The main products are cast pipe fittings which are divided into resin-boned sand and steel casting green sand, diameter DNDN DIN EN Flange connections of ductile cast iron for fresh water supply and waste water disposal. Integral flange cross, all sockets cross. Flange socket, flanged spigot, double flanged collar, double socket reducer, double flanged reducer, blind pipe, bell end, double flanged pipe.
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Ductile iron pipe is pipe made of ductile cast iron commonly used for potable water transmission and distribution. In highly corrosive environments loose polyethylene sleeving LPS to encase the pipe may also be used.
Life expectancy of unprotected ductile iron pipes depends on the corrosiveness of soil present and tends to be shorter where soil is highly corrosive. Ductile iron pipe manufactured in the United States has been certified as a sustainable product by the Institute for Market Transformation to Sustainability.
Ductile iron pipe is sized according to a dimensionless term known as the Pipe Size or Nominal Diameter known by its French abbreviation, DN.
This is roughly equivalent to the pipe's internal diameter in inches or millimeters. However, it is the external diameter of the pipe that is kept constant between changes in wall thickness, in order to maintain compatibility in joints and fittings.
Consequently, the internal diameter varies, sometimes significantly, from its nominal size. Although both metric, European and Australian are not compatible and pipes of identical nominal diameters have quite different dimensions.
European pipes are sized to approximately match the internal diameter of the pipe, following internal lining, to the nominal diameter. ISO maintains dimensional compatibility with older German cast iron pipes. Older British pipes, however, which used the incompatible imperial standard, BS 78, require adapter pieces when connecting to newly installed pipe. Coincidentally, the British harmonization with European pipe standards occurred at approximately the same time as its transition to ductile iron, so almost all cast iron pipe is imperial and all ductile pipe is metric.
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Therefore, the inner diameters of lined pipe differ widely from the nominal diameter, and hydraulic calculations require some knowledge of the pipe standard.
Individual lengths of ductile iron pipe are joined either by flanges, couplings, or some form of spigot and socket arrangement.
Flanges are flat rings around the end of pipes which mate with an equivalent flange from another pipe, the two being held together by bolts usually passed through holes drilled through the flanges. A deformable gasket, usually elastomeric, placed between raised faces on the mating flanges provides the seal.
Flanges are designed to a large number of specifications that differ because of dimensional variations in pipes sizes and pressure requirements, and because of independent standards development. In the U. In the European market flanges are usually welded onto the pipe. A flanged joint is rigid and can bear both tension and compression as well as a limited degree of shear and bending. It also can be dismantled after assembly. Due to the rigid nature of the joint and the risk of excessive bending moment being imposed, it is advised that flanged pipework is not buried.
Spigot and sockets involve a normal pipe end, the spigot, being inserted into the socket or bell of another pipe or fitting with a seal being made between the two within the socket.
Normal spigot and socket joints do not allow direct metal to metal contact with all forces being transmitted through the elastomeric seal. They can consequently flex and allow some degree of rotation, allowing pipes to shift and relieve stresses imposed by soil movement. The corollary is that unrestrained spigot and socket joints transmit essentially no compression or tension along the axis of the pipe and little shear.
Any bends, tees or valves therefore require either a restrained joint or, more commonly, thrust blocks, which transmit the forces as compression into the surrounding soil. A large number of different socket and seals exist. The most modern is the 'push-joint' or 'slip-joint', whereby the socket and rubber seal is designed to allow the pipe spigot to be, after lubrication, simply pushed into the socket. Push joints remain proprietary designs. Also available are locking gasket systems.
These locking gasket systems allow the pipe to be pushed together but do not allow the joint to come apart without using a special tool or torch on the gasket. The earliest spigot and socket cast iron pipes were jointed by filling the socket with a mixture of water, sand, iron filings and sal-ammoniac ammonium chloride. A gasket ring was pushed into the socket round the spigot to contain the mixture which was pounded into the socket with a caulking tool and then pointed off.
