wasteful of materials and labor, and sufficient
from the point of view of achieving safe and reliable remediation,
to place a composite laminate in the form of a patch on a damaged
region rather than wrapping an elongated laminate around the entire
perimeter of such components. Heretofore, work had been started by
an ASME committee to develop qualification standards for repairs
using composite laminates as patches.
[0015] A method, comprising an external installation of a
radiation-curable composite laminate as a circumferential wrap or
as a patch, is taught for strengthening a fluid system component.
The term "strengthening," as used in this disclosure, is inclusive
of, inter alia, a repair made as a remedial action on a damaged
fluid system component, a structural reinforcement made to enhance
an undamaged fluid system component, or any combination thereof.
Fluid system components that may be strengthened are constructed
from materials such as, but not limited to, carbon steel, low and
high alloy steel, stainless steel, aluminum, titanium,
polyethylene, polyvinyl chloride (PVC),
acrylonitrile-butadiene-styrene (ABS) copolymers, fiber-reinforced
polymers, or concrete, or any combination thereof.
[0016] In one aspect, a method of the present disclosure comprises:
transporting near the location of the fluid system component a
fabric constructed from a continuous reinforcing fiber, wherein the
fabric is pre-impregnated with a reactive precursor; unrolling the
fabric and wrapping it around the fluid system component; and
applying radiation to cure the reactive precursor to obtain a
load-bearing composite laminate comprising the fabric in a
thermoset polymer matrix.
[0017] In another aspect, the method of the present disclosure
comprises: transporting near the location of the fluid system
component a fabric constructed from a continuous reinforcing fiber,
wherein the fabric is pre-impregnated with a reactive precursor;
unrolling the fabric and placing it as a patch over a portion of
the fluid system component; and applying radiation to cure the
reactive precursor to obtain a load-bearing composite laminate
comprising the fabric in a thermoset polymer matrix.
[0018] It is also contemplated that in certain embodiment, kits for
implementing the methods and systems, such as those descried
elsewhere herein, may be provided. The kits can include, among
other things, composite repair materials and/or equipment for
implementing such methods and/or processes.
[0019] Another aspect of the present disclosure is directed to a
method for strengthening a component in a fluid system. The method
includes: providing a composite laminate with a fabric carrier
including a continuous reinforcing fiber, the fabric carrier being
pre-impregnated with a reactive precursor chemically configured to
activate upon exposure to artificial radiation; placing the
composite laminate over a portion of the fluid-system component;
and applying artificial radiation to the fabric carrier such that
the reactive precursor is cured thereby creating a load-bearing
repair implement from the composite laminate
[0020] According to yet another aspect, a repair kit is presented
for strengthening a component in a fluid system. The repair kit
includes a composite laminate with a fabric carrier having a
continuous reinforcing fiber. The fabric carrier is pre-impregnated
with a reactive precursor that is chemically configured to activate
upon exposure to artificial radiation. The repair kit also includes
a radiation device operable to apply artificial radiation to the
composite laminate at sufficient intensity to thereby activate the
reactive precursor. Applying radiation to the fabric carrier such
that the reactive precursor is cured creates a load-bearing repair
implement from the composite laminate.
[0021] Also presented herein is a composite laminate for repairing
a section of a pipeline assembly. The composite laminate includes a
fabric carrier including a continuous reinforcing fiber. The fabric
carrier is pre-impregnated with a reactive precursor that is
chemically configured to activate and harden upon exposure to
radiation but not water. In some embodiments, the reactive
precursor is chemically configured to activate in water depths of
approximately 1 to 20,000 feet, water temperatures of approximately
-15.degree. C. and higher, or both. In other embodiments, the
reactive precursor is chemically configured to activate in water
depths of approximately 5 to 10,000 feet (1.5 to 3,048 meters),
temperatures of approximately -18 to 24.degree. C. (0 to 75.degree.
F.), or both. Activating the reactive precursor creates a
load-bearing repair implement from the composite laminate. The
load-bearing repair implement exhibits a tensile strength of
approximately 103.4 to 1034.2 megapascal (MPa) (15,000 to 150,000
pounds per square inch (psi)) (e.g., in at least one principal axis
direction) and an impact resistance of at least approximately 80
joules. In some embodiments, the load-bearing repair implement
exhibits an impact resistance of approximately 80 to 300 joules
and, in some embodiments, approximately 200 to 600 joules. In other
embodiments, the load-bearing implement formed from the composite
laminate exhibits a tensile strength of at least approximately 86.2
MPa (12,500 psi) in at least one principal axis direction. In other
embodiments, the load-bearing implement formed from the composite
laminate exhibits a tensile strength of at least 15,000 psi (103.4
MPa) in both principal axis directions. In yet some other
embodiments, the load-bearing implement formed from the composite
laminate exhibits a tensile strength of at least 30,000 pounds per
square inch (206.8 MPa) in at least one principal axis
direction.
[0022] The above summary is not intended to represent each
embodiment, or every aspect, of the present disclosure. Rather,
additional aspects of the disclosure will be apparent to those of
ordinary skill in the art in view of the detailed description of
various embodiments, which is made with reference to the drawings,
a brief description of which is provided below
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a perspective-view illustration of a
representative repair kit for strengthening fluid-system components
in accordance with aspects of the present disclosure.
[0024] FIG. 2 is a perspective-view illustration of a
representative repair system for strengthening an exemplary
fluid-system component in accordance with aspects of the present
disclosure.
[0025] FIG. 3 is a flow chart diagrammatically illustrating a
representative method of strengthening fluid-system components in
accordance with aspects of the present disclosure.
[0026] While this disclosure is susceptible to various
modifications and alternative forms, specific embodiments have been
shown by way of example in the drawings and will be described in
detail herein. It should be understood, however, that the invention
is not intended to be limited to the particular forms disclosed.
Rather, the invention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the
disclosure.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0027] While the invention is susceptible to various modifications
and alternative forms, specific embodiments have been shown by way
of example in the drawings and will be described in detail herein.
It should be understood, however, that the invention is not
intended to be limited to the particular forms disclosed. Rather,
the invention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims. To that extent, elements and
limitations that are disclosed herein, for example, in the
Abstract, Summary, and Detailed Description sections, but not
explicitly set forth in the claims, should not be incorporated into
the claims, singly or collectively, by implication, inference or
otherwise.
[0028] Referring now to the drawings, wherein like reference
numbers refer to like components throughout the several views, FIG.
1 illustrates an exemplary repair kit, designated 100, for
strengthening fluid-system components, FIG. 2 illustrates a
representative repair system, indicated generally at 200,
strengthening a fluid-system component, and FIG. 3 illustrates a
representative method 300 of strengthening fluid-system components.
The drawings presented herein are provided purely for instructional
purposes, and should therefore not be considered limiting. By way
of example, some of the description set forth herein may be made
with reference to the repair of a damaged pipe in a transmission
pipeline assembly intended for transporting any of an assortment of
fluids, such as water, oil, natural and synthetic gases, sewage,
slurry, hazardous materials, etc. However, the present invention
may be utilized in other pipeline assemblies, such as those housing
fiber optic wires, electrical cabling, etc, and other components.
In addition, the drawings presented herein are not to scale; thus,
the individual and relative dimensions shown in the drawings are
not to be considered limiting.
