Technical standard for anti-corrosion engineering of steel petroleum storage tanks
1 General provisions
1.0.1 This standard is formulated to standardize the design, construction, acceptance, operation, maintenance and management of the anti-corrosion engineering of steel petroleum storage tanks (hereinafter referred to as "storage tanks") so as to ensure safety, environmental protection and economic rationality.
1.0.2 This standard is applicable to the anti-corrosion engineering of steel petroleum storage tanks.
1.0.3 In addition to this standard, the anti-corrosion engineering of steel petroleum storage tanks shall also comply with those stipulated in the relevant current national standards.
2 Terms
2.0.1 steel petroleum storage tanks
steel containers used for storing petroleum and petroleum products, i.e., the vertical cylindrical welded storage tanks in this standard
2.0.2 corrosion conditions
conditions causing corrosion of metal components of storage tanks
2.0.3 atmospheric corrosion
corrosion mainly caused by corrosive medium in the ambient atmosphere
2.0.4 immersed corrosion
corrosion mainly caused by medium in storage tank
2.0.5 owner
end user or user of the storage tank
2.0.6 designer
the organization completing the anti-corrosion design documents for storage tanks
2.0.7 constructor
the organization carrying out anti-corrosion construction of storage tanks
2.0.8 supplier
the organization providing materials necessary for anti-corrosion engineering of storage tanks
2.0.9 documents for anti-corrosion design
a generic term for documents of all processes such as confirmation of corrosion conditions, classification of corrosion grades, anti-corrosion measures, etc. for each part of the storage tank (hereinafter referred to as "design documents")
2.0.10 anti-corrosion engineering
a generic term for works such as anti-corrosion design, construction, quality inspection and acceptance of storage tanks
2.0.11 substrate
the surface of the base material to be coated
2.0.12 surface preparation
measures such as removing the attachments and oxides on the substrate surface or other measures for improving the surface roughness before coating
2.0.13 blasting
a method for cleaning and roughening the workpiece surface by the continuous impact of high-speed solid particle flow
2.0.14 abrasive
solid particles in the blasting medium
2.0.15 hydro-jet cleaning
a method for removing the attachments on the cleaned surface by continuous impact of high pressure water with outlet pressure of 70-170MPa or ultra-high pressure water with outlet pressure of more than 170MPa
2.0.16 mill scale
oxide film formed on the surface of steel during manufacturing or heat treatment
2.0.17 coating
protective layer coated on the metal surface to isolate the metal surface from the surrounding environment for anti-corrosion or decoration purpose
2.0.18 wet film thickness; WFT
thickness of uncured coating on the coated surface
2.0.19 dry film thickness; DFT
thickness of cured coating on the coated surface
2.0.20 volatile organic compound; VOC
any organic liquid or solid that may volatilize naturally at the atmospheric temperature and pressure
2.0.21 static conductive anticorrosion coating
anticorrosion coating having a surface resistivity within the range of 1×108~1×1011Ω
2.0.22 waterborne coating
coating with water as solvent or dispersion medium
2.0.23 solventfree coating
coating with the mass percentage of volatile solvent less than or equal to 2%
2.0.24 holiday
pinhole or holiday point on the surface of coating
2.0.25 surface resistivity
surface resistance per unit area, Ω
2.0.26 cathodic protection
method for controlling electrochemical corrosion by cathodic polarization, including sacrificial anode method and impressed current method
2.0.27 sacrificial anode
the electrode providing cathodic protection current to the protected object by its own corrosion
2.0.28 auxiliary anode
electrode directly connected to the anode of an external power supply under the impressed current cathodic protection to provide cathodic protection current to the protected object
2.0.29 linear anode
auxiliary anode of which the anode core material is pre-packaged with carbon powder and forms an integrated linear structure with it
2.0.30 grid-anode
auxiliary anode formed by vertical cross welding of mixed metallic oxide titanium and titanium connecting piece, which is embedded in the bottom of the storage tank in a grid shape
2.0.31 reference electrode
electrode having a stable open circuit potential and used as a reference when measuring a potential
2.0.32 backfill
material packed around the buried electrode to improve its working conditions
2.0.33 protective potential
potential necessary for the metal to reach effective protection
2.0.34 protective current density
current density necessary for the metal to reach effective protection
2.0.35 IR drop
voltage drop generated by the current on the electrolyte between the reference electrode and the protected facility
2.0.36 polarized potential
potential of storage tank to electrolyte measured without IR drop
2.0.37 on potential
potential of storage tank to electrolyte measured when powering on
2.0.38 instant-off potential
potential of storage tank to electrolyte measured upon power failure
2.0.39 open circuit potential
potential measured when the metal reaches a stable corrosion state without external current
2.0.40 test post
device arranged near the storage tank for measuring cathodic protection parameters
2.0.41 anti-corrosion construction plan
specific operation documents prepared for the anti-corrosion engineering construction according to the design requirements of the anti-corrosion construction organization, including the requirements of construction technology, resources, construction period, HSE and quality (hereinafter referred to as "construction plan")
2.0.42 anti-corrosion construction documents
a generic term for documents used to guide the engineering construction management and construction operations, such as the design, construction plan and construction operation instructions of the anti-corrosion construction organization (hereinafter referred to as "construction documents")
2.0.43 concealed work
part covered by the following procedure or procedure covered by the following operation
2.0.44 design life
expected safe service life of anti-corrosion engineering under set conditions, also known as expected durability
3 Basic requirements
3.1 Responsibilities
3.1.1 The owner shall provide the designer and the constructor with relevant data of the main engineering such as the structural size of the storage tank, storage medium and its components, and also provide the atmospheric data of the area where the storage tank is installed and the design life requirements of the anti-corrosion engineering of the storage tank.
