HG/T 20679-1990 Regulations for external corrosion protection design of chemical equipment and pipelines
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Industry Standard of the People's Republic of China
HG/T20679-1990
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External Corrosion Protection of Chemical Equipment and Pipelines
Design Provisions
19910201
1991-05-01 Implementation
Ministry of Chemical Industry of the People's Republic of China
1 General Principles -
2 Surface treatment for external corrosion protection of equipment, pipelines and steel structures 2.1 Surface treatment level
2.2 Requirements for surface treatment level of anti-corrosion coatings 2.3 Protection after surface treatment
External anti-corrosion coatings and markings for equipment, pipelines and steel structures 3
3.1 Classification of atmospheric corrosion degree on steel surface 3.2 Selection of anti-corrosion coatings
3.3 Equipment , pipelines and steel structure external surface painting and marking External corrosion protection of buried equipment and pipelines
4.1 General provisions
4.2 Classification of soil corrosion grades
4.3 Selection and structure of anti-corrosion layer
Appendix 1 Classification of corrosive gases
Characteristics of particulate matter in the atmosphere (including salts, aerosols and dust)Appendix 2
Appendix 3
Appendix 4
Appendix 5
Appendix 6
Appendix 7
Appendix 8
Appendix 9
Appendix 10
Examples of matching coatings...
Scope of high temperature, high pressure, flammable, explosive and toxic media Legend of pipeline coloring, color rings and flow direction markingsExamples of pipeline coloring, color rings and flow direction markingsBuried equipment and pipes Safety distance between the road and the AC grounding body and ground electrical equipment Soil corrosivity classification in areas with complex corrosion factors Quality indicators for anti-corrosion asphalt for pipelines
Quality indicators for No. 10 petroleum asphalt for construction
Appendix 11
Appendix 12
Appendix 13
Appendix 14
Appendix 15
Preparation instructions
Performance and specifications of medium-alkali glass cloth
Performance and specifications of polyvinyl chloride industrial film
Performance of polyethylene tape
Performance of primer for polyethylene tape anti-corrosion layer
Performance of chlorosulfonated polyethylene anti-corrosion layer
British Standard BS1710:1984 Marking of pipelines and auxiliary facilities (reference 1) Quality of external anti-corrosion technology for 1.8m steel pipe of Huangpu River upstream water diversion pipe Interim Provisions of the Standard (Reference 2) (1)
Industry Standard of the People's Republic of China
20013754
Design Provisions for External Corrosion Protection of Chemical Equipment and Pipelines HG/T20679-1990
Editor: Chemical Industry No. 2 Process Piping Design Technology Center Station, Ministry of Chemical Industry, Third Design Institute of Chemical Industry
Approval Unit: Ministry of Chemical Industry of the People's Republic of China Implementation Date: May 1, 1991
National Chemical Engineering Construction Standard Editing Center (formerly Chemical Engineering Construction Standard Editing Center) Beijing
According to the arrangement of the Infrastructure Department of the Ministry of Chemical Industry, the Chemical Industry Process Piping Design Technology Center Station, Ministry of Chemical Industry, organized the compilation of design standards and technical regulations for process piping as a ministry-level directive technical document to guide the design and manufacture of process piping. "Design Regulations for External Corrosion Protection of Chemical Equipment and Pipelines" (HG/T20679-1990) was compiled based on the summary of the experience in external corrosion protection design, construction and production of chemical engineering since the founding of the People's Republic of China, and with reference to relevant current standards at home and abroad. Its contents include general principles, surface treatment for external corrosion protection of equipment, pipelines and steel structures, external corrosion protection coatings and markings for equipment, pipelines and steel structures, external corrosion protection of buried equipment and pipelines, 15 appendices, two references and compilation instructions. This regulation was compiled by the Third Design Institute of the Ministry of Chemical Industry. The compilers were Comrades Zhang Yuehua, Sun Chuanchao, Fa Jiaqi, Chen Dehua, etc., and reviewed by Comrades Feng Shuyuan and Xia Dekai of the Chemical Process Piping Design Technology Center of the Ministry of Chemical Industry. In the process of implementing this regulation, if you find any modifications or supplements, please provide your opinions and relevant information to the Chemical Process Piping Design Technology Center of the Ministry of Chemical Industry for reference in future revisions. Chemical Process Piping Design Technology Center of the Ministry of Chemical Industry December 1990