[0029] The repair kit 100, as exemplified in FIG. 1, is inclusive
of, but not exclusive to, a composite laminate 102, a radiation
device 104, an automated wrapping device 106, a power supply 108,
an optical measuring tool 110, and safety gloves 112. Additional
and/or alternative components can be included in the repair kit 100
without deviating from the intended scope of the present
disclosure. As will be developed further below, the composite
laminate 102 includes a fabric carrier fabricated, at least in
part, from a continuous reinforcing fiber. The fabric carrier is
pre-impregnated with a reactive precursor chemically configured to
activate upon exposure to artificial radiation. As used herein,
"pre-impregnated" can mean impregnated prior to the commencement of
the installation at the repair site. As some non-limiting examples,
the fabric carrier may be impregnated during fabrication at a
manufacturing plant, it may be impregnated after it leaves the
manufacturing plant but prior to transportation to the repair site,
it may be impregnated during transportation to the repair site,
and/or it may be impregnated at the repair site but prior to the
commencement of the installation process. In this vein, the
composite laminate 102 of FIG. 1 can take on any of the applicable
forms and alternative configurations, and include any of the
various optional features described herein with respect to
composite laminates of the present invention. Although shown as an
elongated flexible wrap wound into a roll, alternative arrangements
can include a composite laminate 102 in the form of a patch, a
number of patches, a frangible wrap separable into smaller
sections, and/or means for partitioning an elongated wrap into
smaller sections.
[0030] The repair kit 100 of FIG. 1 also includes a radiation
device 104 that is operable to apply artificial radiation to the
composite laminate at sufficient intensity to thereby activate the
reactive precursor. Applying radiation to the fabric carrier in
this manner activates and cures the reactive precursor, which
operates to create a load-bearing repair implement from the
composite laminate. The applied radiation may be in the form of
microwaves, ultraviolet rays, electron beams, x-rays, or
gamma-rays, or any combination thereof. As will be developed in
further detail below, the radiation device 104 may be configured to
generate an electron beam that, in some embodiments, possesses an
energy ranging from approximately 0.15-0.3 megaelectron volts
(MeV). The radiation device 104 may be in the form of a COMET.TM.
EBA-90, EBA-180 EBA-200 E-beam emitter, available from COMET
Technologies USA, Inc., of Stamford, Conn. Such electron beam
emitters are of the water-cooled, hermetically sealed metal ceramic
vacuum tube type. Options for the radiation device 104 can include
an active window length of approximately 270-400 mm, a voltage
range of approximately 70-200 kV, and a power range of
approximately 2 to 4 kW.
[0031] Also included in the repair kit 100 are an automated
wrapping device 106 and a power supply 108 for powering the
radiation device 104, the wrapping device 106, or both depending
upon individual requirements. The automated wrapping device 106 may
be in the form of an Eagle Powered Rap-Rite Wrapping machine, avail
able from Eagle Manufacturing and Field Services, Inc., of Tulsa,
Okla. In this instance, the wrapping device 106 can be
pneumatically or hydraulically powered, powered by a gasoline or
diesel engine, or powered via an electric motor, which in turn can
draw electricity from the power supply 108 which is represented
herein for illustrative purposes by a battery module. Alternative
power supplies, such as a gas-powered generator, are also within
the scope of the present concepts. The wrapping device 106 can be
provided with various optional features, including an optional
adjustable overlap control for changing the width of overlap,
preceding and trailing tape arms, a constant-tension tape brake, a
release-liner take-up mechanism, an adjustable break-open frame,
and the option to apply inner-wrap and outer-wrap in a single pass.
In some embodiments it may be desirable that the automated wrapping
device 106 include wheels or other mechanical means for mounting
the device 106 on a pipe, a loadable arm to create tension on and
hold a roll of composite laminate 102, and a pressure wheel or
blade to press layers of composite onto themselves.
[0032] The protective safety gloves 112 are adapted to be worn by a
user in the handling, preparation, and/or application of any
materials that may irritate the skin, which may be the case of a
flexible fiberglass composite wrap 102. The protective gloves 112
are preferably composed of latex, but can be composed of any
material that enables the protective gloves 112 to be used for
their intended purpose. An optical measuring tool 110 (or
"inspection eye") can also be provided as a means for checking to
ensure that the composite laminate 102 has properly cured after
exposure to radiation. The optical measuring tool 110 can be in the
form of a spectrophotometer or other colorimetric device, many
variations of which are available from Thermo Fisher Scientific,
Inc., and Ocean Optics, Inc.
[0033] Turning next to FIG. 2, wherein similar reference numerals
designate the same or similar components from FIG. 1, a repair
system 200 for strengthening a fluid-system component, such as a
transmission pipe 230, is shown in accordance with aspects of the
present disclosure. The repair system 200, as exemplified in FIG.
2, includes a composite laminate 202, a radiation device 204 for
activating and curing the composite laminate 202, an optical
measuring tool 210 for confirming the composite laminate 202 has
properly cured, and a pressure roller 220 for applying pressure to
the composite laminate 202 during the installation process. Each of
the foregoing may be similar in structure and operation to its
corresponding component from FIG. 1 or those described below with
respect to the other aspects and embodiments of the present
disclosure.
[0034] The roller 220, which may be part of or wholly separate from
the automated wrapping device 106 of FIG. 1, assists in applying
the pre-impregnated composite laminate 202 to the outer surface of
a pipe 230 or other component of the fluid system. As seen in FIG.
2, radiation device 204, which may be in the form of an
electron-beam gun, is located downstream from the pressure roller
204--i.e., at a location along the composite laminate 202 after the
laminate 202 is positioned against the pipe 230 and after pressure
is applied to the laminate 202 by the roller 220. The pressure
roller 204 operates to press the composite laminate 202 onto one or
more underlying layers of composite laminate 202, for example, to
assist in removing entrained air and/or water. Artificial radiation
is thereafter applied to the composite laminate 202 via the
radiation device 204 to activate and cure the reactive,
pre-impregnated precursor. As a quality measure, the optical
measuring tool 210 operates to check the resulting repair implement
for proper cure, defects, and/or other metrics of quality. In some
embodiments, a pigment-changing agent may be integrated into the
resin with which the fabric carrier of the composite laminate 202
is impregnated such that the optical sensor 210 can more easily
detect whether the is laminate 202 fully and properly cured as the
resin will change in color from before to after it has been exposed
to radiation. The repair system 200 may also include a blade to
press down on and/or apply tension to the composite laminate 202,
and perhaps a second radiation device or a supplemental thermal
curing device to cure the composite laminate 202 a second time.
[0035] The reactive precursor in the composite laminate 202 of FIG.
2 is chemically configured to activate and harden upon exposure to
artificial radiation. In some embodiments, reactive agent in the
composite laminate 202 is generally hydrophobic--i.e., tends not to
combine with and react to water, saline or other water-based
solutions. In some embodiments, the reactive precursor is designed
to activate in deep-water applications--e.g., water depths of
approximately 5-10,000 feet (1.5-3,048 meters), cold-zone
applications--e.g., temperatures of approximately -18-24.degree. C.
