Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 23257-2009 Polyethylene coating for buried steel pipeline. The following main technical changes have been made with respect to GB/T 23257-2009:
——The definition of the maximum temperature for the classification of extruded polyethylene coating in the clause “Scope” is adjusted, with the “maximum service temperature” adjusted as the “maximum design temperature” and the temperature adjusted from 50℃ to 60℃ and from 70℃ to 80℃ respectively (see clause 1);
——The clause “Terms and definitions” is added (see clause 3);
——The thermal characteristic index of epoxy powder coating is modified (see Table 2);
——The tensile performance requirements of special polyethylene material are modified (see Table 5);
——The performance requirements of polyethylene coating are supplemented and modified (see Table 7);
——The performance requirements of heat shrinkable tape joint coating materials are supplemented and modified (see Table 11);
——The requirements for joint coating construction preparation and joint coating procedure qualification are added (see 9.2);
——The test methods in some annexes are revised (see Annexes B and K);
——The test methods in annexes are added (see Annexes G, M and Q).
This standard was proposed by China National Petroleum Corporation.
This standard is under the jurisdiction of SAC/TC 355 National Technical Committee on Petroleum and Gas of Standardization Administration of China.
The previous edition of this standard is as follows:
——GB/T 23257-2009.
Polyethylene coating for buried steel pipeline
1 Scope
This standard specifies the minimum technical requirements for joint coating of extruded polyethylene coating and radiant crosslinked polyethylene heat shrinkable tape (sleeve) for steel pipeline.
This standard is applicable to the design, production and inspection of extruded polyethylene coating for buried steel pipeline and to the design, construction and inspection of the field joint coating. Reference may be made to this standard for the extruded polyethylene coating for pipelines of other laying forms.
The extruded polyethylene coating may be classified into two types, namely normal temperature type (N) with the maximum design temperature not exceeding 60℃ and high temperature type (H) with the maximum design temperature not exceeding 80℃.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 1040.2 Plastics - Determination of tensile properties - Part 2: Test conditions for moulding and extrusion plastics
GB/T 1408.1 Insulating materials - Test methods for electric strength - Part 1: Tests at power frequencies
GB/T 1410 Methods of test for volume resistivity and surface resistivity of solid electrical insulating materials
GB/T 1633 Plastics - Thermoplastic materials - Determination of Vicat softening temperature (VST)
GB/T 1725 Paints, varnishes and plastics - Determination of non-volatile-matter content
GB/T 1842 Plastics - Test method for environmental stress-cracking of polyethylene
GB/T 3682 Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics
GB/T 4472 Determination of density and relative density for chemical products
GB/T 5470 Plastics - Determination of the brittleness temperature by impact
GB 6514 Safety code for painting - Safety, ventilation and air clean-up for painting process
GB/T 6554 Resin based reactive compounds used for electrical insulation - Part 2: Methods of test - Methods for coating powders for electrical purposes
GB/T 7124 Adhesives - Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies
GB 7692 Safety code for painting - Safety, ventilation and air clean-up for pretreatment process of painting
GB/T 8923.1 Preparation of steel substrates before application of paints and related products - Visual assessment of surface cleanliness - Part 1: Rust grades and preparation grades of uncoated steel substrates and of steel substrates after overall removal of previous coatings
GB/T 13021 Determination for the carbon black content of polyethylene pipes and fittings by calcination and pyrolysis
GB/T 15332 Determination of the softening point of hot-melt adhesives - Ball and ring method
GB/T 18570.3 Preparation of steel substrates before application of paints and related products - Tests for the assessment of surface cleanliness - Part 3: Assessment of dust on steel surface prepared for painting (pressure-sensitive tape method)
GB/T 18570.9 Preparation of steel substrates before application of paints and related products - Tests for the assessment of surface cleanliness - Part 9: Field method for the conductometric determination of water-soluble salts
GB/T 50087 Specifications for the design of noise control system in industrial enterprises
GB 50369 Code for construction and acceptance of oil & gas transmission pipeline engineering
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
extruded polyethylene coating
anti-corrosive coating of polyethylene covered (longitudinal extrusion or lateral winding) on pipelines when the polyethylene in an extruder is heated and pressurized so as to continuously pass through an extrusion die in a flowing state
3.2
maximum design temperature
maximum temperature possibly reached by the anti-corrosive coating during pipeline transportation, handling, construction and operation
3.3
maximum operation temperature
maximum temperature reached by a pipeline or pipeline system during operation
Note: The maximum operation temperature shall not exceed the maximum design temperature.
