Patent Description:
A statement given by the World Shipping Council<NUM> indicates that, during a survey period between <NUM> and <NUM>, there were <NUM> containers lost at sea each year, excluding catastrophic loss. These losses happened despite routine checking of tension by the crews during the journies, and are most oftem are attributed to improper tensioning of lashing gear. Even in the cases where other causal factors are identified, the final component impacted before failure is the lashing gear. <FIG> shows a container vessel that has experienced container movement (and likely losses) as a result of improperly-tensioned lashing gear.

It is difficult to monitor container lashing tightness when the vessel is sailing. Containers can get loose for several reasons, including routine flexing of ship structure, bad weather, poor workmanship in loading and securing containers on borard. Normally, a container ship has several thousand containers stacked on top of each other multi-row configuration. This configuration makes container monitoring difficult. At present, the only effective way to monitor containers is by manually checking them at certain intervals during the sailing voyage period.

Manual systems for monitoring and maintaining lashing gear tension suffer several disadvantages. As the size of container ships increase over time, manual checking of tension during voyage becomes more costly, and is often not comprehensive and ineffective due to resource limitations. With increase in size of ships, it is not possible to visit each lashing rod with sufficient frequency to check its tightness. Even on a sampled basis, one estimate for example suggests manual checking require <NUM>-<NUM> hours time by two crew per day. Manual checking is also dangerous, with associated risks of crew falling overboard. One insurer estimates historical losses per lost container at between $<NUM>,<NUM> to $<NUM> million. Container losses may also generate an environmental impact with attendant costs (for example, from lost containers that are washed ashore).

Indirect methods of monitoring container security such as measuring the hull deformation and container deformation have been proposed in past. They do not directly measure the lashing rod tightness, and hence do not address the problem effectively.

It would be beneficial to develop a more effective and efficient system and method for monitoring and maintaining lashing gear tension. Further background art can be found in the following documents:
<CIT> discloses a method for monitoring the rigging of a sailing vessel. The method comprises a step for measuring elongation, wherein the elongation of at least part of a stay is measured. The invention furthermore relates to a stay provided with elongation-measuring means, such as an optical fibre for example, to a measuring device comprising elongation-measuring means which can be fastened to a stay, as well as to the use of the data which is obtained by the method for monitoring the rigging of a sailing vessel. <CIT> discloses an automatic tension sensing and control system for cargo restraints comprises a load binder, a tension sensor, an actuator coupled to the load binder, and a control module. The control module receives signals from the sensor and can command the actuator to tighten or slacken the load binder. The system can also include an annunciator and an information storage and retrieval system. <CIT> discloses a method and apparatus for monitoring and measuring the load in a sailboat's rigging components. A rigging component such as a turnbuckle is modified to incorporate a sensing element, such as a strain gage. Strain gages are bonded and wired into a measuring circuit. The strain gage measures the strain under a load and generates an electrical signal that is directly proportional to the tension load. The load is then monitored and/or displayed using standard data acquisition equipment. The strain gage also identifies loose rigging such as may happen with shrouds which are subject to sudden high loading with movement of the boat and allows the operator to tighten that shroud or other piece of rigging. <CIT> discloses a strain transducer strand that is provided comprising an elongatable central core around which are helically wound one or more plastic tubes each of which contains an optical fibre. Each tube is overfilled with the optical fibre, such that the fibre is longer than the tube. As the transducer strand experiences strain, the core, plastic tubes, and optical fibres elongate, with the helical winding acting as gearing to produce a reduced elongation in the fibres proportional to the elongation of the transducer strand. The degree of elongation may be detected by monitoring the optical properties of light transmitted along the fibres. The transducer strand is particulary intended for incorporation into elongate load bearing members, such as ropes. The book by <NPL> discloses further background art.

By way of example, aspects of the present disclosure are directed to disclose a novel system and method for remotely monitoring the lashing gear strain for containers being carried onboard ships ("SMARTLashing") using fiber optic sensors and other associated hardware and software systems.

The dependent claims are directed to optional features and preferred embodiments. When a change in the value of stress or strain is indicative of loosened or overtightened restraint members, a mitigation event is triggered. The stress or strain analysis distinguishes intermittent changes indicating a vehicle movement from sustained, gradual changes indicating a restraint member that has either been loosened or overtightened.

For a typical container ship carrying <NUM> or more containers, in comparison to prior art methods requiring manual monitoring of container restraints, it is estimated that the system and method disclosed herein can reduce crew effort by <NUM>-<NUM> hrs. by <NUM> crew per day, prevent crew from falling overboard (<FIG>), and significantly reduce cost of associated insurance claims for injury and loss, which are estimated between $<NUM> - $<NUM> million per container loss. In addition, the impact on environment stemming from containers washed ashore can be substantially reduced.