(0-75.degree. F.), or both. In some embodiments, the reactive
precursor is chemically configured to activate in water depths of
approximately 1-20,000 feet, water temperatures of approximately
-15.degree. C. and higher, or both. Activating the reactive
precursor creates a load-bearing repair implement, which may be
represented herein by the two-layer cured portion of the composite
230 to the right of the pressure roller 220 in FIG. 2. The
load-bearing repair implement, in some embodiments, exhibits a
tensile strength of approximately 103.42 to 1034.21 MPa (15,000 to
150,000 psi) (e.g., in at least one principal axis direction) and
an impact resistance of at least approximately 80 joules and, in
some embodiments, approximately 80-300 joules and, in some
embodiments, approximately 200-600 joules. In other embodiments,
the load-bearing implement formed from the composite laminate
exhibits a tensile strength of at least approximately 86.2
megapascal (MPa) (12,500 psi) in at least one principal axis
direction. In other embodiments, the load-bearing implement formed
from the composite laminate exhibits a tensile strength of at least
103.4 MPa (15,000 psi) in both principal axis directions. In yet
some other embodiments, the load-bearing implement formed from the
composite laminate exhibits a tensile strength of at least 206.8
MPa (30,000 psi) in at least one principal axis direction. In yet
some other embodiments, the load-bearing implement formed from the
composite laminate exhibits a tensile strength of at least 344.7
MPa (50,000 psi) in at least one principal axis direction.
[0036] The flowchart of FIG. 3 diagrammatically illustrates an
improved method 300 for strengthening a component in a fluid
system. In some specific embodiments, the flow chart of FIG. 3 can
be considered representative of a method for repairing a damaged
transmission pipe in a pipeline assembly. The method or algorithm
300 of FIG. 3 is described herein with respect to the embodiments
illustrated in FIGS. 1 and 2. However, the claimed methods are not
so limited. For example, the methods presented herein are not per
se limited to particular components of the repair kit 100 of FIG. 1
or the particular pipeline assembly 230 of FIG. 2. Likewise, use of
the word "step" or "act" in the specification or claims is not
intended to be limiting and should not be considered as
limiting.
[0037] The method 300 of FIG. 3 comprises four generalized steps,
which will be developed further in the description that follows.
These steps include: block 301: providing a composite wrap with a
fabric carrier pre-impregnated with a radiation-curable reactive
precursor; block 303: placing the composite wrap over a portion of
a fluid-system component; block 305: applying artificial radiation
to the composite wrap to activate and cure the wrap into
load-bearing repair implement; and block 307: inspecting the
composite wrap to ensure the reactive precursor properly cured. In
some embodiments, the method 300 includes at least those steps
enumerated in FIG. 3. It is also within the scope and spirit of the
present invention to omit steps, include additional steps, and/or
modify the order presented. It should be further noted that the
method 300 represents a single sequence of creating a single repair
implement. Nevertheless, it is expected that the method 300 be
practiced in a systematic and repetitive manner.
[0038] The composite laminates used in some implementations of the
present disclosure comprise a thermoset polymer matrix and a fabric
constructed from a continuous reinforcing fiber. Any reactive
precursor that can be cured into a thermoset polymer matrix may be
used, including, but not limited to, an epoxy, an epoxy acrylate,
an imide, a bismaleimide, an acrylate, a urethane, a urethane
acrylate, a urea, an unsaturated ester, a vinyl ester, a cyanate
ester, a phenolic, or a mixture thereof; formulated to be
susceptible to curing upon applying radiation.
[0039] Other desired attributes of the reactive precursor depend,
for example, on the application environment. As a non-limiting
example, for a broad range of underwater steel pipeline repair
applications, a desirable reactive precursor can be (a) resistant
to the activation of its cure by water; (b) insoluble in water; (c)
radiation-curable at temperatures as low as -10.degree. C.
(14.degree. F.); and (d) once in its cured form, capable of
providing the resulting load-bearing composite laminate with good
adhesion to steel underwater as measured by a lap shear strength of
at least approximately 4 MPa (580 psi). Optionally, the reactive
precursor can be chemically configured to activate in a water
pressure of approximately 0.015 to 30.34 MPa (2.2 to 4,400
psi).
[0040] Some non-limiting examples of the types of reactive
precursors that may be used include those described in the
following (all of which are hereby incorporated by reference herein
in their respective entireties): (a) J. N. Hay and P. O'Gara,
"Recent Developments in Thermoset Curing Methods", Proc. ImechE
Vol. 220 Part G: J. Aerospace Engineering, pages 187-195, 2006; (b)
Cytec Industries Inc. of Woodland Park, N.J. sells several product
lines of resins and specialty additives for use in ultraviolet
and/or electron beam curing formulations, such as EBECRYL.TM.
resins and oligomers, UCECOAT.TM. waterborne resins, RAYLOK.TM.
resins, and ADDITOL.TM. photoinitiators and additives; EBECRYL.TM.
3701 (a modified bisphenol-A epoxy diacrylate) and EBECRYL.TM. 8808
(an aliphatic urethane diacrylate) are two specific, non-limiting
examples of Cytec's commercially available radiation-curable
formulations; and (c) the Sartomer Company of Exton, Pa., sells
many ultraviolet and/or electron beam curing formulations,
including, as some specific non-limiting examples, CN112C60 (a
trifunctional epoxy novolacacrylate blended with 40% SR351,
trimethylolpropane triacrylate), CN117 (a modified epoxy acrylate),
CN120 (an epoxy acrylate), and SR833S (a tricyclodecane dimethanol
diacrylate). Additionally, Adherent Technologies, Inc. of
Albuquerque, N. Mex., has developed formulations that can cure
rapidly under irradiation even in space which is much colder than a
deepwater environment. These formulations include hybrid resin
systems that combine free radical and cationic curing mechanisms in
a synergistic manner. Resins have also been formulated that will
cure optimally at specific desired wavelengths (and hence at
specific desired frequencies and energies) of irradiation.
Furthermore, Adherent has also developed a special tape dispenser
system, similar in concept to 35-mm photographic film canisters, as
a simple dispensing system to minimize the risk of the accidental
light exposure of a radiation-curable resin formulation. Some of
this work is described by R. E. Allred, A. E. Hoyt Haight and T. F.
Wesley, "Light-Curing Structural Tape for In-Space Repair",
Proceedings of the 39th ISTC Conference, Cincinnati, Ohio, Oct.
29-Nov. 1, 2007, which is also incorporated by reference herein in
its entirety.
[0041] A reactive precursor formulation may optionally comprise
additional ingredients or additives, such as, but not limited to,
an impact modifier, a fire retardant, an antioxidant, a
photoinitiator, a catalyst, an inhibitor, a buffer, a dispersant, a
surfactant, a stabilizer, a compatibilizer, a rheology modifier, a
defoamer, or any combination(s) thereof.
[0042] Many types of continuous reinforcing fiber may be used for
the fabric carrier of the composite laminate, including, but
certainly not limited to, a glass fiber, a carbon fiber, a basalt
fiber, an aramid fiber, a polyolefin fiber, any other type of
synthetic polymer fiber, a fiber obtained or derived from a plant
product, a fiber obtained or derived from an animal product, or any
combination(s) thereof; arranged in a uniaxial orientation, a
biaxial orientation, or any combination(s) thereof. Different plies
of a composite laminate may contain the same type of fiber (such as
carbon fibers) or different types of fibers (such as glass fibers
in the ply bonded to the surface of the fluid system component and
carbon fibers in the other plies). The fibers in different plies of
a composite laminate may be oriented in the same manner or they may
be oriented in different ways.
[0043] The implementation of certain embodiments of the present
disclosure comprises a step of curing a reactive precursor by
applying radiation, wherein the radiation may comprise, but is not
limited to, microwaves, ultraviolet rays, an electron beam, x-rays,
gamma-rays, or any combination(s) thereof.
