Patent Description:
Suitable pressure vessel shell materials include metals, such as steel; or composites, which may be formed of laminated layers of wound fiberglass filaments or other synthetic filaments bonded together by a thermo-setting or thermoplastic resin. A liner or bladder is often disposed within a pressure vessel shell to seal the vessel, thereby serving as a fluid permeation barrier.

Generally, pressure vessels have limited lifetimes, and it is desirable to remove a pressure vessel from service before it fails. Both cyclic fatigue and static fatigue (stress rupture) contribute to the fatigue load, and thus the failure, of pressure vessels. The calendar life of a pressure vessel, or the number of fatigue cycles over a specific pressure range (for example, from near empty to full), is commonly used to determine when to remove a vessel from service. However, in some applications, the pressure ranges and number of cycles applied to the pressure vessel are inconsistent and/or unknown. In addition, the interaction between cyclic fatigue life and static fatigue life is not fully understood. The effects of cycling combine in unknown ways with the effects of the duration the pressure vessel spends at full pressure.

Mathematical projections of vessel lifetime are commonly used to evaluate the fatigue life of a pressure vessel. This requires that the number of cycles be counted or estimated, then sorted by mean stress levels and stress range. These cycles are combined into an equivalent number of full-range cycles to estimate the remaining vessel life. It must then be determined how to combine this information with static fatigue. Uncertainties are inherent in the calculation and estimation of cycles, in combining cycle effects, and in assessing the projected total and remaining life of the pressure vessel.

Another way to assess the estimated useful life remaining in a pressure vessel is to use sensors to gather information on the pressure vessel's physical characteristics. Suitable sensors include Modal Acoustic Emission (MAE) sensors, for example. Such ultrasonic sensors are available from Digital Wave Corporation of Centennial, Colorado. Ultrasonic wave propagation can be evaluated in bulk and "thin-walled" solid materials to assess the structural integrity of the materials. Due to the variation in stiffness as a function of propagation angle (i.e., material anisotropy), which is commonly observed in composite materials, significant effects in wave propagation characteristics are observed. Thus, such material anisotropy must be accounted for in the wave form analysis. Laminates further complicate this analysis because of the multiple material interfaces that should be considered. Analysis of such wave forms can lead to information regarding fiber fracture, matrix cracking, and interfacial delamination, for example.

<CIT> discloses a scanner head for ultrasonic testing of structures includes a carriage with rollers supporting the carriage for movement over a surface being tested in a selected direction. A transverse frame is supported by the carriage and extends in a second direction crossing the one direction. A transducer is supported by the frame for movement along the frame to preset operative offset positions. For pipes or boiler tubes, the frame is in the form of an arc bar having a T-slot in which a holder for the transducer rides. With the carriage moving axially of the tube or pipe along a reference line, the arc bar keeps the transducer perpendicular to the surface regardless of the offset position. The rollers drive a distance increment signal generator to pulse the transducer and drive the ultrasonic transceiver and display circuitry.

<CIT> discloses a self propelled device which travels along a reformer tube or other tube to detect variations in the tube diameter that may indicate impending failure of the tube. A two piece frame opens and closes about a hinge axis to allow application of the device to a tube and removal from the tube. When closed, wheels on the frame are held against the tube by a spring latch which allows the wheels to move in and out radially when diameter changes are encountered. One set of wheels is driven by an electric motor to propel the device along the tube. The diameter changes are sensed and measured by a linear variable differential transformer which monitors the gap between the ends of the frame sections. A chart recorder records the tube diameter measured at different positions along the tube length.

The present application provides a method of gathering information on a vessel arrangement as set out in claim <NUM> and the claims dependent thereon.

