Method and Apparatus for.Oil Skimming Background of the Invention
1. Field of the Invention
This invention relates to a method and apparatus for remov¬ ing oil from a water surface and particularly to an improved method and apparatus for effecting the continuous removal and recovery of large quantities of oil from extended area water surfaces.
2. General Background and Prior Art.
Pollution of natural waterways and defining marginal land masses, such as harbors, rivers, lakes and defining shore lines and even open seas by oil floating on the water surface is of primary environmental significance. Recent years have witnessed ever increasing quantities of oil spillage from tanker or barge damage, drilling accidents, tank cleaning or other sources with attendant environmental damage to both land and water. Such has been accompanied by an ever increasing public concern both with the problem and with the apparent inability of current technology to ameliorate, much less to solve, the problem of large volume oil spillage.
Although many expedients have been proposed for effecting the removal and collection of oil floating on water prior to adjacent land mass contamination, such as dispersion, skimming, absorbtion, burning and the like, such efforts have been gener¬ ally ineffective, at least insofar as oil spills of any large quantity and consequent areal size are concerned or where water surface turbulence of anything over minimal character is in¬ volved.
Prior attempts at the design of skimmers, crafts which move throughout an oil slick and collect the oil therefrom, have pro¬ ved to have very limited effectiveness. An inherent problem with these devices is that they all present a rigid structure, usually in the form of a belt assembly with a rigid support, to the on¬ coming oil. When such a moving rigid structure is presented to an oil slick a "headwave" is formed in the oil near the structure. At very low relative velocities of the headwave becomes hydro- dynamically unstable. Studies have shown that at relative speeds
in excess of approximately 1.25 knots the headwave breaks up, a entrained droplets of oil are swept past the oncoming structure
Studies have also shown that this phenomenon occurs even the structure is provided with a continuously moving belt of o collecting material. Thus, a serious limitation of "prior skimm designs has been that they can only operate at speeds of t order of 1 knot if they are to have any significant collecti efficiency at all.
A further complication that has materially militated again prompt resolution of oil spill problems is the totally unpredic able nature of the causes thereof and the widespread geograph areas within which which such spills may occur. As a practic matter, the necessary time that passes between the initiation- an oil spill and the physical availablity of any collection mea at the locus thereof usually permits the spread of the spill oil over an area that far exceeds the ability of any present d techniques for collecting or otherwise handling the same. As corollary to the above, all problems attendant oil removal a markedly accelerated as the gallonage of the spill increase both with respect to the geograpic ' areas involved and wi respect to disposition of the collected oil itself.
Prior patents of possible interest are cited below:
PRIOR ART PATENTS
U.S. Patent No. Patentee(s) Issue Date
3,643,804 D. E. Sharpton 2/22/72
3,668,118 H. M. Rhodes 6/6/72
3,670,896 F. E. Hale, Jr. 6/20/72
3,744,257 W. F. Spanner 7/10/73
3,968,041 E. A. De Voss 7/6/76
4,061,569 J.A. Bennett, ETAL 12/6/77
General Discussion of the Invention
This invention may be briefly described as an improved me¬ thod and apparatus for removing oil from a water surface and which, in its preferred embodiment, includes a modularly asse b- lable, self-propellable catamaran type vessel defining a longi¬ tudinal oil collection channel of inverted U-shape. Large surface areas of oil collecting material for example, polypropylene, in the form of elongate endless belts or ropes are freely and loosely supported on the water surface to move therewith and are abvanced through the inverted U-shaped channel countercurrent to the direction of vessel advance and preferrably at a zero differential velocity relative to the water surface to maximixe oil collection. The preferred oil collecting material is polypro¬ pylene, formed in thin strips and radially disposed about a core belt or rope. Although oil collecting material in continuous flat wide belt or sheet form is possible and contemplated in the present invention, a series of independent rope belts is greatly preferred because it allows further freedom of movement in the lateral direction between the individual belts due to the presence of debris or other obstacles.
