Steel pipe

The first methods for producing steel pipe were introduced in the early 1800s, and they have steadily evolved into the modern processes we use today.

Large diameter steel pressure pipes for water and wastewater applications are typically made with carbon steel and installed as buried assets. Steel pipe can be made using three main methods:

Seamless

Hot steel is pushed through a die to create the pipe shape. Diameters of up to 20” (500mm) can be made this way. Expensive but the most reliable.

Welded

A sheet of steel is wrapped around a form then welded at the seam. Less expensive but not as reliable as seamless for high-pressure situations.

Casting Mold

Hot liquid steel is poured into a mold. Not very common and as reliable as seamless. The primary benefit of steel pipe is its strength. These pipes don’t crack under most impacts and can operate under high pressure. Under abnormal loads, steel will bend, rather than break.

Advantages

  • High tensile strength
  • High compressive strength
  • Range of corrosion protection systems
  • Wide range of diameters and wall thickness
  • Welded joints give continuity

Disadvantages

  • Prone to external corrosion
  • Electrolysis prone
  • Jointing requires skilled welders
  • Internal/external corrosion protection systems add to price
  • Coatings and linings can get damaged during installation and by third parties

Main forms of failure in steel pipes

Break Failure
Causes of failure
Indicators of failure
Pitting corrosion weakening wall Damage to coating/linings, wall loss, pitting, and leaks
Longitudinal cracking
Causes of failure
Indicators of failure
Thinning from general corrosion, and areas of pitting corrosion Graphitization, groups of pitting, and wall loss
Pipe bursts
Causes of failure
Indicators of failure
Third party damage Construction activity