Journal of commissioned cathodic protection stations. Systems of electrochemical protection, their operation. Welders during work are prohibited

4.7 OPERATION OF ELECTROCHEMICAL PROTECTION INSTALLATIONS

4.7.1 During the operation of ECP installations, periodic technical inspections and verification of the effectiveness of their operation should be carried out.

Each protective installation must have a control log in which the results of inspection and measurements are recorded.

4.7.2 Maintenance of ECP units during operation should be carried out in accordance with the schedule of technical inspections and scheduled preventive repairs. The schedule of technical inspections and scheduled preventive repairs should include the definition of the types and scope of inspections and repairs, the timing of their implementation, instructions on organizing accounting and reporting on the work performed.

The main purpose of the work is to keep ECP protection installations in full working order, to prevent their premature wear and failures.

4.7.3 Technical inspection includes:

Inspection of all elements of the installation in order to identify external defects, check the density of contacts, serviceability of installation, the absence of mechanical damage to individual elements, the absence of burn marks and traces of overheating, the absence of excavations along the route of drainage cables and anode grounding;

Checking the health of the fuses;

Cleaning the housing of the drainage and cathode converter, the unit of joint protection from the outside and inside;

Measurement of current and voltage at the output of the converter or between the galvanic anode (protector) and the pipe;

Measurement of the polarization or total potential of the pipeline at the connection point of the installation;

Production of an entry in the installation log about the results of the work performed.

4.7.4 Maintenance includes:

Measuring the insulation resistance of supply cables;

One or two of the following repair works: power lines (up to 20% of the length), rectifier unit, control unit, measuring unit, unit housing and attachment points, drain cable (up to 20% of the length), contact device of the anode ground loop, loop anode grounding (less than 20% in volume).

4.7.5 Overhaul includes:

All technical inspection works;

More than two repairs listed in paragraph 4.7.4, or repairs in the amount of more than 20% - power line, drain cable, anode ground loop.

4.7.6 Unscheduled repair - a type of repair caused by equipment failure and not provided for by the annual repair plan.

Equipment failure must be recorded by an emergency act, which indicates the causes of the accident and the defects to be eliminated.

Technical inspection - 2 times a month for cathodic installations, 4 times a month - for drainage installations and 1 time in 6 months - for galvanic protection installations (in the absence of telemechanical control). If telemechanical control means are available, the timing of technical inspections is established by the management of the operating organization, taking into account data on the reliability of telemechanical devices;

Maintenance - 1 time per year;

Overhaul - depending on the operating conditions (approximately 1 time in 5 years).

4.7.8 In order to promptly perform unscheduled repairs and reduce interruptions in the operation of ECP in organizations operating ECP devices, it is advisable to have a reserve fund of converters for cathodic and drainage protection at the rate of 1 backup converter for 10 operating ones.

4.7.9 When checking the parameters of electrical drainage protection, the drainage current is measured, the absence of current in the drainage circuit is established when the pipeline polarity changes relative to the rails, the drainage response threshold is determined (if there is a relay in the drainage circuit or control circuit), as well as resistance in the electrical drainage circuit.

4.7.10 When checking the operating parameters of the cathode station, the cathodic protection current, the voltage at the output terminals of the cathode station and the potential of the pipeline at the contact device are measured.

4.7.11 When checking the parameters of the galvanic protection installation, measure:

1) current strength in the circuit galvanic anode (GA) - protected structure;

2) potential difference between the HA and the pipe;

3) the potential of the pipeline at the point of connection of the HA with the HA connected.

4.7.12 ECP efficiency is checked at least 2 times a year (with an interval of at least 4 months), as well as when changing the operating parameters of ECP units and when changing corrosion conditions associated with:

Laying new underground structures;

Changing the configuration of the gas and rail network in the protection zone;

ECP installation on adjacent communications.

4.7.13 The ECP efficiency of underground steel pipelines is monitored by the polarization potential or, if it is not possible to measure it, by the total potential of the pipeline at the connection point of the ECP installation and at the boundaries of the protection zones it creates. To connect to the pipeline, control and measuring points, entrances to buildings and other elements of the pipeline available for measurements can be used. The pipeline to the point of connection should not have flange or electrically insulating connections, unless electrical jumpers are installed on them.

4.7.14 The polarization potential of steel pipelines is measured on stationary instrumentation equipped with a long-term copper sulfate reference electrode with a potential sensor - auxiliary electrode (CE, Fig. 4.7.1), or on non-stationary instrumentation using a portable copper sulfate reference electrode with a potential sensor - auxiliary electrode (VE, Fig.4.7.2).

Fig.4.7.1 Scheme for measuring the polarization potential on stationary instrumentation

1 - pipeline; 2 - control conductors; 3 - device type 43313.1; 4 - stationary copper sulfate reference electrode; 5 - potential sensor.

Note:

Fig.4.7.2 Scheme for measuring the polarization potential on non-stationary instrumentation

1 - pipeline; 2 - potential sensor; 3 - portable copper sulfate reference electrode; 4 - device type 43313.1

Note:

When using a device of the PKI-02 type, the conductor from the pipeline is connected to the corresponding terminal of the device.

4.7.15 For measurements of the polarization potential on non-stationary instrumentation, a SE and a portable copper sulfate reference electrode are used, which are installed in a special pit for the duration of measurements.

The preparation of the pit and the installation of the wind turbine are carried out in the following order:

At the intended measurement point (where it is possible to connect to the pipeline), with the help of a route finder or by references on the pipeline route plan, the location of the pipeline is determined.

Above the pipeline or as close as possible to it, in the place where there is no road surface, a pit is made with a depth of 300-350 mm and a diameter of 180-200 mm.

The sensor (SE) and the portable reference electrode should be installed at a distance of at least 3 h from hydraulic seal tubes, condensate collectors and control tubes ( h- distance from the earth's surface to the upper generatrix of the pipeline).

Before installation in the ground, the VE is cleaned with a sandpaper (GOST 6456-82) with a grain size of 40 or less and wiped dry. Previously, solid inclusions larger than 3 mm must be removed from the part of the soil taken from the bottom of the pit that is in contact with the SE. A layer of soil 30 mm thick is poured onto the leveled bottom of the pit. Then the SE is laid with the working surface down and covered with soil up to a mark of 60-80 mm from the bottom of the pit. The soil above the wind turbine is tamped with a force of 3-4 kg per area of ​​the wind turbine. A portable reference electrode is installed on top and covered with soil. Before installation, a portable reference electrode is prepared according to clause 4.2.12. In the presence of precipitation, measures are taken to prevent soil moisture and moisture ingress into the pit.

4.7.16 To measure the polarization potential, devices with a current interrupter are used (for example, type 43313.1 or PKI-02).

The current interrupter provides alternate connection of the SE to the pipeline and to the measuring circuit.

