Patent Publication Number: US-6660156-B2

Title: Pipe electropolishing apparatus using an electrolyte heater and cooler

Description:
RELATED APPLICATIONS 
     The present application is a divisional of co-pending U.S. patent application Ser. No. 09/496,478, entitled “In Pipe Electropolishing Apparatus Using an Electrolyte Heater and Cooler,” filed Feb. 2, 2000, and now U.S. Pat. No. 6,402,908, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the field of electrochemical processing, and more particularly to an improved fluid chemical system for the chemical used in the process. The predominant current usage of the present inventive improved fluid system is in the handling of chemical electrolyte used for in place electropolishing, wherein it is desirable to reduce the cumulative temperatures imparted to the fluid electrolyte due to the substantial heat created in the process. 
     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. 
     In many electrochemical processes, the temperature of the electrolyte can be readily controlled. Since a large quantity of electrolyte is used to immerse the electrode, the temperature of the electrolyte is generally stable, even though heat is introduced in the process. However, recent developments in the art have resulted in “in place” electrochemical processing. 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. However, since a significant amount of heat is generated in the process, the electrolyte tends to become overly heated as the process continues. This might not, upon first examination, seem to be a significant problem. Indeed, it is desirable that the electrolyte be heated higher than the ambient temperature. Nevertheless, the inventor has found that, as a practical matter, the electrolyte does become dramatically over heated during many such operations. 
     Therefore, it would be desirable to have some method and or means for avoiding or, at least, minimizing the undesirable effects caused by the heating of electrolyte during an electrochemical process. While increasing the quantity of electrolyte used is one possible solution, it would be desirable to have an alternative method and/or means which does not have the disadvantage of the additional bulk and additional expense associated with the use of an additional quantity of electrolyte. 
     DISCLOSURE OF INVENTION 
     Accordingly, it is an object of the present invention to provide an apparatus and method for reducing the electrolyte temperature during an electrochemical process. 
     It is still another object of the present invention to provide an apparatus and method for improving an electrochemical process. 
     It is yet another object of the present invention to provide a method and apparatus for keeping the parameters of an electrochemical process within acceptable tolerances. 
     It is still another object of the present invention to provide a method and apparatus for reducing the quantity of electrolyte needed during an electrochemical process. 
     It is yet another object of the present invention to provide a method and apparatus for reducing the time required to accomplish an electropolishing process. 
     Briefly, a known embodiment of the present invention is an improved in place electropolishing apparatus for polishing a pipe. In an electrolyte handling subsystem, a cooler is provided for cooling a fluid electrolyte as the electrolyte is recirculated through the pipe. Optionally, a temperature sensor controls the operation of the cooler. 
     An advantage of the present invention is that the temperature of the fluid electrolyte is reduced. 
     A further advantage of the present invention is that temperature dependant electrical parameters, such as resistance, can be readily kept within acceptable tolerances. 
     Yet another advantage of the present invention is that a lesser quantity of electrolyte is required, since the fluid electrolyte can be cooled and recirculated. 
     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 drawing. 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 having an electrolyte temperature control system according to the present invention; and 
     FIG. 2 is a flow diagram showing an example of a electrolyte temperature control method according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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 an essential element of the invention. 
     A known mode for carrying out the invention is an improved electrolyte handling subsystem  10  which is, in this example, as part of an in place pipe electrochemical polishing system  12 . The in place pipe electrochemical polishing system  12  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 , a dam  21 , 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. A ground wire  31  provides a good ground from the power supply  30  to the pipe  28 . During the process, the electrolyte  24  is pumped to flow through the pipe  28  in a direction  32  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 example of the inventive electrolyte handling subsystem  12 , 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 electrolyte handling subsystem  12  by the electrolyte pump  26 . A lesser or greater quantity of the filters  34  could be used, as necessary or desirable according to the application. 
     In the example of the invention shown in FIG. 1, 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  as 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 . The application and use of the chiller  46  and the heat exchanger  44  will be discussed in more detail, hereinafter. 
     FIG. 2 is a flow diagram depicting an example of the inventive electrolyte temperature control method  48 . The method  48  will be described herein with reference both to FIGS. 1 and 2. When the pipe electrochemical polishing system  10  is first activated, it is likely that the temperature of the electrolyte  24  will be out of range. One skilled in the art of electropolishing will be familiar with what amounts to an acceptable temperature range for a given application, considering the material of the pipe  28 , the type and concentration of the electrolyte  24 , the current to be provided by the power supply  30 , the speed at which the cathode  14  is to be drawn through the pipe  28  and the like. Normally, the temperature is expected to be low when the system is first turned on. In a temperature high enough decision operation  50 , the temperature indicating control  38  is used to determine if the temperature of the electrolyte  24  is sufficiently high to begin the electropolishing process. When the temperature is low, the electric heater  36  is turned on in a turn on heater operation  52  to raise the temperature of the electrolyte  24 . 
     It should be noted that each of the operations depicted in the example of FIG. 2 is accomplished repetitively as long as the electropolishing operation continues. That is, temperatures are checked, operations are performed based upon the result of such check, and then the temperature is checked again, and so on. Accordingly, when the temperature comes within range in the temperature high enough decision operation  50  the heater  36  is turned off in a turn off heater operation  54  and then current is applied to the cathode  14  and the cathode  14  is begun to be drawn through the pipe  28  in a begin/continue polishing operation  56 . 
     When, in a temperature low enough decision operation  58 , it is determined that the temperature of the electrolyte  24  is not above range the chiller  46  is left off (if already off) or turned off (if on) in a turn off/leave off chiller operation  60 . When, in the temperature low enough decision operation  58 , it is determined that the temperature of the electrolyte  24  is too high, the chiller  46  is turned on (if off) or left on (if already on) and the electrolyte  24  is cooled by the heat exchanger  44  in a turn on/leave on chiller operation  62 . 
     It should be noted that the flow diagram of FIG. 2 is not specific as to whether the operations are automatically controlled or manually initiated. In the example of the invention described, an operator initiates the operations based upon a reading of the temperature indicating controller  38 , although it is anticipated by the inventor that the operations could be placed entirely under computer control or otherwise automated. 
     Various modifications to the inventive method are also quite possible, while remaining within the scope of the invention. For example, while no provision is made in the example of FIG. 2 for shutting down the entire procedure should the temperature become exceedingly high, one skilled in the art will recognize that it would be a simple matter to cause the temperature indicating controller  38  to shut down the electropolishing process should the temperature reach some predetermined level higher than that temperature at which the chiller  46  is initially turned on. 
     It should be noted, as one skilled in the art will recognize, that the electrolyte  24  is an acid and, therefore, all components which come into contact with the electrolyte  24  should be selected to be capable of withstanding the acid. Furthermore, users of the invention should take the appropriate and necessary precautions for handling the electrolyte  24 . 
     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 electrolyte handling subsystem  12  is intended to be widely used in electrochemical processing systems. While the invention could be adapted for use with many types of such systems, it is intended initially for use with in place systems, wherein the electrolyte  24  is recirculated. In such systems it has been found that the electrolyte is further heated each time that it passes through the active area wherein the cathode  14  is electrically interacting with the anode (the pipe  28 , in this example). 
     Since the inventive electrolyte handling subsystem  12  of the present invention may be readily produced and integrated with existing electropolishing and electroplating devices, 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.