GB2279621A

GB2279621A - Building a new marine vessel by a reconstruction method

Info

Publication number: GB2279621A
Application number: GB9413723A
Authority: GB
Inventors: Dimitris Andrew Contos
Original assignee: Renaissance SA
Current assignee: Renaissance SA
Priority date: 1993-07-08
Filing date: 1994-07-07
Publication date: 1995-01-11
Anticipated expiration: 2014-07-07
Also published as: GB9314143D0; GB9413723D0; GB2279621B

Abstract

A method of building a marine cargo vessel of the type having a central section (4) with a substantially uniform transverse cross section situated between a fore section and an aft section (2), the central section (4) comprising outer side members (25), a bottom (15) joining the outer side members (25) and a deck (38), the method including the step of replacing the original central section (4) with a new or substantially overhauled central section including inner and outer side members defining ballasting tanks therebetween. The overall length of the vessel may be increased by the use of a longer new central section or by inserting extension sections (24) in the existing side members (25). The fuel tank (12) is preferably left connected to the aft section (2) and a new bridge structure is preferably installed above an existing bridge structure. The resulting vessel can take advantage of modern vessel design while avoiding the high cost of fabricating new fore and aft sections. <IMAGE>

Description

BUILDING A NEW MARINE VESSEL BY A RECONSTRUCTION METHOD The present invention relates to a process for building by a reconstruction method a new marine cargo vessel of the type having a central section with a substantially uniform transverse cross-section.

Cargo ships are generally considered to have an average life of only 15 to 20 years after which they are usually scrapped. Refitting and overhauling of cargo vessels has hitherto been restricted to gauging parts of the ships structure including the outer hull in order to ascertain which if any of these parts should be replaced due to thinning beyond acceptable limits and in a few cases overhauling of the vessel's-equipment and fittings. The cost of such a thorough overhaul of a vessel may cost as much as twice that of building a new vessel and for this reason is seldom considered economically viable. A further disadvantage of the above type of overhaul is that the advantages of recent developments in vessel design cannot be fully taken advantage of.In general no significant restructuring of the hull is undertaken and finally hull and machinery underwriters and protection and indemnity insurance clubs were reluctant to offer rate differentials therefore there were no actual incentives for the owners to justify the expenditure.

Almost 75% of the world's cargo vessel fleet is over 10 years old and the average age of such vessels is around 18 to 20 years. These facts coupled with the fact that the number of yards suitable for building new cargo vessels has fallen drastically over the last 20 years means that there is an urgent need for a cargo vessel building technique to be developed which is economic to perform.

One object of the invention is to meet this need. A further object of the invention is to provide a cargo vessel building technique which can take advantage of modern developments in the design of such vessels.

According to the invention there is provided a method of building a marine cargo vessel of the type having a central section with a substantially uniform transverse cross section situated between a fore section and an aft section, the central section comprising outer side members, a bottom joining the outer side members and a deck, the method comprising the steps, not necessarily in the following order of either:: (A) replacing the central section with a complete newly constructed one including inner and outer side members defining ballasting tanks therebetween or (Bi) removing outer side members of the vessel from the central section, cleaning, examining and replacing the removed outer sides and substituting new outer side parts where necessary, providing and fixing inner side members spaced inwardly from the outer side members, the side members defining ballasting tanks therebetween, (Bii) removing the deck from the central section and replacing with a new deck, (Biii) removing the bottom of the central section which joins the sides and replacing with a new or fundamentally reconstructed bottom and, (Biv) substantial or complete overhauling fore and aft sections at either end of the central section as required.

Due to the almost complete replacement of the lower cost central section, a vessel may be produced which can reflect modern advances in vessel design yet need not involve the building from start of the relatively expensive fore and aft sections of the vessel. The method can be used to produce a new vessel with a saving in the order of 40% relative to the cost of conventionally building a new vessel having the same specifications. Ballasting and trimming may advantageously be affected by selective filling and emptying of the space between the inner and outer side members.

Due to the over designed scantlings employed in older vessels the existing fore and aft sections and the double side feature adopted for vessels built according to the invention the resulting vessel will be far stronger, last longer and have a higher residual scrap value at the end of its life than a conventionally built new vessel having the same cargo carrying capacity.