Measurements on stationary and non-stationary instrumentation are carried out as follows. To the appropriate terminals of the devices (Fig. 4.7.1 and 4.7.2) connect the control conductors from the pipeline, SE and reference electrode; turn on the device. 10 minutes after turning on the device, the potentials are measured with the recording of the results every 10 s or, when using the PKI-02 device, with storage in the memory of the device. The duration of measurements in the absence of stray currents is at least 10 minutes. In the presence of stray currents, the duration of measurements is taken in accordance with the recommendations set out in clause 4.2.13.

The measurement results are recorded in the protocol (Appendix C).

Notes:

1. The duration of measurements of the potential of the pipeline at the connection point of the protection installation during its technical inspection (see clause 4.7.3) can be 5 minutes.

2. If the SE is permanently connected to a cathodically polarized pipeline on a stationary instrumentation, then the measurements of the polarization potential begin immediately after the device is connected.

4.7.17 Average polarization potential E Wed, V, is calculated by the formula:

,

where  E i- sum of measured n values ​​of polarization potentials (V) for the entire measurement period;

n is the total number of measurements.

4.7.18 Upon completion of the measurement work on the non-stationary instrumentation and removal of the reference electrode and the SE from the pit, the pit is covered with soil. In order to ensure the possibility of repeated measurements at a given point on the pipeline laying plan, a reference is made to the measurement point.

4.7.19 To determine the efficiency of ECP by the total potential (including the polarization and ohmic components), devices such as EV 2234, 43313.1, PKI-02 are used. Portable reference electrodes are installed on the surface of the earth at the minimum possible distance (in plan) from the pipeline, including at the bottom of the well. Measurement mode - according to item 4.7.15.

4.7.20 Average value of total potential U Wed(B) calculated by the formula:

,

where  U i- the sum of the values ​​of the total potential, n is the total number of readings.

The measurement results are recorded in a summary log (Appendix C), and can also be recorded on maps of underground pipelines.

4.7.21 In case of protection according to the softened security criterion, the minimum (in absolute value) protective polarization potential is determined by the formula:

E min = E st- 0.10 V,

where E st- stationary potential of the auxiliary electrode (potential sensor).

The polarization potential is measured in accordance with paragraph 4.7.15.

For determining E st sensor (SE) the sensor is disconnected from the pipe and 10 minutes after disconnection, its potential is measured E. If the measured potential is more negative - 0.55 V, then this value is taken as E st. If the measured potential is equal to or less than 0.55 V in absolute value, then E st= -0.55 V. Values E st(measured and accepted) are recorded in the protocol (Appendix C).

4.7.22 If an inefficient operation of cathodic or drainage protection installations is detected (their coverage areas are reduced, potentials differ from permissible protective ones), it is necessary to regulate the operating mode of ECP installations.

If the potential of the pipeline at the connection site of the galvanic anode (GA) turns out to be less (in absolute value) than the design or minimum protective potential, it is necessary to check the serviceability of the connecting wire between the GA and the pipeline, the places of its soldering to the pipeline and the GA. If the connecting wire and its soldering points turn out to be serviceable, and the potential does not increase in absolute value, then a pit is made to the depth of the HA digging to inspect it and check for backfill (activator) around it.

4.7.23 The current spreading resistance of the anode grounding should be measured in all cases when the operating mode of the cathode station changes dramatically, but at least once a year.

The spreading resistance of the anode grounding current is determined as the quotient of dividing the voltage at the output of the cathode installation by its output current or using the M-416 device and steel electrodes according to the diagram in Fig. 4.7.3.

Fig.4.7.3 Measurement of resistance to current spreading of anode grounding

1 - anode ground electrodes; 2 - control and measuring point; 3 - measuring device;

4 - measuring electrode; 5 - supply electrode; 6 - drainage wire.

With the length of the anode earthing l a.z the supply electrode is taken to a distance b 3 l a.z, measuring electrode - at a distance a 2 l a.z

4.7.24 The protective grounding resistance of electrical installations is measured at least once a year. The scheme for measuring the resistance to spreading of the protective earthing current is shown in Fig. 4.7.3. Measurements should be taken during the driest time of the year.

4.7.25 The serviceability of electrically insulating connections is checked at least once a year. For this purpose, special certified indicators of the quality of electrically insulating connections are used.

In the absence of such indicators, the voltage drop across the electrically insulating joint or synchronously the potentials of the pipe on both sides of the electrically insulating joint are measured. The measurement is carried out using two millivoltmeters. With a good electrically insulating connection, the synchronous measurement shows a potential jump.

In the case of the use of insulating inserts, CJSC "Ecogas"; (Vladimir), which have a metal coupling isolated on both sides of the pipeline, their serviceability can be checked by determining the resistance of the coupling relative to each side of the pipeline using a megger with a voltage of up to 500 V. The resistance must be at least 200 kOhm.

The results of the check are drawn up in protocols in accordance with Appendix Ch.

4.7.26 If 6 or more failures in the operation of the converter were observed at the operating ECP installation during the year, the latter must be replaced. To determine the possibility of further use of the converter, it is necessary to test it in the scope provided for by the requirements of pre-installation control.

4.7.27 If during the operation of the ECP unit the total number of failures in its operation exceeds 12, it is necessary to conduct a survey of the technical condition of the pipeline along the entire length of the protective zone.

4.7.28 Organizations that operate ECP devices must annually compile a report on failures in their work.

4.7.29 The total duration of interruptions in the operation of ECP units should not exceed 14 days during the year.

In those cases when, in the coverage area of ​​a failed ECP installation, the protective potential of the pipeline is provided by neighboring ECP installations (overlapping of protection zones), then the period for eliminating the malfunction is determined by the management of the operating organization.

4.8 FIELD CONTROL OF INSULATION AND CORROSION HAZARD OF PIPING

4.8.1 In all pits torn off during repair, reconstruction and elimination of insulation defects or corrosion damage to the pipeline, the corrosion state of the metal and the quality of the insulating coating should be determined.

4.8.2 If corrosion damage is detected on the existing pipeline, an examination is carried out in order to identify the cause of corrosion and develop anti-corrosion measures.

The form of the survey report is approved by the head of the facility operating the pipeline.

The act must reflect:

Year of commissioning of this pipeline section, pipeline diameter, wall thickness, laying depth;

Type and material of insulating coating;

Coating condition (presence of damage);

Thickness, contact resistance, coating adhesion;

Corrosive aggressiveness of soil;

The presence of a dangerous action of stray currents;

Information about the date of switching on the protection and data on the ECP outages that have taken place;

Measurement data of the polarization potential of the pipe and the potential of the pipe with the protection turned off;

The condition of the outer surface of the pipe near the site of damage, the presence and nature of corrosion products, the number and size of damage and their location along the perimeter of the pipe.

If a high corrosiveness of the soil or the dangerous action of stray currents is detected during a pit survey, the corrosiveness of the soil and the presence of a dangerous action of stray currents at a distance of about 50 m on both sides of the damage site along the pipeline route should be additionally determined.

The conclusion should indicate the cause of corrosion and suggest anti-corrosion measures.

A possible form of the act is given in Appendix III.

4.8.3 Determination of the hazardous effect of stray currents (according to clauses 4.2.16-4.2.24) in sections of pipelines that previously did not require ECP is carried out once every 2 years, as well as with each change in corrosion conditions.