This took several weeks to set and produced a completely rigid joint. Such pipe systems are often to be seen in nineteenth century churches in the heating system.
In the late s, ductile iron pipe was introduced to the marketplace, featuring higher strength and similar corrosion resistance compared to cast iron. Like most ferrous materials, ductile iron is susceptible to corrosion, therefore its useful life depends on the impact of corrosion.
Over the last years, the average thickness of iron pipes has decreased due to increased metal strength,  through metallurgical advancements as well as improved casting technique.
The potential for corrosion, leading to pipe failure, is significantly impacted by the corrosivity of soil. Unprotected pipes in highly corrosive soil tend to have shorter lifespans. In the United States, the American National Standards Institute and American Water Works Association have standardized the use of polyethylene sleeving to protect ductile iron pipe from the effects of corrosion.
The only environment for which the analysis found the polyethylene sleeving did not provide effective corrosion control was for "uniquely severe" environments, a classification of a rare but extremely corrosive environment. The analysis found that a lifespan of 37 years could be expected in these "uniquely severe" environments. Pipes manufactured under International Organization for Standardization ISO standards are typically coated with zinc, to provide protection against corrosion.
In instances of more aggressive soils, polyethylene sleeving is installed over the zinc coated pipe to provide added protection. Cathodic protection may also be used to prevent corrosion and tends to be advocated by corrosion engineers for pipes in corrosive soils as an addition to external dielectric coatings. Engineers and water authorities in the United States are divided on the use of different coatings or cathodic protection.
Mixed results have been found for all methods of protection. However, this may be due to the impact of variations in local soil corrosiveness and temperature or by damage occurring during installation, which can impact effectiveness of protective coatings. Ductile iron pipe is somewhat resistant to internal corrosion in potable water and less aggressive forms of sewage. However, even where pipe material loss and consequently pipe wall reduction is slow, the deposition of corrosion products on the internal pipe wall can reduce the effective internal diameter.
A variety of linings are available to reduce or eliminate corrosion, including cement mortar, polyurethane and polyethylene. Of these, cement mortar lining is by far the most common. Polyurethane is an option offered as an internal lining for ductile iron pipes in lieu of cement mortar. However, as PUR provides only passive protection it becomes vitally important that the coating is not damaged during handling and installation. Manufacturers will specify strict handling, transport and installation procedures to ensure PUR coatings are protected.
If pipes are deformed Polyurethane's elasticity, does in some situations allow the coating to remain intact. Corrosion Experts. Polyurethane coatings were first used in Polyurethane is a thermosetting plastic with no solvents, with a three-dimensionally linked molecular structure giving it mechanical stability.
The polyurethane lining used for internal coating has the following standard properties is standardised by EN Ductile iron pipes, fittings and accessories - Internal polyurethane lining for pipes and fittings - Requirements and test methods. The predominant form of lining for water applications is cement mortar centrifugally applied during manufacturing. The cement mortar comprises a mixture of cement and sand to a ratio of between and For potable water, portland cement is used; for sewage it is common to use sulfate resisting or high alumina cement.
Cement mortar linings have been found to dramatically reduce internal corrosion. A DIPRA survey has demonstrated that the Hazen-Williams factor of cement lining remains between and with only slight reduction with age.
Unprotected ductile iron, similarly to cast iron, is intrinsically resistant to corrosion in most, although not all, soils.
Nonetheless, because of frequent lack of information on soil aggressiveness and to extend the installed life of buried pipe, ductile iron pipe is commonly protected by one or more external coatings.
In Europe, standards recommend a more sophisticated system of directly bonded zinc coatings overlaid by a finishing layer be used in conjunction with polyethylene sleeving. It was employed more widely in the U. Loose Polyethylene Sleeving LPS remains as one of the most cost effective corrosion protection methods available today with a proven track record for reliability and effectiveness.
