Class 6 HDPE pipe (ring stiffness SN6) is a medium-high strength grade among high-density polyethylene pipes, and its performance advantages are significant:
Mechanical properties
Ring stiffness ≥6kN/m², can withstand 4 meters of buried soil pressure (under no dynamic load conditions)
Elongation at break >350%, impact resistance is more than 5 times that of PVC pipe
Chemical stability
PH value range 1-14, can resist 90% of corrosive media in municipal sewage
Passed GB/T 17391 slow crack growth test (≥5000 hours)
Fluid characteristics
The inner wall roughness coefficient is only 0.01, and the hydraulic loss is 40% lower than that of concrete pipe
Environmental adaptability
Working temperature -40℃~60℃, outstanding low-temperature brittle crack resistance
1. Municipal drainage trunk network
Applicable to the combined rainwater and sewage system with a pipe diameter of 300-800mm, the design flow rate should be ≥0.6m/s
2. Industrial tailings transportation
Use black thickened type (wall thickness ≥12mm), wear-resistant layer thickness ≥3mm
3. Sponge city infiltration drainage
Perforated 6-grade HDPE pipe (opening rate 8%-15%) used with geotextile
4. Oil and gas field gathering and transportation pipeline
Must comply with SY/T 6652 standard, add 2.5% antistatic agent
|
Indicator |
SN6 Grade |
SN8 Grade |
Test Standard |
|
Ring Stiffness (kN/m²) |
6–7.9 |
8–9.9 |
GB/T 9647 |
|
Maximum Burial Depth (m) |
4 |
6 |
EN 1295-1 |
|
Price Coefficient |
1.0 |
1.3 |
Market Research |
1. Trench excavation
Trench bottom width = pipe diameter + 500mm, slope gradient 1:0.33 (sandy soil)
2. Connection process
Hot-melt welding: The welding temperature must be controlled at 210±5℃, and the pressure holding time is calculated according to the wall thickness × 10 seconds
Electrofusion connection: used Automatic Electrofusion Welding Machine automatically records voltage and current curves
3. Backfill quality control
Layered compaction requirements:
Pipe side: ≥90%
30cm within the top of the pipe: ≥85%
1. Pipe body elliptical deformation
Cause: Backfill material contains large-size stones
Solution: Replace medium-coarse sand backfill, deformation > 5% requires replacement of pipe section
2. Interface leakage
Hot-melt joint inspection: Cut off the port to observe the weld flange (should be uniform and height ≥2mm)
3. Ultraviolet aging
Anti-UV formula pipes containing 2.5% carbon black should be selected for outdoor laying
1. Municipal engineering
Recommend DR17 series (pressure level 1.0MPa), equipped with EPDM rubber ring
2. Chemical industry
Select PE100-RC anti-cracking material, wall thickness increase coefficient 1.25
3. Alpine areas
PE RT-Ⅱ type low-temperature resistant special material should be used
Class 6 HDPE pipe has become the preferred material for modern underground pipeline construction due to its excellent comprehensive performance. In actual engineering, it is necessary to scientifically select the type according to parameters such as load level and medium characteristics, and strictly implement the welding process regulations. With the breakthrough of material modification technology, HDPE pipes will show greater potential in emerging fields such as deep-sea discharge and hydrogen energy transportation in the future. It is recommended that engineering units give priority to manufacturers that have passed ISO 4427 certification to ensure the reliability of material quality.
