GB2174347A - Liquid ballasting and de-ballasting systems for a vessel - Google Patents

Abstract

A ballast pumping system for vessels which does not require the ballast tanks to have a separate stripping system. The system can be partially de-ballasted by gravity as well as by pumping. A common central duct 21 stretches along the bottom of the vessel and level with or substantially below the bottom of the ballast tanks, at least one valve is positioned between each tank and the central duct, the valve positioned to fill and substantially completely drain each tank. A pressure relief system is also part of the ballast system. This pressure relief system has a vent trunk 50 connected to the central duct and has an air outlet positioned at a regulation height above the free board deck, the air outlet preventing water from entering the trunk whilst permitting air to enter and exit thus preventing a build up of pressure or vacuum in the central duct. <IMAGE>

Description

SPECIFICATION Liquid ballasting and de-ballasting systems for a vessel The present invention relates to a ballast system for vessels. More particularly, the present invention relates to a system for de-ballasting liquid from ballast tanks without the need of separate stripping systems and discharging ballast water without using pumps.

In some vessels ballast tanks are located within the double bottom structure. Other ballast tanks such as deep tanks, upper wing tanks, side tanks and side hopper tanks may also be arranged as ballast tanks with some of these tanks located up to and sometimes above the water line of the vessel. Ballast tanks may be utilized by filling with water or alternatively, liquid cargo may be stored therein.

Most ballast systems presently provide separate piping and valves to each ballast tank or compartment in conjunction with one or more independent ballast pumps. Present day ballast systems usually include a separate stripping system which has independent suction pumps connected to pipes and valves to strip or drain each tank and compartment.

Each ballast compartment is provided with at least two independent air escape and overflow pipes, larger in diameter than the single inlet pipe and located at the fore and aft ends of each compartment. It has been found that this type of venting system is subject to high friction losses in the pipes with the corresponding additional energy consumption for the handling of water ballast. In addition, there have been numerous incidents in which the structure of the ballast compartments has been seriously damaged by over pressuring when pumping ballast into the tanks.

A recent improvement in ballasting for dry cargo vessels incorporates a large rectangular duct in the double bottom steel structure of the vessel. The central duct extends along the bottom of the vessel to the forward ballast water tank. Such a system is disclosed in U.S. Patent 3,209,715 which issued October 5, 1965. As can be seen in the patent, the central duct acts as a large pipe in which water is transferred by pumps to and from a series of ballast tanks on both sides of the duct. Suction and inlet piping are located in a short transverse duct incorporated in the after end of the main duct. Individual remote operated valves are provided in the side structure of the duct through which the major portion of the water is transferred into and from the tanks.A separate stripping system is provided to drain the tanks, but the major portion of water can be pumped out of the tanks eliminating much of the friction losses which occur in the piping of normal piping systems thus reducing the pump energy required for handling ballast water when compared with standard ballast water piping systems.

A central duct is a steel structure which forms a strength member in hull construction without increasing the weight of the hull. The duct is usually of a sufficient width and depth to also accommodate the piping to fuel oil bunker tanks, and steam heating pipes. The central duct also serves as a ballast compartment when required and can be full or empty without appreciably altering the fore and aft trim of the vessel.

The duct also provides for ballasting of cargo holds when they are used as ballast tanks. For this arrangement, each ballasted cargo hold has an outlet to the central duct which is provided with a blanking plate. In addition, a remotely operated valve is incorporated above the blanking plate in the top of the central duct. When the cargo hold is used for cargo, the blanking plate is locked in the closed position whereby it is impossible to flood the cargo hold from the central duct. A separate cargo hold bilge system is provided in the cargo hold in the normal manner for use when the cargo hold is used for cargo.

This separate bilge system has a shut-off valve incorporated therein whereby the cargo hold bilge system cannot be used when the cargo hold is used as a ballast water compartment. Access to the central duct is arranged via manholes in the top of the duct from the cargo holds. Access to the central duct can also be provided via a manhole in the transverse duct which is accessible when the cargo holds are full. The central duct pumping system can also be applied to tankers for the transfer of oil cargos.