To assist the reader's understanding of the method, this disclosure describes a sensor mounting assembly configured for use with a vessel arrangement including at least first, second, third and fourth vessels. The sensor mounting assembly includes first and second elongated frame members, first and second rollers, and first and second sensors. The first roller is attached to the first elongated frame member and is configured to contact and roll upon a first surface of one of the first, second, third and fourth vessels. The first sensor is attached to the first elongated frame member and is configured to contact the surface of the first vessel upon actuation in a first direction. The second elongated frame member is connected to the first elongated frame member. The second roller is attached to the second elongated frame member and is configured to contact and roll upon a second surface of one of the first, second, third and fourth vessels. The second sensor is attached to the second elongated frame member and is configured to contact the surface of the second vessel upon actuation in a second direction that is substantially orthogonal to the first direction.

To further assist, this disclosure describes another embodiment of a sensor mounting assembly configured for use with a vessel arrangement including at least first, second, third and fourth vessels. The vessel arrangement is disposed in a container in a two-by-two stacked configuration having a central space. The sensor mounting assembly includes a top rail assembly, an upper interior rail assembly, a lower interior rail assembly, and a bottom rail assembly. The top rail assembly is attached to the container proximate a top of the container and is configured to position a first sensor proximate the first vessel. The upper interior rail assembly is positioned in the central space and is configured to position a second sensor proximate the first vessel and a third sensor proximate the second vessel. The lower interior rail assembly is positioned in the central space and is configured to position a fourth sensor proximate the third vessel and a fifth sensor proximate the fourth vessel. The bottom rail assembly is attached to the container proximate a bottom of the container and is configured to position a sixth sensor proximate the fourth vessel.

Additionally, to provide further assistance, this disclosure describes a method of mounting first, second, third, fourth, fifth, and sixths sensors for use with a vessel arrangement including at least first, second, third and fourth vessels, the vessel arrangement disposed in a container in a two-by-two stacked configuration having a central space. The method includes attaching a top rail assembly to the container proximate a top of the container to position a first sensor proximate the first vessel; inserting an upper interior rail assembly into the central space to position a second sensor proximate the first vessel and a third sensor proximate the second vessel; inserting a lower interior rail assembly into the central space to position a fourth sensor proximate the third vessel and a fifth sensor proximate the fourth vessel; and attaching a bottom rail assembly to the container proximate a bottom of the container to position a sixth sensor proximate the fourth vessel.

This summary is provided to introduce concepts in simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the disclosed or claimed subject matter and is not intended to describe each disclosed embodiment or every implementation of the disclosed or claimed subject matter. Specifically, features disclosed herein with respect to one embodiment may be equally applicable to another. Further, this summary is not intended to be used as an aid in determining the scope of the claimed subject matter. Many other novel advantages, features, and relationships will become apparent as this description proceeds. The figures and the description that follow more particularly exemplify illustrative embodiments.

The disclosed subject matter will be further explained with reference to the attached figures, wherein like structure or system elements are referred to by like reference numerals throughout the several views. It is contemplated that all descriptions are applicable to like and analogous structures throughout the several embodiments.

While the above-identified figures set forth one or more embodiments of the disclosed subject matter, other embodiments are also contemplated, as noted in the disclosure. In all cases, this disclosure presents the disclosed subject matter by way of representation and not limitation.

The figures may not be drawn to scale. In particular, some features may be enlarged relative to other features for clarity. Moreover, where terms such as above, below, over, under, top, bottom, side, end, right, left, vertical, horizontal, etc., are used, it is to be understood that they are used only for ease of understanding the description. It is contemplated that structures may be oriented otherwise.

As a result of the principal stress state and anisotropic construction of Type III and Type IV cylindrical composite pressure vessels (also called pressure cylinders), several unique wave propagation characteristics are observed by MAE sensors. These principal stress states are caused, for example, by the metallic load sharing liner on the interior of Type III cylinders and the inherently asymmetric laminate construction of Type IV composite pressure cylinders. From a laminated plate theory perspective, the non-symmetric laminate results in non-zero components of the coupling stiffness matrix (Bij); from a wave propagation perspective, such a result indicates that unlike isotropic plates, pure extensional and flexure mode deformation will not be observed.

