GB/T 35508-2017 Regional cathodic protection in stations GB/T35508-2017 |tt||Standard compressed package decompression password: www.bzxz.net
This standard specifies the terms, definitions and abbreviations, requirements, criteria, design, construction and acceptance, operation, documentation and management of regional cathodic protection systems in stations. This standard applies to the regional cathodic protection of buried steel pipelines, equipment and the outer wall of the bottom of storage tanks in new or existing stations. The regional cathodic protection of other buried metal structures can be implemented as a reference.

ICS25.220.99
National Standard of the People's Republic of China
GB/T35508—2017
Regional cathodic protection within station
Regional cathodic protection within station Issued on 2017-12-29
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Administration of Standardization of the People's Republic of China
Implementation on 2018-07-01
Normative references
3 Terms, definitions and abbreviations
Terms and definitions
3.2 Abbreviations
4 Basic requirements
5 Protection criteria
General circumstances
Special considerationswww.bzxz.net
General requirements
Design of cathodic protection system
Electrical continuity
Electrical insulation
Auxiliary anode bed
Sacrificial anode
Cathode protection detection device
Anti-interference design
Construction and acceptance
General provisions
Installation of power supply equipment
Installation of auxiliary anode bed
Installation of sacrificial anode
Installation of power supply point...
Installation of voltage-equalizing line||tt ||Laying of cables
Installation of junction boxes
Installation of test equipment
Application and acceptance
Operation management
Documents and management
Corrosion control data
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GB/T35508—2017
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GB/T35508—2017
Design and construction documents and data
Data management
Appendix A (Normative Appendix)
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+.................+..........+.................Confirmation of the necessity of regional cathodic protection within the station 15
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This standard was drafted according to the rules given in GB/T1.1-2009. This standard is proposed by China Petroleum and Chemical Industry Federation. This standard is under the jurisdiction of National Anti-corrosion Standardization Technical Committee (SAC/TC381). GB/T35508—2017
The drafting units of this standard: Shenyang Zhongke Environmental Engineering Technology Development Co., Ltd., Beijing Bihaizhou Corrosion Protection Industry Co., Ltd., China International Anti-corrosion Technology Research Institute (Beijing) Co., Ltd., Sinopec Zhongyuan Oilfield Branch, Xiamen Yiliang Technology Co., Ltd., Luoyang Tyco Pipeline Technology Co., Ltd., China National Petroleum Corporation Tarim Oilfield Branch, Sinopec Northwest Oilfield Branch, Zhejiang Yuxi Corrosion Control Co., Ltd., Xi'an Titanium Industry Electrochemical Technology Co., Ltd., Sichuan Sihuan Pipeline Anti-corrosion Co., Ltd., China Industrial Anti-corrosion Technology Association. The main drafters of this standard are: Zang Hanyu, Peng Bo, Ding Baofeng, Wang Weidong, Zhao Haiyang, Gu Zhijun, Li Mingzhi, Meng Xiangjuan, Yang Dongming, Di Jianjun, Yang Chunyu, Wang Shutao, Zhang Jiangjiang, Wang Guiming, Huang Shaohua, Ou Rujie, Wan Li, Zhang Yuping, Fang Yuan, Wu AnmingiKAoNi KAca
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1 Scope
Regional cathodic protection within the station
GB/T35508—2017
This standard specifies the terms, definitions and abbreviations, requirements, criteria, design, construction and acceptance, operation, documentation and management of regional cathodic protection systems within the station
This standard applies to the regional cathodic protection of buried steel pipelines, equipment and the outer wall of the bottom of storage tanks in new or existing stations. The regional cathodic protection of other buried metal structures can be implemented as a reference. 2 Normative references
The following documents are indispensable for the application of this document. For dated references, only the dated versions apply to this document. For undated references, the latest versions (including all amendments) apply to this document. GB/T4950 Zinc-aluminum-cadmium alloy sacrificial anodes Basic terms and definitions for corrosion of metals and alloys GB/T10123
GB/T 17731
GB/T 21246
Magnesium alloy sacrificial anodes
Methods for measuring parameters of cathodic protection of buried steel pipelines GB/T21448-2008 Technical specification for cathodic protection of buried steel pipelines GB50021
GB50058
GB50393
Specification for geotechnical engineering investigation
Design specification for electrical installations in explosive atmospheres Technical specification for anti-corrosion engineering of steel petroleum storage tanks SY/T 0029
SY/T0086
Technical specification for application of buried steel inspection pieces
Electrical insulation standard for cathodic protection pipelines
SY/T0088—2016 Technical standard for cathodic protection of outer wall of steel storage tank bottomSY/T 0096
SY/T0516
SY/T 5919
Technical specification for forced current deep anode groundbed
Technical specification for insulating joints and insulating flanges
Technical management regulations for cathodic protection of buried steel pipelines 3 Terms, definitions and abbreviations
3.1 Terms and definitions
The terms and definitions defined in GB/T10123 and the following terms and definitions apply to this document. For ease of use, some terms and definitions in GB/T10123 are repeated below.
