EA023227B1 - System of cathode protection for underwater object - Google Patents

Abstract

The invention relates to a protection of underwater objects from corrosion using an electrochemical method. The increase of protection potential on an object is reached due to the implemention of the system made as a chain of series connected galvanic cells. By one end the chain is connected to the protected object, by the other to an electrode positioned near the protected object. An anode of the galvanic cell is connected to a cathode of a neighbor galvanic element through a metallic conductor. The distance between the cathode and the anode of each galvanic cell is at least 1.1 times lesser the distance between the anode of one galvanic cell and the cathode of the neighbor galvanic element. The chain of galvanic cells connected by metallic conductors is positioned in the direction perpendicular to the axis of the protected pipe. A water medium serves as electrolyte of the galvanic cells.

Description

The invention relates to the operation of underwater parts of oil and gas pipelines, in particular to means for their protection against corrosion by an electrochemical method.

Known bracelet made of protectors for corrosion protection of the underwater part of metal structures of the structure according to the patent of the Russian Federation for invention No. 2270277, С23Р 13/06, 2006. The bracelet consists of protectors in the form of plates with support elements rigidly connected to the supporting reinforcement. The supporting reinforcement is two half-cylinders connected among themselves. The disadvantage of the invention is the complexity of installing the bracelet on an underwater structure, the low protective potential created at the protected object.

A cathodic protection device for a marine structure is known according to the US application for invention No. 2008199258. The cathodic protection device for a marine structure contains vertical columns installed in the bottom underwater around the protected structure. The anodes of the columns are electrically connected to the marine structure. The disadvantage is the difficulty of installing a large number of columns necessary to create the required protective potential.

As the closest analogue to the claimed technical solution, US patent No. 6461082 was selected, according to which the cathode anti-corrosion protection system includes an elongated anode holder made in the form of a pipe placed at the bottom. A plurality of sacrificial anodes connected to the pipe are stably fixed to the pipe along its length. The pipe is connected by an electric conductor with an underwater protected object. The disadvantage is that the materials of the anodes alloys of aluminum, zinc or magnesium - have a greater electrochemical activity in relation to the material of the steel pipe. Electrochemical processes take place between the anode holder tube and the anodes, as a result of which not only the protected object is exposed to cathodic protection, but also the steel pipe on which the anodes are mounted. The effectiveness of the process of restoring the metal surface of the protected object is reduced.

The technical result of the claimed invention is to increase the protective potential at the protected object.

The technical result is achieved due to the fact that the cathodic protection system of an underwater object, consisting of electrodes and conductors placed in water, according to the invention is made in the form of one or more series-connected galvanic cells, the cathode of one galvanic cell is connected to the anode of the neighboring galvanic cell by a metal conductor, a circuit of galvanic cells from one end is connected to the protected object, its other end is connected to an electrode located near the protected about the object, the distance between the galvanic cells is not less than 1.1 distances between the electrodes of each galvanic cell.

A chain of galvanic cells connected by metal conductors is located in a direction perpendicular to the axis of the protected pipe.

The electrolyte of galvanic cells is an aqueous medium.

The technical result is ensured by the fact that the electrode located near the protected object is connected to a galvanic cell or to a chain of series-connected galvanic cells. Each galvanic cell consists of two dissimilar electrodes in contact with an electrolyte, which is the water in which they are placed. The anode located near the protected object, together with the protected object itself, is also a galvanic cell in which electric energy is generated as a result of direct conversion of the chemical energy of redox reactions. In a circuit of galvanic cells, the cathode of each cell has a potential higher than the anode of the same cell. The anode and cathode of two adjacent galvanic cells are connected by an elongated metal conductor. The medium resistance between the anode of one galvanic cell and the cathode of another galvanic cell is much higher than the internal resistance between the electrodes of these galvanic cells. Therefore, the current encountered in relation to the galvanic cell will be (I = and / K) much weaker than the current arising inside the galvanic cell. Current in the anode circuit of one galvanic cell, the cathode of the next will flow through a metal conductor connecting them. The resistance of the conductor is much lower than the resistance of water, which is an electrolyte for galvanic cells ^, and the counter resistance in the conductor is ^{1> K} ? ^{To 0} > ^and counter in the conductor ⁰ . ^{Therefore, the vapor} pair of the ^current TO ^{com in the conductor} can be neglected. And the circuit current of the series-connected conductors will be directed in accordance with the direction of the current of the galvanic cells. The potential difference in the circuit of the galvanic cells is the sum of the potential difference on the electrodes of each galvanic cell, i.e. and total = I1 + and2 + and _n .

