Abstract: A reinforced tube or a tubular pipe comprises an inner tubular first layer of glass fiber reinforced plastic, an outer tubular second layer disposed around and spaced radially outwardly from the first layer and also comprising a glass fiber reinforced plastic, and an intermediate filler layer located between the first and second layers and containing plastic and granular filler material which is bonded together and to said first and second layer. In addition a reinforcing insert is embedded in the intermediate filler layer and it comprises a continuous coil wound around the first layer and embedded in the intermediate layer. The coil may comprise a fiber reinforced plastic coil or a steel wire coil and a single one or two concentrically arranged coils may be embedded in the filler layer. The filler layer comprises plastic bonded granular material such as plastic and sand or an insulating material which may be made of an epoxy or a diphenyl polyester resin.

Abstract: A glass fiber reinforced multilayer pipe of plastic, comprises a wall having a plurality of plastic layers interconnected together and having a central wall axis with a median area on each side of the axis directly adjacent the axis and with an outer area radially outwardly from said median area, and an inner area radially inwardly of said median area. The plastic layers of the pipe wall include a plurality of glass fiber reinforced plastic layers and a plurality of plastic bonded granular filler material layers. The glass fiber reinforced plastic layers are provided both in the inner area and the outer area and the percentage of reinforcing glass fiber in the outer area is less than the percentage in the inner area. The ratio of the outer area glass fiber percentage to the inner glass fiber percentage is preferably 3 : 5.