Multi purpose container vessels, dried bulk cargo vessels and tankers all typically have such a central section with a substantially uniform transverse cross section and for this reason the method may advantageously be applied to all of these types of vessel.

The condition of the hull and machines, and consequently the value of the vessel, can be maintained in the same order as when the vessel was delivered by the use of an onboard computerised management system (RIME - trade name) designed to monitor/control vessel maintenance. Such a management system may also advantageously be designed to deal with vessel stability, accounting matters, drills (e.g. fire drills) etc.

The length of the central section may advantageously be extended possibly by the insertion of an additional extension section including side and bottor: panels at an appropriate stage in the building process.

This will allow the vessel's overall cargo carrying capacity to be increased as a result of the new building method.

Preferably the majority of the machinery and equipment on the vessel will be replaced. Substantial overhaul in accordance with the findings of vibration monitoring diagnostic surveys may occur in order that the machinery and equipment may be restored to top condition.

The main engine will preferably be replaced by a new engine or fully modernised and brought up to current standards.

By use of the computerised management system (RIME) discussed above, preferably every individual member of the entire hull/structure/scantlings will be identified and measured and its condition will be constantly monitored after the vessel's delivery. This means that the hull/structure/scantlings will also be fully condition monitored in the same way as all other onboard machinery.

Furthermore, advantageously underwater external hull parts are provided with corrosion protection including at least one and preferably all of special coating techniques, sacrificial anode/cathode protection and static protection.

Further full predictive protection may be provided for the machinery and equipment by continuous vibration monitoring and analysis and onboard lubricant oil analysis plus computerised preventive maintenance care for the remaining parts of the vessel. Provided with such protection vessels rebuilt according to the invention are likely to outlive contemporary conventionally built vessels, partly due to the double hull and to the inherently stronger detailing used in the design of the fore and aft sections of older vessels.

Cargo ships of the type described customarily include a fuel tank in the form of a portion of the double skin bottom of the vessel. Such a tank customary extends forwards from the aft section of the vessel along the bottom of the central section and is advantageously left connected to its associated engine/engine rooms accommodated in the aft section of the vessel during the rebuilding of the vessel.

Other aims and advantages of the invention will become apparent to the skilled reader from the following description of a specific example of the process which is made with reference to the following drawings in which: Figure 1A shows in schematic cross section a typical multi-purpose cargo vessel suitable to be used sacrificially when building a vessel using the method according to the invention, Figure lB shows similar view to figure 1A of a new vessel built using the method according to the invention, Figure 2 is a cross-section on the line AA of the vessel shown in figure 1, Figure 3 is a schematic exploded view of the vessel at an intermediate stage of the building process, Figure 4 is a schematic longitudinal cross section of the vessel after completion of building, Figure 5 is a cross section on the line BB of the vessel shown in Figure 4, Figure lA shows a schematic cross section through a multi-purpose vessel 1 suitable for use in the method according to the invention. The vessel 1 includes an aft section 2, central section 4 and a fore section 6. The central section, a cross section of which is shown in figure 2, includes single outer side members 8, bulkheads 11, a double bottom 10 and a deck 3 with hatch covers 7.

The steps involved in the process according to the invention will now be described.

The fore section 6 and the aft section 2 (complete with the fuel tank 20 still attached) are removed from the central section 4.

The fore section 6 receives the following basic treatment. The weather deck and associated machinery and chain locker are removed and scrapped. The external plating is gauged to detect where thinning beyond acceptable limits has occurred and offending plates are removed and replaced with new plates. This gauging may possibly include magnetic testing of welds/seams. The entire fore section is grit blasted internally and externally and the external surface of the fore section is smoothed. A new chain locker, weather deck and associated mooring equipment are Installed. A Bosun's store space is extended and decked at the same level as the deck 3 of the central section. A new top section to the fore bulwark 18 is installed.

The aft section 2 receives the following basic treatment.

The external plating of the aft section 2 is gauged and replaced as required as described above in connection with the fore section and the mooring equipment is discarded and replaced with new equipment.

