Patent Application
20120090765
This patent claims the benefit of and priority to Canadian patent application 2,658,494, filed Mar. 13, 2009, under the title “Apparatus for Heating Heat Shrink Sleeves”.
The content of the above patent application is hereby expressly incorporated by reference into the detailed description hereof.
The invention relates to apparatus for heating an elongate tubular article, for example, heating a heat shrinkable sleeve applied around a welded pipe joint during pipeline construction, or for pre-heating a welded pipe joint before treating or coating.
Usually, pipe for pipeline construction is coated with a mainline polymer coating leaving the ends of the pipe bare to allow the exposed ends to be welded together at a pipe joint. There are several different ways used in the art to coat pipe joints. One such way is the use of a heat shrinkable sleeve applied around the welded pipe joint. The sleeve is fitted to the pipe joint, then heat shrunk down onto the joint. Alternatively, a film or tape wrapping can be used. This can be, for example, a polypropylene film, which is wrapped around the pipe joint. The film or tape wrapping requires use of heat and tension to fuse the wrapping to itself as it is applied to the pipe joint. Typically, the film or tape wrapping is also applied over the ends of the pipeline coating, to form a complete coating of the exposed pipe. Such film or tape wrapping typically requires pre-heating of the exposed pipe to facilitate or enable fusion of the wrapping to the pipe. A further alternative way of coating the welded pipe joint is an injection moulding method, whereby the exposed pipe joint is encased with a mould, and a polymer, such as polypropylene or polyurethane, is pressure injected into the mould. The polymer is allowed to cool, and the mould is removed, leaving a pipe joint that is coated with polymer. As can be appreciated, such a method also benefits from the pre-heating of the exposed pipe, so that the injected polymer is not cooled too quickly upon contact with the pipe and a good adhesion to the substrate is affected. These injection moulding and film or tape wrapping methods have an advantage over the use of heat shrinkable sleeves in situations where the mainline coating is extremely thick, and the joint cavity needs to be filled.
In the case of heat shrinkable sleeves applied around a welded pipe joint during pipeline construction, typically, such sleeves are heated and shrunk down onto the joint or other article using a hand held flame torch (see, for example, U.S. Pat. No. 4,472,468, entitled “Heat Shrinkable Covering and Method for Applying Same”, issued Sep. 18, 1984, which is incorporated herein by reference). In some cases, this manual operation produces an imperfect installation because of air trapped underneath the shrunk down sleeve. This can arise when the ends of the sleeve are shrunk down before the middle portion of the sleeve. Artful application of the torch is critical. If the torch is tilted outwardly the end zones of the sleeve may shrink-first leading to air entrapment. Windy conditions may spread the flame and shrink the end zones of the sleeve prematurely. Further, unless the torch is moved carefully, the torch flame may burn the sleeve and cause it to split. Where a large area needs to be heated, it becomes difficult or impossible to maintain the heat while the sleeve is being shrunk; this leads to wrinkling of the sleeve, imperfect installation due to trapped air, tearing, or scorching of the heat shrink material. Sometimes, it also results in improper or incomplete adherence of the heat shrink material around the welded pipe joint.
Before the field joints coatings are applied over the joint, the joint has to prepared in prescribed manner required for the coating type. Typically, for heat shrink sleeves, tapes and wrap systems, and injection molding, the steel is usually grit blasted, and in rare cases, power wire brushed to obtain white metal or near white metal finish. The mainline coating is usually prepared in order to clean it, and often impart roughness by abrading or light grit blasting. The joint usually requires preheating to remove moisture, but more importantly to achieve certain temperature consistent with coating type to obtain adhesion or fusion of the joint coating to the steel and to the mainline coating. For example, for polypropylene type shrink sleeves, where the adhesive may have melting point of around 155° C., the preheat of the steel is often 180° C. The preheating is often done by using induction heating, which heats the steel only, and indirectly the mainline polymeric coating. Since the exposed steel is directly heated, it can be taken to the desired temperature readily, however, the mainline coating gets heated via the heat conducted by the heated steel underneath. Therefore there is time lag for the coating surface to heat up, and there is often 40-100° C. temperature difference on the steel and coating surface temperature, depending on the coating thickness. For example, on a 610 mm diameter pipe with a wall thickness of 25 mm, when the joints steel temperature reaches 180° C., a polypropylene coating of a 5 mm thickness may only reach 100° C.-120° C. Therefore when subsequently applying a heat shrink sleeve over a joint with such substrate heat profile, the sleeve requires more heat to be applied near the ends overlapping over the mainline coating in order for the sleeve to adhere to the exposed steel and the mainline coating to form a sound protective seal.
