Abstract:
An apparatus and method for protecting a structure from corrosion, according to which the apparatus includes two pivotally connected members, at least one anode device connected to at least one of the members, and a resilient component engaged with the members.

Description:
BACKGROUND  
       [0001]     This invention relates, in general, to the corrosion protection of a structure that is exposed to wet, gaseous and/or below-ground environments wherein either water or a thin film of condensed moisture covers at least a portion of the structure. In these types of environments, an electrochemical process, often referred to as corrosion, can destroy the material of the structure.  
         [0002]     While undergoing corrosion, the structure has two areas, an anodic site (or anode) where the corrosion occurs and from which electrons flow, and a cathodic site (or cathode) to which the electrons flow. Sacrificial anode devices have been used to prevent the corrosion. A sacrificial anode device includes one or more anodes from which electrons flow into the structure, thereby intentionally corroding the anodes while lowering the potential of the structure to such a value that no anodic sites form, that is, no corrosion occurs. The sacrificial anode device is usually replaced as its anodes near destruction.  
         [0003]     The installation or replacement of a typical sacrificial anode device is usually costly and time-intensive, and sometimes requires the interruption of the operation of the system of which the structure to be protected is a part. For example, the replacement of a sacrificial anode device connected to an underwater flexible pipe usually requires raising the flexible pipe out of the water.  
         [0004]     Therefore, what is needed is a sacrificial anode device that may be quickly and easily installed or replaced in situ, without moving the structure to be protected or interfering with its normal operation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is an perspective view of an anode protection clamp installed onto a cylindrical structure.  
         [0006]      FIG. 2A  is a side view of the clamp of  FIG. 1 , the clamp including a generally U-shaped center bar  32  and a plurality of bars  20 .  
         [0007]      FIG. 2B  is a view similar to that of  FIG. 2A  but depicting a plurality of anodes connected to the clamp.  
         [0008]      FIG. 3  is an end view taken along the line  3 - 3  of  FIG. 2B , but with the end portions of the generally U-shaped center bar  32  removed for clarity.  
         [0009]      FIG. 4  is a sectional view taken along the line  4 - 4  of  FIG. 2B , but with an end portion of the generally U-shaped center bar  32  removed for clarity.  
         [0010]      FIG. 5  is a sectional view taken along the line  5 - 5  of  FIG. 3 , but with the bars  20  removed for clarity.  
         [0011]      FIG. 6  is an elevation view of a stem of the clamp of  FIG. 1 .  
         [0012]      FIG. 7  is a view similar to that of  FIG. 3  but depicting the clamp extending over a cylindrical structure to be protected.  
         [0013]      FIG. 8  is a view similar to that of  FIG. 7  but depicting the clamp in an intermediate position relative to the structure.  
         [0014]      FIG. 9  is a view similar to that of  FIG. 4  but depicting the clamp extending over the structure.  
         [0015]      FIG. 10  is a view similar to that of  FIG. 9  but depicting the clamp in its final position during operation.  
         [0016]      FIG. 11  is a view similar to that of  FIG. 3  but depicting inserts connected to the clamp.  
     
    
     DETAILED DESCRIPTION  
       [0017]     Referring to  FIGS. 1-3 , an anode protection clamp according to an embodiment is generally referred to by reference numeral  10  which is designed to be mounted on a cylindrical structure  12 , which can be in the form of a metal pipe, or the like.  
         [0018]     The clamp  10  includes three pairs of spaced arcuate arms  14 ,  16  and  18  with the arms  18  extending between the arms  14  and  16 . (Only one arm of each pair is shown in  FIGS. 2A and 2B  and only one pair of arms  14  is shown in  FIG. 3 .)  
         [0019]     As shown in  FIG. 3 , each arm  14  includes a curved arcuate portion and a straight portion extending from the arcuate portion. The arrangement is such that the opposed arcuate portions of each pair of arms  14  from a partial circle that envelopes a portion of the structure in the clamping position of the clamp  10 , and the straight portions extend in a spaced, parallel relation. The arms  16  and  18  are identical to the arms  14 . Two bars  20  run along the entire length of the clamp  10  and are connected to each of the arms  14 ,  16 , and  18  on each side of the clamp.  
