WO2009124928A1

WO2009124928A1 - Structural and/or thermal monitoring system for ships

Info

Publication number: WO2009124928A1
Application number: PCT/EP2009/054135
Authority: WO
Inventors: Giuseppe Tassara; Paolo Cappa; Giovanni Tassara
Original assignee: Pegaso Systems S.R.L.
Priority date: 2008-04-09
Filing date: 2009-04-07
Publication date: 2009-10-15
Also published as: ITGE20080025A1

Abstract

Structural and/or thermal monitoring system for ships, in particular bulk carrier cargo ships, container ships, tankers or the like, or platforms, in particular off-shore platforms or the like, which have compartments which are filled with liquid or gaseous products, comprising a series of sensors (5) for detecting the structural and/or thermal stresses, positioned at various predefined points in the hull (2) of a given ship (1) and connected together and to a central reading unit (7) by means of a network of optical fibre cables (6); this central optical reading unit (7) is designed to emit at predetermined frequencies laser signals to said sensors (5); said sensors (5) for detecting the structural stresses and/or for detecting the thermal stresses are positioned, in direct contact with the outer hull (102) or inner hull (202) of the ship or the platform (1), at given predefined points inside said compartments to be filled with liquid or solid products, in particular inside ballast tanks (11) of the ship (1), each of the latter being delimited by sealed bulkheads (12, 102, 202); said optical fibre cables (6) are connected together by means of suitable sealed joining means (14), and means (13) for sealingly guiding said cables (6) through the sealed bulkhead (12, 102, 202) separating the inside and outside of the ballast tank (11) are provided between the inside and outside of a ballast tank (11).

Description

TITLE

"STRUCTURAL AND/OR THERMAL MONITORING SYSTEM FOR SHIPS"

DESCRIPTION The present invention relates to a structural and/or thermal monitoring system for ships, in particular bulk carrier cargo ships, container ships, tankers, for example petrol tankers, or the like, or platforms, in particular off-shore platforms, or the like.

The technology used hitherto for the structural monitoring of ships is based on sensors for detecting the structural and/or thermal stresses, which are mounted transversely and longitudinally at various points and on various levels of a given ship or platform which is to be monitored. These sensors may be connected together and to a central data recording and processing unit by means of a network of electrical cables, in the case of electrical sensors, or by means of a network of optical fibre cables, in the case of optical sensors. The central unit sends, at a predefined frequency, to these optical sensors positioned inside the ship a laser beam which, passing through each of these sensors, triggers sending of a return signal which is processed and recorded. Through the use of optical fibres, since they are inert, it is possible to make the entire system safer and to install the sensors even in points which normally would be dangerous if electrical sensors were used.

The document US 5,942,750 describes a method and a device for continuously monitoring dynamic loads, including the tension and stresses in the hulls of ships, in particular bulk carriers and tankers, comprising an optical transmitter unit, an optical receiver unit and an optical fibre network, where the transmitter unit and the receiver unit are provided inside a central monitoring unit which is connected via an interface to a control system with processor which is in turn connected to a data display and viewing unit; in this system the optical transmission unit comprises at least one first laser which sends an optical signal to the optical fibre cable network, the receiver unit comprises an optical detection system with one or more optical detectors, and an associated optical fibre stress sensor is positioned at a series of predefined measuring points; the optical fibre stress sensors are each connected via the optical fibre cable network to the optical transmitter unit and to the optical receiver unit; the optical fibre cable network is also provided with various generic sensors for detecting the longitudinal stresses.

These known systems mentioned above have various drawbacks, including firstly the fact that these sensors are positioned only in the loading zones of the ship and in zones where no filling of liquid products is performed, for example in the case of double-hull tankers these sensors are in fact positioned only in the part of the hull situated innermost within the ship and therefore the stresses detected may be approximate. In the case of bulk carriers or container ships, these sensors, since they are positioned essentially inside the loading holds, may come into contact with the actual loads and therefore suffer damage following any impacts affecting these loads or the like. In other words, therefore, in the known systems, the sensors for detecting the structural and/or thermal stresses of ships are not positioned directly on the ship hull or at the really critical points of the ship.

