GB1568043A - Cathodic pipe protection system - Google Patents

Description

(54) CATHODIC PIPE PROTECTION SYSTEM (71) We, CAUNNED ESTABLISH MENT, a Company organised under the Laws of Liechtenstein of Im Städtle 35, Vaduz, Liechtenstein, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be described in and by the following statement: It is well known to construct pipes, for conveying all kinds of fluids, which have an electrically insulating inside covering without any break of continuity with respect to the ends of the elements composing the pipes, by the use of tubular elements as described in Italian patent No. 932747 (U.K. Patent Application No. 29808/72).

According to the above-mentioned patent, each piece of tube is provided at its ends with a joint portion and, in the formation of the pipe obtained by welding together the extreme ends of the abovementioned joint portions, the section of the pipe itself is maintained uniform in relation to the joint portions by the presence. in the inside opening of each joint portion, of a tube segment having the same inside diameter as the tube elements.The whole inside surface of the tube elements as well as that of the tube segment, the ends and a portion of the outside surface of the end, not jointed with the base of the joint portion are equipped with anti-corrosive covering, and finally the space enclosed between the inside walls of the joint portions and the outside wall of the tube segments enclosed therein is filled, after welding together of the ends of the joint portions, with a material which is made fluid at a certain temperature that will not damage the covering, and particularly a liquid resin or other product capable of being polymerized. or otherwise solidified at ambient temperature, or suitable for the working temperature of the pipes.

In this way there is obtained a complete protection of the inside surface of the pipes, without break of continuity.

In view of the fact that there are nevertheless unavoidable porosities of scratches on the inside covering, and therefore also small areas of bare surface, subject to corrosion, the above-mentioned patent provides a condition of cathode protection on the inside surface of the pipes by means of inserting on all or a portion of the joint members of toroidal anodes of reactive metal (zinc, magnesium. or aluminium, or an alloy of these) in direct electrical contact with the pipe surfaces. or by means of inserting between the opposed joint portions of all or of a part of the adjoining pipe elements, of a member serving as a muff and provided inside with a reactive toroidal anode.

Furthermore. in the above-mentioned patent, there is provided the possibility of obtaining the cathodic protection of the inside surface of the pipe by current impressed on indissoluble anodes inserted directly on some joint members, or contained in the muffs inserted between some joint members of the entire pipe, so that they are electrically insulated from the pipe surface and are connected, by electric cable also insulated from the pipe. with a suitable generator of direct current.

The present invention has for its object to improve such a system of cathodic protection. particularly for pipes carrying highly corrosive fluids, and provides a system to protect by the cathodic method the inside surface of a metallic pipe. constructed of tubular elements. with an electrically insulating inside covering without break in continuity, corresponding to the joints of the tubular elements.

This system is characterised in that the indissoluble anodes contained in the joint members or in the muffs between the joint members, are electrically connected with metallic cathodes, outside the pipe, in form of ropes, cables or plates disposed in the ground containing the pipes, by suitable treatment of this ground, in the case of soil, in order to allow that the above-mentioned cathodes drain the maximum possible current disseminated in the ground from the cathodic protection plant constructed to preserve the ouside surface of the pipe.

The electrical circuit for cathodic protection is made between the pipe, connected to the negative pole of the source of direct current, and a dispersor connected to the positive pole of the said source.

In this way it is possible, with only one cathode source, to preserve contemporaneously the ouside and the inside surface of the pipe, by means of two protective circuits in parallel, and in practice:- the first circuit extending between the positive pole of the current rectifier outgoing line, dispersor, electrolytic means, outside surface of the pipe, return line, negative pole of the rectifier, and the second between the positive pole of the current rectifier outgoing line, dispersor, electrolytic means outside the pipe, outside cathode of the pipe, anode and electrolyte inside the pipe, inside surface of the pipe return line, and negative pole of the source.

In the particular event of discharges, in the sea, of sewage effluents, these may be discharged very far from the water edge, and there may be avoided coastal pollution by use of steel-pipes which are cathode protected along the outside and inside surface according to the present invention.

In this case, in order to increase the electrical conductivity of the sewage effluent, and therefore to increase the spacing between the continuous couples of indissoluble cathode-anode, provision may be made to mix these sewage effluents with sea water by means of an injector-mixer.

By means of this device, there is also obtained the advantage of dilution of the sewage effluent in the discharge pipe, where it can also be injected with air or oxygen in order to achieve an aerobic action.

In a particular case, as for example sea water pipes for cooling circuits in vessels, each indissoluble anode may be directly fed from a battery adjacent to the anode itself.

An embodiment is shown in the accompanying drawings. wherein: Figures la, ib. and 1c together show a length of pipe; Figure 2 shows a joint.

This solution refers to pipelines immersed in an electrolytic environment (water or ground) and by means of this solution cathodic protection is obtained both on the external and on the internal surfaces of a pipeline by the use of the electrolytic fluid to convey the protective current.

In this case the current passes not only through the external surfaces of the pipeline, which becomes protected in this way, but also through the cathodic plates p electrically connected with insoluble anodes t through which the current is conveyed to the electrolyte r, and polarizes the areas s of the internal surface of the pipeline lacking any coating.

In this way two protective circuits in parallel are obtained, i.e.: 1st circuit: supplier c, disperser b, electrolyte e, external surface of the pipeline, pipeline, supplier c.

2nd circuit: supplier c, disperser b. electrolyte e, cathodic plates p, platinated titanium anodes t, fluid conveyed in pipeline r, uncovered areas of the internal surfaces s, pipeline, supplier c.

