US3722690A

US3722690A - Apparatus for skimming oil

Info

Publication number: US3722690A
Application number: US00162161A
Authority: US
Inventors: B Stenstrom
Original assignee: Gulf Oil Corp
Current assignee: Chevron USA Inc
Priority date: 1970-11-09
Filing date: 1971-07-13
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27

Abstract

A collapsible flotation buoy is disclosed for skimming an oil layer from water in a tanker. The buoy is provided with mechanical folding means for collapsing the buoy, permitting its insertion into a narrow opening at the top of the tank. The folding means is remotely controlled to permit expansion of the buoy for use when it is inside the tank.

Description

United States Patent I 1 Stenstriim Mar. 27, 1973 [54] APPARATUS FOR SKIMMING OIL UNITED STATES PATENTS Inventor: Biirie Slensiriim, Enebyberg, 3,667,609 6/1972 Daniel ..2l0/DIG. 2| Sweden 3,534,859 10/1970 Amero et al ..210/242 [73] Asslgnee: (32 Oil Corporation, Pittsburgh, Primary Examiner Reuben Friedman Assistant Examiner-T. A. Granger [22] Filed: July 13, 19 Att0rneyNeyer Neishloss et a1.

21 l. N 162 161 l 1 App 0 57 ABSTRACT [30] Foreign Application Priority D t A collapsible flotation bnoy is disclosed for skit nming an oil layer from water in a tanker. The buoy is pro- N0v.9, Sweden vided mechanical means for collapsing the buoy, permitting its insertion into a narrow open- [52] US. Cl. ..210/242, 210/1316. 21 ing at h top f h tank The folding means is [51] hit. Cl. ..C02b 9/02 remotely controlled to permit expansion of the buoy v [58] Field Of Search ..2l0/83, 242, DIG. 21 for use when it is inside h tank [56] References Cited 7 Claims, 8 Drawing Figures PATENTEDHARZHSH 3 722, 90

SHEET 2 BF 5 INVENTOR.

Bb'rje Sfens fr'o'm PATENTEUHARZYIHTS 3,722,590

SHEET 3 BF 5 INVENTOR.

Bb'rje Sfens frb'm PATENTEDHARZYIQYS 7 ,59

SHEET u 0F 5 INVENTOR.

Bbrje Sfensfrbm APPARATUS FOR SKIMMING OIL The present invention relates to a solution of the problem of cleaning oil tanks, and in this connection, large containers on board tanker ships as well as oil tanks on land are considered. The term oil was used to designate both refined petroleum products and crude oil, however, it should be pointed out that the problem in question is most pronounced in the case of containers for crude oil.

When a crude oil tanker has discharged its cargo in its home port, the partitions of the cargo tanks have to be cleaned before a fresh load can be taken on. One method for carrying out this cleaning which is common at the present time, consists in spraying the sides of the tanks with water. For this purpose, a suitable number of spray devices are used, which can either be permanently installed in the top of the tank, or temporarily lowered into the tank in connection with the cleaning. Every such device has a spray nozzle which is swingable in at least one plane. The water is ejected at very high pressure and in very large quantities, so that the most effective possible washing away of the oil residues, and rinsing of the tank walls is achieved. It is also common to add some cleaning agent to the water. As a result of what has just been said, however, the application of such a method makes for a very large volume of a mixture of oil and water and, perhaps, cleaning agent, that is to say, polluted water. It is a known fact that for a long time it has been customary to pump all this liquid into the ocean, making for considerable damage to the environment. On the other hand, the retention of this relatively large amount of water on board, and its discharge only on returning to the loading port, requires the installation on board of suitable storage tanks for this purpose, which implies increased cost, instead. In illustration of the extent of the problem, it can' be said that a so-called super-tanker, after discharging, has about 1,000 tons of oil residues in its tanks.

