SY/T 0447 Epoxy Coal Tar Anti Corrosion Steel Pipe

SY/T0447-2014 is a technical standard for epoxy coal tar anti-corrosion coating of buried steel pipelines, which is applicable to the anti-corrosion design, construction and inspection of the outer wall of buried steel pipelines with a conveying medium temperature not exceeding 80 ℃. This standard specifies the grade, structure, material selection, construction process, and inspection requirements of the anti-corrosion coating, and emphasizes the need to implement them in conjunction with the current relevant national standards. The small thickness of ordinary and reinforced anti-corrosion coatings is ≥ 400 μ m and ≥ 600 μ m, respectively. Reinforced coatings can be reinforced by wrapping polypropylene non-woven fabric or glass cloth.

Anti corrosion coating materials and construction requirements

Epoxy coal tar coating consists of two components: A (resin and additives) and B (curing agent), which need to be provided by the same supplier and formulated according to the ratio determined by the manufacturer. The surface treatment of steel pipes must reach Sa2 level (sandblasting) or St3 level (tool rust removal), and visual inspection must be carried out before coating. Unqualified steel pipes cannot be constructed. Fiber reinforced materials must meet the requirements for chemical resistance and physical and mechanical properties specified in the standards.

Inspection and Quality Control of Anti corrosion Coating

The inspection of anti-corrosion coating includes visual inspection (no defects such as sagging or wrinkles), thickness measurement (magnetic thickness gauge), leak detection (electric spark leak detector), and adhesion testing (pull or scratch method). The voltage for leak point inspection is adjusted according to the thickness of the anti-corrosion layer, with a normal level of 2000V and a reinforced level of 5000V. The adhesive strength requirement is that the ordinary grade should be ≥ 3MPa, and the reinforced grade should be ≥ 5MPa. During the construction process, it is necessary to record data from each stage for traceability.

Main updates of SY/T0447-2014

Compared to the 1996 version, the 2014 version of the standard has expanded its scope of application (clarifying that the medium temperature is ≤ 80 ℃), removed the special reinforcement structure, and added solvent-free epoxy coal tar coating and polypropylene non-woven fabric as fiber reinforcement materials. At the same time, a test method for bonding strength after hot water immersion has been added, strengthening the requirements for health, safety, and environmental protection.

Application Scenarios and Engineering Practice

Epoxy coal tar anti-corrosion steel pipes are widely used for buried oil, gas, water, and heating pipelines, as well as for anti-corrosion of steel structures such as docks, ships, and storage tanks. Practical engineering has shown that this anti-corrosion layer has the advantages of high pressure resistance and resistance to microbial erosion in oilfield gathering and transportation systems, but it needs to be combined with cathodic protection to extend its service life in high water content media environments.

Supporting Materials and Supply Chain Management

Paint suppliers are required to provide complete safety data sheets, product manuals, and third-party testing reports, and packaging must clearly indicate production information. During material acceptance, sampling and testing shall be carried out in accordance with GB/T3186. Unqualified batches shall be double checked, and if they still fail, they shall be rejected. The warp and weft density of fiber-reinforced materials must comply with standard regulations (such as glass cloth warp and weft density ≥ 8 fibers/cm).