[0044] The choice of which type or types of radiation to be used
can depend on factors such as, but not limited to, the penetration
depth of the radiation, as well as the availability, cost, safety,
and ease of use of suitable equipment. The maximum attainable
penetration depth increases as the energy of the radiation
increases, being greatest with x-rays (up to approximately 12
inches) and least with ultraviolet rays (up to approximately 0.8
inches) among the alternatives of ultraviolet irradiation, electron
beam irradiation, and x-ray irradiation. On the other hand, in
general, the availability, cost, safety, and ease of use of
suitable equipment increases as the energy of the radiation
decreases, usually being greatest with ultraviolet rays and least
with x-rays among the alternatives. In the case of curing by using
ultraviolet radiation, the need for the optical transparency of the
material that will be cured to allow penetration can imposes a
challenge to the curing of a composite where carbon fibers, which
lack optical transparency, have been used constructing in the
reinforcing fabric. Electron beam curing (with a penetration depth
of up to approximately 2 inches) often provides an optimum or
desirable balance between these factors.
[0045] While the penetration depth is related mainly to the energy
of the radiation, the curing rate (and hence the curing time) is
controlled mainly by the dose rate (defined as the amount of
radiation absorbed per unit time). The penetration depth and the
curing rate are hence not in lockstep with each other. They can be
varied independently to a significant extent to optimize a curing
process. For example, at a fixed energy of radiation intended to
achieve a desired penetration depth, the curing rate can be
modified by selecting resin formulations comprising unreacted
resins of differing molecular structure, photoinitiators of
differing molecular structure, photoinitiators at differing
concentrations, or any combination(s) thereof.
[0046] An advantage of using radiation-curable resin formulations
in terms of storage, handling, and transport can include that,
unlike a resin formulation intended to be cured thermally, there is
no need for a radiation-curable resin formulation to be thermally
labile. In addition, unlike a resin formulation intended to undergo
moisture-activated curing, there is no need for a radiation-curable
resin formulation to be labile in the presence of water. On the
other hand, some radiation-curable resin formulations may begin
curing if exposed to ultraviolet light, so that their exposure to
sunlight may need to be minimized during storage, handling, and
transport.
[0047] A processing advantage of radiation curing is that it can
help achieve rapid curing even at very low temperatures, such as
water temperatures as low as approximately -10.degree. C.
(14.degree. F.), that may be encountered in some deep saltwater or
cold environment applications because of the effect of the
dissolved salt on the freezing temperature of water. By way of
contrast, the energy-intensive nature of thermal curing (in other
words, the fact that often a large amount of thermal energy must be
provided to increase the temperature to the level that will enable
the acceptably rapid cure of a typical thermally-curing resin)
introduces practical difficulties that are very difficult to
overcome in cold and/or water-submerged environment(s).
[0048] The performance of a thermally-cured composite is often
limited by residual stresses introduced during "cool down" from a
high temperature after cure as a result of mismatches of thermal
expansion coefficients. For example, a thermal expansion
coefficient difference between a thermoset polymer matrix and a
fabric may create residual stresses within a composite laminate. In
addition, a difference in thermal expansion coefficient between a
composite laminate and a fluid system component onto which the
laminate has been applied may create residual stresses between the
composite laminate and the fluid system component. An advantage of
a radiation-cured composite compared with a similar thermally-cured
composite is the buildup of less residual stress since there is no
need to cool down from a high temperature after cure.
[0049] A potential disadvantage of some radiation-cured composites
compared with similar thermally-cured composites is that radiation
curing sometimes results in poor fiber-matrix adhesion. Poor
fiber-matrix adhesion may result in lower performance
characteristics (such as a lower strength), especially in the
weaker transverse direction of a composite laminate where the fiber
orientation is not biaxially symmetric. Some approaches that may be
used to overcome this challenge can include, singly and in any
combination: careful optimization of the radiation curing process
conditions; use of fibers that have been specially surface-modified
to enhance their adhesion to the radiation-cured thermoset polymer
matrix; and, use of a thermal postcure step to further the extent
of cure by enhancing molecular mobility.
[0050] If it is desired that the extent of curing is to be driven
further than can be achieved readily by means of radiation curing,
a moderate thermal postcure can be applied and may be preferred to
the use of a very high radiation dose rate and total dose to induce
a very large exotherm. In this context, the "exotherm" refers to
the thermal energy (heat) released as a result of the curing
reactions that are taking place. Such an exotherm can be measured
by using standard techniques of material testing, such as but not
limited to differential scanning calorimetry. A very large
exotherm, however, can induce an uncontrollable runaway reaction as
it overheats the reacting system while inducing thermal cure
simultaneously with the radiation cure. This can potentially lead
to reduced and highly variable and hence unpredictable cured
composite laminate properties. Consequently, a thermal postcure
step can be useful to help achieve higher quality than non-postcure
methods by obtaining full composite laminate material properties in
a reliable manner. When a thermal postcuring step is used, it is
typically sufficient to impose a heat exposure profile which allows
for significantly lower temperatures and/or significantly shorter
durations than would be required to achieve a similar extent of
cure starting from a similar uncured resin formulation via thermal
curing by itself. As a non-limiting illustrative example, a
composite laminate that requires thermal curing at a temperature of
80.degree. C. (176.degree. F.) for four hours to reach a Shore D
hardness level of 75, if it has been first cured via radiation, may
instead be able to reach the same Shore D hardness level of 75
after postcuring for just one hour at a temperature of 45.degree.
C. (113.degree. F.) or after postcuring for just fifteen minutes at
temperature of 60.degree. C. (140.degree. F.).
[0051] Field installations of certain embodiments may include
equipment suitable for the safe and efficient installation and
radiation-induced curing of a composite laminate. In one
non-limiting example for deepwater repairs, completely automated
(robotic) methods can be used for a "diverless" installation of a
composite laminate by using equipment and supplies transported to
the repair site via a remotely operated vehicle (ROV). In practical
implementations of such methods, another possible role for an ROV
(beyond its use in transporting equipment and supplies to a repair
site) is its use for the installation and/or curing of a composite
laminate. In any particular field installation, an ROV may be used
for transporting equipment and supplies to the repair site, for
installing a composite laminate, for the radiation-induced curing
of the composite laminate, or any combination thereof.
[0052] In another example, for coastal or shallow water repairs, it
is possible to choose between using completely automated or
semi-automated methods, deploying personnel (for example, one or
more divers) to a repair site to install an uncured composite
laminate and then use portable radiation curing equipment to cure
it, or using a partially automated, partially manual approach. In a
similar regard, for above ground repairs, such as repairs at
exceedingly cold locations, it is possible to choose between using
completely automated methods, deploying personnel to the repair
site to install an uncured composite laminate and use portable
radiation curing equipment to cure it, or using a partially
automated, partially manual approach.
[0053] The development of radiation-curable composite laminates
that are easier to install than thermally-curing or
moisture-activated curing composite laminates in many environments
is anticipated to expand greatly the applications of composite
repair systems in strengthening fluid system components. As a
non-limiting example, in deepwater pipeline repair applications,
the installation of a radiation-curable composite laminate can
avoid or minimize some or all of the key limitations of
thermally-curing composite laminates (need to often use
impractically high temperatures to achieve an acceptable level of
cure at an acceptable rate) and moisture-activated curing composite
laminates (tendency to cure prematurely upon exposure to the water
in which the pipeline is submerged).
