AU772972B2 - Detection of circumferential erosion of a conduit - Google Patents

Description

WO 00/70326 PCT/AU00/00472 DErECTION OF CIRCUMFERENTIAL EROSION OF A CONDUIT This invention relates to an erosion detector. In particular, the invention concerns a detector for detecting erosion in a conduit or similar member which is subject to wear.

Pipes used for conveying slurries and outlet cones employed in cyclone separators are subject to high degrees of wear due to the abrasive nature of the slurries and materials which progress through the cones or pipes. The cones and pipes may be lined with a sacrificial and/or wear resistant lining such as a composite including a ceramic or other hard material. The operation of a cyclone separator requires that the size of the outlet aperture be within predefined tolerances. If the diameter of the outlet increases beyond a predetermined size through erosive wear then the outlet cone should be replaced. Similarly, pipes carrying abrasive material such as slurries may fail if the lining is worn away. It is accordingly desirable to determine wear of the liner.

United States Patent Specification 4642557 discloses a probe in a conduit wall for detecting erosion in the wall. The probe consists of an insulated conductor which is in electrical contact, at the base of a blind hole, with the conduit. Wear of the conduit down to the level of the probe may be determined by periodic continuity measurements, a lack of continuity indicting that the inserted end of the probe has been exposed. The probe requires that the pipe in which the insulated conductor is inserted be electrically conductive in addition the construction of the probe is such that it is only able to detect erosion at one particular radial location in the wall of the conduit or pipe. If the length of pipe is installed in a flow path and the probe is radially displaced from the flow path of the material within the pipe then the probe is ineffective in determining erosion at a radially displaced location.

In another known erosion probe two longitudinally spaced non- conductive plugs were placed extending through the wall of the pipe and a conductor was arranged to extend into the pipe, along a length of a non-conductive lining within the pipe and out of the pipe through the other plug. As the lining adjacent the probe wears down to the conductor, continuity of the circuit indicates that the liner is within acceptable dimensions. When the exposed conductor wears through, discontinuity is detected as an indicator for maintenance. However, lining wear may not be circumferentially even. Accordingly, the probe may indicate that the liner is within 2 acceptable dimensions when a portion of the liner circumferentially spaced from the probe has worn beyond acceptable limits.

In one aspect of the invention, there is provided a method of determining erosive wear within a conduit having an outer shell and an in situ moulded lining, the method comprising monitoring for continuity a conductor extending substantially about the circumference of the conduit and embedded in said lining, said conductor being supported on chairs or the like of an electrically insulating material during formation of the lining, said chairs being left in situ in the lining after formation thereof, at least some of said chairs extending through openings provided in the outer shell and having a connection passing therethrough from said conductor to means performing said monitoring.

In a further aspect this invention resides in a method of forming a conduit including the steps of providing an outer shell, supporting a conductor in spaced relation to and extending substantially about the circumference of the inner wall 15 of said outer shell on chairs or the like of an electrically insulating material, at least some of said chairs extending through openings provided in the outer shell and having a connection passing therethrough from said conductor to continuity monitoring means, and in situ forming a moulded lining in said conduit and embedding said conductor and said chairs or the like.

In a further aspect, this invention resides broadly in a conduit comprising S: an outer shell and an in situ-moulded lining having embedded therein a conductor extending substantially about the circumference of the conduit, said conductor being supported on chairs or the like of an electrically insulating material during formation of the lining, said chairs being left in situ in the lining after formation thereof, at least some of said chairs extending through openings provided in the outer shell and having a connection passing therethrough from said conductor to monitoring means for monitoring the continuity of said conductor.

The detection means may comprise an embedded conductor extending substantially about the circumference of the conduit whereby monitoring means may monitor the continuity of the conductor. The conductor may be embedded in a liner, or be disposed about the outer surface of the liner.

