Pipe coating apparatus and method

Details Pipe coating apparatus and method Pipe coating apparatus and method

2001-07-19

2003-07-08

Crispino, Richard (Department: 1734)

Coating apparatus

With means to apply electrical and/or radiant energy to work...

Electrostatic and/or electromagnetic attraction or...

C118S634000, C118S630000, C118S629000, C118S064000, C118S309000, C118S316000

Reexamination Certificate

active

06589346

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to pipe coating apparatus and methods for coating a length of non-rotating pipe with a fluid.
BACKGROUND OF THE INVENTION
Steel pipes or tubing which are intended for underground installation must be protectively coated against corrosion. This is typically accomplished by coating a pipe with an adhesive coating or primer followed by a layer of plastic jacketing material in a two-step procedure. The primer frequently consists of a particulate epoxy thermo-setting powder which fuses to a heated pipe to which the powder is applied. The jacketing material often consists of high density polyethylene.
A traditional method for protectively coating a length of pipe is to rotate and convey a heated pipe longitudinally through a booth in which are mounted an array of powder guns. The powder guns spray particulate primer material about the circumference of the pipe as it is advanced through the booth. Downstream of the booth is spiral wrapping apparatus which winds jacketing material in screw thread fashion onto the rotating pipe as disclosed, for example, in U.S. Pat. No. 3,616,006 to Landgraf et al.
There are several disadvantages associated with the above approach. First, the conveying system used to rotate and advance the pipe is expensive to construct and maintain. Second, particularly in connection with smaller diameter pipes, it is difficult to achieve a uniform coating of primer on the pipe and there is also a great deal of over-spray and hence wastage of primer material. Third, jacketing material applied using a spiral method are subject to weak joints at the overlap and poor coverage of radial or longitudinal welding seams on the pipe. The disadvantages of spiral wrapping are greater where high density polyethylene is applied as the outer jacketing material. Pipe which has been spiral-wrapped with jacketing material often exhibits relatively poor low temperature adhesion of the protective coating. Fourth, this approach can only be used in an industrial plant setting and cannot be used to renew the pipe coating of a pipe at the site of installation.
To overcome the above disadvantages, alternative methods for protectively coating pipe have been sought. For example, a presently preferred method of jacketing a pipe employs a “cross-head” extrusion technique, also known as a “straight-through” or “endo” process. This entails conveying a non-rotating pipe longitudinally through an annular nozzle or head of an extruder, the extruder being operable to extrude tubular coatings of adhesive film and jacketing material over the pipe as it passes through the extrusion head.
To more readily employ the cross-head extrusion technique, it is desirable to provide an apparatus for and method of coating a length of non-rotating pipe with primer material upstream of the cross-head extruder. Furthermore, it is desirable that such apparatus be adapted to overcome or minimize the other problems described above.
SUMMARY OF THE INVENTION
Accordingly, in accordance with one aspect, the invention provides an apparatus for coating the outer surface of a non-rotating pipe with a fluid. The apparatus includes a fluid reservoir for containing fluid to be discharged onto the surface of a pipe, and a pipe receiving chamber extending through and separate from the fluid reservoir. The apparatus further includes a fluid application assembly having a plurality of fluid intake openings positioned in the fluid reservoir for the intake of fluid therefrom. The fluid intake openings are rotatable in a circular pattern within the reservoir about a path extending through the chamber. The assembly has a plurality of fluid discharge outlets in fluid communication with the fluid intake openings and directed towards the path. The fluid discharge outlets are rotatable in unison with the fluid intake openings about the path, whereby fluid entering the fluid intake openings from the reservoir is discharged through the fluid discharge outlets to coat the outer surface of a pipe being conveyed along the path.
In accordance with another aspect, the invention provides a method of applying a fluid coating to a length of non-rotating pipe employing the apparatus.


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