Associated therewith and disposed upon a deck structure bridging the catamaran hulls are means for advancing the oil collecting material concurrently with the movement of the catama¬ ran vessel through the water and for removing the collected oil prior to the reintroduction of the material into the oil collec¬ tion channel. In its narrower aspects, the subject invention includes the conjoint usage of the catamaran hulls or sections thereof to temporarily store the oil removed from the water sur¬ faces.
Among other advantages of the subject invention is the pro¬ vision of a self-propellable oil collection vessel that serves to maximize the collection of oil and the separation efficiency of the oil collecting material employed with respect to the quantity of oil exposed to collection and the time of explosable contact therebetween. Further advantages accrue in oil collection and efficiency when the multiple strip poypropylene ropes used.
Still further advantages include provision of a collect method and apparatus that is effectively operative independent sea conditions both with respect to surface turbulence and to presence of floating debirs thereon. Still other advanta include the provision of increased oil storage facilities with detrimental diminution of oil collection efficiency and provision of a readilly assemblable modular structure that easily transportable for rapid assembly at the locus of intended use thereof^
An object of this invention is the provision of impro method and apparatus for effecting the collection of oil from surface of water in calm waters as well as in relativ turbulent waters when needed and at relattively high speeds.
Other objects and advantages of the subject invention w become apparent from the following specification and from appended drawings which illustrate, in accord with the mandate the patent statutes, a certain presently preferred embodiment oil collection apparatus embodying the principles of this inv tion.
Brief Description of Drawings
For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals and wherein:
Figure 1 is a schematic plan view of an improved oil collec¬ tion apparatus incorporating the principles of this invention.
Figure 2 is a schematic side elevation of the apparatus illustrated in Figure 1; and
Figure 3 is a vertical section as taken on the line 3-3 of Figure 1.
Detailed Description of the Preferred Embodiment
Referring to the drawings there is provided a catamaran t vessel formed of a pair of elongate spaced hull sectio.ns 10, spanned by a deck section 14 suitably constituted, at least part, of metal grating or the like and supported by a plural of cross beams removably securable to the hull sections 10, The transversely spaced hull sections 10 and 12 and the overly deck assembly generally define an inverted generally U-shaped collection channel 16 running the full length of the vessel w the surface of the water disposed intermediate the hull sectio The hull section 10, 12 and overlying decking may be pref ricated in easily assemblable modular sections of, for examp readily transportable 20 foot lengths, and detachably joined at 18 to form an assembled structure. Further, the hull secti 10, 12 are of multi-co partmented construction. Some of th compartments may be filled with buoyant foam material wh others may be utilized for storage of collected oil.
As will hereinafter become apparent, and is clear from F ure 2, the oil collecting material herein employed is slack loose when the vessel is at rest and thus floats loosely upon water surface and allows substantial "give" or movement of t material under water action; hence particular depth of catamar hull section immersion is not a critical or determinati operative parameter and additionally this looseness allows oper tion of the vessel at higher speeds as discussed more ful below.
Mounted in the stern portion of each of the catamaran hu sections 10, 12 in an inboard motor 20 controllable both as speed and helm response from an operating console 22 mounted the deck section 14. Although having the vessel being sel propellable is preferred, it is of course possible to utili some of the basic principles of the present invention in a tow type or other type movable vessel. Peripherally disposed abo the deck section 14 is a guard rail assembly 24.
The oil collecting material employed in the practice of the herein described invention may be any of a number of types of materials. For example, sponge may be used, in a sheet or other continuous belt configuration, for collection by absorbtion. However, the material preferred for use in the present invention is polypropylene, formed into the structure disclosed in U.S. Patent No. 3,668,118. Such structure is essentially comprised of an elongate core strand having a multiplicity of thin guage narrow polypropylene strips extending generally radially there¬ from and constituting a relatively loose mass of individually discrete strands or strips that compositely provide a markedly extensive or expanded surface area for the oleophilic attraction and adherence of oil. As is apparent from the disclosure of such patent, the composite structure is both easy to handle and effective in removing the olepohilically adherent- oil from the oleophilic material prior to its reexposure to oil . Such material will hereinafter be termed an "elongate oleophilic rope element" or "elongate oleophlic rope material."