This SUMMARY is provided to briefly identify some aspects of the present disclosure that are further described below in the DESCRIPTION. This SUMMARY is not intended to identify key or essential features of the present disclosure nor is it intended to limit the scope of any claims.

A more complete understanding of the present disclosure may be realized by reference to the accompanying drawing in which:.

The following merely illustrates the principles of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its scope as defined by the appended claims.

Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.

Unless otherwise explicitly specified herein, the drawings are not drawn to scale.

Aspects of the present disclosure are directed to an inventive system and method for monitoring and maintaining lashing gear tension of a container vessel. Elements of the inventive system include lashing rods, optical strain sensors ("fiber Bragg grating" or "FBG" sensors), an interrogator unit for polling the optical strain sensors to obtain strain data, optical fiber cables for optical communications between the interrogator unit and strain sensors, and a general-purpose computer and monitor for operating the system.

Some other non-optical strain monitoring solutions require extensive power cable networks on board ship, and are difficult to implement. Also, the environment on deck is often harsh, and components are required to be environmentally robust and explosion-proof. This makes many other possible strain monitoring solutions impractical to implement on board merchant vessels.

<FIG> illustrate container lashing arrangements in accordance with aspects of the present disclosure. As shown for example in <FIG>, containers <NUM> are arranged in column stacks <NUM> in which vertically adjacent ones of the containers <NUM> are fixedly fastened to one another. Column stacks <NUM> are subjected to a variety of forces (for example, resulting from wind and motion of the vessel <NUM> asea that can be characterized as one or more of pitch motion, heave motion and roll motion) which further require that the column stacks <NUM> be secured to the deck <NUM> of the vessel <NUM>. This is typically accomplished by mechanically fastening one or more containers in the column stack to the deck <NUM> by means of lashing rods <NUM> that are preferably fastened at one end to a receptacle affixed to a container <NUM> and at the other end to a lashing bridge <NUM> that is integral with and/or afficxed to the deck <NUM> (see, e.g., <FIG>). With reference to <FIG>, lashing rods <NUM> may preferably include a turnbuckle <NUM> with a threaded rod connected to a shackle <NUM> on one end, and a rod extending from the other end that terminates in a second shackle <NUM>. The turnbuckle <NUM> provides a mechanism for loosening or tightening the lashing rods <NUM> in order to properly secure the associated containers <NUM> to the deck <NUM>. In accordance with aspects of the present disclosure, and as depicted in <FIG>, suitable lashing gear may included a model ST-<NUM> knob/jaw turnbuckle and LB-<NUM> lashing bar, both available from International Lashing Systems NV of Antwerp, Belgium.

Lashing rods <NUM> are preferably applied in a selective manner to a limited number of containers <NUM> to secure the containers <NUM> to the deck <NUM>. <FIG> illustrate two nonlimiting examples of such selective applications. In <FIG>, two crossing lashing rods <NUM> are attached to opposing lashing bridges <NUM> in proximity to a lower containers <NUM>. The turnbuckles <NUM> are each coupled to a twin rod and shackle arrangement that is respectively coupled to one receptacle that is integral with an upper corner of the lower container <NUM> and to another shackle arrangement that is coupled to a second receptacle that is integral with a lower corner of a vertically adjacent container <NUM> (see, eg. An equalizing device (for example, toggle plate 21a) is preferably positioned between the turnbuckles <NUM> and twin rod and shackle arrangement to equalize the forces applied by each lashing rod <NUM> to the corners of the two containers. In the example of <FIG>, a pair lashing rods <NUM> are attached to each of the opposing lashing bridges <NUM>, with one of the lashing rod pair being coupled to a receptacle that is integral with an upper corner of the lower container <NUM> and the other one of the lashing rod pair being coupled to a another receptacle that is integral with an upper corner of a vertically adjacent container <NUM>.

<FIG> illustrate a lashing rod monitoring scheme in accordance with aspects of the present invention. A typical container vessel <NUM> may carry several thousand containers. A suitable monitoring scheme should ideally be capable of ensuring that lashing tightness of all containers is comprehensively covered without having the need to fit all lashing rods with sensors. For this purpose, the inventors determined by experimentation and by studying causal factors for container lashing becoming loose or tight that sensors could be applied to lashing rods associated with just two rings of the most vulnerable container stacks. As illustrated for example in <FIG>, these rings include containers <NUM> occupying one or two tiers <NUM> of the outermost stack rows 14a on the deck <NUM> of the container vessel <NUM>, and at least one tier of the outermost stack rows 15b having a highest stack weight. Other containers deemed to be especially vulnerable may optionally be added for monitroring as well.

