CAST IRON PIPE

Cast iron (grey cast iron) is a historical type of pipe manufactured in the 19th and 20th centuries that is used as pressure pipe for transmission of water and sewage. Cast iron pipe was gradually superseded by ductile iron pipe, which is a direct development, with most existing manufacturing plants transitioning to the new material during the 1970s and 1980s.

Most grey cast iron pipes that are in service were manufactured by either pit casting or spin casting. The earliest cast iron pipes were vertically pit-cast grey iron. In the early nineteenth century, the first pit-cast iron pipes in the U.S. were imported, but from 1830, local production became more widely established. Pit-cast iron pipes were manufactured and installed until the 1940s. There is currently almost no new manufacture of cast iron pipe.

Advantages
  • Thicker wall than ductile iron or steel
  • Similar rate of corrosion to ductile iron and steel
  • Most pipes after 1950 supplied with cement mortar lining or retrofitted
Disadvantages
  • No elastic behavior and lower mechanical strength
  • Prone to external and internal corrosion in aggressive conditions
  • Older pipes having caulked joints with little flexibility
  • Often no external protection
  • Most pipes unlined before 1960
  • Manufacturing defects including variations in wall thickness
  • Poor records

MAIN FORMS OF FAILURE IN CAST IRON PIPES

Form of Failure Causes of Failure Indicators of Failure
External pitting and graphitization corrosion Lining damage, wall loss from internal pitting, graphitization, leaks, external loads, and pressure variations
Break Failure External pitting and graphitization corrosion Coating damage, wall loss from external pits, graphitization (hard to detect), leaks, external loads, and pressure variations
Manufacturing defects Cracks in body or bell
Movements from thermal, seismic, external loading Joint leaks, poor bedding, and pipe movements
Structural Failure Thermal contraction, poor support leading to movement, internal pressure Circumferential cracks, frost regions, leaks, pipe movements, and expansive clays
Internal pressures, external loadings, thermal stresses Longitudinal cracks, frost regions, and changed internal/external loads
Leadite joints Cracking at bell
Leaks Loss of soil support and bending failure Leak noise, wet areas, and pressure variations