However, the difficulty of producing an effective cleaning, and the difficulty of handling the large quantity of polluted cleaning liquid, form aspects of the total problem with which the invention is concerned. A third equally important aspect is connected with the fact that the oil residues also entrain a risk of explosion. When an oil tanker has been emptied and hence for the most part is full of air, the oil residues on the sides of the tanks give off gases and this results in an air-gas mixture which, at certain concentrations of gas, becomes explosive. These concentrations correspond to an explosive mixture. range which has a lower and an upper limit. It

follows from this that it is possible to eliminate the risk of explosion by either reducing or increasing the relative gas content. Reduction of the gas content can be done by forced ventilation of the inside of the tank, while a displacement of the mixture ratio to a level about gas contents which fall within the explosive range can be accomplished by evacuating the air in the tank. This is done in practice in such a way that an inert gas in introduced in place of the air. None of these methods, however, makes for a satisfactory solution of the problem of eliminating the risk of explosion. Aside from the fact that they require installation and operation of a comparatively extensive amount of auxiliary equipment, it will be clear that the protective measures in question, in order to be effective, must be carried out continuously for the whole time often several weeks while the tanker is on its return voyage to the loading port. Even an occasional interruption of the ventilation can lead to a rise in the gas content to a dangerous level, and correspondingly, unless the tanks are continuously checked for a sufficient quantity of-inert gas, a leakage of air will make the oxygen content of the tanks atmosphere rise from the over-rich range into the danger zone. Another natural consequence of these conditions is that a breakdown in the ventilation or protective gas installations means an unavoidable moment of risk. In addition, the situations in which such breakdowns can occur or can be feared, are the same in which the risk of fire is greater, for example on running aground, or in a collision, or when repair work has to be done in the tank, particularly for maintenance of the abovementioned equipment.

It should be pointed out here, that the cursory cleaning of the tank sides achieved by spraying and rinsing according to the above, does not eliminate the risk of explosion. On the contrary, this treatment can trigger an explosion, depending on 7 whether the water is ejected in the form of drops, and with such dynamic energy that'the resulting electrostatic charge entrains such powerful field strengths that discharge by sparking occurs. It should also be noted that neither application of the ventilation principle nor introduction of an inert gas in the tank has any cleaning effect, the function is purely protective. I

The object of the invention is to provide a method for tank cleaning which forms an integral solution of the problem in question, that is to say both protection against risk of explosion and complete cleaning, without difficulties in handling occasioned thereby. More specifically, the invention relates to a method of tank cleaning in two stages, the removal of oil residues by collection of oil from an oil layer floating on a ballast of water inside the tank, and a subsequent, conventional cleaning of the tank sides by spraying.

The introduction of water ballast inside a tank, so that as the water level rises a substantial part of the oil residing on the tank sides comes away and forms an oil layer on top of the water, is already known. This layer was then collected with the aid of long gutters inside the upper part of the tank, for example on the top of a bulkhead. This method, which 'can thus be characterized as being entirely analogous to thesystem used in stationary cleaning installations for waste water, is entirely unsatisfactory for a'ship under way. The invention is based on the realization that an effective collection of such an oil layer floating above a ballast of water can be accomplished with the aid of a number of buoylike devices floating in the mixture of oil and water, with openings at the level of the oil layer, through which the oil can enter, and be carried away from the tank through a hose or pipe.

As mentioned above, the collection operation is designed to be followed by a washing operation. Ac-

cording to a preferred form of execution of the invention, however, the spray devices, with the aid of which the second treatment stage is carried out, can also be utilized during the oil collection phase, in such a way that they subject the outer surface of the liquid mixture to an action promoting the movement of the oil toward the buoy or buoys.

The invention'also envisages a device for execution of the above-mentioned method. The principal characteristic of the device is that it consists of a number of buoys, each of which consists of both a floating body and at least one oil collection chamber, disposed thereunder and with a substantially funnel-like shape,

which chamber communicates through a hose or pipe with a container to receive the oil.

A particular advantage of such buoys is that they can be made collapsible, hence the system can also be available for use on tankers whose tanks can be entered from the deck only through relatively narrow, usually circular openings of the man-hole type.

' which is suitable for practical use thereof.

FIG. 4 shows in perspective, a buoy with its auxiliary equipment, permanently installed inside the tank.

FIG. 5 shows an axial section through a buoy, whose collection funnel is divided into two separate chambers for staged collection of the oil.

