Abstract:
An apparatus and method for applying a protective material to the girth weld of pipe. The apparatus is particularly suited for protecting a pipe that, except for the ends adjacent to the weld, is protected by layer of a semi-interpenetrating polymer network of epoxy and polyolefin resins. Using the apparatus and method, the protective material is firmly bonded to both the exposed steel end and the pre-existing protective layer.

Description:
RELATED APPLICATION  
       [0001]     This application claims priority to U.S. Provisional Application Ser. No.: 60/810993 titled APPARATUS FOR APPLYING A PROTECTIVE LAYER TO A PIPE JOINT filed on Jun. 5, 2006 and U.S. Provisional Application Ser. No.: 60/810916 titled METHOD FOR APPLYING A PROTECTIVE LAYER TO A PIPE JOINT AND ARTICLE MADE THEREBY filed on Jun. 5, 2006, which are both incorporated by reference herein in their entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     The present document relates to an apparatus and method for coating pipes and particularly, but not exclusively, to apparatus and methods for coating girth welds on oil and gas pipelines.  
       BACKGROUND  
       [0003]     Pipelines intended for underground installation are typically manufactured in sections that are transported to the destination site and there joined into a continuous pipe by girth welds prior to burial. Since steel pipe generally requires protection from the environment to prevent corrosion, pipe sections are usually provided with a protective coating at the factory. To accommodate the anticipated welding of one pipe section to the next pipe section the protective coating typically does not go all the way to the end of the pipe sections. Typically the coating stops roughly fifteen centimeters from the end of the pipe sections. This leaves the challenge of providing an appropriate corrosion resistant coating over the welded joint and the uncoated area immediately adjacent to the end of the pipe section. This task is particular challenging as it is typically done at the job site rather than at the factory.  
         [0004]     It has been proven to be difficult to overcoat the weld joint, raw steel adjacent the weld joint, and the pre-coated portions of the pipe in such a way that the joint has sufficient corrosion resistance. When failure modes are analyzed, an underground pipe is typically much more likely to have failed at or near the joint than anywhere else along its length. Different techniques are known for protecting the weld joints from corrosion. For example, some techniques involve wrapping the joints with sealing tape, adhesive materials, or impregnating the joints with corrosion protective materials. Heat-shrinkable sleeves and spray-able compositions have also been used to protect weld joints from corrosion. In addition, apparatuses have been built to grip a pipe and apply a protective covering to the pipe. For example, see U.S. Pat. No. 5,589,019 to Van Beersel et al. However, such apparatuses can be improved upon in terms of their overall effectiveness, ease of use, reliability, and versatility.  
         [0005]     One particularly suitable method and material for coating a pipe is described in coassigned U.S. Pat. 5,709,948, “Semi-Interpenetrating Polymer Networks Of Epoxy And Polyolefin Resins, Methods Therefor, And Uses Thereof,” to Perez et al, which is hereby incorporated by reference as if rewritten herein. However, in spite of the advance in the art, there is still a need for more effective methods of applying protective coating on pipes. In particular, there is a need for more effective methods of protecting weld joints at the job site.  
       SUMMARY  
       [0006]     The present invention provides an apparatus and a method for applying a protective material to a pipe. Using the apparatus and method can be used to bond a material to both the exposed steel portion of a pipe and portions of the pipe that have pre-existing protective coatings thereon. The apparatus and method is particularly suited for covering girth weld of a pipe and the area adjacent the girth weld of the pipe. In some embodiments the area adjacent the girth weld includes pipe surface that is protected by a layer of a semi-interpenetrating polymer network of epoxy and polyolefin resins. The apparatus and method can in such embodiments be used to apply a protective coating covering different pipe surfaces.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a perspective view of a pipe coating apparatus mounted to a pipe according to an embodiment of the disclosure;  
         [0008]      FIG. 2  is a perspective view of the pipe coating apparatus of  FIG. 1  released from the pipe;  
         [0009]      FIG. 3   a  is a front view of a portion of the pipe coating apparatus of  FIG. 1 ;  
         [0010]      FIG. 3   b  is an exploded assembly view of  FIG. 3   a;    
         [0011]      FIG. 4  is a perspective view of a pipe surface preparation apparatus mounted to the pipe;  
         [0012]      FIG. 5  is an assembly view of a portion of a pipe coating apparatus illustrating the embodiment of a quick release mechanism;  
         [0013]      FIG. 6  is a perspective cross sectional view of a portion of the pipe coating apparatus of  FIG. 1 ;  
         [0014]      FIG. 7  is an end view of the portion of the pipe coating apparatus of  FIG. 6 ;  
         [0015]      FIG. 8   a  is a perspective view of a portion of the pipe coating apparatus shown in a retracted position relative to a mounting frame;  
         [0016]      FIG. 8   b  is a perspective view of a portion of the pipe coating apparatus shown in an extended position relative to the mounting frame;  
         [0017]      FIG. 9   a - f  depicts an embodiment of the linkage that enables the pipe coating apparatus to be retracted and extended and quickly attached and detached from the mounting frame;  
         [0018]      FIG. 10  is a bottom perspective view of a pipe surface preparation apparatus of  FIG. 4 ;  
         [0019]      FIG. 11A  depicts a high voltage portion of an embodiment of an electrical control system for the device of  FIG. 1 ;  
         [0020]      FIG. 11B  depicts a low voltage portion of an embodiment of an electrical control system for the device of  FIG. 1 ;  
         [0021]      FIG. 12  depicts an embodiment of a method of applying a coating material to a pipe; and  
         [0022]      FIG. 13A -D depicts an exemplary embodiment of a structure that results from execution of the method of  FIG. 12 .  
