MXPA96004140A - Cathodic protection system against vandalism for steel ducts of high risk, which transport oil hydrocarbons and its petrochemical by-products - Google Patents

Abstract

The"cathodic protection"is a technology to prevent metallic structures from corrosion. The construction of these systems has been based for many years on the use of copper cables of different gauges in all their circuits. The proposed new system (against vandalism), does no change nor alter the intrinsic electrochemical phenomena of the cathodic protection;it is chiefly based on the substitution of the copper cables for steel pipes and interconnections, previously calculating their dimensions and specifications and exteriorly lined with dielectric thermal-contractile adhesive by thermalfusion plastic materials. The pipes already installed, is drown in all its length in a concrete cylinder. This new system also involves the substitution of a traditional anodic device for a monolithic-type one, in which there are also eliminated all the copper cables. It is conformed by a core of steel pipes, surrounded by a mixture of graphite carbon with various inches of thickness, Portland cement, calcium oxide, calcium sulphate, additives and water. In order to operate, a direct electric current is circulated by the pipes metal, by means of appropriate adjustments of voltage gradients in a regulator device, installed in the energy source of the cathodic protection system itself.

Description

CATHODIC PROTECTION SYSTEM "AGAINST VANDALISM" FOR HIGH RISK STEEL DUCTS, WHICH TRANSPORT PETROLEUM HYDROCARBONS AND THEIR PETROCHEMICAL DERIVATIVES. BACKGROUND OF THE INVENTION It is known as "Cathodic Protection" an electrochemical phenomenon that man uses to prevent corrosion of buried or submerged metal structures. See: Pipe Une Corrosion and Cathodic Protection, Third Edition, Parker-Peattie, Gulf Publishing Company; Underground Corrosion, ASTM-Committee G-1, Technical Publication 741; Cathodic Protection, Second Edition, John Morgan, National Association of Corrosion Engineers; Control of Pipe Line Corrosion, A.W. Peabody N.A.C.E. Houston, Tex .; NACE-Standard RP-169-92 Control of External Corrosion on Underground or Submerged Metallic Piping Systems. NACE-Houston, Tex. 15 In all the Cathodic Protection Systems for buried metallic ducts that are currently known, copper cable of different calibers and in lengths of several hundred meters is used between the circuits (ANODO-RECTIFIER- CATODO). This system has been disadvantageous in various population areas, since that are destroyed and looted by vandalism groups; thus putting, from this moment, in a high degree of risk to the facilities that drive petroleum hydrocarbons and petrochemical derivatives, which received the benefits of the Cathodic Protection.

The objective of the invention is to modify the conventional elements of current Cathodic Protection Systems (without altering their intrinsic electrochemical phenomenon), by suitable elements, functional and of a high physical resistance, to counteract the attacks of vandalism; thus ensuring the continuous, efficient and safe protection of high-risk metallic installations.

DESCRIPTION OF THE INVENTION The characteristic details of this novel system are clearly shown in the following description and in the accompanying drawings, as well as an illustration thereof and following the same reference signs to indicate the parts and figures shown.

Figure 1 is a conventional perspective of the CATHODIC PROTECTION SYSTEM AGAINST VANDALISM. Figure 2 is a longitudinal section of an ANODIC DEVICE TYPE MONOLITHIC SECTIONABLE. Figure 3 is a THREE SECTION MONOLITHIC ANODIC DEVICE. Figure 4 is a diagram of a CATHODIC PROTECTION SYSTEM CONTRA-VANDALISM, OPERATED BY A GAS TURBINE, FOR REMOTE SITES.

Each Cathodic Anti-Vandalism Protection System must first be designed in its capacities and dimensions, according to the specific requirements of the structures to be protected. The calculation forms and specifications for the realization of designs, are derived mainly from Ohm's Law and its mathematical ramifications. See reference: Control of Pipe Une Corrosion, A.W. Peabody - NACE. Houston, Tex. (Chapter 7 and 8).