The differences in materials in the exposed steel, and the mainline coating result in different heat requirements during the preheating. In some cases, for example, excess heat at the pipe joint may overheat the mainline coating and damage it. During preheating, more intense heat is generally required on the exposed steel, and less intense heat being required the coated pipe, due to the properties of the material used in the mainline coating. For example, where a pipe has a thick mainline coating, made of polymeric material, the exposed steel will have different specific heat, heat resistance, retention and conductivity characteristics than the mainline coating. Thus, the exposed steel may require a more intense heat (which would damage the mainline coating), but may require it for a shorter amount of time, with the mainline coating requiring a lower heat, for a longer period of time, in order for the heat to absorb into the coating thickness. In addition, where heat is applied using a hand held flame torch, the operator of the torch must bear in mind the differences in thicknesses of the different zones to be coated, and radially adjust the torch position accordingly. For example, the thickness of the mainline coating may be substantial, and the operator may need to move the torch a substantial distance in order to keep the same distance between the torch and the area to be heated.
The sizes and configurations of torches and heating implements vary greatly in the field, as do the sizes and configurations of the pipes to be treated. Sometimes, large powerful torches are used. These tend to flare out greatly and do not allow focused heating of the shrink sleeve, thereby causing air entrapment due to prematurely shrunk sleeve ends. Sometimes four torches are used to shrink a sleeve to get fast production rates, with two operators on one side of the pipe and two on the other. This practice makes it very difficult to selectively heat the middle portion of the sleeve before the ends, and makes it near impossible to apply even, consistent heat throughout the area to be heated, to accurately control the amount of heat applied to different areas to be shrunk, or to accurately control the order in which the various areas are to be heated. Often, in order to obtain proper adhesion of the sleeve, it is required to maintain a minimum preheat temperature of the substrate, usually steel pipe and the mainline coatings on the pipe sections adjacent to the joint. Even when fewer area is to be heated, or where less torches are employed, certain areas, for example, the mainline coating adjacent the opposite end of the pipe, tends to have cooled below the minimum preheat temperature, so that the sleeve does not bond thereto. Therefore during the shrinking operation, extra prolonged heat has to be applied to sleeve area overlapping onto the mainline coating in order raise the adhesive-mainline coating interface to sufficient temperature to achieve a sound bond. With the flame torches, this is difficult as prolonged heating can scorch and damage the sleeve, and sometimes lead to splitting. The need for the extra prolonged heating is exacerbated by the fact that during the preheating of the joint, the mainline coating surface maybe 40° C.-100° C. cooler than the adjacent steel, as described earlier. Therefore, focused prolonged heating is imperative to achieve a good bond on the overlap coating.
Similar considerations should be taken into account when pre-heating a pipe joint prior to film or tape wrapping, or injection moulding.
The present invention provides apparatus that at least in preferred embodiments may avoid the above-noted problems.
According to one aspect of the invention is provided an apparatus for heating an elongate tubular article, comprising a frame member adapted to be disposed around said article, said frame member having a heater device adapted to heat the elongate tubular article and disposed on or proximal to an inner surface of said frame member, and a controller for operating the heater device.
