Abstract:
Improved self-tightening clamp assemblies are designed for application to the adjacent ends of connected pipe sections in spanning relationship to the joint therebetween. The assemblies include a plurality of clamp bodies configured for placement about the adjacent pipe section ends and carrying a plurality of pipe-engaging teeth; a clamping mechanism is operably coupled with the clamp bodies to cause the teeth to grippingly engage the pipe section ends. The teeth are oriented so as to exert an increasing gripping force on the pipe sections ends in the event of relative separation movement between the ends.

Description:
The present invention is broadly concerned with improved clamp assemblies adapted for application to the joint between welded-together pipe sections in order to prevent full separation of the pipes. More particularly, the invention pertains to clamp assemblies of this character having self-tightening capabilities, i.e., the clamp assemblies exert an increasing gripping force on the engaged pipes in the event of relative separation movement between the pipes. 
     BACKGROUND OF THE INVENTION 
     Piping systems in refinery and other oil and gas plants make use of welded pipe sections of various sizes. Such pipe sections are subject to varying temperature and pressure conditions which can lead to failures, particularly at the welded pipe joints. One such failure mechanism is referred to as carbonate stress corrosion cracking, which is a common problem within fluid catalytic cracking units, especially in the main fractionator overhead condensing and reflux systems, the downstream wet gas compression systems, and the sour water systems emanating from the foregoing. Carbonate stress corrosion cracking results in leakage and cracking in carbon steel and low alloy steel piping weldments if appropriate post-weld heat treatment is not adequately performed. 
     When a cracking indication is detected in these systems at the weld locations, a temporary repair in the form of an external clamp is normally applied. The clamp is designed to protect the pipe against full separation while the plant is still in operation. 
     A variety of clamps have been proposed in the past for the temporary repair of refinery piping systems. U.S. Pat. Nos. 4,049,296, 4,171,142, and 4,709,729 illustrate such clamps having divided clamp bodies which can be installed around continuous piping in bridging relationship to a joint. These types of clamp are deficient, however, inasmuch as they do not provide any self-tightening feature which causes the clamp to effect a tighter gripping relationship with the pipe sections as the latter tend to separate. U.S. Pat. Nos. 4,127,289 and 4,832,379 and Published Application 2005/0052023 disclose pipe couplings having toothed pipe-engaging segments. However, these units do not include separable clamp bodies, and thus cannot be applied to continuous piping around existing joints. 
     There is accordingly a real and unresolved need in the art for improved clamp assemblies which can be installed on interconnected ends of opposed pipe sections in bridging relationship to connection joints, and which afford a self-tightening feature such that the clamp assemblies exert an increased gripping force in the event that the interconnected pipes begin to separate. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the invention to provide improved clamp assemblies and clamping methods designed for application to the joint between pipe sections, in order to provide a more effective clamping action even in the event of relative separation movement between the pipes. 
     A further object of the invention is to provide clamp assemblies and methods having self-tightening capabilities so that an increased gripping force is exerted upon clamped pipe ends in the event of separation thereof. 
     It is yet another object of the invention to provide improved clamp assemblies and methods wherein the assemblies are equipped with pipe-engaging teeth oriented against separation movement of the engaged pipes and further having mechanical advantage geometries which create increased gripping forces as a result of relative separation movement between clamped pipes. 
     One aspect of the invention concerns self-tightening clamping assemblies adapted for installation on the adjacent ends of a pair of opposed pipe sections having a joint therebetween. The clamping assembly comprises a plurality of clamp bodies configured to be placed about the adjacent pipe section ends in spanning relationship to the joint, wherein the clamp bodies have a plurality of teeth oriented for engaging both of said pipe section ends. The assemblies further include clamping mechanisms operably coupled with the clamp bodies in order to cause the teeth to grippingly engage both of the pipe section ends. The teeth are oriented relative to the adjacent gripped pipe section ends so as to exert an increasing gripping force thereon in the event of relative separation movement between the adjacent gripped pipe section ends. 
