Patent Publication Number: US-6712668-B2

Title: System and method for electropolishing nonuniform pipes

Description:
TECHNICAL FIELD 
     The present invention relates to the field of electrochemical processing, and more particularly to an apparatus and method for uniformly polishing the interior of pipes which include both uniform portions and nonuniform portions. The predominant current usage of the present inventive improved pipe electropolishing apparatus and method is in the in place polishing of the inner surfaces of pipes. 
     BACKGROUND ART 
     It is known in the art to deposit and/or remove materials by passing an electric current through a fluid electrolyte which is in contact with a conductive electrode. Materials are exchanged between the electrolyte and the electrode depending upon the direction of current flow and the ionization of materials to be deposited on or removed from the electrode. Electroplating is a well known application of this general method. Electropolishing is also well known in the art. In the electropolishing process, irregularities and deposits on a surface are removed by causing such to be drawn into the electrolyte solution. 
     An example is the in place electrochemical polishing of a pipe. In such an example, a cathode is drawn through the pipe while an electrolyte solution is simultaneously piped through the pipe. The pipe acts as an anode and is electrochemically polished in the process. Since the electrolyte solution must be continuously pumped through the pipe during the process, it is most practical to recirculate the solution. 
     A piping system will generally consist of uniform (e.g., straight, no welds or joints, etc.) sections of pipe and of nonuniform (e.g., bent, welded joint fittings, etc.) sections joining such uniform sections. For various reasons, it happens that the nonuniform portions of pipe tend to become more pitted and uneven during manufacture and in use than do the uniform portions. An alternative in the prior art has been to over polish the uniform sections in order to make certain that the nonuniform portions are sufficiently polished on the interior. However, this alternative is wasteful of time, materials, and energy. The only other alternative has been to polish the interior of the pipes to a lesser degree, leaving the nonuniform portions less than perfectly polished. However, this alternative is much less than desirable, since leaving an uneven surface on the interior of the nonuniform portions continues to cause the same problems which necessitated the polishing in the first place. 
     It would be advantageous to have an electropolishing system which would adequately polish nonuniform pipe segments without over polishing the uniform segments. However, to the inventor&#39;s knowledge, no such system has existed in the prior art. All prior art systems have required either over polishing uniform sections or under polishing nonuniform sections, since there has been no provision for adjusting the amount of polishing in the different sections, as required. 
     SUMMARY 
     Accordingly, it is an object of the present invention to provide an apparatus and method for evenly polishing all portions of the interior of a pipe system. 
     It is still another object of the present invention to provide an apparatus and method for polishing nonuniform portions of a pipe more than uniform sections thereof, such that the end result will be a generally evenly polished finish in all portions of the pipe. 
     It is yet another object of the present invention to provide an apparatus and method for varying the amount of polishing accomplished in an electropolishing system, depending upon the location of the polishing apparatus. 
     It is still another object of the present invention to provide an apparatus and method for adapting a pipe electropolishing apparatus such that the amount of polishing accomplished is adapted to specific portions of the pipe. It is yet another object of the present invention to provide a method and apparatus for controlling the amount of polishing accomplished in a pipe electropolishing system according to the amount of polishing required in particular sections of the pipe. 
     Briefly, a known embodiment of the present invention is an improved in place electropolishing apparatus for polishing a pipe. According to one described embodiment of the present invention, a cathode is drawn through a pipe at a variable rate such that the cathode can be slowed down in nonuniform sections of the pipe, wherein more polishing is required, and further such the cathode can be speeded up in uniform sections of the pipe, wherein less polishing is required. In another described embodiment of the invention, voltage to the cathode is increased while the cathode is in nonuniform portions of the pipe and decreased when the cathode is in uniform portions of the pipe. 
     According to one embodiment of the present invention, it is desirable to know where within a pipe the electrode is at any given time during the processing process. This can be accomplished in a number of ways, including but not limited to methods and means specifically discussed herein. For example, the cable which pulls the cathode through the pipe could be encoded, for example with colored or magnetic markings or the like, such that the position of the cathode can be generally determined by keeping track of how much cable has been pulled through. Another means would be measure the resistance and/or capacitance between the cathode and a measuring electrode placed at the end of the pipe and/or at various points along the pipe. Other means for detecting the position of the cathode could rely upon the fact that there is a significant amount of heat generated at the location of the cathode during the process. This heat could be detected by an infrared camera, by thermisters placed at specified locations along the pipe, or by marking the pipe at various locations and/or intervals with a heat sensitive crayon that changes color or melts due to heat generated by the electropolishing process. 