According to another aspect of the invention is provided an apparatus for heating a heat shrinkable sleeve applied around an elongate tubular article, comprising a frame member adapted to be disposed around said article, said frame member having a heater device adapted to heat the heat shrinkable sleeve and disposed on or proximal to an inner surface of said frame member, and a controller for operating the heater device.
According to a further embodiment, the heater device forms a surface which envelops said elongate tubular article when the apparatus is disposed around said article.
According to yet a further embodiment, the heater device forms a surface which envelops said heat shrinkable sleeve when the apparatus is disposed around said sleeve.
According to a further embodiment, the heater device comprises a thin stamped sheet, foil strip.
According to a further embodiment, the thin stamped sheet or foil strip is configured in a sinusoidal or linear configurations to form a heating plane providing relatively even heat.
According to a further embodiment, the heater device comprises infrared elements in the form of for example, quartz tubes or ceramic tiles.
According to a further embodiment, the heater device comprises diffused gas combusting devices, powered for example by propane or natural gas, such as catalytic panel heaters.
According to a further embodiment, the heater device comprises at least two independent heating zones adapted to heat respectively at least two distinct longitudinally spaced zones of the elongate tubular article, and said controller allows for the operating of the heating zones simultaneously or sequentially.
According to a further embodiment, the two independent heating portions are slidable longitudinally with respect to the tubular article from an adjacent, central position to a spaced position, as shown for example in
According to a further embodiment, the heater device comprises at least two areas of different inner surface diameter when disposed around said article.
According to a further embodiment, the at least two areas comprise a first area and a third area at either end of a second area, wherein the inner surface diameter of said second area is smaller than the inner surface diameter of said first area and said third area.
According to yet a further embodiment, the apparatus has a first, a second, and a third independent heating zones each corresponding to the first, second, and third area.
According to a further embodiment, the apparatus further comprises a reflecting layer and/or an insulating layer.
According to yet a further embodiment, the heater device is mounted onto said reflecting or insulating layer.
According to yet a further embodiment, the reflecting or insulating layer is made of a refractory material.
According to a further embodiment, the frame member comprises a clam shell device having a hinge extending longitudinally along one side.
According to a further aspect of the present invention is provided a method for heating a heat shrinkable sleeve applied around an elongate tubular article, comprising disposing adjacent to the sleeve a heater device as herein described, and heating said sleeve with said heater device.
According to a further embodiment, the heater device comprises at least two heater portions, and said method comprises heating at least two distinct longitudinally spaced zones of the sleeve simultaneously or sequentially with said respective heater portions.
The invention provides apparatus for heating an elongate tubular article, and/or for heating a heat shrinkable sleeve applied around an elongate tubular article. The apparatus comprises a frame member adapted to be disposed around said article, the frame member provided with a heater device adapted to heat the article and/or the sleeve surrounding said article. The invention also provides a controller for operating the heater device. Optionally, the heater device can comprise two or more independent heater portions adapted to heat respectively two or more distinct longitudinally spaced zones of the sleeve, and the controller is able to operate the heater portions simultaneously or sequentially, and/or at different heating intensities/wavelengths/temperatures. The heater device can comprise two or more regions of different diameters, to better conform to an elongate tubular article of varied diameter.
The heating element can be any known form of heating element. In certain embodiments, the heating elements comprise infrared electrical elements, such as Unitube heaters available from Casso-Solar Corporation, Pomono, N.Y., United States of America. These infrared elements may be in the form of, for example, quartz tubes or ceramic tiles. Alternatively, they may comprise diffused gas combusting devices, powered for example by propane or natural gas. Examples of these include gas catalytic heaters available from Casso-Solar and from CCI Thermal Technologies, Edmonton, Alberta, Canada. Further examples include burners comprising metallic or ceramic matrixes that diffuse the flame and then radiate the heat outwards, such as Fibergas-II™ heaters, again from Casso-Solar, and heaters using gas diffused through perforated ceramic matrices, as supplied by Infragas S.p.a., Caselle Torinese, Italy.