A key component to optimizing the sensor spacing for the MAE testing of composite pressure cylinders and ensuring full coverage of the cylinder is understanding the attenuation behavior of the composite laminate as a function of the propagation angle and the frequency at which the wave propagates. From experimental measurements and considerations of the principal stress state of the vessel, for an equivalent frequency, waves are attenuated more severely at angles approaching the axial direction of the vessel. Conversely, waves are attenuated less severely in the hoop direction, a fact that can be exploited when determining sensor spacing and placement schemes of composite pressure cylinders.

To minimize the number of sensor locations necessary to fully cover a vessel, increases in signal sensitivity and SNR (signal-to-noise ratio) can be realized through a Phased Array Modal Acoustic Emission (PA-MAE™) approach over traditional single-element MAE measurements. The increase in system sensitivity and SNR provided with PA-MAE™ are utilized in determining sensor spacing in highly attenuative wave propagation measurements, as is common in composite pressure cylinders. Furthermore, it has been shown that accurate source location from a multiple element array is possible.

In light of the above discussion, sensor array placement that is adequately dense in the axial direction <NUM>, but which simultaneously takes advantage of the less attenuative nature of wave propagation in the hoop direction, is utilized to minimize the number of sensor placement locations, while fully covering the pressure vessel.

Sensor arrays have been used to assess the structural integrity of pressure vessels in laboratory settings. In the current state of the art, the pressure vessel is removed from its field application and shipped to a laboratory for testing. Thus, pressure vessels are typically not tested when they are deployed in arrangements in use. This disclosure is directed to a sensor mounting system that allows for the testing of pressure vessels in the field, such as in an arrangement <NUM> of four pressure vessels <NUM> contained within a container <NUM>, as shown in <FIG>. The disclosed system allows for requalification testing of the pressure vessels <NUM> out in the field by allowing testing sensors to be manipulated in very compact spaces around the pressure vessels as they are arranged in an actual use, such as in a shipping container, for example.

In an exemplary embodiment, container <NUM> is a typical intermodal shipping container, such as one suitable for use with semi-trailer trucks, trains, cargo ships and barges. <FIG> shows the top portion of an arrangement <NUM>, the totality of which can be seen in <FIG>. In <FIG>, the roof of the container <NUM> has been removed to allow access to a top portion of arrangement <NUM> of the pressure vessels <NUM>.

As shown in <FIG> and <FIG>, different types of rail assemblies for holding the sensors are used in different areas of the container <NUM>. Rail assemblies <NUM>, <NUM>, <NUM> and <NUM> allow for insertion of the sensor arrays into the confined areas within the shipping container <NUM> and around the pressure vessels <NUM>. For example, top rail assembly <NUM> includes brackets <NUM> for resting upon a side wall <NUM> of a shipping container <NUM> in which the arrangement <NUM> of pressure vessels <NUM> is placed. Upper interior rail assembly <NUM> includes wheels thereon for rolling into the space <NUM> between the pressure vessels <NUM>, with the rollers or casters <NUM> rolling upon the upper wall surfaces of the two bottom pressure vessels <NUM>. Once rolled into the space <NUM>, the upper interior rail assembly <NUM> is raised into position against the upper two pressure vessels <NUM> by cable <NUM> and hook <NUM>, as shown in <FIG>. Thereafter, the lower interior rail assembly <NUM> can be similarly rolled into space <NUM>. Two bottom rail assemblies <NUM> are attached by pipe brackets <NUM> to pipes <NUM> at the lower corners of container <NUM>. Thereafter, sensor brackets <NUM> (having spacer bars <NUM> attached between adjacent sensor brackets <NUM>) are rolled onto frame member <NUM> of bottom rail assembly <NUM> via rollers <NUM>, as shown in <FIG>, <FIG>.