The monolithic anodic device (No. 1), is formed by a core (No. 9) of steel pipe 3 to 6 inches in diameter, in a length that can vary from 20 to 50 meters (as required). A series of stirrups (No. 8) of steel rebar 1 inch in diameter by 50 cm. in length, welded at both ends to the core pipe (No. 9). After mechanical cleaning of the pipe surface (No. 9), a coating (No. 5) based on a conductive acrylic monomer is applied to a minimum thickness of 30 mils. The anodic device (No. 1), is introduced in an excavation of appropriate dimensions up to 1.0 meters deep and is surrounded up to 16"0 of a mixture (No. 11) consisting of: 94.0% Mexican-type graphite carbon, 3.0% Type I portland cement, 1.0% calcium hydroxide, 1.0% calcium sulfate, 1.0% type I additive, 1.0% calcium hydroxide, 1.0% calcium sulfate, 1.0% integral waterproofing additive (FESTER or similar) and clean water without chlorides, enough to saturate the mixture (% by weight).

As a direct current generator (No. 7) can be used commercial equipment such as thermo-generators, turbo-generators, and alternating current rectifiers mounted in weldable and heavy-gauge metal enclosures to provide strong shielding.

The monolithic anodic device (No. 1), located generally at an average distance of 100 meters from the Current Generator (No. 7), is joined through welds of weldable steel pipe (No. 3) of 3 inches in diameter; previously coated on the outside with a thermocontractable dielectric plastic material with thermofusion adhesive (RAYCHEM or similar). This coating will be tested for its effectiveness by porosity detector equipment adjusted to a minimum voltage of 1,000 volts.

The rectifier of Current (No. 7) and the cathode group integrated by the pipes to be protected (No. 2), will also be joined by pipe rings (No. 3) of 3 inches of weldable steel diameter, applying them equally that in the previous paragraph, an outer dielectric coating and testing its insulating effectiveness.

The pipe (No. 3) is placed in suitable 1.0 meter deep excavations, which will be surrounded, throughout its length, by a concrete cylinder (No. 4) with a minimum resistance F'c = 150 Kg / Cm2 and with dimensions of 25 cm. X 25 cm. The excavations are finally covered with the material produced by them.

The "Current Pipe" (No. 3) on the cathodic side of the generator will be connected to each of the pipes to be protected (No. 2) (which transport hydrocarbons), by means of a 25-centimeter-long section of cable. of copper isolated 4 gauge AWG, using the welding technique by aluminotermia, whose technology is already well known. can be concentrated in the current generator cabinet (No. 7). It consists of a 2-inch diameter steel tube core measuring 1.20 meters in length, surrounded by up to an inch diameter of the same chemical mixture used to integrate the Monolithic Anodic Device (No. 1). It is placed vertically in an excavation of suitable proportions from a depth of 0.8 meters from the natural level of the ground and is interconnected with the "ground" terminal of the current generator (No. 7) by means of a 2-inch pipe extension. diameter by 1.08 meters in length, dielectrically lined with the same heat shrink materials used in the "current pipes" (No. 3); this pipe will also be drowned in a concrete cube with minimum strength F'c = 150 Kg / Cm2 of 15 by 15 centimeters over the entire length of 1.8 meters.

The direct electric current in this new Cathodic Protection System will be circulated, according to the requirements of each particular system, through appropriate voltage adjustments in a commercial type regulator device, installed in the Energy Source of the system itself (No 7).

With reference to Figure 2, the longitudinal section of a SECTIONABLE MONOLITHIC TYPE ANODIC DEVICE section is illustrated therein. It is designed to be installed on dehydrated soils and high dryness. The objective of sectioning the Monolithic Anodic Device is to avoid cracks in the body of the device that would create electrical discontinuities within its mass. These discontinuities may cause concentrations of undesirable currents in some areas of the Anodic Device, causing excessive consumption of material at those points and therefore a reduction in its useful life.

Each Section of Anodic Device Type Monolithic Seccionable, of a maximum length each of 5 meters, is conformed by a core (No. 9) of carbon steel pipe of 3, 4 or 6 inches in diameter in a total length of the Device Anodic of approximately 50 meters (ten sections) according to the current requirements of each Cathodic Protection System in particular; a series of stirrups (No. 8) of steel rebar? inch diameter of 5 centimeters in height by 50 centimeters in length, welded by the electric arc process, its ends to the core pipe (No. 9). The steel stirrups (No. 8) will be distributed along the core pipe (No. 9) at intervals of 50 centimeters and in groups of ? - four, corresponding in each cross section to positions 0o, 90 °, 180 ° and 270 °.