The object of the present invention is therefore to overcome the drawbacks of the known systems mentioned above by means of a structural and/or thermal monitoring system for ships which allows a predefined number of sensors to be positioned in direct contact with the outermost part of the hull and also in compartments which are filled with liquid or gaseous products, such as, for example, the ballast tanks of the ship, and therefore allows continuous and highly precise monitoring of data such as: an analysis of the structural fatigue, the shearing force and the bending moment affecting the load-bearing structure of the ship, i.e. the ship's beam, or the stresses locally affecting particular parts of the ship's structure, and the like.

This object is achieved according to the present invention by means of a structural and/or thermal monitoring system for ships, in particular also bulk carrier cargo ships, container ships, tankers or the like, or platforms, in particular off-shore platforms or the like, which have compartments filled with liquid or gaseous products, comprising a series of sensors for detecting the structural and/or thermal stresses, positioned at various predefined points in the hull of a given ship or platform and connected together and to a central reading unit by means of a network of optical fibre cables, said central optical reading unit being designed to emit at predetermined frequencies laser signals to said sensors, characterized in that said sensors for detecting the structural stresses and/or for detecting the thermal stresses are positioned, in direct contact with the outer hull or inner hull of the ship or platform, at given predefined points inside said compartments to be filled with liquid or gaseous products, in particular inside ballast tanks of the ship separated by sealed bulkheads; said optical fibre cables are connected together by means of suitable sealed joining means, and means for sealingly guiding said cables through the sealed bulkhead separating the inside and outside of the ballast tank are provided between the inside and outside of a ballast tank.

Further characteristic features and advantages of the present invention will emerge more clearly from the following description, considered purely by way of a non- limiting example and with reference to the accompanying drawings, in which:

• Fig. 1 shows a schematic side elevation view of a ship at various points of which a series of optical sensors for detecting the structural and/or thermal stresses are positioned and connected to a central reading unit by means of optical fibre cables;

• Fig. 2 shows a plan view of the ship according to Fig. 1 comprising ballast tanks inside which these optical sensors according to the present structural and/or thermal monitoring system are positioned;

• Fig. 3 shows a schematic cross-sectional view of half the hull of a tanker comprising, on the sides and on the bottom of the hull, ballast tanks inside which these optical sensors are arranged;

• Fig. 4 shows a cross-sectional view of a portion of a ballast tank separated by a sealed bulkhead having, passing through it, a device for sealingly guiding the optical fibre cables between the inside and outside of the ballast tank where a sensor is mounted;

• Fig. 5 shows a longitudinally sectioned view of a joint for connecting the optical sensor according to Fig. 4 to this device for sealed guiding through the sealed bulkhead;

• Fig. 6 shows a longitudinally sectioned view of the sealed guiding device of the sealed bulkhead shown in Fig. 4;

• Fig. 7 shows a cross-sectional view of an optical sensor mounted inside the outer wall of the hull inside a ballast tank of the ship.

With reference to these accompanying drawings and in particular to Figs 1 and 2 thereof, 1 denotes a cargo ship, which may be for example a container ship, a bulk carrier, a tanker or the like. This ship 1 comprises a hull 2 shown as having above a deck 3, at the stern of which the ship control room 4 is situated. Ballast tanks 11 , separated by sealed bulkheads 12, are provided inside the hull 2, on the sides and at the bottom thereof. A series of optical sensors 5, for example FBG (Fibre Bragg Grating) optical fibre sensors, for detecting the structural and/or thermal stresses acting on the ship, are positioned inside these ballast tanks 11. These sensors 5 are connected by means of a network of optical fibre cables 6 to a central optical reading unit 7, comprising a control unit for emitting laser rays and a data processing and recording unit. This central data processing unit 7 is positioned inside the operating and control room 4 of the ship and has, departing therefrom, a main cable line 8 positioned along the deck 3 of the ship and containing one or more, multi-fibre or single fibre, optical fibre cables. This main cable line 8 comprises longitudinal nodes 9 having, extending from them, transverse branches 10 for connection to additional lateral nodes 9' from which the various optical fibre cables 6 extend and reach the sensors 5 positioned at the various points of the ballast tanks 11.