As shown in <FIG> and <FIG>, in an exemplary embodiment, cross bars <NUM> span across the top two pressure vessels <NUM> and include support rods <NUM>. In container <NUM>, a perforated pipe <NUM> may span a length (i.e., dimension along axial direction <NUM>) of the container <NUM> at the top and/or bottom of each of the side walls <NUM> of container <NUM>. In some cases, perforated pipes <NUM> contain fire protection elements. In an exemplary embodiment, top rail assemblies <NUM> of an exemplary sensor mounting system are positioned proximate top pipes <NUM>. A plurality of sensors <NUM> and associated data acquisition boxes <NUM> are arranged along a length (i.e., dimension along axial direction <NUM>) of each top rail assembly <NUM>. In an exemplary embodiment, each sensor <NUM> is a PA-MAE sensor that is configured to be placed in contact with the outer cylindrical surface of pressure vessel <NUM>. As shown in the illustrations, an array of the sensors <NUM> is positioned along the surfaces of pressure vessels <NUM> in predetermined locations to gather acoustic wave data relevant to each pressure vessel <NUM>.

<FIG> is a close-up view of a right-hand portion of <FIG>, showing a sensor <NUM> and its associated data acquisition box <NUM>. To position sensor <NUM> to obtain information on pressure vessel <NUM>, an actuation device <NUM> is actuated to move sensor <NUM> in direction <NUM>, so that the sensing surface of sensor <NUM> contacts the outer surface of pressure vessel <NUM> with an appropriate coupling force. In exemplary embodiments, suitable actuation devices <NUM> include, for example, pneumatic cylinders, electric motors, and magnetic actuators. In an exemplary embodiment, direction <NUM> is substantially orthogonal to a tangent of the outer surface of pressure vessel <NUM>. In an exemplary embodiment, top rail assembly <NUM> is supported on container <NUM> by brackets <NUM>.

In <FIG> and <FIG>, only the upper portion of an arrangement <NUM> of four pressure vessels <NUM> is visible. <FIG> show the entire arrangement <NUM> of four pressure vessels <NUM>, removed from container <NUM>. While the disclosed mounting system is described with reference to a set of four pressure vessels <NUM>, positioned in a two-by-two stacked arrangement, it is contemplated that the various components of the disclosed mounting system can be applied to other arrangements of pressure vessels including more or fewer pressure vessels, in different stacked configurations, and/or different vessel sizes. As shown in <FIG>, an exemplary sensor mounting system includes two top rail assemblies <NUM>, an upper interior rail assembly <NUM>, a lower interior rail assembly <NUM>, and two bottom rail assemblies <NUM>. Each of these rail assemblies <NUM>, <NUM>, <NUM> and <NUM> has a length that is suitable for the pressure vessels <NUM> to be tested, and also configured for the container <NUM> in which the pressure vessel arrangement <NUM> is positioned. While sensors <NUM>, data acquisition boxes <NUM>, actuation devices <NUM>, and their associated electrical, signal, and fluid supply lines are not shown in some drawings for ease of viewability, it is to be understood that they would be attached to the described sensor mounting system in actual use. In an exemplary embodiment, each of the rail assemblies <NUM>, <NUM>, <NUM>, <NUM> carries the same number of sensors <NUM> and their corresponding actuation devices <NUM>, evenly spaced along a length that is parallel to axial direction <NUM>. In <FIG>, for simplicity of illustration, not all of the devices <NUM>, <NUM> are shown on each of the rail assemblies <NUM>, <NUM>, <NUM> and <NUM>.

In the illustrated embodiments, each of the pressure vessels <NUM> has a row of sensors <NUM> (mounted on rail assemblies <NUM>, <NUM>, <NUM>, <NUM>) on diametrically opposed sides of the pressure vessel <NUM>. Thus, in the illustrated embodiment, the rows of sensors <NUM> are arranged around each pressure vessel <NUM> with a radial spacing of about <NUM> degrees. Such an arrangement <NUM> is particularly suitable for use with phased array MAE sensors. However, it is contemplated that additional rows of sensors <NUM> (and corresponding rail assemblies) could be added, such as would be suitable with other types of sensors, such as the more traditional single-element MAE sensors, or as vessel diameter, material attenuation behavior, and other factors warrant. For example, additional rail assemblies may be used to space rows of sensors around each pressure vessel <NUM> with a radial spacing of about <NUM> degrees. Moreover, where a pressure vessel is removed from a container, additional flexibility is afforded, and a radial spacing between three rows of sensors around a pressure vessel with a radial spacing of about <NUM> degrees is useful. It is contemplated that still other radial spacings are suitable, such as might be used with other types of sensors.

