Class K8 DN500 ductile iron pipe has a nominal wall thickness of 8.0 mm, calculated per ISO 2531’s formula e = K × (0.5 + 0.001 × DN) (K = 8, DN = 500 mm) . It is rated PN 12.5 (1.25 MPa) for medium‑pressure water, gas and fire mains . With cement‑mortar lining and optional loose‑fit polyethylene encasement, its design life exceeds 100 years, reaching up to 110 years under severe soil conditions . Installation uses push‑on (“Tyton”), mechanical and flanged joints conforming to ISO 2531, AWWA C111 and ANSI B16.1 standards. In the K‑series, wall thickness climbs from 7.0 mm (K7) to 8.0 mm (K8) to 9.0 mm (K9) to 12.0 mm (K12), with prices ranging USD 480–600 / ton for K8, reflecting its cost‑performance balance.
Applications
Potable Water Distribution
K8 DN500 pipes form the backbone of large municipal mains, delivering stable hydraulic performance with minimal leakage .
Sewage & Drainage
Abrasion‑resistant ductile iron and smooth cement‑mortar lining handle grit‑laden wastewater in gravity or pressure sewers .
Irrigation Systems
Uniform flow and surge resilience support agricultural and landscape irrigation networks under variable demands .
Gas Distribution
When produced and tested per EN 969 with external coatings, K8 DN500 safely conveys natural gas up to 16 bar .
Fire‑Protection Mains
High ductility and surge capacity ensure reliable hydrant loops and feeder mains for fire suppression systems .
Service Life
Modern ductile iron pipe is proven to last 100+ years in benign soils, thanks to its high‑strength matrix and cement linings .
Loose‑fit polyethylene sleeving per ISO 8180 extends life to 110 years even in aggressive soils, as confirmed by DIPRA test sites .
A lifecycle cost analysis by AWWA shows that ductile iron mains reduce total system costs—including pumping energy and maintenance—by millions over 50 years compared to alternatives .
Installation & Connection
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Push‑On (“Tyton”) Joints: Spigot‑socket assembly with elastomeric gasket for rapid, bolt‑free sealing per ISO 2531 .
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Mechanical Joints: Gland‑and‑bolt restraint for fittings and valves, meeting AWWA C111 dimensions for DN 80–600 mm .
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Flanged Joints: ANSI B16.1 or EN 1092 flanges enable easy disassembly and high axial‑load resistance .
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Best Practices: Proper trench bedding, ≤3 % deflection, hydrostatic testing and chlorination per ISO 2531/AWWA C600 maximize pipeline integrity .
K‑Series Comparison & Pricing
| Class | Wall Thickness<br>(e = K·(0.5 + 0.001·DN)) | Pressure Rating | Price (USD/ton) |
|---|---|---|---|
| K7 | 7 × (0.5+0.001×500) = 7.0 mm | PN 10 (1.0 MPa) | $450–500 |
| K8 | 8 × (0.5+0.001×500) = 8.0 mm | PN 12.5 (1.25 MPa) | $480–600 |
| K9 | 9 × (0.5+0.001×500) = 9.0 mm | PN 16 (1.6 MPa) | $550–650 |
| K12 | 12 × (0.5+0.001×500) = 12.0 mm | PN 25 (2.5 MPa) | $700–900 |
Thickness formula per ISO 2531 . Prices from global market surveys (Alibaba, Made‑in‑China) .
International Standards
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ISO 2531:2009 – Pipe dimensions, linings & joint performance.
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GB/T 13295‑2019 – Chinese national standard for DIP, fittings & joints.
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ISO 8180 – Polyethylene encasement for external corrosion control.
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AWWA C111/A21.11 – Mechanical‑joint dimensions for DN 80–600 mm.
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ANSI B16.1 – Flanged‑joint dimensions & ratings.
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EN 969:2009 – Requirements for gas‑pipeline DI pipe & fittings.
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ISO 1083 – Ductile iron material grades (tensile ≥ 420 MPa) .
Advantages
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Exceptional Longevity: 100+ year design life minimizes replacements.
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High Strength & Toughness: Tensile strength ≥ 420 MPa resists surges & external loads.
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Superior Corrosion Control: Cement‑mortar lining, zinc/bitumen coatings + LPS.
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Versatile Jointing: Push‑on, mechanical, flanged & restrained systems.
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Sustainability: Recycled feedstock, fully recyclable, lower life‑cycle energy than plastics.
FAQ
Q1: How do K classes differ?
They follow e = K·(0.5 + 0.001 DN)—for DN 500, K7=7.0 mm, K8=8.0 mm, K9=9.0 mm, K12=12.0 mm, matching PN 10/12.5/16/25 respectively .
Q2: Which joint type is best?
– Push‑on for speed; Mechanical for restraint; Flanged for maintenance access and axial loads .
Q3: Do I need polyethylene sleeving?
Recommended in aggressive soils for up to 110 years life; proven by DIPRA Logandale tests .
Q4: What sizes & lengths are available?
DN 80–2600 mm, standard 6 m laying lengths (5.7 m for containers), custom cuts on demand .
Case Studies
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AWWA Lifecycle Analysis: A 24″ (DN600) pipeline evaluation showed ductile iron’s lowest total cost over 50 years, factoring design, O&M, energy and salvage value .
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DIPRA Poly Encasement Tests: HDPE‑sleeved pipes at Logandale, NV, remained in “excellent” condition after decades in corrosive soils .