The inventors further determined that the number of sensors <NUM> used in each ring cant be selectively reduced without significantly impacting the ability of the system to detect tensioning anomalies for the lashing rods <NUM>. Specifically, for example, as illustrated by <FIG>, sensors <NUM> can alternatively be omitted on each of port and starboard sides from adjacent bays <NUM>, such that each bay <NUM> has sensors <NUM> positioned on only one of the sides (port or starboard) of the bay. As another example illustrated by <FIG>, the sumber of sensors on port and starboard sides in each bay can be reduced (for example, eliminating sensors on either the for or aft lashing rods <NUM> on each side).

<FIG> and <FIG>, in accordance with aspects of the present disclosure, illustrates sensor configurations as applied to the lashing rods <NUM>. As depicted, strain gauges are applied along a longitidinal axis of the lashing rods <NUM>. The sensors <NUM>, <NUM> depicted in <FIG> and <FIG> are optical strain gauges (a suitable gauge for this purpose is the OS3100 optical strain gauge available from Micron Optics, Inc. of Atlanta, Georgia). The OS3100 optical strain gauge incorporates a fiber Bragg grating (FBG) configured as a fiber Fabry-Perot interferometer. <FIG> illustrates a first configuration not forming part of the present invention, in which a long strain-sensing gauge <NUM> is affixed to the turnbuckle <NUM> of the lashing rod <NUM>. <FIG> and <FIG> illustrate a second configuration in accordance with the present invention, in which a short strain-sensing gauge is affixed to the shackle <NUM> of the lashing rod <NUM>. Strain is measured by sending a laser beam through the FBG sensor fitted on the lashing gear, and measuring the change in wavelength. For ease of identification, ach sensor is assigned a unique wavelength. This approach minimizes the amout of required cabling, and supports a modular, scalable infrastructure which is practical and easy to implement.

Long strain gauge sensors <NUM> are fitted along the length of the turnbuckle <NUM> of the lashing gear <NUM>. These gauges are fitted across the entire length of the turnbuckle <NUM> in longitudinal direction. The inventors determined however that this configuration is difficult to maintain since the turnbuckle needs to be rotated. Short strain gauge sensors <NUM> on the other hand are fitted on the lower shackle, after machining the surface. The inventors found that, while measurements are magnified for the long strain gauge sensors <NUM> as compared to the short strain gauge sensors <NUM>, deviations were accurately captured in both cases. <FIG> illustrate outputs for the long strain gauge sensors <NUM> and the short strain gauge sensors <NUM>, respectively. As a result, the implementation uses the short strain gauge sensors <NUM>.

Since the FBG sensors are very sensitive to variation in temperature, an additional sensor is used in each case for measuring temperature. Compensation for temperature is made to accurately measure strain due to movement of ship and other factors. <FIG> illustrate the measurement process. In <FIG>, a measure of change in wavelength over time is obtained by the strain gauge. <FIG> illustrates the output of the isolates sensor, which indicates a change in wavelength over time due only to temperature effects. In order to produce the output of <FIG>, a second FBG sensor may be provided in proximity to the strain gauge but isolated from exposure to forces inducing strain. Alternatively, as optical fiber rates of expansion and contraction due to temperature are readily known, the change in wavelength due to temperature can simply be calculated to represent the output of <FIG>. As illustrated in <FIG>, a difference between the wavelength values illustrated in <FIG> can then be calculated to determine temperature-compensated strain levels.

In accordance with aspects of the present disclosure, <FIG> and <FIG> illustrate an overall architecture for the container lashing gear monitoring system. Each of the strain gauge sensors <NUM> and temperatures sensors are coupled via sensor cables <NUM> and sensor connectors <NUM> to backbone connectors <NUM> of an optical fiber backbone <NUM>. Each backbone connector <NUM> connects sensors from several lashing rods <NUM> to the optical fiber backbone, which runs across the length of the ship in order to provide access to all containers onboard the ship.

An interrogator unit <NUM>, which is preferably housed within the ship, determines lashing rod strain from measurements provided by the sensors <NUM>. The interrogator unit <NUM> is preferably implemented by a Hyperion s255 Hyperion Optical Sensing Instrument, available from Micron Optics, Inc. of Atlanta, Georgia. Individual sensors incorporate a light source having a unique wavelength, and thus are able to continuously and identifiably monitor changes in lashing rod tightness for monitored lashing rods <NUM>. Each backbone connector <NUM> may for example connect up to <NUM> sensors to optical splines that are integrated with the backbone <NUM>.