     
    
     DETAILED DESCRIPTION  
       [0023]     Referring generally to  FIGS. 1-3   b  an embodiment of a pipe crawling apparatus  100  is shown positioned over a weld joint  128  of a pipe  101 . In the depicted embodiment the weld joint  128  is located where two segments  124  and  126  of the pipe  101  have been joined together via welding. The depicted pipe crawler  100  includes a frame  102  with a tool  122  attached thereto. In the depicted embodiment the frame  102  is configured to clamp around a section of the pipe and rotate circumferentially around the pipe  101 . While the frame rotates around the pipe, the tool  122  is activated to perform a desired function (e.g. cleaning, roughing, coating).  
         [0024]     The frame  102  in the depicted embodiment is composed of two substantially curved members  104  and  106 . One end of the frame  102  is configured to pivot towards and away from the other end. In the depicted embodiment the frame  102  extends around ⅝-⅞ of the pipe when it is mounted to the pipe. In alternative embodiments, the frame  102  could extend around more or less of the pipe  101 . In the depicted embodiment the frame member are primarily constructed of aluminum. However, it should be appreciated that other suitable material can also be used, for example, steel, polymers, composites, etc. The members  104 ,  106 ,  108  and  110  of the frame  102  may be punctured, so as to exhibit holes, in order to reduce the weight of the frame  102 . In some embodiments the frame  102  weights less than about  80  pounds and is configured to mount to pipes having diameters between 36-60 inches. In alternative embodiments the weight and size of the frame vary outside of the above values. The frame  102  includes cross members  112  that provide for torsional rigidity, and also serve as a convenient location for handling (e.g., lifting and carrying) of the frame  102 .  
         [0025]     Referring particularly to  FIGS. 3   a  and  3   b , the hinge  107  is configured such that moving the handle  150  towards the pipe  101  causes pivot members  108  and  110  of the frame  102  to pivot towards the pipe  101 . In the depicted embodiment the hinge  107  is configured such that when the handle  150  is moved towards the pipe  101  the handle typically stays in a locked position until the user pulls the handle  150  away from the pipe  101 .  FIGS. 3   a  and  3   b  depict an embodiment of an over center hinge arrangement that provides this auto-locking function. Moreover, in the depicted embodiment, a frame  102  is configured such that rotating the cross member  152  about its axis enables a user to fine tune the fit between the frame and the pipe  101 . In the depicted embodiment, the cross member  152  attaches to the pivot member  108  and  110  via fastener  156  and off-center nut  154  (see  FIG. 3   b ). This configuration allows the user to adjust the position of the pivot member  108  and  110  by rotating the cross member  152 . It should be appreciated that numerous alternative fine adjustment arrangements are also possible.  
         [0026]     Referring back generally to  FIGS. 1-3   b , rollers  114  and  116  are shown mounted to the ends of the frame  102 . In the depicted embodiment the rollers  114  is mounted to the frame  102  via roller frames  118  and rollers  116  is mounted to the frame  102  via roller frame  120 . The roller frames  118  and  120  include a plurality of mounting holes  138  that can be aligned with bracket holes  140  on the frame  102  to enable the frame  102  to be adjusted to accommodate various size pipes. In the depicted embodiment, each roller  114  and  116  is shown housed within a roller frame  118  and  120 , which, in turn, is mounted to the frame  102  of the pipe crawler  100 . In the depicted embodiment, one of the rollers  114  or  116  is driven by a motor. The motor for driving a given roller  114  or  116  is housed within the roller frame itself. In an alternative embodiment, both rollers  114  and  116  are driven by motors. In should be appreciated that in alternative embodiments, any number of rollers can be used and they can be driven by motor or manually powered. It should also be appreciated that some embodiments of the frame  102  may not include rollers.  