4.8.4 Evaluation of the corrosiveness of soils (according to clauses 4.2.1-4.2.8) along the route of pipelines that previously did not require ECP is carried out once every 5 years, as well as with each change in corrosion conditions.

4.8.5 In sections of the pipeline where corrosion damage has occurred, after its elimination, it is advisable to provide for the installation of corrosion indicators (clause 4.3.11 and Appendix O).

APPS

Annex A

(Informative)

SCROLL

normative documents referred to in this manual

1. GOST 9.602-89*. Unified system of protection against corrosion and aging. Underground structures. General requirements for corrosion protection. Taking into account the ch. No. 1.

2. GOST R 51164-98. Main steel pipelines. General requirements for corrosion protection.

3. GOST 16336-77*. Polyethylene compositions for the cable industry. Specifications.

4. GOST 16337-77* E. High pressure polyethylene. Specifications.

5. GOST 9812-74. Oil bitumen. Methods for determining water saturation.

6. GOST 11506-73*. Oil bitumen. Method for determining the softening point by ring and ball.

7. GOST 11501-78*. Oil bitumen. Method for determining the depth of penetration of the needle.

8. GOST 11505-75*. Oil bitumen. Method for determining extensibility.

9. GOST 15836-79. Mastic bitumen-rubber insulating.

10. GOST 2678-94. Materials are rolled roofing and waterproofing. Test methods.

11. GOST 19907-83. Electrical insulating fabrics made of glass twisted complex yarns.

12. GOST 12.4.011-89. SSBT. Means of protection for workers. General requirements and classification.

13. GOST 6709-72. Distilled water.

14. GOST 19710-83E. Ethylene glycol. Specifications.

15. GOST 4165-78. Copper sulfate 5-water. Specifications.

16. GOST 5180-84. Soils. Methods for laboratory determination of physical characteristics.

17. GOST 6456-82. Grinding paper skin. Specifications.

18. Safety rules in the gas industry (PB 12-245-98). Moscow: NPO OBT, 1999

19. SNiP 11-01-95. Instructions on the procedure for the development, approval, approval and composition of project documentation for the construction of enterprises, buildings and structures.

20. Rules for the installation of electrical installations (PUE). 6th edition. M .: CJSC "Energo" ;, 2000

21. Rules for the operation of consumer electrical installations (PEEP) of Glavenergonadzor of Russia.

22. Safety regulations for the operation of consumer electrical installations (PTBEEP) of Glavenergonadzor of Russia.

23. TU 1394-001-05111644-96. Pipes steel with a two-layer covering from extruded polyethylene.

24. TU 1390-003-01284695-00. Pipes steel with an external covering from extruded polyethylene.

25. TU 1390-002-01284695-97. Pipes steel with an external covering from extruded polyethylene.

26. TU 1390-002-01297858-96. Steel pipes with a diameter of 89-530 mm with an external anti-corrosion coating made of extruded polyethylene.

27. TU 1390-003-00154341-98. Electric-welded and seamless steel pipes with an outer two-layer anti-corrosion coating based on extruded polyethylene.

28. TU 1390-005-01297858-98. Steel pipes with an outer two-layer protective coating based on extruded polyethylene.

29. TU RB 03289805.002-98. Steel pipes with a diameter of 57-530 mm with an outer two-layer coating based on extruded polyethylene.

30. TU 1394-002-47394390-99. Steel pipes with a diameter of 57 to 1220 mm coated with extruded polyethylene.

31. TU 1390-013-04001657-98. Pipes with a diameter of 57-530 mm with an external combined tape-polyethylene coating.

32. TU 1390-014-05111644-98. Pipes with a diameter of 57-530 mm with an external combined tape-polyethylene coating.

33. TU RB 03289805.001-97. Steel pipes with a diameter of 57-530 mm with an external combined tape-polyethylene coating.

34. TU 4859-001-11775856-95. Steel pipes coated with polymer adhesive tapes.

35. TU 2245-004-46541379-97. Tape heat-shrinkable two-layer radiation-modified ";DONRAD";.

36. TU 2245-002-31673075-97. Tape heat-shrinkable two-layer radiation-modified ";DRL";.

37. TU 2245-001-44271562-97. Tape protective heat-shrinkable "Terma";.

38. TU RB 03230835-005-98. Heat-shrinkable two-layer tapes.

39. TU 8390-002-46353927-99. Thermally bonded non-woven technical fabric.

40. TU 8390-007-05283280-96. Glued non-woven fabric for technical purposes.

41. TU 2245-003-1297859-99. Polyethylene tape for protection of oil and gas pipelines ";POLYLEN";.

42. TU 2245-004-1297859-99. Polyethylene wrapper for protection of oil and gas pipelines ";POLYLEN - OB";.

43. TU 38.105436-77 with Amend. No. 4. Rubber waterproofing sheet.

44. TU 2513-001-05111644-96. Bitumen-polymer mastic for insulating coatings of underground pipelines.

45. TU 2245-001-48312016-01. Polymer-bitumen tape based on Transkor mastic; - LITKOR.

46. ​​TU 2245-024-16802026-00. Tape LIAM-M (modified) for insulation of underground gas and oil pipelines.

47. TU 5775-002-32989231-99. Mastic bituminous and polymeric insulating ";Transkor";.

48. TU 204 RSFSR 1057-80. Protective bitumen-atactic coating against underground corrosion of steel gas and water networks and liquefied gas storage tanks.

7 Vladimir 2005 1 FOREWORD The purpose of the discipline "Automation of systems ... detection of hidden ( underground) leaks of external ... worn out gas pipelines. 9.13. Instructiononprotectionurbanpipelinesfromcorrosion. RD153 -39 .4-091 -01 9.14. GOST 9.602 ...

Corrosion has a detrimental effect on the technical condition of underground pipelines, under its influence the integrity of the gas pipeline is violated, cracks appear. To protect against such a process, electrochemical protection of the gas pipeline is used.

Corrosion of underground pipelines and means of protection against it

The condition of steel pipelines is influenced by soil moisture, its structure and chemical composition. The temperature of the gas conveyed through the pipes, currents straying in the ground caused by electrified transport and climatic conditions in general.

Types of corrosion:

• Surface. It spreads in a continuous layer over the surface of the product. Represents the least danger to the gas pipeline.
• Local. It manifests itself in the form of ulcers, cracks, spots. The most dangerous type of corrosion.
• Fatigue corrosion failure. The process of gradual accumulation of damage.

Methods of electrochemical protection against corrosion:

• passive method;
• active method.

The essence of the passive method of electrochemical protection is the application of a special protective layer to the surface of the gas pipeline, which prevents the harmful effects of the environment. This coverage could be:

• bitumen;
• polymer tape;
• coal tar pitch;
• epoxy resins.

In practice, it is rarely possible to apply an electrochemical coating evenly on a gas pipeline. In places of gaps, over time, the metal is still damaged.

The active method of electrochemical protection or the method of cathodic polarization is to create a negative potential on the surface of the pipeline, which prevents the leakage of electricity, thereby preventing the occurrence of corrosion.