In a particularly advantageous embodiment, thin film or otherwise flexible infrared electrical elements are used (also called “foil”, or “flexible ribbon” heating elements). Examples of such elements include the V-series medium wavelength infrared panel heaters available from Casso-Solar Corporation, Pomona, N.Y., United States of America. Other examples can be found throughout the art, for example, as described in EP 0417375, incorporated herein by reference. The thin film elements discussed herein also comprise within their scope strips, sheets, planar thin foil heaters, corrugated ribbon foil, carbon loaded film, metal film photopatterned with runs of graphite material, conductive material sprayed or doctor bladed on a support medium, expanded metal, or wire resistive elements, such as sinuated wire. The V-series, for example, are stamped thin metal sheets having low mass for fast heating/cooling and minimal thermal lag, and can be attached to a high temperature insulation board having low thermal conductivity, low thermal mass and low heat capacity to minimize stored heat. Thin film elements can be mounted on a high temperature insulating material and/or onto refractory insulating material in a variety of configurations, including linear, sinusoidal, or other configurations, as required or desired by the heating configuration and sequence. The use of a thin film or otherwise flexible heating element has numerous advantages. A thin film or otherwise flexible heating element facilitates the manufacturing of the apparatus in varying shape and size, to tightly conform to the area to be heated. The thin film or otherwise flexible heating element also allows customization of apparatus size and shape in other ways, such customization not being limited by the standard sizing and rigidity of quartz tubes or ceramic tiles. The thin film can simply be stamped to the size required. In the case of applying a heat shrinkable sleeve around an elongate tubular article such as a coated pipe, the apparatus can be tapered in the middle, to account for the difference in radius of the uncoated pipe, such as the pipe proximal to the pipe joint, and the radius of the mainline coating; in such cases, a thin film or otherwise flexible heating element can be easily shaped to conform to the varied shape of the apparatus. In this manner, the distance between the pipe joint or heat shrinkable sleeve and the heating element can be made more consistent, allowing for an improved and more even heat distribution along the various areas to be heated. This improved and more consistent proximity may thus permit even closer control of the heating, avoiding problems of burning or splitting of the sleeve. This improved and more consistent proximity is especially advantageous in applications wherein a pipe joint is preheated, and the mainline coating is very thick. Such joints would necessarily have a cavity at the exposed steel area, and a very thick coating adjacently. The use of a heater the foil elements can allow custom design to facilitate the proximity of the heater to the exposed steel, the sloping chamfer of the mainline coating, as well as the top surface of the mainline coating. Thus most efficient heating could be imparted to all surfaces with careful temperature control without burning or oxidising the polymeric coating.
A further advantage of a thin film element is that, compared to the other alternatives described herein, they are more robust and less breakable in field conditions. The film elements are flexible, and when attached to a solid base of insulating material such as refractory insulating material, they are near unbreakable, compared to a quartz tube or a ceramic tile. The thin film elements are also more resistant to contact to water, which may occur in field conditions, for example, on off shore pipe lay-barges. In such conditions, heat shrinkable sleeves are often water cooled, since soft (still hot) sleeves can get damaged by the stinger rollers which support the pipe as it is released into the ocean. Cold water used to cool the pipe can splash onto the heating element as the heating element is removed or placed on the pipe. In the case of quartz tubes or ceramic tiles, this rapid change in temperature can cause cracking oii, other damage to the heating element, whereas for the thin film elements, there is less risk of such damage, with the cold water simply steaming off the element.