Fig. 3 shows a schematic transverse view of half of the hull of, for example, a tanker. This hull 2 comprises, on the sides and at the bottom of the ship, an outer sealed wall 102 and an inner sealed wall 202 between which the various ballast tanks 11 are defined, each of the latter being delimited by the sealed bulkheads 12, 102, 202, 103. Advantageously, as mentioned previously, optical sensors 5 for detecting the structural and/or thermal stresses acting on the ship hull are positioned at various points of these ballast tanks 11. These sensors 5, as can be seen, are connected to the lateral node 9' by means of a series of associated optical fibre cables 6. It should also be noted that, in order to form a chain of optical sensors, the latter may also be connected together by means of such optical fibre cables 6. These single fibre or multi-fibre cables 6 may be reinforced with a plastic sheathing or a reinforcement consisting of steel, kevlar or other similar material able to guarantee a high impact strength and resistance to shearing forces and a long working life in compartments which are filled with liquid materials, which may also be of an aggressive, corrosive or similar nature, so that they may be positioned for example inside the ballast tanks without the need for ducts, tubes or other forms of protection.

Fig. 4 shows by way of example one of the optical sensors 5 mounted inside the outer wall 102 or inner wall 202 of the hull 2 and positioned inside any one of the ballast tanks 11 described above. This ballast tank 11 is separated from the outside by means of a sealed bulkhead, for example the inner wall 202 of the hull. A device 13, which will be described in detail below, for sealingly guiding the optical fibre cables through the bulkhead, is fixed by means of welding to this bulkhead 202. The figure shows two optical fibre cables 6' and 6" which are connected by a joint 14 which may be formed by means of sealed optical connectors or optical connectors protected with a metal or plastic tube closed at the end by seals or watertight rings held by means of cable glands or the like or optical connectors protected by a plastic or metal box-shaped body filled with glues or other liquid-resistant insulating materials.