In the past it has been necessary to provide air vent pipes at each end of the duct, however, in a preferred embodiment of the present invention, a single vent trunk is provided at the fore end of the central duct. The vent trunk provides overall venting to the complete ballast system and permits the use of only one air vent pipe per ballast tank, instead of two or more air vent pipes which are normally required to prevent pressure or vacuum damage in the tanks. Such a vent trunk not only provides a vent to stop build up of pressure or vacuum in the ballast tanks, but also provides access from the free-board deck to the central duct without having to go through a cargo hold or the transverse duct.

Existing ballasting systems utilizing a common duct system are not able to utilize efficiently the static head provided by deep ballast tanks or upper wing and side tanks during the de-ballasting or unloading of liquid from the tanks. This is primarily because most de-ballasting systems provide pumps for de-ballasting and the advantage of a positive gravity head with the level of the liquid in the tanks above the vessels water line cannot be used effectively.

It is an object of the present invention to provide a ballast system which can be deballasted, partly by gravity and partly by pump action or partial discharge by gravity head without pump action. This dual discharge feature reduces the de-ballasting times normally reguired for vessels and in addition reduces the energy required.

It is a further object of the present invention to provide a ballast system utilizing a central duct stretching along a portion of the length of the vessel adjacent the bottom of the vessel and level with and/or substantially below the bottom of the ballast tanks, the central duct having valves located between the duct and the ballast tanks such that the tanks may be de-ballasted completely without the need of separate stripping systems.

It is a further object of the present invention to provide a ballast system utilizing a central duct and having a single vertical vent trunk connected to one end of the duct which permits using only a single air vent pipe in each of the ballast tanks, and permits access to the central duct from the freeboard deck. The single vertical vent trunk eliminates possible over pressuring of ballast tanks when they are filled by the ballast pumps.

Yet another feature of the present invention is a preferred embodiment wherein the use of a low sea suction inlet for ballasting a vessel can be omitted by utilizing a common cross pipe extending across the vessel with inlets on both sides of the vessel. Low sea suction inlets some-times allow mud to enter the system, but with inlets on both sides, a constant flow of inlet water is maintained regardless of list or rolling of the ship.

The present invention provides in a ballast system for a vessel including a central duct extending along a portion of the length of the bottom of the vessel, a plurality of ballast tanks in the vessel, adjacent to the central duct with the bottoms of the ballast tanks not below the bottom of the central duct, means for feeding liquid into and means for discharging liquid out of the central duct, the improvement of a discharge system comprising at least one valve between each tank and the central duct, the valve positioned to fill and substantially completely drain each tank without any other draining devices and means for opening and closing each valve by remote control.

In other embodiments of the invention, the valve for each tank is located at the base of an upright wall member between the ballast tank and the central duct. The ballast tanks preferably include a plurality of double bottom ballast tanks on each side of the central duct and at least one deep water ballast tank above the central duct. In another embodiment a plurality of upper wing tanks are provided above the double bottom ballast tanks, each of the upper wing tanks are joined to one of the double bottom ballast tanks by a pipe and each of the upper wing tanks has a vent to prevent pressure or vacuum build up in the upper wing tanks and the double bottom ballast tanks. The vent in one embodiment comprises a single vent pipe extending from the approximate center of each of the upper wing tanks to an outlet above a freeboard deck of the vessel.

The valve is preferably a slide valve having an opening with a bottom lip substantially in line with the bottom of the ballast tank. In one embodiment the slide valve has a gate adapted to slide over the valve opening and has wedge shaped side frames to seal the gate over the valve opening when the valve is closed. In a preferred embodiment the gate is moved by a hydraulic cylinder operator means with a piston which is extended when the valve is open and is retracted when the valve is closed.

The present invention also provides in a ballast system for a vessel including a central duct extending along a portion of the length of the bottom of the vessel, a plurality of ballast tanks in the vessel adjacent the central duct with the bottoms of the ballast tanks not below the bottom of the central duct, at least one valve between each tank and the central duct, and means for opening and closing each valve by remote control, the improvement of a filling and discharging system comprising a transverse duct connected to the central duct, the transverse duct having a first suction outlet connected to a ballast pump with a valve manipulation system to pump liquid from the first suction outlet to a first overboard discharge to de-ballast and to pump liquid from a main liquid suction line to the first suction outlet to ballast, and a second suction outlet in the transverse duct connected by a non-return valve to a second overboard discharge for gravity de-ballasting.