The principle of operation of electrochemical protection

To protect the gas pipeline from corrosion, it is necessary to create a cathodic reaction and eliminate the anodic one. To do this, a negative potential is forcibly created on the protected pipeline.

Anode electrodes are placed in the ground, the negative pole of the external current source is connected directly to the cathode - the protected object. To close the electrical circuit, the positive pole of the current source is connected to the anode - an additional electrode installed in a common environment with the protected pipeline.

The anode in this electrical circuit performs the function of grounding. Due to the fact that the anode has a more positive potential than the metal object, its anodic dissolution occurs.

The corrosion process is suppressed under the influence of the negatively charged field of the protected object. With cathodic corrosion protection, the anode electrode will be subjected to the deterioration process directly.

To increase the service life of anodes, they are made of inert materials that are resistant to dissolution and other external influences.

An electrochemical protection station is a device that serves as a source of external current in a cathodic protection system. This unit is connected to the mains, 220 W and produces electricity with set output values.

The station is installed on the ground next to the gas pipeline. It must have a degree of protection of IP34 and above, as it works outdoors.

Cathodic protection stations may have different technical parameters and functional features.

Types of cathodic protection stations:

• transformer;
• inverter.

Transformer stations of electrochemical protection are gradually becoming a thing of the past. They are a construction of a transformer operating at a frequency of 50 Hz and a thyristor rectifier. The disadvantage of such devices is the non-sinusoidal form of the generated energy. As a result, a strong current ripple occurs at the output and its power decreases.

The inverter station of electrochemical protection has an advantage over the transformer one. Its principle is based on the operation of high-frequency pulse converters. A feature of inverter devices is the dependence of the size of the transformer unit on the frequency of current conversion. With a higher signal frequency, less cable is required, and heat losses are reduced. In inverter stations, thanks to smoothing filters, the ripple level of the produced current has a lower amplitude.

The electrical circuit that puts the cathodic protection station into operation looks like this: anode grounding - soil - insulation of the protected object.

When installing a corrosion protection station, the following parameters are taken into account:

• position of anode grounding (anode-ground);
• soil resistance;
• electrical conductivity of the insulation of the object.

Drainage protection installations for a gas pipeline

With the drainage method of electrochemical protection, a current source is not required, the gas pipeline communicates with the traction rails of railway transport using currents wandering in the ground. An electrical interconnection is carried out due to the potential difference between the railway rails and the gas pipeline.

By means of the drainage current, a displacement of the electric field of the gas pipeline located in the ground is created. The protective role in this design is played by fuses, as well as automatic overload switches with a return, which adjust the operation of the drainage circuit after a high voltage drop.

The system of polarized electrical drainage is carried out with the help of valve block connections. Voltage regulation with this installation is carried out by switching active resistors. If the method fails, more powerful electrical drains are used in the form of electrochemical protection, where a railway rail serves as an anode ground electrode.

Installations of galvanic electrochemical protection

The use of protective installations for the galvanic protection of the pipeline is justified if there is no voltage source near the object - power lines, or the gas pipeline section is not impressive enough in size.

Galvanic equipment serves to protect against corrosion:

• underground metal structures not connected by an electrical circuit to external current sources;
• individual unprotected parts of gas pipelines;
• parts of gas pipelines that are isolated from the current source;
• pipelines under construction, temporarily not connected to corrosion protection stations;
• other underground metal structures (piles, cartridges, tanks, supports, etc.).

Galvanic protection will work best in soils with electrical resistivity in the range of 50 ohms.

Plants with extended or distributed anodes

When using a corrosion protection transformer station, the current is distributed along a sinusoid. This adversely affects the protective electric field. There is either excess voltage at the place of protection, which entails a high consumption of electricity, or an uncontrolled leakage of current, which makes the electrochemical protection of the gas pipeline ineffective.

The practice of using extended or distributed anodes helps to circumvent the problem of uneven distribution of electricity. The inclusion of distributed anodes in the gas pipeline electrochemical protection scheme helps to increase the corrosion protection zone and smooth the voltage line. Anodes with this scheme are placed in the ground, throughout the entire gas pipeline.

Adjusting resistance or special equipment provides a change in current within the required limits, the voltage of the anode ground changes, with the help of which the protective potential of the object is regulated.

If several grounding conductors are used at once, the voltage of the protective object can be changed by changing the number of active anodes.

The ECP of a pipeline by means of protectors is based on the potential difference between the protector and the gas pipeline located in the ground. The soil in this case is an electrolyte; the metal is restored, and the body of the protector is destroyed.

Video: Protection against stray currents

6.8.1. Maintenance and repair of means of electrochemical protection of underground gas pipelines from corrosion, control over the efficiency of ECP and development of measures to prevent corrosion damage to gas pipelines are carried out by personnel of specialized structural divisions of operating organizations or specialized organizations.

6.8.2. The frequency of performance of work on maintenance, repair and verification of the efficiency of the ECP is established by PB 12-529. It is allowed to combine measurements of potentials when checking the efficiency of ECP with planned measurements of electrical potentials on gas pipelines in the coverage area of ​​ECP facilities.

6.8.3. Maintenance and repair of insulating flanges and ECP installations are carried out according to schedules approved in the prescribed manner by the technical management of organizations - owners of electrical protective installations. During the operation of ECP facilities, their failures in operation and downtime are recorded.

6.8.4. Maintenance of ECP cathode units includes:

Checking the condition of the protective ground loop (re-grounding of the neutral wire) and supply lines. An external inspection checks the reliability of the visible contact of the ground conductor with the body of the electrical protective installation, the absence of a break in the supply wires on the overhead line support and the reliability of the contact of the neutral wire with the body of the electrical protective installation;

Inspection of the condition of all elements of cathodic protection equipment in order to establish the serviceability of the fuses, the reliability of the contacts, the absence of traces of overheating and burns;

Cleaning equipment and contact devices from dust, dirt, snow, checking the presence and compliance of anchor marks, the condition of carpets and contact device wells;

Measurement of voltage, current value at the output of the converter, potential on the protected gas pipeline at the connection point with the electrochemical protection unit turned on and off. In case of discrepancy between the parameters of the electrical protective installation and the commissioning data, its operating mode should be adjusted;

Making appropriate entries in the operating log.

6.8.5. Maintenance of tread units includes:

Measurement of the tread potential relative to the ground with the tread off;

Measurement of the potential "gas pipeline-ground" with the protector on and off;

The value of the current in the circuit "protector - protected structure".

6.8.6. Maintenance of insulating flange joints includes cleaning the flanges from dust and dirt, measuring the potential difference "gas pipeline-ground" before and after the flange, voltage drop across the flange. In the zone of influence of stray currents, the measurement of the potential difference "gas pipeline-ground" before and after the flange should be performed synchronously.

6.8.7. The condition of adjustable and unregulated jumpers is checked by measuring the potential difference "structure-to-ground" at the jumper connection points (or at the nearest measuring points on underground structures), as well as by measuring the magnitude and direction of the current (on adjustable and detachable jumpers).

