QCNPC-GD-0291 solvent-free liquid epoxy anti-corrosion steel pipe

QCNPC-GD 0291-2006 is an enterprise standard issued by the China Petroleum Pipeline Bureau, officially known as the "Technical Specification for Solvent free Liquid Epoxy Coating for Buried Steel Pipelines". The standard was released and implemented on March 1, 2006.

scope of application

This standard specifies the requirements for solvent-free liquid epoxy external anti-corrosion coating for buried steel pipelines, applicable to buried steel pipelines transporting crude oil, refined oil, natural gas, and water. In addition, when solvent-free epoxy anti-corrosion coating is used for steel storage tanks, ships, steel structures and other facilities, it can also be followed. The long-term working temperature of solvent-free liquid epoxy anti-corrosion coating should usually not exceed 80 ℃, unless otherwise specified by the coating manufacturer. At the same time, the design, construction, and acceptance of solvent-free liquid epoxy anti-corrosion coatings for buried steel pipelines shall comply with the relevant national standards (specifications) in addition to this standard.

Grade and requirements of anti-corrosion coating

Grade dry film thickness

Ordinary grade ≥ 0.4mm

Enhancement level ≥ 0.55mm

If requested by the user, the thickness of the anti-corrosion coating can also be increased.

Material requirements

Solvent free liquid epoxy coating

Basic characteristics: Solvent free liquid epoxy coating does not contain volatile solvents and is a two-component, chemically cured epoxy coating.

Performance indicators: Its performance indicators must comply with the relevant table regulations, such as color and appearance requirements, uniform color, and light; Fineness ≤ 85 μ m; Solid content ≥ 95%, etc. Specific reference can be made to Table 3 Coating Technical Indicators and Table 4 Coating Performance Indicators in the standard.

Sampling regulations: Each batch of paint must be sampled and comply with relevant regulations. When a batch of paint exceeds 20 tons, a sampling inspection shall be conducted every 20 tons of paint. When there are no significant changes in the raw materials and formula of the coating, the factory inspection shall be carried out according to the provisions of items 1, 2, and 3 in Table 4 and Table 3. At the same time, paint manufacturers also need to provide evidence related to the temperature at which the paint is used.

Material acceptance

Marking and certification documents: Coatings should have complete product markings including name, factory name, batch number, production date, shelf life, etc. The coating manufacturer should provide product instructions, testing reports, and quality certificates, otherwise they should be rejected.

Instruction manual content: The content of the coating instruction manual should cover the technical indicators of the coating, the proportion of each component, the applicable period of the coating after preparation, the application and use methods, the reference dosage, and the precautions for transportation and storage.

Re inspection regulations: Each batch of paint should be re inspected according to items 1, 2, 3, 4, 5, and 6 in Table 4 and the regulations in Table 3. When there is doubt about the quality, testing should be carried out according to Tables 3 and 4. If it is not qualified, it should be re sampled and the number of samples should be doubled. If it is still unqualified, the batch of paint is unqualified and should be rejected. Sampling inspection must be conducted in a nationally recognized laboratory.

Storage and use: Users should store according to the conditions required in the product manual and use within the shelf life. Coatings that have exceeded their shelf life should be rechecked according to relevant regulations, but the number of samples should be doubled. Only when they meet the requirements can they be used. When necessary, a water immersion test of 2400 hours should be conducted on the coating at the recommended operating temperature. The coating is considered qualified if it has bubbles, no cracking, and no rust to verify its temperature resistance performance.

Construction requirements for anti-corrosion coating application

Surface pretreatment of steel pipes

Appearance inspection and cleaning: Steel pipes should be visually inspected one by one, and the surface of the steel pipes should not contain grease or dirt. If there is any, appropriate methods should be used to clean the surface of the steel pipes.

Rust removal treatment: According to the spray (polishing) rust removal method and abrasive requirements specified in SY/T0407, the surface of the steel pipe shall be sprayed (polished) for rust removal. The requirement for surface treatment of steel pipes should reach Sa2.5 level, and the depth of anchor lines should be between 50 μ m and 75 μ m.

Surface cleaning and weld treatment: After surface treatment of steel pipes, the dust on their surface should be removed completely. The weld seam should be treated to be free of weld beads, edges, and burrs.

Coating time and environmental requirements: Steel pipes with qualified surface pretreatment should be coated before rusting or within 4 hours, otherwise surface pretreatment should be carried out again. During construction, the surface temperature of the steel should be at least 3 ℃ higher than the dew point, and the relative humidity of the air should be below 85%.