Electric heating – Heating devices – With heater-unit housing – casing – or support means
Reexamination Certificate
2000-02-04
2001-11-13
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
With heater-unit housing, casing, or support means
C219S534000, C219S528000, C219S549000, C285S041000, C138S033000
Reexamination Certificate
active
06316751
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
FIELD OF THE INVENTION
The present invention relates generally to an apparatus for applying and/or repairing fusable wraps on plastic-coated pipelines. More specifically, the present invention relates to a unified device and system for thermally fusing a layer of plastic to the plastic pipe coating so as to perform a variety of functions, including: covering and cathodically and mechanically protecting the area of a weld joint of a pipeline in the field; covering and mechanically protecting an exposed end of pipe insulation; holding together pipes in a pipeline bundle; confining a sacrificial anode to the proximity of a pipeline; and supporting and spacing an inner pipe within an outer pipe. Further, the present invention relates to a device and system for protecting the area of a weld joint between insulated pipes in the field with at least one plastic or foam preformed piece, such as a half shell, and holding the half shell in place with a fusable wrap. Still more particularly, the present invention comprises a circumferential compression clamp provided with electrical leads arrayed circumferentially and a corresponding plastic wrap piece provided with correspondingly arrayed leads.
BACKGROUND OF THE INVENTION
Pipelines are commonly used to transport fluids both underground and subsea. It is typical for pipelines to be provided with some type of protective coating for anti-corrosion and/or mechanical purposes. Common types of coating include coal tar and asphalt enamel. A concrete coating or sheath can be applied to individual lengths of pipe in a coating yard, before the pipes are shipped to the location where the pipeline is to be assembled. Alternatively, in the case of underground pipelines, the coating can be applied to the pipe “over the ditch” after it is welded and immediately before it is placed in the ground. Yard-applied coatings are preferred in many instances because a superior coating job can be performed under the controlled conditions of a coating plant. Further, an outer coating, such as a concrete or plastic coating, can provide protection for insulation material that may be included between the pipe and the outer coating. Yard-applied coatings are also preferred when an inner pipe is used within a second, outer pipe. This allows the inner pipe to be coated when it is more accessible, before being placed within the second pipe. One example of the use of a pipe within a pipe is placement of a bore pipe at a road crossing.
Yard-applied coatings are also preferred when more than one pipeline is to be joined in a bundle. This allows each pipe to be coated before it is placed alongside another pipe. Pipeline bundles are useful in both underground and subsea applications, particularly for transporting separate fluid streams. For example, a pipeline bundle may be used to separate an export line from a production line so as to facilitate separate metering of the export and production fluids and accommodate different tax rates. Similarly, pipeline bundles may be used to separate a gas line from a liquid line, or a water line from a hydrocarbon line. Pipeline bundles may include pipelines of different diameters. For example, a smaller pipeline may be included with a larger pipeline in a “piggyback” arrangement. Pipeline bundles may be assembled from preformed pipelines. Alternatively, pipeline bundles may be formed simultaneously as the individual pipelines are formed from pipe segments. Assembly may occur in the yard or in the field, such as on a lay barge, and the pipeline bundle may be reeled for later use.
A variety of problems exist with the use of pipe having a yard-applied coating. These include problems related to the use of insulated pipe segments that have received a yard-applied coating, the use of pipelines having gaps in the yard-applied coating in the vicinity of weld joints between pipe segments, and the use of a combination of more than one pipeline having a yard-applied coating. Such combinations include the arrangement of a inner pipeline within an outer pipeline of larger diameter; as well as pipeline bundles, in which pipelines are arranged adjacently.
With regard to insulated pipe, a problem with yard-applied coatings is the need to cover an exposed end of insulation. A wrap sealing an exposed end of insulation is commonly called a “water stop”. Insulation under a plastic coating typically does not extend beyond the coating into the gap region to either side of the weld joint, thus leaving a portion of the insulation exposed. Exposed insulation is vulnerable to water seepage, which is undesirable, as it contributes to deterioration of the thermal insulation. One technique for providing a water stop is to cover the exposed area of insulation as well as the area of coating and pipe to either side with a shrink sleeve. The shrink sleeve is formed of material that shrinks upon the application of heat, causing it to fit tightly over the region of exposed insulation. A disadvantage of this technique is its dependence on adhesive to bond the sleeve to the pipe, forming a seal. The adhesive is susceptible to deterioration, so that the bond may become unreliable.
With regard to pipe cathodically protected by a ribbon anode, a common problem with yard-applied coatings is the need to mechanically hold the anode to the pipe to prevent sagging of the anode away from the pipe when it is handled. To aid in the corrosion protection of metal pipe, particularly in subsea applications, a sacrificial anode is commonly anchored to the coated pipe and connected electrically to the pipe metal. An anode may take a variety of forms, a common form being that of a length of ribbon anode. More than one anode may be placed at intervals along the pipeline. In the case of pipeline bundles, one anode may be used to protect adjacent pipes. An anode is typically connected electrically to the pipe(s) at each end of the anode. A region of the plastic coating is removed to expose a portion of pipe, the anode is welded to the pipe in this region, and the weld area covered with epoxy for protection. Typically the weld is a thermite weld, such as is known under the tradename of CAD weld. An alternate weld is the pin weld, which penetrates further into the pipe. In either case, the welds at either end of the anode are insufficient to maintain the length of the anode close to the pipeline and prevent the anode from sagging away from the pipeline, for example when the pipeline flexes during handling.
With regard to the joint area of a pipeline, it is necessary to coat the uncoated portion of the pipe on either side of the weld joint once two lengths of coated pipe have been joined together. This portion is typically less than about three feet long. There are two known techniques for coating the weld joint area in the field. The first entails wrapping the weld joint area with a protective tape that overlaps the yard-applied coating at either end. The protective tape is not welded or fused to the yard-applied coating and therefore depends on adhesive to bond it to the yard-applied coating. One of the primary disadvantages of this technique is that it is not possible to achieve a hermetic seal of great integrity. If tape is utilized in the area of the weld joint, the seal in that area will not be of the same quality as the seal from the yard-applied coating on the remainder of the pipe, due in part to deterioration of exposed adhesive near the tape edges.
Another common technique for coating the area of the weld joint area of pipe in the field is to utilize a field mold that is fitted around the pipe. The mold forms an annular space around the weld joint, into which space is poured or injected a coating material that is compatible with the coating on the remainder of the pipe. While this process does result in the seal to the pipe surface in the area of the weld joint being of generally the same integrity as the coating on the remainder of the pipe, it lacks good adhesion to the plant-applied coating at the inte
Fernandez Julio J.
Wyke Richard L.
Conley & Rose & Tayon P.C.
Dahbour Fadi H.
Fusion Weld Corporation
Walberg Teresa
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