Abstract: A pipe connection of a first and a second fibre reinforced plastic pipe by accommodating a free end portion of each pipe in a centering plastic pipe part, an adhesive layer being present between the inner side of the centering pipe part and the outer side of the free end portions. A reinforcing layer extends over the centering pipe part and over parts of the first and second pipe part adjoining the free ends of the centering pipe part, preferably the centering pipe part has a smaller wall thickness than the wall thickness of the first and second pipe parts.The free end portions have a smaller wall thickness than the wall thickness of the centering pipe part.The centering pipe part may be formed as a bend, or part of a saddle or branch saddle and consists of a reinforced thermosetting plastic material.The bend may be formed from a plurality of standard bend parts of relatively small length, e.g. 5.degree. or 10.degree.

Abstract: The invention relates to a process for manufacturing an inner tube element made of synthetic resin for a double tube coring apparatus provided for deep boring. The tube element is provided with coupling nipples for connecting it to other inner tube elements. Fibers coated with synthetic resin are wound helically onto a cylindrical mandrel so as to overlap each nipple. This process gives the tube element a higher strength than that of glued nipples.