1 General Principles
1.0.1 This regulation applies to the external corrosion protection of non-standard equipment, pipelines (including overhead, trench and buried laying) and steel structures (including platforms, brackets, railings, escalators, etc.) made of carbon steel, cast iron and low alloy steel. 1.0.2 The anti-corrosion methods specified in this regulation include non-metallic coatings and claddings, but do not include other anti-corrosion methods such as cathodic protection. 1.0.3 The coating and anti-corrosion design of the external surface of chemical equipment and pipelines shall be implemented in accordance with this regulation. During the engineering design, the designer shall select the scheme according to the specific situation (economic indicators, anti-corrosion effect, etc.). For new anti-corrosion materials and anti-corrosion structures, they must be proved to be effective through scientific experiments and practice or be identified by relevant departments before they can be selected. 1.0.4 All raw materials must meet the relevant standards or the relevant technical indicators of this regulation, and have factory certificates and inspection data. Materials should be used within the specified validity period, and expired materials must be inspected and qualified before they can be used. 1.0.5 Anti-corrosion construction must be carried out in accordance with the relevant national regulations and the construction instructions of the anti-corrosion material manufacturer. 2 Surface treatment of external corrosion protection of equipment, pipelines and steel structures 2.1 Surface treatment level
"St? or
2.1.1 The surface treatment level of equipment, pipelines and steel structures is represented by the letters "Sa", "Fl\, "Be\" indicating the rust removal method.
2.1.2 This regulation has four surface rust removal methods: (1) There are four quality levels of Sal, Sa2, Sa2-No., and -Sa3 for rust removal by spraying or projecting,
(2) There are two quality levels of St2 and St3 for rust removal by manual and power tools, (3) There is FI quality level for rust removal by flame; (4) There is Be quality level for chemical rust removal. 2.1.3 Rust removal by spraying or projecting
(1) Sa1 level: The surface of equipment, pipelines and steel structures should be free of Visible grease and dirt, and no loosely attached oxide scale, rust, paint and other attachments.
(2) Sa2 level: There should be no visible grease and dirt on the surface of equipment, pipelines and steel structures, and the oxide scale, rust and paint coatings and other attachments have been basically removed, and their residues should be firmly attached. (3) Sa2 level: There should be no visible grease, dirt, oxide scale, rust and oil 2
paint coatings and other attachments on the surface of equipment, pipelines and steel structures. Any remaining traces are only slight spots or stripes. (4) Sa3 level, there should be no visible grease, dirt, oxide scale, rust and paint coatings and other attachments on the surface of equipment, pipelines and steel structures, and the surface should show a uniform metallic color. 2.1.4 Manual and power tool rust removal
|(1) St2 level: There should be no visible grease and dirt on the surface of equipment, pipelines and steel structures, and no loosely attached oxide scale, rust and paint coating. (2) St3 level: There should be no visible grease and dirt on the surface of equipment, pipelines and steel structures, and no loosely attached oxide scale, rust and paint coating. Rust removal should be more thorough than St2, and the surface of the exposed part of the substrate should have a metallic luster. 2.1.5 Flame rust removal
(1) F1 level: There should be no oxide scale, rust and paint coating on the surface of equipment, pipelines and steel structures, and any remaining traces should only be surface discoloration (dark colors of different colors). 2.1.6 Chemical rust removal
(1) Be level: There should be no visible grease and oil stain on the surface of equipment, pipelines and steel structures, and pickling Individual residual spots of unfinished scale, rust and paint coating may be removed manually or mechanically, but in the end the surface should reveal the original metal appearance without re-rusting.
