APPARATUS FOR COATING WELDED PIPE JOINTS

Abstract

An apparatus for powder coating a welded pipe joint includes a coating head having a powder chamber and at least one vacuum chamber. The coating head is mounted to a carriage operable to circumferentially traverse a pipe workpiece. The powder chamber has at least one inlet for receiving an air/powder suspension, and at least one outlet for delivering the air/powder suspension to a pre-heated weld zone of the pipe, such that the suspension fuses to and coats the weld zone. The vacuum chamber has at least one powder inlet for receiving excess air/powder suspension from the weld zone, and is connectable to a source of vacuum for exhausting the excess air/powder suspension from the weld zone. The coating thickness in the weld zone can be controlled by coordinated regulation of the air/powder flow rate into the powder chamber and the exhaust flow rate from the vacuum chamber.

Claims

1. A coating head comprising: (a) a powder chamber having one or more powder inlets and one or more powder discharge outlets, said one or more powder inlets being connectable to a source of a powderized coating material; and (b) a vacuum chamber having one or more vacuum inlets and one or more vacuum outlet ports, said one or more vacuum outlet ports being connectable to a source of vacuum; wherein: (c) the coating head is mountable on a coating head carriage adapted for mounting to a pipe so as to be circumferentially traversable around the pipe while maintaining the coating head a desired radial distance from the pipe surface, with the one or more powder discharge outlets being directed radially inward toward the surface of the pipe to enable the flow of coating material to a selected pipe surface region, and with the one or more vacuum inlets being positioned to enable the flow of coating material from the selected pipe surface region into the vacuum chamber; (d) the rate of flow of powderized coating material into the powder chamber is selectively variable; and (e) the rate of flow of powderized coating material into the vacuum chamber is selectively variable.

2. A coating head as in claim 1 wherein the coating material is in the form of an air/powder suspension.

3. A coating head as in claim 1 wherein the powder chamber shares a common wall with at least one of the at least one vacuum chambers.

4. A coating head as in claim 1 wherein the one or more powder inlets comprise one or more nozzle ports formed in a nozzle plate in an upper region of the powder chamber.

5. A coating head as in claim 1 wherein the powder chamber is defined by a pair of spaced sidewalls extending between a pair of endwalls, and wherein the one or more powder inlets are provided in said sidewalls or in said endwalls.

6. A coating head as in claim 1 wherein the powder discharge outlet is an opening extending across a lower region of the powder chamber.

7. A coating head as in claim 1 wherein at least one of the one or more vacuum inlets is an opening extending across a lower region of the corresponding vacuum chamber.

8. A powder coating apparatus comprising a coating head as in claim 1, and including the coating head carriage.

9. A powder coating apparatus as in claim 8 wherein the coating head carriage has curved side rails which carry pipe-engaging wheels driven by a carriage drive motor.

10. A powder coating apparatus as in claim 9 wherein the side rails of the coating head carriage are hinged to facilitate mounting on a pipe.

11. A powder coating apparatus as in claim 8 wherein the radial position of the coating head is adjustable.

12. A method for applying a powder coating to a weld zone associated with a circumferential welded joint on a pipe workpiece, said method comprising the steps of: (a) providing a powder coating apparatus as in claim 8; (b) mounting the powder coating apparatus onto the pipe workpiece in the region of the weld zone; (c) connecting the one or more powder inlets of the powder chamber of the coating head of the powder coating apparatus to a source of a selected powderized coating material; (d) connecting the one or more vacuum outlet ports of the vacuum chamber of the coating head to a source of vacuum; (e) applying heat to the weld zone of the pipe workpiece sufficient for fusion of the coating material to the workpiece; (f) actuating the source of vacuum; (g) initiating the flow of coating material into the powder chamber such that the coating material is discharged through the one or more powder discharge outlets of the powder chamber and toward the weld zone of the workpiece; and (h) selectively adjusting the rate of flow of coating material into the powder chamber and the rate of flow of coating material into the vacuum chamber to achieve a desired thickness of coating over the weld zone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments in accordance with the present disclosure will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which:

[0024] FIG. 1 is an isometric view of an exemplary embodiment of a carriage-mounted coating head in accordance with the present disclosure, shown mounted on a pipe.

[0025] FIG. 2 is an enlarged isometric view of the coating head in FIG. 1.

[0026] FIG. 3 is a further enlarged isometric view of the coating head in FIG. 1, illustrating the powder discharge outlet of the powder chamber and the vacuum inlets of the vacuum chambers.

DETAILED DESCRIPTION

[0027] FIG. 1 illustrates one embodiment of a powder coating application apparatus 100 in accordance with the present disclosure, mounted around on a pipe assembly 50 formed by two coaxially-aligned sections 50A and 50B of coated pipe that have been joined end-to-end by a circumferential welded joint 55 subsequent to the removal the coating in cut-back areas 52A and 52B at the ends of pipe sections 50A and 50B, respectively. Apparatus 100 includes a coating head 10 mounted in a coating head carriage 40 adapted for mounting to pipe assembly 50 such that carriage 40 can traverse a weld zone comprising welded joint 55 and cut-back areas 52A and 52B (typically but not necessarily by way of oscillating circular movements), while keeping coating head 10 at a set radial distance from the pipe surface. Various types of carriages suitable for this purpose are known in the art, and apparatus in accordance with the present disclosure are not restricted or limited to the use of any particular type of carriage or carriage structure to provide the required functionality.

