US3309167A - Anti-fouling apparatus - Google Patents

Description

March 14, 1967 s. GALLER 3,309,167

ANTI-FOULING APPARATUS Filed May 21, 1963 2 Sheets-Sheet 1 IELE'LL :3 (CASTOR 0| I.)

f|3 ENERGY SYSTEM ENERGY SYSTEM ENERGY SYSTEM x I l .3 C. 35 I C 34 INVENTOR SID N EY G A L L E R ATTORNEY March 14-, 1967 Filed May 21, 1963 S. GALLER ANTI-FOULING APPARATUS 2 Sheets-Sheet 2 FF: 6 n mnmmmmg 62 z 60 E: 000mm}? E1125: so

ENERGY soURoE CLOC K WATER TRANSDUCER TRANSDUCER PROGRAMMER TEMPERATURE TEMPERATURE HEATTNG sENsDR SENSOR ELEMENT INVENTOR WATER VELOCITY SIDNEY GALLER DETECTOR ATTORNEY United States Patent 3,309,167 ANTI-FOULIN G APPARATUS Sidney Galler, 6242 Woodcrest Ave., Baltimore, Md. 21209 Filed May 21, 1963, Ser. No. 282,184 1 Claim. (CI. 21-61) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to an apparatus to prevent fouling of marine equipment by marine biological organisms in the sea. More particularly the invention is directed to apparatus for combating barnacles and the like, which tend to attach to and/or deposit heavy encrustations of calcareous-like materials on underwater equipment.

Barnacles have a long and inglorious history in the marine industries. Their razor-sharp shells coat pilings and pier walls, forming a hazard to deck hands and dock hands and dock workers. The same is true of anchor chains, anchors, nets and other gear, which are submerged for days and weeks at a time. Most important, the hulls, screws, and rudders of ships eventually become too burdened and distorted to perform their function and must be cleaned.

The problem has become more serious in modern times. A host of new precision instruments have been developed for the science of oceanography to measure sound velocity, depth, temperature, salinity, and similar properties in the sea. Other instruments have been developed for navigation and purposes of national defense. Not only must many of these instruments be built to survive long immersions in the sea, but their surfaces must remain reasonably clean to permit them to function properly.

It has become the practice in the art to paint or coat such objects, as are mentioned by way of example above, in order to prevent fouling. Some of these coatings have proved successful in preventing this condition for short periods, while Others merely slow the process. Such coatings are often dislodged by accident, leaving the equipment with no protection. An early attempt to solve the problems involved releasing oil through holes in a ships keel. This method has obvious disadvantages.

An object of the present invention is, therefore, to provide apparatus to prevent fouling of underwater equipment which involves heating external surfaces exposed to marine organisms.

These and other objectsor attendant advantages of the present invention will be best understood with reference to the following specification, taken in conjunction with the accompanying drawings wherein:

FIG. 1 shows the side view of a submarine partly cut away with antifouling structure incorporated in its sonar dome;

FIG. 2 shows the cut away side view of a low frequency sound transducer incorporating antifouling structure;

FIG. 3 shows a hydrofoil craft partly cut away with antifouling structure associated with its hydrofoils;

FIG. 4 shows a heating element for use in the structures of FIGS. 1-3 using a liquid heat carrier;

FIG. 5 shows a first electrical type of heating element for use in the structures of FIGS. 1-3;

FIG. 6 shows a second electrical type of heating element for use in the structures of FIGS. 1-3;

FIG. 7 shows a block diagram of the heating element and energy system of FIGS. 13; and FIG. 8 shows a cut away view of one embodiment of the velocity detector in FIG. 7.

- animals involved in the fouling.

In order to appreciate the present invention, it is necessary to know a little about the life cycle of barnacles. A great deal of research has been done on these organisms and reported in various publications. One example is the publication edited by Dixy Lee Ray entitled, Marine Boring and Fouling Organisms, published in 1959 by the University of Washington Press, Seattle, Wash.

The development of a" barnacle proceeds in several stages beginning with an ovum or egg. After hatching from the egg the resulting organism proceeds through a series of naupliar stages, in which it exists as a free moving planktonic life form. This generally takes between seven and thirteen days. At least two additional stages are of interest, the cyprid stage and the sessile stage.