2.1.7 Before removing rust from the surface of equipment, channels and steel structures, thick rust layers and visible oil stains should be removed, and floating dust and debris on the metal surface should be removed after rust removal. 2.2 Requirements for surface treatment level of anti-corrosion coatings 2.2.1 The surface treatment level of equipment, pipelines and steel structures is related not only to the coating and primer used, but also to its own importance and the corrosive environment. For equipment, pipelines and steel structures that are critical, difficult to maintain, or susceptible to corrosion, the treatment level should be increased by one level according to the actual situation. 2.2.2 The surface treatment level required for commonly used anti-corrosion coatings can be specified in Table 2.2.2. Table 2.2,2
Coating categories
Resin
Ethylene
Polyurethane
Epoxy
·Asphalt
Raw lacquer or lacquer phenol
Organic silicon
Oil-based anti-rust
Alkyd, phenolic
Common anti-corrosion coatings require surface treatment levels Anti-corrosion coatings Sealing paint
Chlorosulfonated polyethylene corrosion paint, nitrided rubber primer Phosphate primer + pernitrogen primer, Ethylene paint primer Polyurethane Ester paint primer, various polyurethane modified paint primers Zinc-rich paint primer, various zinc-rich modified paint primers Various epoxy resin primers and their modified paint primers Acid-resistant asphalt primer
On-site primer (see Appendix 3)
Silicone paint primer
Red lead, iron red, boron barium and other anti-rust primers
Alkyd, phenolic resin primer and its modified paint primer, oil-based anti-rust paint primer Asphalt back paint When using oil-based anti-rust paint as primer, the surface treatment level is Sa2, F1 or St3. 2.2.3 The surface treatment level of buried equipment and pipelines is shown in Chapter 4. 2.3 Protection after surface treatment
2.3.1 A layer of primer should be applied in time after surface treatment, generally not more than 6 hours. 2
Surface treatment level
Sa2 level or Be level
Sa1 level or St2 level
2.3.2 If the equipment, pipelines and steel structures cannot be primed immediately after surface treatment, they should be properly protected to prevent rust and pollution again. If rust or dirty beams are found, the surface treatment should be repeated. 3 External anti-corrosion coatings and markings for equipment, pipelines and steel structures 3.1 Classification of the degree of corrosion of steel parts by the atmosphere 3.1:1 Corrosive substances in the atmosphere can be divided into corrosive gases, acid mist, particulate matter (including salt, aerosol, dust, etc.), dripping liquids, etc. Their corrosion on the surface of steel parts can be divided into three categories according to the degree of corrosion of corrosive gases, acid mist, particulate matter, and dripping liquids: strong corrosion, medium corrosion, and weak corrosion. The corrosion degree of corrosive gases, acid mist, particulate matter and dripping liquid in the atmosphere are shown in Tables 3.1.1-1, 3.1.1-2, 3.1.1-3 and 3.1.1-4 respectively.
Table 3.1.1-1
Relative humidity of air (%)
Table 3.1.1-2
Performance of acid mist
Weak acid and acid mist
Strong acid and acid mist
Corrosion degree of corrosive gases in the atmosphere
Gas category (continued in Appendix)
Corrosion degree of acid mist in the atmosphere
Effect evidence
Corrosion degree
Weak corrosion
Weak corrosion
Medium corrosion
Strong corrosion
Weak corrosion
Medium corrosion
Medium corrosion
Strong corrosion
Medium corrosion
Medium corrosion
Strong corrosion
Strong corrosion
Corrosion degree
Porridge corrosion
Medium corrosion
Medium corrosion
Strong corrosion
Note, "more" in the table means that acid mist appears frequently or periodically, and may condense on the metal surface. "Less" means that the acid mist is small and easy to diffuse, and cannot condense on the metal surface. 3
3.1.1-3
Relative humidity of air (%)
Degree of corrosion of particles in the atmosphere
Particularly good particles (according to Appendix 2)
Difficult to dissolve
Easily soluble, difficult to absorb moisture
Easily soluble, no moisture
Difficult to dissolve
Easily soluble, difficult to absorb moisture
Easily soluble, hygroscopic
Difficult to dissolve
Easily soluble, difficult to absorb moisture
Easy to dissolve, absorb moisture
Action
Corrosion degree
Weak corrosion
Chrysanthemum corrosion
Medium corrosion
Weak corrosion
Medium corrosion
Medium corrosion
Weak corrosion
Medium corrosion
Strong corrosion
Note: (1) The most "more" action means that the particles are concentrated or large in the air, and are not easy to spread, and often or periodically act. Accumulate or adhere to the surface of steel parts, which has a greater impact on the corrosion of steel parts. (2) When the amount of particles is small, the degree of corrosion is reduced by one level. 3.1.1-4
General organic liquids
Corrosion degree of decondensation liquids
Salt solution, industrial water (pH>3)
Corrosion degree of organic acid, inorganic acid solution, alkali solution, acidic water (pH>3)
Weak corrosion
Medium corrosion
Strong corrosion
3.1.2 When the atmosphere contains two or more of the above four types of corrosive substances, the atmospheric corrosion degree shall be the one with the highest corrosion degree. When the corrosion degrees of several types of corrosive substances are the same, the atmospheric corrosion degree shall be increased by one level. 3,1,3 For critical or difficult to maintain equipment and pipelines, the corrosion degree shall be increased by one level. 3.2 Selection of anticorrosive coatings
3.2.1 Selection of coatings
Comprehensively select according to the properties of the medium, environmental conditions, and the importance of the parts used in the project and the requirements for the coating performance to solidify into a film at room temperature.
