Technical Specifications for Installation of TPEP Anti-Corrosion Steel Pipes

Technical Specifications for Installation of TPEP Anti-Corrosion Steel Pipes

TPEP (Two-layer Polyethylene and Epoxy) anti-corrosion steel pipes require careful handling and installation to preserve their coating integrity and ensure long-term performance. The following technical guidelines outline best practices for storage, handling, welding, joint treatment, and pipeline laying in accordance with international and industry standards.

1. Handling and Storage

• Avoid coating damage: Use padded slings or rubber-lined hooks for lifting. Do not drag pipes on the ground.

• Stacking: Store pipes on level ground with soft padding; avoid direct contact with sharp or hard objects.

• Weather protection: Cover stored pipes with tarpaulins in open areas to prevent prolonged UV exposure.

2. Trench Preparation

• Bottom bedding: Use soft sand or fine soil (≥100 mm thick) free of debris or stones.

• Width and depth: Trench dimensions must allow space for jointing and safe handling without forcing the pipe.

• Dewatering: Keep trenches dry before and during pipe installation.

3. Welding and Jointing

• Welding method: Use arc welding (e.g., SMAW or GTAW) with qualified personnel and materials.

• Beveling: Pipe ends should be beveled uniformly; remove any coating 100–150 mm from the weld area before welding.

• Post-weld treatment: After welding, the bare steel area must be cleaned and coated using field joint coating systems, typically heat-shrink sleeves or liquid epoxy compatible with TPEP.

4. Field Joint Anti-Corrosion Coating

• Surface preparation: Clean weld area to SA 2.5 standard (near-white metal blast cleaning).

• Coating materials: Use compatible materials with TPEP (e.g., 3-layer heat shrink sleeves or liquid epoxy + PE tape systems).

• Inspection: Ensure overlap and adhesion meet manufacturer specifications. Perform peel and continuity tests.

5. Pipeline Lowering and Backfilling

• Lowering method: Use wide, non-abrasive belts or cradles to gently place the pipe into the trench.

• Backfill material: Use selected fine soil or sand free of sharp objects. Avoid large rocks or frozen chunks.

• Backfill process: Compact in layers (especially around the sides of the pipe) to provide uniform support.

• Warning tape: Place detectable warning tape 300–500 mm above the pipe.

6. Pressure Testing

• Hydrostatic test: After backfilling and curing of joint coatings, perform pressure test per design requirement.

• Leak detection: Monitor joints and connections for leaks; repair and retest as needed.

7. Quality Control and Inspection

• Coating inspection: Perform visual checks for cracks, blisters, or disbondment.

• Holiday detection: Use high-voltage holiday detector to find pinholes in the coating.

• Thickness testing: Check coating thickness at factory and joints using magnetic gauges.

• Documentation: Record all inspection and repair logs as part of final acceptance.

8. Environmental and Safety Considerations

• Weather limits: Avoid applying joint coatings in rain, snow, or high humidity.

• Safety gear: Workers must wear gloves, masks, and protective clothing when handling epoxy or heat-shrink sleeves.

• Environmental protection: Prevent coating debris, solvents, and epoxy from contaminating soil or water sources.

Conclusion

Proper execution of TPEP-coated steel pipe installation ensures the long-term integrity and corrosion resistance of buried pipelines. Adherence to standardized handling, jointing, coating repair, and inspection procedures is essential for successful project delivery and pipeline service life.