US3071531A

US3071531A - Cathodic protection system for submerged installations

Info

Publication number: US3071531A
Application number: US791917A
Authority: US
Inventors: Jr Harry W Hosford
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-02-09
Filing date: 1959-02-09
Publication date: 1963-01-01
Anticipated expiration: 1980-01-01

Description

Jan. 1, 1963 H. w. HQSFORD, JR 3,071,531

CATHODIC PROTECTION SYSTEM FOR SUBMERGED INSTALLATIONS Filed Feb. 9, 1959 2 Sheets-Shet 1 INVENTOR' HARRY W. HOSFORD JR.

f DWI/41% ATTORNEYS Jan. 1, 1963 H. w. HOSFORD, JR 3,071,531

CATHODIC PROTECTION SYSTEM FOR SUBMERGED INSTALLATIONS Filed Feb. 9, 1959 2 Sheets-Sheet 2 Q INVENTOR.

' HARRY w. HOSFORD JR.

AT TORNEYS United States Patent Ofifice Patented Jan. 1, 1963 35371531 CATHGIDEC PRQTEYCTHQN YSTEM FER SUEMERGED ENSTALLATIONS Harry W. He eford, in, 2565 Stratford Road, Cleveland Heights, (this Filed Feb. 9, 1959, Ser- No. 791,917 9 Qiaims. (Cl. 204-196) This invention relates as indicated to the cathodic protection of submerged installations and more particularly to the protection of steel piling, piers, bulkheads, drilling platforms and the like.

The problem of corrosion of metal installations such as piers, especially in salt water, is, of course, an extremely serious one and many efforts have been made to overcome or at least mitigate this problem, with two forms of protection now being quite generally employed. The first consists of any of the various well-known protective coatings, none of which, however, is of any great durability, while the second is cathodic protection utilizing electrically charged anodes spaced a proper distance from the piling or other metallic parts to be protected. It is interesting to note that it is usually expected that without the provision of an effective cathodic protection system as much as by weight of the submerged pier, for example, will corrode away in the first year. Many different forms of installations have been tested with only indifferent results from a practical viewpoint, particularly with regard to installation cost and durability. Thus, anodes have been suspended in the water alongside and beneath piers and docks by means of the insulated cables utilized to conduct the electric current thereto. It has been found, however, that such installations are frequently damaged by debris floating in the water, and also, that the gases such as hydrogen, oxygen, chlorine and compounds derived therefrom rising from the submerged anodes tend to attack the insulation of the supporting conductor, thus exposing the conductor proper to attack and preventing transmission of the electric current to the anode which is thereupon rendered useless for its intended purpose.

Still another method employed has been to place a string of anodes on the bottom adjacent the installation to be protected, the anodes being connected together by the insulated conductor so that but a single conductor line leads upwardly from the string to the current source. Such single conductor has, however, normally still extended above at least one or more of the anodes and has thus still been subjected to chemical attack, with the additional disadvantage that when it eventually fails, the entire series of thus-connected anodes is rendered inoperative. Furthermore, the anodes quickly silt over and the deleterious gases aforesaid tend to be trapped and to accumulate about such anodes, reducing their protective effectiveness and also causing the anodes themselves to be attacked much more rapidly than would otherwise be the case and so reducing the life of the anodes themselves.

In view of the foregoing, it is a principal object of my invention to provide a system of cathodic protection for submerged steel installations such as piers and the like which will be both sturdy in use and reasonably invulnerable to damage from floating debris, and also in which electrical connections to the anodes are so disposed that they are not subjected to deleterious chemical attack.

It is a further object of my invention to supply 21 cathodic protection system for submerged steel installations which can be quickly and easily installed and can be readily serviced when the occasion demands.

Other objects of the invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

FIG. 1 is a diagrammatic top plan view of a maritime structure equipped with a cathodic protection system in accordance with my invention;

FIG. 2 is a vertical section taken on line 2-2 on FIG. 1;

FIG. 3 is an enlarged elevation of one of the electrodes and its supporting means with the electrode being shown on a larger scale than the supporting means and having parts broken away for clarity of illustration.

FIGS. 4 and 5 are detailed sectional views of alternative electrode supporting means;

FIG. 6 is a fragmentary detail sectional view illustrating means of suspending one type of electrode.