     An advantage of the present invention is that all portions of the interior of the pipe are polished sufficiently to cause such interior surface to be smooth, but not overpolished. 
     Another advantage of the present invention is that more polishing is accomplished in nonuniform portions of the pipe, where it is needed, than in uniform sections, wherein less polishing action is adequate. 
     A further advantage of the present invention is that electricity and time are not wasted in polishing uniform sections of the pipe more than is required. 
     Still another advantage of the present invention is that the polishing process can be speeded up, while still adequately polishing nonuniform portions of the pipe. 
     Yet another advantage of the present invention is that uniform portions of the pipe are not worn away by unnecessary polishing. 
     These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of modes of carrying out the invention, and the industrial applicability thereof, as described herein and as illustrated in the several figures of the drawings. The objects and advantages listed are not an exhaustive list of all possible objects or advantages of the invention. Moreover, it will be possible to practice the invention even where one or more of the intended objects and/or advantages might be absent or not required in the application. 
     Further, those skilled in the art will recognize that various embodiments of the present invention may achieve one or more, but not necessarily all, of the above described objects and advantages. Accordingly, the listed objects and/or advantages are not essential elements of the present invention, and should not be construed as limitations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is block diagrammatic view of an example of an in place pipe electropolishing system; 
     FIG. 2 is a more detailed view of a portion of the cable and cable mark detector of FIG. 1; 
     FIG. 3 is a block diagrammatic view of an example of an alternative in place pipe electropolishing system; and 
     FIG. 4 is a flow diagram depicting an example of the present inventive method. 
    
    
     DETAILED DESCRIPTION 
     The embodiments and variations of the invention described herein, and/or shown in the drawings, are presented by way of example only and are not limiting as to the scope of the invention. Unless otherwise specifically stated, individual aspects and components of the invention may be omitted or modified, or may have substituted therefore known equivalents, or as yet unknown substitutes such as may be developed in the future or such as may be found to be acceptable substitutes in the future. The invention may also be modified for a variety of applications while remaining within the spirit and scope of the claimed invention, since the range of potential applications is great, and since it is intended that the present invention be adaptable to many such variations. 
     Unless otherwise stated herein, component parts of the invention will be familiar to one skilled in the art, and may be purchased or readily manufactured accordingly. Also, unless otherwise stated herein, substitutions can be made for the components described, and each of the individual components, except as specifically claimed, is not considered to be an essential element of the invention. 
     A known mode for carrying out the invention is an in place pipe electrochemical polishing system  10 . The in place pipe electrochemical polishing system  10  is depicted in a block schematic diagrammatic view in FIG.  1 . As one skilled in the art will recognize, some of the relevant component parts of the in place pipe electrochemical polishing system are a cathode  14 , a cathode puller cable  16 , a cable puller  18 , a valve  20 , an electrolyte reservoir  22  for containing a supply of an electrolyte  24 , and an electrolyte pump  26 , all of which are provided for the purpose of polishing the interior of a pipe  28 . In the electrochemical polishing process, the cathode  14  is drawn toward the cable puller  18  by the cathode puller cable  16 , while current is applied through the cathode  14  from a power supply  30 . The current flows through the electrolyte  24  in the pipe  28 , which shares a common ground with the power supply  30  such that the pipe  28  acts as an anode and the interior thereof is polished, according to the known principles of electropolishing. During the process, the electrolyte  24  is generally pumped to flow through the pipe  28  in a direction opposite that in which the cathode  14  is being drawn. The valve  20  prevents the electrolyte  24  from escaping the pipe  28  while allowing the cathode puller cable  16  to be pulled therethrough. 
     In the particular example of the in place polishing system  10  shown in the view of FIG. 1, two filters  34  are placed in the path of the electrolyte to insure that particulate matter removed from the inside of the pipe  28  is removed from the electrolyte  24  solution as it is recirculated through the in place polishing system  10  by the electrolyte pump  26  and an electric heater  36  and temperature indicating control  38  are provided in the path of the electrolyte  24 . In this example, the electric heater  36  and the temperature indicating control  38  are located in the electrolyte reservoir  22 . Also, in the present example of the invention, a collector sump  40  catches the electrolyte  24  at it flows out of the pipe  28 , and a collector sump pump  42  pumps the electrolyte  24  from the collector sump  40  to the electrolyte reservoir  22 . A heat exchanger  44  is provided in the path of the electrolyte  24  with a chiller  46  operatively connected thereto. The chiller  46  is a conventional refrigeration unit and pump, and the heat exchanger  44  is adapted to transfer heat from the electrolyte  24  in the pipe  28  to the chiller  46 . 
