GB2423686A

GB2423686A - Electrically-heated pipes

Info

Publication number: GB2423686A
Application number: GB0603907A
Authority: GB
Inventors: Kevin Mcclay; Mark Cook; Robin Hunter
Original assignee: ALLEN GROUP Ltd
Current assignee: ALLEN GROUP Ltd
Priority date: 2005-02-25
Filing date: 2006-02-27
Publication date: 2006-08-30
Also published as: GB0603907D0; GB0503891D0; WO2006090182A1

Abstract

An electrically-heated pipe or hose 1 has a central bore 9, preferably formed by an extruded polymeric tube 8, that is surrounded by a layer 10 of electrically-conductive material. This layer 10 may be covered by a protective layer 2. Conductors 11 and 12 embedded in the layer 10, run lengthwise of the hose 1, so that electric current flows in the layer 10 around the tube 8 to heat it along its length. The conductors 11 and 12 are preferably bare wire and diametrically opposite. Supply of electric current to hoses (each having the form of hose 1) within a selective catalytic reduction system (SCR) of a diesel-powered vehicle engine can maintain flowability of a urea solution injected into the exhaust of the engine (figure 6).

Description

Electrically-Heated Pipes This invention relates to electrically-heated

pipes, and is concerned especially, though not exclusively, with electrically-heated pipes of the kind used in vehicle systems where it is desirable to maintain the pipe at a temperature which will ensure flowability of fluid within it.

In the latter regard, selective catalytic reduction (SCR) systems have been proposed for use in removal of nitrogen oxides from the exhaust emissions of diesel-powered commercial vehicles. Such systems are based on injection of a solution of urea into the hot exhaust gas. However, because the solution freezes at about -11 degrees Celsius, there is the likelihood that in some circumstances of vehicle-operation, supply of the solution to the injector will be frustrated so that the system does not function properly. Proposals have been made to overcome this problem by electrically heating the hoses or other pipes used to convey the solution to the injector, using electrically-insulated conductors wound helically round them.

It is one of the objects of the present invention to provide an electrically-heated pipe that may be used with advantage instead of a helically-wound pipe, in the above and other contexts.

According to one aspect of the present invention there is provided electrically-heated pipe wherein the pipe has a surrounding layer of material that is embedded with mutually-spaced electrical conductors in electrical contact with the material of the layer, and the material of the layer is electrically conductive such that voltage applied between the conductors causes electric current to flow through the material of the layer to heat the pipe.

The electrically-conductive layer may be a coating to the pipe, or a sleeve surrounding it.

One or more pairs of conductors may be embedded in the layer and may run lengthwise of the pipe, or extend helically or otherwise along the pipe. Where there is just one pair of embedded conductors they may be located diametrically opposite one another relative to the pipe.

The electrically-heated pipe according to the invention may be used for conveying fluid, or for fuel ventilation, within an engine installation.

More especially, the engine installation may include a selective catalytic reduction (SCR) system for exhaust emissions of the engine, and in these circumstances the electrically-heated pipe may be used for conveying a solution of urea or other material within the system, for example between a pump and injector of the system.

An electrically-heated pipe in accordance with the present invention, for use in a commercial vehicle, and a commercial-vehicle installation including such electrically-heated pipes, will now be described, by way of example, with reference to the accompanying drawings, in which: Figures 1 and 2 are respectively a plan view and side elevation of an electrically-heated pipe according to the invention; Figure 3 is illustrative in broken-away perspective plan of the structure of the electrically-heated pipe of Figure 1; Figures 4 and 5 are respectively a part-sectional side elevation and a representative plan view in perspective of one end of the electrically-heated pipe of Figures 1 and 2; and Figure 6 is a block schematic representation of part of the engine installation of a diesel-powered commercial vehicle that includes electrically-heated pipes according to the invention.

Referring to Figures 1 and 2, the electrically-heated pipe in this case is provided by an elongate, flexible hose 1 that has an outer protective sleeve 2. Connectors 3 and 4 are fitted to the two ends of the hose 1 for coupling it into a fluid-supply system of a commercial vehicle; the fluidsupply system may, for example, be that of a diesel-powered commercial vehicle for supplying fluid between components used for selective catalytic reduction (SCR) of the exhaust emissions of the vehicle.