3.2.2 The types of coatings selected according to the degree of corrosion are shown in Table 3.2.2-1 and Table 3.2.2-2. 3.2.3 Raw lacquer, lacquer phenol paint, phenolic paint and alkyd paint should not be used in alkaline environments. 3.2.4 Zinc coatings are suitable for marine atmospheres. In acidic and alkaline environments, they can only be used as primers. 3.2.5 Raw lacquer, lacquer phenol paint, phenolic paint and asphalt paint should not be used. 3.2.6 Primers, enamels, varnishes and topcoats that are well matched with each other should be used in combination. For examples of the matching and number of layers of corrosion-resistant coatings, please refer to Appendix 3. Table 3, 2.2-1
Strongly abrasive
Medium corrosion
·See 3.2.3~3.2.5.
Corrosion degree
Medium corrosion
Hamokan
Perfluoroethylene paint, polyurethane paint·, chlorosulfonated polyethylene paint, oxidized rubber material, raw lacquer, lacquer phenol paint·, epoxy resin paint
Epoxy resin paint, polyvinyl chloride paint, chlorosulfonated polyethylene paint, fluorinated rubber paint, nitrile paint (catalytic curing type), asphalt paint, phenolic resin paint epoxy asphalt paint phenolic resin paint, alkyd resin paint, oil-based paint, window zinc paint, asphalt paint Selection of high-temperature resistant paint
Temperature resistance,·C
300~450
3.2.7 See Table 3.2.7 for the thickness of the coating.
Degree of erosion
Strong corrosion
Medium corrosion
Weak corrosion
200220
120~150
Sulfonated polyethylene modified high temperature resistant coating
Organic silicon heat resistant coating
33 Color and marking degree of equipment, pipes and steel structure outer surface
220~250
150~200
100~150
3.3.1This regulation is formulated in reference to the national standard GB7231-87. Basic identification colors and identification symbols for industrial pipelines.
3.3.2 For new equipment expanded from old plants, this regulation should be referred to. For individual newly added equipment and pipelines, the coloring regulations for equipment, pipelines and steel structures can be specifically negotiated in combination with the type of the original coating of the old plant. 3.3.3 When the outer protective layer of the heat-insulating equipment and pipelines is made of ordinary iron sheet, glass cloth, asbestos cement and other materials, the coloring shall be carried out in accordance with these regulations.
3.3.4 For equipment and pipelines with high pressure, flammable or special indication, they shall be marked with words in obvious places. The scope of high temperature, high pressure, flammable, easy to dry and toxic media is shown in Appendix 4. 3.3.5 All ordered equipment or pipe fittings are required to be painted in accordance with these regulations (except for standard equipment). 3.3.6 Equipment color
(1) All kinds of static chemical equipment such as containers, towers, heat exchangers, storage tanks, etc. are painted silver white and sprayed with signs. 5
(2) All kinds of furnaces are painted black and sprayed with signs (3) Fire-fighting equipment is painted red and sprayed with signs. (4) All kinds of bacon are painted steel gray. For bacon with aviation requirements, the coloring shall be in accordance with relevant regulations (one section is red and the other section is white).
(5) If the outer sheath of the insulation equipment needs to be painted, it should be painted and marked as above. If the outer sheath of the insulation equipment does not need to be painted (see 3:3.7 (2) 3, a mark should be sprayed in a conspicuous position. (6) Marking: Use a color paint with a significant color difference from the main body, spray the equipment position number (code) or name, and the font must be correct.
