1 Scope
This standard specifies the minimum technical requirements of extrusion on polyethylene coating by buried steel pipeline. This standard is applicable to the design, production as well as construction acceptance for the extrusion on polyethylene coating by buried steel pipeline. The extrusion of crossover pipeline on polyethylene coating may be implemented as a reference.
The extruding polyethylene coating may be divided into the normal temperature type (N) for long term work with the highest temperature not more than 50℃ and high temperature type (H) for long term work with the highest temperature not more than 70℃.
2 Normative References
The following documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated reference, subsequent corrections to (excluding correction to), or revisions of, any of these publications do not apply. However, all parties coming to an agreement according to this standard are encouraged to study whether the latest edition of these documents is applicable. For undated references, the latest edition of the normative document is applicable to these specifications.
GB/T 1040.2 Plastics - Determination of tensile properties - Part 2: Test conditions for moulding and extrusion plastics
GB/T 1408.1 Electrical strength of insulating materials - Test methods - Part 1: Tests at power frequencies
GB/T 1410 Methods of test for volume resistivity and surface resistivity of solid insulating materials
GB/T 1633 Plastics - Thermoplastic materials - Determination of Vicat softening temperature (VST)
GB/T 1842 Plastics - Test method for environmental stress-cracking of polyethylene
GB/T 2792 Determination method for peel strength of pressure-sensitive tape at 180° angle
GB/T 3682 Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics
GB/T 4507 STANDARD test method for softening point of bitumen （ring-and-ball apparatus)
GB/T 4472 General rule for 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 pourders 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 painting process
GB/ 8923 Rust grades and preparation grades of steel surfaces before application of paints and related products
GB/T 13021 Determination for the carbon black content of polyethylene pipes and fittings by calcination and pyrolysis
GB/T 18570.3 Preparation of steel substrates before application of paints and related products- Tests for the assessment of surface cleanliness - Part3: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 -- Part8: Field method for the conductometric determination of water-soluble salts
GB 50369 Code for construction and acceptance of oil & gas transmission pipeline engineering
GBJ 87 Specifications for the design of noise control system in industrial enterprises
GBZ 1 Hygienic Standards for the Design of Industrial Enterprises
HG/T 2751-1996 Determination for the water content of the un-plasticized cellulose acetate
3 Anticorrosive Coating Structure
3.1 The extruding polyethylene coating is divided into two kinds of two-layered structure and three-layered structure. The ground floor of the former is adhesive layer and its outer layer is polyethylene layer while the ground floor of the latter is usually powdered epoxy coating, its intermediate layer is adhesive layer and its outer layer is polyethylene layer.
3.2 The minimum thickness of anticorrosive coating shall be in accordance with those specified in Table 1. The thickness of anticorrosive coating at the position of welded joint shall not be less than 70% of the specified value in Table 1. The position with high mechanical strength requirements of anticorrosive coating shall adopt the strengthened Grade.
