Ductile iron pipes
Ductile iron (spheroidal graphite iron) pipes and matching fittings for pressure water supply and sewerage: socket pipes DN80–DN1200 in classes K9 and C40 from Chinese foundries casting to ISO 2531, EN 545 and GB/T 13295.
2
items with size and weight tables
6
standards for rolling and acceptance
Items in this category
Socket pipes and fittings in ductile (spheroidal graphite) iron, DN80–DN1200
What it is and how it is supplied
Ductile iron is produced by treating liquid iron with magnesium: the graphite in the casting forms spheroidal nodules instead of flakes, and the metal stops being brittle. In strength and ductility ductile iron approaches steel — tensile strength not less than 420 MPa, elongation of pipes not less than 10 % — while keeping the resistance of cast iron to corrosion in soil and water. Pipes are cast centrifugally in metal or sand moulds and annealed to a ferritic structure; fittings are cast in sand moulds.
Details
For water supply, pipes and fittings are governed by ISO 2531 and EN 545, for sewerage by ISO 7186 and EN 598; in the CIS GOST ISO 2531-2012 applies, and Chinese plants work to GB/T 13295. Wall thickness is set by class: K9 and K10 by a formula from the diameter, C25, C30 and C40 by the allowable operating pressure in bar. The standard protection is a cement mortar lining inside and metallic zinc with bituminous varnish outside; zinc-aluminium is used for aggressive soils, and a high-alumina cement lining for sewerage.
The bureau finds a plant with centrifugal casting and its own laboratory, agrees the specification — DN, class, joint type, coatings, sealing gaskets — and inspects the batch at the plant before shipment: measurements, checking the mill test certificate (MTC) against the heat number, marking, stacking and packing. The batch is sized to your volume — send us the specification. Rejects recorded in the inspection report are replaced; the replacement is supplied by the manufacturing plant under its contract with the bureau.
Grade equivalents
Equivalents are the nearest, not identical: the exact grade and standard are written into the contract.
| GOST | GB (China) | ASTM | EN | Note |
|---|---|---|---|---|
| VCh45 (GOST 7293-85) | GB (China)QT450-10 (GB/T 1348) | ASTM65-45-12 (ASTM A536) | ENEN-GJS-450-10 (EN 1563) | NoteNearest equivalents by strength and elongation. Pipe standards specify mechanical properties directly; the casting grade in the plant certificate is for reference. |
| K9 (GOST ISO 2531-2012) | GB (China)K9 (GB/T 13295) | ASTM— | ENK9 (EN 545:2006) | NoteWall thickness class: e = 9·(0.5 + 0.001·DN), not less than 6 mm. In the ISO 2531:2009 and EN 545:2010 editions pressure classification became the primary one, K9 is retained for continuity. AWWA C151 classifies by pressure; the thicknesses do not match. |
| C40 (GOST ISO 2531-2012) | GB (China)C40 (GB/T 13295-2019) | ASTM— | ENC40 (EN 545:2010) | NoteClass by allowable operating pressure of 40 bar. At the same DN the C40 wall is thinner than K9; the classes are not equated — the specification names one class and one edition of the standard. |
| Socket with rubber ring (GOST ISO 2531-2012) | GB (China)Socket T-type (GB/T 13295) | ASTMPush-on (AWWA C111/A21.11) | ENTyton / push-on (EN 545) | NoteTyton is a trade name of the joint. Socket seating dimensions are set by the standard, but the groove and gasket profile differs between plants: gaskets are ordered from the pipe manufacturer. |
| — | GB (China)GB/T 21873 | ASTM— | ENEN 681-1 / ISO 4633 | NoteEPDM sealing gaskets for drinking water. Gasket requirements are checked against EN 681-1 and ISO 4633, which GOST ISO 2531-2012 references. |
| — | GB (China)GB/T 17457 | ASTMAWWA C104/A21.4 | ENISO 4179 / EN 545 | NoteCement mortar lining. Nominal thickness to ISO 4179: 3 mm for DN80–DN300, 5 mm for DN350–DN600, 6 mm for DN700–DN1200. |
| GOST 33259-2015 (PN10, PN16) | GB (China)GB/T 17241.6 | ASTMASME B16.1 (Class 125) | ENEN 1092-2 (PN10, PN16, PN25) | NoteFlange connection dimensions PN10 and PN16 to EN 1092-2 and GOST 33259 coincide for most DN and are checked against the drawing. ASME B16.1 has a different bolt-hole pattern and does not mate with EN flanges. |
Equivalents are the closest match, not identical: chemistry and tolerances differ between standards. The exact grade and standard are written into the contract.
Buyer questions
What to check in the plant's mill test certificate (MTC) for ductile iron pipes
Heat and batch number — the same on the pipe and in the certificate; standard and class (K9 or C40) — the same as in the contract; mechanical properties: tensile strength not less than 420 MPa, elongation not less than 10 %, hardness not more than 230 HB; the result of the works hydrostatic test of each pipe; cement mortar lining thickness and zinc weight per square metre; type and material of the sealing gasket. A certificate without a heat number or with a different edition of the standard is returned to the plant before shipment.
How class K9 differs from C40 and what to write in the specification
K is a wall thickness class: e = K·(0.5 + 0.001·DN); for K9 and DN300 that is 7.2 mm. C is a class by allowable operating pressure in bar: a C40 pipe is rated for 40 bar, the wall is calculated from the pressure and at the same DN comes out thinner than K9. Both systems run in parallel in the ISO 2531:2009 and EN 545:2010 editions. In the specification name one class and one edition of the standard — thickness, weight and the works test of the batch are derived from them.
How the weight and volume of a batch are calculated
Ductile iron pipes are counted in pieces and metres; weight is taken from the standard's table for the class — barrel weight per metre plus socket weight — not from the steel-product formula, since the density of cast iron is 7.05 g/cm³. Fittings are counted in pieces per the schedule, weight per the plant catalogue. For transport the volume is calculated: the number of packages and the transport depend on DN and length, not on tonnage alone. The batch is sized to your volume — send us a specification with DN, class, length, joint type and coatings.
What the bureau's inspector checks at the plant before shipment
The spigot outside diameter with a circumferential tape, wall thickness at the end face with a calliper, thickness along the barrel with an ultrasonic thickness gauge; cement lining thickness and absence of cracks and delamination; the socket and sealing groove; the cast marking — plant mark, DN, class, year; the heat number on the pipe against the certificate; the full set of gaskets and lubricant; stacking on bearers before loading. The result is an inspection report with photographs.
Are pipes and fittings from different plants compatible
In connection dimensions — yes: the spigot outside diameter and socket seating dimensions are set by the standard, flanges to EN 1092-2. In the sealing gasket — no: each plant has its own groove and gasket profile, and another plant's gasket does not fit the socket. The bureau orders pipes, fittings and gaskets from one manufacturing plant or agrees compatibility with the plants in writing before the contract.
Price request
Send your specification and we will quote your batch
Price depends on grade, size, tonnage and delivery terms on the day of contract.
Request received