     In preferred forms, a pair of clamp bodies are utilized to cooperatively surround the adjacent pipe ends, wherein each of the clamp bodies has a plurality of segments carrying teeth members oriented for engagement of the pipe ends. The clamping mechanism advantageously includes a plurality of links surrounding the segments and pressing the teeth members into gripping engagement with the pipe ends. 
     Another aspect of the invention concerns the combination comprising a pair of opposed pipe sections having adjacent ends with a joint therebetween, together with a clamping assembly operably engaging the pipe ends in spanning relationship to the joint. The clamping assembly comprises a plurality of clamp bodies configured to be placed about the adjacent pipe section ends, wherein the clamp bodies have a plurality of teeth oriented for engaging both of the pipe section ends. The assembly further includes clamping mechanisms operably coupled with the clamp bodies in order to cause the teeth to grippingly engage both of the pipe section ends. The teeth are oriented relative to the adjacent gripped pipe section ends so as to exert an increasing gripping force thereon in the event of relative separation movement between the adjacent gripped pipe section ends. 
     A still further aspect of the invention relates to methods for preventing full separation of a pair of opposed pipe sections having a joint therebetween. The methods comprise the steps of applying a plurality of clamp bodies about adjacent pipe section ends in spanning relationship to the joint, with the clamp bodies carrying a plurality of teeth. The bodies are clamped to the pipe sections in order to cause said teeth to grippingly engage both of the pipe section ends. In the event of relative separation movement between the adjacent pipe section ends, the teeth are caused to exert an increasing gripping force on the gripped pipe section ends. Preferably, the teeth are oriented at an angle relative to the adjacent gripped portions of the pipe section ends, so as to create the desired enhanced gripping properties. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a clamp assembly in accordance with the invention, shown operatively coupled to the ends of a pair of interconnected pipe sections for preventing separation thereof. 
         FIG. 2  is an end view of the assembly depicted in  FIG. 1 . 
         FIG. 3  is a perspective exploded view of the clamp assembly of  FIG. 1 . 
         FIG. 4  is a fragmentary view illustrating one of the toothed segments forming a part of the  FIG. 1  clamp assembly. 
         FIG. 5  is a vertical sectional view taken along line  5 - 5  of  FIG. 1  and illustrating the initial clamping orientation of the clamp assembly disposed about the pipe section ends. 
         FIG. 6  is a sectional view taken along line  6 - 6  of  FIG. 1  and illustrating the fastener connection of the toothed segments. 
         FIG. 7  is a sectional view similar to that of  FIG. 6 , but illustrating the operation of the clamping assembly for preventing full separation of the interconnected pipe section ends. 
         FIG. 8  is a perspective exploded view of another clamp assembly embodiment of the invention. 
         FIG. 9  is a vertical sectional view similar to that of  FIG. 5 , but showing the  FIG. 8  clamp assembly embodiment. 
         FIG. 10  is a view similar to that of  FIG. 6 , but again showing the  FIG. 8  embodiment. 
         FIG. 11  is a perspective view of another clamp assembly of the invention, shown operatively mounted on the interconnected ends of opposed pipe sections. 
         FIG. 12  is a perspective view of one of the toothed segments carried by the  FIG. 11  clamp assembly adjacent one of the butt ends thereof. 
         FIG. 13  is a perspective view of one of the toothed segments carried by the  FIG. 11  clamp assembly adjacent the opposite butt end thereof. 
         FIG. 14  is a sectional view of the clamp assembly shown in  FIG. 11 . 
         FIG. 15  is a sectional view of part of the clamp assembly shown in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings, particularly  FIGS. 1-7 , a self-tightening clamp assembly  20  is depicted. The assembly  20  is designed for installation about the adjacent ends  22 , 24  of a pair of elongated pipe sections  26 , 28 , and specifically in bridging relationship to the weld joint  30  between the ends  22 , 24 . Broadly speaking, the assembly  20  includes a pair of clamp bodies  32 , 34  designed to cooperatively surround the ends  22 , 24 , as well as a clamping mechanism  36  operably coupled with the clamp bodies  32 , 34  in order to draw the latter into tight gripping engagement with the ends  22 , 24 . 
