Abstract: A union for tubes having a first external wall and a second internal wall coaxial with the first to define a chamber around a central duct. The union includes at least two seats for reception each of one end of a tube to be connected. Each seat includes a first surface designed to adhere to an end segment of the first wall of a tube inserted in the seat and a second surface coaxial with the first and designed to adhere to an end segment of the second wall of the tube. Between the first and second surfaces of the union there is a connection surface. The union includes in it first ducts which lead into the connection surfaces to provide connection between the chambers of tubes inserted in the seats and second ducts which lead into spaces circumscribed by the second surfaces to provide connection between the central ducts of the tubes.

Abstract: A pipe fitting for pipelines comprises at least one seating (12) for receiving the end of a pipe to be coupled. The seating surface which is intended to come into contact with the surface of the pipe end, is made of a material having a chemical adhesion reaction on reaching of a predetermined temperature and, around the seating (12), the pipe fitting incorporates an electric winding (14) for heating of the material when an electric current passes therethrough in order that said predetermined temperature can be reached. Advantageously, the seating (12) is formed in a sleeve (17) incorporating the electric winding (14) which in turn is incorporated into the pipe fitting body.