When the barnacle reaches the cyprid stage it tends to settle out of its exclusively liquid environment onto solid objects. The barnacle may remain in this stage from one to fourteen days, but if it remains more than three days its development generally ceases at this stage.

If the barnacle successfully settles out and metamorphoses to the sessile or attached stage, the problems associated with this organism begin. The organism begins to deposit its characteristic calcium shell material. Killing the organism will arrest, but not eliminate this deposition. Further, it has been noted that new barnacles settle more readily on surfaces that are already occupied by others of their breed. In the sessile stage a barnacle is very adaptable and may survive for years.

It can be seen from the discussion above that at any particular time underwater equipment should be protected from organisms in the cyprid stage. Earlier stages are no problem. Organisms in the sessile stage are more diificult to kill and have done irreversible damage.

It has been discovered that heat can be used to prevent the attachment of the cyprid stage. In geographic loca tions where settlement rates are normally high, a blockage often occurs during a series of unusually warm days. Tests have shown that even the most adaptable species in the more favorable sessile stage cannot endure a temperature over 45 C. about F. for more than a minute without damaging the organism.

While barnacles are perhaps the best known of the fouling organisms it is not always the most important. There are more than 2000 species of both plants and In certain instances, a two day accumulation of algae on the pontoons of an air plane has been sufficient to prevent the aircraft from reaching take-off speed. The settlement of all of these organisms can be discouraged by the periodic application of a suificiently high temperature, e.g. 150 F., at the surface under attack. In contrast, protective coatings are usually designed to discourage only specific species of organisms.

FIG. 1 shows a structure in which the above temperature characteristic can be used to protect underwater sound equipment. submarine 10 with a sound transducer 11 mounted on the outer surface of the submarine. To prevent turbulence, a dome 12 is placed over the transducer and a sound coupling medium 13 such as castor oil added to fill the space between the transducer and the dome. Heating elements 14 are placed in the dome to quickly elevate the temperature. Energy is supplied to the heating elements from an energy system 13 Within the submarine.

Other ways of producing the desired heating might be to place the heating elements in the castor oil or to heat the oil in the submarine and circulate it between the dome and the transducer. However, owing to the efiicient heat sink presented by the sea, it is preferred to apply the heat rapidly as near the external surface as The equipment is carried aboard a possible. The settlement of organisms on the external surface provides a degree of insulation, so that the system is actually more efiicient in its working environment. The structure of the heating elements per se will be discussed presently.

FIG. 2 shows another form which the present invention may take. The structure shown is an underwater sound transducer of the type currently used in low frequency sonar systems. It is sufficient for present purposes to state that this transducer consists of a hollow cubical housing 20 with an internal motor 21 which engages the internal surfaces of housing walls only over a small percentage of four nonradiating walls. The radiation characteristics of this transducer depends in part on the mass of the housing and its resistance to reciprocal motion in the water. A more complete description of one form of this transducer may be found in patent application Ser. No. 611,798, filed Sept. 24, 1956 by John Chervenak, now abandoned.

The accumulation of barnacles on this type of transducer presents a serious problem. The extra mass causes a shift in the center frequency of their operating characteristic. Roughening of the surfaces lowers the efficiency of the device and alters the directivity pattern. Such an accumulation may be prevented by means of a heating element 22 attached to inner surfaces of the walls, which again are made and operated in a manner to be described presently.

The heating element is connected to an external energy system which may be the same system supplying the motor element 21. The two elements can easily operate on a time sharing basis, since the timing of the former is not critical. To prevent barnacle accumulations, heating elements 34 and 35 are placed in all parts of the hydrofoil which are submerged when the craft is at rest. The heating elements are connected to an energy source Within the boat and operated in a manner to be described presently.

FIG. 4 shows one form the heating elements may take. In this case heat is carried by a heat transfer liquid flowing through tubing 40 embedded in the wall 41 or other member to be heated. The tubing is preferably made from a material having good heat conducting properties such as copper or aluminum, although other materials may be used. If used in the structure of FIG. 1, the tubing and heat transfer liquid should have the same composition or sound propagation characteristics as the dome and castor oil.

FIG. 5 shows a second form of heating element which may be employed with structures having walls of electrical insulating materials. A length of wire 50 consisting of electrically conducting material is imbedded in the wall 51. 'By passing an electric current through the wire ohmic heating is induced which is transferred to the wall. In thermoplastic materials the temperature of the wire must remain below the softening point of the material. The use of ribbon shaped conductors will improve heat transfer in such instances.