The distance between the anode and the protected object, as well as the distance between the cathode and anode of each galvanic cell, is not less than 1.1 times less than the distance between the anode of the previous and the cathode of the subsequent galvanic cells. The cathode of one galvanic cell is remote from the anode of a neighboring galvanic cell so that there is no electrochemical interaction between them. An electrochemical reaction proceeds only between the electrodes of one galvanic cell, and in the case of an anode located near the protected object, between it and the protected object. With a significant removal of the anode from the protected object, the activity of electrochemical processes decreases. With this implementation of the cathodic protection system, there are no losses associated with electrochemical reactions between the anode protectors and the elongated metal holders of the anodes of the closest analogue.

Thus, an increase in the protective potential is provided through the use of a circuit of galvanic cells and due to the implementation of conductors connecting galvanic pairs elongated.

The drawing shows a diagram of the cathodic protection system of an underwater object.

Underwater object cathodic protection system comprises an anode 1 located underwater near the perimeter of the tube 2. The anode 1 is connected with the cathode 3 _by an elongated metal conductor 4, near the cathode 3 is set _{to the} anode 3 _while forming the cathode 3 _{to the} electrochemical cell, the electrolyte between the electrodes of the a galvanic cell is the water in which the protected pipe 2 is located. Anode 3 _{k is} connected by an elongated metal conductor 4 to the next pair of electrodes forming a galvanic cell 5 _k and 5 _a , or with a protected pipe 2. Chain galvanic elements n _k + n _and connected by metal wires 4 is disposed in a direction perpendicular to the axis of the tube 2 to be protected, which provides maximum distance of electrochemical cells of the protected pipe 2. The outermost galvanic element is disposed at a distance from the axis of the tube 2 is about 200 m. Electrodes galvanic cells are fixed at the bottom. During cathodic protection, an electric current occurs between the electrodes of each galvanic cell. The protected pipe 2 is in a closed electrical circuit. The loss of electrons on its surface due to the corrosion of metals is compensated by electrons formed as a result of an electrochemical reaction inside the galvanic cells, and between the anode 1 and the protected tube 2. The anodes of the galvanic cells are made of tread alloys, for example aluminum and zinc. Cathodes can be made of copper, stainless steel.

The use of this system in the Kama River showed that the initial voltage in the galvanic pair of the anode-protected object is 0.9 V. Connection of each galvanic pair connected in the above way increases the value of the voltage between the protected object and the anode located near it by 1.68 V.

Thus, the invention allows to increase the protective potential of the protected object.

Claims (3)

CLAIM 1. The cathodic protection system of an underwater object, consisting of electrodes and conductors placed in water, characterized in that it is made in the form of one or more series-connected galvanic cells, the anode of one galvanic cell is connected to the cathode of the neighboring galvanic cell by a metal conductor, the galvanic cell circuit with one end is connected to the protected object, its other end is connected to the electrode located near the protected object, the distance between the galvanic cells Tammy is not less than 1.1 the distance between the electrodes of each cell. 2. The cathodic protection system of an underwater object according to claim 1, characterized in that the circuit of the galvanic cells connected by metal conductors is located in a direction perpendicular to the longitudinal axis of the protected object. 3. The cathodic protection system of an underwater object according to claim 1, characterized in that the electrolyte of the galvanic cells is an aqueous medium.