The rudder, propeller and stern tube liner are removed and the sea chest water intake opening is welded closed and reestablished at a higher level to avoid problems of silt uptake with water drawn into the vessel.

The propeller 41 and stern tube are thoroughly inspected and overhauled and the stern gland seal is replaced with a state of the art long life seal.

The fuel tank 20 which remains connected to the aft section 2 is gas purged, cleaned and cut open by removal of its upper member 12. Gauging of all fuel tank parts followed by replacement as necessary and replacement of the upper member then takes place.

The entire aft section is grit blasted and the exterior is smoothed as described above. Corrosion protection is provided as also described above.

All other equipment and fittings in the aft section are inspected and overhauled or replaced as necessary.

In particular the main engine is removed, thoroughly inspected/gauged and completely overhauled in order that it can be provided with a new serial number. The main engine will be converted to run on oil of 180 cst (centistokes).

The steering gear will also be dismantled, inspected, gauged and overhauled. A new bridge 52 is installed over the existing one 54 which is converted into a day operations room.

The central section 4 receives the following basic treatment.

The majority of the central section 4 is scrapped.

The only parts of the central section retained are the outer side members 8 up to the level of the deck 3.

The original bulkheads 11 and deck 3 are removed and scrapped. In certain circumstances where the new design permits however the bulkheads may be retained for reuse. The outer side members 8 are removed, gauged to detect where thinning beyond acceptable limits has occurred and offending plates scrapped and replaced with new plates.

The outer side members 8 are grit blasted and the entire external surface of the members are smoothed. Each outer side member 8 is then cut vertically so as to enable an extension section 24 of length X to be inserted so as to form a new outer side member of greater length than the original outer side member 8. Where the new design necessitates it or where a substantial proportion of the original outer side members 8 are unacceptably thinned the entire original outer side members 8 may be discarded and replaced with new outer side members of the appropriate length.

The original double bottom 10 is removed and scrapped and a new double bottom 15 is fabricated with a central duct 17 defined by two vertical duct walls 16. The duct 17 separates a port bottom ballast tank 32 from a starboard bottom ballast tank 33. The new double bottom 15 is longer than the old double bottom 10 by the same distance X that the sides are extended by.

The parts shown in figure 3 (with the exception of the bulkheads 23, only one of which is shown, and the new deck 38) are overhauled as described above are then assembled. The new double bottom 15 is connected at its aft end to the fore end of the fuel tank 20 and at its fore end to the fore section 6 of the vessel. The new outer side members 25 (which may comprise the original side members suitably overhauled and extended) are connected along their lower edges to the new double bottom 15, and at their fore and aft ends to the fore and aft sections of the vessel respectively.

After reassembly of the new outer side members 25 with the new double bottom 15, new inner side members 13 (Fig 5) are connected to the inner surface of the outer side members 25. The complete length of the central section on both port and starboard sides of the vessel is provided with inner side members which are spaced from the outer side members by horizontal support walls 28. Each space between and inner and an outer wall constitutes a side ballast tank 30.

New bulkheads 23 and tweendecks 27 (Fig 4) are then installed between the inner side members 13 and the fore and aft section.

A newly fabricated deck 38 is then connected between the new outer side members 25 which includes hatch coamings 34. New hatch covers 36 are provided. The new deck 38 may extend over the central section 4 only or extend over the fore section 6 in addition The total number of holds 45 (5 shown) provided in the built vessel 22 may be different from that provided in the original vessel 1 (4 shown) and very wide hatch coamings 34 are provided. The horizontal tweendeck divisions 27 (only two shown in Figure 4) are hydraulically fully retractable to maximise cargo storage efficiency.

Furthermore the load bearing capacity of the new double bottom 15 is designed to be greater than that of the original double bottom 10 and is also provided with flush container fixing points.

The new deck 38 of the central section 4 has no transverse camber or sheer (ie longitudinal inclination).

Hatch covers 36 are of the universal jack-knife type, hydraulically operable and strengthened to support a load of three tiers of 40 tonne containers.