[0054] Some exemplary embodiments will be described below purely to
facilitate the teaching and understanding of the present
disclosure. With the help of these examples and other corresponding
sections of this disclosure, persons skilled in the art to which
the present disclosure pertains can readily imagine many additional
embodiments that fall within the scope as taught herein.
[0055] A reactive precursor to a composite laminate comprises a
glass fabric, a carbon fabric, or a combination(s) thereof; the
fabric comprising continuous fibers; wherein a fiber alignment in
the fabric may comprise a uniaxial orientation, a biaxial
orientation, or any combination(s) thereof; and the fabric can be
pre-impregnated with an electron beam curable resin
formulation.
[0056] Many of the applications where using an electron beam cured
composite laminate for strengthening a fluid system component may
provide significant commercial opportunities involving fluid system
components located in cold environments, such as, but not limited
to, deepwater locations and cold (e.g., below freezing)
above-ground locations. In this context, a cold environment can be
defined to mean an environment where the temperature does not
exceed approximately 10.degree. C. (50.degree. F.) during the
curing period. Many additional significant commercial opportunities
where using an electron beam cured composite laminate for
strengthening a fluid system component may provide significant
value can, however, also be envisioned in shallow water locations
and/or coastal locations that may or may not be cold, and above
ground locations that are not cold, i.e., >10.degree. C.
(50.degree. F.).
[0057] In many embodiments, a reactive precursor is formulated to
cure sufficiently rapidly at a very low temperature upon applying
an electron beam, while the maximum use temperature of a cured
composite laminate does not need to be especially high. As a
non-limiting example, a maximum use temperature of 20.degree. C.
(68.degree. F.) is sufficient for use in some, a maximum use
temperature of 40.degree. C. (104.degree. F.) is sufficient for use
in many, a maximum use temperature of 60.degree. C. (140.degree.
F.) is sufficient for use in most, and a maximum use temperature of
80.degree. C. (176.degree. F.) is sufficient for use in almost all,
of the currently envisioned applications.
[0058] Many envisioned applications involve the use of a composite
laminate in an environment where it is exposed to (or even
submerged entirely in) water. The cured composite laminate of an
embodiment targeted for use in such an application must have
sufficient water resistance to be able to manifest its targeted
maximum use temperature in such an environment.
[0059] An exemplary uncured resin formulation may comprise an
epoxy, an epoxy acrylate, or a mixture thereof, optimized to cure
via electron beam irradiation in an application environment and
provide a cured composite laminate possessing a targeted maximum
use temperature.
[0060] In some embodiments, electron beam irradiation can be used
to cure a reactive precursor. D. L. Goodman and G. R. Palmese
provide some background information on electron beam irradiation in
"Curing and Bonding of Composites Using Electron Beam Processing",
in C. Vasile and A. K. Kulshreshtha (editors), Handbook of Polymer
Blends and Composites, Volume 1, Shawbury, Rapra Technology Ltd.,
2002, pages 459-499, which is hereby incorporated by reference
herein in its entirety.
[0061] Depending on many variables, such as uncured resin molecular
structure, use of ingredients, such as photoinitiators, and/or
curing conditions, one or any combination of four types of
polymerization chemistries may occur in curing via electron beam
irradiation: (1) free radical mechanisms usually dominate in
polymerizing acrylic/methacrylic systems; (2) cationic mechanisms
aided by photoinitiators usually dominate in polymerizing epoxies;
(3) thermal polymerization of a first network under moderate heat
exposure followed by electron beam curing of a second network
around the first network is typical in the formation of
interpenetrating networks; and (4) a reactive precursor mixture
comprising two or more types of unreacted resins that cure at very
different rates and/or with differing mechanisms under electron
beam irradiation may be used to form an interpenetrating network
without needing the use of a thermal polymerization step.
[0062] A moderate thermal postcure step may be applied after
electron beam curing to advance the extent of curing of the
thermoset network and/or to enhance fiber-matrix adhesion. In this
context, the term "moderate thermal postcure step" is defined as a
process step performed after curing a formulation via electron beam
irradiation, the step utilizing a lower temperature and/or a
shorter duration than would be required to cure the same resin
formulation thermally.
[0063] A fabric pre-impregnated with an unreacted resin formulation
can be rolled up and placed inside a hermetically sealed pouch that
is both non-transparent and non-translucent to minimize and/or
protect it from curing prematurely as a result of accidental
exposure to environmental factors, including but not limited to
sunlight; during storage, handling, and transport.
[0064] In some embodiments, the fabric is unrolled and wrapped
around a circumference of a fluid system component, and the resin
formulation is cured to obtain a composite laminate. In some
embodiments, the fabric is placed as a patch over a portion of a
fluid system component, and the resin formulation is cured to
obtain a composite laminate. In some embodiments, the fabric is
removed from its packaging and, where applicable, unrolled or
unfolded for partitioning into smaller sections for application as
a patch or wrap of a component with a smaller periphery.
[0065] Curing via electron beam irradiation can be performed in a
layer-by-layer manner in many embodiments, as a fabric that has
been pre-impregnated with an unreacted resin formulation is either
being wrapped around a circumference of or being placed as a patch
over a portion of a fluid system component. The scope of this
disclosure is not limited by stipulating the use of multiple layers
and/or by requiring that the curing be performed one layer at a
time. For example, other useful, non-limiting, embodiments can be
envisioned where the utilization of two layers or even just a
single layer may be sufficient. As another example, yet other
useful embodiments can be envisioned where one or two passes of an
electron beam irradiation instrument may be sufficient to provide
the extent of cure needed for a particular application.
[0066] For deepwater repairs, completely automated (robotic)
methods can be used, for example, in diverless installations or
diver-assisted installations of an uncured composite laminate by
using equipment and supplies transported to a repair site via a
remotely operated vehicle (ROV). In practical implementations of
such methods, another possible role for an ROV (beyond its use in
transporting equipment and supplies to a repair site) is for the
installation and/or curing of a composite laminate. In any
particular field installation, an ROV may be used for transporting
equipment and supplies to the repair site, for installing a
composite laminate, for the radiation-induced curing of the
composite laminate, or any combination(s) thereof.
[0067] For coastal or shallow water repairs, the alternatives of
(a) using completely automated or semi-automated methods, (b)
deploying personnel (for example, one or more divers) to a repair
site to install an uncured composite laminate and then use portable
electron beam curing equipment, or (c) using a partially automated
approach with the help of one or more divers, are all feasible in
principle. But, it is possible to make choices between them by
considering some general constraints whose implications depend on
the circumstances of a specific installation. For instance, the
radiation dose absorbed by an electron beam curing system may
depend strongly on the distance of the electron gun from the
surface of the laminate (unless highly energetic electrons are
used, which is usually an undesirable approach because of factors
related to increased cost, reduced safety, and potentially lower
cured composite laminate quality), its angle, and the speed and
detailed mode with which it is being moved. These variables often
need to be controlled to within tight tolerances. A. N. Bykanov, D.
L. Goodman, C. A. Byrne, L. G. Bykanova, T. W. Pond, L. R.
Vorobyev, W. M. McMahon, and M. P. Kovach provide some relevant
information in "Automated Tape Placement with In-situ Electron Beam
Cure: Process Parameters Optimization", International SAMPE
Symposium and Exhibition, 47 (Affordable Materials Technology:
Platform to Global Value and Performance, Book 2), pages 902-918,
2002, which is hereby incorporated by reference herein in its
entirety, provides examples of the effects of several key
parameters on the effectiveness of the curing process.