     In more detail, the bodies  32 , 34  are each formed of malleable metal and are substantially semi-circular in configuration and are designed for mating interconnection. Referring first to the body  32 , it will be seen that it has a central body section  38  ( FIG. 3 ) as well as side peripheral sections  40 , 42 . The central section  38  is essentially imperforate and has endmost, external flange couplers  44  with through-apertures  45 . Internally, the central section  38  has a pair of laterally spaced apart, inwardly extending walls  46 , 48  cooperatively defining a channel  50 . A single fill port  52  extends through the section  38  and communicates with channel  50 . As explained below, the opposed clamping section  34  also has a port  52 . 
     The peripheral sections  40 , 42  are each formed into eight individual segments  54  by means of seven spaced joints or cut lines  56 . Each segment  54  has a pair of spaced apart, inwardly extending walls  58 , 60  which define a recess  62  having an oblique, sloped inner wall  63 . A pair of spaced apart fastener holes  64  extend through each segment  54  and communicate with the corresponding recess  62 . As best seen in  FIG. 4 , a toothed member  66  having threaded connection bores  67  is disposed within each of the recesses  62  and is maintained therein by means of screws  68  extending through the holes  64  and into the bores  67 . The internal face of each of the members  66  presents a plurality of elongated, hardened metal teeth  70  which are slightly inclined towards joint  30  (see  FIG. 5 ) and are designed to engage and grip a corresponding pipe section end  22 , 24 . It will further be seen that the width of each member  66  is less than the distance between side walls  58 , 60 ; the significance of this feature will be described below. 
     The body  34  is substantially identical to body  32 , and accordingly like reference numerals will be applied to the parts of body  34  which correspond to those of body  32 . As best seen in  FIG. 3 , the central body section  38  is equipped with flange couplers  44 , and bolts  74  extend through the apertures  45  in order to interconnect the sections  32 , 34 ; nuts  76  and washers  78  are employed to complete the connection of the clamp bodies  32 , 34 . It will be appreciated that when the sections  32 , 34  are interconnected, the channel  50  is continuous throughout the entirety of the clamped assembly and that the segments  54  are uniformly spaced about the peripheral sections  40 , 42 . 
     The clamping mechanism  36  is made up of two circumferential, substantially identical clamps  80 , 82  which are respectively disposed about the segments  54  of the peripheral sections  40 , 42 . Thus, the clamp  80  is made up of a pair of complemental clamp halves  84  which cooperatively surround and engage the segments  54  of peripheral section  40 . Each half  84  has a pair of apertured end blocks  86  with a total of five interconnected links  88  which are secured to the blocks  86  and to each other by means of lateral pin couplers  90 . The inner faces  86   a  of the blocks  86 , and the inner faces  88   a  of the intermediate links  88 , are configured to closely conform with the outer faces of the segments  54 , i.e., each of these inner faces engages one of the segment outer faces. Interconnection of the halves  84  is effected by means of bolts  92  extending through the opposed blocks  86  and secured with nuts  94  and washers  96 . 
     The clamp  82  is identical with clamp  80 , save for the fact that the clamp  82  is disposed about the segments  54  of side section  42 . Therefore, like reference numerals are used throughout and no further description is warranted. 
     In use, the clamp bodies  32 , 34  are disposed about the pipe sections  26 , 28  in spanning relationship to joint  30 , with teeth  70  of the individual members  66  in engagement with the outer surfaces of the section ends  22 , 24 . The bodies  32 , 34  are then bolted together using the couplers  44  and bolts  74 . The clamps  80 , 82  are next secured to the peripheral sections  38 , 40 , with the inner surfaces  86   a , 88   a  in alignment with corresponding segments  54 , as best illustrated in  FIG. 2 . The clamp halves  84  are then interconnected and drawn in to tight engagement with the segments  54  by means of the bolts  92  and nuts  94 . Tightening of the bolts  94  serves to slightly deflect (either permanently or temporarily) the segments  54  inwardly so as to insure a tight gripping engagement of the teeth  70  with the outer surfaces of the pipe ends  22 , 24 . The soft steel segments  54  allow the segments to deflect and yield as necessary so that the clamp conforms to irregular pipe surfaces, e.g., the pipes may not be precisely round or flat-sided as the case may be. 