Electrical connection to the hose 1 is made via a sheathed twin-core electrical cable 5 that extends part-way along the outside of the hose 1 between an electrical-input connector 6 and a moulded junction- block 7 that encases the hose 1 adjacent the fluid- connector 3.

As illustrated by Figure 3, the body of the hose 1 incorporates a tube 8 of extruded nylon that defines its central bore 9. The tube 8, which is electrically non-conductive is coated by extrusion with a tubular layer 10 of a thermoplastic elastomer which, in contrast to the material of the tube 8, is slightly electrically-conductive. Two bare-wire conductors 11 and 12 are embedded in the layer 10 to run lengthwise of the tube 8 diametrically opposite one another.

They are insulated from one another electrically at either end so that interconnection between them within the hose 1 is exclusively through the slightly-conductive layer 10. External electrical connection to them is made solely from the cable 5, within the junction block 7.

The manner of external connection to the conductors 11 and 12 from the cable 5 will now be described with reference also to Figures 4 and 5. For simplicity of illustration, the body of the hose 1 provided by the sleeve 2, the tube 8 and the layer 10 are shown as one in Figure 4, and the moulding of the junction block 7 is omitted from Figure 5.

Referring to Figures 4 and 5, the conductors 11 and 12 extend from the layer 10 within the moulded junction-block 7 for crimped connection to the two insulated leads 13 and 14 respectively, of the cable 5. Accordingly, when an electrical power supply is connected to the connector 6, voltage appears between the conductors 11 and 12 causing current to flow between them in the layer 10 throughout their full length. If a direct-current (DC) (or an alternating- current (AC)) power supply is used, current will flow constantly (or periodically where AC is involved) from whichever of the conductors 11 and 12 is positive to the other conductor in both directions round the layer 10, so that heat will be generated throughout the volume of the layer 10 around the full circumference of the hose 1. The heating is therefore substantially uniform, without hot-spots, throughout substantially the full length of the hose 1. In the latter respect, the gauge and resistivity of the conductors 11 and 12 themselves are chosen to be such that the current flow in them does not have a significant heating effect.

The two ends of the hose 1 at the connectors 3 and 4 respectively, are over-moulded (embedded in a moulding material) to seal them against the ingress of water. The over-moulding at the connector 4 forms an enshrouding, elbow block 15 at the interface between the connector 4 and the hose 1, whereas that at the connector 3 forms the junction block 7 which as well as providing the same sealing, enshrouding function at the interface between the connector 3 and the hose 1, protects and secures the cable 5 mechanically in its interconnection with the conductors 11 and 12.

External electrical connection to the hose 1 via the connector 6 may be from a switched-supply source that responds to the output of a temperature sensor, for example placed on the sleeve 2, to switch power (for example in pulse form) to the hose 1 ON only when the sensed temperature has fallen below a lower threshold value and to switch it OFF when an upper temperature threshold is reached.

In one embodiment of the electrically-heated hose 1 described above, the outer protective-sleeve 2 is of a polypropylene, and the tube 8 is of electrically non-conductive polyamide 12, whereas the layer 10 is of a polypropylene material loaded with carbon-black additive to make it electrically conductive. The layer 10 may have a resistivity, of, for example, 50 ohm centimetre, and the conductors 11 and 12 may be of copper wire of 0.50 mm gauge. More generally, the resistivity of the layer 10 may, for example, be in the range 1 - 100 ohm centimetre, and the gauge of the conductors 11 and 12 may be within the range 0.30 - 0.60 mm.

As indicated above, the hose 1 may be used in the fluid-supply system of a diesel-powered commercial vehicle for supplying fluid between components used for selective catalytic reduction (SCR) of the exhaust emissions of the vehicle. Such a system and the use of three hoses of the general form of hose 1 described above, will now be described with reference to Figure 6.

Referring to Figure 6, the hot exhaust-emissions from a diesel engine 20 of the commercial vehicle are supplied via a path 21 to an SCR catalyst unit 22 for removal of nitrogen oxides before release via the exhaust outlet 23 of the vehicle. The removal of the nitrogen oxides is carried out by injecting a solution of urea into the path 21, and is monitored by a sensor (not shown) of the unit 22 which communicates with an electronic unit 24 that controls supply of the urea solution.

