Industrial & Chemical Process Piping # 1970 Southampton
In the early development of plastics for pipelines, particularly those that were to be employed in the transmission of corrosive fluids, it very soon became apparent that it would be necessary to control the flow of the fluids with valves constructed of material similar to that of the pipeline instead of with metal bodied valves that were either rubber or glass lined to combat corrosion. Various materials have been used, and indeed still are used, for fittings and pipe for the industrial field, but the earliest developments of valves were in the material polyvinylchloride - PVC for short.
The angle seat valve was one of the earliest to appear, and was first made by fabricating, that is to say by using tube and solid bar from which parts were machined and subsequently welded. The labour content in manufacturing such valves was of course very expensive, and because of this it was not long before the body of this particular type of valve began to be moulded in thermoplastics. Then, as experience increased with the usage of such items, other mechanical parts that were previously machined were manufactured by the moulding process, resulting in considerable improvement in performance and appearance. As time went on, PVC became recognised as a material in its own right; today, components tend to be desiqed around the material and not as slavish copies of similar valves made in metal. This valve - the angle seat valve - is offered for sale today in Normal Impact PVC, polypropylene and ABS.
Author(s) : Young, Thomas, Marshall
Within the Water Industry in England and Wales, there is an estimated length of 295,000 km of water main, much of which was laid in unlined cast iron prior to 1940. Subsequently, asbestos cement, UPVC and cement lined cast/ductile iron has been uscd. It is kn-that a substantial number of...
Author(s) : Young, Howart
The West Wilts Water Board was set up in 1960, and among the many problems facing the Board were the following: Large areas of subsoil composed of aggressive Kimmeridge and Oxford clays whch were causing repeated corrosion failures of spun iron mains laid only 100 years before, aggravated by seasonal ground movements...