3.3.77 Coloring of pipelines
(1-) In order to distinguish the types of media in the pipeline, the basic color of the outer surface of the pipeline is uniformly specified, see Table 3:3:7-1 In addition to the basic colors, different varieties of the same medium should also be given color rings and flow direction marks. The colors of the color rings and flow direction marks (same color) should be specified separately in the engineering design. The color rings should not be too complicated and are only allowed to be added to important pipelines, see Appendix V.
Table 3.3.7-#
Color regulations
Basic pipeline
Medium categories
Oil, flammable liquid
Other liquids
Gas (except air and oxygen)
Air, gas
Acids, alkalis
Original color
"Gray
Yellow brown
Light blue
(2) For carbon steel, cast iron, low alloy steel and insulated pipelines that need to be painted, the entire pipeline surface should be painted with the basic color. For stainless steel, non-ferrous metals, non-metals and insulated pipelines that do not need to be painted, the color ring should be painted with the basic color. Color rings and flow direction signs can be added for different types of media, see Appendix 5 and 6. (3) Basic color The color range and color samples, except for liquid materials and sewage pipes, are in accordance with the provisions of the national standard GB7231-87 "Identification colors and symbols for industrial pipelines". (4) The representation of color rings and flow direction marks is shown in Figure 3.3.7. (5) The specifications of color rings and flow direction marks are shown in Table 3.3.7-2. 3.3.72
Pipe outer diameter
50~150
150~300
Figure 3.3.7. Color rings and direction marks. Figure
Specifications of color rings and direction marks
Note, 1. When the pipeline is insulated, the outer diameter of the pipe refers to the outer diameter of the insulation layer. br
2. When using more than two color rings, the color ring spacing is equal to the color ring width. mm
The last set of color rings and flow 3. The location of the color ring and flow direction mark, except for the intersection of the pipe gallery, one group of color rings and flow direction marks are set every 6 to 10 meters for outdoor straight pipes, and one group of indoor pipes are set near elbows, valves, flanges or branches. 4. For pipelines that transport multiple media in one pipeline, the colors should be painted according to the media that are frequently transported. 5. Vent pipes that are not smokestacks should be painted according to the discharged media. 3.3.8 Steel structures such as platforms, brackets, supports, railings, escalators, etc. can generally be painted dark gray. External corrosion protection of buried equipment and pipelines
4.1 General provisions
4.1.1 The outer walls of all buried equipment and pipelines shall be coated with an anti-corrosion layer in accordance with these regulations. 4.1.2 Anti-corrosion layer used in the regulations (or covering layer) Cathodic protection measures are not considered. When adopting cathodic protection, the type and grade of the anti-corrosion layer should be reconsidered.
4.1.3 The outer anti-corrosion layer of buried equipment and pipelines should have the following properties: (1) Good electrical insulation. The resistance of the anti-corrosion layer should be greater than 10000Qm2, and the breakdown voltage strength should not be lower than the voltage standard detected by the spark detector.
(2) When there is cathodic protection, the anti-corrosion layer should have a certain ability to resist cathodic peeling strength. (3) Sufficient mechanical strength to ensure that the coating is not damaged under the pressure of transportation and earth filling. 7
(4) There should be good adhesion between the coating and the pipeline, and between the coatings, and the coating should have good permeability to the lining cloth. (5) Good impermeability and chemical stability. (6) Sufficient heat resistance to ensure that it does not deform at the operating temperature, and good low temperature resistance to ensure that it does not crack or fall off during stacking, transportation and construction at low temperatures. 4.1.4 After coating, the pipes should be wrapped with woven fabrics such as straw or cloth to prevent the coating from being damaged during transportation. The wrapping should be removed before burying.