         [0027]     In the depicted embodiment a tool  122  is shown mounted toward the middle of the frame  102  for performing work upon the pipe  101 . As described above, the tool  122  in the depicted embodiment can be used for many purposes including, for example, preparing the surface of the pipe (e.g., cleaning, roughing), or coating the pipe. The tool  122  depicted in  FIGS. 1 and 2  is an applicator  300  whereas the tool  122  depicted in  FIGS. 4 and 10  is a surface preparation device  400 . Both the surface preparation device  400  and the applicator  300  will be described in greater detail below. In the depicted embodiment when one or both of the rollers  114  and  116  begin to rotate under power of the one or more motors, the pipe crawling apparatus  100  travels around the circumference of the pipe. As the pipe crawling apparatus  100  travels around the pipe  101 , the tool  122  can perform work on the portion of the pipe facing the tool  122 . In the depicted embodiment the pipe crawler  100  is centered over the weld joint  128 , therefore, the tool  122  performs work upon the weld joint  128  and the regions of pipe  101  immediately surrounding it. It should be appreciated, that the apparatus  100  can be used to perform work along any portion of the pipe  101 . It should also be appreciated that the alternative embodiment of the depicted apparatus can have uses other than moving a tool  122  around a pipe  101 .  
         [0028]     Referring to  FIGS. 1, 2 ,  4 ,  5  and  10 , the tool  122  is shown connected to the frame  102  via a quick release mounting assembly  130  (also interchangeably referred to herein as the tool or device frame). As discussed above the tool  122  of  FIGS. 1, 2  and  5  is an applicator  300  for applying a protective material to an outer surface of a pipe  101  and the tool  122  of  FIGS. 4 and 10  is a surface preparation device  400  for preparing the surface of the pipe for cleaning and otherwise preparing the surface of the pipe for further processing. Referring particularly to  FIG. 5 , the quick release mounting assembly  130  includes mounting brackets  200 ,  202  that include a plurality of aperture that can be aligned with aperture on the frame  102  to enable the position of the tool  122  to be adjusted relative to the frame  102 . The mounting bracket configuration allows the system to be attached to a variety of different size pipes.  
         [0029]     In the depicted embodiment, the quick release mounting assembly  130  also includes a configuration whereby the tool  122  can be released from the mounting assembly  130  without the use of tool. In the depicted embodiment the tool  122  can be unlocked from the mounting assembly by moving the knobs  204  from a first position to a second position. The knobs  204  are shown in the first position in the depicted figures. The second position is the position that the knob  204  would be at if they were moved to the opposite end of the channel  206  (see  FIGS. 5, 9   a , and  9   b ). Moving the knobs  204  to the second position retracts the pins  214  thereby pulling the connecting member  216  away from the housing of the tool  122  ( FIGS. 9   e  and  9   f ). The connecting member  216  will be described in greater detail below. Once the tool  122  is unlocked from the frame of the mounting assembly  130 , the tool  122  can be slid away from the frame of the quick release mounting assembly  130 . In the depicted embodiment the tool includes guide rails  208  on either end of the tool  122  that are configured to slidably receive alignment rails  210 ,  212  that are connected to the mounting brackets  200 ,  202 . The quick release arrangement  130  enables the applicator  300  and the surface preparation device  400  to be swapped quickly and easily. It should be appreciated, not all embodiments of the disclosure include a quick release mounting assembly and in embodiments that do include such an assembly many other alternative configurations are also possible.  
         [0030]     Referring to  FIGS. 6-7 , the applicator  300  is shown in greater detail. In the depicted embodiment the applicator  300  includes a housing  302  to which three curved surfaces  304 ,  306  and  308  are anchored. The curved surfaces  304  and  306  cooperate to form a region  310  in which a coiled sheet of coating material  312  is housed. According to some embodiments, the sheet of coating material  312  is polymeric, such as a polymeric interpenetrating network coating (PINC), such as those that are described in U.S. Pat. No. 5,709,948, titled Semi-interpenetrating polymer networks of epoxy and polyolefin resins, methods therefor, and uses thereof, which is hereby incorporated by reference for all it teaches. The curved surfaces  306  and  308  also form a channel  314  through which the sheet of coating material  312  may be strung. Thus, a distal end  316  of the sheet of coating material  312  exits the channel  314  at a slot  318 . Stringing of the sheet of coated material  312  may be accomplished by insertion of a finger through slot  301  in the housing  302  (visible in  FIG. 3 ); the individual&#39;s finger may engage the material  312  and advance it through the channel  314 .  
         [0031]     The applicator includes one or more heating blankets  320 . Each heating blanket  320  generates heat when an electric current is passed through it. According to some embodiments, the applicator  300  may include but a single heating blanket  320 . According to other embodiments, the applicator  300  may include two, three, four, or more heating blankets  320 . In the particular embodiment depicted in  FIGS. 6-7 , the applicator  300  includes four heating blankets  320 . As can be seen in  FIG. 3 , the heating blankets  320  may be affixed to each of curved surfaces  306  and  308  that form the channel  314 , thereby heating both sides of the sheet of coating material  312  as it travels through the channel  314  to the slot  318 . According to some embodiments, each of the heating blankets  320  may be individually controllable, so that one heating blanket  320  may be driven with a first current, and thereby reach a first temperature, while a second heating blanket  320  may be driven with a second current and thereby reach a second temperature. According to some embodiments, a pair of heating blankets most proximal to the slot  318  may form an oven for heating the coating material  312  to a temperature just below its melting point, immediately prior to its exit through the slot  318 . Another pair of heating blankets  300  that are more distal from the slot  318  may form a pre-heat oven to warm the sheet of coating material  312  to a temperature chosen so that, as the material  312  passes through the main oven it is able to reach the desired temperature by the time it exits the slot  318 . Such an arrangement may be useful, for example, in particularly cold environments.  