Referring now to such drawing and more particularly to FIGS. 1 and 2 thereof, there is shown a common platform 1 usually made of reinforced concrete resting on steel pilings 2 submerged in water. These steel pilings 2 are embedded in the bottom 8 and extend well below the mean low water level W. interspersed between the pilings 2 are a series of suspended anodes 3. These anodes are suspended from the platform or deck of the pier 1, for example, by means of strong impervious cords or cables 4 which may desirably be of a synthetic plastic material such as a resin obtained from the copoiymerization of vinylidene chloride and vinylchloride and known in the trade as Saran, such material having a very long life under conditions to which it is subjected in use and being quite strong and resilient so it is very seldom broken or damaged by floating debris. The insulated electrical conductors 5 leading from the current source pass downwardly through a vertically extending galvanized steel pipe 6, the lower end of which may desirably be at a level approximating that of the lower ends of the anodes 3 which are preferably suspended so as to remain entirely submerged at low water level. The individual insulated electrical conductors coming from the lower end of pipe 5 are connected to the lower ends of the suspended anodes 3 making a common insulated connection therewith.

It will readily be seen from the foregoing that the conductors which extend at a level beneath the anodes rather than extending upwardly above the latter are so located as to avoid the deleterious action of the gases and chemicals which arise from the submerged anodes. Furthermore, the vertically extending metal pipe 6 through which the conductors pass is itself protected from corrosion through the action of the cathodic protection system in the same manner as other metal parts of the structure.

The conducor 5 may comprise an electrically conductive cable such as copper covered with insulating material such as a high molecular weight polyethylene, and the joints, as those shown at 7, may be of any standard wrapped and moulded construction.

The conduit or pipe 6 extends upwardly to a housing 8 which contains the standard rectifier and relay units supplying a source of direct current. From this housing there extends downwardly another conduit or pipe 9 through which pass the insulated conductors 10 of the cathode or negative portion of the system. These conductors are connected to the steel pilings and other portions of the pier or submerged installation, ordinarily at points above water level.

In suspending the anode by the Saran rope or cable the use of metal eye-bolts or other similar hardware has been found unsuitable since they themselves tend to be subjected to undesirable chemical attack. As shown in FIG. 3, a sectional graphite anode has been used wherein the sections of the anode are provided with central bores for insertion of the cable or conductor. However, anodes of carbon, high-silicon cast iron or other suitable material may also be used. The upper section 11 of the anode 3 has been hollowed out as at 12 and a knot 13 has been tied in the Saran rope to secure the upper section of the anode thereon. The lower section of the anode is attached thereto by means of a threaded connection member 14. A suitable crimp connection is provided at 15 for the vertically extending conductor cable to secure it to the anode in electrical contact therewith and a resin base cement is injected at 16 to provide a firm bond and seal both the joints of the conductor cable and the Saran rope against entry of moisture.

In connecting the Saran rope to the reinforced concrete deck of the pier, a cast iron box 17 is provided which seats on a beveled recessed portion of opening 18. To this box is attached an eye-bolt 19 from which is suspended the Saran rope 4.

FIG. 4 illustrates a modified form of support for the Saran rope wherein a galvanized steel plate 29 is employed seating in a recessed portion in the opening 18 in the deck.

FIG. illustrates a lining or reinforcing member 2 1 which can be inserted in the opening in the reinforced concrete deck to provide a more secure seat for such plate 20.

FIG. 6 illustrates a modified form of connection between the anode and the Saran rope. The anode employed in this modification is an anode having a blind section i.e., a section without a complete central bore. The end of the section is provided with a short central passage 22 and a lateral opening 23 which is somewhat enlarged. In securing the anode shown in FIG. 6, the rope 4 is merely drawn through the passage. A knot 13 is tied in the end thereof and is drawn through the lateral opening 23 until it is caught by the shoulder of the smaller passage 22. These openings in the anodes can readily be formed by drilling. I have found it important that the suspension cables enter the upper end of the anode centrally and axially rather than to be offset in any way as otherwise the anodes tend to revolve or twist in use with consequent damage to the system. It will be noted that in the openings provided in the anode in FIG. 6, a suitable sealant can also be inserted in the same manner as shown at 16 in FIG. 3, if desired.

It will be readily appreciated from the foregoing that the equipment is itself of minimum cost and is also very simple to install. As will be noted from the showing of FIGS. 3, 4 and S, the connection between the rope and the floor or deck of the pier permits easy and ready removal of the anodes from the Water through the openings in the deck for inspection or replacement as desired.