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Energy & Cost Savings: A Journal AWWA study found ductile iron mains save utilities millions in energy and maintenance versus alternative materials.
ductile iron pipe dimensions
| Pipe body weight （kg/m) | |||||||||||||||
| (Inside Diameter) | (Outside Diameter) | Socket Weight | K8 | K9 | K10 | C class | Total weight of Active Length=6M (kg) | Total weight of Active Length=5.7M (kg) | |||||||
| DN(mm) | OD(mm) | ≈ kg | Class | kg/m | K8 | K9 | K10 | C class | K8 | K9 | K10 | C class | |||
| 80 | 98 | 3.40 | 12.20 | 12.20 | 12.20 | C40 | 9.10 | 77.00 | 77.00 | 77.00 | 58.00 | 73.00 | 73.00 | 73.00 | 55.00 |
| 100 | 118 | 4.30 | 14.90 | 15.10 | 15.10 | C40 | 11.12 | 93.70 | 95.00 | 95.00 | 71.00 | 90.00 | 91.00 | 90.00 | 68.00 |
| 125 | 144 | 5.70 | 18.90 | C40 | 119.00 | ||||||||||
| 150 | 170 | 7.10 | 21.80 | 22.80 | 22.80 | C40 | 16.48 | 138.00 | 144.00 | 144.00 | 106.00 | 132.00 | 138.00 | 137.00 | 101.00 |
| 200 | 222 | 10.30 | 28.70 | 30.60 | 30.60 | C40 | 22.62 | 183.00 | 194.00 | 194.00 | 146.00 | 174.00 | 185.00 | 185.00 | 139.00 |
| 250 | 274 | 14.20 | 35.60 | 40.20 | 44.30 | C40 | 32.63 | 228.00 | 255.00 | 280.00 | 210.00 | 218.00 | 244.00 | 267.00 | 200.00 |
| 300 | 326 | 18.90 | 45.30 | 50.80 | 56.30 | C30 | 43.90 | 290.00 | 323.00 | 357.00 | 282.00 | 278.00 | 309.00 | 340.00 | 269.00 |
| 350 | 378 | 23.70 | 55.90 | 63.20 | 69.60 | C30 | 51.88 | 359.00 | 403.00 | 441.00 | 335.00 | 343.00 | 384.00 | 420.00 | 319.00 |
| 400 | 429 | 29.50 | 67.30 | 75.50 | 83.70 | C30 | 60.78 | 433.00 | 482.00 | 532.00 | 394.00 | 414.00 | 460.00 | 506.00 | 376.00 |
| 450 | 480 | 38.30 | 80.00 | 89.30 | 99.00 | C30 | 73.30 | 515.00 | 575.00 | 632.00 | 472.00 | 492.00 | 550.00 | 597.00 | 450.00 |
| 500 | 532 | 42.80 | 92.80 | 104.30 | 115.60 | C30 | 87.20 | 600.00 | 669.00 | 736.00 | 566.00 | 572.00 | 638.00 | 702.00 | 540.00 |
| 600 | 635 | 59.30 | 122.00 | 137.30 | 152.00 | C30 | 120.62 | 791.00 | 882.00 | 971.00 | 783.00 | 755.00 | 842.00 | 926.00 | 747.00 |
| 700 | 738 | 79.10 | 155.00 | 173.90 | 193.00 | C25 | 142.15 | 1009.00 | 1123.00 | 1237.00 | 932.00 | 963.00 | 1071.00 | 1179.00 | 889.00 |
| 800 | 842 | 102.60 | 192.00 | 215.20 | 239.00 | C25 | 177.07 | 1255.00 | 1394.00 | 1537.00 | 1165.00 | 1197.00 | 1330.00 | 1465.00 | 1112.00 |
| 900 | 945 | 129.60 | 232.00 | 260.20 | 289.00 | C25 | 197.68 | 1521.00 | 1691.00 | 1863.00 | 1446.00 | 1452.00 | 1613.00 | 1777.00 | 1257.00 |
| 1000 | 1048 | 161.30 | 275.00 | 309.30 | 343.20 | C25 | 266.28 | 1811.00 | 2017.00 | 2221.00 | 1759.00 | 1729.00 | 1925.00 | 2118.00 | 1679.00 |
| 1100 | 1152 | 194.70 | 362.80 | 2372.00 | |||||||||||
| 1200 | 1255 | 237.70 | 374.00 | 420.10 | 466.10 | C25 | 373.88 | 2482.00 | 2758.00 | 3034.00 | 2481.00 | 2370.00 | 2632.00 | 2894.00 | 2369.00 |
| 1400 | 1462 | 279.30 | 547.20 | 3563.00 | |||||||||||
ductile iron pipe Mechanical property
| Mechanical Property | |||||||
| Nominal Diameter | Hydraulic test | Tensile strength | Elogation | Yield strength | Bending strength | Brinell hardness | Thickness of cement lining |
| DN(MM) | Mpa | Mpa | % | Mpa | Mpa | HB | mm |
| DN80-DN300 | 5 | ≥420 | ≥10 | ≥300 | ≥590 | ≤230 | 3 |
| DN350-DN600 | 4 | ≥420 | ≥10 | ≥300 | ≥590 | ≤230 | 5 |
| DN700-DN1000 | 3.2 | ≥420 | ≥10 | ≥300 | ≥590 | ≤230 | 6 |
| DN1100-DN1600 | 2.5 | ≥420 | ≥7 | ≥300 | ≥590 | ≤230 | ….. |