         [0032]     During operation, the applicator  300  is oriented/centered over the weld joint  128 , as shown in  FIG. 1  (one must assume that the device  122  therein is an applicator  300 , rather than a Roto Peen™). The sheet of coating material  312  is strung through the channel  314  as shown in  FIGS. 6-7 , so that its distal end  316  emerges from the slot  318 , and enters a nip created by an application roller  322  and the pipe, i.e., the application roller  322  rolls along the surface of the weld joint  128 , and the exposed and surrounding regions of pipe, and the coating material  312  is compressed between the application roller  322  and the pipe. In one embodiment an electrical current is passed through the heating blankets  320 , so as to warm the coating material  312  to a temperature just below its melting point. According to one embodiment where a variety of PINC is used as the coating material  312 , the heating blankets  320  cooperate to warm the coating material  312  to a temperature of approximately 320° F. Thus, as the sheet of coating material  312  exits the slot, it is pliable, and able to conform to the surface of the pipe, which may exhibit irregularities.  
         [0033]     According to one embodiment as the coating material  312  contacts the pipe, it is further heated, as the pipe is induction heated immediately prior to operation of the pipe crawler/applicator. The pipe is induction heated to a temperature equal to or greater than the melting point of the coating material  312 . Consequently, as the coating material  312  contacts the pipe, it is nipped between the application roller  322  and pipe, and is thereby applied to the surface of the pipe, where it melts and sticks/bonds to pipe. As the pipe crawler advances around the circumference of the pipe, the material  312  unwinds and continues to advance through the channel  314 , meaning that the pipe crawler  100  leaves a strip of coating material bonded to the pipe, in its wake. In the depicted embodiment, the weld joint  128  and exposed regions of the pipe are thereby covered with the coating material, without the use of an adhesive. The pressure exerted against the coating material  312  by application roller  322  performs the additional function of removing any air bubbles that may be trapped between the coating material  312  and the surface of the pipe.  
         [0034]     Still referring to  FIGS. 6-7 , according to some embodiments, the surface of the applicator roller  322  may include grooves  600  that extend around the circumference of the roller  322 . It has been found that it is advantageous when the application roller  322  has a substantial compliance to accommodate regions of different height, e.g. the weld ridges versus the regular surface of the pipe. One way of accomplishing this is to provide the application roller  322  with the aforementioned plurality of circumferential grooves  600 . Another way of accomplishing this is by providing the application roller  322  with a very compliant layer, possibly with a thin surface layer that is less compliant but more abrasion resistant. One alternative is a roller having a soft rubber outer surface, around 15 to 30 Shore A, having a thickness of 12 mm. This outer surface of the embodiment has circumferential grooves, 8 mm deep and 6 mm wide, spaced every 8 mm apart across the width of the roll. It is contemplated that many other configurations may be used for the application roller  322 . In particular, it is contemplated that an application roller having an outer surface formed from closed cell silicone sponge tube covered by a solid silicone sleeve having a durometer of about 60 Shore A would be suitable. Such a construction is available from, for example, Ipotec, of Exeter, N.H. Although not visible in  FIG. 6 , the application roller  322  may include a plurality of longitudinal voids that penetrate the roller  322  substantially throughout the length of the roller  322 , thereby rendering the roller  322  even more pliable. In some embodiment the outer diameter of the application roller is between about 2-10 inches.  
         [0035]     Referring back to  FIG. 1 , it can be seen therein, that each of the drive rollers  114  and  116  has a recessed surface, so that only the end regions contact the pipe. The recessed regions  115  do not contact the pipe. Thus, in the depicted embodiment, the drive rollers  114  and  116  do not make contact with the weld joint  128 , which is oriented under the recessed regions  115  of each drive roller  114  and  1   16 . This arrangement has the advantage of not having the drive rollers  114  and  116  exert further pressure upon the warm, already-applied coating material  312 . In some application, such additional pressure can cause the coating material  312  to “mushroom,” or to push the uneven surfaces weld joint  128  through the coating material  312 .  
         [0000]     Engaging/Disengaging the Pipe Crawler and Pipe  
         [0036]     As shown in  FIG. 1 , the pipe crawler  100  is mounted on, i.e., engaged with, the pipe. In this configuration, the drive rollers  114  and  116  and the application roller or peripheral rollers  134  (discussed further, below) are contacting the pipe. When engaged with the pipe, approximately 110° separate the drive roller  114  and the tool  122 , and 110° separate the tool  122  from the other drive roller  116 . Because the pipe crawler  100  makes contact with the pipe at three points that encompass more than 180° of an arc of the pipe, the pipe crawler  100  is fastened to the pipe, and will not fall off.  
