ELECTRIC CURRENT HEATER FOR PIPES

SYSTEME DE CHAUFFAGE ELECTRIQUE POUR TUYAUX

English Abstract

2062738 9010817 PCTABS00002
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.

Claims

WO 90/10817 PCT/FI90/09068
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 (S)
which is attached to the pipe by pushing the plastic hems
(6) of the strip (5) round the pipe.

WO 90/10817 4 PCT/FI90/00068
AMENDED CLAIMS
[received by the International Bureau
on 15 August 1990 (15.08.90);
original claims 1-4 replaced by amended claims 1 and 2 (1 page)]
1. Electric current heater 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 (1) or in its extension, 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 round the pipe.
2. Electric current heater according to claim 1,
characterized in that there are more than one conduit (2)
if necessary.

Description

L i . .
ELECTRIC CURRENT HEATER FOR PIPES
Water and sewage pipes often have to be opened by heating
after they have fro~en 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 ~o make a pipe having wires embedded in
~he walls during manufactuxe. This is the case particularly
if normal ~oltages of 380 Yl 230 V, or 110 ~ are used which
: reguire protection of the resistance wire from damage
according to the existing safety regulations in several
coun~ries.
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 descrihed by means of
enclosed figure 1.
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L~ 3,~ \ 2
On the outside of the wall 1 of a ~inished plastic pipe, an
ex~ension is cast forming a conduit 2 into which a
protected resistance wire ox 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 ~he wall of the tube already at the extrusion stage
of manufacture. The conduit can also be made on ~op 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 ~ary according to uses.
The wires an be locked in place and even cast tagether
with the pipe material to improve thermal conduc~ivity 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
~or the holes 4 by means of an extruder provided with an
appropriate perforator. Duxing 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.
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Representative Drawing