| What is ACIPCO Ductile Iron? The ideal of cast iron with ductility, long sought by metallurgists, was realized with the introduction of ductile iron in 1948. Acclaimed to be one of the most significant metallurgical developments in this century, ductile iron has had an increasing impact in many industries. Ductile iron has ductility -- as the name implies -- and, in addition, it has strength and impact resistance far greater than that of gray iron; yet it retains the proven corrosion resistance of gray iron, thus making it an ideal piping material.
American Cast Iron Pipe Company pioneered the development of ductile iron pipe and produced experimental casts of ductile pipe and fittings as early as 1948. The first shipment of ACIPCO Ductile Iron pipe was made in 1955. Production of ductile iron pipe has grown steadily, and it is now the predominant piping material for conveying water and other liquids.
Ductile iron is produced by treating molten low-sulfur base iron with magnesium under closely controlled conditions. The startling change in the metal is characterized by the free graphite in ductile iron being deposited in spheroidal or nodular form instead of flake form, as in gray iron. With the free graphite in nodular form, the continuity of the metal matrix is at a maximum, accounting for the formation of a far stronger, tougher, ductile material exceeding gray iron in strength, in ductility, and in impact characteristics by wide margins.
INT ACIPCO International Ductile Iron Pipe - Minimum...
ACIPCO Ductile Iron
Minimum Physical Properties for Ductile Iron Pipe |
| AWWA C151 |
ISO 2531 |
| These properties are verified by tensile samples from the wall of the pipe. |
Tensile Strength ... 60,000 psi |
... 420 N/mm2 |
| These properties are verified by tensile samples from the wall of the pipe. |
Yield Strength ... 42,000 psi |
... 300 N/mm2 |
| These properties are verified by tensile samples from the wall of the pipe. |
Elongation ... 10% |
... 10% |
EXHIBITS TREMENDOUS TENSILE STRENGTH. A pipe must be able to withstand severe stresses caused externally by shifting ground and heavy loads and internally by water pressure and water hammer. ACIPCO ISO Ductile Iron pipe has minimum strength requirements of 420 N/mm2 tensile strength, 300 N/mm2 yield strength, and 10% minimum elongation.
HAS GREAT BEAM STRENGTH. Ductile iron will bend or give considerably before it will ultimately fail. This characteristic is what makes its ductility so desirable. Ductile iron's ability to bend under load greatly increases its resistance to beam load.
WITHSTANDS SEVERE CRUSHING LOADS. Extreme traffic loads, heavy backfill, or earth movements caused by freezing, thawing, and soil swell pressures impose tremendous forces on buried pipes. Beam tests, free bend tests, and -- toughest of all -- ring tests, which determine the pipe's ability to resist concentrated loads, all demonstrate the superiority of ductile iron pipe.
IS CORROSION RESISTANT. Numerous laboratory and field tests have proved that ductile iron's corrosion resistance is equal to or greater than that of cast iron, which has served a number of U.S. utilities for more than 150 years with no external corrosion protection. In the majority of soils, ductile iron needs no external corrosion protection. In most areas of highly corrosive soil, simple, economical polyethylene encasement has provided excellent corrosion protection for the pipe.
HAS EXTREMELY HIGH IMPACT RESISTANCE. In test after test, ductile iron has exhibited tremendous impact resistance. Ductile's toughness makes it much less vulnerable to damage from improper handling or abnormal service conditions. And it stands up under heavy traffic conditions in unstable soil environments where other materials might fail due to the stresses caused by unusual loading.
DEMONSTRATES TREMENDOUS BURSTING STRENGTH. Ductile's tremendous bursting strength makes it ideally suited for high-pressure applications. Ductile's bursting strength also provides an additional safety factor against water hammer.
IS EASY TO INSTALL. Ductile iron is easy to install in the field. A wide variety of joints and standard fittings are available for every application. Ductile iron can be cut and direct-tapped in the field. And it requires no complex laying schedules or line-and-grade drawings.
IS VIRTUALLY MAINTENANCE FREE. Years of experience in operating systems throughout the world have proved that, once installed, ductile iron requires little, if any, maintenance over the life of the pipeline. Ductile's longevity can be witnessed in the outstanding service records of cast iron pipe over the past 150 years.
OFFERS IMPRESSIVE ENERGY SAVINGS. Ductile's high flow coefficient (C = 140) and generally larger-than-nominal inside diameters can result in increased flow capacity, lower head loss, lower pumping costs, and significant energy savings over the life of the pipeline.
ASSURED, PROVEN LONG LIFE. Historical records document the proven service for centuries of gray cast iron pipe. Extensive laboratory and field tests conducted by many authorities under various installation conditions prove the superiority of ductile iron for soil corrosion resistance over gray cast iron. The outstanding resistance of ductile iron pipe to soil corrosion has been verified by more than four decades of service. |
Above left: Photomicrograph showing graphite form in ductile iron.
Above right: Photomicrograph showing graphite form in gray iron.
Because of ductile iron's great beam strength and durability, it is ideally suited for challenging applications such as this pipe-on-supports installation.
Ductile iron pipe can withstand severe crushing loads. The ring test, shown above, determines a pipe's ability to withstand load over a relatively small area, as would occur in rocky terrain where the pressure of a single rock, plus all the backfill above it, could cause weaker materials to fail. A deflection gauge on the ring-crushing apparatus has been adjusted to accurately record deflection at specified load intervals.
Bottom of picture: This photograph was taken immediately after rupture occurred at the top of the ring. Note deflection of a full 50mm in this 200mm ductile iron pipe.
After receiving the full force of a two-ton weight dropped from a height of 9m, this 800mm ACIPCO Ductile Iron pipe was severely deformed, but did not fail. |