     In the embodiment of the invention shown in FIG. 1, the cable puller  18  is a variable speed puller and the cathode puller cable  16  is marked such that a cable mark sensor  50  can sense how far the cable has been pulled. FIG. 2 is a more detailed view of the cable mark sensor  50  and a portion of the cable  16  showing a plurality of cable marks  52  on the cable. In the embodiment shown in the view of FIG. 2, the cable mark sensor  50  is a optical sensor and the cable marks  52  are relatively (as compared to the color of the cable  16 ) dark bands about the cable  16 . However, it is within the scope of the sensor that essentially any means, known or yet to be developed, could be used to sense how much of the cable has been pulled past the cable mark sensor  50 . For example, the cable marks  52  could be magnetic bands and the cable mark sensor  50  could be a magnetic sensor. 
     FIG. 3 is an alternative in place polishing system  10   a , in which components are alike to and numbered the same as those of the example of FIG. 1, except for those specifically discussed herein as being different. In the alternative in place polishing system  10   a , a standard cable  16   a  is a plain, unmarked cable, such as has been used in the prior art. A standard cable puller  18   a  is a conventional cable puller such as has been used in the prior art. Although the standard cable puller  18   a  is adjustable such that it can pull the cable  16   a  at different speeds, according to one embodiment of the present inventive method which will be discussed hereinafter, it is anticipated that the cable  16   a  will be pulled at essentially the same speed through the entire pipe  28  when the alternative pipe electrochemical polishing system  10   a  is used. However, in the alternative in place polishing system  10   a , an alternative power supply  30   a  is variable such that the voltage applied to the cathode  14  can be varied. 
     Also visible in the view of FIG. 3 are an infra red camera  60 , a heat sensing crayon  62  and a plurality (three are shown) of heat sensing crayon marks  64  on the pipe  28 . A plurality (three are shown) of thermisters  66  are also shown placed on the pipe  28  in the view of FIG. 3. A plurality (three are shown) of capacitive sensors are also shown on the pipe  28  in the view of FIG.  3 . 
     As was briefly discussed hereinbefore, the practice of the present invention requires some knowledge of the present location of the cathode  14  during the polishing process. Since the cathode  14  gives off a substantial amount of heat during the electropolishing process, the infra red camera  60  can be used to detect the instant location of the cathode  14 . Similarly, the heat sensing marks  64  made by the heat sensing crayon  62  will change color when the cathode  14  is passing within the pipe  18  under the marks  64 , thereby disclosing the location of the cathode  14 . In like manner, the thermisters  66  will detect a rise in heat when the cathode  14  is passing within the pipe  28  at the location of the thermisters  66 . Also, when the cathode  14  passes through a particular location in the pipe  28 , the capacitance across the pipe will be reduced, and this can be detected by one of the capacitance sensors  68  placed at such location. 
     It should be noted that, in actual practice, more than three of the thermisters  66 , capacitance sensors  68 , heat sensing crayon marks  64 , or the like will be used. For example, each transition between a uniform portion  72  and a nonuniform portion  70  of pipe  28  would generally be delimited by one such sensor. In some applications it might also be desirable to place such a device on one or more uniform sections  72  of the pipe. If used, the infrared camera  60  could be moved, as necessary during the course of the polishing process, such that those portions of the pipe  28  wherein the cathode  14  is currently located could be seen by the infra red camera  60 . It should be noted that the practice of the present inventive method is not limited to the use of any one method for detecting the position of the cathode  14 . Any of the thermisters  66 , capacitance sensors  68 , heat sensing crayon marks  64 , or infrared camera  60 , or any combination thereof could be used to detect the current position of the cathode  14  during a single electropolishing process. Also, any of these could be used in combination with the cable marks  52  and cable mark sensor  50 , previously discussed herein in relation to FIGS. 1 and 2, or could be substituted for or used in combination with other methods and/or means for detecting the present position of the cathode  14 . 
     FIG. 4 is a flow diagram depicting relevant operations of an example of the inventive portion of the in place electropolishing method  80 . In a begin polish operation  82  voltage is applied to the cathode  14  by the power supply  30  (FIG. 1) or  30   a  (FIG.  3 ), and the cable puller  18  (FIG. 1) or cable puller  18   a  (FIG. 3) begins to pull the cathode  14  through the pipe  28  by the cathode puller cable  16  (FIG. 1) or  16   a  (FIG.  3 ). The begin polish operation  82  is conventional in nature and is not unlike such operation as applied in the prior art. 
