HDPE pipes (high-density polyethylene pipes) are widely used in agricultural irrigation due to their corrosion resistance, aging resistance, good flexibility, and convenient construction. Reasonable selection of pipe diameter and pressure level can effectively improve irrigation efficiency, reduce costs, and extend service life. This article will systematically introduce the selection method of HDPE pipes in agricultural irrigation from three aspects: selection principle, diameter calculation, and pressure level determination.
1. Meet the irrigation flow demand
The pipe diameter must ensure sufficient flow to avoid excessive hydraulic loss due to too small a diameter, which will affect the irrigation effect.
2. Ensure water delivery pressure
According to the terrain height difference, pipe length, and terminal equipment requirements, reasonably select the pressure level to avoid pipe bursting or insufficient water pressure.
3. Take into account economy
The larger the diameter, the higher the investment. It is necessary to optimize the pipe size and reduce the construction and operation costs on the premise of meeting the use requirements.
1. Basic formula
Common flow-velocity formula for irrigation system to calculate pipe diameter:
Q=A×VQ = A \times VQ=A×V
Where:
Q = flow (m³/s)
A = pipe cross-sectional area (m²), A = π × (D/2)²
V = flow velocity (m/s)
2. Recommended flow velocity
Pipe Diameter Range | Recommended Flow Velocity (m/s) | Remarks |
D < 100mm | 0.6 - 1.5 | Low velocity for small diameters to avoid water hammer |
100mm ≤ D ≤ 300mm | 1.0 - 2.0 | Moderate velocity for medium diameters |
D > 300mm | 1.2 - 2.5 | Higher velocity allowed for large diameters |
3. Diameter calculation example
Assuming the design flow rate is 50m³/h, convert to m³/s:
Q=503600≈0.0139 m3/sQ = \frac{50}{3600} ≈ 0.0139 \, m³/sQ=360050≈0.0139m3/s
Take the design flow rate V = 1.5 m/s, then the pipe cross-sectional area:
A=QV=0.01391.5≈0.00927 m2A = \frac{Q}{V} = \frac{0.0139}{1.5} ≈ 0.00927 \, m²A=VQ=1.50.0139≈0.00927m2
Calculate the inner diameter D:
D=2×Aπ=2×0.009273.1416≈0.1085 m≈110mmD = 2 \times \sqrt{\frac{A}{\pi}} = 2 \times \sqrt{\frac{0.00927}{3.1416}} ≈ 0.1085 \, m ≈ 110mmD=2×πA=2×3.14160.00927≈0.1085m≈110mm
Therefore, DN110 HDPE pipe is recommended.
1. Common nominal pressure (PN) levels
Nominal Pressure (PN) | Maximum Working Pressure (MPa) | Application Scenario |
PN6 | 0.6 MPa | Gravity flow, low-pressure water conveyance |
PN10 | 1.0 MPa | General farmland irrigation |
PN12.5 | 1.25 MPa | Undulating terrain, medium to long-distance water transport |
PN16 | 1.6 MPa | Large elevation differences or sprinkler systems |
PN20 | 2.0 MPa | High-pressure main water supply pipelines |
2. Pressure verification formula (Hagen-William formula)
Hf=10.67×L×Q1.85C1.85×D4.87H_f = 10.67 \times \frac{L \times Q^{1.85}}{C^{1.85} \times D^{4.87}}Hf=10.67×C1.85×D4.87L×Q1.85
H_f = Head loss along the way (m)
L = Pipeline length (m)
Q = Flow rate (L/s)
C = Hagen-William roughness coefficient (HDPE takes 150)
D = Pipeline inner diameter (mm)
According to the water source pressure, head and terminal equipment requirements, after verifying the head loss, select the appropriate pressure level.
Determine the design flow (based on the irrigation area, irrigation method, etc.).
Select a reasonable flow rate (based on pipe diameter and system type).
Calculate the pipe diameter (to ensure sufficient flow and economic rationality).
Calculate the head loss based on the terrain and pipe length.
Determine the pressure level (to meet safety and operation requirements).
Comprehensively consider cost and installation convenience to optimize the selection.