While the present invention is particularly useful in protecting docks or piers having steel pilings it will be understood that this use of the invention is by way of illustration only and that the invention may be employed to advantage for the protection of any metal member submerged in a body of liquid or moist earth wherein the deleterious effects of the gases from the anode will affect the conductors therefor.

Other modes of applying the principles of the invention maybe employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be em ployed.

I therefore particularly point out and distinctly claim as my invention:

1. In a cathodic protection system for a maritime installation having a platform supported on submerged corrodible metal piling, a series of vertically extending anodes suspended from the platform and spaced from the piling, said anodes being submerged between the low water line and the bottom beneath the installation, said anodes each having a conductor connecting the anodes to a source of 4 direct current, said conductors extending generally horizontally beneath the level of the anodes and being connected thereto solely through the lowermost points there- 2. A cathodic protection system for maritime installations having a platform supported on submerged corrodible metal piling, a series of vertically extending anodes arranged in a submerged position between the low water line and the bottom beneath the installation, said anodes each having a conductor connecting the anodes to a source of direct current, said conductors running generally parallel to the bottom and extending beneath the anodes and being connected thereto solely through the lowermost points thereof.

3. The cathodic protection system set forth in claim 2, wherein the anodes are supported by inert plastic ropes suspended from the installation platform.

4. The cathodic protection system set forth in claim 3, wherein the rope is made of a resin formed by the copolymerization of vinylidene chloride and vinyl chloride.

5. The cathodic protection system set forth in claim 3, wherein the anodes are fixed centrally and axially to the suspended ropes.

6. The cathodic protection system set forth in claim 2, wherein the conductors are received in a metal conduit for transmission to the current source, said conduit extending beneath the platform to approximately the same level as the lowermost point of the anodes so that said conductors will be enclosed therein above the level of said anodes.

7. A cathodic protection system for a maritime installation having a platform supported on submerged corrodible metal piling, anodes suspended from the platform in a submerged position and spaced from the metal piling, conductors connecting the anodes to the positive side of a direct current source, said anodes being suspended by inert plastic ropes connected to metal plates seated in recessed openings in the platform whereby the anodes may readily be removed through such openings from their submerged position for inspection or replacement as desired, said conductors being solely connected at the lower ends of said anodes and disposed substantially horizontal in the region of the anodes.

8. A cathodic protection device for a maritime structure comprising a platform, an opening in said platform, a. recessed shoulder in said opening, a support element rest ing on said shoulder, an inert plastic cable suspended from said support element and extending to the upper end of an electrode, an insulated conductor connected solely to and leading laterally from the lower end of the electrode to a vertically extending conduit and extending horizontal in the region of the electrode, said conductor connecting said electrode to a source of direct current.

9. A cathodic protection system for a maritime installation having a platform supported on submerged corrodible metal piling, a plurality of vertically extending elongated anodes suspended by means of inert plastic ropes from such platform and spaced from the piling between the low water line and the bottom beneath the installation, and electrical conductor means connecting solely the lower end of each anode to a source of direct current, said conductor means extending substantially horizontal and laterally away from the lower end of each anode in the region near the latter.

References Cited in the file of this patent UNITED STATES PATENTS 84,671 Baker et al Dec. 8, 1868 1,874,759 Kirkaldy Aug. 30, 1932 2,700,649 Hosford Ian. 25, 1955 2,838,453 Randall June 10, 1958 2,851,413 Hosford Sept. 9, 1958 2,870,079 McCall Ian. 20, 1959 2,876,190 Oliver Mar. 3, 1959 2,926,128 Flower Feb. 23, 1960

Claims

1. IN A CATHODIC PROTECTION SYSTEM FOR A MARITIME INSTALLATION HAVING A PLATFORM SUPPORTED ON SUBMERGED CORRODIBLE METAL PILING, A SERIES OF VERTICALLY EXTENDING ANODES SUSPENDED FROM THE PLATFORM AND SPACED FROM THE PILING, SAID ANODES BEING SUBMERGED BETWEEN THE LOW WATER LINE AND THE BOTTOM BENEATH THE INSTALLATION, SAID ANODES EACH HAVING A CONDUCTOR CONNECTING THE ANODES TO A SOURCE OF DIRECT CURRENT, SAID CONDUCTORS EXTENDING GENERALLY HORIZONTALLY BENEATH THE LEVEL OF THE ANODES AND BEING CONNECTED THERETO SOLELY THROUGH THE LOWERMOST POINTS THEREOF.