3LPE Steel Pipe

Tianjin Lefin Industrial Co., Ltd is one of the most experienced manufacturers and suppliers of 3lpe steel pipe in China. Please feel free to buy high quality 3lpe steel pipe from our factory. Good service and reasonable price are available.

3LPE (ThreeLayer Polyethylene) steel pipe, also known as three-layer polyethylene anti-corrosion steel pipe, is a type of steel pipe that has a composite anti-corrosion coating of "epoxy powder base layer + adhesive middle layer + high-density polyethylene outer layer" applied to its outer wall. This type of steel pipe is commonly referred to as 3PE in the industry.

1. Coating structure (from inside to outside)

• Bottom layer: Epoxy powder (FBE)

1. Thickness: ≥ 80–100 μm
2. Function: Chemically bonded to the steel pipe, dense and corrosion-resistant, anti-anode peeling, blocking electrochemical corrosion.

• Middle layer: Adhesive (AD)

1. Thickness: 170–250 μm
2. Function: "Molecular bridge", bonding FBE and PE, buffering thermal expansion and contraction stress, preventing cracking.

• Outer layer: High-density polyethylene (HDPE)

1. Thickness: Ordinary grade 1.8–2.0 mm; Reinforced grade 2.2–2.4 mm; Super reinforced grade 2.9–3.7 mm
2. Function: Mechanical protection + water/chemical barrier, water absorption rate < 0.01%, impact resistance, wear resistance.

2. Common Standards and Materials

• Execution Standards: GB/T 232572017, SY/T 04132022, API RP 5L.
• Steel Pipe Materials: Carbon steel (Gr.B, X42–X80), Spiral Welded Pipe, Seamless Welded Pipe, Straight Seam Welded Pipe.
• Specifications: Outer Diameter 60–3000 mm, Wall Thickness 4.5–50 mm, Length 6–18 m. 

1. Ultra-anti-corrosion, long service life

• Resistant to soil acidity and alkalinity (pH 3–12), seawater, salt fog, microorganisms, hydrogen sulfide corrosion.
• Design life for underground installation ≥ 50 years, far superior to asphalt, single-layer FBE, 2PE (approximately 15–20 years).
• Strong anti-anode peeling (≤ 8 mm, 65℃/48h), compatible with cathodic protection systems.

2. Strong mechanical properties, resistant to construction damage

• Impact resistance: ≥ 10 J/mm, capable of withstanding crushed stone compression and mechanical collision.
• Magnetic resistance: 5–8 times that of ordinary carbon steel, suitable for rock sections, directional drilling (HDD), and pipe jacking.
• Good ductility: Can adapt to ±2.5% deformation of the pipeline without cracking.

3. Wide temperature adaptability

• Long-term operation: 40℃ to 80℃; short-term can withstand 150℃.
• Weather resistance: Outer layer contains carbon black (2.5% ± 0.5%), resistant to ultraviolet rays, suitable for temporary storage in the open air.

4. Low permeability, good insulation

• Closed-cell ratio approximately 92%, water absorption rate < 0.01%, prevents moisture and ion penetration.
• High insulation resistance (> 10¹⁴ Ω·cm), effectively inhibits stray current corrosion.

5. Environmentally friendly, hygienic, energy-saving

• No solvents, no heavy metals, suitable for drinking water pipelines.
• Smooth surface, low friction resistance, reduces transportation energy consumption by approximately 10–15%.

1. Underground long-distance pipelines (core scenario)

• Oil and gas pipelines: West-to-East Gas Transmission, long-distance crude oil/fuel oil transportation (high pressure, sulfur-containing, soil corrosion).
• Urban gas/heating: High pressure, high temperature, high groundwater level, stray current areas.
• Water conveyance: Large diameter (DN2000+), high salt and alkalinity, swamps, crossing rivers/railways.

2. Corrosive soil environments

• Sodic soil, wetland areas: High chloride ions, sulfate ions, prone to electrochemical corrosion.
• Acidic/alkaline soil: pH < 4 or pH > 9, microbial active areas.
• Mining/industrial pollution areas: Heavy metals, chemical waste liquid infiltration, strong corrosion.

3. Marine and coastal environments

• Undersea pipelines, cross-sea pipelines: High salt content, ocean current erosion, microbial adhesion (select reinforced grade ≥ 3.7 mm).
• Coastal power plants, seawater desalination: Salt fog, dry-wet alternation, high Cl⁻ concentration.

4. Complex geology and special construction

• Rock/pebble strata: Strong mechanical friction, strong compression, high scratch resistance requirements.
• Permafrost/cold regions: 40℃ low temperature, freeze-thaw cycles, coating resistant to low-temperature cracking.
  
• Directional drilling (HDD)/pipe jacking: Long distance, strong friction, bending deformation, requires high-toughness coating.

5. Not recommended environments

• Long-term > 80℃ (such as steam pipelines, select 3LPP).
• Strong chemical corrosion (concentrated acid/concentrated alkali) direct contact (3LPE is resistant to acid and alkali but not resistant to long-term immersion in strong corrosive media).

• 3LPE: Anti-corrosion + strong mechanical properties, 50-year service life, suitable for harsh underground/ocean environments, medium-high cost.
• Single-layer FBE: Good anti-corrosion, weak mechanical properties, 20–30-year service life, suitable for station areas/non-underground.
• 2PE: Strong mechanical properties, weak anti-corrosion, 15–20-year service life, suitable for general soil.
• Asphalt/coke oil: Cheap, short service life (5–10 years), heavy pollution, gradually phased out.

3LPE steel pipes are currently the "gold standard" for anti-corrosion of underground/ocean steel pipes, with the core features of "three-layer composite, strong anti-corrosion, high mechanical properties, wide temperature range, long service life", especially suitable for long-distance oil and gas transportation, high-salt and alkaline/swamp soil, marine environments, rock/frozen soil, and directional drilling construction under harsh conditions.