As shown in <FIG>, each of upper interior rail assembly <NUM> and lower interior rail assembly <NUM> includes two t-slot aluminum frame members <NUM> in an exemplary embodiment. Particularly suitable frame members <NUM> are commercially available from <NUM>/<NUM> Inc. of Columbia City, Indiana. In an exemplary embodiment, the two frame members <NUM> of each of upper interior rail assembly <NUM> and lower interior rail assembly <NUM> are held in a mutually orthogonal relationship by the affixation of each of frame members <NUM> to an angle plate <NUM>. Brackets <NUM> of each of interior rail assemblies <NUM>, <NUM> carries casters <NUM> thereon. As shown on lower interior rail assembly <NUM>, casters <NUM> are oriented to roll on the outer cylindrical surfaces of the lower pressure vessels <NUM>. Sensor mounting brackets <NUM> are positioned on interior rail assemblies <NUM>, <NUM> so that actuation devices <NUM> mounted thereon will move the attached sensors into position in contact with the outer cylindrical surfaces of the pressure vessels <NUM>.

Because the interior rail assemblies <NUM>, <NUM> each include two frame elements <NUM>, the frame elements of the interior rail assemblies <NUM>, <NUM> in some cases will be referred to with reference numerals 50a and 50b. However, it is to be understood that all references to frame member <NUM> will also apply to frame members 50a and 50b, unless otherwise indicated.

Upper interior rail assembly <NUM> has a plurality of casters <NUM> arranged similarly to those described with reference to lower interior rail assembly <NUM>. To position the interior rail assemblies <NUM>, <NUM> in the space <NUM> between the four pressure vessels <NUM>, in an exemplary method of positioning rail assemblies of an exemplary sensor mounting system, the upper interior rail assembly <NUM> is inserted into space <NUM> while the lower interior rail assembly <NUM> remains outside of arrangement <NUM>. Upper interior rail assembly <NUM> is inserted into space <NUM> proximate an end of the pressure vessels <NUM> by rolling the upper interior rail assembly <NUM> on casters <NUM> on the cylindrical surfaces of the two bottom pressure vessels <NUM>. Thus, the upper interior rail assembly <NUM> would occupy essentially the position shown as being occupied by the lower interior rail assembly <NUM> in <FIG>. After the upper interior rail assembly <NUM> is fully inserted into space <NUM>, the upper interior rail assembly <NUM> is raised into the position shown in <FIG> by a cable inserted through loops <NUM>, which are affixed to angle bracket <NUM> in an exemplary embodiment. As shown in <FIG>, an exemplary cable <NUM> is attached to support rod <NUM>, which in turn is attached to cross bar <NUM>. In an exemplary embodiment, an easily detachable connection between support rod <NUM> and cable <NUM> is provided by hook <NUM>. In the lifted position, another set of casters <NUM> is placed in contact with the cylindrical outer surfaces of the two upper pressure vessels <NUM>.