3.4
low temperature applied epoxy powder coating
epoxy powder coating serving as the bottom layer of three-layer polyethylene coating specified in this standard and capable of being applied below 200℃
3.5
nominal tensile strain at break
nominal tensile strain corresponding to tensile stress at break
3.6
cohesive failure
adhesive layer breaking itself, with adhesive bonding on the surfaces of the two adherends
3.7
interfacial failure
visually visible damage occurred at the interface between adhesive layer and adherend
4 Anti-corrosive coating structure
4.1 The structure of extruded polyethylene coating is classified into two-layer structure and three-layer structure. For the two-layer structure, the bottom layer is an adhesive layer and the outer layer is a polyethylene layer; for the three-layer structure, the bottom layer is usually epoxy powder coating, the middle layer is adhesive layer, and the outer layer is polyethylene layer. Two-layer polyethylene coating should not be used for pipelines with the nominal diameter above DN500.
4.2 The minimum thickness of the anti-corrosive coating shall meet those specified in Table 1. The thickness of the anti-corrosive coating at the weld shall not be less than 80% of the value specified in Table 1. The grade of anti-corrosive coating shall be selected according to the pipeline construction environment and operation conditions.
Table 1 Anti-corrosive coating thickness
Nominal diameter of steel pipe
DN Epoxy coatinga
μm Adhesive layer
μm Minimum thickness of anti-corrosive coating
mm
General grade (G) Strengthened grade (S)
DN≤100 ≥120 ≥170 1.8 2.5
1001,200 3.3 4.2
a It is not applicable to two-layer polyethylene coating.
5 Materials
5.1 Steel pipes
5.1.1 The steel pipe shall meet the requirements of current relevant standards for steel pipes or the ordering technical conditions, and be provided with end-of-manufacturing certificate.
5.1.2 Steel pipes shall be subjected to appearance inspection piece by piece. The appearance quality shall meet those specified in current relevant standards or ordering technical conditions, and the anti-corrosive coating shall not be applied for rejected steel pipes.
5.2 Anti-corrosive coating material
5.2.1 General requirements
5.2.1.1 All kinds of raw materials of anti-corrosive coating shall be provided with end-of-manufacturing quality certificate, inspection report, operation instruction, safety data sheet, end-of-manufacturing certificate, production date and validity period. The supplier of epoxy powder coating shall provide the data like thermal characteristic curve of the product.
5.2.1.2 All kinds of raw materials of anti-corrosive coating shall be packed in good condition and stored according to the requirements of product instructions.
5.2.1.3 For the epoxy powder coating, adhesive and special polyethylene material of each grade (type), they shall be tested by the inspection agency passing the national metrological certification according to the corresponding performance items specified in 5.2 before use. Materials with the performance test results meeting the requirements specified in this standard may be used.
5.2.2 Epoxy powder coating
The performance of the epoxy powder coating and the coating shall meet the requirements specified in Tables 2 and 3. The coating factory shall reinspect the quality of each production batch of epoxy powder coatings (no more than 20 t) according to the requirements specified in Tables 2 and 3 (excluding 65℃, 30d cathodic disbonding), and Item 3 in Table 3 shall be reinspected irregularly. Where steel pipes have the requirements of being coated at low temperature, low temperature applied epoxy powder coating with its performance meeting the requirements specified in Tables 2 and 3 shall be adopted.
