Installation Precautions for HDPE Pipes in Municipal Engineering
HDPE (High-Density Polyethylene) pipes are widely used in municipal engineering due to their excellent corrosion resistance, flexibility, and long service life. To ensure project quality and durability, the following key points must be strictly observed during installation:
Pre-Construction Preparation
1. Material Inspection
Check pipe appearance: uniform color, free of bubbles, cracks, dents, or other defects.
Stiffness requirement: Municipal drainage pipes should have a ring stiffness ≥ 4000 N/m² (SN4).
Pipe end flatness: Straightness tolerance should be less than 3‰.
2. Trench Excavation
Width requirement: Pipe outer diameter + 0.3 m (for above-ground connections) or + 0.5 m (for in-trench connections), with a minimum width ≥ 0.7 m.
Base treatment: Avoid disturbing the natural soil; backfill and compact with graded gravel if over-excavated.
Groundwater control: Lower the water table to 0.3–0.5 m below the trench bottom.
Key Installation Techniques
1. Connection Methods
Butt Fusion (DN ≥ 75 mm): Temperature 210 ± 10°C, voltage stabilized at 200–220 V.
Electrofusion (for confined spaces): Suitable for pipe wells and restricted areas.
Socket Fusion (DN ≤ 63 mm): Control heating time to avoid excessive melt flow.
2. Special Environmental Considerations
Summer installation (DN ≤ 110 mm): Use a serpentine layout to compensate for thermal expansion.
Outdoor installation: Apply shading measures to prevent UV degradation.
Low-temperature environments (below -10°C): Use special low-temperature-resistant pipes.
3. Pipe Laying
Lowering method: Use non-metallic slings (secured at 1/4 of the pipe length from the end); never use center lifting.
Foundation treatment: Use gravel bedding (50–200 mm thick); avoid concrete foundations.
Backfilling & Quality Inspection
1. Backfilling Requirements
Layered backfilling: Use medium-coarse sand for pipe sides, compaction ≥ 90%.
Mechanical backfilling restriction: Only allowed above 0.7 m from the pipe crown.
Symmetrical backfilling: Backfill both sides simultaneously to prevent deformation.
2. Quality Inspection Standards
Pressure test: Use water as the medium, maintain pressure for 30 minutes.
Joint inspection: Butt fusion beads should be uniform (height ≥ 2 mm).
Alignment control: Horizontal deviation ≤ 1.5 mm/m, total length ≤ 25 mm.
Special Considerations
1. Safety Risk Prevention
Static electricity protection: Anti-static measures required in flammable environments.
Trench safety: Install supports to prevent collapse.
Large-diameter pipes (DN ≥ 400): Require special construction plans to control rebound risks.
2. Connection with Manholes
Flexible connection: Use rubber gaskets to prevent leaks.
Anti-settlement treatment: Enhance compaction within 1 m of the manhole.
Table: Key Control Indicators for HDPE Pipes in Municipal Engineering
|
Item |
Standard Requirement |
Test Method |
|
Ring stiffness |
≥ SN4 (4000 N/m²) |
Pressure test |
|
Fusion temperature |
210 ± 10°C |
Infrared thermometer |
|
Backfill compaction |
≥ 90% (pipe sides) |
Sand replacement method |
|
Leak tightness |
0.8 MPa/30 min, no leakage |
Hydrostatic test |
By strictly adhering to these technical requirements, HDPE pipeline systems can achieve optimal performance in municipal engineering. It is recommended to conduct pre-construction technical briefings and establish a complete quality traceability system (e.g., RFID tagging) for full lifecycle quality control. For special geological conditions or large-diameter pipes (e.g., DN ≥ 800 mm steel-reinforced pipes), refer to the manufacturer’s specialized construction guidelines.
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