6.8.8. When checking the efficiency of the operation of electrochemical protection installations, in addition to the work performed during the technical inspection, the potentials are measured on the protected gas pipeline at reference points (at the boundaries of the protection zone) and at points located along the gas pipeline route, every 200 m in settlements and every 500 m on straight sections of inter-settlement gas pipelines.

6.8.9. The current repair of the ECP includes:

All types of technical inspection works with performance checks;

Measurement of insulation resistance of current-carrying parts;

Repair of the rectifier and other circuit elements;

Elimination of breaks in drainage lines.

6.8.10. The overhaul of ECP installations includes work related to the replacement of anode ground electrodes, drainage and supply lines.

After the overhaul, the main equipment of electrochemical protection is checked in operation under load for the time specified by the manufacturer, but not less than 24 hours.

9.11. The results of measurements of the first stage, taking into account measurements on adjacent communications, are analyzed and decisions are made to adjust the operating modes of protection installations.

9.12. If it is necessary to change the operating modes of the ECP, the measurements are repeated at all points located in the areas of protection installations with changed operating modes.

9.13. ECP operation modes can be adjusted repeatedly until the desired results are achieved.

9.14. Ultimately, the protective installations should be set to the minimum possible protective currents, at which the protected structures at all measurement points achieve protective potentials in absolute value not lower than the minimum allowable and not more than the maximum allowable.

9.15. The finally established modes of operation of protective installations must be agreed with all organizations that have underground structures in the areas of operation of the installations being adjusted, as they confirm in their conclusions (certificates).

9.16. In cases where during the commissioning work it is not possible to achieve the required protective potentials at all measurement points on the protected structures, the commissioning organization, together with the design and operating organizations, develops a list of necessary additional measures and sends it to the customer for taking appropriate measures.

9.17. Until the implementation of additional measures, the zone of effective protection of underground structures remains reduced.

9.18. The commissioning work is completed with the execution of a technical report on the commissioning of ECP units, which should include:

Full details about:

1) protected and adjacent underground structures;
2) active sources of stray currents;
3) criteria for corrosion hazard;
4) on the constructed and previously operating (if any) ECP installations;
5) electrical jumpers installed on the structures;
6) operating and newly constructed instrumentation;
7) electrically insulating connections;

Complete information about the work performed and its results;
- a table with the final parameters of operation of ECP units;
- a table of potentials of protected structures in the finally established operating modes of ECP installations;
- certificates (conclusions) of the owners of adjacent structures;
- conclusion on the adjustment of ECP installations;
- recommendations for additional measures to protect underground structures from corrosion.

10. Procedure for acceptance and commissioning of electrochemical protection installations

10.1. ECP units are put into operation after completion of commissioning and stability testing for 72 hours.

10.2. ECP units are commissioned by a commission, which includes representatives of the following organizations: customer; design (if necessary); construction; operational, to the balance of which the constructed ECP unit will be transferred; corrosion protection enterprises (protection services); bodies of Gosgortekhnadzor of Russia, bodies of Gosenergonadzor of Russia (if necessary); urban (rural) power networks.

10.3. The customer reports the data on checking the readiness of objects for delivery to the organizations that are part of the selection committee at least 24 hours in advance.

10.4. The customer submits to the selection committee: a project for the ECP device and the documents specified in Appendix U.

10.5. After reviewing the as-built documentation and the technical report on commissioning, the selection committee selectively checks the performance of the designed work - ECP facilities and assemblies, including insulating flange connections, control and measuring points, jumpers and other assemblies, as well as the efficiency of ECP installations. To do this, measure the electrical parameters of the installations and the potentials of the pipeline in sections where, in accordance with the project, the minimum and maximum protective potential are fixed, and when protecting only from stray currents, the absence of positive potentials is provided.
ECP installations that do not meet the design parameters should not be subject to acceptance.

10.6. The ECP unit is put into operation only after the acceptance certificate is signed by the commission.
If necessary, ECP can be accepted for temporary operation on an unfinished pipeline.
After the construction is completed, the ECP is subject to re-acceptance for permanent operation.

10.7. When accepting ECP on pipelines of channelless laying heating networks that have lain in the soil for more than 6 months, it is necessary to check their technical condition and, if there are damages, set the deadlines for their elimination.

10.8. Each accepted ECP installation is assigned a serial number and a special installation passport is entered into which all acceptance test data is entered (see Appendix F).

11. Operation of ECP units

11.1. The operational control of ECP installations includes periodic technical inspection, verification of the effectiveness of their work.
Each protective installation must have a control log in which the results of inspection and measurements are recorded (see Appendix X).

11.2. Maintenance of ECP units during operation should be carried out in accordance with the schedule of technical inspections and scheduled preventive repairs. The schedule of preventive inspections and scheduled preventive repairs should include the definition of the types and scope of technical inspections and repairs, the timing of their implementation, instructions on organizing accounting and reporting on the work performed.
The main purpose of preventive inspections and scheduled preventive repairs is to keep the ECP protection units in full working order, to prevent their premature wear and failures.

11.3. Technical inspection includes:

Inspection of all elements of the installation in order to identify external defects, check the density of contacts, serviceability of installation, the absence of mechanical damage to individual elements, the absence of burn marks and traces of overheating, the absence of excavations along the route of drainage cables and anode grounding;
- checking the serviceability of the fuses (if any);
- cleaning of the housing of the drainage and cathode converter, the unit of joint protection from the outside and inside;
- measurement of current and voltage at the converter output or between galvanic anodes (protectors) and pipes;
- measurement of the potential of the pipeline at the point of connection of the installation;
- production of an entry in the installation log about the results of the work performed.

11.4. Technical inspection with verification of the effectiveness of protection includes:

All technical inspection works;
- measurements of potentials in permanently fixed strong points.

11.5. Current repairs include:

All technical inspection work with performance verification;
- measurement of insulation resistance of supply cables;

RUSSIAN STATE UNIVERSITY OF OIL AND GAS IM. I.M. GUBKINA

TRAINING AND RESEARCH CENTER FOR EDUCATION OF EMPLOYEES OF THE FUEL AND ENERGY COMPLEX (FEC)

MUNTS "ANTIKOR"

Final work

under the program of short-term advanced training:

"CORROSION PROTECTION OF GAS AND OIL-FIELD EQUIPMENT, PIPELINES AND RESERVOIRS OF GAS AND OIL SERVICES"

Topic: Electrochemical protection systems, their operation

Moscow, 2012

Introduction

electrochemical corrosion protection grounding

Electrochemical protection of underground structures is a method of protection against electrochemical corrosion, the essence of which is to slow down the corrosion of a structure under the influence of cathodic polarization when the potential shifts to the negative region under the action of a direct current passing through the “structure - environment” interface. Electrochemical protection of underground structures can be carried out using cathodic protection installations (hereinafter referred to as CCP), drainage installations or tread installations.

When protected with the help of UKZ, a metal structure (gas pipeline, cable sheath, tank, well casing, etc.) is connected to the negative pole of a DC source. At the same time, an anode ground is connected to the positive pole of the source, which ensures the input of current into the ground.