Fig. 5 shows in detail the type of joint 14 for connecting together the two sections 6' and 6" of an optical fibre cable, described above. This joint comprises a first box- shaped body formed by a first box-shaped part 15 which is open on one side and inside which, via this open side, a second box-shaped part 16 is inserted, the latter also comprising a side open towards the end wall of the first box-shaped part 15. A layer 17 of sealing material, such as silicone or other filler material, is injected between these first and second box-shaped parts 15 and 16. This second box- shaped part 16 receives, positioned inside it, a second box-shaped body comprising a first box-shaped part 18 having an open side via which a second box-shaped part 19 is engaged, the latter also having a side open towards the end wall of the first box-shaped part 18. Said second box-shaped body has, formed inside it, a seat 20 housing two connectors 21 for connecting together two sections 6' and 6" of an optical fibre cable. As can be seen, the walls of the second box-shaped part 16 of the first box-shaped body are inserted inside the first box-shaped body 15 so as to leave suitable gaps - filled by the layer 17 of sealing material - between them and the side and end walls of said first box-shaped part. Moreover, a gap is also left between the second box-shaped body and the inner walls of said second box-shaped part 16 of the first box-shaped body so that the layer 17 of sealing material completely surrounds the second box-shaped body formed by the parts 18 and 19. The end walls of all the box-shaped parts 15, 16, 18 and 19 are also provided with through- holes for allowing said optical fibre cable sections 6' and 6" to pass through the joint 14. This second box-shaped body composed of the parts 18 and 19 may be designed with an ogive, parallelepiped, cylindrical or other shape. As an alternative to the engaging-type system, these parts 18 and 19 may be joined together by superimposing said parts with the aid of clamps or the like. Fig. 6 shows a detailed longitudinally sectioned view of the sealed guiding device 13 of the sealed bulkhead 202. This sealed bulkhead 202 has a through-hole 22 inside which a cylindrical body 23, which is fixed thereto by means of welding, is inserted. This cylindrical body comprises internally a through-hole 123 and at each end an externally threaded section 223. Opposite this section 223 externally the through- hole 123 of the cylindrical body 23 has a frustoconical section increasing towards the outside of said body. A tubular member 24, coaxial with this cylindrical body 23 and longer than the latter, is seated inside the through-hole 123 of this cylindrical body 23. This tubular member 24 has internally a threaded through-hole 124 and at one end a flange 224. The optical fibre cable 6" passes through this through-hole 124 of said tubular member 24 from one side to the other of the sealed bulkhead 202. A nut 25, which has a through-hole 125 through which said tubular member 24 passes, is screwed onto each of the externally threaded sections 223 of the ends of the cylindrical body 23. A frustoconical seal 26 is positioned around this tubular member 24, between each of these nuts 25 and the frustoconical section formed in the through-hole 123 of the cylindrical body 23, opposite the sections 223. At the end of the tubular member 24 provided with the flange 224 a hub 27 which is externally threaded and internally hollow for receiving the optical fibre cable 6" is screwed inside the through-hole 124. This hub 27 comprises an external head 28 which bears against the flange 224. Two sealing rings 29 are provided between this external head 28 and said flange 224. The inside of the through-hole 124 of the tubular member 24 is provided with a first cylindrical seal 30 positioned around the optical fibre cable 6" and consisting preferably of inert, intumescent and heat-expanding material, for example a graphite-based material or the like.

The end of the tubular member 24 opposite to that where the flange 224 is positioned is provided with a second cylindrical seal 31 positioned around the optical fibre cable 6" and consisting preferably of a silicone or polyurethane based material or the like. This hub 27 with its head 28 could alternatively be replaced by a cylindrical seal similar to the second cylindrical seal 31 which surrounds the optical fibre cable 6". The optical sensors 5 used may be of a different type, such as straight FBG optical sensors with a long base, short base, spot-like or rose-like form, or any other form suitable for detecting the deformations at the point considered.

For example, a particularly suitable sensor is the optical sensor 5 shown in Fig. 4 and mounted inside the ballast tank of the ship. This sensor 5 comprises an encapsulation, for example made of composite material, containing FBG sensors for measuring the structural stresses or performing the temperature measurements. Depending on the hull zones on which detection of the structural and/or thermal stresses is performed, these sensors may be positioned in series in the form of a chain interconnected by cable sections which are suitably protected. At each monitoring point the sensors may be arranged longitudinally or transversely with respect to the ship beam or longitudinally and transversely (L-shaped arrangement). By means of this latter L-shaped arrangement it is possible to determine the twisting forces acting on the ship at the various points by means of suitable calculation methods.

Fig. 7 shows the wall 102 or 202 of the hull 2 of the ship on which wall the sensor 5 is mounted. The sensor 5 is fixed to the wall 102 or 202 of the hull by means of a layer 32 of adhesive material, preferably based on epoxy glue. This glue fixes the sensor 5 directly onto the polished metal of the hull wall, advantageously avoiding the use of welds which may adversely affect the solidity of the sheet metal. When the sensor 5 is fixed to the wall 102 or 202, it is kept in position on the sheet metal of the hull by means of a series of magnets, for example neodymium or similar magnets, with a strong magnetic action for as long as the sensor 5 is firmly secured to the sheet metal. Once the layer 32 of adhesive material has solidified, the magnets are removed. This sensor 5, once fixed to the wall 102 or 202 of the hull 2 by means of the layer 32 of adhesive material, is covered by a layer 34 of sealing material, preferably silicone-based, or similar materials. This layer 34 is particularly resistant both to water and to any impacts and may also, if necessary, be walked on if positioned in walking zones, without adversely affecting the correct operation of the sensor for detecting the structural and/or thermal stresses. In order to detect the deformations associated with the groundswell, the present system may be equipped with a tri-axial accelerometer positioned, for example, in the bows zone of the ship, which device will use the optical fibre sensors in order to detect the movements of the ship and the consequent deformations associated with the groundswell. The points where the sensors are positioned may be those which, based on a structural analysis, for example using finite-element calculation systems, are most susceptible to the continuous stresses or in absolute terms inside the individual section of the ship. Moreover, different sections may be chosen for monitoring, for example by identifying the most critical sections in the bows, in the midship zone, at the stern, etc.

