By Sheila Kennedy
The quest for the perfect pipe continues. Corrosion, erosion, abrasion and chemical attack are threats to pipe life and production reliability. The high cost of locating and repairing a leak, or excavating and replacing pipes, is exacerbated by costly downtime and environmental hazards. The entire supply chain is affected when degraded pipes disrupt production and product flow.
Fortunately, advancements are increasing the service life of process piping, and options are expanding for in situ repairs.
Can damaged pipe be repaired? Slip lining may be a repair option for internal or external corrosion. This involves feeding new pipe within an existing pipeline, and filling the void between the old and new pipes with grout. Weakened pipes can be reinforced with a fiberglass cloth and resin composite that is essentially taped to the outer wall.
What can be done to extend life? Cathodic protection (CP) is a well-known way to mitigate corrosion by substituting a sacrificial metal to corrode in place of the pipeline. However, stray electrical currents can interfere with the effectiveness of CP and must be monitored.
Surface enhancement coatings, such as a paint-on epoxy primer, are effective, but damage to the coating caused during pipe installation or by soil stresses could diminish the benefits.
Glass linings can be added for abrasion and chemical resistance. Once the internal surface is cleaned and prepared, the glass lining is applied and cured.
What alternative materials provide resistance? Fiberglass-reinforced pipe offers resistance to corrosion and chemical degradation without linings, coatings or cathodic protection. The pipe is constructed using glass fiber reinforcement and thermosetting resin. Fiberglass pipe manufactured with the more common filament-wound method now competes against those manufactured by a centrifugal casting process that provides greater strength at equal wall thickness.
Plastic pipe's long life and low maintenance make it another cost-effective piping alternative. Polyethylene pipes can be laid stand-alone or inserted as a liner, and are suitable for many process industry and utility applications.
Where can I find more information? Piping Design Central is a good starting point for anyone interested in piping design issues, trends and standards.
The Pipe Fabrication Institute initiates research, proposes and maintains standards, and provides networking and educational opportunities for members.
For more information, see:
E-mail Contributing Editor Sheila Kennedy, Additive Communications, at Sheila@addcomm.com.