With sacrificial protection, the protected structure is electrically connected to a metal that is in the same environment, but has a more negative potential than the potential of the structure.

With drainage protection, the protected structure, located in the area of ​​action of stray direct currents, is connected to a source of stray currents; this prevents these currents from flowing from the structure into the ground. Stray currents are leakage currents from rail tracks of electrified DC railways, tram tracks and other sources.

1. Cathodic protection installations

To protect underground pipelines from corrosion, cathodic protection units (CCP) are being built. The composition of the UKZ includes sources of power supply of the AC network 0.4; 6 or 10 kV, cathode stations (converters), anode grounding, control and measuring points (CIP), connecting wires and cables. If necessary, control resistors, shunts, polarized elements, control and diagnostic points (KDP), with corrosion monitoring sensors, remote control units and protection parameters adjustment units are included in the UKZ.

The structure to be protected is connected to the negative pole of the current source, the second electrode is connected to its positive pole - the anode ground electrode. The point of contact with the structure is called the drainage point. The principle scheme of the method can be represented as follows:

1 - direct current source

Protected structure

Drain point

Anode grounding

2. Overhead lines of cathodic protection installations

The operation of the overhead line consists in carrying out technical and operational maintenance, restoration and overhaul.

Maintenance of overhead lines consists of a set of measures aimed at protecting the elements of overhead lines from premature wear.

The overhaul of overhead lines consists in carrying out a set of measures to maintain and restore the initial operational indicators and parameters of overhead lines. During a major overhaul, defective parts and elements are replaced either with equivalent ones or with more durable ones that improve the operational characteristics of the overhead line.

Inspections along the entire route of the overhead line are carried out in order to visually check the condition of the overhead line. During inspections, the condition of supports, wires, traverses, insulators of arresters, disconnectors, attachments, bandages, clamps, numbering, posters, and the condition of routes are determined.

Unscheduled inspections are associated, as a rule, with a violation of the normal mode of operation or automatic disconnection of the overhead line from relay protection, and after a successful reconnection, they are carried out if necessary. Inspections are purposeful, they are carried out using special technical means of transportation and search for places of damage. They also detect malfunctions that threaten damage to overhead lines or people's safety.

A set of maintenance works for overhead lines 96 V - 10 kV.

3. Transformer substations above 1 kV

KTP refers to electrical installations with voltages above 1000 V.

Complete transformer substations used in UKZ with a capacity of 25-40 kVA are designed for receiving, converting and distributing electrical energy of three-phase alternating current with a frequency of 50 Hz.

A single transformer transformer substation consists of an input device on the high voltage side (UVN), a power transformer, and a switchgear on the low voltage side (RUNN).

During the operation of the PTS, reliable operation must be ensured. Loads, voltage level, temperature, transformer oil characteristics and insulation parameters must be within the established norms; cooling devices, voltage regulation, protection, oil facilities and other elements must be kept in good condition.

A sole inspection of the PTS can be performed by an employee who has a group of at least III, from among the operational personnel serving this electrical installation during working hours or on duty, or an employee from among the administrative and technical personnel who has group V and the right to a sole inspection on the basis of a written order the head of the organization.

4. Cathodic protection stations

Cathodic protection stations are subdivided into stations with thyristor and inverter type converters. Thyristor stations include stations of the PASK, OPS, UKZV-R types. Stations of the inventory type include stations of the type OPE, Parsek, NGK-IPKZ Euro.

Thyristor-type cathodic protection stations.

high reliability;

simplicity of design, which makes it possible to organize the repair of the station on the ground by the specialists of the ECP service.

The disadvantages of thyristor stations include:

low efficiency even at rated power,

The output current has unacceptably large ripples;

Large weight of stations;

Lack of power correctors;

a large amount of copper in the power transformer.

5. Inverter-type cathodic protection stations

The advantages of this type of station include:

high efficiency;

low output current ripple;

low weight (typical weight of a station with a power of 1 kW ~ 8 ... 12 kg);

compactness;

small amount of copper in the station;

high power factor (in the presence of a corrector, which is a mandatory requirement of GOST);

ease of quick replacement of the station (power converter) even by one person, especially when the station is modular.

The disadvantages include:

the lack of the possibility of repair in the workshops of the ECP services;

lower, compared to thyristor, station reliability, determined by a significantly greater complexity, a large number of components and the sensitivity of some of them to power surges during a thunderstorm and with an autonomous power supply system. Recently, a number of manufacturers have been supplying CPS with installed lightning protection units and voltage stabilizers, which significantly increases their reliability.

Maintenance of the transducer is carried out taking into account the requirements of the technical description and according to the maintenance schedule.

Routine maintenance is a system of scheduled preventive repairs, inspections and checks of the correct operation of ECP facilities. These works include the identification and elimination of malfunctions and defects, testing of instrumentation, accumulation and analysis of the obtained materials characterizing wear, as well as the performance of periodic repairs. The essence of the system of scheduled preventive repairs is that after the ECP means have worked out a given number of hours, a certain type of scheduled repair is carried out: current, or capital.

6. Current inspection (TO)

A set of works for the maintenance and control of the technical condition of all structural elements of ECP facilities available for external observation, carried out for preventive purposes.

During the current inspection of the SKZ, the following works are performed:

checking the readings of built-in electrical measuring instruments with control devices;

setting the instrument arrows to zero scale;

taking readings of voltmeters, ammeters, electricity consumption meter and converter operating time;

measuring and, if necessary, adjusting the potential of the structure at the point of drainage of the SCZ;

A record of the work carried out in the field log of the installation.

The current inspection is carried out by a bypass method throughout the entire period of operation of the ECP facilities between scheduled repairs.

7. Maintenance (TR)

Current repair - is carried out with a minimum amount of repair work. The purpose of the current repair is to ensure the normal operation of ECP facilities until the next scheduled repair by eliminating defects and through regulation.

During the current repair of the UKZ, all the work provided for by the technical:

Cleaning of detachable contacts and installation of connections;

removal of dust, sand, dirt and moisture from structural elements of circuit boards, coolers of power diodes, thyristors, transistors;

hauling of screw contact connections;

measurement or calculation of the resistance of the DC circuit of the UKZ;

a record of the work carried out in the field log of the installation.

8. Overhaul (KR)

The largest type of scheduled preventive maintenance in terms of the scope of work, in which individual components and parts are replaced or restored, disassembly and assembly, adjustment, testing and adjustment of ECP system equipment. Tests must show that the technical parameters of the equipment comply with the requirements stipulated by the regulatory and technical documentation (NTD).

The scope of KR of a cathodic protection station includes:

all medium repair works;

replacement of failed supports, struts, attachments;

hauling, and if necessary, replacement of wires, insulators, traverses, hooks;

replacement of defective blocks, switching equipment;

partial or complete replacement (if necessary) of anode and protective grounding;

inspection of the contact of the cathode cable with the protected structure.