After the upper interior rail assembly <NUM> is lifted into the position shown in <FIG> and <FIG>, the lower interior rail assembly <NUM> can be rolled into position as shown, with casters <NUM> contacting the cylindrical surfaces of the bottom two pressure vessels <NUM>. As shown in <FIG>, front wall panel <NUM> of container <NUM> has an opening <NUM> provided therein to allow for the insertion of interior rail assemblies <NUM>, <NUM> into space <NUM> between the four pressure vessels <NUM> of arrangement <NUM>. To position sensor <NUM> to obtain information on pressure vessel <NUM>, an actuation device <NUM> is actuated to move sensor <NUM> in direction <NUM>, so that the sensing surface of sensor <NUM> contacts the outer surface of pressure vessel <NUM> with an appropriate coupling force. In exemplary embodiments, suitable actuation devices <NUM> include, for example, pneumatic cylinders, electric motors, and magnetic actuators. In an exemplary embodiment, direction <NUM> is substantially orthogonal to a tangent of the outer surface of pressure vessel <NUM>. While not illustrated, it is to be understood that a plurality of electrical power, signal communication, and pneumatic air lines are connected to the sensors <NUM>, actuators <NUM> and associated data acquisition boxes <NUM> mounted on the rail assemblies <NUM>, <NUM>, <NUM>, <NUM>.

<FIG> is a perspective view of an exemplary embodiment of top rail assembly <NUM>. <FIG> is an enlarged view of the portion of <FIG> that is encircled and labeled "A. " <FIG> is an enlarged view of the portion of <FIG> that is encircled and labeled "B. " In <FIG>, some of the sensor brackets <NUM>, container brackets <NUM>, and data acquisition box brackets <NUM> shown attached to frame member <NUM>. Additionally, one each of container bracket <NUM>, sensor bracket <NUM> and data acquisition box bracket <NUM> are shown detached from frame member <NUM>. A length of frame member <NUM> (along axial direction <NUM>) can be selected to suit a particular pressure vessel <NUM> to be assessed. Moreover, the number of sensor brackets <NUM> and data acquisition box brackets <NUM> (and a corresponding number of sensors <NUM> and data acquisition boxes <NUM>) can be selected according to the length and diameter of the pressure vessel <NUM>, along with other considerations such as the pressure vessel material composition and the type of sensor <NUM> to be mounted. Each of the plurality of sensor mounts <NUM> is preferably evenly spaced along a length of frame member <NUM> (i.e., at equal intervals) in an exemplary embodiment. Such positioning along the length of frame member <NUM> can be adjusted in some embodiments by sliding and/or rolling the bracket <NUM>, <NUM> or <NUM> along longitudinal slots <NUM> of frame member <NUM>. Moreover, the brackets <NUM>, <NUM>, <NUM> can be attached to frame member <NUM> using fasteners such as plates, washers, screws, and bolts, for example.

<FIG> shows a reverse side of the top rail assembly <NUM> of <FIG>. <FIG> is an enlarged view of the portion of <FIG> that is encircled and labeled "D. " As shown in <FIG>, and <FIG>, in an exemplary embodiment, sensor bracket <NUM> includes arms <NUM> on opposed sides of plates <NUM>. Each arm <NUM> includes at least one hole <NUM> configured for the passage of fastener <NUM>, which secures sensor <NUM> between arms <NUM> of sensor bracket <NUM>. As shown in <FIG>, fasteners <NUM> pass through two of holes <NUM> in plates <NUM> and connect to corresponding fasteners <NUM> positioned within slot <NUM> of frame member <NUM>. An actuation device <NUM> is held in actuator containment space <NUM> and is configured to push upon surface <NUM> of sensor <NUM> in direction <NUM>. This action moves suitable sensor components into contact with the surface of pressure vessel <NUM>.

As shown in <FIG>, in an exemplary embodiment, container bracket <NUM> includes a first portion <NUM> attached to frame member <NUM> with fastener <NUM>, washer <NUM>, and plate <NUM>. Container bracket <NUM> also includes a second portion <NUM> attached to the first portion <NUM> by fastener <NUM>, to thereby clamp sill <NUM> of side wall <NUM> (labeled in <FIG>, <FIG> and <FIG>) of container <NUM> between the first and second portions <NUM>, <NUM> of container bracket <NUM>.

As shown in <FIG>, in an exemplary embodiment, data acquisition box bracket <NUM> includes plate <NUM> having holes <NUM> for the passage of fasteners <NUM>, which attach to data acquisition box <NUM>. Further, plate <NUM> has holes <NUM> for the passage of fasteners <NUM>, which connect to corresponding fasteners <NUM> positioned within slot <NUM> of frame member <NUM> (as discussed above with reference to <FIG>, for example).