The device shown in FIG. 1 is built around a central pipe 11, which is attached by its lower end to a bottom plate 12. The latter is connected in turn, by means of a number of rods 13, with a flange 14 disposed axially thereunder. To'the latter, a downward pointing pipe 15 is welded, and this pipe .15 in turn communicates, by

nected to the buoy, but instead there is a number of slots there, or other openings. The space between the bottom of the buoy and the cloth 29 assumes the form of a funnel, and when the buoy is floating on the mixture of water and oil, the oil layer can pass into this funnel as shown by arrows 30. The oil continues via the center'hole in flange 14 and pipe 15 into hose 17 and it is then drawn off therefrom by means of a pump not shown. Asthis is taking place, the resulting density of the water mixture rises. Thanks to the fact that the buoy has large cross dimensions in relation to its height and bulk, these variations in density will have a negligible influenceon the displacement of the buoy. The oil intake openings will therefore always be at a suitable level, so that for the most part, only oil is' sucked in. The exact proportions of the buoy in this respect will, of course be selected according to cases, but it can be mentioned here that practical experiments revealed that in an oil tanker whose tanks, after discharging, were filled with a ballast of water, as high as possible, there was an oil layer about 25 cm thick on topof the water. With a device according to the invention, so

precise a separation can be achieved that 95 98 percent of this amount of oil was removed.

FIG. 2 shows the, device according to FIG. 1 in a collapsed state. ln this condition, as can be seen, the largest transverse dimension is very small, and the device can therefore be lowered through manholes and the like openings in the ships deck, for example an opening as shown at 31 in FIG. 2. How the device can be so lowered is illustrated in FIG. 3a-3d. As these figures show, device 10 is introduced through hole 31 upsidedown, in order to avoid severe deformation of hose 7 17. This is made clear in FIG. 3a. FIG. 3b shows how,

means of a suitable screw, with a hose 17. At the upper of 'thebuoy thus makes it possible to apply the inventhrough corresponding longitudinal grooves in thepipe. The shaft bears pulleys 21. At the upper end of I pipe 11 there are similarpulleys 27, and lines 23 run over the pulleys. The latter pass out through the bottom plate 12 and flange 14, and are so arranged that by drawing them in, it is possible to displace ring 20 between two terminal positions, one of which is shown in FIG. 1, and the other in FIG. 2. To bottom plate 12 and ring 20, bears are fixed for

link arms

24, 25 respectively, running in an oblique radial direction outward and upward or downward, respectively. Each of the arms 25 has two parallel legs, between which,'corresponding arms 24 are fitted. At their outer ends, the arms are guidably fixed to standards 26. Together with the latter, the arms form a link mechanism, which in this case consists of six units. The latter are surrounded on all sides by a sheath 27 which is connected water-' tightly to bottom plate l2. Thus a floating body is formed, which, according to the selected example of execution, has a hexagonal shape when seen horizonby maneuvering lines 23, it is possible to expand the buoy 10, which is thus still upside-down. FIG. 3c illustrates the actual inverting process. In FIG. 3d the buoy is seen floating on the water mixture. The construction tion even to tankers or other containers which access is available only through relatively small introductory openings.

FIG. 4, on the contrary, shows a format execution of the invention according to which it is assumed that the installation was made in connection-with the construction of the ship. Buoy 10 is therefore not collapsible,

tally. At each of these corners there are staves 28' designed to protect the buoy thus formed.

To the outer, underside of the buoy, a cloth 29 is connected, which can consist of the same material as sheath 27, and which is tightly connected to flange 14.

and instead of a hose from this suction funnel, there is a pipe duct 32. At both ends of pipe 32 there are

angle ducts

33, 34 respectively. As in FIG. 1-3, an eye 18 is attached to the top of the buoy, with a wire 19 connected to said eye. In this case, only the wire passes through manhole 31 to a winch or some corresponding device 35 on the deck. As shown in the drawing, this arrangement makes it possible to keep the buoy, normally, in a storage place, marked in dotted lines. In this 'position, the buoy is inside a boxlike, protected chamber which can be closed by all walls except by one or two of the end walls, which are perpendicular to a plane in which the swinging movement takes place. In

have counterparts in the above-described figures have been given the same reference numbers as the latter. The difference with respect to FIGS. l-4 consists in the fact that the oil collection funnel is divided by a partition 38 likewise funnel-shaped, into a top section 39 and a bottom 40. The upper one of these is connected to outlet pipe 15, while the lower one, at the bottom, passes into a collection chamber 41, to which is connected the lower end of a pipe 42 whose upper end opens directly below the surface of the all-liquid mixture. The top edge of wall 38 lies at a somewhat lower level than the corresponding edge of bottom wall 29. The device which at first hand is considered for use with comparatively thin oil layers, has the advantage that the oil concentration in section 39 becomes higher than in section 40. The first named fraction is thus pumped off directly through pipe 15. The oil which is in section 40, in chamber 41 and in pipe 42, tends to rise up through pipe 42, and its corresponding movement is assisted by introduction of compressed air through a narrow pipe 42, which opens inside pipe 42.