9. Unscheduled repairs

An unscheduled repair is a repair not provided for by the PPR system, caused by a sudden failure associated with a violation of the rules of technical operation. A clear organization of the ECP service should ensure that such repairs are carried out as soon as possible. During the operation of the BPS, measures should be taken to minimize the possibility of the need for unscheduled repairs.

The work performed in the course of all scheduled preventive and unscheduled repairs is recorded in the relevant passports and logs for the operation and repair of electrochemical protection equipment.

10. Checkpoints

To monitor the state of integrated protection at underground structures, control and measuring points (CIP) should be equipped, on which the binding of the point of connection of the control wire to the structure is indicated.

The operation of control and measuring points (CIP) provides for maintenance and repairs (current and overhaul) aimed at ensuring their reliable operation. During maintenance, periodic inspections of instrumentation, preventive checks and measurements should be carried out, minor damage, malfunctions, etc. should be eliminated.

Control and measuring points (KIP) are installed on an underground structure after laying it in a trench before backfilling with earth. The installation of control and measuring points at existing facilities is carried out in special pits.

Control and measuring points are installed above the structure no further than 3 m from the point of connection to the structure of the control wire.

If the structure is located on a site where the operation of control and measuring points is difficult, the latter can be installed in the nearest places convenient for operation, but not further than 50 m from the point of connection of the control wire to the structure.

Control and measuring points on underground metal structures must ensure reliable electrical contact of the conductor with the protected structure; reliable insulation of the conductor from the ground; mechanical strength under external influences; lack of electrical contact between the reference electrode and the structure or control conductor; accessibility for service personnel and the possibility of measuring potentials regardless of seasonal conditions.

The current inspection of the instrumentation is carried out by a detour method throughout the entire period of operation of the ECP facilities between scheduled current repairs and during seasonal measurements of protective potentials by a team of workers consisting of at least two people. Before performing work at control and measuring points, it is necessary:

Carry out a gas measurement.

Determine the work area and mark it with appropriate safety signs.

During the current inspection of the instrumentation, the following types of work are performed:

External inspection of the instrumentation;

Checking the serviceability of the control output and outputs from the electrodes and sensors installed in the instrumentation;

Align the instrument perpendicular to the pipeline.

Measurement production

Carry out a measurement of gas contamination;

perform an external inspection of the instrumentation;

Determine the picket and the number of the protected structure on the identification plate;

Open the instrument lock and remove the cover;

get a device for measuring the protective potential;

make measurements on the terminal block of the instrumentation;

put on the instrument cover and close the locking device;

remove installed safety signs;

Continue moving along the protected structure to the next control and measurement point (CIP).

12. Maintenance (TR)

At the TR of control and measuring points, all preparatory work, current inspection work and the following types of work are performed:

Checking the serviceability of the control output and outputs from the electrodes and sensors installed in the instrumentation;

cleaning the locking devices of the column head covers;

lubrication of rubbing surfaces with CIATIM 202 grease.

coloring of control and measuring columns, racks of columns;

sodding or restoration of crushed stone blind areas;

renewal and (or) restoration of identification plates;

checking the insulation of control wires (optionally);

check of contacts of control conclusions with a pipe (selectively).

13. Overhaul (KR)

During the overhaul of instrumentation, damaged speakers, racks or posts are replaced, and the control cable is replaced.

When repairing control and measuring points, work must be performed in the following sequence:

carry out a measurement of gas contamination;

designate the work area with appropriate safety signs;

dig a pit to install a point;

open item cover;

if necessary, weld the control leads of the cable to the pipe;

insulate the place of welding, restore the heat-insulating coating of the pipeline;

stretch cables or wires into the cavity of the point post, providing for their reserve of 0.4 m;

install the rack in the pit vertically;

fill the pit with soil with compaction of the latter;

connect cables or wires to the terminals of the terminal block;

mark cables (wires) and terminals corresponding to the connection diagram;

close the item cover;

put on the top of the rack with oil paint the serial number of the point along the pipeline route;

fix the soil around the point within a radius of 1 m with a mixture of sand and crushed stone with a fraction of up to 30 mm;

remove the installed safety signs.

Prior to the installation of the control and measuring point, it is necessary to apply an anti-corrosion compound to its underground part, and paint the above-ground part in accordance with the corporate colors of Gazprom.

Anode grounding

According to the location relative to the ground surface, there are two types of grounding - surface and deep.

Like all technological installations, deep anode grounding (GAS) requires proper technical operation and timely maintenance.

Inspection of the state of the GAS, maintenance (tightening the contact of the drainage cable and painting the GAS), measuring the resistance and currents of the anode in order to determine the deviation of the spreading resistance is carried out once a year after the melt water converges and the soil dries out. The results are recorded in the VHC log and the VHC passport.

In the case of an increase in the GAS resistance (this can also be seen from the readings of the RMS ammeter or a decrease in potential at the drainage point), the protection zone decreases.

Maintenance, periodic measurements of GAS, registration of measurements in the field log book of the UKZ and analysis make it possible to provide a reliable protection zone for gas pipelines and predict further measures for the repair and restoration of GAS.

When operating a cathodic protection system for underground pipelines with deep anode ground electrodes (GAS), there is a problem of replacing them after the expiration of their service life. This process is complicated, and the costs are comparable to the installation of a new ground electrode system. The desire to maximize the use of the well has led to the fact that noble, slightly soluble metals are used for the grounding material, as a result of which their service life increases. However, the cost of building such GAS is much higher than that of ferrous metal ground electrodes. In recent years, intensive searches have been carried out for GAS of a replaceable design. Thus, an increase in the effectiveness of cathodic protection of any underground pipeline can be achieved by using insulating flanges or insulating inserts. At the same time, the use of insulating flanges gives the greatest technical and economic effect.

At present, extended flexible anodes (PGA) for cathodic protection (SC) of oilfield facilities are of great interest to provide an opportunity to reduce the cost of anti-corrosion protection of pipelines and oil and gas facilities.

The design feature of the anode units, for the protection of the VST, does not allow them to be placed horizontally on the bottom due to the possible blockage of the perforations of the dielectric shell by bottom sediments. Operation with a vertical arrangement of the anodes is allowed at a water phase level of at least 3 m and the presence of an emergency shutdown system of the RMS, at a lower level, sacrificial protection is used.

Technological efficiency of PHA application

In order to confirm the technical characteristics of ELER-5V CHAs declared by the manufacturer for protection against internal corrosion (IC) of capacitive equipment, the specialists of NGDU "NN" together with the TatNIPIneft Institute developed and approved programs and methods for bench and field testing of CHAs. Bench tests of samples of electrodes ELER-5V were carried out on the basis of TsAKZO NGDU "NN". Field tests were also carried out at the facilities of NGDU "NN": at BPS-2 TsDNG-5 (RVS-2000) and at UPVSN TsKPPN (horizontal settler GO-200).

In the course of bench tests (Fig. 1), the rates of anodic dissolution of the ELER-5V electrode in waste water were determined at values ​​of the maximum allowable linear current density and two times higher than it, and the effect of oil on the technical characteristics of the electrodes. It was found that after blocking the PHA surface with oil products, the electrodes are able to fully restore their performance (self-clean) after 6-15 days. Visual inspection of the outer surface of the samples participating in the study did not reveal any changes.