Mounted on the fore portions of the deck section 14 are a pair of oleophlic rope element driving and oil separation assem¬ blies, generally designated 30 and 32 respectively. As best shown in Figure 2, each of these assemblies includes a pair of compres- sively engaged drive rollers 34, 36, adapted to advance an assem¬ blage of a plurality of elongate oleophilic rope elements, for example, three endless belt type oil ropes 38a, 38b, and 38c in the direction indicated by the directional arrows 40. Associated therewith are a plurality of guide rollers 44 and 46 to direct the path of travel of the elongate oleophlic rope elements from the drive rollers 34, 36 downwardly into loose, floating disposi¬ tion on the water surface intermediate the catamaran hull sections 10 and 12 adjacent to the bow of the vessel. As can be seen in Figure 2, the lowermost bow guide roller 46 is located substantially above the water line "W.L." (for example three feet above in an exemplary vessel of forty feet in length) with the ropes having several extra feet of slack which allows the slack
oil collecting material 38 to contact and ride onto the init contacted water surface freely or loosely with substantial " permitting it (note 38') to be easily moved longitudinal vertically in response to wave or other water action, as we laterally. Additionally preferably no further guide roll other longitudinal or vertical movement restriction mean provided along the length of the oil collection material 38 it is in the water or close thereto. The rope elements 38 float freely on the wate surface without being taut or ri presented or under any substantial tension or restraint ad to the water surface contact and its contemplated movement.
Suitable spacing means, such as vertically disposed ba mounted at each end to a housing 54, are desirably includ maintain the elongate oleophilic rope elements,* for example 38b and 38c, in a desired laterally spaced relation .during travel through the drive asemblies 30 and 32.
Mounted on the rear of the deck section 14 and prefe well above the water level "W.L." is a guide roll assemb adapted to elevate the oil saturated oleophilic rope ele from engagement with the water surface and to direct them an elongate catch pan 52 on which they are supported during advance as effected by the drive rollers 34, 36. Suitable such as radially extending plates or flanges are included i guide rolls assembly 50 to maintain the oil rope belt laterally spaced relation. The catch pan 52 drains towar driving and separation assemblies 30, 32. Each of the oleopo rope element driving and oil separation assemblies 30 includes a housing 54 and an oil sump from which collected o transferred via schematically illustrated conduit 58 and pu are also utilized to transfer collected oil from the compart 62 to other storage vessels.
In using the described unit, the separated modular co ents thereof are adapted to be shipped via air or other means of transportation to the locus of their intended us there assembled. By way of example, the main modular compo thereof may comprise the illustrated two catamaran hull
sections, the deck gratings, the oleophilic rope clement driving and oil sepoaration assemblies, the control console assemblies and the like, or may include further sub-assemblies thereof. At" or near the locus of use, the readily transportable modules are readily assembled to form the structure depicted in the drawings. The assembled structure is then towed to or drive under its own power to the locus of spillage.