2A The lining where used is preferably a moulded lining formed of a composite material whereby the detection means may be embedded therein during formation of the lining. Examples of suitable lining materials include those composites of a refractory material such as a ceramic and a binder. One liner material of this class is the composite of sintered bauxite and epoxy resin currently used to line slurry pipes and cyclone outlet cones. In this composite, bauxite (crude hydrated aluminium hydroxide) is sintered at high temperatures and the sinter crushed to produce a hard particulate material. The liner is formed up by mixing the crushed sintered bauxite with epoxy resin, moulding to shape and curing. The linings so formed are insulative with considerable dielectric strength.

o*oo -WO 00/70326 PCT/AU00/00472 3 In the moulding stage detection means may be set up in the composite by any suitable means. For example, the detection means may be supported on chairs or the like during the moulding process. The chairs may be left in situ in the lining or may be removed after curing, whereupon the voids formed thereby are filled the lining composite or other material. In the case of detection means requiring electrical or other connection to monitoring means outside of the conduit, the chairs may be configured whereby they extend through openings provided in the conduit wall and have the connection passing therethrough. To this end and to avoid the need for insulating electrical connection, the chairs are preferably formed of an insulating material.

The conductor when used may be coated with an insulating material if the lining is electrically conductive. Where the lining is non-conductive, the conductor need not be insulated. Any suitable electrically conductive material may be employed for the conductor. Preferably the conductor is selected to wear at least as readily as the lining material whereby the conductor does not overly resist wear when the liner is worn to the conductor. For example, the conductor may be made from stainless steel. The conductor may extend through walls of the cyclone cone or conduit.

Where the conductor extends through the walls, insulating plugs apart from the foregoing chairs may be employed to electrically isolate the conductor from the walls of the conduit. The conductor may extend through the plugs. The plugs may be made from any suitable material.

Preferably the chairs and/or plugs are made from polyurethane. The conductor embedded in the lining may follow a slightly helical path and the circular part of the conductor may be present as a complete circle or may extend through more than 3600. In this way the plugs and the ends of the conductor may be positioned so that end portions of the conductor may overlap and extend past each other.

The monitoring means may take any suitable form in general dictated by the selection of detection means. For example, in the case of capacitive detection means or an embedded circumferential conductor, the monitoring means may comprise an electronic monitoring means having suitable input characteristics and output a numeric or graphic display, alarm or the like. In the case of an ultrasonic WO 00/70326 PCT/AU00/00472 4 detection means, the monitoring means may include a circuit adapted to analyse the ultrasonic transducers for return signal and provide a suitable output.

The ends of the conductor may be coupled to a remote continuity monitoring system via any suitable link such as a cable, radio link or the like.

Particular preferred embodiments of the invention will now be described by way of example with reference to the drawing in which: Figure 1 is a partially sectioned elevation of a cyclone cone incorporating the erosion detector according to an embodiment of the invention- Figure 2 is a section taken along line A of Figure 1; and Figure 3 is a transverse sectional view of a conduit incorporating the erosion detector of an embodiment of the invention.

Figures 1 and 2 show a cyclone cone 10 having an outer metallic wall 11 lined with a wear resistant lining 12. The lining 12 in this case is a moulded sintered bauxite/epoxy composite. Apertures 13 and 14 are radially spaced from one another and are formed by setting up insulating plugs 15 and 16 during the moulding of the liner. A conductor 17 is embedded within the lining during formation thereof. In the illustrated embodiment, the conductor 17 is shown extending substantially around the cone and is spaced from the interior surface 18, through which material may pass from the cone, by a selected distance. The conductor is shown this way for clarity in illustration in simple section. It is however preferred that the conductor 17 describe a slightly helical shape such that in practice the ends 18 of the conductor 17 are circumferentially overlapped and longitudinally spaced. The ends 18 of the conductor project beyond the plugs 15 and 16 and allow the electrical continuity of the conductor to be tested. Once the lining wears and the conductor is broken, a continuity test will indicate that the lining has worn to the depth to which the conductor was imbedded within the lining.