         [0020]     Three anodes  22  are mounted between each outer arm  14  and  16  and its corresponding middle arm  18 , resulting in six anodes per side of the clamp  10  and a total of twelve anodes for the entire clamp. The anodes  22  are welded to the arms  14 ,  16  and  18  and are composed of an alloy material such as an aluminum alloy. The anodes  22  have been omitted from  FIG. 2A  in the interest of clarity.  
         [0021]     As better shown in  FIG. 2A , each outer arm  14  and  16  includes a padeye  24  mounted on the straight portion of each arm and extending away from the center of the clamp  10 .  
         [0022]     A generally elliptical-shaped frame  30  ( FIG. 3 ) is provided and a generally U-shaped center bar  32  is connected, at its ends, to the frame. The respective ends of two spaced bars  34  are connected between one side of the frame  30  and the bar  32 , and the ends of two additional spaced bars  36  are connected between the other side of the frame  30  and the base of the bar  32 , and opposite the bars  34 .  
         [0023]     Two vertical bars  40  ( FIG. 2A ) extend downwardly from the bar  32  as viewed in the drawing, to the structure  12  when the clamp  10  is in its clamping position, as will be described.  
         [0024]     Three laterally-spaced locking elements or stems  44  are threadably engaged through corresponding threaded openings formed in the base of the center bar  32 . The stems  44  will be described in detail later.  
         [0025]     As shown in  FIG. 3 , a pin  46  extends between the padeyes  24  with its ends being connected to the padeyes, and an elastomer spring  48  extends around the pin  46 . It is understood that an identical spring and pin are also associated with the arms  16 .  
         [0026]     The arms  14 ,  16 , and  18  have inner surfaces  54  and it is understood that a portion of the surfaces  54  may be grooved (not shown). The grooves on the surfaces  54  may begin, for example, at about the axis x-x (as shown in  FIG. 3 ) and continue to the bars  20  at the bottom ends of the arms  14 ,  16 , and  18 .  
         [0027]     Referring to  FIGS. 4 and 5 , two eyelets  56  extend from the vertical portions of the arms  14 ,  16 , and  18 , and towards the corresponding arm on the other side of the clamp  10 . The eyelets of each arm  14 ,  16 , and  18  of each pair of arms overlap so that their respective openings are aligned. A shaft  58  extends through the aligned openings in the eyelets  56  as well as through openings extending through the bars  40 , and a plate  59  connects the two bottom surfaces of the two eyelets  56  on each arm  14 ,  16 , and  18 , for reasons to be described.  
         [0028]     A pin  60  is disposed through each pair of corresponding eyelets  56  of the arms  14  and  16  positioned towards the outside ends of the clamp  10  so that the latter arms  14  and  16  are able to rotate about the pins  60  with the degree of rotation being limited by the elastomer springs  48  ( FIG. 3 ).  
         [0029]     Each arm  14 ,  16 , and  18  also includes an inwardly directed wedge member  62  positioned on the inner surface of its straight portion for reasons that will be described.  
         [0030]     The three stems  44  mentioned above are associated with the three pairs of arms  14 ,  16 , and  18 , respectively, and the details of each stem  44  are shown in  FIG. 6 . Each stem  44  includes a cross handle  64  disposed at one end of a shaft  68  that extends for the length of the stem. A sleeve  70  extends around the upper end portion of the shaft  68 , and a portion  68   a  of the shaft extending adjacent the sleeve is externally threaded. A pair of spaced elastomer springs  74  and  76  extend around the shaft  68  to either end of a conical stop  78 , and a pair of washers  80  and  82  also extend around the shaft  68  and are disposed at the respectively outer ends of the springs. A pin  86  extends through the lower portion of the stem  44 , as viewed in  FIG. 6 , and a washer  88  rests on the upper surface of the pin. An opening  68   b  is formed in the lower portion of the shaft  68  below the pin  86 . The specific function of the above components of the stem  44  will be described in detail.  
         [0031]     As shown in  FIGS. 3 and 4 , the threaded portion  68   a  of the shaft  68  is in threaded engagement with an internally threaded opening extending through the base of the bar  32 , and the conical stop  78  is in a camming engagement with the wedge members  62  of the arms  14 ,  16 , and  18 . Thus, when manually rotated by the handle  64  the stem  44  is able to move vertically up or down relative to the arms  14 ,  16 , and  18  and the frame  30  causing the stop  78  to move relative to the members  62 , resulting in corresponding movement of the arms  14 ,  16 , and  18 , under conditions to be described.  