LPS comprises a loose sleeve of polyethylene that completely wraps the pipe, including the bells of any joints. The sleeving inhibits corrosion by a number of mechanisms. It physically separates the pipe from soil particles, preventing direct galvanic corrosion. By providing an impermeable barrier to ground water, the sleeve also inhibits the diffusion of oxygen to the ductile iron surface and limits the availability of electrolytes that would accelerate corrosion. It provides a homogeneous environment along the pipe surface so that corrosion occurs evenly over the pipe.
The sleeve also restricts the availability of nutrients which could support sulfate-reducing bacteria , inhibiting microbially induced corrosion. LPS is not designed to be completely water-tight but rather to greatly restrict the movement of water to and from the pipe surface.
An improperly installed sleeve that continues to allow the free flow of ground water is not effective in inhibiting corrosion. Polyethylene sleeves are available in a number of materials. The latter may or may not be reinforced with a scrim layer. Polyethylene sleeving does have limitations. In Europe and Australia, ductile iron pipe is typically manufactured with a zinc coating overlaid by either a bituminous, polymeric, or epoxy finishing layer.
No current AWWA standards are available for bonded coatings zinc, coal tar epoxy, tape-wrap systems as seen on steel pipe for ductile iron pipe, DIPRA does not endorse bonded coatings, and AWWA M41 generally views them unfavourably, recommending they be used only in conjunction with cathodic protection.
Zinc coatings are generally not employed in the U. This coating is not intended to provide protection once the pipe is installed. They protect against corrosion from the outside and inside, and also protect the product from contamination. The coating is an emulsion manufactured using asphaltene and water primarily, with other raw materials according to the manufacturer's specifications.
They came in use in the early s, replacing coatings based on dangerous and environmental harmful solvents, such as benzenes, toluenes, hexanes and other volatile organic compounds.
This European Standard specifies the requirements and associated test methods applicable to ductile iron pipes, fittings, accessories and their joints for the construction of pipelines outside buildings: - to convey different types of water e. NOTE 1 This does not preclude special arrangements for the products to be used at higher temperatures. This European Standard covers pipes and fittings cast by any type of foundry process or manufactured by fabrication of cast components, as well as corresponding joints and accessories, in a size range extending from DN 40 to DN 2 , inclusive. This European Standard specifies requirements for materials, dimensions and tolerances, mechanical properties and standard coatings of ductile iron pipes and fittings. It also gives performance requirements for all components including joints. Joint design and gasket shapes are outside the scope of this standard. In addition, reference is made to the performance requirements of couplings, flange adaptors and saddles manufactured for use with ductile iron pipes and fittings.
Ductile iron pipe
BS EN provides best-practice requirements and test methods for ductile iron pipes, pipe fittings, accessories and their joints for the construction of pipelines outside buildings. This can be to transport different types of water with or without pressure, below or above ground. This standard applies to pipes, fittings and accessories with socketed, flanged or spigot ends and internal or external coatings. It also gives performance requirements for couplings, flange adaptors and saddles that are manufactured to use with ductile iron pipes and fittings. BS EN looks at the technical requirements, pressure class and dimensional tolerances for ductile iron pipes and their fittings. It also gives an in-depth explanation of coatings and linings, as well as the marking of pipes, fittings and accessories.
Ductile iron pipe is pipe made of ductile cast iron commonly used for potable water transmission and distribution. In highly corrosive environments loose polyethylene sleeving LPS to encase the pipe may also be used. Life expectancy of unprotected ductile iron pipes depends on the corrosiveness of soil present and tends to be shorter where soil is highly corrosive. Ductile iron pipe manufactured in the United States has been certified as a sustainable product by the Institute for Market Transformation to Sustainability. Ductile iron pipe is sized according to a dimensionless term known as the Pipe Size or Nominal Diameter known by its French abbreviation, DN. This is roughly equivalent to the pipe's internal diameter in inches or millimeters.
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