Some of the sensors <NUM> are fixedly attached to the connectors <NUM>, and some are additionally connected to the connectors <NUM> via one or more free ports <NUM>. Interrogator unit <NUM> is further coupled (for example, via LAN cable <NUM>) to a general purpose computer <NUM> nd associated display <NUM> that funtion to provide a continuous monitoring display and alarm unit for the container lashing gear monitoring system.

Continuous monitoring display and alarm unit <NUM>, <NUM> may preferably display a dashboard that is used by operators to identify alert conditions. On this screen, an operator can see a current status of each lashing rod <NUM> (normal or alarm state), together with strain and historical data. For example, with reference to <FIG>, the user is able to select a particular sensor <NUM> (ID No. <NUM>) that is assigned to a lashing rod <NUM> positioned at bay <NUM>, row <NUM>, tier <NUM>. Graphic <NUM> depicts the location of the associated container <NUM> on deck <NUM> of the vessel <NUM>. Graphic <NUM> indicates that a "tension warning" was initially issued indicating a tension level that exceeds a baseline value (<NUM>"), and a "tension alert" was later issued when the exceeded baseline value remained for a predetermined number of measurement and/or time period. One of skill in the art will readily envision many other modes of display are possible for the monitoring and alarm functions. It is possbile that Interrogator unit <NUM> may be coupled to existing on-board monitoring and alert systems for the purpose of implementing the continuous monitoring display and alarm unit <NUM>, <NUM>.

<FIG> illustrates an exemplary method for operating the container lashing gear monitoring system according to aspects of the present disclosure. suitable software. At step <NUM> of the method, sensors <NUM> are identified and fitted to lashing rods <NUM> according to a selected desgin (for example, as depicted in <FIG>. At step <NUM>, thelashing gear <NUM> is tightened according to accepted specifications. <NUM> At step <NUM>, sensor data is collected at a regular interval (for example, with a frequency of <NUM>), and algorithms are applied to filter increases in strain force that are due only to ship movement. At step <NUM>, additional algorithma are applied to look for sustrained and gradual strains that are indicative of a loosening of associated lashing rods <NUM>. At step <NUM>, an alert decision is made when the change and duration of strain exceed a threshold indicating a loosening of associated lashing rods <NUM>. At step <NUM>, upon receipt of the alert, ship crew are dispatched to mitigate the loosening condition by re-tightening the associated lashing gear <NUM> to prescribed specifications.

It will be understood that, while various aspects of the present disclosure have been illustrated and described by way of example, the invention claimed herein is not limited thereto, but may be otherwise variously embodied within the scope of the following claims. For example, the system may be readily adapted for application to other mechanical systems both onboard the vessel <NUM> (including engine rooms) and/oror other operating environments - for example, including tie rods, foundation bolts and other long bolting arrangements subject to cyclic stress and strain.

The following table lists the reference characters and names of features and elements used herein: Reference characters assigned to method steps are not listed.

Claim 1:
A system for monitoring restraint of one or more containers that have been restrainedly secured to a container ship by one or more restraint members, the system comprising:
the one or more containers (<NUM>);
the one or more restraint members (<NUM>) for restraining respective ones of the one or more containers, wherein the one or more restraint members (<NUM>) each comprise a turnbuckle member (<NUM>) configured for fastening to a fixed point on the container ship via a shackle or fork member (<NUM>);
a plurality of sensors (<NUM>) each configured for monitoring one or more of a compressive or tensile stress or strain in one of the one or more restraint members (<NUM>) wherein each of the plurality of sensors (<NUM>) is fitted on the shackle or fork member (<NUM>) of the turnbuckle member for monitoring stress or strain in one of the turnbuckle members (<NUM>);
a controller (<NUM>) for periodically interrogating each of the plurality of sensors (<NUM>) to ascertain a value of stress or strain detected by the respective sensor; and
a computing device (<NUM>) coupled to the controller,
characterized in that
each of the plurality of sensors (<NUM>) comprise a Fiber Bragg Grating (FBG) sensor configured for measuring the stress or the strain in one of the turnbuckle members (<NUM>);
wherein the one or more containers (<NUM>) that are secured by restraint members (<NUM>) having sensors (<NUM>) for monitoring one or more of compressive or tensile stress or strain are a subset of containers on the container ship;
the computing device (<NUM>) determines whether the value of stress or strain ascertained by the controller satisfies a threshold condition in the FBG sensors.