[0028] In the illustrated embodiment, and by way of example only, carriage 40 has curved side rails 42 which carry pipe-engaging wheels 44 driven by a carriage drive motor 46 (which may be of any suitable type, such as but not limited to electric or hydraulic). Although not illustrated in detail in FIG. 1, carriage side rails 42 may be hinged to facilitate mounting on pipe assembly 50, with suitable latch means for retaining carriage 40 in position on pipe assembly 50 while in operation. Coating head 10 is shown as being mounted between carriage side rails 42. Coating head 10 could be rigidly mounted to carriage 40, so as to permanently position coating head 10 at a fixed radial distance from the centerline of pipe assembly 50. In alternative embodiments, coating head 10 could be mounted to carriage 40 so as to facilitate adjustment of its radial position.

[0029] FIGS. 2 and 3 illustrate coating head 10 in greater detail. In the illustrated embodiment, coating head 10 comprises two spaced side beams 12 separated by two end members 14. A powder chamber 20 is defined by a pair of powder chamber sidewalls 22 spanning between a pair of powder chamber endwalls 24, which in turn span between side beams 12. Powder chamber 20 is provided with one or more powder inlets 28 for introducing an air/powder suspension into powder chamber 20. In the illustrated embodiments, powder inlets 28 are provided in the form of nozzle ports through a nozzle plate 26 in the upper (i.e., radially-outward) region of powder chamber 20. However, this is by way of non-limiting example only, and powder inlets could be provided in other forms using different structure without departing from the scope of the present disclosure. For example, in alternative embodiments powder inlets could be provided in powder chamber sidewalls 22 and/or in powder chamber endwalls 24, with the upper region of powder chamber 20 being capped off with a solid plate.

[0030] Powder chamber 20 also has at least one powder discharge outlet 21 suitably positioned to deliver the air/powder suspension to the weld zone of a pipe workpiece. In the illustrated embodiment (and as best seen in FIG. 3), a powder discharge outlet 21 is provided in the form of an opening extending across the lower (i.e., radially-inward) side of powder chamber 20. However, this is by way of non-limiting example only, and embodiments in accordance with the present disclosure are not limited to this particular form or configuration of powder discharge outlets. For example, in unillustrated alternative embodiments, the lower side of powder chamber 20 could have a cover plate with perforations that serve as powder discharge outlets.

[0031] As best seen in FIG. 3, the lower (i.e., radially-inward) edges 25 of powder chamber endwalls 24 optionally may be contoured to conform with the curvature of pipe assembly 50. Although not illustrated as such in FIG. 3, the lower edges 23 of powder chamber sidewalls 22 optionally may be similarly contoured.

[0032] The illustrated embodiment of coating head 10 also includes a pair of vacuum chambers 30, one on either side of powder chamber 20. Each vacuum chamber 30 is defined by a portion of one of the side beams 12, the adjacent powder chamber sidewall 22, and one or more vacuum chamber roof members 32 extending between the respective side beams 12 and powder chamber sidewalls 22.

[0033] Each vacuum chamber 30 has at least one vacuum inlet 31 suitably positioned to receive excess air/powder suspension from the weld zone. In the illustrated embodiment (and as best seen in FIG. 3), each vacuum chamber 30 has a vacuum inlet 31 in the form of an opening across its lower (i.e., radially-inward) side. However, this is by way of non-limiting example only, and embodiments in accordance with the present disclosure are not limited to this or any other particular form or configuration of vacuum inlets. For example, in unillustrated alternative embodiments, the radially-inward side of vacuum chamber 30 could have a cover plate with one or more openings or perforations that serve as vacuum inlets.

[0034] One or more vacuum outlet ports 36 are provided for each vacuum chamber 30, connectable to a source of vacuum to facilitate exhausting of excess air/powder suspension entering vacuum chamber 30 from the weld zone via vacuum inlet 31.

[0035] It is to be noted that the radial positions of lower edges 13 of side beams 12 in the vicinity of vacuum chambers 30 could match the radial positions of lower edges 23 of powder chamber sidewalls 22, but this is not essential. In alternative embodiments, lower edges 13 could be positioned either radially inward or radially outward of lower edges 23.

[0036] The illustrated structural configuration of vacuum chambers 30 is by way of non-limiting example only, and alternative embodiments of coating head 10 could have functionally suitable vacuum chambers of other structural configurations without departing from the scope of the present disclosure. As well, although the illustrated embodiment incorporates two vacuum chambers, alternative embodiments could have only a single vacuum chamber.

[0037] The Brief Summary section of this disclosure provides a general description of the operation of powder coating application apparatus 100.

[0038] It is to be understood that the scope of the present disclosure should not be limited by the any particular embodiment or embodiments described and illustrated herein, but should be given the broadest interpretation consistent with the disclosure as a whole. It is also to be understood that the substitution of a variant of a claimed element or feature, without any substantial resultant change in functionality, will not constitute a departure from the scope of the disclosure.

[0039] In this patent document, any form of the word comprise is to be understood in its non-limiting sense to mean that any element following such word is included, but elements not specifically mentioned are not excluded. A reference to an element by the indefinite article a does not exclude the possibility that more than one such element is present, unless the context clearly requires that there be one and only one such element.

[0040] The use of any form of any term describing an interaction between elements (such as but not limited to connect, engage, mount, or attach) is not intended to limit the interaction to direct interaction between the subject elements, and may also include indirect interaction between the elements such as through secondary or intermediary structure. Relational or relative terms (such as, but not limited to, horizontal, vertical, parallel, perpendicular, coaxial) are not intended to denote or require absolute mathematical or geometrical precision. Accordingly, such terms are to be understood as denoting or requiring substantial precision only (e.g., substantially horizontal) unless the context clearly requires otherwise.

[0041] Wherever used in this document, the terms typical and typically are to be interpreted in the sense of being representative of common usage or practice, and are not to be understood as implying invariability or essentiality.