The second overboard discharge is preferably located on the side of the vessel and at a level substantially representing a light ballast condition water line. In another embodiment, the ballast pump connected to the first suction outlet may be bypassed by the valve maniuplation system for gravity ballasting and de-ballasting.

In yet another embodiment, the main liquid suction line comprises a cross pipe extending across the vessel having a water intake on each side of the vessel. A vent pipe is preferably located at the approximate center of the cross pipe.

The present invention also provides in a ballast system for a vessel including a central duct extending along a portion of the length of the bottom of the vessel, a plurality of ballast tanks in the vessel adjacent the central duct, at;least one valve between each of the ballast tanks and the central duct, means for opening and closing each valve by remote control, means for feeding liquid into and means for discharging liquid out of the central duct, each of the ballast tanks having a vent extending above a freeboard deck of the vessel, the improvement of a vent trunk connected to the central duct and extending above the freeboard deck, the vent trunk having an outlet means above the freeboard deck, the outlet means preventing liquid from entering and permitting air entering and discharging from the central duct.In a preferred embodiment, the outlet means in the vent trunk is positioned at a regulation height above the freeboard deck.

In a preferred embodiment the vent trunk includes a vertical ladder and provides access from the freeboard deck to the central duct through the vent trunk. In still another embodiment, the vent means for each of the ballast tanks comprises a single vent pipe extending from the approximate center of each of the ballast tanks to an outlet at a regulation height above the freeboard deck.

In another embodiment, the vent trunk extends up above the freeboard deck into a first compartment which has an intermediate barrier leaving a top space extending into a second compartment having louvers to permit entry and exit of air, and a float valve in the second compartment adapted to seal on a seat positioned above the louvers and below the top space, when water enters the second compartment through the louvers.

In drawings which illustrate embodiments of the invention, Figure 1 is a side elevational view of a vessel showing the location of ballast tanks and central duct, Figure 2 is a plan view of the vessel of Figure 1 showing the location of the central duct and transverse duct, Figure 3 is a cross sectional view taken at line 3-3 of Figure 1, Figure 4 is a partial cross sectional view taken at line 4-4 of Figure 2, Figures 5 and 6 are front elevational views of slide valves suitable for the ballast system of the present invention, Figure 7 is a representative side view of the valves shown in Figures 5 and 6, Figure 8 is a schematic plan view'of one embodiment of the ballasting and de-ballasting system for the ballast tanks taken at line 8-8 of Figure 1, Figure 9 is a cross sectional view taken at line 9-9 of Figure 4 showing a vent trunk at the fore end of the vessel, Figure 10 is a detail cross sectional view taken at line 10-10 of Figure 9 showing an air outlet arrangement for the vent trunk, Figure 11 is a cross sectional view taken at line 11-11 of Figure 10.

Referring now to the drawings, Figures 1, 2 and 3 illustrate a vessel 20 having a central duct 21 which extends from a transverse duct 22 in the engine room along the bottom of the vessel 20 to a vent trunk 50. The central duct 21 has a substantially rectangular cross section with substantially vertical side walls to form connecting upright wall members with double bottom ballast tanks 24 as shown in Figure 3. The double bottom ballast tanks 24 and central duct 21 are located within the double bottom 25 of the vessel 20. Deep water ballast tanks 26 are spaced apart and positioned above the double bottom 25 extending from side to side of the vessel and up to the freeboard deck 27. These deep water ballast tanks 26 extend above the water line of the vessel and thus when being emptied, provide a static head for gravity discharge.

Upper wing tanks 28 are shown in Figure 3 and have a vertical pipe 29 connecting one wing tank 28 to one double bottom ballast tank 24. A single vent pipe 30 on the freeboard deck, located at about the center along the length of the wing tank 28 provides a vent far both the wing tank 28 and the double bottom tank 24. The vent 30 has an outlet arranged to allow air to freely pass in and out but prevent water from above the deck 27 from entering. The outlet of the vent 30 is placed at the regulation height above the deck 27. By having the upper and lower tanks connected obviates the necessity of additional reinforcement of the lower compartment since the total head of liquid in the lower compartment is the same regardless of whether or not there is an upper tank.