         [0037]     As mentioned previously, the frame  102  includes a self-locking system of hinges  107  that permit the rotatable members  108  and  110  to rotate in the direction indicated by the arrow  132 . The hinge system  107  is controlled by a handle  150 . As discussed above,  FIG. 1  depicts the handle is in the “down” or “locked” position, and the rotatable members  108  and  110  of the frame  102  are locked in place. When rotated to the “up” or “unlocked” position, the handle  150  manipulates the hinge system  107 , so as to cause the rotatable members  108  and  110  to swing outwardly, away from the pipe. The frame  102  then exhibits an opening greater than the diameter of the pipe. In this way, the pipe crawler  100  may be disengaged from the pipe.  
         [0038]     To engage the pipe crawler  100 , the handle  150  is rotated to the aforementioned “up” position, so that the rotatable members  108  and  110  are swung outwardly, and the frame  102  presents an opening larger than the diameter of the pipe. In this configuration, the pipe crawler  100  is placed upon the pipe. Next, each of the roller frames  118 ,  120  and tool frame  130  are adjusted to accommodate the diameter of the pipe. For example, turning to roller frame  118  it can be seen that the frame  118  includes a plurality of holes. The frame  118  (and therefore the roller  114 ) may be advanced or withdrawn toward or away from the pipe, by selecting which of the pair of frame holes is to be aligned with a corresponding pair of bracket holes. After such selection, a threaded fastener is passed through the aligned frame and bracket holes. (The other roller  116  and tool  122  are similarly mounted on frames  120  and  130  having holes with the same pitch, and a corresponding selection should be made, e.g., if the n th  pair of hole is selected for alignment on roller frame  118 , then the n th  pair of holes should be selected on frames  120  and  130 ). Adjustment of the frames  118 ,  120 , and  130  constitutes a rough adjustment for the diameter of the pipe.  
         [0039]     After performing the aforementioned rough adjustment, a fine adjustment may be made. As discussed above, the fine adjustment is made by loosening bolt  156  ( FIG. 3   b ), which permits member  152  to rotate about its longitudinal axis. Rotation of member  156  causes rotation of a cam, which, in turn, causes rotatable members  108  and  110  to rotate toward the pipe. Member  152  may be rotated until the rollers  114  and  116  exert the desired degree of pressure upon the pipe. At this point, the bolt  156  may be tightened, and the handle  150  is rotated to the “down position,” thereby locking the pipe crawler  100  on the pipe.  
         [0000]     Starting/Stopping the Pipe Crawler  
         [0040]     Stopping the operation of the pipe crawler  100  presents a challenge, namely, that should the advancement of the pipe crawler  100  be halted so that it can be disengaged from the pipe (as described above), the result is that the oven in the applicator  300  remains in place over a given local, until the pipe crawler  100  is disengaged. Hence, the oven tends to provide excessive heat to the local over which it is oriented, thereby tending to melt the coating material located on the pipe directly beneath the pipe crawler  100 . This can result in a flat spot on the protective coating. To avoid the flat spot, the tool  122  is slideably mounted within the frame. In the depicted embodiment, the application roller  322  is distinct from the peripheral rollers  134 . When the applicator  300  is applying protective coating to the surface of the pipe, the application roller  322  and peripheral rollers  134  are colinear, and operate as a single roller. However, the applicator  300  may be withdrawn from the pipe  101  and peripheral rollers  134  by rotation of the handle  304  (see  FIGS. 8   a  and  8   b ). Thus, to stop the operation of the pipe crawler  100 , the following steps may be taken. Initially, while the pipe crawler  100  is advancing around the circumference of the pipe and laying a protective coating, the handle  304  should be rotated to a disengaging position shown in  FIG. 8   a . Such rotation causes the applicator  300 , including the application roller  322 , to withdraw from the pipe. Notably, the peripheral rollers  134 , which are fastened to the device frame  130 , remain in place. Thus, the pipe crawler  100  maintains three points of contact with the pipe, even though the applicator and its roller  322  have been withdrawn. By virtue of having withdrawn the applicator  300 , the region of pipe directly beneath the applicator  300  is no longer subject to excessive heat. Next, the advancement of the pipe crawler  100  may be halted. For example, the pipe crawler  100  may be stopped by selection of an on/off switch to an off position, or the advancement may be halted by use of a remote control. After having halted the pipe crawler, the pipe crawler  100  may be disengaged from the pipe, as described above.  