Transverse box girders 40 are situated under the new deck 38 fore and aft of each hold for accommodating all removable container fittings, semi-automatically controlled ventilation and de-humidification equipment etc... Vertical air ducts are constructed at the transverse bulkheads 23 of each hold 45 and tweendeck 27.

All piping networks from the original double bottom 10 are removed and scraped. Equipment including the electro-hydraulic plant for purposes such as cargo handling, pumping bilges and ballast pumps are removed for scrapping or overhaul and reuse as appropriate.

A bilge network comprising a single trunk pipe 42 running through the duct 17 is installed with branch pipes 44 at each hold 45.

Electrically operated luffing cranes 48 incorporating deck illumination systems and portable electronic weighing apparatus are installed on the deck 38 of the central section 4.

The above description has included only the major steps involved in the building of a cargo vessel according to the invention. Many other minor steps will be involved the nature of which will be apparent to those skilled in the art.

The entirely new or almost total reconstruction of the central section of the vessel as described above permits a vessel to be produced which can benefit from the latest advances in vessel design and permits the resources saved by avoiding the high cost of conventionally building a new vessel to be used to pay for the installation of state of the art vessel control systems and equipment which can assist in allowing the vessel to be operated in a highly efficient manner.

Claims

CLAIMS:

1. A method of building a marine cargo vessel of the type having a central section with a substantially uniform transverse cross section situated between a fore section and an aft section, the central section comprising outer side members, a bottom joining the outer side members and a deck, the method including the step of replacing the original central section with a new or substantially overhauled central section including inner and outer side members defining ballasting tanks therebetween.

2. The method claimed in claim 1 wherein the central section is completely replaced by a newly constructed central section.

3. The method claimed in claim 1 wherein the replacement of the central section involves removing outer side members of the vessel from the central section, cleaning, examining and replacing the removed outer side members and substituting new outer side members where necessary, providing and fixing inner side members spaced inwardly from the outer side members, the side members defining the ballasting tanks therebetween.

4. The method claimed in claim 3 comprising the further step of removing the deck from the central section and replacing with a new deck.

5. The method claimed in claim 3 or 4 comprising the further step of removing the bottom of the central section which joins the sides and replacing with a new or fundamentally reconstructed bottom.

6. The method of claim 3, 4 or 5 comprising the further step of substantially or completely overhauling fore and aft sections at either end of the central section.

7. The method of any preceding claim wherein the length of the central section of the newly built vessel is longer than the original central section.

8. The method of claim 7 wherein extra length is added to the original central section by means of inserting extension sections in the side members, bottom and deck.

9. The method of any preceding claim wherein the majority of equipment on the vessel is replaced.

10. The method of any preceding claim wherein a vibration monitoring diagnostic survey technique is used to ascertain the condition of equipment on the vessel.

11. The method according to any preceding claim including the provision of corrosion protection including at least one of special coating techniques, sacrificial anode, sacrificial cathode and static protection.

12. The method of any preceding claim wherein a fuel tank constituted by a double skin bottom of the vessel is retained connected to the aft section.

13. The method of claim 12 wherein the fuel tank is cleaned and cut open for overhaul by removing one skin of the double skin bottom.

14. The method claimed in any preceding claim wherein an original bridge structure is retained and a new higher bridge structure is connected thereover.

15. The method claimed in any preceding claim including the step of providing a new double skinned bottom for the central section including port and starboard ballast tanks separated by a duct.

16. The method claimed in any preceding claim including the step of providing a longitudinally disposed single bilge draining trunk pipe between upper and lower skins of a double skinned bottom.

17. The method claimed in any preceding claim including the step of providing transverse box girders between deck hatch openings immediately below the deck for accommodating equipment.

18. The method claimed in any preceding claim in combination with a subsequent monitoring method involving identifying and measuring the condition of some or all of hull, scantlings and other structural components of the vessel.

19. The method claimed in claim 18 wherein the subsequent monitoring is carried out with the use of an on board computerised management system.

20. A method of building a marine cargo vessel substantially as hereinbefore described with reference to the accompanying drawings.

21. A marine cargo vessel constructed using the method according to any preceding claim.