Whereas upper wing tanks 28 are illustrated here, both side tanks and side hopper tanks may also be used for ballasting.

As illustrated in Figure 3, the double bottom ballast tanks 24 have a vertical wall member 31 which separates the ballast tanks 24 from the central duct 21. A slide valve 32 is positioned at the base of each vertical wall member 31 and the bottoms of the ballast tanks 24 are arranged to be not lower than the bottom of the central duct 21. The valves 32 have a small bottom lip to allow substantially all the liquid in the ballast tanks 24 to drain into the central duct 21.

Examples of suitable valves 32 are illustrated in Figures 5, 6 and 7 which show a slide valve with a gate 33 to slide down and seal over port 34. Figure 5 illustrates a circular gate 33 and Figure 6 shows a rectangular gate 33. The rectangular gate design provides a straight sill which allows quicker drainage at low levels. As can be seen, the port 34 has a clearance dimension A from the bottom of the flange 35 of the valve to the lowest point in the port 34. This dimension A is preferably in the order of about 50 mm so that when the valve 32 is mounted in the vertical wall member 31, an adjacent ballast tank 24 can completely drain into the central duct 21.

The valve has side frame members 36 with wedge shaped surfaces 37 to match with ta pered surfaces on the gate 33. Thus when the gate 33 moves into the closed position1 the wedged shaped surfaces 37 push the gate against the opening port and seals 38 ensure that liquid does not leak through the port. The operation of the valve 32 is preferably by a double acting cylinder 39 mounted in a yoke frame 40 such that when the gate 33 moves upwards, the piston extends out from the body of the cylinder 39 so that when the valve is in the open position, the piston stem is extended from the valve. When the valve is closed, the double acting cylinder 39 retracts the piston stem so that the stem is not exposed while the valve is closed.This provision prevents sea water or other corrosive liquids from contacting the piston stem of the cylinder 39 when the valve is in the closed position and as the valves normally remain closed except when ballasting and de-ballasting, the life of the valve is longer than those normally used in these locations.

As shown in Figure 4, a vent trunk 50 is provided at the fore end of the central duct 21. The vent trunk 50 extends upwards from the central duct 21 to an air vent positioned at a regulation height above the freeboard deck 27. Details of the vent trunk 50 and air vent will be described hereafter.

As shown in Figure 4, valves 32 for the deep water tanks 26 are placed in a horizontal divider of the double bottom 25 above the central duct 21 so no liquid can remain in the tank 26 once the valve 32 is opened.

At the aft end of the central duct 21 is a transverse duct 22 which, as shown in Figure 8, has a first suction outlet 65 connected to a valve manipulation system-comprising a series of valves 66, connecting pipes 67 and a pump 70. The valve manipulation system permits water or liquid inside the transverse duct 22 to be pumped through the first suction outlet 65 to a first overboard discharge 71 or, alternatively, akes sea water from the main sea water suction line 72 and feeds it to the first suction outlet 65 thus filling the transverse duct 22. As can be seen from the valve manipulation system, the pump 70 may be used or bypassed so that both in filling and discharging the transverse duct 22, the gravity head may be employed depending on the position of the tanks above or below the water line.

The main sea water suction line 72 is shown in Figure 8 as being a cross pipe which extends from one side of the vessel to the other and has a sea water intake 75 on both sides of the hull. The two intakes 75 ensure a flow of water into the suction line regardless of list or roll of the vessel. An air pipe 76 or vent line is located at the approximate center of the cross pipe 72 instead of having individual air pipes with independent shut off valves attached and located at each sea inlet. The central air pipe 76 eliminates the inflow of excess air to the system with its attendant problems.

A second suction outlet 77 is provided in the transverse duct 22 which through a nonreturn self closing valve 78 and an on-off valve 79 feeds to an overboard discharge 80, the discharge 80 is preferably positioned at about the level corresponding to the light ballast condition water line of the vessel. At this position, the maximum gravity head effect can be obtained. By utilizing the first suction outlet 65 and the second suction outlet 77, the ballast can be pumped and gravity discharged at the same time from the transverse duct 22.