         [0032]     The operation of the above embodiment will be described, for the purpose of example, under the assumption that the cylindrical structure  12  is an end fitting of an underwater pipeline resting on the sea bottom. It is understood that the installation and removal procedures to be described may be performed by either a human diver, a remotely operated vehicle or the like, or a combination thereof. As shown in  FIG. 7 , the clamp  10  is positioned directly above the structure  12 , with the distal ends of the arms  14 ,  16 , and  18  touching the upper portion of the structure  12 . In this position, the elastomer springs  48  maintain the clamp  10  in its normal, at rest, position.  
         [0033]     The clamp  10  is then pushed downwardly, as viewed in  FIG. 7 , towards the horizontal surface (or the sea bottom) which forces the arms  14 ,  16 , and  18  open due to the camming action provided by the cylinder surface of the structure  12 . The arms  14 ,  16 , and  18  thus rotate about the shaft  58  and the pins  60  radially outwardly against the resistance provided by the elastomer springs  48  and cause a corresponding compression of the springs.  
         [0034]     As the clamp  10  is pushed further downwardly relative to the structure  12 , the arms  14 ,  16 , and  18  continue to open as shown in  FIG. 8 , with the distance between the ends of the arms reaching a maximum when the tangential points of the arcs located at the bottom of the arms touch the opposing tangential points of the cylindrical structure  12 .  
         [0035]     Further downward pushing of the clamp  10  relative to the structure  12  continues until the bars  40  contact the cylindrical structure  12  and the clamp takes the position of  FIG. 9 . In this position, the arms  14 ,  16 , and  18  close around the structure  12  due to the forces exerted by the elastomer springs  48  as they move from their compressed state to their normal, relaxed state. Also, in this position, the lower end of the shaft  68  of each stem  44  is spaced from the upper surface of the structure  12  a distance referred to by the reference letter X in  FIG. 9 .  
         [0036]     Referring to  FIG. 10 , the handles  64  of the stems  44  are then manually rotated to lower the stems  44  relative to the structure due to the threaded engagement of the threaded portion  68   a  of the stems with the internally threaded bar  32 . As the stems  44  move downwardly in this manner, the conical stops  78  of the stems slide along the cam surfaces of the wedges  62 , thus pivoting the straight portions of the arms  14 ,  16 , and  18  radially outwardly and the arcuate portions radially inwardly about the shafts  58  and the pins  60  to increase the clamping force on the cylindrical structure  12 . This continues until the lower ends of the shafts  68  contact the top of the cylindrical structure  12 , and the clamp is in its “locked” in position. In this position the washer  82  of each stem engages the top surfaces of the eyelets  56 , and the elastomer spring  76  of each stem  44  is compressed between its corresponding conical stop  78  and washer  82 , and the elastomer spring  74  of each stem is compressed between its corresponding conical stop  78  and washer  80 . It is understood that the aforementioned grooves of the inner surfaces  54  of the arms  14 ,  16 , and  18  may promote adhesion to the cylindrical structure  12 .  
         [0037]     Once in its final position, the clamp  10  is electrically connected with the cylindrical structure  12  due to the intimate contact between the inner surfaces of the arcuate arms  14 ,  16 , and  18 , the lower end of the shaft  68 , and the ends of the bars  40  with the corresponding outer surfaces of the structure. Thus the anodes  22  can function in a sacrificial mode to protect the structure from corrosion.  
         [0038]     In particular, as corrosion begins to take place on the surfaces of the anodes  22  over time, electrons flow from the anodes  22  to the arms  14 ,  16 , and  18  via the weld joints, and then into the cylindrical structure  12  via the inner surfaces of the arms, by the ends of the shafts  68  of the stems  44 , and by the bars  40 . It is understood that there may be other electron flow paths from the anodes  22  to the cylindrical structure  12 . The cylindrical structure  12  serves as a cathode, with the electrons moving to the surfaces of the structure to combine with oxygen and water molecules in the water. Meanwhile, the positively-charged metal ions on the surfaces of the anodes  22  (produced as a result of the electron flow) discharge into the water, resulting in a partial destruction of the anode  22  surfaces (corrosion). This process continues until all of the anode  22  material is destroyed or nearly destroyed.  