On the surface of the pipe (No. 9) and after mechanical cleaning of its surface, it is applied to a minimum thickness of 30 mils., A resin (No. 5) with waterproof and conductive characteristics of electricity, formed by a mixture of 62% by weight of modified epoxy resin (NAPKO) and 38% of finely powdered graphite (MEXICAN TYPE). The objective of this resin (No. 5) is to put a waterproof barrier and conductive between the pipe (No. 9) and the mixture (No. 11) in order that the electrolyte of the ground does not make direct contact with the steel of the pipe (No. 9) preventing the metal from entering very quickly in solution and therefore will have a longer life of the pipe core (No. 9).

On the pipe core (No. 9) and at a separation distance of every 5 meters, insulating sleeves (No. 10) of heat-shrinkable plastic material (RAYCHEM or similar) of 12 inches in length will be placed, in order to to isolate in this section the pipe (No. 9) of the contact with the electrolyte of the soil and to avoid its premature wear. 20 Along the pipe section (No. 9) of 5 meters of the Anodic Device type The Monolithic Seccionable, will be surrounded with a layer of five inches of thickness of the mixture (No. 11) formed by graphite, portland cement, calcium hydroxide, calcium sulfate and waterproofing additive. 25 These Anodic Device Sections are installed in the soil in an excavation with a minimum depth of 1 meter.

With reference to figure No. 3, there is illustrated a group of three sections (No. 12) 30 of an ANODIC DEVICE TYPE MONOLITHIC SECTIONABLE. As mentioned in the description of Figure 2, the objective of sectioning the total length of the device (which results from the specific design for each Cathodic Protection System in particular) is to avoid as much as possible the possibility of cracks in its mass during the time of setting of the mixture and decreasing its period of useful life of current drainage to structures buried or submerged to protect against corrosion.

Figure 3 shows an Anodic Device of 3 sections (No. 12) of 5.0 meters length each, making a total length of 15.0 meters. Between each section (No. 12), a separating disk (No. 13) of compressible polyurethane 10 centimeters thick and an outer diameter of 16 inches is placed. The purpose of this separating disk (No. 13) is to dampen the expansions that due to the effect of temperature in the subsoil, could crack or damage the conductive concrete mass of the sections (No. 12) of the Anodic Device.

The field construction of an Anodic Device of 3 sections or more, will be done according to the same procedure described in Figure 2 which refers to the construction of only one section of Anodic Device.

The parts that make up an Anodic Device with 3 sections or more, are identical to those described in figure 2 and correspond to: carbon steel core (No. 9), insulating heat shrink sleeves (No. 10), rebar stirrups of steel (No. 8), waterproof resin - conductive at 30 mils. (No. 5) and 5-inch thick layer of conductive mixture (No. 11).

This Anodic Device of 3 sections or more will be installed and operated on the ground in an excavation at a minimum depth of 1 meter.

With reference to figure 4; This shows an installation diagram of a Cathodic Anti-Vandalism Protection System, powered by a gas turbine and that can be used in remote areas of Road Rights of oil and gas pipelines in which there is no alternating electric current available. Its construction and operation is based on the same principles and elements of the system described in detail and corresponding to Figure 1 and that are: Monolithic Anodic Device (No. 1), Catodic Group of pipes to protect (No. 2), Steel pipes as interconnection elements (No. 3), Concrete shell on interconnection pipes (No. 4), Monolithic type "earth" system (No. 6) and Direct current generator (No. 7). The only difference is that in Figure 1, the Current Generator (No. 7) is powered by alternating current of 110/220/440 Volts and in Figure 4 the Generator (No. 7) is powered by a system of Gas Turbine (No. 15) of the type specially designed for Cathodic Protection and very well known worldwide. This Generator (No. 7) is powered by a Gas Turbine (No. 15) which in turn is powered by a gas flow, which transport the same pipes to protect (No. 2). The speed of the turbine (No. 15) is controlled by a mechanism of Pressure Reduction (No. 14) and Flow Regulation (No. 16). ^

Claims (6)