By utilizing the two de-ballasting systems, the de-ballasting times for a vessel is reduced.

Furthermore de-ballasting can be carried out by gravity alone without the use of pumps for all ballast above the water line of the vessel.

Gravity de-ballasting provides a savings in energy consumption.

A third suction outlet 81 is illustrated in the transverse duct 22 which feeds through a valve 82 to the main bilge of the vessel where bilge pumps (not shown) discharge the liquid therein overboard. This third suction outlet 81 is generally the lowest outlet in the transverse duct 22 and smaller than the first suction outlet 65, and second suction outlet 77. If this third suction outlet 81 is not connected to the ships bilge, then a separate sea water pump eductor is provided to empty the transverse duct 22. The transverse duct 22 is generally positioned in the double bottom of the vessel in the engine room as shown in Figures 1 and 2. Access to the transverse duct 22, which is generally clear of the cargo holds is via a manhole (not shown), positioned on the top horizontal divider; through a manhole (not shown) in the cargo holds or through the vent trunk 50 and the central duct 21.Access can be achieved through the central duct 21 when the ship is in any condition of loading or ballasting By utilizing two suction outlets 65 and 77, one of which may be connected through a pump and the other which is connected directly to the overboard discharge 80 enables deballasting of the upper ballast tanks to take place in a shorter time than pumping alone.

Both suction outlets 65 and 77 are used to empty the transverse duct 22 and hence the central duct 21. This enables a faster flow of liquid from within the central duct 21 and the ballast tanks.

The vent trunk 50 extends up above the freeboard deck 27 as shown jn- Figure 9. The trunk 50 has a sufficiently large cross section to ensure that pressure build up in the central duct 21 cannot exceed the pressure head representing the pressure atiffereiice from the central duct 21 to the air outlet. This vent trunk 50 provides overall venting of the complete ballast system and enables each individual ballast tank 24 to be provided with only a single air vent 30 provided that the lower inlet of the air vent 30 is located in approximately the center of the tank to vent air pockets that remain in the tank when ballasting or allow air to enter the tank when de-ballasting.

The individual air vents 30 are designed on the basis of air pocket release.

A vertical ladder 90 extends down one side of the vent trunk 50 to provide access to the central duct 21. At the top of the vent trunk 50 is a first compartment 92 located between the freeboard deck 27 and the forecastle deck 93. As can be seen in Figures 10 and 11, the first compartment has an intermediate barrier 94 leaving an air space 95 at the top leading into a second compartment 96 which has louvers 97 to act as the air entry and outlet. A float valve 98 sits on a frame 99 in the second compartment 96 and has a sealing seat 100 located just above the louvers 97 and below the air space 95 so that if water comes in through the louvers 97, the float 98 floats up and closes against the seat 100 preventing water from slopping down the vent trunk 50. The seat 100 is positioned at the regulation height above the freeboard deck 27.

A manhole cover 101 is provided in the wall of first compartment 92 which can be unlatched to allow access to the vertical ladder 90.

Various changes may be made to the embodiments disclosed herein without departing from the scope of the present invention which is limited only by the following claims.

Claims (20)

1. In a ballast system for a vessel including a central duct extending along a portion of the length of the bottom of the vessel, a plurality of ballast tanks in the vessel adjacent to the central duct with the bottoms of the ballast tanks not below the bottom of the central duct, and, means for feeding liquid into and means for discharging liquid out of the central duct, the improvement of a discharge system comprising at least one valve between each tank and the central duct, the valve positioned to fill and substantially completely drain each tank without other draining devices, and, means for opening and closing each valve by remote control.

2. The ballast system according to claim 1 wherein the ballast tanks are positioned on each side of the central duct within a double bottom structure of the vessel, and have substantially upright wall members between the tanks and the central duct, the valve for each tank being located at the base of each of the upright wall members.

3. The ballast system according to claim 1 wherein the ballast tanks include a plurality of double bottom ballast tanks on each side of the central duct and at least one deep water ballast tank above the central duct.