Forward i
1 Scope
2 Annex References
3 Terms and Definitions
4 Coating Structure
5 Materials
5.1 Steel Pipe
5.2 Anti-corrosion Material
5.3 Process Evaluation Test
6 Anti-corrosion Coating
7 Quality Inspection
8 Signs, Stacking and Handling
9 Repair Mouth and Injury
9.1 Filling Materials
9.2 Preparation for Construction
9.3 Filling Construction
9.4 Quality Inspection
9.5 Injuries
10 Back Ditch Backfill
11 Safety, Hygiene and Environmental Protection
12 Delivery Documents
Annex A (Annex) Epoxy Powder Curing Time Test Method
Annex B (Annex) Test Method for Thermal Properties of Epoxy Powder and Its Coating
Annex C (Annex) Coating Adhesion Method
Annex D (Annex) Anticorrosion Layer Cathode Peel Test Method
Annex E (Annex) Coating Anti-Bending Test Method
Annex F (Annex) Oxidation Induction Method
Annex G (Annex) Plastic Moisture Content Determination Test Method
Annex H (Annex) Indentation Hardness Test Method
Annex I (Annex) Polyethylene Resistant Chemical Medium Corrosion Test Method
Annex J (Annex ) Polyethylene UV Aging Resistance Test Method
Annex K (Annex Annex) Coating Peel Strength Measurement Method
Annex L (Annex ) Anticorrosion Layer Impact Strength Test Method
Annex M (Annex ) Polyethylene Anticorrosion Layer Hot Water Immersion Test Method
Annex N (Annex) Method for Thermal impact Test of Heat Shrinkable Tape (Sleeve)
Annex P (Annex) Heat Preservation Water Soak Test Method
Annex Q (Annex) Method for Thermal Aging Test of Filler Coating
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 23257-2009 Polyethylene coating for buried steel pipeline. The following main technical changes have been made with respect to GB/T 23257-2009:
——The definition of the maximum temperature for the classification of extruded polyethylene coating in the clause “Scope” is adjusted, with the “maximum service temperature” adjusted as the “maximum design temperature” and the temperature adjusted from 50℃ to 60℃ and from 70℃ to 80℃ respectively (see clause 1);
——The clause “Terms and definitions” is added (see clause 3);
——The thermal characteristic index of epoxy powder coating is modified (see Table 2);
——The tensile performance requirements of special polyethylene material are modified (see Table 5);
——The performance requirements of polyethylene coating are supplemented and modified (see Table 7);
——The performance requirements of heat shrinkable tape joint coating materials are supplemented and modified (see Table 11);
——The requirements for joint coating construction preparation and joint coating procedure qualification are added (see 9.2);
——The test methods in some annexes are revised (see Annexes B and K);
——The test methods in annexes are added (see Annexes G, M and Q).
This standard was proposed by China National Petroleum Corporation.
This standard is under the jurisdiction of SAC/TC 355 National Technical Committee on Petroleum and Gas of Standardization Administration of China.
The previous edition of this standard is as follows:
——GB/T 23257-2009.
Polyethylene coating for buried steel pipeline
1 Scope
This standard specifies the minimum technical requirements for joint coating of extruded polyethylene coating and radiant crosslinked polyethylene heat shrinkable tape (sleeve) for steel pipeline.
This standard is applicable to the design, production and inspection of extruded polyethylene coating for buried steel pipeline and to the design, construction and inspection of the field joint coating. Reference may be made to this standard for the extruded polyethylene coating for pipelines of other laying forms.