1. CLAIMS Having sufficiently described my invention that I consider as a novelty and therefore claim as my exclusive property, contained in the following 5 clauses: 1. - A Cathodic Protection System in which the NEGATIVE current generated with a direct current energy source is flowed over the metal structures to be protected (buried or submerged) through a pipeline. 10 carbon steel (scrap type) that can be of different diameters, thicknesses and specifications, according to the design currents and voltages required and calculated for each cathodic protection system in particular. The steel pipe, with a specific known conductance, has a plastic dielectric coating tape of the thermo-shrinkable type with adhesive on the outside. 15 thermofusion, tested with a porosity detector equipment at a minimum voltage of 1, 000 volts. The above in order to avoid the "landing" of the current that is flowed by it when putting into operation the Cathodic Protection System. The current is flowed through appropriate voltage adjustments in a regulating device installed in the Power Supply of the Cathodic Protection System itself. 20 2.- A Cathodic Protection System in which the POSITIVE direct current, which is generated in the Direct Current Power Source, is flowed to an Anodic Device Monolithic type (buried) through a carbon steel pipeline. (scrap type), dielectrically insulated on its outside with a coating tape 25 of thermo-shrinkable plastic material with thermo-melt adhesive, tested with a porosity detector equipment at a minimum voltage of 1,000 Volts. The steel pipe can also be of different diameters, thicknesses and specifications according to the currents and voltages required for each cathodic protection system in particular. 30 The POSITIVE direct current that leaves the buried Monolithic Anodic Device flows through the ground to the pipes that are intended to be protected and from these the current returns to the NEGATIVE terminal of the Current Source, through the pipe that interconnects the metallic structures by Protect and the Source of Current. The POSITIVE current is also flowed, by appropriate adjustments of voltage gradients in the regulating device installed in the Power Source. 3. - A Cathodic Protection System in which dielectrically-lined carbon steel pipes (Type scrap) through which the direct POSITIVE and NEGATIVE currents generated in the Power Source are flowed, are drowned in their entire length in a concrete cylinder of anti-vandal shielding with a minimum resistance F'c = 150 Kg / Cm2 and with dimensions of 25 X 25 cms. The above in order to form a physical shield and high resistance around the buried pipes through which the direct currents mentioned above flow. The tubing dielectrically lined and drowned in the shielding concrete, is housed in an excavation at a minimum depth of 1 meter. 4. - A Cathodic Protection System in which a POSITIVE direct current is made to flow through the ground and into the ducts to be protected, by means of a buried Monolithic Anodic Device, formed by a core of bare steel pipe (scrap) of 3 a 6 inches in diameter of different thicknesses and specifications and from 20 to 50 meters in length, according to your current drainage requirements, with a series of stirrups constructed of corrugated rod of Vi inch diameter by 50 centimeters in length, welded in their 2 ends to the core pipe. These abutments have the function of serving as anchors to a cylinder of 16 inches in diameter, which surrounds the "core pipe", formed by a mixture of 94.0% graphite carbon, 3.0% portland type I cement, 1.0% Calcium sulfate, 1.0% calcium hydroxide, 1.0% integral waterproofing additive and water in sufficient quantity to make the mixture. 5. - A Cathodic Protection System with a Monolithic "Ground Device", whose objective is the protection of operative personnel against high voltage electrical discharges. It consists of a cylinder with a core of steel pipe 2 inches by 1.20 meters. in length, surrounded up to 8 inches in diameter with the chemical mixture described in the previous clause (4) of these Claims. This cylinder is buried vertically at a depth of 80 centimeters from its upper end. This "ground device" is connected to the "EARTH" terminal of the Power Source, by means of a steel pipe (scrap), 2 inches in diameter by 1.8 m. Of length dielectrically lined with sleeves and thermocontractable materials, testing its insulation at 1,000 Volts. The pipe section of 2"diameter by 1.80 meters in length will be drowned in a concrete cube with a minimum resistance of F'c = 150 Kg / Cm2 with dimensions of 15 X 15 centimeters, this in order to form a shield of protection against vandalism for this element. 6. - A Cathodic Protection System with a Monolithic Anodic Device in which the "pipe-core" of scrap steel, 3 to 6 inches in diameter is coated, in the first term, with a waterproof and conductive film based on a Acrylic monomer or epoxy-modified resin and Mexican-type graphite finely powdered in the proportion of 62% (by weight) of monomer or resin and 38% of graphite, applied by brush on the surface of the pipe to a minimum thickness of 30 thousandths of an inch dry film. The function of the waterproof and conductive film is so that when the system is put into operation and the direct current flowing from the anode flows to the electrolytic medium that is the ground, this film reduces or minimizes the rate of wear or consumption of Iron material of the steel tube to values that significantly increase the useful life of this Anodic Device.