Ships – Ballasting – Water tanks
Reexamination Certificate
2003-07-10
2004-07-27
Sotelo, Jesus D. (Department: 3617)
Ships
Ballasting
Water tanks
C114S07400A
Reexamination Certificate
active
06766754
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods and apparatus for controlling the intake, exchange and discharge of seawater ballast from marine vessels such as VLCC, container ships, oil tank ships and the like.
BACKGROUND OF THE INVENTION
In order to maintain the stability and safe operation of an empty or partially loaded marine cargo vessel, it is necessary to add seawater to the ballast tanks to trim the vessel and/or to attain a predetermined draft.
In many instances, cargo vessels take on seawater as ballast in a first port, transport the seawater as ballast many thousands of miles to a second port where cargo is loaded and the seawater ballast discharged into the local harbor or mooring site. It has been well documented that seawater ballast loaded at one location can contain a variety of living organisms ranging from microscopic bacteria to marine plants, fish, crustaceans and other marine life that can have a negative ecological impact when discharged into the local waters at the port of call. Although some efforts have been undertaken to reduce this problem by providing at least a crude filtration system to prevent the intake of rodents, fish, crabs and the like, these efforts have not been particularly effective.
Large volumes of water must typically be introduced into the vessel's ballast tanks and the loading must be done as quickly as possibly due to the large demurrage fees associated with the inefficient loading or idling of commercial marine vessels. Improved methods and apparatus are needed to eliminate or substantially reduce the adverse effects associated with current marine shipping practices that transport and discharge at remote locations large volumes of water that can contain biological and marine life that can have an adverse impact on the marine ecology at the point or points of discharge.
A method and apparatus that includes a bow intake conduit and that utilizes the difference in hydrodynamic pressure for effecting an exchange of water in ballast tanks while the ship is underway is disclosed in U.S. Pat. No. 6,053,121. Pressurized fresh seawater from a main conduit containing fresh seawater is introduced at the bottom of one end of a ballast tank and a valved bottom drain at the opposite end of the ballast tank discharges the water through the underside of the hull into the sea. As disclosed in the '121 patent, based upon laboratory experimental data, after six hours of operation of a small-scale system, a salt water solution in the primary tank was diluted to 25% of its original salt content. There is no suggestion or teaching in the disclosure of the '121 patent that water in the ballast tank should be discharged through a port or outlet at the top of the ballast tank, nor does it disclose the desirability of the removal of biological marine life from the ballast tank.
It is therefore an object of this invention to provide a method and apparatus for rapidly exchanging seawater ballast from marine vessels that eliminates or greatly reduces the transport of the original ballast over great distances from the origin of the ballast, along with the marine organisms entrained therein.
It is a further object of this invention to provide an efficient and economical apparatus for introducing and discharging seawater ballast into the ballast tanks of a marine vessel while the vessel is underway.
Yet another object of the present invention is to provide a method and apparatus that permits the ready control of the volume of seawater ballast, as well as its position in any one or more ballast tanks in the vessel, while minimizing the utilization of pumps and power that must be provided while the vessel is underway.
SUMMARY OF THE INVENTION
The above objects and other advantages are achieved through the apparatus and method of the invention in which water is continuously admitted through at least one opening in the bow of a ship and transmitted through one or more main conduits communicating with the bow opening for distribution into the bottom of a ballast tank to displace existing ballast water upwardly through the tank and discharging the ballast water into the sea through one or more overflow discharge ports or outlets that are positioned at an upper-most point of the ballast tank as close to the shear strake as possible.
As the ship advances, the seawater is admitted through the one or more bow openings and is distributed into the lower regions of the ballast tanks and rises to overflow through the discharge ports in each of the ballast tanks to which it has been admitted. The overflow is discharged into the sea. The greater the ship's forward speed, the greater will be the volumetric flow of water through the main conduit(s) and thereafter through the ballast tanks and discharge ports.
In a particularly preferred embodiment, two bow openings are provided, each opening is provided with at least one valve communicating with a main conduit and each conduit has valved outlets that extend to or through each of the plurality of ballast tanks along the length and on either side of the centerline keel. At least one inlet T-fitting or branch line is provided to introduce fresh sea water from the main conduit into the bottom or lower region of the respective ballast tanks.
In a further preferred embodiment, a plurality of inlet openings to each ballast tank are provided from the main conduit to maximize the flow and distribution of incoming seawater to all of the lower regions of the ballast tank in order to facilitate the flushing effect and the replacement of existing ballast water. The positions of the multiple inlet openings are selected based upon the existing bulkheads, stringers, baffles and structural elements inside each of the ballast tanks.
In another preferred embodiment of the apparatus and method of the invention, each of the T-fittings to the ballast tank is provided with at least one, but most preferably two sequential valves that are controlled by hydraulically-operated actuators. The valves are positioned between the main conduit and any discharge of suction bellmouth(s). The use of two valves in series provides an added margin of safety in the event of a malfunction or blockage in one of the valves. The operation of the hydraulic actuators is preferably directed from a control panel located in the cargo control room, bridge and/or another operations area of the ship. As a further safety precaution, manually operable valve positioners can also be provided for each valve.
The installation of at least two valves at the one or more bow intake openings is also preferred. In order to protect the valve from impact with submerged debris, a high-strength intake guard, such as a grid of steel or stainless steel bars can be provided. The primary control valve for admitting seawater is preferably a ball valve with a hydraulic actuator. Behind the ball valve is preferably installed a double gate valve, also fitted with a hydraulic actuator. The bow openings can optionally be fitted with one or more hydraulically-operated doors or covers. In the event of an accidental failure of the hydraulic power system, the bow doors fail-safe to the closed position. The intake valves are also constructed to return to their closed position in the event of a power failure.
The apparatus and its method of operation differs from the prior art in which the intake ports for the ballast water are typically located at the rear of the ship in the vicinity of the pump room. As will be appreciated by those of ordinary skill in the art, a considerable amount of energy is required to power the pumps in view of the large volume of water that must be displaced. Moreover, the prior art systems and methods of operation provide only for the dilution of the water that has been drawn into the ballast tanks during the unloading of the ship. This limitation of the prior art is overcome by the present invention where the ballast water is displaced upwardly to be discharged from the top of the tanks, rather than the bottom of the tanks as in the prior art.
The intro
Abelman ,Frayne & Schwab
Saudi Arabian Oil Co.
Sotelo Jesus D.
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