In operation, the illustrated vessel is adapted to be ad¬ vanced through the oil spill at a predetermined speed. For the purposes of explanation, such rate of advance may be considered as the water moving from the bow to the stern at a rate of Vw knots. Concurrently therewith, the oleophilic rope element driv¬ ing and oil separation assemblies 30 and 32 are adjusted to ef¬ fect a displacement of those portions of the endless belt elong- gate oleophilic rope elements floating upon the water and dis¬ posed within the oil collection channel intermediate the cata¬ maran hull sections 10 and 12 in the bow to stern direction at a predetermined speed, for example, at a rate of V knots. As best shown in Figure 1, each of the oleophilic rope element driving and oil separation assemblies serves a plurality of separate and discrete endless belt type elongate oleophlic rope elements and whose composite transverse extend substantially fills the trans¬ verse space between the hull sections 10 and 12. As will now be apparent, if the speed of displacement V of the elongate oleophilic rope elements is substantially equal to or slightly in excess of that of V of the elongate oleophilic rope elements is substantially equal to or slightly in excess of that of V , optimum conditions will be established with respect to dwell time for oleophlic pick up of the oil on the strands of the oleophlic rope material. Thus, if the transverse extent of the channel formed between the hull sections is substantially filled with the floating oleophilic mop material and the differential speed relation between such material and the water surface is main¬ tained at a minimal or zero value as described above, essentially optimum conditions, effectively, independent of water surface condition or the presence of' floating debris, can be established and maintained for enhanced oil pick up on a quantitative basis. As is also now apparent, each set of the elongate oleophilic
rope elements, for example, 3aa, 38b, 28c, will sclective- ely and preferentially entrain oil from the water surface an they pass upwardly and over the guide roll assembly 50 effe vely separate appreciable quantities of the oil from the w surface. The guide roll assembly 50 directs the elongage o philic rope elements 38 on to the surface of the catch pan 5 support the same as it is advanced into the bite of the pressively engaged drive rollers 34 and 36. The drive roller and 36, which preferably have a surface of elastically deform material, serve both to advance the endless belts of elon oleophilic rope material in the manner described and to pressively squeeze or otherwise displace most of the entra oil from the surfaces of the elongate oleophilic rope materia it advances therepast. Such separated oil is collected in sumps from which it is removed and stored in the tank section of the catamaran hull sections 10 and 12. As will no apparent, the depth of immersion of the catamaran hull sect 10 and 12 is not critical since all collection activity t place on the water surface within the channel marginally def by such hull sections. The loose floatation of the oil collec materials, such as the elongate oleophilic rope elements 38, only maintains the same contact with the floating oil but renders the unit effectively impervious to floating debris or in the water, and within limits, to the degree of turbulenc the water surface since the free floating oleophilic mate will travel over and around any debris and will generally con to the water surface contour.
The permitted control of the differentiated velocity bet the floating elongate oleophilic rope elements and the ve velocity permits high efficiency utilization of the oleoph capabilities of the rope elements and consequent high volume high efficiency oil separation from the water surface in a mobility vehicle under widely varying conditions of operation
Exemplary dimensions for a vessel as illustrated and actually buit, tested and successfully used are a forty (12.2m) aluminum catamaran vessel for inland waters use. Such
a vessel can be disassembled and the total vessel stored in two eight-foot-by-eight-foot-by-twenty-foot standard containers. The vessel was powered by two diesel engine driven outdrives and was designed for recovery rates of up to one hundred and seventy-five gp (662 1/m) .
Each hull had its own plant and oil recovery system and was capable of operating independently of each other. The vessel had an on-board storage capability of two thousand gallons (7,570 1) and its own discharge pumps for unloading purposes. Further specfications and exemplary details are outlined below:
-DIMENSION SPECIFICATIONS-
LOA 39'- 8" ( 12 .1 m)
Beam 13' - 2" ( 4.01 m)
Draft (empty) 1' - 0" ( .305m)
Endurance Time 16 hours
Radius Operation 125 N.M. (231 km)
Engines ( 2) GM 3-53 N
Fuel 200 gal. (750L)
Oil Recovery Rate 175 gpm (662 1/m) -
-OIL RECOVERY SYSTEM-
(2) "Oil Mop" Mark 11-9 recovery systems
(6) Continuous loop "Oil Mop" 10" (254 mm) ropes 35' (10.7m) long ea.
(2) 135 GPM (511 1/m) independent sump/discharge pumps
(6) Independent oil tanks (2000 gal. [7,570.1] total)
(2) Manifolds for -fill and discharge
(6) Manholes (one into each tank).
A vessel at least generally identical to the foregoing was successfully tested for effective oil recovery at speeds up to five kts.
The foregoing details and examples are merely exemplary, and subject to great variation within the scope of the present invention. Thus the vessel land its oil collecting materials can be of various sizes and configurations from for example a single hull with the oil collecting materials hung off its side to the preferred multi-hull configurations with centrally defined chan¬ nels.
Thus, while the fundamental novel features of -invention been shown and described, it should be undrstood that var substitutions, modifications and variations may be made wit departing from the spirit or scope of the invention. Accordin all such modifications and variations are included in the sop the invention as defined by the following claims.