         [0039]     The clamp is removed from the cylindrical structure  12  by first manually unscrewing the stems  44 . During this upward movement of the stems  44 , the conical stops  78  also move upward and out from between the wedges  62  of the arms  14 ,  16 , and  18 , thus “unlocking” the arms. The stems  44  are prevented from being completely removed from the clamp  10  by the washers  88  contacting the plates  59  during this upward movement. After the arms  14 ,  16 , and  18  have been unlocked, a diver or a remotely operated vehicle can lift the clamp  10  upwardly in a direction away from the cylindrical structure  12 , resulting in the arcuate portions of the arms  14 ,  16 , and  18  rotating away from and unclamping the cylindrical structure  12 . Thus, the cylinder structure  12  is unaffected by the above corrosion.  
         [0040]     Referring to  FIGS. 2B and 3 , three electrical cables  90   a ,  90   b , and  90   c  are provided that promote the flow of electrons from the anodes  22  to the cylindrical structure  12 . The cable  90  connects the padeye  24  associated with the arms  16  to the corresponding stem  44 , the cable  90   b  connects the latter padeye with the stem corresponding to the arms  18 , and the cable  90   c  connects the padeye associated with the arms  14  to the corresponding stem  44 . Each cable  90   a ,  90   b , and  90   c  is connected to its corresponding stem  44  via the opening  68   b  ( FIG. 6 ) formed in the shaft  68  of each stem. Thus, electrons may flow from the arms  14 ,  16 , and  18  to the stems  44  via the electrical cables  112 . It is emphasized that the use of the cables  90   a ,  90   b , and  90   c  is not necessarily required to utilize the anodes  22  to prevent corrosion to the structure  12 , but simply further promotes the electron flow in the above manner.  
         [0041]     Referring to  FIG. 11 , a pair of inserts  92  are connected to each pair of arms  14 ,  16  and  18 . The inserts  92  are shaped to conform to the inside surfaces  54  of the arms  14 ,  16 , and  18  and to enable the clamp  10  to be used with a cylindrical structure having an outer diameter that is smaller than the outer diameter of the cylindrical structure  12 . It is understood that the inserts  92  may be welded or fastened to the arms  14 ,  16 , and  18  in any conventional manner so that the clamp  10  is electrically connected to the smaller cylindrical structure due to the contact between the inserts and the smaller cylindrical structure. It is further understood that inner surfaces  94  of the inserts  92  may be grooved to promote adhesion to the smaller cylindrical structure. Also, multiple sets of inserts  92  may be provided, with each set of inserts accommodating a different outer diameter. Moreover, instead of employing the inserts  92  to accommodate a cylindrical structure having a smaller outer diameter, it is understood that the clamp  10  and/or the arms  14 ,  16 , and  18  could be modified accordingly to accommodate the smaller outer diameter.  
       Variations  
       [0042]     It is understood that several variations may be made in the foregoing without departing from the scope of the invention. For example, the clamp  10  is not limited to the particular exemplary application discussed above but rather is also well suited for other off-shore and on-shore applications in wet (such as underwater), gaseous (such as air), and below-ground environments. Further, the clamp  10  may be installed onto non-cylindrical structures, such as structures having rectangular cross-sections, and the shapes of the arms  14 ,  16 , and  18  and the inserts  92  may be modified accordingly to conform to the non-cylindrical structures.  
         [0043]     Still further, the number of pairs of arms  14 ,  16 , or  18  may be varied from one to an unlimited number. Also, other alloys, such as zinc or magnesium, may be used for the anodes  22 . Moreover, the quantity of the anodes  22  in the clamp  10  may be varied from one to an unlimited number, and the anodes may be connected to the arms  14 ,  16  and  18  with bolts and/or other types of fastening systems in addition to or instead of weld joints. Also, other types of resilient components such as, for example, a helical spring, could be substituted for the elastomer spring  48 .  
         [0044]     Although only one exemplary embodiment of this invention has been described in detail above, those skilled in the art will readily appreciate that many other modifications are possible in the exemplary embodiment without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.