Regional cathodic protection
regional cathodic protection Cathodic protection that takes all protected objects in a certain area as a whole. 3.1.2
shielding
When there is an insulating structure or metal structure near the protected object of the station area cathodic protection, it will affect the flow of cathodic protection current. The phenomenon of hindering the cathodic protection current from flowing into the protected object or causing the cathodic protection current to deviate from the expected flow loop. 1
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GB/T35508—2017
Step voltage
stepvoltage
The electric field potential gradient formed by the auxiliary anode bed on the surface, that is, the change in surface potential per unit length 3.1.4
Feeding test
current requirementtes
A test to establish a direct current from the temporary auxiliary anode bed to the protected object to determine the protection current density value required for the protected object. 3.1.5
Drainpoint
The location where the protected body is electrically connected to the cathode cable. The protection current flows back to the negative pole of the DC power supply through this connection point. It is also called the confluence point or cathode power-on point. One or more drainpoints can be set in the cathodic protection system of each circuit. 3.1.6
Flexible anodeflexibleanode
The anode body is a cable-shaped auxiliary anode composed of linear and continuous anode materials. The anode material is located in the center of the coke filler wrapped by a fabric bag. The fabric bag is also tightly wrapped with a layer of wear-resistant woven mesh. 3.1.7
Mixed metal oxide anodemixedmetaloxideanodeA titanium-based anode material with a dense mixed metal oxide film sintered on the surface. Mixed metal oxides are generally a mixture of platinum group metal (Pt, Ir, Ru, etc.) oxides and valve metal (Ti, Ta, Nb, Zr, etc.) oxides. 3.1.8
Foreign structure
Metal structures outside the scope of regional cathodic protection. 3.2 Abbreviations
The following abbreviations apply to this document.
CSE: Copper/Copper Sulfate Reference Electrode SCC Stress Corrosion Cracking SRB: Sulfate-Reducing Bacteria HSE: Health, Safety and Environment MMO: Mixed Metal Oxide MMO/Ti: Mixed Metal Oxide Activated Ti Anodes 4 Basic requirements
4.1 When the corrosion of soil to steel structure is evaluated as strong corrosion level according to GB50021, the buried pipelines, equipment and outer wall of the bottom of the tank in the newly built station shall be protected by cathodic protection, and the buried pipelines, equipment and tanks in the existing station shall be supplemented with cathodic protection measures within a time limit and maintained during operation. When the corrosion evaluation is medium or weak corrosion level, cathodic protection should be adopted. The necessity of cathodic protection is confirmed in Appendix A.
4.2 The cathodic protection project of underground pipelines, equipment and the outer wall of the bottom of storage tanks in the newly built station should be surveyed, designed, constructed and put into operation simultaneously with the main project. When the cathodic protection system cannot be put into operation within 6 months of the pipeline and equipment being buried, temporary cathodic protection measures should be taken; in a highly corrosive soil environment, temporary cathodic protection measures should be added when the pipeline and equipment are buried underground until normal cathodic protection is put into operation. 4.3 The buried pipelines, equipment and the outer wall of the bottom of storage tanks in the newly built station should adopt the combined protection measures of anti-corrosion layer and cathodic protection, and they should be maintained during the operation of the station.
4.4 Potential test points should be set around the newly built storage tanks, and multiple long-term reference electrodes should be buried along the radius from the center point of the tank bottom to the tank periphery. The bottom potential of the built storage tank 2
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GB/T35508—2017
can be measured by setting a plastic pipe with holes at the bottom of the tank and using a portable reference electrode. The tank foundation should not be affected during construction.
