Ductile iron pipe has long been recognized as the industry standard for modern water and wastewater pipelines. Nearly seven decades of field experience have proven its strength, durability, reliability and resilience in service.
Ductile Iron Pipe Joints
Joints for iron pipe have come a long way. About 550 years ago, the first cast iron pipes were made with flanged joints, using lead or leather gaskets. The bell and spigot joint, which was assembled by caulking yarn or braided hemp into the base of the annular bell cavity and then pouring molten lead into the remaining space inside the bell, was developed in 1785 and extensively used until the late 1950s. The roll-on joint was developed in 1937 and was used for roughly 20 years before its manufacture was discontinued. Assembly of this joint involved a compressed rubber gasket rolled under a restriction ring, followed by caulked, square-braided jute. The remainder of the joint was packed with a bituminous compound.
Today, the push-on and mechanical joints are the most prominent. The mechanical joint was developed for gas industry use in the late 1920s but has since been used extensively in the water industry. The push-on joint was developed in 1956 and represented an important advancement in the water distribution field.
Several special joints have been available for years. These include ball and socket for subaqueous crossings, grooved and shouldered, and numerous variations of restrained joints. There is a much wider variety of joints available for Ductile iron pipe than for any other piping material, providing greater flexibility and versatility in pipeline design and installation.
Flanged Ductile iron pipe and fittings have been an industry standard for plant piping for more than 65 years. The flanged ends of most pumps, valves, and other appurtenances are compatible with the flanged joints manufactured by DIPRA member companies. This article provides an overview of the applicable standards for flanged Ductile iron pipe and fittings and discusses the compatibility with other commonly used flange standards.
Iron pipe has proven strong and reliable for nearly 200 years in water and wastewater systems across North America and for nearly 350 years in Europe. The Ductile iron pipe industry continues to deliver outstanding service while constantly exploring innovative ways to improve its product, especially with regard to corrosion control.
While the PVC pipe industry claims iron pipe corrodes on the inside, problems associated with internal corrosion were alleviated decades ago with the popular (and now standard) use of cement-mortar linings.