During operation of the present system, the central reading unit 7 emits a laser beam with a certain frequency which reaches the sensors 5 positioned at the various points in the ship and is reflected, recording the length or the compression of the sensor Bragg grating or the deformation following a thermal stress. In this way the stresses acting on specific points of the sheet metal are determined, with the possibility of obtaining data such as the fatigue analysis thereof, the bending moments, the shearing forces or the deformations of the ship's beam, and this data may be compared with the data which is obtained using finite-element calculation procedures. For example, the data obtained by the present system may be compared with and/or combined with the systems for theoretical calculation of the stresses which the ship is reckoned to sustain during the various loading and unloading procedures. All this will enable the data to be validated in response to factors which cannot be predicted by the calculation systems, such as the real wear of the ship structure, the weight of the load, in particular in the case of bulk carriers and container ships, the surrounding sea weather conditions, etc. This data is stored in a recording unit comprising a backup unit which records all the data supplied by the central reading unit 7 on one or more disks. The present system is moreover able to detect modifications to the recorded data by calculation of a code based on the current and prior data measured, which code is added to the data recorded by the sensors. Moreover, the layer 34 of sealant covering each sensor may be provided with an identification means, for example a seal or a stamp which, during an inspection, will reveal any attempt to tamper with the sensor.

Claims

1. Structural and/or thermal monitoring system for ships, in particular bulk carrier cargo ships, container ships, tankers or the like, or platforms, in particular off-shore platforms or the like, which have compartments which are filled with liquid or gaseous products, comprising a series of sensors (5) for detecting the structural and/or thermal stresses, positioned at various predefined points in the hull (2) of a given ship (1 ) and connected together and to a central reading unit (7) by means of a network of optical fibre cables (6), said central optical reading unit (7) being designed to emit at predetermined frequencies laser signals to said sensors (5), characterized in that said sensors (5) for detecting the structural stresses and/or for detecting the thermal stresses are positioned, in direct contact with the outer hull (102) or inner hull (202) of the ship (1 ), at given predefined points inside said compartments to be filled with liquid products, in particular inside ballast tanks (11 ) of the ship (1 ), each of latter being delimited by sealed bulkheads (12, 102, 202), said optical fibre cables (6) being connected together by means of suitable sealed joining means (14), and means (13) for sealingly guiding said cables (6) through the sealed bulkhead (12, 102, 202) separating the inside and outside of the ballast tank (11 ) being provided between the inside and outside of a ballast tank (11 ).

2. Monitoring system according to Claim 1 , characterized in that each of said sensors (5) is fixed to the hull (102) of the ship (1 ) by means of at least one layer (32) of adhesive material and covered by means of at least one covering layer (34) consisting of sealing material.

3. Monitoring system according to Claim 1 , characterized in that said means for joining said optical fibre cable sections (6', 6") comprise a box-shaped body (15, 16) inside which connectors (21 ) for connecting said optical fibre cable sections (6', 6") are housed, at least one layer (17) of sealing material being injected inside said box- shaped body (15, 16).