Consequently, even when feasible, the use of a hand-held electron
gun by a field technician is a feasible, but perhaps not an optimum
approach as it leaves too much room for quality problems caused by
technician errors. An additional practical difficulty with the use
of a hand-held electron gun by a field technician is that the
technician(s) would need to carry portable (but very cumbersome and
heavy) concrete blocks or lead slabs with them for shielding to
implement such an approach safely. For example, for a low energy
(0.15 MeV to 0.3 MeV) electron beam system that can be used to cure
a composite laminate layer-by-layer, typical x-ray shielding
requirements are the use of a lead slab thickness of approximately
2 to 6 cm or a concrete block thickness of approximately 10 to 30
cm. Because of all of these considerations, even when an
installation approach deploying one or more divers is being used,
electron beam curing of a composite laminate is oftentimes
performed in an automated manner.
[0068] For above ground repairs, it is possible to choose between
using completely automated methods, deploying personnel to a repair
site to install an uncured composite laminate and then use portable
radiation curing equipment to cure it, or using a partially
automated approach with the help of one or more workers. However,
for the same reasons as for coastal or shallow water repairs, also
for above ground repairs, even when an installation approach
deploying one or more workers is being used, electron beam curing
of a composite laminate is usually performed in an automated or
semi-automated manner. As a non-limiting example, workers can use a
tape wrapping tool to which an electron gun can be attached. In so
doing, the field technicians may be in close proximity to the pipe
and the tape wrapping operation.
[0069] As the applications of portable radiation curing equipment
expand, the development of such equipment as well as its
customization for more effective use in specific applications are
continuing to be pursued actively by instrument manufacturers.
COMET AG (with headquarters in Switzerland) and Advanced Electron
Beams (with headquarters in Wilmington, Mass., USA) are two
non-limiting examples of portable electron beam curing equipment
vendors.
[0070] Implementations intended for use in different application
environments may require different customized instrument
configurations. For example, some electron beam emitters that are
currently available commercially cannot withstand immersion in
water. They must, therefore, be protected from exposure to water
during use in underwater application environments. Without limiting
the generality of this disclosure, in some exemplary embodiments,
an electron beam emitter that is incapable of withstanding
immersion in water is placed within a protective enclosure that can
be transported to an underwater repair site, for example, via an
ROV, and possesses a window or other structure constructed from a
material that allows an electron beam to pass therethrough.
[0071] Automated tape placement with "in-situ" layer-by-layer,
low-energy electron beam curing can be used as a relatively cheap,
safe, and reliable approach for the fabrication of large and
complex composite parts in a reproducible manner. The typical
electron beam energy used in implementations of this approach
ranges from approximately 0.15 MeV to 0.3 MeV since there is no
need for an electron beam to penetrate to a great depth. A. N.
Bykanov, D. L. Goodman, C. A. Byrne, L. G. Bykanova, T. W. Pond, L.
R. Vorobyev, W. M. McMahon, and M. P. Kovach provide some relevant
information in "Automated Tape Placement with In-situ Electron Beam
Cure: Process Parameters Optimization", International SAMPE
Symposium and Exhibition, 47 (Affordable Materials Technology:
Platform to Global Value and Performance, Book 2), pages 902-918,
2002.
[0072] A version of this approach, which is modified to overcome
some major practical difficulties encountered in field
implementations of electron beam curing for composite laminates of
varying shapes and sizes wrapped around or placed as a patch over
fluid system components of varying shapes and sizes located in many
different types of environments, is used in exemplary embodiments
of the present disclosure. For example, different field
implementations may need to be performed in environments including,
but not limited to, a deep water location, a coastal location,
shallow water, or above ground. The repair design may require the
circumferential wrapping and curing of different numbers of layers
of a pre-impregnated fabric extended to different axial extents
beyond the damaged region. The repair design may require the
placement of a composite laminate patch and curing of different
numbers of layers of a pre-impregnated fabric extended to different
extents beyond the damaged region. The repair design may also
require doing so on fluid system components of different shapes,
diameters, and surface curvatures. Each composite repair system can
have its own design. Economic considerations may require the
hardware and software utilized in automation (robotics) equipment
intended for use in such field implementations to be sufficiently
versatile to allow the use of the same equipment for a wide range
of such repairs. Such versatility can be accomplished, for example,
by having both hardware of sufficient agility to be able to execute
the necessary motions precisely under greatly differing
circumstances and control software of sufficient sophistication to
allow the motions to be programmed and controlled for execution
with precision. Such aspects are not expected to arise in factory
implementations of electron beam curing for the repeated
manufacture of aerospace composite parts of fixed shapes and sizes
in a highly controlled environment.
[0073] Some exemplary embodiments of the present disclosure may be
selected to be manufactured for commercial use in applications
where a fabric pre-impregnated with a reactive precursor is wrapped
around a fluid system component before being cured into a
load-bearing composite laminate. Optionally, these embodiments may
be qualified formally for commercial use in high risk applications
by being shown to meet the criteria stipulated in the current
version of ASME, Repair of Pressure Equipment and Piping, Part 4
(Non-Metallic and Bonded Repairs), Article 4.1, "Non-Metallic
Composite Repair Systems: Risk Applications". Some embodiments may
be selected to be manufactured for commercial use in applications
where a fabric pre-impregnated with a reactive precursor is placed
as a patch over a fluid system component before being cured into a
load-bearing repair implement. A committee of the American Society
of Mechanical Engineers is currently developing a qualification
standards document for repairs using composite laminates as
patches. These embodiments may be qualified formally by being shown
to meet the criteria stipulated in the version of the standard that
is in effect as of the date of completion of their development. In
this context, the "successful development" of a standards document
is defined as the formal approval of the document by the ASME so
that it becomes one of the official standards documents published
by the ASME.
Description of Representative Samples
A. Exemplary Experimental Work
[0074] In some experimental applications, electron beam curing was
performed of Cytec's EBECRYL.TM. 3701 and EBECRYL.TM. 8808 resin
formulations and of pre-impregnated laminates containing these
resin formulations, both in a dry environment and under water, at
the facilities of E-BEAM Services, Inc., Lebanon, Ohio, USA.
[0075] A Dynamitron electron beam particle accelerator, which was
originally developed by IBA Industrial (formerly Radiation
Dynamics), operated at 150 kW, 4.5 MeV, was used for electron beam
curing. Irradiation was performed at a dose rate of approximately
1.1 MR/sec. The distance from the exit of the instrument window to
a sample being cured was approximately 50 inches (127 cm). Far West
Technology FWT-60 radiachromic dosimeters (heat-sealed in a foil
pouch to protect them from water) were used to monitor the
radiation dose. A FWT-100 spectrometer was used to measure the dose
at a wavelength setting of 510 nm. In curing experiments performed
under water, the depth of the water layer was approximately 0.8 cm
(0.315 inches).
[0076] The resin formulations cured in a dry environment and the
resin formulations cured under water were all found to be
well-cured as indicated by their high Shore D hardness values (see
examples below).
[0077] Samples of a hybrid bidirectional fabric (11 ends/inch, 8
picks/inch, 0.030 inch thickness, 16.0 oz/yd.sup.2 weight per unit
area, black carbon 12 k fiber in warp direction, white E-glass K 18
517 fiber in weft direction) were impregnated with the resin
formulations to prepare a pre-impregnated composite laminate (or
"prepreg"). In some embodiments, the warp and weft directions of
the fabric are perpendicular to each other; one or both of these
directions can define a principal axis direction of the fabric. The
electron beam curing of both prepregs placed in a dry environment
and prepregs placed under water was found to produce composites
possessing excellent tensile properties (see examples below).