4.5 The buried pipelines, equipment and storage tanks in the protection area should be electrically insulated from other metal structures unless the cathodic protection system integrates them and can provide them with sufficient protection current. 4.6 The design of the cathodic protection system should be coordinated with the design of the power grounding system and should be included in the cathodic protection scope. The grounding body of the buried pipelines, equipment and storage tanks that implement regional cathodic protection should not use materials with a more positive electrode potential series than the main material. 4.7 The cathodic protection of the outer wall of the bottom plate of the storage tank in the station area should comply with the provisions of GB50393 and SY/T0088. 5 Protection criteria
5.1 General situation
5.1.1 The cathodic protection potential of the pipeline (i.e. the polarization potential of the protected metal structure/ground interface, the same below) should be -850mV (CSE) or more negative. 5.1.2 The ultimate protection potential of the pipeline under cathodic protection cannot be more negative than -1200mV (CSE). 5.1.3 For high-strength steel (minimum yield strength greater than 550MPa) and corrosion-resistant alloy steel, such as martensitic stainless steel, duplex stainless steel, etc., the ultimate protection potential should be determined based on the actual hydrogen evolution potential. Its protection potential should be slightly more positive than -850mV (CSE), but in the potential range of -650mV to -750mV, the sensitive area of ​​high pH SCC in the pipeline should be paid attention to. 5.1.4 In the soil environment of oxic bacteria or SRB and other harmful bacteria, the cathodic protection potential of the pipeline should be -950mV (CSE) or more negative. 5.1.5 For pipelines in an environment with a soil resistivity of 100Ω·m to 1000Ω2·m, the cathodic protection potential should be negative -750mV (CSE); for pipelines in an environment with a soil resistivity greater than 1000Ω2·m, the cathodic protection potential should be negative -650mV (CSE). 5.2 Special considerations
When 5.1 cannot be achieved, the criterion of cathodic polarization or depolarization potential difference greater than 100mV can be used. Note: The 100mV polarization criterion cannot be used for pipelines under high temperature conditions, in the presence of stray current interference in the soil of SRB, and in coupling of dissimilar metal materials. 6 Design
6.1 General requirements
6.1.1 Design principles
6.1.1.1 It can provide a protective current that meets the cathodic protection criteria for the protected buried pipelines, equipment and storage tanks in the station and distribute it reasonably.
6.1.1.2 The regional cathodic protection in the station should be independent of the external system, and the interference of the external system and the underground metal structures in the non-protected area of ​​the station should be avoided or reduced to the greatest extent. 6.1.1.3 The design life of the cathodic protection system should take into account the matching of the design service life of the buried pipelines, equipment and storage tanks in the station. 6.1.1.4
The designed current should have a margin (about 20% of the required protection current). 5 The designed protection method, selected materials, installation location and installation requirements can meet the safe operation during the design life. 6.1.1.5
In order to test and evaluate the cathodic protection effect, complete testing facilities should be provided. 6.1.1.7
The cathodic protection system should meet the explosion-proof requirements in the station during installation and service. 3 The regional cathodic protection system should avoid the uncontrollable electrical noise in the instrumentation, communication system or information technology circuit. 6.1.1.8
6.1.2 Factors to be considered in design
The following factors should be considered in the design of the cathodic protection system: a) Confirm the safety requirements of the installation location of the cathodic protection system, the technical requirements of the selected materials, and the safe construction and operation and maintenance methods to ensure that the cathodic protection system can operate reliably and economically during its expected service life; when determining the location of the cathodic protection station, especially the location of the anode bed, the cathodic protection electrode should be b)
The interference with nearby metal structures is minimized: c)
Practical solutions should be proposed for areas with interference: For unfavorable conditions such as sulfides, bacteria, peeled anti-corrosion layers, insulation layers, high temperatures, shielding, acidic environments and the presence of foreign metals, investigations and studies should be conducted to propose solutions to the problems, avoiding excessive negative cathodic polarization potential, resulting in cathodic peeling of the anti-corrosion layer and over-protection that may damage high-strength steel due to hydrogen evolution; e
The cathodic protection station should be combined with the process site as much as possible. Basic data and on-site investigation
Basic data required for design
When designing a regional cathodic protection system, the following technical data are required: protection area plan and explosion-proof area division map; a
Distribution, type, quantity, basic parameters, construction date, corrosion history/current status, rectification and overhaul history and related b)
Drawings and data:
Design life of cathodic protection system;
Current density and protection current required to meet cathodic protection criteria: d)
Electrical continuity between protected objects, electrical insulation between protected objects and other surrounding metal structures; Anti-corrosion type/level and technical status of protected objects; Physical properties, temperature and pressure of the medium in the protected object; Lightning and static protection in the protection area Electrical grounding form, material and quantity: grounding form, material and quantity of machines, pumps, furnaces and other equipment in the protected area; type and quantity of other metal structures outside the protected area; layout of existing adjacent cathodic protection system and its operating parameters; k)
Other possible sources of electrical interference;
Natural potential of pipelines/ground, storage tanks/ground in the protected area; m)
Soil properties in the protected area, including soil resistivity, pH value and corrosion-causing bacteria; groundwater level, frost line depth, bedrock depth, topography and climatic conditions in the protected area; p
Available power supply sources;
Stray current interference and other relevant test data: r)
Design and completion documents of cathodic protection system for trunk pipelines outside the station and adjacent cathodic protection system. On-site survey
The on-site survey shall include the following items: a) test results, test location and method of soil resistivity at different depths in the anode bed area, protected body/ground potential, redox potential, soil pH value, etc. (see GB/T21246 for test methods); b) corrosion conditions of possible bacterial activity; c) specific parameters of AC and DC interference sources and their relationship with pipelines; non-compliance with construction technical specifications; d)
operating status of cathodic protection system and adjacent cathodic protection system of trunk pipeline outside the station; e)
6.1.3.1. The data collected in the project cannot meet the design requirements. f)
2 Cathodic protection system design
6.2.1 Protection method
6.2.1.1 Selection of protection method
GB/T35508—2017
Forced current cathodic protection is the main method for implementing regional cathodic protection for buried pipelines, equipment and storage tanks in the station. Sacrificial anodes can be used to supplement the forced current cathodic protection method. For stations with fewer buried pipelines and equipment and suitable geological conditions, forced anode cathodic protection can also be used alone.
