Exhumation triumph

The exhumation of an ageing iron drinking water pipe has demonstrated the efficacy of an in situ lining product developed by 3M. Once lined, returned-to service mains are routinely exhumed to sample the effectiveness of the lining application.

The results are added to the lining records for that area. In this instance a 125mm diameter cast iron water main in the north of England, estimated to have been in service for around 50 years, had been treated two years previously.

3M Scotchkote Rapid Setting Polymeric Lining 169HB had been used to address significant water quality issues.

A section of this main, buried underneath a grass verge adjacent to a main highway, was selected for retrieval so the lining could be inspected and its condition assessed. The water supply to the main was turned off, but the main remained charged with water during excavation. Once a length of pipe had been exposed to reveal a jointed section, the pipe was cut either side of the spigot and socket joint to enable recovery of the joint section. A sledgehammer was then used to remove the cast iron pipe between the cut sections and expose the lining.

Despite the aggressive nature in which the pipe was removed, the lining survived intact. There was also no evidence of water having permeated the lining, according to 3M.

The removed section of lining showed that the original application process, using specialist lining equipment to treat the pipe in situ, had been successful in creating a smooth internal layer with an even material thickness which faithfully followed the internal geometry of the pipe. No defects were found within the pipe, even after the aggressive recovery process, clearly showing the strength and suitability of the product for in situ water pipe lining.

Carl Bradley of 3M’s Corrosion Protection Products division explains: “After many years and even decades in service, the insides of cast iron pipes can become clogged with minerals and other contaminants, with potentially major impact on water quality. They are also more prone to physical failures as they age.

“In situ lining has become established as a reliable and cost-effective alternative to excavation and replacement of entire mains – and this example shows how modern lining equipment and products are able to deliver effective and long-lasting protection.”