The extruded polyethylene coating may be classified into two types, namely normal temperature type (N) with the maximum design temperature not exceeding 60℃ and high temperature type (H) with the maximum design temperature not exceeding 80℃.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 1040.2 Plastics - Determination of tensile properties - Part 2: Test conditions for moulding and extrusion plastics
GB/T 1408.1 Insulating materials - Test methods for electric strength - Part 1: Tests at power frequencies
GB/T 1410 Methods of test for volume resistivity and surface resistivity of solid electrical insulating materials
GB/T 1633 Plastics - Thermoplastic materials - Determination of Vicat softening temperature (VST)
GB/T 1725 Paints, varnishes and plastics - Determination of non-volatile-matter content
GB/T 1842 Plastics - Test method for environmental stress-cracking of polyethylene
GB/T 3682 Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics
GB/T 4472 Determination of density and relative density for chemical products
GB/T 5470 Plastics - Determination of the brittleness temperature by impact
GB 6514 Safety code for painting - Safety, ventilation and air clean-up for painting process
GB/T 6554 Resin based reactive compounds used for electrical insulation - Part 2: Methods of test - Methods for coating powders for electrical purposes
GB/T 7124 Adhesives - Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies
GB 7692 Safety code for painting - Safety, ventilation and air clean-up for pretreatment process of painting
GB/T 8923.1 Preparation of steel substrates before application of paints and related products - Visual assessment of surface cleanliness - Part 1: Rust grades and preparation grades of uncoated steel substrates and of steel substrates after overall removal of previous coatings
GB/T 13021 Determination for the carbon black content of polyethylene pipes and fittings by calcination and pyrolysis
GB/T 15332 Determination of the softening point of hot-melt adhesives - Ball and ring method
GB/T 18570.3 Preparation of steel substrates before application of paints and related products - Tests for the assessment of surface cleanliness - Part 3: Assessment of dust on steel surface prepared for painting (pressure-sensitive tape method)
GB/T 18570.9 Preparation of steel substrates before application of paints and related products - Tests for the assessment of surface cleanliness - Part 9: Field method for the conductometric determination of water-soluble salts
GB/T 50087 Specifications for the design of noise control system in industrial enterprises
GB 50369 Code for construction and acceptance of oil & gas transmission pipeline engineering
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
extruded polyethylene coating
anti-corrosive coating of polyethylene covered (longitudinal extrusion or lateral winding) on pipelines when the polyethylene in an extruder is heated and pressurized so as to continuously pass through an extrusion die in a flowing state
3.2
maximum design temperature
maximum temperature possibly reached by the anti-corrosive coating during pipeline transportation, handling, construction and operation
3.3
maximum operation temperature
maximum temperature reached by a pipeline or pipeline system during operation
Note: The maximum operation temperature shall not exceed the maximum design temperature.
3.4
low temperature applied epoxy powder coating
epoxy powder coating serving as the bottom layer of three-layer polyethylene coating specified in this standard and capable of being applied below 200℃
3.5
nominal tensile strain at break
nominal tensile strain corresponding to tensile stress at break
3.6
cohesive failure
adhesive layer breaking itself, with adhesive bonding on the surfaces of the two adherends
3.7
interfacial failure
visually visible damage occurred at the interface between adhesive layer and adherend
4 Anti-corrosive coating structure
4.1 The structure of extruded polyethylene coating is classified into two-layer structure and three-layer structure. For the two-layer structure, the bottom layer is an adhesive layer and the outer layer is a polyethylene layer; for the three-layer structure, the bottom layer is usually epoxy powder coating, the middle layer is adhesive layer, and the outer layer is polyethylene layer. Two-layer polyethylene coating should not be used for pipelines with the nominal diameter above DN500.
4.2 The minimum thickness of the anti-corrosive coating shall meet those specified in Table 1. The thickness of the anti-corrosive coating at the weld shall not be less than 80% of the value specified in Table 1. The grade of anti-corrosive coating shall be selected according to the pipeline construction environment and operation conditions.
