Pipe producer's fire warning about plastic

A powerful plea for cast-iron to be used instead of plastic for sanitary drainage systems in public buildings has been made by international pipework suppliers Saint Gobain, Mary Munroe reports.

As manufacturers of cast-iron pipes, Saint Gobain might be accused of special pleading, but recent tests in Germany have demonstrated that both plastic based and HDPE systems are vulnerable to fire. The company points out that in the event of fires, plastic based materials swiftly melt and can spread fires both up and down the building.

The tests, commissioned by IZEG, the German association for cast iron pipe manufacturers, and carried out by MPA North-Rhine Westphalia Laboratory, were based on cast iron, PVC, HDPE and twin-walled PVC sanitary pipe systems. Each of the plastic based systems was fitted with the recommended intumescent fire collars.

Dramatic video footage taken during the tests clearly demonstrated that within three minutes the PVC system had melted, within 12 the HDPE also had disintegrated and within 15 the twin-walled system was beginning to suffer damage. At the end of 35 minutes only the cast iron system was intact.

Equally disturbing, dripping plastic had bypassed the fire collars and ignited a lower floor, and dense smoke was filling the area. Alan Gwilliam, Saint Gobain Pipelines' market director for Building Services, Industrial and Maintenance, said that the toxicity of the fumes from burning plastic was a further reason for using cast iron. He cited fires at Dusseldorf airport and the MGM Grand in Las Vegas as situations where fumes had significantly contributed to deaths.

Rod Green, a consultant public health engineer, supported the use of cast iron drainage systems, especially for buildings where large numbers of people might need to be evacuated in the event of a fire.

Cost was often a consideration, but cast iron's fire resistance and non-toxicity provided an essential safety factor. An added advantage was that the cast-iron pipework could, in his experience, often be refurbished after a fire where plastic had to be completely replaced.

One problem raised was that cast iron pipework would heat up, but Alan Gwilliam said that Saint Gobain had devised a non-conduction system which had been tested up to 1000 oC without the pipework melting.

Questioned on comparative costs of plastic systems, he said cast iron installed cost was roughly 25% more, but with the fire risk in public buildings now being given a higher profile, the demonstrable superior performance of cast iron systems must make it the material of choice.

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