         [0041]     To initiate operation of the pipe crawler, the pipe crawler may be engaged with the pipe, as described above. Then, the aforementioned handle may be pushed into the “engaged” position, thereby advancing the applicator  300  (chamber  310 , oven and application roller  322 ) toward the pipe and peripheral rollers  134 , so that the application roller  322  becomes colinear with the peripheral rollers  134 . The engaged position is shown in  FIG. 8   b . At this point, the advancement of the pipe crawler  100  is initiated. Again, this may be accomplished by selection of an on/off switch to the “on” position, or by remote control, etc. Next, while the pipe crawler  100  is in motion, the operator may insert his or her finger into the slot  301  defined by the housing  302  of the applicator, in order to contact the sheet of coating material  312 . Using his finger, the operator advances the coating material  312  through the channel  314 , until the distal end  316  of the sheet  312  exits the slot  318  and is nipped between the roller  322  and the pipe. Thus, the pipe crawler progresses around the circumference of the pipe, leaving a strip of protective coating stuck to/bonded to the pipe in its wake.  
         [0042]      FIG. 9   a - 9   f  further illustrates one embodiment of the mechanism, which enables the applicator  300  to be easily moved towards and away from the pipe  101  relative to the peripheral rollers  134 . The connecting member  216 , that was described above in the context of the quick release functionality of the frame  130  also plays a roll in the retracting and extending functionality of the frame  130 . In the depicted embodiment the connecting member  216  rotates when handle  304  is rotated. One end of the connecting member  216  engages a ring  217  in an off axis arrangement such that when the connecting member  216  rotates in a first direction it raises the ring  217  and when it rotates in a second direction in lowers the ring  217 . In the depicted embodiment the ring  217  is movably mounted to the guide  208  which is attached to the applicator  300  and the connecting member is movably mounted to the frame  130 . The above described arrangement enables the tool  122  (e.g., the applicator  300 ) to be raised and lowered relative to the frame  130 .  
         [0043]     Referring to  FIG. 10 , the surface preparation device  400  of  FIG. 4  is shown and described in greater detail. The surface preparation device  400  is an example of a tool  122 . In the depicted embodiment the surface preparation device  400  includes a rotating cleaning unit  404  commercially available from 3M Corporation under the trade name Roto Peen™. The Roto Peen™ contains a plurality of abrasive pads  402  (e.g., carbine disks) flexibly coupled to an axle that is rotated (e.g., pneumatically, hydraulically, by a motor, etc.). As the axle rotates, so too do the pads  402 . The pads  402  thus strike the pipe  101 , thereby removing surface contaminants and in some cases roughing the pipe surface. In the depicted embodiment the rotating cleaning unit  404  is driven by a cleaning unit motor  406  via a belt and a pair of pulleys  412 ,  410 . By activation of the motor driving the pipe crawler  100  and the motor  406  driving the rotating cleaning unit  404 , the pipe crawler  100  may travel a full 360° around the circumference of the pipe, and may thereby clean and rough the entire weld joint  128  and portions of the pipe  101  on either side of the weld joint  128 . The surface preparation device  400  is shown mounted within a housing that is similar to the housing described above with reference to the applicator  300 . This enables the surface preparation device  400  to be quickly and easily exchanged with the applicator  300 .  
         [0044]     Though in the depicted embodiment only one tool  122  is shown connected to the frame  102  at one time, it should be appreciated that multiple tools  122  could be connected to a single frame  102 . For example, in an alternative embodiment a surface preparation device  400  and an applicator  300  could both be connected to the frame  102  at the same time. In another alternative embodiment, two or more applicators  300  could be connected to a single frame  102  so that two or more layers of material can be applied to the pipe in a single rotation of the crawler  100 . In some embodiment the two or more layers can be of different composition (i.e., abrasion resistance fibers, moisture repellant coatings) and geometric configurations (e.g., widths and thicknesses). Using two applicators  300  instead of one can better enable two layers of materials to be applied to the pipe while both layers are soft.  
         [0000]     Electrical Control System  
         [0045]     Referring now to  FIG. 11A , the high voltage portion  700  of an exemplary electronic control system  702  suitable for controlling the apparatus of  FIG. 1  is illustrated. The high voltage portion  700  is conveniently adapted to connect to an external source  704  of 250 volt, 3-phase electrical energy such as is provided by many commercially available portable generators. The 3-phase mains  706  are connected via fast acting fuses  708  and  710  to a solid state relay  712 . A solid state relay such as the Din-A-Mite style B, commercially available from Watlow of Winona, Minn., is considered suitable. The solid state relay  712  is regulated by control impulses on lines  714  and  716  from the low voltage portion (depicted on  FIG. 11B ) as will be described in more particularity in connection with  FIG. 11B  below. The 3-phase power regulated by the solid state relay  712  is connected to the heating blankets  320 , conveniently via quick-disconnect connectors  718 . If additional blankets  320  are present, as will be the case in many preferred embodiments, they can be operated in parallel from the mains as the skilled artisan will readily appreciate.  
         [0046]     The mains  706  can also be used to run auxiliary equipment that may optionally be mounted on the pipe crawler  100 . For example, it is often convenient to clean and roughen the surface of the pipe after girth welding but before the application of wrapping material in order to remove oxides and promote good bonding. To accomplish this expeditiously, a ganged abrading or peening tool can be mounted on the frame  102 . The motor for such an auxiliary appliance is conveniently connected to the mains  706  by quick disconnects  724 . When such equipment is present, it is often desirable to protect the motor with an overload protector  726  and/or a interlock  728  that prevents the motor from being operated when the drives  732  and  734  (seen in  FIG. 11B ) for drive rollers wheels  114  and  116  (seen in  FIG. 1 ) are operating in a direction contrary to the natural rotation of the abrading or peening tool. Inhibit line  729 , going to the low voltage motor control  760  exerts this control as will be discussed with more particularity below.  
