Compressive Strength of HDPE Pipes
The compressive strength (external pressure resistance) of HDPE pipes mainly depends on their material grade, wall thickness design (SDR value), and installation conditions. Below are the detailed technical specifications:
Compressive Strength of the Material Itself
|
Property |
Typical Range |
Test Standard |
|
Short-term compressive strength |
20-30 MPa |
ISO 6259 |
|
Long-term compressive strength |
8-12 MPa |
ISO 9080 |
|
Elastic modulus (20°C) |
800-1000 MPa |
ASTM D638 |
Note: Performance varies among different HDPE grades (e.g., PE80, PE100, PE100-RC).
Pipe Ring Stiffness (External Pressure Resistance)
HDPE pipes are primarily characterized by ring stiffness (SN) to indicate their external pressure resistance:
|
Ring Stiffness Grade |
Standard Value (kN/m²) |
Suitable Burial Depth |
Typical Pipe Diameter Range |
|
SN4 |
4 |
≤1.2m (shallow burial) |
DN110-DN400 |
|
SN8 |
8 |
1.2-3m (standard burial) |
DN200-DN800 |
|
SN16 |
16 |
3-6m (deep burial) |
DN400-DN1200 |
Calculation Formula:
Ring Stiffness = (EI)/(D³)
Where:
E = Elastic modulus
I = Moment of inertia
D = Pipe diameter
Pressure Rating (Internal Pressure Resistance)
According to ISO 4427 standards, HDPE pipe pressure ratings are classified as:
|
SDR Value |
Nominal Pressure (PN) |
Maximum Working Pressure (20°C) |
|
SDR11 |
PN10 |
1.0 MPa |
|
SDR17 |
PN6 |
0.6 MPa |
|
SDR26 |
PN4 |
0.4 MPa |
Burst pressure is typically 2.5-4 times the PN value.
Compressive Performance in Practical Engineering Applications
Mining pipelines: Typically require SN8-SN16 grade, capable of withstanding ≥0.8 MPa internal pressure.
Buried pipelines: Under 3m burial depth, a DN500 HDPE pipe exhibits <3% deformation rate.
Extreme cases: Reinforced HDPE pipes for deep-sea mining can withstand 6 MPa external pressure.
Key Factors Affecting Compressive Strength
Temperature: Strength decreases by ~10% per 10°C increase.
Medium: Increased wall thickness is required when transporting abrasive slurries.
Installation quality: Backfill compaction ≥95% is necessary.
Service life: >70% strength retention after 50 years.
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