Table 1 Anti-corrosive coating thickness
Nominal diameter of steel pipe
DN Epoxy coatinga
μm Adhesive layer
μm Minimum thickness of anti-corrosive coating
mm
General grade (G) Strengthened grade (S)
DN≤100 ≥120 ≥170 1.8 2.5
1001,200 3.3 4.2
a It is not applicable to two-layer polyethylene coating.
5 Materials
5.1 Steel pipes
5.1.1 The steel pipe shall meet the requirements of current relevant standards for steel pipes or the ordering technical conditions, and be provided with end-of-manufacturing certificate.
5.1.2 Steel pipes shall be subjected to appearance inspection piece by piece. The appearance quality shall meet those specified in current relevant standards or ordering technical conditions, and the anti-corrosive coating shall not be applied for rejected steel pipes.
5.2 Anti-corrosive coating material
5.2.1 General requirements
5.2.1.1 All kinds of raw materials of anti-corrosive coating shall be provided with end-of-manufacturing quality certificate, inspection report, operation instruction, safety data sheet, end-of-manufacturing certificate, production date and validity period. The supplier of epoxy powder coating shall provide the data like thermal characteristic curve of the product.
5.2.1.2 All kinds of raw materials of anti-corrosive coating shall be packed in good condition and stored according to the requirements of product instructions.
5.2.1.3 For the epoxy powder coating, adhesive and special polyethylene material of each grade (type), they shall be tested by the inspection agency passing the national metrological certification according to the corresponding performance items specified in 5.2 before use. Materials with the performance test results meeting the requirements specified in this standard may be used.
5.2.2 Epoxy powder coating
The performance of the epoxy powder coating and the coating shall meet the requirements specified in Tables 2 and 3. The coating factory shall reinspect the quality of each production batch of epoxy powder coatings (no more than 20 t) according to the requirements specified in Tables 2 and 3 (excluding 65℃, 30d cathodic disbonding), and Item 3 in Table 3 shall be reinspected irregularly. Where steel pipes have the requirements of being coated at low temperature, low temperature applied epoxy powder coating with its performance meeting the requirements specified in Tables 2 and 3 shall be adopted.
Contents of GB/T 23257-2017
Forward i
1 Scope
2 Annex References
3 Terms and Definitions
4 Coating Structure
5 Materials
5.1 Steel Pipe
5.2 Anti-corrosion Material
5.3 Process Evaluation Test
6 Anti-corrosion Coating
7 Quality Inspection
8 Signs, Stacking and Handling
9 Repair Mouth and Injury
9.1 Filling Materials
9.2 Preparation for Construction
9.3 Filling Construction
9.4 Quality Inspection
9.5 Injuries
10 Back Ditch Backfill
11 Safety, Hygiene and Environmental Protection
12 Delivery Documents
Annex A (Annex) Epoxy Powder Curing Time Test Method
Annex B (Annex) Test Method for Thermal Properties of Epoxy Powder and Its Coating
Annex C (Annex) Coating Adhesion Method
Annex D (Annex) Anticorrosion Layer Cathode Peel Test Method
Annex E (Annex) Coating Anti-Bending Test Method
Annex F (Annex) Oxidation Induction Method
Annex G (Annex) Plastic Moisture Content Determination Test Method
Annex H (Annex) Indentation Hardness Test Method
Annex I (Annex) Polyethylene Resistant Chemical Medium Corrosion Test Method
Annex J (Annex ) Polyethylene UV Aging Resistance Test Method
Annex K (Annex Annex) Coating Peel Strength Measurement Method
Annex L (Annex ) Anticorrosion Layer Impact Strength Test Method
Annex M (Annex ) Polyethylene Anticorrosion Layer Hot Water Immersion Test Method
Annex N (Annex) Method for Thermal impact Test of Heat Shrinkable Tape (Sleeve)
Annex P (Annex) Heat Preservation Water Soak Test Method
Annex Q (Annex) Method for Thermal Aging Test of Filler Coating