B. Exemplary Electron Beam Curing of Resin Formulations in Dry
Environments and Under Water Environments
[0078] The purpose of the first experiment was to assess the
electron beam curing characteristics of the resins, both in a dry
environment and underwater.
[0079] The two resin formulations were poured on dry flat steel
plates. One of the dry steel plates with the resin formulations on
top of it was kept dry while the other dry steel plate with the
resin formulations on top of it was then submerged in water. An
electron beam was then applied with a 2.5 MR surface dose at 4.5
MeV. A dosimeter placed on the dry steel plate measured 2.8 MR
while a dosimeter placed on the underwater steel plate measured 3.1
MR, indicating that submersion in water had amplified the exposure
slightly relative to the use of a dry environment. The surface dose
dosimeter measured 2.5 MR on the cart conveyor (a dry environment)
as expected. It is envisioned that the slightly higher (2.8 MR)
reading on the dry steel plate is most likely caused by a
combination of the backscattering of electrons when they impinge
upon the steel plate and the generation of X-rays when the
electrons hit the steel.
[0080] The resin temperatures after one pass of electron beam
irradiation were 100.degree. F. on the dry plate and 75.degree. F.
on the plate submerged in water. The Shore D hardness, measured in
accordance with ASTM D2240, "Standard Test Method for Rubber
Property--Durometer Hardness", by using a Pencil Style Durometer
Model 202 Type Dfrom PTC Metrology, ranged from 68 to 84 (TABLE 1),
showing that the resins had been cured successfully.
[0081] After applying a second pass of 2.5 MR electron beam
irradiation, the resin temperatures were 128.degree. F. on the dry
plate and 82.degree. F. on the plate submerged in water. The Shore
D hardness (TABLE 2) had not changed significantly as a result of
the application of the second pass of irradiation, providing
further confirmation that the resins had been well-curedin the
first pass. Three measurements were made for each resin cured in
each type of environment.
TABLE-US-00001 TABLE 1 Shore D hardness values of EBECRYL .TM. 3701
and EBECRYL .TM. 8808 resin formulations placed on steel plates and
cured (in a dry environment and under water) with a single pass of
electron beam irradiation. EBECRYL .TM. EBECRYL .TM. EBECRYL .TM.
8808 3701 8808 EBECRYL .TM. 3701 (cured (cured (cured dry) (cured
dry) underwater) underwater) 79 79 68 80 80 84 70 79 79 79 68
82
TABLE-US-00002 TABLE 2 Shore D hardness values of EBECRYL .TM. 3701
and EBECRYL .TM. 8808 resin formulations placed on steel plates and
cured (in a dry environment and under water) with two passes of
electron beam irradiation. EBECRYL .TM. EBECRYL .TM. EBECRYL .TM.
8808 3701 8808 EBECRYL .TM. 3701 (cured (cured (cured dry) (cured
dry) underwater) underwater) 68 83 79 85 72 83 78 85 72 83 79
85
C. Exemplary Electron Beam Curing of Composite Laminates in Dry
Environments and Under Water Environments
[0082] A surface dose of 1.75 MR was selected for use in
layer-by-layer composite laminate curing experiments based on the
results of the first experiment summarized above. The rationale
behind the selection of this surface dose, which is smaller than
the surface dose of 2.5 MR that had been used in curing the resins
poured on steel plates, was that subsequent passes of electron beam
irradiation would deliver additional radiation doses to the lower
layers when the layers of the prepreg are placed one at a time and
an additional pass of electron beam irradiation is applied as each
new layer is placed.
[0083] The impregnation of the fabric with the resin formulations
was performed with the help of a mild amount of heating (so that
the resin temperatures remained below 130.degree. F. as measured by
an infrared thermometer) to facilitate impregnation by reducing the
resin viscosities.
[0084] Two different layer-by-layer electron beam curing trials
were performed (curing in a dry environment, curing under water)
for prepregs containing each resin formulation (EBECRYL.TM. 3701,
EBECRYL.TM. 8808), resulting in a total of four "layer-by-layer"
trials. Note: the prepregs used in the curing trials in a dry
environment were placed under a pan filled slightly with water in
an attempt to simulate the radiation doses of samples cured
underwater. In order to accomplish layer-by-layer curing, one strip
of the impregnated fabric was smoothed against a steel plate and
folded over the edges. It was then sent under the electron beam to
receive a 1.75 MR surface dose at 4.5 MeV. After this first layer
was cured under the electron beam, a second layer was placed over
the first layer, and the curing at 1.75 MR was repeated. This step
was repeated two more times to achieve a total of four layers. A
dosimeter placed on the steel plate underwater measured 2.4 MR and
a dosimeter placed under the pan of water on the dry steel plate
measured 1.8 MR. Surface doses measured by dosimeters placed during
each pass averagedat 1.75 MR.
[0085] A final trial using EBECRYL.TM. 8808 as the resin
formulation and four layers of fabric placed all at once and cured
all at once via electron beam irradiation was also performed, for
comparison with the layer-by-layer curing trials. The surface dose
was 2.5 MR during the first pass of electron beam irradiation. A
second pass of irradiation at a surface dose 1.75 MR was then
performed, to make sure that this 4-layer composite with the layers
being cured all together was cured completely. This trial was
performed in a dry environment; and furthermore, without a pan of
water above the sample, so that the sample was placed directly
under the beam.
[0086] The results of measurements performed, in the direction
parallel to the carbon fibers, in accordance with ASTM D3039,
"Standard Test Method for Tensile Properties of Polymer Matrix
Composite Materials", by using an ADME TeXpert 2613 Dual Column
Universal Testing Machine (10000 lb load cell capacity), are listed
in TABLE 3. It is seen that these five electron beam cured 4-layer
composites all possess excellent tensile properties.
[0087] Upon examining the data shown in Table 3 more closely, the
following trends can be discerned: (a) In layer-by layer curing
using each resin, curing dry results in a higher Young's modulus, a
higher ultimate tensile strength, and a lower ultimate tensile
strain than curing under water. (b) In layer-by-layer curing in
each type of environment, using EBECRYL.TM. 3701 as the resin
formulation results in a higher Young's modulus and a higher
ultimate tensile strength than using EBECRYL.TM. 8808 in the same
type of environment. (c) For the composites using EBECRYL.TM. 8808
as the resin formulation and being cured dry, curing all four
layers together provides enhancements in Young's modulus, ultimate
tensile strength, and ultimate tensile strain.
TABLE-US-00003 TABLE 3 Results of tensile elongation measurements
in a direction parallel to the carbon fibers, for electron beam
cured 4-layer composite laminates where a hybrid bidirectional
fabric woven by using a carbon fiber in one direction and a glass
fiber in the other direction was impregnated with the indicated
Cytec resin formulation and then cured either while being kept in a
dry location or under water. How Curing Young's Ultimate Tensile
Ultimate Tensile Resin Formulation Was Done Modulus, msi Strength,
psi Strain, % EBECRYL .TM. 8808 dry, 3.026 .+-. 0.726 55304 .+-.
2560 1.246 .+-. 0.22 layer-by-layer EBECRYL .TM. 8808 underwater,
2.687 .+-. 1.19 50429 .+-. 3085 2.56 .+-. 1.42 layer-by-layer
EBECRYL .TM. 8808 dry, all layers 3.412 .+-. 1.84 59043 .+-. 2206
1.56 .+-. 0.46 cured together EBECRYL .TM. 3701 dry, 4.903 .+-.
