Class K9 DN900 pipe carries PN 25 (2.5 MPa) service pressure, with a nominal wall thickness of 12.6 mm (T = K·(0.5 + 0.001·D)) and an external diameter of ~ 918 mm, giving it the strength and durability for major water, sewer, industrial, and fire-fighting mains—often lasting 100+ years in favorable soils, with 50–80 years in aggressive conditions. Installation uses push-on, restrained K-type, or self-restrained joints per ISO 2531, EN 545/598, ISO 4179, and ISO 8179; pricing for K9 ranges around USD 630–680 per m, with K7/K8 lower and K12 higher.
Application Scenarios
Class K9 DN900 ductile iron pipe is ideal for:
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Municipal potable water and raw water networks, ensuring high flow with minimal head loss over long distances.
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Gravity and rising sewer mains, plus stormwater drainage, where mechanical robustness and leak-proof joints are critical.
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Fire-fighting mains (hydrants, sprinklers) requiring surge resistance up to 40 bar when paired with restrained joints.
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Industrial effluent, mining, and large-scale irrigation, benefiting from the pipe’s high tensile strength (> 420 MPa) and ductility.
Service Life
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100+ years design life in benign soils, backed by lab and field data on K-class metallurgy.
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50–80 years in aggressive soils with standard corrosion protection (cement mortar lining, zinc/bitumen coatings, epoxy).
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Low total cost of ownership due to recyclability and minimal maintenance requirements.
Installation & Connections
Push-On (“Tyton”/T-Type) Joints
Gasketed EPDM (or SBR/NBR) joints allow quick, field-ready assembly, accommodate 5° deflection per joint in large-diameter runs, and maintain leak-free performance when installed per ISO 2531.
K-Type Restrained Joints
Mechanical restraints lock socket and spigot, resisting axial thrust from surge and vacuum conditions. Ideal for pre-test pressure verification prior to backfill.
Self-Restrained Joints
Clamped harnesses prevent joint separation up to PN 16, simplifying installations in tight trenches without separate restraint hardware.
Series Comparison & Pricing
| Class | Wall Thickness (mm) | Pressure (PN) | Relative Price |
|---|---|---|---|
| K7 | 7·(0.5+0.001·900)=9.8 | PN 10 | ~20–25% below K9 |
| K8 | 8·(0.5+0.001·900)=11.2 | PN 16 | ~15% below K9 |
| K9 | 9·(0.5+0.001·900)=12.6 | PN 25 | USD 630–680/m |
| K12 | 12·(0.5+0.001·900)=16.8 | PN 40 | ~30% above K9 |
Prices depend on order volume, coating options, and region; contact suppliers for firm quotes.
International Standards
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ISO 2531: Ductile iron pipes, fittings, accessories & joints for water pipelines.
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EN 545 / EN 598: European standards for drinking water and sewerage pipes.
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ISO 4179: Internal cement-mortar lining requirements.
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ISO 8179: External zinc + bitumen coating specifications.
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ISO 21053: Life-cycle analysis & sustainability evaluation.
Advantages
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High Tensile Strength & Ductility (> 420 MPa) stand up to ground movement and surge events.
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Exceptional Corrosion Protection via multi-layer linings/coatings, proven in aggressive soils.
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Fast, Leak-Free Assembly reduces installation time and labor costs.
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Environmentally Responsible: high recycled-iron content, fully recyclable at end-of-life.
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Global Interoperability ensures easy sourcing and compatibility across regions.
FAQ
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What is Class K9 for DN900?
Wall thickness = 9·(0.5 + 0.001·900) = 12.6 mm, PN 25 rating per ISO 2531. -
How long will DN900 K9 last?
100 years in benign soils; 50–80 years with standard corrosion protection in aggressive soils .
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Which joint suits high-rise or surge-prone systems?
K-type restrained joints provide axial restraint and zero-leak performance under pressure transients . -
What linings/coatings are standard?
Cement-mortar lining (ISO 4179); external zinc (≥ 130 g/m²) + bitumen (ISO 8179); optional fusion-bonded epoxy. -
Is it approved for potable water?
Yes—EN 545 compliance, internal cement lining and external coatings meet all drinking-water standards.
Case Studies
1. Rewa River Water Supply, Fiji
Although steel MSCL pipes (DN900) were chosen in this gravity-fed scheme, the project’s demand—40 ML/day for 360 000 residents under challenging terrain—illustrates the hydraulic performance required of large-diameter mains. Class K9 DN900 ductile iron pipes match or exceed these requirements with superior corrosion protection and durability.
2. Port of Tampa Corrosion Challenge, USA
A 35-year-old ductile iron line suffered severe leaks in aggressive soils, prompting replacement with plastic mains. This underscores the critical importance of robust coatings (zinc + bitumen + epoxy) and linings in K9 installations to avoid similar failures.
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 | ….. |