<FIG> show perspective and exploded perspective views of exemplary embodiments of sensor bracket <NUM>. An exemplary sensor bracket <NUM> includes a centrally located actuator containment space <NUM>, configured to hold actuation device <NUM>. Plates <NUM> includes holes <NUM> configured to accept fasteners for attachment to frame member <NUM>, as discussed above with reference to <FIG>. Additionally, referring to <FIG>, holes <NUM> may be used to accept fasteners (not shown) for attachment of plate <NUM>, which is in turn attached to rollers <NUM>.

<FIG> is a perspective view of an exemplary embodiment of upper interior rail assembly <NUM>. On the left side of <FIG>, in encircled portion "A," some of the components such as caster bracket <NUM> and its associated caster <NUM>, sensor bracket <NUM>, data acquisition box bracket <NUM> and its associated data acquisition box <NUM> are shown as detached from frame members <NUM>. However, these elements are illustrated as being attached to frame members <NUM> in the un-encircled portion of <FIG>. In <FIG>, the sensor brackets <NUM> and data acquisition box brackets <NUM> on only one of the frame elements 50b are clearly visible. However, it is to be understood that a similar arrangement of sensor brackets <NUM> and data acquisition box brackets <NUM> is also provided on the other frame element 50a. <FIG> also shows fluid manifold <NUM>, to which fluid lines are attached for actuation of actuation devices <NUM> held in actuator containment space <NUM> of sensor bracket <NUM>.

<FIG> is a perspective view illustrating some components of an exemplary lower interior rail assembly <NUM>. Because the sensor brackets <NUM> are mounted on two frame members 50a and 50b, in some cases, the sensor brackets will be referred to with reference numerals 58a and 58b. However, it is to be understood that all references to sensor bracket <NUM> will also apply to sensor brackets 58a and 58b, unless otherwise indicated. Sensor brackets 58a are shown as attached to frame element 50a. Sensor brackets 58b are shown as removed from frame element 50b. In an exemplary embodiment, data acquisition box brackets <NUM> are attached to frame element <NUM> between adjacent sensor brackets <NUM>.

<FIG> is a perspective view of an exemplary embodiment of bottom rail assembly <NUM>, which includes pipe brackets <NUM> attached to frame element <NUM> proximate ends of the frame element <NUM>. In an exemplary embodiment, sensor brackets <NUM> are attached to frame element <NUM> by rollers <NUM>, shown in <FIG>. In an exemplary embodiment, each roller <NUM> is configured with a flange <NUM> that rolls along groove <NUM> of frame element <NUM>. In an exemplary embodiment, spacer bars <NUM> are positioned on frame element <NUM> between adjacent sensor brackets <NUM> to facilitate accurate and consistent spacing intervals between adjacent sensor brackets <NUM> (and therefore consistent spacing between sensors <NUM> in the mounted sensor arrays).

<FIG> is a perspective partial end view of bottom rail assembly <NUM> secured to pipe <NUM> of container <NUM>. Often, a container <NUM> will include four pipes <NUM>, the upper pipes <NUM> being visible in <FIG>, and the lower pipes <NUM> being visible in <FIG>. In an exemplary embodiment, pipe bracket <NUM> includes a first portion <NUM> attached to frame member <NUM> with fastener <NUM> and a second portion <NUM> attached to the first portion <NUM> by fasteners <NUM>, to thereby clamp pipe <NUM> between the first and second portions <NUM>, <NUM> of pipe bracket <NUM>. <FIG> further shows a two part clamp <NUM>, fastened together by fastener <NUM>, which is used to secure pipe <NUM> to an interior of side wall <NUM> of container <NUM>.