0.762 69962 .+-. 4966 1.42 .+-. 0.49 layer-by-layer EBECRYL .TM.
3701 underwater, 4.133 .+-. 2.172 58718 .+-. 4650 1.59 .+-. 0.33
layer-by-layer
Additional Features, Alternatives, and Embodiments
[0088] Presented hereinbelow are an array of additional and
optional embodiments and variations that fall within the scope and
spirit of the present disclosure. The variants discussed
hereinafter are not intended to represent every embodiment, or
every aspect, of the present invention, and should therefore not be
construed as limitations. Further, the following variants and
embodiments may be used in any combination or subcombination not
logically prohibited. By way of example, the following variants are
described with respect to methods, kits, and alternatives thereof;
nevertheless, the following features may be similarly applicable to
any of the disclosed system embodiments, method embodiments, and
kit embodiments of the present invention.
[0089] One embodiment may be directed to a method, or kits
including composite repair materials and equipment for implementing
the method, for strengthening a fluid system component by
installing a composite repair system, the method comprising: (a)
transporting to the location of the fluid system component a fabric
constructed from a continuous reinforcing fiber, wherein the fabric
is pre-impregnated with a reactive precursor; (b) unrolling the
fabric and wrapping it around the fluid system component; and (c)
applying radiation to cure the reactive precursor to obtain a
load-bearing composite laminate comprising the fabric in a
thermoset polymer matrix.
[0090] One embodiment may be directed to a method, or kits
including composite repair materials and equipment for implementing
the method, for strengthening a fluid system component by
installing a composite repair system, the method comprising: (a)
transporting to the location of the fluid system component a fabric
constructed from a continuous reinforcing fiber, wherein the fabric
is pre-impregnated with a reactive precursor; (b) unrolling the
fabric and placing it as a patch over a portion of the fluid system
component; and (c) applying radiation to cure the reactive
precursor to obtain a load-bearing composite laminate comprising
the fabric in a thermoset polymer matrix.
[0091] The reactive precursor may comprise an epoxy, an epoxy
acrylate, an imide, a bismaleimide, an acrylate, a urethane, a
urethane acrylate, a urea, an unsaturated ester, a vinyl ester, a
cyanate ester, a phenolic, or any mixture(s) or combination(s)
thereof.
[0092] The reactive precursor may comprise an epoxy, an epoxy
acrylate, or any mixture(s) or combination(s) thereof.
[0093] The reactive precursor may comprise an additional ingredient
selected from the group consisting of an impact modifier, a fire
retardant, an antioxidant, a photoinitiator, a catalyst, an
inhibitor, a buffer, a dispersant, a surfactant, a stabilizer, a
compatibilizer, a rheology modifier, a defoamer, or any
combination(s) thereof.
[0094] The fiber may be selected from the group consisting of a
glass fiber, a carbon fiber, a basalt fiber, an aramid fiber, a
polyolefin fiber, a synthetic polymer fiber, a fiber obtained or
derived from a plant product, a fiber obtained or derived from an
animal product, or any combination(s) thereof.
[0095] The fiber may be selected from the group consisting of a
glass fiber, a carbon fiber, or any combination(s) thereof.
[0096] The fabric may comprise fibers arranged in a uniaxial
orientation, a biaxial orientation, or any combination(s)
thereof.
[0097] The radiation may be selected from the group consisting of
microwaves, ultraviolet rays, an electron beam, x-rays, gamma-rays,
or any combination(s) thereof.
[0098] The radiation may comprise or consist essentially of an
electron beam.
[0099] The electron beam may possess an energy ranging from 0.15
MeV to 0.3 MeV.
[0100] Automated tape placement with "in-situ" layer-by-layer
curing may be used for applying the composite laminate.
[0101] The automated tape placement method can be modified to
overcome a technical challenge involved in a field installation of
a composite repair system.
[0102] A step of curing by applying radiation can be followed by a
step of thermal postcuring.
[0103] The step of thermal postcuring can be performed at a lower
temperature than, for a shorter duration than, or both at a lower
temperature and for a shorter duration than, would be needed to
achieve a similar extent of cure via thermal curing.
[0104] The fluid system component may comprise pipework, a
pipeline, a transmission pipeline, a distribution pipeline, a
gathering line, an oil riser, a gas riser, process piping, a girth
weld on a pipeline, a tank, a vessel, a girth weld on a vessel, an
elbow, a tee, a flange, a high-pressure injection line, or any
combination(s) thereof.
[0105] The material of construction used in the fluid system
component may comprise carbon steel, low and high alloy-steel,
stainless steel, aluminum, titanium, polyethylene, poly(vinyl
chloride) (PVC), acrylonitrile-butadiene-styrene (ABS) copolymers,
fiber-reinforced polymers, concrete, or any combination(s)
thereof.
[0106] Strengthening may comprise a repair, a structural
reinforcement, or any combination(s) thereof.
[0107] The location of repair may be in deep water, in shallow
water, coastal, or above ground.
[0108] In some embodiments, the temperature of the location that
the method is implemented and/or the curing takes place does not
exceed approximately 10.degree. C. (50.degree. F.).
[0109] In some embodiments, the temperature of the location that
the method is implemented and/or the curing takes place exceeds
10.degree. C. (50.degree. F.).
[0110] In some embodiments, automated or semi-automated means are
used for implementing the method. In some embodiments, personnel
deployed to the location are used for implementing the method. In
some embodiments, automated or semi-automated means are used in
conjunction with deployed personnel for implementing the method
[0111] A remotely operated vehicle (ROV) can be used for
transporting equipment and supplies to the location, for installing
the composite laminate, for the radiation-induced curing of the
composite laminate, or any combination(s) thereof.
[0112] In some embodiments, the maximum use temperature of the
composite repair system is at least 20.degree. C. (68.degree.
F.).
[0113] In some embodiments, the maximum use temperature of the
composite repair system is at least 40.degree. C. (104.degree.
F.).
[0114] In some embodiments, the maximum use temperature of the
composite repair system is at least 60.degree. C. (140.degree.
F.).
[0115] In some embodiments, the maximum use temperature of the
composite repair system is at least 80.degree. C. (176.degree.
F.).
[0116] In some embodiments, the maximum use temperature is attained
while the composite repair system is submerged in water.
[0117] The composite repair system can be qualified formally for
commercial use in high risk applications by being shown to meet the
criteria stipulated in the version of American Society of
Mechanical Engineers (ASME), Repair of Pressure Equipment and
Piping, Part 4 (Non-Metallic and Bonded Repairs), Article 4.1,
"Non-Metallic Composite Repair Systems: High Risk Applications"
that is in effect as of the date of completion of the development
of the composite repair system.
[0118] The composite repair system can be qualified formally for
commercial use by being shown to meet the criteria stipulated in
the version of an American Society of Mechanical Engineers (ASME)
qualification standards document for repairs using composite
laminates as patches, under preparation as of the date of this
filing, that is in effect as of the date of completion of the
development of the composite repair system.
[0119] While exemplary embodiments and applications of the present
disclosure have been illustrated and described, it is to be
understood that the invention is not limited to the precise
construction and compositions disclosed herein and that various
modifications, changes, and variations can be apparent from the
foregoing descriptions without departing from the spirit and scope
of the invention as defined by the appended claims.
* * * * *