The unit 24 communicates with the main electronic control 25 of the engine 20 and as well as responding to the output of the sensor of the unit 22, responds to the output of a sensor (not shown) in the path 21, to bring about the most efficient operation of the SCR system. It does this by regulating supply of the urea solution from a reserve-tank unit 26 in dependence upon the operation of the engine 20, the engine-emission and monitored system-effectiveness.

The urea solution from the unit 26 is supplied to a pump 27 via a hose 28, and the pump 27 supplies overflow back to the unit 26 via a hose 29. The pumped output from the pump 27 is supplied via a hose 30 to an injector 31 that injects the urea solution under pressure into the path 21 (a heated-hose return line from the injector 31 to the pump 27 may be added).

The hoses 28, 29 and 30 are each electrically-heated hoses corresponding to the hose 1 described above.

Voltage is applied to each of them to ensure that the resultant current flow in its layer 10 maintains the urea solution at a substantially uniform temperature throughout the hose-length, adequate for goodflowability irrespective of the climatic conditions to which the vehicle is subjected.

Hoses corresponding to the hose 1 may be used in other applications, for example where water, diesel fuel or oil are to be conveyed in the context of vehicle or other operations. They may also be used in circumstances where there is a need to prevent a ventilation tube, for example of a fuel tank, becoming blocked in freezing conditions.

It has been found that hoses having the form of hose 1 have significant advantages of efficiency and uniformity of heating, over conventional hoses heated by electrically-insulated conductors wound helically round them. In particular, it has been found that with a hose of the form of hose 1, frozen urea solution at an ambient air temperature of -38 degree Celsius can be melted to flowability within the hose, using a power input of 20 watt per metre supplied for less than 30 minutes.

Although in the embodiment of the invention described above, the conductors 11 and 12 extend from the layer to enable connection to be made to them from the cable 5, blades, spikes or other members clamped to the hose 1 may be used instead, to pierce the sleeve 2 and layer 10 to make the connection.

Claims

Claims: 1. An electrically-heated pipe wherein the pipe has a surrounding

layer of material that is embedded with mutually-spaced electrical conductors in electrical contact with the material of the layer, and the material of the layer is electrically conductive such that voltage applied between the conductors causes electric current to flow through the material of the layer to heat the pipe.
2. An electrically-heated pipe according to Claim 1 wherein the layer is a coating to the pipe.
3. An electrically-heated pipe according to Claim 1 or Claim 2 wherein the embedded conductors run lengthwise of the pipe within the layer.
4. An electrically-heated pipe according to any one of Claims 1 to 3 wherein the embedded conductors are a pair of conductors that are located diametrically opposite one another relative to the pipe.
5. An electrically-heated pipe according to any one of Claims 1 to 4 wherein the material of the layer is a plastics material loaded with carbon- black for its electrical conductivity.
6. An electrically-heated pipe according to Claim where the plastics material is polypropylene.
7. An electrically-heated pipe according to any one of Claims 1 to 6 wherein an extruded tube of electrically non-conductive material defines a central bore of the pipe, and the layer of electrically-conductive material is an extruded coating of the tube with the electrical conductors embedded in the coating.
8. An electrically-heated pipe according to Claim 7 wherein the extruded tube is of nylon.
9. An electrically-heated pipe according to any one of Claims 1 to 8 wherein the electrical conductors extend from the electrically-conductive layer, and electrical connection is made to them where they extend from the layer.
10. An engine installation wherein an electrically-heated pipe according to any one of Claims 1 to 9 is used for conveying fluid, or for fuel ventilation, within the installation.
11. An engine installation according to Claim 10 wherein the installation includes a selective catalytic reduction (SCR) system for exhaust emissions of the engine, and the electrically- heated pipe is used for conveying a solution of urea or other material within the system.
12. An engine installation according to Claim 10 or Claim 11 wherein the engine of the installation is a diesel engine.
13. An electrically-heated pipe substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.
14. A diesel-engine installation substantially as hereinbefore described with reference to Figure 6 of the accompanying drawings.