FIG. 6 shows an electrical heating element primarily suitable for metal structures. A radiant heating conductor 69 is mounted in close spaced relationship to the metal wall 61 by means of refractory ceramic insulators 62. The conductor is a conventional tungsten alloy which maintains its strength at red heat. If desired, a polished metal reflector (not shown) may be mounted parallel to the wall with heating element between and spaced from the two former elements. The surface of the wall may also be roughened and darkened to improve its heat absorbing qualities.

FIG. 7 shows an energy system such as shown in FIGS. l-3 in block diagram form. While this system can conceivably consist merely of a manually controlled energy source 60, a few simple refinements make the device much easier to use. For example, a temperature sensor attached to the transducer can be used to control the output of the energy source to maintain a constant temperature at the heated surface, thereby saving fuel. Also, a clock programmer can be used to automatically energize the system at appropriate intervals.

Two additional devices can also be employed to conserve fuel and heater life. A water temperature sensor may be connected to the programmer to disable it when the seawater temperature is too high for settlement and metamorphoses of cyprids. Also a water velocity detector may be employed to disable the clock programmer when a water current is passing over the protected surface and organisms are unable to settle on it.

The actual structure of various elements shown diagrammatically in FIG. 7 is not a critical feature of the invention. The temperature sensors may be the same type of thermostat and aquastat used in home heating systems or ovens. The clock programmer may be the same type as found in completely automatic home ovens. The energy source for the heating elements of FIGS. 5 and 6 will be a battery or generator and the various control elements will open or close high current relays to the heating element. A system using the heating elements of FIG. 4 may be similar with electrically controlled valves instead of high current relays, similar to the valves found in automatic clothes washers and dishwashers. The FIG. 4 system obviously can use oil or gas burners as an energy source.

FIG. 8 shows a convenient form of water velocity detector for use with the present invention. Briefly, the detector employs a mercury switch attached to the end of a length of flexible cable 81. The cable and switch are composed of materials having suflicient density to provide a negative buoyancy in seawater. With the upper end of the cable attached to the structure containing the heating elements, clock programmer, etc., the unit hangs vertically in the sea as shown. Attachment generally will involve a conventional watertight seal through a non-radiating wall.

The switch consists of a housing 86, at least the inner surface 82 of which is formed of conducting material, and a drop of conducting material such as mercury. The housing is a solid of revolution having its axis normally vertical. The bottom of the housing is slightly concave to gravitationally center the drop in the vertical position. Two conductors 84 and 85 enter the housing from the cable. First conductor 84 is electrically connected to the inner surface of the housing, and the other, 85, extends along the vertical axis of the housing to the upper surface of the conductive drop 83. When displaced by a water current the attitude of the housing shifts, as does the drop, thereby opening the circuit which energizes the programmer.

The ideal method of operating the device will vary according to its geographical location and the season of the year. Biological data may be compiled in suitable book form for use by a human operator. However, data so far available indicates that an automatic system operating a few minutes every other day might provide sufficient protection. For greater safety, operating periods of half an hour each day are relatively easy to supply.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It would be impossible to disclose fully all of the marine equipment such as seaplanes, buoys, mines, nets, etc., in which the present apparatus may be installed. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

What is claimed is:

An apparatus for preventing the settlement of organisms in sea water onto the exposed surface of the walls of submerged objects, comprising:

a heating element mounted internally of said sub- 5 merged object in heat transfer relationship to said walls,

an electrical source for energizing said heating element coupled thereto,

a water temperature sensing means operative to control said electrical source in response to temperature changes in the sea water, and

deactivating means external to said object for disabling said electrical source through activation of said deactivating means in response to the flow of sea Water relative to said walls of said object and said deactivation means.

References Cited by the Examiner UNITED STATES PATENTS 58,742 10/'1-86 6 Weems l14222 6 632,919 9/ 18-99 Farley l44222 660,646 10/ 1900 'Mason 144-222 900,929 1-0/1908 Howe 144222 X 1,319,550 10/1'919 Wilson 114-222 FOREIGN PATENTS 890,265 2/ 1962 Great Britain.

I. ZATARGA, Assistant Examiner.

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