         [0047]     In the illustrated embodiment, the mains  706  are connected to a power supply  736  for the low-voltage portion. The power supply  736  is conveniently arranged to charge a pair of e.g. 12 volt batteries  738  and  740  that are series connected to provide 24 volts DC on terminals  742  and  744 . It is considered particularly suitable to use high-amperage, long life cells such as the Energy Odyssey PC310 batteries commercially available from BatteryMart of Woodbury, Minn. It is believed that in typical field use, the power supply can advantageously be an 8 ampere, 24-volt charger such as the model 2416SRF commercially available from Soneil of Ontario, Canada.  
         [0048]     Referring now to  FIG. 11B , the low voltage portion of an exemplary electronic control system  702  suitable for controlling the apparatus of  FIG. 7  is illustrated. The positive and negative buses,  752  and  754  respectively, are connected to terminals  742  and  744  (and from there to the batteries  738  and  740  on  FIG. 11A  as discussed above.) A heater controller circuit  746 , conveniently the model SD6C, commercially available from Watlow of Winona, Minn., is present to provide closed-loop control for the heating blankets  320 . A heat sensor  748 , conveniently a thermocouple, is positioned so that it can sense the temperature of the heating blankets  320 . Control is exerted on lines  714  and  716  (that also appear on  FIG. 11A ) to solid state relay  712 .  
         [0049]     Conveniently, the drives  732  and  734  are on the low voltage portion, although this is not a requirement. It is considered convenient for the drives  732  and  734  to be capable of both forward and reverse operation around the pipe, if for no other reason than conveniently unwinding the cord supplying the high voltage portion  700  from around the pipe. A motor controller  760 , such as the KBBC-Micro commercially available from KB Electronics of Coral Springs, Fla., is conveniently employed to coordinate the control functions, and power to the drives  732  and  734  conveniently derive from the motor controller via lines  762  and  764 . Main power to the motor controller is provided through a main on/off switch  766 . Speed control is conveniently accomplished via a variable resistor  768  connected to the motor controller  760 . The motor controller also conveniently has a fault condition indicator  770 . The inhibit line  729  is active when then drive is operating in the reverse direction.  
         [0050]     It is also considered convenient to have the drives be operable from both manual controls on the unit, and from a wireless remote control. A wireless receiver  772  may be present; a suitable wireless receiver can be adapted from a commercially available garage door controller such as model RA-423LM, commercially available from Chamberlain Group of Elmhurst, Ill. Since the ferrous bulk of the pipe is a substantial barrier to radio waves, it is considered convenient to provide an antenna  774  that extends a good way around the frame  102  so the pipe crawler  100  can respond to radio signals in any orientation around the pipe.  
         [0051]     The wireless receiver  772  includes three normally open switches  772   a ,  772   b , and  772   c  that close upon receipt of radio signals from a transmitter that signify requests for the conditions of forward drive, reverse drive and stop. Wired in parallel with normally open switches  772   a ,  772   b , and  772   c  are manual control switches  780 ,  782 , and  784  respectively that can independently mediate the conditions of forward drive, reverse drive and stop.  
         [0052]     It may be convenient to route each of the forward and reverse signals through a relay. The forward relay has a normally open contact  790   a  that closes when coil  790  is energized (these components are depicted as separated to reduce the complexity of the drawing). The reverse relay also has a contact normally open contact  792   a  that closes when coil  792  is energized (also depicted as separated.) Momentary closure on contacts  790   a  and  792   a  is sufficient to activate the forward and reverse modes respectively; the motor controller  760  can be configured to latch these modes based on a momentary contact signal.  
         [0000]     Operation  
         [0053]     The general operation of applying the coating material to a pipe according to an embodiment of the disclosure is shown in  FIG. 12 . Initially, the region of pipe that is to be coated is cleaned, as shown in operation  800 . The pipe may be cleaned with the surface preparation device  400 , as described above, with a cleaning solution, or in any other suitable manner. Typically, the region to be cleaned includes the weld joint  128 , and the exposed regions of pipe (usually about 15 cm. of pipe in either direction from the weld joint).  
         [0054]     After the pipe is cleaned, the pipe is induction heated, as shown in operation  802 . The pipe is to be heated to a temperature that is equal to or greater than the melting point of the coating material to be applied to the pipe. For example, the pipe may be heated to a temperature of about 450° F. if PINC is used as the coating material. If the coating material is a laminate (discussed below), then the pipe should be heated to a temperature equal to or greater than the melting point of the bottom layer of the laminate. It is to be understood that the pipe may be heated in ways other than induction heated, as well, as long as the region to which the coating is to be applied reaches the desired temperature.  
