WO1990010817A1

WO1990010817A1 - Electric current heater for pipes

Info

Publication number: WO1990010817A1
Application number: PCT/FI1990/000068
Authority: WO
Inventors: Urpo Vainio
Original assignee: Urpo Vainio Oy
Priority date: 1989-03-16
Filing date: 1990-03-16
Publication date: 1990-09-20
Also published as: SE469533B; SE9103481D0; SE9103481L; NO914618L; FI82510C; NO914618D0; FI82510B; FI891233A0; CA2062738A1

Abstract

Heating system for pipes wherein heating, for instance for melting ice, is performed by supplying electric current through a resistance wire (3), the wire being passed into the wall (1) or a conduit (2) made on the outside of the pipe during manufacture of the plastic or corresponding pipe.

Description

ELECTRIC CURRENT HEATER FOR PIPES

Water and sewage pipes often have to be opened by heating after they have frozen up.

Melting has become increasingly difficult since electrically non-conducting materials like plastics have come into use in the manufacture of these pipes. Therefore, pipes cannot anymore be heated by using them as electric resistors.

Attempts have been made to accomplish heating by means of electrically conducting wires wound on the surface of the pipe or placed inside the pipe, the wires acting as resistors. However, protection of these wires is difficult and internal wires will disturb the free flow of the liquid. Furthermore, attempts have been made to use plastic pipes having resistance wires embedded in the pipe wall either parallel with the pipe or spirally. To avoid need for return wires on the outside of the pipes the resistance wires embedded in the material might have been shorted in pairs at the other end of the pipe during installation. In addition to resistance wires one might also use a strip resistance or a resistance of another shape. It is, however, difficult to make a pipe having wires embedded in the walls during manufacture. This is the case particularly if normal voltages of 380 V, 230 V, or 110 V are used which require protection of the resistance wire from damage according to the existing safety regulations in several countries.

The enclosed invention will remove these drawbacks. It is characterized primarily in what has been set forth in claim 1.

One embodiment of the invention is described by means of enclosed figure 1. On the outside of the wall 1 of a finished plastic pipe, an extension is cast forming a conduit 2 into which a protected resistance wire or wires 3 can be drawn either at the last stage of manufacture or later, in the same way as electric cables are drawn into plastic tubing used in buildings. The conduit for the resistance wires can also be made in the wall of the tube already at the extrusion stage of manufacture. The conduit can also be made on top of a conventional pipe by pushing into a plastic strip 5 as shown in figure 2. The hems of the plastic strip are merely pushed round the pipe.

The resistance, protection, and structure of the wires can in general vary according to uses.

The wires can be locked in place and even cast together with the pipe material to improve thermal conductivity if, during manufacture or later, holes 4 are made through which appropriate binding and filling compound is compressed. The compound can be compressed through the wall without need for the holes 4 by means of an extruder provided with an appropriate perforator. During installation it is generally practicable to put the cable below the pipe center in order to improve thermal conductivity.

Instead of one conduit there can be several conduits 2 if necessary.

Claims

1. Heating system for pipes wherein heating, for instance for melting ice, is performed by supplying electric current through a resistance wire or wires (3) in the wall of a pipe or in its extension characterized in that, on the outside of the wall of the pipe (1), an extension is made after manufacture of the pipe, the extension having a conduit (2) for the later installation of resistance wires (3) or that this conduit (2) is made into the wall of the pipe already during manufacture of the pipe.

2. Heatable pipe (1) with conduits (2) according to claim 1 characterized in that, after installation of the cable, binding and filling compound is compressed into the conduit through holes (4) in the wall of the conduit (2).

3. Pipe according to claim 1 characterized in that there are more than one conduit (2) if necessary.

4. Heatable pipe according to claim 1 characterized in that the extension with the conduits (2) on the outside of the wall of the pipe (1) is comprised of a plastic strip (5) which is attached to the pipe by pushing the plastic hems (6) of the strip (5) round the pipe.