Referring to <FIG>, <FIG> and <FIG>, for installation of bottom rail assembly <NUM> in container <NUM>, in an exemplary embodiment, only small access openings <NUM> in an end wall panel <NUM> proximate the lower corners of container <NUM> are required for insertion of frame element <NUM> having first portion <NUM> of pipe bracket <NUM> fixed thereto. Frame element <NUM> of bottom rail assembly <NUM> is secured inside container <NUM> by clamping second portion <NUM> and first portion <NUM> of pipe bracket <NUM> together around pipe <NUM>.

Thereafter, the plurality of sensor brackets <NUM>, spaced apart from each other by intervening spacer bars <NUM>, are attached to frame element <NUM> by moving rollers <NUM> from one end of frame element <NUM> toward the other end of frame element <NUM>. To position sensor <NUM> to obtain information on pressure vessel <NUM>, an actuation device <NUM> is actuated to move sensor <NUM> in direction <NUM>, so that the sensing surface of sensor <NUM> contacts the outer surface of pressure vessel <NUM> with an appropriate coupling force. In exemplary embodiments, suitable actuation devices <NUM> include, for example, pneumatic cylinders, electric motors, and magnetic actuators. In an exemplary embodiment, direction <NUM> is substantially orthogonal to a tangent of the outer surface of pressure vessel <NUM>.

After gathering and processing information from sensors <NUM> and data acquisition boxes <NUM>, actuation devices <NUM> may be activated to retract sensors <NUM> away from the respective surfaces of pressure vessel <NUM> so that rail assemblies <NUM>, <NUM>, <NUM>, <NUM> can be removed from container <NUM> in a reverse method of their installation. The rail assemblies <NUM>, <NUM>, <NUM>, <NUM> can then be deployed on a different pressure vessel arrangement <NUM> for assessment of the structural integrity and estimated useful remaining life of a different set of pressure vessels <NUM>.

For example, for removal of bottom rail assembly <NUM>, in an exemplary embodiment, the connected line of multiple sensor brackets <NUM> and attached intervening spacer bars <NUM> can be pulled off one end of frame <NUM>. Then, two portions <NUM>, <NUM> of pipe bracket <NUM> can be disconnected, allowing frame <NUM> to be pulled out opening <NUM> in end wall <NUM> of container <NUM>.

Lower interior rail assembly <NUM> can be rolled via casters <NUM> on the two bottom pressure vessels <NUM>, out of opening <NUM> of end wall <NUM> of container <NUM>, to thereby remove lower interior rail assembly <NUM> from space <NUM> between the pressure vessels <NUM>. For removal of upper interior rail assembly <NUM>, cable <NUM> is detached from hook <NUM> and upper interior rail assembly <NUM> is lowered so that casters <NUM> contact the two bottom pressure vessels <NUM>. Upper interior rail assembly <NUM> can be rolled via casters <NUM> on the two bottom pressure vessels <NUM>, out of opening <NUM> of end wall <NUM> of container <NUM>, to thereby remove upper interior rail assembly <NUM> from space <NUM> between the pressure vessels <NUM>.

For removal of upper rail assembly <NUM> from container <NUM>, two portions <NUM>, <NUM> of container bracket <NUM> can be disconnected, allowing their removal from sill <NUM> of side wall <NUM> of container <NUM>. Frame <NUM> can be lifted out of container <NUM> so that a roof of container <NUM> can be replaced.

Claim 1:
A method of gathering information on a vessel arrangement (<NUM>) having a central space (<NUM>) between first, second, third and fourth vessels (<NUM>), the method comprising:
inserting an interior sensor mounting assembly (<NUM>, <NUM>) into the central space (<NUM>);
positioning a first sensor (<NUM>) of the interior sensor mounting assembly (<NUM>, <NUM>) proximate the first vessel (<NUM>);
positioning a second sensor (<NUM>) of the interior sensor mounting assembly (<NUM>, <NUM>) proximate the second vessel (<NUM>);
moving the first sensor (<NUM>) in a first direction (<NUM>) into contact with the first vessel (<NUM>); and
moving the second sensor (<NUM>) in a second direction (<NUM>) into contact with the second vessel (<NUM>).