By using stamped thin metal strips, different areas can be heated to different temperatures or at different time periods within the heat shrinking process, simply by having separate heating elements applied to different areas of the apparatus, and having each of these separate heating elements controlled individually by the controller. The different heating elements may be individually thermostatically controlled by the controller, and/or may have different heating characteristics (for example, made of different substrates or having a different coil thickness) to enable the variation in heating. With this arrangement, at least in preferred embodiments, the heating of the sleeve can be carefully controlled to shrink down the middle zone of the sleeve before the end zones, avoiding air entrapment. Moreover, in certain embodiments, once the middle zone of the sleeve is shrunk, the end zones can be shrunk simultaneously, providing for fast installation before the mainline coatings cool down below a required preheat temperature. In case of the preheating of a pipe joint, this arrangement also permits heating the areas of bare pipe to a higher heat level than the areas of coated pipe, thus preventing damage to the pipe coating while providing the bare pipe with optimal heat. Though this controlled heating can be done with the other heating elements described, a further advantage of utilising thin film elements is that the element heats, and cools, much more rapidly. In many cases, the thin film element will cool down with 5-10 seconds of deactivation, and will heat up in a similar time frame. For example, certain metallic foil type elements can have a temperature rise of 700 degrees Celsius, in 10 seconds. Others can cool down in as little as 2 seconds. This means that the controller can control the zone changes much more effectively, rapidly, and precisely. It also means that the pipe joint can be heated, or the sleeve can be shrunk, much more rapidly. This rapid cooling of the thin film elements also adds a safety feature when used in the field, such as on an offshore pipe lay-barge, where work space is crammed—worker safety is dramatically improved, since the heating elements are much cooler when the apparatus is handled, for example, when the apparatus is clamped to, or removed from, a pipe. In addition, the rapid heating and cooling of the film elements can result in significant time and energy cost savings, up to 20%.
The apparatus can also be used before and after application of the heat shrinkable sleeve. For example, the apparatus can be placed around the welded pipe joint, for preheating the welded pipe joint before application of the heat shrinkable sleeve. Once the pipe has been preheated to a desired extent (i.e. after a pre-set temperature or a pre-set time has been reached), the apparatus (including the heating element) can then easily be removed, and the heat shrinkable sleeve can be applied. The apparatus may optionally then be placed around the welded pipe joint again, and heat re-applied, to shrink the heat shrinkable sleeve. This permits a much more consistent and even pre-heating of the pipe joint than previous methods, where, often, different areas of the pipe joint were pre-heated at different times, with resultant unevenness in cooling before the sleeve was applied.
The apparatus can also be used to preheat the pipe joint for other coating applications, for example, before the application of a film or tape wrapping, or an injection moulding of a coating. As would be appreciated, a further advantage of using the apparatus in certain embodiments is that the entire pipe joint or sections of the pipe joint can be brought to a desired temperature, at the same time, and the apparatus can be quickly removed and the application of coating can be started much more quickly than in more traditional preheating methods.
Preferred embodiments are described with reference to the accompanying drawings, wherein like reference numerals indicate like parts.
Referring firstly to
The support structure 35 carries a heater device comprising in this example heating element layer 32. The support structure 35 also has an insulating/reflecting layer 30, which reflects heat emitted from heating element layer 32 and insulates the exterior of the support structure 35. The insulating/reflecting layer 30 may be made of any material known in the art to have heat reflection or insulating properties, for example, an insulating foam or a refractory material.
In a preferred form, as seen in
A controller 33, which may be (as shown) separate from support structure 35 or which may be integrated within it, controls the level and/or intensity of heat output from heating element layer 32. The controller 33 may be thermostatically controlled, may be controlled through the measurement of resistance in heating element layer 32, may be a timer, or may simply be an operator—selected switch.
In the example illustrated in
In the example illustrated in
In a preferred form, the support structure 35 comprises a clam shell device as seen in
In one embodiment, the heating element layer 32 consists of thin circuit nickel chromium alloy wire sandwiched between a heat resistant polymer such as polyimide or polyester. Other embodiments comprise a heating element layer 32 made from chromium aluminum and iron alloy or nickel chromium and iron alloy. In one embodiment, the heating element layer 32 is a thin stamped sheet or foil having a chemical composition in percent by weight as follows: 0.02-0.10% C; 0-0.10% Mn; 19.5% Cr; about 56% Ni; 4.25% Mo; 0-2.0% Fe; 13.5% Co; 1.3% Al; 9.1% Cu; 0-0.15% Si; 0.003-0.01% B; and 3% Ti.
