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News

Optimal internal protection of water mains

Bayer MaterialScience AG : 10 May, 2004  (Company News)
For some years, a project has been ongoing in South West England to renew the water mains, parts of which date back to Victorian times. The city of Plymouth in the county of Devon serves as a case study.
In an initial project phase, pipe with an interior diameter of 36 inches (91.4 centimeters) was rehabilitated and coated with a polyurethane system formulated using raw materials from Bayer MaterialScience AG. The project was honored by the UK Society for Trenchless Technology (UKSTT) in 2003 as the best large renovation project. Its success was due in large measure to the high-performance coating system, the innovative application technology and the good collaboration between the project partners: raw materials supplier Bayer MaterialScience, coating formulator E. Wood, applicator T J Brent Ltd. and client South West Water Ltd.

Due to their outstanding properties, polyurethane coatings have largely replaced the epoxy systems previously used in this application. For the project described here, E. Wood's Copon Hycote 169, a 2K polyurethane system, was chosen. This is based on aliphatic Desmodur« N supplied by Bayer MaterialScience and special amines. 'Apart from the excellent anti-corrosion properties, one key advantage of this coating is its rapid curing, which shortens the interruption to the water supply,' says Dr. Malte Homann, an expert for anti-corrosion coatings at Bayer MaterialScience. 'Also, the surface of the cured coating is extremely smooth; this prevents the formation of deposits and the growth of algae so water can flow through the pipe unhindered.' The environmentally friendly and solvent-free coating system fulfils all U.K. drinking water regulations and has already been approved in other countries, both in Europe and elsewhere.

The large main in Plymouth with an interior diameter of 36 inches and a length of 1.5 kilometers supplies some 47,000 properties and the Devonport Royal Naval Dockyard in Plymouth. In the 80 years since the main was laid in 1924, homes and other buildings have been built on the land above it, making it difficult or even impossible to access the main directly. However, thanks to a clever technology, it was possible for T J Brent Ltd to complete the rehabilitation project in just nine weeks.

Rehabilitation involves various stages. Firstly, the interior of the pipe is cleaned to remove corrosion products. Once the pipe is completely clean, the polyurethane coating is applied in a thickness of 1.5 millimetres. This is done using a specially developed sled with guide tracks that position the rotary spray system exactly in the middle of the pipe. The device is designed such that the entire pipe - including curved sections - can be coated with a uniform thickness in a single operation. The coating cures quickly. A mobile camera unit is then used for the final quality check.

Using this process, South West Water in conjunction with its contracting Partners TJ Brent and Balfour Beatty Utilities has already rehabilitated 753 kilometers since April 2000 to March 2004 of water mains throughout Devon and Cornwall using Copon Hycote 169. In comparison replacement work undertaken in this region in the same period is 413 kilometers. Over the next six years, the total will reach about 3,850 kilometers, approximately 70 percent of the South West Water's statutory undertaking with the Drinking Water Inspectorate in improving water quality.
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