Bench tests confirmed the technical characteristics of PGA brand ELER-5V declared by the manufacturer.

In preparation for field testing, calculations of the ECP parameters of the internal surface of the VST and GO were performed. Taking into account the specifics of the CHA design, wiring diagrams (Fig. 2 and 3) were developed for their placement inside the capacitive equipment.

The calculated length of the electrode for GO-200 was 40 m, the distance between the “anode-bottom” surfaces was 0.7 m. The total protection current was 6 A, the output voltage of the cathodic protection station was 6 V, the power of the cathodic protection station was 1.2 kW .

The calculated length of the electrode for RVS-2000 was 115 m, the distance between the surfaces "anode-bottom" - 0.25 m, "anode-side surface" - 0.8 m. The total protection current - 20.5 A, the output voltage of the cathode station protection - 20 V, the power of the cathodic protection station - 0.6 kW.

The estimated service life for both options is 15 years.

In the process of testing on objects, the parameters at the output of the RMS were controlled and the current strength was adjusted. The potential shift measured on the steel measuring electrode ranged from 0.1 to 0.3 V.

According to the test certificate, specialists from the TatNIPIneft Institute and NGDU NN inspected the CCGT installed in the GO (200 m 3) at the UPVSN (Fig. 4). The operating time of the anode was 280 days. The results of the examination of the PHA showed his satisfactory condition.

16. Economic efficiency of PHA application

The design features and characteristics of the flexible anodes ELER-5V, according to the data of the Oil and Gas Production Department, made it possible to reduce the cost of equipping the HE in comparison with the sacrificial protection by 41%. In addition, with the introduction of ELER-5V anodes, a decrease in energy consumption for the protection of RVS by up to 16 times was noted. The power consumption for the protection of the VST of the NGDU "NN" was 0.03 kW (according to OAO "Tatneft" from 0.06 to 0.5 kW). According to the methodology for calculating the economic effect presented by NGDU NN, when introducing this type of anode, in comparison with the sacrificial protection, the economic effect will be 2.5 million rubles. (for the average annual output of HE for repair and cleaning at OAO TATNEFT). The total annual effect will be at least 6 million rubles.

Main conclusions:

The conducted bench and field tests of PHA at the facilities of NGDU "NN" showed their high efficiency in protecting capacitive equipment from internal corrosion (IC).

The use of CHA in OAO TATNEFT to protect capacitive equipment from VC by reducing the cost of construction and operation will provide an economic effect of at least 6 million rubles.

17. Tread protection

Under certain conditions, protection of underground structures from soil corrosion using protectors is effective and easy to operate.

One of the positive features of tread protection is its autonomy.

It can be carried out in areas where there are no sources of electricity.

Protective protection systems can be used as the main ECP:

When exercising temporary protection;

As a backup protection;

for potential equalization along the pipeline;

to protect transitions;

On short pipelines.

Protectors can have various shapes and sizes and are made in the form of individual castings or molds, rods, bracelet type (semi-rings), extended rods, wires and tapes.

The effectiveness of protective protection depends on:

Physical and chemical properties of the protector;

external factors that determine the mode of its use.

The main characteristics of protectors are:

electrode potential;

current output;

the efficiency of the tread alloy, on which the service life and optimal conditions for their use depend.

The design of the protectors should ensure reliable electrical contact of the protectors with the structure, which should not be disturbed during their installation and operation.

To make electrical contact between the protected structure and the protector, the latter must have reinforcement in the form of a strip or rod. The reinforcement is inserted into the tread material during the manufacture of the tread.

In Russia, when protecting underground metal structures from corrosion, protectors of the PMU type, which are magnesium anodes of the PM type, packed in paper bags with an activator, have found the greatest use.

In the center (along the longitudinal axis) of the PM protector there is a contact rod made of galvanized steel rod. A wire 3 m long is welded to the contact core. The junction of the conductor with the rod is carefully insulated. The stationary potential of magnesium protectors of the PMU type is -1.6 V relative to the m.s.e. The theoretical current output is 2200 A*h/kg.

In order to reduce spreading resistance and ensure stable operation, the protector is placed in a powdered activator, which is usually a mixture of bentonite (50%), gypsum (25%) and sodium sulfate (25%). The specific electrical resistance of the activator should be no more than 1 Ohm*m.

Gypsum prevents the formation of layers with poor conductivity on the surface of the tread, which contributes to uniform wear of the tread.

Bentonite (clay) is introduced to maintain moisture in the activator, in addition, clay slows down the dissolution of salts by groundwater, thereby maintaining a constant conductivity, and increases the service life of the activator.

Sodium sulphate gives readily soluble compounds with tread corrosion products, which ensures the constancy of its potential and a sharp decrease in the resistivity of the activator.

Under no circumstances should coke breeze be used as an activator for protectors.

After installing the protector in the ground, its current output is established within a few days.

The current output of the protectors significantly depends on the resistivity of the soil. The lower the electrical resistivity, the higher the current output of the protectors.

Therefore, protectors should be placed in places with a minimum specific resistance and below the level of soil freezing.

18. Drainage protection

A significant danger for main pipelines is the stray currents of electrified railways, which, in the absence of pipeline protection, cause intense corrosion damage in the anode zones.

Drainage protection - removal (drainage) of stray currents from the pipeline in order to reduce the rate of its electrochemical corrosion; ensures the maintenance of a stable protective potential on the pipeline (creation of a stable cathode<#"700621.files/image019.gif">

Schematic diagram of drainage protection:

Traction rail network;

Electrical drainage device;

Overload protection element;

Electric drainage current control element;

Polarized element - valve blocks assembled from several,

silicon avalanche diodes connected in parallel;

Protected underground structure.

Drainage protection is not used at our enterprises due to the absence of stray currents and electrified railways.

Bibliography

1. Backman V, Shvenk V. Cathodic corrosion protection: a Handbook. M.: Metallurgy, 1984. - 495 p.

Volkov B.L., Tesov N.I., Shuvanov V.V. Handbook on the protection of underground metal structures from corrosion. L .: Nedra, 1975. - 75s.

3. Dizenko E.I., Novoselov V.F. etc. Anticorrosive protection of pipelines and reservoirs. M.: Nedra, 1978. - 199 p.

Unified system of protection against corrosion and aging. Underground structures. General requirements for corrosion protection. GOST 9.602-89. M.: Publishing house of standards. 1991.

Zhuk N.P. Course of the theory of corrosion and protection of metals. M.: Metallurgy, 1976.-472 P.

Krasnoyarsky V.V. Electrochemical method of protecting metals from corrosion. Moscow: Mashgiz, 1961.

Krasnoyarsky V.V., Tzikerman L.Ya. Corrosion and protection of underground metal structures. Moscow: Higher school, 1968. - 296 p.

Tkachenko V.N. Electrochemical protection of pipeline networks. Volgograd: VolgGASA, 1997. - 312 p.