3.1.2 The designer shall, determine the corrosion conditions and grades of each part of the storage tank according to the data provided by the owner, and complete the design documents of the storage tank on this basis. When data provided by the owner are incomplete, the designer shall communicate with the owner to obtain relevant data or form relevant documents according to the requirements of relevant standards, but the formed ones must be confirmed by the owner.
3.1.3 The constructor shall, according to the requirements of the design documents, prepare relevant construction documents and organize the implementation of the anti-corrosion engineering to ensure that the quality of the anti-corrosion engineering meets the requirements of the design documents.
3.1.4 The supplier shall, according to the requirements of the design documents, provide qualified materials and detailed construction instructions for the materials.
3.2 Design life of anti-corrosion engineering
3.2.1 The design life of the anti-corrosion engineering shall be specified by the owner in the contract.
3.2.2 Where not specified in the contract by the owner, the design life shall be determined according to the following principles, but shall be confirmed by the owner in writing:
1 the design life of parts not easy to be overhauled should be consistent with that of the main engineering;
2 the design life under immersed corrosion conditions shall not be lower than the overhaul period of the main engineering;
3 the design life of the coating, where used for protection, should not be less than 10 years;
4 the design life under atmospheric corrosion conditions may be considered as three grades, i.e., low (L), medium (M) and high (H); low (L) refers to a design life of 2-5 years, medium (M) refers to a design life of 5-15 years, and high (H) refers to a design life of more than 15 years;
5 the design life of impressed current cathodic protection should not be less than 20 years, while that of the sacrificial anode in tank should not be less than 10 years.
3.3 Corrosion grades
3.3.1 The atmospheric corrosion may be divided into four grades according to the uniform corrosion rate v1(mm/a) of the tank metal in the first year of exposure to atmospheric environment, which shall conform to the requirements of Table 3.3.1.
Table 3.3.1 Atmospheric corrosion grades
Corrosion grade Uniform corrosion rate v1(mm/a) Corrosion degree
I v1<0.025 No corrosion
II 0.025≤v1<0.050 Light corrosion
III 0.050≤v1<0.200 Moderate corrosion
IV v1≥0.200 Strong corrosion
3.3.2 The immersed corrosion may be divided into four grades according to the uniform corrosion rate v1(mm/a) and pitting corrosion rate v2(mm/a) of the tank metal by medium, which shall conform to the requirements of Table 3.3.2.
Table 3.3.2 Immersed corrosion grades
Corrosion grade Uniform corrosion rate
v1(mm/a) Pitting corrosion rate
v2(mm/a) Corrosion degree
I v1<0.025 v2<0.130 No corrosion
II 0.025≤v1<0.130 0.130≤v2<0.200 Light corrosion
III 0.130≤v1<0.250 0.200≤v2<0.380 Moderate corrosion
IV v1≥0.250 v2≥0.380 Strong corrosion
Note: the degree and grade of corrosion shall be determined based on the v1 or v2, which is worse.
3.4 Other requirements
3.4.1 The anti-corrosion engineering of storage tank shall be designed, constructed and put into service simultaneously with the main engineering.
3.4.2 In addition to the requirements of this standard, the construction of anti-corrosion engineering shall also meet the requirements of the design documents. Any design change or material substitution, if necessary, shall be confirmed in writing by the designer.
3.4.3 Materials adopted for anti-corrosion engineering shall be provided with product quality certification documents. The quality certification documents shall at least cover the following contents:
1 product quality certificate and material testing report;
2 technical indexes and testing method of quality.
3.4.4 The anti-corrosion engineering of storage tanks shall be accepted, and may only be put into service upon the expiration of curing period. Necessary protective measures should be taken for storage tanks when not used.
3.4.5 Relevant industrial hygiene, safety, labor protection and environmental protection involved in the anti-corrosion engineering shall conform to the current national standards GB 50160 Fire prevention code of petrochemical enterprise design, GB 7692 Safety code for painting - Safety, ventilation and air clean-up for pretreatment process of painting, GB 6514 Safety code for painting - Safety, ventilation and air clean-up for painting process, GBZ 1 Hygienic standards for the design of industrial enterprises, GB 50058 Code for design of electrical installations in explosive atmospheres and GB 7691 Safety code for painting - Safety management general rule.