         [0055]     Thereafter, the coating material to be applied to the pipe is heated to a temperature just below its melting point, as shown in operation  804 . Typically, the coating material is a variety of PINC, but other coating materials may be used. In general, the coating material is a material that lacks an adhesive, and is polymeric. Upon application (operation  806 ), the material softens, conforms to the surface of the pipe (usually with the aid of an application roller), and is thereby strongly stuck or bonded thereto. In should be appreciated that alternative embodiment may include adhesives.  
         [0056]     One possible result of the preceding operations is shown in  FIG. 13A . As can be seen, the resulting structure is a pipe with a layer of coating material (in the embodiment of  FIG. 13A , PINC) applied directly thereto. No adhesive is present.  
         [0057]     In some instances, it may be preferable to use a laminate coating material. For example, a top coat may be applied over the coating material. Where the coating material is a variety of PINC, the top coat serves to protect the PINC from ultraviolet radiation. The two materials may be applied to the pipe at the same time, with the coating material softening, and adhering to both the pipe and the top coat upon application to the pipe. One exemplary useful top coat for use with PINC is MOPLEN™, which is a polypropylene based material, commercially available from Basell. The inventors of the present subject matter have tested MOPLEN™ as a top coat over PINC, and have found that it withstands temperatures as low as −50° F. without cracking.  FIG. 13B  depicts the structure that results from use of a top coat with the coating material.  
         [0058]     In some cases, it may be useful to treat the pipe with a fusion-bonded epoxy (FBE), prior to application of the coating material.  FIGS. 13C and 13D  depict the resulting structure, when only a coating material is applied ( FIG. 13C ), and when a coating material and top coat is applied ( FIG. 13D ).  
       EXAMPLE  
       [0059]     Two sections of 30 inch (76.2 cm) outside diameter pipe made from 0.5 inch (12.5 mm) thick steel were joined by means of a circumferential weld. The weld had a height of 6 mm. An additional weld of approximately the same height was made on the outside surface of one of the sections in a direction parallel to the long axis of the pipe in order to simulate pipe made by rolling and welding.  
         [0060]     The ends of the welded pipe were coated with a 0.06 inch (1.5 mm) thick layer of a semi-interpenetrating polymer network of epoxy and polyolefin resin, generally as described in copending and coassigned U.S. patent application Ser. No. 60/707332, “Method and Kit for Providing Interpenetrating Polymer Network as Coating for Metal Substrate,” Perez et al (Attorney docket number 59519US003), which is hereby incorporated by reference as if rewritten. The coating ended so as to leave a gap of exposed steel approximately 6 inches (15.20 cm) wide on either side of the girth weld. This experimental set-up approximated the situation of a field weld having just been completed on steel pipe treated with Scotchkote™ 224N corrosion protection compound, commercially available from 3M Company of St. Paul, Minn. The steel in the exposed gap was then cleaned and roughened with a Roto Peen™ flap wheel, commercially available from 3M Company of St. Paul, Minn.  
         [0061]     A wrapping apparatus generally as illustrated in  FIG. 1  and described above was constructed. The film magazine was loaded with a roll of film 25 mils (0.64 mm) thick and 6 inches (15.3 cm) wide, composed of the same semi-interpenetrating polymer network of epoxy and polyolefin resin as described above as coating the pipe ends. The gap oven was supplied with two 600 watt blanket heaters as the first and second heaters, commercially available as catalog number SHSO1300 from Tempco of Wood Dale, Ill. A pre-heater was present, provided with two 1300 watt blanket heaters as the first and second pre-heaters, commercially available as catalog number SHS01299 from Tempco. The heaters in the gap oven were set to heat the pipe-facing side of the film to 160° C. and the outside-facing side of the film to 140° C. The laydown roller had a soft rubber outer surrounding a steel shaft. The outer had a durometer of 20 to 30 Shore A, having a thickness of 12 mm. This outer had circumferential grooves, 8 mm deep and 6 mm wide, spaced every 8 mm apart across the width of the roll.  
         [0062]     The welded pipe was then exposed heat energy from six 3000 watt heaters, each 6 inches wide by 20 inches long (15.3 cm by 50.8 cm) commercially available from Tempco of Wood Dale, Ill., positioned so as to heat up the pipe from the inside out. The wrapping apparatus was then clamped onto the pipe and activated to dispense heated film from the magazine onto the heated surface of the pipe, centered on the joint. The drives were set to propel the apparatus at a circumferential speed of 7.6 cm/sec. When the joint was completely wrapped once, the apparatus was halted and removed from the pipe. The pipe was allowed to cool to room temperature and then inspected visually. It was observed that the coating was a very uniformly deposited protection that adhered not only to the cleaned steel but also to the previously applied protective coating on either side of the cleaned area.  
         [0063]     While the invention has been particularly shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various other changes in the form and details may be made therein without departing from the spirit and scope of the invention.