Issues to be noted when designing the forced current mode The following issues should be noted when designing the forced current mode: a) Have a reliable power supply;
b) Do not cause interference corrosion to the surrounding metal structures and external trunk lines; c)
Reasonably select the location and burial method of the auxiliary anode bed: comply with explosion-proof safety regulations;
Different forms of anode beds should be used according to different geological conditions and the specific conditions of different sites; e
When using multiple groups of anode beds, the selection of control points should be conducive to the balanced discharge of each group of anodes , the working current of a single set of auxiliary anode ground bed should not be too large, and the step voltage formed on the ground should be ≤5V/m6.2.2 Calculation of cathodic protection current
The cathodic protection current is calculated according to formula (1):
Where:
The value of the total protection current in the area, in amperes (A); the value of the current margin, take 1.2;
The value of the surface area of ​​the protected structure, in square meters (m\); The value of the protection current density required for the design of the protected structure, in amperes per square meter (A/m\). Note: The protected structures include pipelines, equipment, storage tanks, grounding systems, steel bars in concrete, etc. ....(1
2 When the supports (piers) of equipment and overhead pipelines cannot be completely insulated from the ground, the calculated total protection current should be appropriately increased according to the specific situation.
6.2.2.2
6.2.2.3 The cathodic protection current demand of the station can be determined by the power feeding test. During the power feeding test, the temporary auxiliary anode bed should be laid with coke filler.
6.2.2.4 The value of the cathodic protection current density of the station should take into account the influence of the leakage current of the grounding system, or include the grounding system in the protection range.
6.2.2.5 For additional regional cathodic protection of existing projects, if there are no insulation facilities at the boundary of the limited protection range and insulation facilities cannot be installed, the current leakage caused by this should be fully considered during the design of cathodic protection and the capacity of the cathodic protection system should be appropriately increased.6.3 Electrical continuity
6.3.1 There should be good electrical continuity between the steel structures in the protection area. Electrical continuity. 6.3.2 Permanent jumpers should be installed between non-welded connected protected steel structures. 6.3.3 When protecting multiple parallel pipelines or multiple buried metal structures in the same protection area, a voltage equalizing line should be installed. 5
GB/T35508—2017
6.4 Electrical insulation
6.4.1 Electrical insulation devices include insulating joints, insulating flanges, insulating joints, insulating short pipes, insulating pipe joints, insulating sleeves, insulating gaskets, insulating supports, etc.
6.4.2 For abnormal conditions such as lightning strikes and overcurrents that may occur on the insulation device, surge protection devices should be used for protection. 6.4.3 The selection, installation, operation and maintenance of electrical insulation devices shall comply with the provisions of SY/T0086 and SY/T0516. The location where the electrical insulation device should be installed:
a) At the entrance and exit station;
b) The boundary between the pipelines, equipment and storage tanks in the protection area and the metal structures that do not require cathodic protection. 6.5 Power supply
6.5.1 Basic requirements
Basic requirements for AC power supply for forced current cathodic protection: a) Long-term uninterrupted power supply;
b) Priority should be given to using the mains or using stable and reliable AC power supply from various stations: c)
When the power supply is unreliable, a backup power supply or special equipment for uninterruptible power supply should be installed. 6.5.2 Power supply in areas without electricity
For areas without AC mains, DC power supplies such as solar cells, wind turbines, TEG, CCVT, etc. can be selected according to meteorological data and the medium to be transmitted.