4 Design
4.1 General requirements
4.1.1 The coating plan or the plan of combining coating and cathodic protection may be adopted as the anti-corrosion plan. Coating plan includes paint coating and metal coating.
4.1.2 For Grade I corrosion, the metal surface may not be protected against corrosion, while for corrosion of other grades, coating shall be protected against corrosion.
4.1.3 When the corrosion grade of the storage tank metal or the corrosion resistance of the anticorrosion coating cannot be determined, the anti-corrosion plan may be determined through test.
4.1.4 For the storage tanks in the area with strong soil corrosiveness or those of high importance, the external surface of the tank bottom should be subjected to the plan of combining coating and cathodic protection.
4.1.5 When the plan of combing sacrificial anode and coating is adopted, the surface resistivity of anticorrosion coating on the protected part shall not be less than 1×1013Ω.
4.1.6 The medium is flammable, explosive and prone to static charge accumulation during operation. In the absence of static conduction measures, light-color non-carbon static conductive anticorrosion coating with surface resistivity of 1×108~1×1011Ω shall be used for the anticorrosion coating exposed to the medium.
4.1.7 The anticorrosion coating applied inside the floating plate and buoyancy chamber shall be waterborne coating or solventfree coating.
4.1.8 When the plan of combining coating and cathodic protection is adopted, the cathodic disbonding resistance of the coating shall conform to the requirements of the current professional standard SY/T 0315 Technological standard of FBE external fusion bonded epoxy coating for steel pipeline.
4.1.9 The selection of anticorrosion coating shall:
1 be adapted to the surface material of the storage tank;
2 be adapted to the service environment and storage medium of the storage tank;
3 be adapted to the temperature of the metal surface of the storage tank;
4 be provided with good overcoatability and compatibility between each coating layers;
5 be provided with construction adaptability;
6 be safe, environmentally friendly and economically feasible.
4.2 Paint coating
4.2.1 The coating shall meet the following requirements:
1 solventfree, waterborne and high-solid coatings should be selected, in which the content of volatile organic compound (VOC) shall be less than 420g/L, and the performance of common coating shall meet the requirements of Annex A hereof;
2 the content of harmful heavy metals of lead (Pb), cadmium (Cd), hexavalent chromium (Cr6+) and mercury (Hg) shall meet the requirements of the current national standard GB 30981 Limit of harmful substances of anticorrosion coatings for construction steel structure.
3 the primer, intermediate paint, finish paint, curing agent, diluent, etc. shall be compatible with each other.
4.2.2 The anticorrosion coatings may be divided into alkyd, phenolic epoxy, epoxy, polyurethane, fluorocarbon, polysiloxane, etc. according to the film-forming resin.
4.2.3 Alkyd, acrylic polyurethane, fluorocarbon, polysiloxane, epoxy, epoxy zinc-rich coatings and other coatings may be used according to different coating performance and application temperature ranges under atmospheric conditions.
4.2.4 The anti-corrosion plan under atmospheric conditions shall meet the following requirements:
1 the weather-resistant coating shall be adopted on the surface of storage tank directly exposed to sunlight;
2 the anticorrosion coating under the thermal insulation layer of the storage tank may not be weather-resistant;
3 the reflective thermal insulation paint should be adopted for an-corrosion of storage tanks storing light oil products or volatile organic solvent media, with the total dry film thickness not be less than 250μm. The performance indexes of reflective thermal insulation paint and coating shall meet the requirements of Table A.0.14 hereof;
4 the corrosion grade of storage tanks in closed spaces such as caves shall be one grade higher than that of the corresponding atmospheric environment;
5 the phenolic coating and alkyd coating should not be used in alkaline environment;
6 the common anti-corrosion plan under different corrosion grades shall meet the requirements of Annex B hereof.
4.2.5 Glass flake, epoxy, phenolic epoxy, inorganic zinc-rich coatings and other coatings may be used according to different coating performance and application temperature ranges under immersed corrosion conditions.
Foreword i
1 General provisions
2 Terms
3 Basic requirements
3.1 Responsibilities
3.2 Design life of anti-corrosion engineering
3.3 Corrosion grades
3.4 Other requirements
4 Design
4.1 General requirements
4.2 Paint coating
4.3 Metallic coating
4.4 Annular plate protection
4.5 Cathodic protection
5 Construction
5.1 General requirements
5.2 Surface preparation
5.3 Paint coating
5.4 Metallic coating
5.5 Annular plate protection
5.6 Cathodic protection
5.7 Process inspection and construction quality control
6 Acceptance
7 Operation and maintenance
7.1 General requirements
7.2 Coating
7.3 Cathodic protection
Annex A Performance index of common paint
Annex B Common anti-corrosion plan under different grades
Annex C Common anti-corrosion plan for petroleum storage tanks under immersion conditions
Annex D Cathodic protection
Annex E Test for cathodic protection potential
Annex F Abrasive and surface preparation
Annex G Dew temperature table
Annex H Rules and methods of coating quality inspection
Explanation of wording in this standard
List of quoted standards
