Class K9 DN350 ductile iron pipe offers a robust solution for demanding water and wastewater systems. Its iron-graphite matrix delivers superior tensile strength and ductility, ensuring reliable performance under high pressures and corrosive conditions. With an expected service life exceeding 100 years and straightforward installation using push-on or restrained-joint systems, it minimizes both lifecycle and maintenance costs. As part of a family that includes Class K7, K8, K9, and K12, DN350 pipe allows designers to select the optimal balance of pressure rating, wall thickness, and budget. Compliant with ISO 2531, EN 545/598, AWWA C151/AWWA C110, and other global standards, Class K9 pipe meets rigorous quality benchmarks.
Application Scenarios
Ductile iron pipe is widely used in:
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Potable water distribution (municipal networks, pumping mains)
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Wastewater conveyance (gravity sewers, force mains, treatment plant piping)
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Industrial process and raw water intake (power plants, steelworks, chemical plants)
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Subaqueous crossings & trenchless installations (river crossings, HDD, microtunneling)
Short spans, high-pressure zones, and corrosive soils pose minimal risk due to ductile iron’s high toughness and advanced linings.
Service Life
Modern ductile iron pipe retains full mechanical properties for over a century under normal conditions.
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100+ year lifespan confirmed by long-term utility audits
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Corrosion resistance via cement-mortar lining and external zinc-bitumen or polyethylene coatings
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Sustainability: ≥ 80 % recycled material content; energy-efficient manufacturing and recyclability
Economic studies show energy savings up to 3 % of operating budgets, translating into millions in present-value savings over a 50-year horizon.
Installation and Jointing
Class K9 DN350 pipe accommodates various jointing systems:
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Push-on joints: Rapid assembly, no thrust blocks required for moderate pressures
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Restrained-joint systems (e.g., Megalug®): Ideal for thrust-restraint scenarios, eliminates concrete thrust blocks
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Flanged connections: Used for valves and fittings, compatible with standard PN10/PN16 flanges
Encasement options (polyethylene sleeving) protect joints in aggressive soils; trenchless methods preserve urban infrastructure.
Product Series Comparison and Pricing
| Class | Pressure Rating | Wall Thickness (DN350) | Typical Price/Ton (USD) | Key Use Case |
|---|---|---|---|---|
| K7 | 7 bar | ~6.0 mm | ~880–900 | Low-pressure distribution |
| K8 | 8 bar | ~6.8 mm | ~880–900 | Medium distribution |
| K9 | 9 bar | ~7.7 mm | ~880–900 | Standard water mains |
| K12 | 12 bar | ~10.2 mm | ~880–900 | High-pressure transmission |
Wall thickness formula: T = K × (0.5 + 0.001 D), where D = 350 mm and K = class coefficient.
International Standards
Class K9 DN350 pipe conforms to:
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ISO 2531:2009 / ISO 8180 for ductile iron pipes, fittings, accessories
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EN 545 & EN 598 (BS EN 545:2010, BS EN 598:2007) for drinking water and sewer mains
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AWWA C151 / C110 (ANSI A21.51 / A21.10) for U.S. potable-water applications
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ISO 9349:2017 for pre-insulated ductile iron systems
Compliance ensures global acceptance, system interoperability, and quality assurance.
Advantages
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High strength & ductility: Tensile strength ≥ 400 MPa, elongation ≥ 10 %
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Corrosion protection: Cement-mortar lining, zinc-bitumen coating; optional polyethylene sleeving
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Ease of installation: Modular joints reduce labor and excavation time
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Longevity & sustainability: 100 + years, high recycled content
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Cost-effective lifecycle: Lower maintenance and energy costs than alternative materials
FAQ
Q: Can Class K9 pipe handle seismic loads?
A: Yes—its ductility and restrained-joint options accommodate ground movements.
Q: What coatings are available?
A: Standard zinc-bitumen; optional polyethylene sleeving, epoxy, or polyurethane.
Q: How is joint leakage prevented?
A: Precision-cast bells, EPDM gaskets, and restrained joints ensure leak-tight seals.
Q: Are fittings and valves standardized?
A: Yes—compatible with AWWA C110, ISO 2531, EN 545 dimensions.
Case Studies
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Municipal water main upgrade (Huntsville, AL): Switching to ductile iron saved $17 million PV over 50 years at energy costs of 30 % of O&M budget.
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Trenchless river crossing (CA): HDD installation of DN350 K9 with restrained joints eliminated surface disruption and reduced installation time by 40 %.
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Wastewater treatment plant piping: Cement-mortar-lined DN350 K9 handled corrosive slurries for over 20 years with minimal maintenance.
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 | ….. |