6.5.3 Power supply equipment
Basic requirements
Basic requirements for forced current cathodic protection power supply equipment: High reliability:
Easy maintenance;
Long life:
Strong adaptability to the environment;
Adjustable output current and voltage;
With functions such as anti-overload, lightning protection, anti-interference, and fault protection; The instrument circuit board has been treated with moisture-proof treatment and can work for a long time in an environment with a humidity of ≤85%. Selection of power supply equipment
6.5.3.2.1
Principles for selecting power supply equipment
For forced current cathodic protection power supply equipment, rectifiers or constant potentiostats should generally be used. When the protected body/ground potential or loop resistance has frequent and large changes or the grid voltage changes greatly, a constant potentiostat should be used. 6.5.3.2.2 Matters to be noted when selecting power supply equipment When selecting power supply equipment, matters to be noted include: a) matching with the AC power connection;
b) type of rectifier or constant potentiostat;3 The selection, installation, operation and maintenance of electrical insulation devices shall comply with the provisions of SY/T0086 and SY/T0516. The locations where electrical insulation devices should be installed:
a) At the entrance and exit of the site;
b) The boundary between pipelines, equipment and storage tanks in the protection area and metal structures that do not require cathodic protection. 6.5 Power supply
6.5.1 Basic requirements
Basic requirements for forced current cathodic protection on AC power supply: a) Long-term uninterrupted power supply;
b) Priority should be given to using AC power or using stable and reliable AC power supply from various sites: c)
When the power supply is unreliable, a backup power supply or special equipment for uninterruptible power supply should be installed. 6.5.2 Power supply in areas without electricity
For areas without AC power, DC power supplies such as solar cells, wind turbines, TEG, CCVT, etc. can be selected according to meteorological data and the medium being transmitted.
6.5.3 Power supply equipment
Basic requirements
Basic requirements for forced current cathodic protection power supply equipment: High reliability:
Easy maintenance;
Long life:
Strong adaptability to the environment;
Adjustable output current and voltage;
With functions such as anti-overload, lightning protection, anti-interference, and fault protection; The instrument circuit board has been treated with moisture-proof treatment and can work for a long time in an environment with a humidity of ≤85%. Selection of power supply equipment
6.5.3.2.1
Principles for selecting power supply equipment
For forced current cathodic protection power supply equipment, rectifiers or constant potentiostats should generally be used. When the protected body/ground potential or loop resistance has frequent and large changes or the grid voltage changes greatly, a constant potentiostat should be used. 6.5.3.2.2 Matters to be noted when selecting power supply equipment When selecting power supply equipment, matters to be noted include: a) matching with the AC power connection;
b) type of rectifier or constant potentiostat;3 The selection, installation, operation and maintenance of electrical insulation devices shall comply with the provisions of SY/T0086 and SY/T0516. The locations where electrical insulation devices should be installed:
a) At the entrance and exit of the site;
b) The boundary between pipelines, equipment and storage tanks in the protection area and metal structures that do not require cathodic protection. 6.5 Power supply
6.5.1 Basic requirements
Basic requirements for forced current cathodic protection on AC power supply: a) Long-term uninterrupted power supply;
b) Priority should be given to using AC power or using stable and reliable AC power supply from various sites: c)
When the power supply is unreliable, a backup power supply or special equipment for uninterruptible power supply should be installed. 6.5.2 Power supply in areas without electricity
For areas without AC power, DC power supplies such as solar cells, wind turbines, TEG, CCVT, etc. can be selected according to meteorological data and the medium being transmitted.
6.5.3 Power supply equipment
Basic requirements
Basic requirements for forced current cathodic protection power supply equipment: High reliability:
Easy maintenance;
Long life:
Strong adaptability to the environment;
Adjustable output current and voltage;
With functions such as anti-overload, lightning protection, anti-interference, and fault protection; The instrument circuit board has been treated with moisture-proof treatment and can work for a long time in an environment with a humidity of ≤85%. Selection of power supply equipment
6.5.3.2.1
Principles for selecting power supply equipment
For forced current cathodic protection power supply equipment, rectifiers or constant potentiostats should generally be used. When the protected body/ground potential or loop resistance has frequent and large changes or the grid voltage changes greatly, a constant potentiostat should be used. 6.5.3.2.2 Matters to be noted when selecting power supply equipment When selecting power supply equipment, matters to be noted include: a) matching with the AC power connection;
b) type of rectifier or constant potentiostat;
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