Class K12 DN350 ductile iron pipe combines a 350 mm nominal diameter with a 12 bar working pressure, offering an optimal balance of strength, corrosion resistance, and hydraulic performance for modern infrastructure projects. Its cement-mortar internal lining and fusion-bonded epoxy or bitumen external coatings ensure a service life exceeding 100 years, outperforming many alternative materials in full-life cost analyses. Multiple jointing systems—including push-on, mechanical, and self-restraining—allow rapid, leak-tight assembly in both trench and trenchless environments. Fully compliant with ISO 2531, EN 545, EN 598, ASTM A 536, and GB 13295, these pipes meet global standards for potable water, wastewater, fire-fighting, and industrial applications.
Application Scenarios
Municipalities deploy DN350 K12 pipes for potable water distribution, where the smooth cement-mortar lining resists biofilm formation and maintains water quality under varying flow regimes. In wastewater and sewer force mains, their 12 bar rating and abrasion-resistant lining reduce friction losses and extend maintenance intervals in high-flow systems. Fire-fighting networks leverage DN350’s high flow capacity and heat-resistant coatings to deliver rapid, high-pressure water supply to hydrants and sprinklers in industrial parks and large facilities. In industrial plants, these pipes convey process water, cooling fluids, and chemicals, benefitting from ductile iron’s impact resistance and dimensional stability under cyclic loads. For trenchless installations such as HDD and river crossings, DN350’s weight, ductility, and coated exterior guard against soil movement, stray currents, and subaqueous corrosion.
Service Life
Modern ductile iron pipe is engineered to last 100 years or more, as documented by the Ductile Iron Pipe Research Association’s Longevity program and century-old mains still in operation today. Lifecycle cost analyses show that over a century, DN350 K12 pipelines can yield significant net present value savings compared to PVC or HDPE alternatives, driven by lower energy losses and fewer repairs.
Installation & Jointing
Push-On Joints
EPDM-gasketed bell-and-spigot assemblies allow quick, tool-light connections, maintaining leak-tight seals up to 12 bar without supplementary restraints.
Mechanical Joints
Megalug® mechanical restraints clamp to standard flanged ends, providing axial thrust restraint and accommodating pressures well above 12 bar without external blocking .
Self-Restraining Joints
Integral locking lugs in the bell eliminate the need for concrete thrust blocks, accelerating installation at bends and tees while ensuring joint integrity under dynamic loads.
Corrosion Protection & Encasement
Polyethylene encasement per ANSI/AWWA C105/A21.5 wraps each barrel and joint, blocking stray currents and aggressive soil chemistries to sustain >100 years of service in corrosive environments.
International Standards
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ISO 2531:2015 – Ductile iron pipes, fittings, linings, and joints for water pipelines.
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EN 545:2010 – Standards for water supply ductile iron pipes and fittings.
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EN 598:2007 – Guidelines for sewerage ductile iron pipes, fittings, and accessories.
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ASTM A 536 – Material specifications for ductile iron castings in pressure pipe systems.
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GB 13295-2019 – Chinese national standard for ductile cast iron pipes and coatings.
Price Comparison
| Series / Class | Typical DN350 Price (USD/m) | Source |
|---|---|---|
| Class K9 | 430 – 470 | Alibaba |
| Class K12 | 450 – 700 | Alibaba |
| PN10 (C25) | 400 – 550 | Alibaba |
| PN16 (C30) | 500 – 650 | Alibaba |
Note: Prices vary by coating, joint type, order volume, and region. Consult local suppliers for exact quotes.
Key Advantages
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Centennial Durability: Proven >100 year service life reduces replacement cycles and downtime.
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High Pressure Rating: 12 bar working pressure supports fire mains and industrial networks without upsizing.
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Corrosion Resistance: Combination of cement-mortar lining and epoxy/bitumen coatings protects internal and external surfaces.
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Installation Flexibility: Adaptable joint systems and encasement options suit trench, trenchless, seismic, and subaqueous conditions.
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Environmental Sustainability: High recycled-iron content and full recyclability align with circular-economy goals.
Frequently Asked Questions
Q1: What does “DN350” mean?
“DN350” denotes a nominal internal diameter of 350 mm, standardized under ISO 2531 and related specifications.
Q2: What defines “Class K12”?
“K-class” categories indicate pressure ratings in bar; Class K12 pipes are rated for 12 bar working pressure with thicker walls than K9 or C-class equivalents.
Q3: Which joint type is best?
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Push-on for fast, low-tool installations
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Mechanical for axial restraint and easy disassembly
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Self-restraining for minimal excavation and thrust blocking
Q4: Are DN350 pipes suitable for trenchless methods?
Yes—ductile iron’s flexural ductility, combined with restrained joints and coatings, enables HDD and microtunnelling installations with minimal surface disruption.
Q5: How long will these pipes last?
With proper installation, jointing, and corrosion control, DN350 K12 pipes typically exceed 100 years of reliable service.
Case Studies
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Brussels Renewal (Belgium): A 440 m section of DN350 water main was rehabilitated using trenchless Primus Liner®, completed in just four days with minimal surface disruption.
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California HDD Crossing (USA): A DN350 K9 trunk main installed via HDD with restrained joints cut installation time by 40% and avoided extensive excavation along a sensitive riverbank .
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Kobe Earthquake Resilience (Japan): Pre-1995 SⅡ-type DN350 ductile iron mains remained intact after 1.3 m ground subsidence, showcasing exceptional seismic performance .
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U.S. Municipal Upgrades: Multiple DIPRA case studies report zero failures and a 70% reduction in break rates after replacing aging mains with Class K ductile iron systems over two decades.
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 | ….. |
