Class K7 DN200 ductile iron pipe combines a 200 mm (8″) nominal diameter with a working pressure of 7 bar (≈100 psi), making it well suited for medium‑pressure water and wastewater networks. Properly installed with cement‑mortar lining, zinc external coating, and polyethylene encasement, it can achieve an expected lifespan exceeding 100 years in benign soils or up to 110 years under evolved laying practices. Available in standard 6 m lengths with push‑on, mechanical, or restrained joints, it balances rapid installation with robust performance across diverse terrains.
Application Scenarios
Ductile iron’s high strength and ductility support urban water distribution, carrying potable water under steady pressures with minimal friction loss. It excels in pressure sewer systems, where standard classes handle hydraulic transients and surge pressures common at pump stations. For subsea or river crossings, the boltless ball‑and‑socket joint offers flexibility and restraint against joint separation under subaqueous conditions. Trenchless installations via horizontal directional drilling leverage restrained-flexible joints to replace mains without extensive excavation.
Service Life
Laboratory tests and field data indicate ductile iron pipes can last over 100 years when protected by cement lining and sleeve encasement. In unprotected or highly corrosive soils, lifespans may range from 21 to 40 years, underscoring the value of modern corrosion‑control measures.
| Protection Level | Estimated Service Life |
|---|---|
| Cement‑mortar lining + PE encasement | ≥ 100 years |
| Zinc coating only | ≈ 50 years |
| Unprotected in aggressive soils | 21–40 years |
Installation and Connections
Push‑on (T‑type) joints use elastomeric gaskets to achieve quick, leak‑tight assemblies with up to 5° angular deflection per joint. Proprietary restrained joints eliminate thrust blocks, cutting excavation and labor costs in thrust‑prone installations. In highly corrosive soils, V‑Bio® enhanced polyethylene encasement over zinc‑coated pipes further mitigates external corrosion.
International Standards
Class K7 DN200 pipes conform to ISO 2531 for water applications and ISO 4179 for cement‑mortar lining. They also meet EN 545 for potable water, EN 598 for sewerage, and AWWA C150/C151 for centrifugally cast ductile iron pipes in North America.
Price Comparison with Other Series
Indicative pricing for DN200 pipes (USD per meter, subject to volume and coating options):
Key Advantages
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High mechanical strength: Tensile ≥ 420 MPa, yield ≥ 300 MPa, elongation ≥ 10%.
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Robust corrosion resistance: Internal cement‑mortar lining and external zinc/bitumen coatings extend life in varied soils.
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Hydraulic efficiency: Smooth linings minimize head loss, reducing pumping costs over decades.
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Joint flexibility: Push‑on and restrained joints accommodate ground movement and seismic activity without leakage.
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Sustainability: Made from > 90% recycled material; fully recyclable at end‑of‑life.
Frequently Asked Questions
Q1: What defines “Class K7”?
A1: “K7” indicates a nominal working pressure of 7 bar (≈100 psi) per ISO 2531 designations.
Q2: Why choose DN200?
A2: DN200 (200 mm) is a globally standard size that balances high throughput for trunk mains with manageable handling and fitting availability.
Q3: How is corrosion controlled?
A3: Standard cement‑mortar lining, zinc or bitumen coatings, and optional polyethylene sleeve encasement per ANSI/AWWA C105 substantially mitigate corrosion.
Q4: Which joint types are available?
A4: Push‑on, mechanical (MJ), and self‑restrained joints allow contractors to optimize speed, cost, and thrust‑resistance per project needs.
Case Studies
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Chiba Prefecture landslide (Japan, 2004): An NS‑type DN200 ductile iron pipeline survived a road collapse with zero damage, maintaining uninterrupted water service
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Arizona PVC ban (USA): Eight major Arizona water utilities require ductile iron (often Class K7) over PVC in new distribution mains, prioritizing life‑cycle reliability.
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 | ….. |