Following completion of the shrinking, the halves 37a and 37b of the clam shell device are pivoted to the open position to facilitate moving the apparatus relative to the pipe, to align it with a further pipe joint, and the above described cycle of operation is repeated.
As will be appreciated, the apparatus may have any number of heat zones for any desired application. In addition, the controller 33 may be actuated manually or under the control of an automatic primary controller, optionally with pre-set temperature and timing for a selection of a variety of pipes, mainline coatings 22, and/or applications. For example, in some applications, the apparatus would be used for preheating a pipe 20, pipe joint 25, and mainline coating 22 following the welding of the pipe joint 25 and before the application of a film or tape wrapping or an injection moulding coating. In such applications, of course, sleeve 26 would be absent. In such applications, the controller may be pre-set for different temperatures for the different areas of the heating element. For example, the entire heating element may be set for a simultaneous 5 minute heating, but the center zone 42 would be set to heat at a much higher intensity and temperature than transition zone 44, which, in turn, would be set to heat at a higher intensity than external zone 46. In this manner, the pipe 20 and pipe joint 25 can be preheated to a desired temperature, while avoiding damage to mainline coating 22, which would be heated with a lower intensity to the desired temperature. Alternatively, for example in cases where mainline coating 22 is especially thick (for example, 100 mm thick), it may be desired to heat external zone 25 for an extended period of time (for example, 10 minutes) at a relatively low intensity, to allow the heat to permeate the mainline coating 22. In cases like this, the controller can be set to heat external zone 25 for 10 minutes, with transition zone 44 and center zone 42 activating for the last 5 minutes of such time period. In this example, transition zone 44 would be useful as an interface zone, heating only for 5 minutes, but heating at an intensity similar to external zone 25, to avoid damage at the interface between the mainline coating 22 and the pipe 20. Center zone 42 would heat at a much higher intensity, since pipe 20 can typically withstand (and may require) a higher intensity heat due to much faster heat dissipation properties as compared to mainline coating 22. Using this heating method, at the end of the 10 minutes, all heated sections of pipe 20 and mainline coating 22 are at the desired preheat temperature, suitable for film or tape wrapping, injection moulding, or application of a heat shrinkable sleeve.
Of course, the apparatus as illustrated in
In use, the heating portions 64 and 66 can be in this example operated simultaneously and are moved progressively outwardly from the position shown in
In the final stage, as seen in
In one modification (not shown) a structure 35 similar to that shown in
The structure shown in
In this manner, the mainline coating 22 is subjected to heat first, since, in some applications, it will retain heat longer than pipe 20.
Advantages of preferred embodiments of the present apparatus, in addition to those mentioned above, include the following:
The apparatus offers high speed automatic operation wherein the heating of successive zones of the sleeve eliminates air entrapment.
The support structure such as insulating/reflecting layer 30 shields the interior of the apparatus so that its operation is not impaired by windy conditions.
The flexible thin film heating element allows for a shape whereby pipes having thick mainline coatings 22 can be accommodated through the use of a narrower inner portion which ‘hugs’ the exposed pipe 20 proximal to the weld 24.
Since the apparatus covers the entire sleeve, once the middle zone of the sleeve is shrunk, the end zones may then be shrunk simultaneously, providing fast installation of the sleeve before the mainline coating 22 cools down below the desired preheat temperature.
Although all of the figures show the apparatus for use with sleeve 26, it would be appreciated that the apparatus could also equally be used for pre-heating of the pipe joint, either before application of the sleeve 26, or for different applications, such as pre-heating of a pipe joint before tape or film wrapping, or before injection moulding of a coating around the pipe joint. In such applications, sleeve 26 would, of course, be absent.
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2658494 | Mar 2009 | CA | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CA2010/000334 | Mar 2010 | US |
| Child | 13230258 | US |