4.1.5 The buried equipment and pipelines should be placed away from or far away from the AC ground body and other ground electrical equipment as much as possible. The safe distance between the buried equipment and pipelines and the AC ground body is shown in Appendix VII. 4.2 Classification of soil corrosion levels
4.2.1 For general areas, soil corrosivity is divided into sections according to soil resistivity or total acidity in the soil. Non-acidic soil is classified according to soil resistivity, and acidic soil is classified according to total acidity (see Table 4.2.1-1 and Table 4.2.1-2). For soil corrosivity classification in areas with complex corrosion factors, see Appendix VIII. Table 4.2.1-1
Corrosion degree
Soil fill resistivity (0.m)
Note: The soil fill resistivity adopts the annual minimum value. Table 4.2.1-2
Corrosion degree
Total acidity of soil (to pH=7)
(mval/kg)
Non-acid soil fill corrosion classification standard
Acid soil fill corrosion classification standard
4.2.2 Soil in general areas refers to soil with no or less sulfuric acid and other sulfides, and its main material is uniform. 4.2.3 When buried pipelines cross railways, highways, rivers, lakes, etc., regardless of the soil quality, special reinforced anti-corrosion coating grades should be used.
4,3 Selection and structure of anti-corrosion layer
4.3.1 The outer anti-corrosion layer of buried equipment and pipelines is divided into three levels: ordinary, reinforced, and special reinforced, and the corresponding three structures. Select the anti-corrosion layer structure according to the degree of soil corrosion, the performance of the anti-corrosion layer (petroleum asphalt, epoxy coal asphalt, polyethylene tape, nitrogen sulfonated polyethylene) and the importance of the anti-corrosion parts, see Table 4.3.1. 4.3.2. Petroleum asphalt anti-corrosion layer
(1) The type of asphalt used in the anti-corrosion layer is determined according to the temperature inside the pipeline or equipment: when the medium temperature is between 50 and 80°C, pipeline anti-corrosion asphalt should be used. The quality indicators of pipeline anti-corrosion asphalt should comply with the provisions of Appendix 9.
When the medium temperature is less than 50°C, No. 10 construction petroleum asphalt can be used, and its quality indicators should comply with the provisions of GB494-75 (see Appendix 10).
(2) The surface treatment level of the petroleum asphalt anti-corrosion layer before construction should meet the requirements of S2 level. :A83 The outer anti-corrosion layer of buried equipment and pipelines should have the following properties: (1) Good electrical insulation. The resistance of the anti-corrosion layer should be greater than 10000Qm2, and the breakdown voltage strength should not be lower than the voltage standard detected by the spark detector.
(2) When there is cathodic protection, the anti-corrosion layer should have a certain cathodic peeling strength resistance. (3) Sufficient mechanical strength to ensure that the coating is not damaged under the pressure of transportation and earth filling. 7
(4) There should be good adhesion between the coating and the pipeline, and between the coatings, and the coating has good permeability to the lining cloth. (5) Good impermeability and chemical stability. (6) Sufficient heat resistance to ensure that it will not deform at the operating temperature, and good low-temperature resistance to ensure that it will not crack or fall off during stacking, transportation and construction at low temperatures. 4.1.4 The coated pipeline should be wrapped with woven fabrics such as straw or cloth to prevent the coating from being damaged during transportation. The wrapping should be removed before burying.
4.1.5 The effective installation of buried equipment and pipelines should be avoided as far as possible or far away from the AC ground body and other ground electrical equipment. The safe distance between buried equipment and pipelines and the AC ground body is shown in Appendix VII. 4.2 Classification of soil corrosion levels
4.2.1 For general areas, soil corrosivity is divided into sections according to soil resistivity or total acidity in the soil. Non-acidic soil is classified according to soil resistivity, and acidic soil is classified according to total acidity (see Table 4.2.1-1 and Table 4.2.1-2). For soil corrosivity classification in areas with complex corrosion factors, see Appendix VIII. Table 4.2.1-1
Corrosion degree
Soil fill resistivity (0.m)
Note: The soil fill resistivity adopts the annual minimum value. Table 4.2.1-2
Corrosion degree
Total acidity of soil (to pH=7)
(mval/kg)
Non-acid soil fill corrosion classification standard
Acid soil fill corrosion classification standard
4.2.2 Soil in general areas refers to soil with no or less sulfuric acid and other sulfides, and its main material is uniform. 4.2.3 When buried pipelines cross railways, highways, rivers, lakes, etc., regardless of the soil quality, special reinforced anti-corrosion coating grades should be used.