4. The ballast system according to claim 1 wherein the ballast tanks include a plurality of double bottom ballast tanks on each side of the central duct, and a plurality of upper wing tanks on each side of the vessel, each of the upper wing tanks joined to one of the double bottom ballast tanks by a pipe, and each of the upper wing tanks having a vent means to prevent pressure or vacuum build up in the upper wing tanks and the double bottom ballast tanks.

5. The ballast system according to claim 4 wherein the vent means for each of the upper wing tanks comprises a single vent pipe extending from the approximate center of each of the upper wing tanks to an outlet above a freeboard deck of the vessel.

6. The ballast system according to claim 1 wherein the valve comprises a slide valve positioned at the base of an upright wall member between the ballast tank and the central duct, the valve having an opening with a bottom lip substantially in line with the bottom of the ballast tank.

7. The ballast system according to claim 6 wherein the slide valve comprises a gate adapted to slide over the valve opening and has wedge shaped side frames to seal the gate over the valve opening when the valve is closed.

8. The ballast system according to claim 6 wherein the slide valve comprises a gate adapted to slide over the valve opening, a hydraulic cylinder operator means with a piston which is extended when the valve is open and is retracted when the valve is closed.

9. In a ballast system for a vessel including a central duct extending along a portion of the length of the bottom of the vessel, a plurality of ballast tanks in the vessel adjacent the central duct with the bottoms of the ballast tanks not below the bottom of the central duct, at least one valve between each tank and the central duct, and means for opening and closing each valve by remote control, the improvement of a filling and discharging system comprising a transverse duct connected to the central duct, the transverse duct having a first suction outlet connected to a ballast pump with a valve manipulation system to pump liquid from the first suction outlet to a first overboard discharge to de-ballast, and to pump liquid from a main liquid suction line to the first suction outlet to ballast, and a second suction outlet in the transverse duct connected by a non-return valve to a second overboard discharge for gravity de-ballasting.

10. The ballast system as claimed in claim 9 wherein the second overboard discharge is located on the side of the vessel at a level substantially representing a light ballast condition water line.

11. The ballast system as claimed in claim 9 wherein the ballast pump connected to the first suction outlet may be bypassed by the valve manipulation system for gravity ballasting and de-ballasting.

12. The ballast system as claimed in claim 9 Wherein the main liquid suction line comprises a cross pipe extending across the vessel having a water intake on each side of the vessel.

13. The ballast system as claimed in claim 12 wherein the suction line has a vent pipe located at the approximate center of the cross pipe.

14. In a ballast system for a vessel including a central duct extending along a portion of the length of the bottom of the vessel, a plurality of ballast tanks in the vessel adjacent the central duct, at least one valve between each of the ballast tanks and the central duct, means for opening and closing each valve by remote control, means for feeding liquid into and means for discharging liquid out of the central duct, each of the ballast tanks having a vent means extending above a freeboard deck of the vessel, the improvement of a vent trunk connected to the central duct and extending above the freeboard deck, the vent trunk having an outlet means above the freeboard deck, the outlet means preventing liquid from entering the central duct and permitting air entering and discharging from the central duct.

15. The ballast system as claimed in claim 14 wherein the outlet means in the vent trunk is positioned at a regulation height above the freeboard deck.

16. The ballast system as claimed in claim 14 wherein the vent trunk includes a vertical ladder and provides access from the freeboard deck to the central duct through the vent trunk.

17. The ballast system as claimed in claim 13 wherein the vent means for each of the ballast tanks comprises a single vent pipe extending from the approximate center of each of the ballast tanks to an outlet at a regulation height above the freeboard deck.

18. The ballast system as claimed in claim 13 wherein the vent trunk extends up above the freeboard deck into a first compartment, the first compartment having an intermediate barrier leaving a top space extending into a second compartment, the second compartment having louvers to permit entry and exit of air, and a float valve in the second compartment adapted to seal on a seat positioned above the louvers and below the top space, when water enters the second compartment through the louvers.

19. The ballast system as claimed in claim 18 wherein the vent trunk includes a vertical ladder extending up into the first compartment, and includes a manhole cover over an access in a wall of the first compartment.

20. A ballast system substantially as described herein with reference to the accompanying drawings.