After the oil collection is terminated, the ballast water is pumped out, and it has an oil content of no more than up to about 5 percent of the level obtained with the spraying. Pollution of the ocean water is thus correspondingly reduced. Evacuation of the ballast also means that the tank is completely filled with fresh air. This state of affairs in combination with the fact that the oil residues remaining on the tank sides will not give off any substantial amount of gases, means that the gas content drops to a completely safe level, on the order of percent of the lower limit of the explosive range. Water spraying of the tank walls can thus be carried out with no risk of explosion, and after this treatment is completed, the gas concentration is, of course, still lower.

The foregoing description also makes it clear how the method according to the invention is operated. It can be added, however, that according to a preferred form of execution of the invention, it is suitable to use the spray devices during the oil collection stage as well as, for subsequent rinsing of the tank walls. By suitable placement or utilization of these spray devices it is possible to accelerate the sucking out of the oil layer by the buoys. A single typical case can be represented by one or more buoys disposed at one short end of an elongated tank, while at the other short end the spray devices are actuated, so that the oil layer tends to flow towards the buoys. Last of all, it will be mentioned that the invention can vary within wide limits, both as the method and construction. The only essential thing is that water ballast be introduced into an emptied tank so that an oil layer floating on the top of the water is formed, which layer is removed with the aid of collecting devices in the form of buoys which in turn float on the oil-and-water mixture.

I claim:

1. A collapsible oil skimmer apparatus for collecting oil on the surface of a body of water comprising a longitudinal member with a first end and a second end comprising a central axis for said apparatus, a buoyant chamber of flexible material surrounding said longitudinal member at a first end thereof and foldable therearound whereby it is at reduced diameter in folded position, an oil collection chamber constructed and arranged around saidlongitudmal member at said second end and foldable therearound whereby it is of reduced diameter in folded position, oil inlet means substantially at the outer periphery of said collection chamber when said apparatus is in unfolded position, oil outlet means arranged within said collection chamber relatively closer axially to the second end of the longitudinal member than said oil inlet means when said apparatus is in unfolded position whereby collected oil may be withdrawn from said chamber, said apparatus being inoperative for skimming oil when in a folded position and operative for skimming oil when in an unfolded position.

2. The apparatus of claim 1 including pulley means and a pulley line associated therewith for remotely foldingv and unfolding said apparatus.

3. The apparatus of claim 1 including a connecting line attached thereto for inserting said apparatus into a tank.

4. The apparatus of claim 3 including a remote winch with said connecting line extending to said winch.

5. The apparatus of claim 1 wherein said oil collection chamber is funnel-shaped when said apparatus is in unfolded position and said oil outlet means is centrally located in said collection chamber when said apparatus is in unfolded position.

6. The apparatus of claim 5 including funnel-shaped partition means within said collection chamber.

7. The apparatus of claim 1 including oblique radial arms extending from said longitudinal member for unfolding said buoyant chamber.

m3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,722,690 Dated March 27, 1973 Inventor(s) Borje Stenstrom It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 14, "devices" should read -device Column 3', line 51, "bears" shou'ldread --bearings Signed and sealed this 29th day of January 1974.

(SEAL) Attest: v v

EDWARD M.FLETCHlER,JR. RENE D. TEG'lMEUfER' Attesting Officer Acting Co mmlssloner of Patents

Claims

1. A collapsible oil skimmer apparatus for collecting oil on the surface of a body of water comprising a longitudinal member with a first end and a second end comprising a central axis for said apparatus, a buoyant chamber of flexible material surrounding said longitudinal member at a first end thereof and foldable therearound whereby it is at reduced diameter in folded position, an oil collection chamber constructed and arranged around said longitudinal member at said second end and foldable therearound whereby it is of reduced diameter in folded position, oil inlet means substantially at the outer periphery of said collection chamber when said apparatus is in unfolded position, oil outlet means arranged within said collection chamber relatively closer axially to the second end of the longitudinal member than said oil inlet means when said apparatus is in unfolded position whereby collected oil may be withdrawn from said chamber, said apparatus being inoperative for skimming oil when in a folded position and operative for skimming oil when in an unfolded position.

2. The apparatus of claim 1 including pulley means and a pulley line associated therewith for remotely folding and unfolding said apparatus.