     One skilled in the art will recognize in the diagram of FIG. 4 that a detect cathode position operation  84  begins an operational loop that is repeated during the continuation of the in place electropolishing method  80 . In a detect cathode position operation  84 , the position of the cathode  14  (FIGS. 1 and 3) is detected, such as by use of the calibrated cathode puller cable  16  having thereon cable marks  52  and the cable marks sensor as discussed in FIG.  1 . Alternatively, any other method, such as the heat detecting methods using the infra red camera  60  (FIG.  3 ), the heat sensing crayon marks  64 , the thermisters, or the like and/or any combination thereof could be used. Another alternative for accomplishing the detect cathode position operation  84  could be the use of the capacitance sensors  68  as discussed previously herein in relation to FIG. 3, or essentially any other means for detecting the position of the cathode  14 , now known or yet to be developed. 
     In an in nonuniform portion decision operation, it is determined if the cathode  14  is presently working in a nonuniform portion  70  of the pipe  28  as compared to a uniform portion  72 . If the cathode  14  is in a nonuniform portion  70  the in place electropolishing method  80  proceeds to an increased polishing operation  88 . If the cathode  14  is in a uniform portion  72  then the in place electropolishing method  80  proceeds to a decreased polishing operation  90 . In the decreased polishing operation  90  the process is much like that of the prior art. The cathode  14  is drawn through the pipe  28  at a rate of approximately three inches per minute, and the voltage applied to the cathode will be calculated according to the variables of the application according to the prior art. Alternatively, in the increased polishing operation  88  more polishing action is provided for the nonuniform portions  70  of the pipe  28 . Such increased polishing actions can be provided by slowing down the rate of progress of the cathode  14  through the pipe  28 . For example, the rate can be slowed to approximately one and one half inches per minute using the variable speed cable puller  18  (FIG.  1 ). Alternatively, the polishing action can be increased by increasing the voltage to the cathode  14  using the variable power supply  30   a  (FIG.  3 ). It is within the scope of the invention that the increased polishing operation  88  could also be accomplished by some combination of slowing the progress of the cathode  14  and increasing the voltage applied thereto. 
     Following either the increased polishing operation  88  or the decreased polishing operation  90 , in an end of pipe decision operation  92  it is determined if the cathode  14  has reached the end of the pipe  28 . If the cathode  14  has reached the end of the pipe  28 , the in place electropolishing method  80  proceeds to an end polish operation  94  wherein the pipe electrochemical polishing system  10 ,  10   a  is cleaned and shut down according to prior art methods. If it is determined in the end of pipe decision operation  92  that the end of the pipe  28  has not been reached then the decision loop returns to the detect cathode position operation  84  and the process is repeated as indicated in the flow diagram of FIG.  4 . 
     Each of the described embodiments relies on varying degrees of operator participation in the electropolishing process. It is possible, however, to more fully automate the electropolishing process of the present invention. For example, a controller  100  (FIG. 1) can be coupled to receive input from cable mark sensor  50  and to provide control signals to cable puller  18  and/or power supply  30  to implement the electropolishing processes of the present invention which are stored in a computer readable medium (not shown) of controller  100 . The operator would then only need to input the contour of pipe  28  to controller  100 . In a particular embodiment, controller  100  is a desktop or laptop computer system. 
     Various other modifications to the inventive method and apparatus are also quite possible, while remaining within the scope of the invention. For example, alternative means could be developed for determining the position of the cathode  14 . Also, alternative means for increasing the polishing action within nonuniform portions  70  of the pipe  28  could be developed. Another logical alternative would be to use the apparatus specifically disclosed herein, and/or other apparatus yet to be developed, in combinations not specifically discussed herein. 
     All of the above are only some of the examples of available embodiments of the present invention. Those skilled in the art will readily observe that numerous other modifications and alterations may be made without departing from the spirit and scope of the invention. Accordingly, the disclosure herein is not intended as limiting and the appended claims are to be interpreted as encompassing the entire scope of the invention. 
     INDUSTRIAL APPLICABILITY 
     The inventive pipe electrochemical polishing system  10 ,  10   a  and associated in place electropolishing method  80  are intended to be widely used for the in place polishing of the interior of piping systems. Since the inventive pipe electrochemical polishing system  10 ,  10   a  and associated in place electropolishing method  80  may be readily produced and integrated with existing electropolishing systems, and since the advantages as described herein are provided, it is expected that it will be readily accepted in the industry. For these and other reasons, it is expected that the utility and industrial applicability of the invention will be both significant in scope and long-lasting in duration.