Natural gas distributed in the Netherlands contains very little sulphur.the sulphur content is currently below 10 milligrams per cubic metre.Most o fthe sulphur which is present comes from the trtrahydrothiophene added to the gas as odorant.Prior to 1994,however,a sulphur content of up to 150 milligrams per cubic metre of naturla gas was permitted.the effect of such a high sulphur content on the corrosion of materials and different ytpes of joint in condensing appliances was unknown.to investigate this effect,tests were carried out using naturla gas with the high sulphur content as well as with today's low sulphur content.For this purpose,a test rig was built enabling the performnce of different materials to be compared under simulated practical conditions.The results obtained over a test period of twelve months were extrapolated over the desing life of fifteen years.
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