Official website: www.phtopindustry.com | www.phpipes.com
Contact us: Email:inquiry@phtopindustry.com | Whatsapp:+86 15093100892
Company address: Room 802, 8th Floor, Building 5, Jinyin Modern City, Jinshui District, Zhengzhou City, Henan Province, China
HDPE (High-Density Polyethylene) pipes have become the preferred choice for modern agricultural irrigation systems due to their outstanding advantages:
Exceptional Weather Resistance: UV-resistant additives ensure over 20 years of outdoor use without aging
Superior Flexibility: Can withstand ground settlement with seismic resistance 5 times that of steel pipes
Ultra-Low Water Delivery Loss: Inner wall smoothness of 0.009mm, with friction coefficient only 1/3 of steel pipes
Eco-Friendly and Safe: NSF certified, fully compliant with drinking water standards
Cost-Effective and Durable: 40% lower overall cost than steel pipes with a service life of 50 years
(1) Golden Rules for Pipe Diameter Calculation
Flow Rate Formula:
Q=π×(D/2)²×v×3600
(Q: m³/h; D: Pipe diameter in m; v: Flow velocity in m/s)
Flow Velocity Control Standards:
Branch pipes: 0.6-1.0m/s
Main pipes: 1.0-1.5m/s
Maximum not exceeding 2.5m/s
Common Specification Reference Table:
Irrigation Area (acre) | Drip Irrigation System | Sprinkler System | Main Pipeline |
Below 50 | Φ32-50mm | Φ63-75mm | Φ90-110mm |
50-200 | Φ50-63mm | Φ75-90mm | Φ110-160mm |
200-500 | Φ63-75mm | Φ90-110mm | Φ160-200mm |
(2) Pressure Rating Selection Guide
Pressure Loss Formula:
hf=λ×(L/D)×(v²/2g)
(λ value: 0.02-0.03)
Pressure Rating Recommendations:
Irrigation Type | Working Pressure | Recommended Rating | Safety Factor |
Drip Irrigation | 0.15MPa | PN0.8 | 1.5 |
Micro Spray | 0.25MPa | PN1.0 | 1.6 |
Sprinkler | 0.5MPa | PN1.6 | 1.8 |
Hub Project | 0.8MPa | PN2.0 | 2.0 |
(3) Advanced Material Selection Guide
PE100 vs PE80:
Strength: PE100 is 25% stronger than PE80
Cost: PE100 is 15-20% more expensive
Application Scenarios:
Drip irrigation branch pipes: PE80
High-pressure main pipes: PE100
Anti-Aging Performance:
Standard type: 3 years outdoor lifespan
UV-resistant type: Contains 2.5% carbon black, lifespan 20+ years
Recommendation: Above-ground sections must use UV-resistant type
(1) High-Sediment Water
Choose SDR11 thick-walled pipes
Maintain flow velocity above 1.2m/s to prevent sedimentation
Install sediment traps every 500m
(2) Cold Climate Areas
Use low-temperature impact-resistant PE-RT material
Burial depth ≥ frost line +20cm
Implement electric heat tracing systems
(3) Slope Irrigation
Use SDR17 series for slopes >15°
Install pressure relief valves every 50m
Use flange-type anchor blocks for fixation
Pipe Diameter Combination Plan:
Main pipes: PE100 PN1.6
Branch pipes: PE80 PN1.0
Capillary pipes: PE40 PN0.6
Procurement Techniques:
Bulk purchase discounts: >5000 meters can get 20% off
Seasonal procurement: 10-15% lower prices in winter
Direct factory purchase eliminates middleman margins
Hot Melt Welding Parameters:
Temperature: 210±5℃
Pressure: 0.15-0.3MPa
Time: Pipe diameter ×10 seconds (mm)
Pressure Testing Standards:
Strength test: 1.5× working pressure, hold for 1 hour
Leak test: 1.1× working pressure, hold for 2 hours
Backfill Requirements:
First layer: 20cm fine sand bedding
Compact in layers (each layer ≤30cm)
Compaction density ≥90%
Water Hammer Effect:
Install slow-closing check valves
Set up pressure regulating towers
Use SDR26 thin-walled pipes to absorb impact
Algae Growth:
Choose black opaque pipes
Regularly inject sodium hypochlorite solution
Install UV sterilizers
Rodent Damage:
Use HDPE material with rodent repellent
Burial depth ≥80cm
Use protective sleeves for critical sections
Through scientific selection, HDPE irrigation systems can achieve 30% water savings, 25% energy savings, and 15% yield increase. We recommend involving professional irrigation engineers at the planning stage and adopting EPC mode to ensure optimal system performance.
Official website: www.phtopindustry.com | www.pefitting.net
Contact us: Email:inquiry@phtopindustry.com | Whatsapp:+86 15093100892
Company address: Room 802, 8th Floor, Building 5, Jinyin Modern City, Jinshui District, Zhengzhou City, Henan Province, China