The cone may then be replaced to ensure effective operation of the cyclone to which the cone is attached. Since the conductor extends substantially all of the way around the cone the erosion detector is responsive to excessive wear at any radial location around the interior of the cone.

Figure 3 shows a transverse sectional view across a conduit 20. 25 The conduit 20 has a wall 21 and a wear resistant lining 22 having an inner surface 23. A plurality of support plugs 24 extend through the wall 21 and support the conductor WO 00/70326 PCT/AU00/00472 at a desired spacing from the inner surface 23. The plugs 24 are made from any suitable electrically non-conducting material such as polyurethane. The conductor extends substantially around the conduit and terminates in free ends 26 which project through insulating plugs 27 and 28.

The continuity of the conductor may be periodically measured and if a break in continuity is detected this denotes that the lining has been worn down to the depth of the conductor.

If desired a plurality of conductors may be present within the lining and the conductors may be located at different depths within the lining. In this way the thickness of the remaining lining may be monitored and when the lining is too thin the conduit may then be replaced.

In a typical method of manufacture of a lined conduit in accordance with the invention, a steel pipe or cyclone outlet is formed with apertures into which are inserted polyurethane moulded chairs extending into the conduit. The chairs in turn support one or more circumferential conductors, which has its ends led out of the conduit through selected ones of the chairs. The composite lining is then moulded within the conduit, embedding the chairs and the one or more conductors.

It will of course be realised that while the above has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as defined in the claims appended hereto.

Claims (13)

1. A method of determining erosive wear within a conduit having an outer shell and an in situ moulded lining, the method comprising monitoring for continuity a conductor extending substantially about the circumference of the conduit and embedded in said lining, said conductor being supported on chairs or the like of an electrically insulating material during formation of the lining, said chairs being left in situ in the lining after formation thereof, at least some of said chairs extending through openings provided in the outer shell and having a connection passing therethrough from said conductor to means performing said monitoring.

2. A method of forming a conduit including the steps of providing an outer shell, supporting a conductor in spaced relation to and extending substantially about the circumference of the inner wall of said outer shell on chairs or the like of an electrically insulating material, at least some of said chairs extending through openings provided in the outer shell and having a connection passing therethrough from said conductor to continuity monitoring means, and in situ forming a moulded lining in said conduit and embedding said conductor and said chairs or the like.

3. A conduit comprising an outer shell and an in situ-moulded lining having embedded therein a conductor extending substantially about the circumference of the conduit, said conductor being supported on chairs or the like of an electrically insulating material during formation of the lining, said chairs being left in situ in the lining after formation thereof, at least some of said chairs extending through openings provided in the outer shell and having a connection passing therethrough from said conductor to monitoring means for monitoring the continuity of said conductor.

4. A conduit according to claim 3, wherein said moulded lining is formed from a curable polymer composition.

A conduit according to claim 4, wherein said curable polymer composition comprises a polyurethane.

6. A conduit according to claim 4, wherein said curable polymer composition comprises a composite of a ceramic and a binder.

7. A conduit according to claim 6, wherein said ceramic is sintered bauxite and said binder is epoxy resin.

8. A conduit according to any one of claims 3 to 7, wherein said conductor is disposed helically in the lining and extending through more than 3600 o whereby opposed ends thereof are displaced longitudinally one from the :O other.

9. A conduit according to any one of claims 3 to 8, and comprising a slurry pipe.

10. A conduit according to any one of claims 3 to 8, and comprising a cyclone cone.

11. A method of determining erosive wear within a conduit substantially as hereinbefore described with reference to the example.

12. A method of forming a conduit substantially as hereinbefore described with reference to the example.

13. A conduit substantially as hereinbefore described with reference to the accompanying drawings. DATED this 28 th day of November 2002 LUDOWICI MINERAL PROCESSING By their Patent Attorneys PIZZEYS