WHAT WE CLAIM IS: 1. A system to protect the inside surface of a metallic pipe constructed of tubular elements having their ends formed with joint portions and each having internally a tube section of the same diameter as the tubular element. this being provided with an electrically insulating inside covering without interruption of continuity, corresponding to the joints of the tube sections, characterized in that indissoluble anodes contained in the joint portions or between the joint portions and not in metallic contact with the pipe. are electrically connected with metallic cathodes outside the pipe and in the form of ropes, cables or plates inserted in the same gound as the pipes themselves, this ground being treated suitably. if composed of soil. in order to allow the cathodes to drain the maximum current, dispersed in this ground from the cathode protection plant provided to protect the outside covering of the pipe.

2. A system, as claimed in claim 1, characterized in that especially in the case of discharge in the sea of sewage effluents, these are mixed, before entering the pipe, with sea water in order to increase the electric conductivity and to increase the distance between the indissoluble anodes.

3. A system, as claimed in either of claim 1 and 2. characterized in that the case of sewage effluents, substances are added to make them more electrically conductive and if possible less polluting, air or oxygen being also added in order to obtain an aerobic action.

4. A system. as claimed in any one of claims 1 to 3, characterized in that the indissoluble anodes are fed from batteries positioned adjacent to the anodes themselves.

5. A pipe protection system substantially as described herein with reference to the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. metallic cathodes, outside the pipe, in form of ropes, cables or plates disposed in the ground containing the pipes, by suitable treatment of this ground, in the case of soil, in order to allow that the above-mentioned cathodes drain the maximum possible current disseminated in the ground from the cathodic protection plant constructed to preserve the ouside surface of the pipe. The electrical circuit for cathodic protection is made between the pipe, connected to the negative pole of the source of direct current, and a dispersor connected to the positive pole of the said source. In this way it is possible, with only one cathode source, to preserve contemporaneously the ouside and the inside surface of the pipe, by means of two protective circuits in parallel, and in practice:- the first circuit extending between the positive pole of the current rectifier outgoing line, dispersor, electrolytic means, outside surface of the pipe, return line, negative pole of the rectifier, and the second between the positive pole of the current rectifier outgoing line, dispersor, electrolytic means outside the pipe, outside cathode of the pipe, anode and electrolyte inside the pipe, inside surface of the pipe return line, and negative pole of the source. In the particular event of discharges, in the sea, of sewage effluents, these may be discharged very far from the water edge, and there may be avoided coastal pollution by use of steel-pipes which are cathode protected along the outside and inside surface according to the present invention. In this case, in order to increase the electrical conductivity of the sewage effluent, and therefore to increase the spacing between the continuous couples of indissoluble cathode-anode, provision may be made to mix these sewage effluents with sea water by means of an injector-mixer. By means of this device, there is also obtained the advantage of dilution of the sewage effluent in the discharge pipe, where it can also be injected with air or oxygen in order to achieve an aerobic action. In a particular case, as for example sea water pipes for cooling circuits in vessels, each indissoluble anode may be directly fed from a battery adjacent to the anode itself. An embodiment is shown in the accompanying drawings. wherein: Figures la, ib. and 1c together show a length of pipe; Figure 2 shows a joint. This solution refers to pipelines immersed in an electrolytic environment (water or ground) and by means of this solution cathodic protection is obtained both on the external and on the internal surfaces of a pipeline by the use of the electrolytic fluid to convey the protective current. In this case the current passes not only through the external surfaces of the pipeline, which becomes protected in this way, but also through the cathodic plates p electrically connected with insoluble anodes t through which the current is conveyed to the electrolyte r, and polarizes the areas s of the internal surface of the pipeline lacking any coating. In this way two protective circuits in parallel are obtained, i.e.: 1st circuit: supplier c, disperser b, electrolyte e, external surface of the pipeline, pipeline, supplier c. 2nd circuit: supplier c, disperser b. electrolyte e, cathodic plates p, platinated titanium anodes t, fluid conveyed in pipeline r, uncovered areas of the internal surfaces s, pipeline, supplier c. WHAT WE CLAIM IS:

1. A system to protect the inside surface of a metallic pipe constructed of tubular elements having their ends formed with joint portions and each having internally a tube section of the same diameter as the tubular element. this being provided with an electrically insulating inside covering without interruption of continuity, corresponding to the joints of the tube sections, characterized in that indissoluble anodes contained in the joint portions or between the joint portions and not in metallic contact with the pipe. are electrically connected with metallic cathodes outside the pipe and in the form of ropes, cables or plates inserted in the same gound as the pipes themselves, this ground being treated suitably. if composed of soil. in order to allow the cathodes to drain the maximum current, dispersed in this ground from the cathode protection plant provided to protect the outside covering of the pipe.

2. A system, as claimed in claim 1, characterized in that especially in the case of discharge in the sea of sewage effluents, these are mixed, before entering the pipe, with sea water in order to increase the electric conductivity and to increase the distance between the indissoluble anodes.

3. A system, as claimed in either of claim 1 and 2. characterized in that the case of sewage effluents, substances are added to make them more electrically conductive and if possible less polluting, air or oxygen being also added in order to obtain an aerobic action.

4. A system. as claimed in any one of claims 1 to 3, characterized in that the indissoluble anodes are fed from batteries positioned adjacent to the anodes themselves.

5. A pipe protection system substantially as described herein with reference to the

accompanying drawings.