4. Monitoring system according to Claim 3, characterized in that said first box- shaped body comprises a first box-shaped part (15) which is open on one side and inside which a second box-shaped part (16) also comprising a side open towards the end wall of the first box-shaped part (15) is inserted, at least one layer (17) of sealing material being injected between said first and said second box-shaped parts (15, 16) and said second box-shaped part (16) receiving, positioned inside it, said second box-shaped body comprising a first box-shaped part (18) having an open side via which a second box-shaped part (19) having a side open towards the end wall of said first box-shaped part (18) is inserted.

5. Monitoring system according to Claim 4, characterized in that said box-shaped parts (18, 19) of said second box-shaped body are joined together by means of engagement, supehmposition, or using clamps or the like.

6. Monitoring system according to Claim 1 , characterized in that said sealed guiding means comprise a cylindrical body (23) fixed to the sealed bulkhead (202) separating the outside and inside of the ballast tank (11 ) and comprising internally a longitudinal through-hole (123) which sealingly receives a tubular member (24) having longitudinally a through-hole (124) through which one or more optical fibre cables (6) pass, seals (30, 31 ) being provided between said optical fibre cables (6) and the wall of said through-hole (124).

7. Monitoring system according to Claim 6, characterized in that said cylindrical body (23) comprises at each end: externally a threaded section (223) and internally a section of said through-hole (123) with a frustoconical section increasing towards the outside of said cylindrical body (23), each end of said through-hole (123) having inserted around the outer surface of said tubular member (24) at least one frustoconical seal (26) held in position by means of a fixing nut (25) mounted around said tubular member (24) and tightened on said threaded section (223) of the cylindrical body (23).

8. Monitoring system according to Claim 6, characterized in that at at least one end said through-hole (124) of said tubular member (24) is threaded, said threaded end of said through-hole (124) receiving, screwed therein, a hollow hub (27) passed through by the optical fibre cable (6) and having on the outside of the tubular member (24) a head (28) able to bear against a flange (224) provided around said end of said tubular member (24) and sealing means (29) being provided between said flange (224) and said head (28).

9. Monitoring system according to Claim 6, characterized in that the inside of the through-hole (124) of the tubular member (24) is provided with a first cylindrical seal (30) positioned around the optical fibre cable (6") and consisting of inert, intumescent and heat-expanding material, such as a graphite-based material or the like.

10. Monitoring system according to Claims 6 and 8, characterized in that the end of the tubular member (24) opposite to that where the flange (224) is positioned is provided with a second cylindrical seal (31 ) positioned around the optical fibre cable (6") and consisting of a silicone- or polyurethane-based sealing material or the like.

11. Monitoring system according to Claim 6, characterized in that said cylindrical body (23) is inserted inside a through-hole (22) formed in said sealed bulkhead (202) and fixed thereto by means of welding.

12. Monitoring system according to Claim 1 , characterized in that said central data reading unit (7) is positioned inside the operating and control room (4) of the ship and has, departing therefrom, a main cable line (8) positioned along the deck (3) of the ship and containing one or more, multi-fibre or single fibre, optical fibre cables

(6), said main cable line (8) comprising longitudinal nodes (9) having, extending from them, transverse branches (10) for connection to further lateral nodes (9') from which the various optical fibre cables (6) extend and reach the sensors (5) positioned in particular at the various predefined points of the ballast tanks (11 ).

13. Monitoring system according to Claim 1 , characterized in that said central reading unit (7) comprises means for processing and storing the data received from the structural and/or thermal monitoring sensors (5), each sensor (5) being provided with a given code for the secure management of said data.

14. Monitoring system according to Claim 1 , characterized in that each of said sensors (5) is provided with a specific identification means, such as a seal or a stamp.

15. Monitoring system according to Claim 1 , characterized in that, during loading and unloading of the ship, the shearing forces and the bending moment calculated with the real data supplied by the sensors is compared with the data calculated theoretically by the loading instrumentation of the ship.

16. Monitoring system according to Claim 1 , characterized in that said single fibre or multi-fibre cables (6) are reinforced with a plastic sheathing or a reinforcement consisting of steel, kevlar or other similar material.