4,3 Selection and structure of anti-corrosion layer
4.3.1 The outer anti-corrosion layer of buried equipment and pipelines is divided into three levels: ordinary, reinforced, and special reinforced, and the corresponding three structures. Select the anti-corrosion layer structure according to the degree of soil corrosion, the performance of the anti-corrosion layer (petroleum asphalt, epoxy coal asphalt, polyethylene tape, nitrogen sulfonated polyethylene) and the importance of the anti-corrosion parts, see Table 4.3.1. 4.3.2. Petroleum asphalt anti-corrosion layer
(1) The type of asphalt used in the anti-corrosion layer is determined according to the temperature inside the pipeline or equipment: when the medium temperature is between 50 and 80°C, pipeline anti-corrosion asphalt should be used. The quality indicators of pipeline anti-corrosion asphalt should comply with the provisions of Appendix 9.
When the medium temperature is less than 50°C, No. 10 construction petroleum asphalt can be used, and its quality indicators should comply with the provisions of GB494-75 (see Appendix 10).
(2) The surface treatment level of the petroleum asphalt anti-corrosion layer before construction should meet the requirements of S2 level. :A83 The outer anti-corrosion layer of buried equipment and pipelines should have the following properties: (1) Good electrical insulation. The resistance of the anti-corrosion layer should be greater than 10000Qm2, and the breakdown voltage strength should not be lower than the voltage standard detected by the spark detector.
(2) When there is cathodic protection, the anti-corrosion layer should have a certain cathodic peeling strength resistance. (3) Sufficient mechanical strength to ensure that the coating is not damaged under the pressure of transportation and earth filling. 7
(4) There should be good adhesion between the coating and the pipeline, and between the coatings, and the coating has good permeability to the lining cloth. (5) Good impermeability and chemical stability. (6) Sufficient heat resistance to ensure that it will not deform at the operating temperature, and good low-temperature resistance to ensure that it will not crack or fall off during stacking, transportation and construction at low temperatures. 4.1.4 The coated pipeline should be wrapped with woven fabrics such as straw or cloth to prevent the coating from being damaged during transportation. The wrapping should be removed before burying.
4.1.5 The effective installation of buried equipment and pipelines should be avoided as far as possible or far away from the AC ground body and other ground electrical equipment. The safe distance between buried equipment and pipelines and the AC ground body is shown in Appendix VII. 4.2 Classification of soil corrosion levels
4.2.1 For general areas, soil corrosivity is divided into sections according to soil resistivity or total acidity in the soil. Non-acidic soil is classified according to soil resistivity, and acidic soil is classified according to total acidity (see Table 4.2.1-1 and Table 4.2.1-2). For soil corrosivity classification in areas with complex corrosion factors, see Appendix VIII. Table 4.2.1-1
Corrosion degree
Soil fill resistivity (0.m)
Note: The soil fill resistivity adopts the annual minimum value. Table 4.2.1-2
Corrosion degree
Total acidity of soil (to pH=7)
(mval/kg)
Non-acid soil fill corrosion classification standard
Acid soil fill corrosion classification standard
4.2.2 Soil in general areas refers to soil with no or less sulfuric acid and other sulfides, and its main material is uniform. 4.2.3 When buried pipelines cross railways, highways, rivers, lakes, etc., regardless of the soil quality, special reinforced anti-corrosion coating grades should be used.
4,3 Selection and structure of anti-corrosion layer
4.3.1 The outer anti-corrosion layer of buried equipment and pipelines is divided into three levels: ordinary, reinforced, and special reinforced, and the corresponding three structures. Select the anti-corrosion layer structure according to the degree of soil corrosion, the performance of the anti-corrosion layer (petroleum asphalt, epoxy coal asphalt, polyethylene tape, nitrogen sulfonated polyethylene) and the importance of the anti-corrosion parts, see Table 4.3.1. 4.3.2. Petroleum asphalt anti-corrosion layer
(1) The type of asphalt used in the anti-corrosion layer is determined according to the temperature inside the pipeline or equipment: when the medium temperature is between 50 and 80°C, pipeline anti-corrosion asphalt should be used. The quality indicators of pipeline anti-corrosion asphalt should comply with the provisions of Appendix 9.
When the medium temperature is less than 50°C, No. 10 construction petroleum asphalt can be used, and its quality indicators should comply with the provisions of GB494-75 (see Appendix 10).
(2) The surface treatment level of the petroleum asphalt anti-corrosion layer before construction should meet the requirements of S2 level. :A8
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