     Finally, an injectable polymer resilient fill material  98  is inserted into the continuous channel  50  so that the fill material engages and spans the joint  30 . This material preferably hardens but will retain a degree of resiliency for sealing purposes. It may be advisable to block the port  52  of one half of the clamping mechanism in order to effect a seal without a “leaking” of the injected material. Additionally, at the region where the clamp bodies  32 , 34  come together there will be a gap. It may be advisable to use a labyrinth seal or some other type of gasket to keep the injected filler material from leaking out of the clamping arrangement before it hardens. 
     It will be appreciated that the teeth  70  are driven into the pipe walls by the elastic response of the preloaded clamp arrangement. When the clamping bolts are preloaded initially, there is a stretching of the clamp elements and a consequent elastic compression the pipe sections. 
     In the event of relative separation movement between the pipe ends  22 , 24  as depicted in  FIG. 7 , the self-tightening feature of the invention comes into play. Specifically, in such an instance, the relatively large forces generated by such separation serves to shear the screws  68  holding the members  66 . At the same time, owing to the oblique orientation of the surfaces  63 , an increased gripping force is generated between the teeth  70  and the pipe ends  22 , 24 , thereby serving to minimize the separation between the pipe ends within the width of the fill material  98 . This effect is augmented owing to the elasticity of the preloaded clamp/pipe section arrangement. The small motion between the teeth and pipe does not significantly reduce the preload force. The dimensions of recess  62  are a significant factor in controlling the gap  30  ( FIG. 7 ), i.e., the amount of gripping force can be controlled by the recess dimensions, and are selected to provide enough self-tightening to grip the pipe sections but not to allow the clamping ring to become overloaded or deform the pipe sections. As such, complete failure of the pipe arrangement is avoided, thereby permitting continued operation until the separation can be permanently repaired. 
       FIGS. 8-10  illustrate a modified clamp assembly  100  which is in many respects identical with assembly  20 . Accordingly, like reference numerals will be used in the description of the assembly  100 , and only the differences between assembly  100  and assembly  20  will be particularly discussed. 
     Thus, the assembly  100  is broadly made up of clamp bodies  32   a , 34   a  which differ from the previously described bodies  32 , 34  only in the specific construction of the individual segments  54   a . In particular, these segments include inwardly directed walls  58   a , 60   a  defining recesses  62   a . The latter receive toothed members  66   a  having inwardly directed, angularly oriented hardened teeth  70   a . In this case, however, the members  66   a  are in a tight fitting relationship with the recesses  62   a . In all other respects, the bodies  32   a , 34   a  are identical with the clamp bodies of the first embodiment. Similarly, the clamping mechanism  36 , including the clamps  80 , 82 , are identical to those of the first embodiment and need not be further described. 
     The use of assembly  100  is the same as that described with reference to assembly  20 . However, upon relative separation movement between the pipe ends  22 , 24 , the assembly  24  creates an increased gripping power owing simply to the orientation of the teeth  70   a ; the mechanical advantage derived in the assembly  20  from the use of the frangible screws  68  and the oblique surfaces  63  is not present in assembly  100 . 
     A still further embodiment of the invention is illustrated in  FIGS. 11-15 , in the form of clamp assembly  102  which includes a pair of opposed clamp bodies  104 , 106  adapted to be mounted in spanning relationship to the joint  30  between pipe ends  22 , 24  of pipes  26 , 28 . Additionally, the overall assembly  102  includes a clamping mechanism  108  applied over the bodies  104 , 106 . 
     In more detail, the clamp body  104  is generally semicircular in configuration and includes a central section  110  as well as outwardly extending side sections  112 , 114 . The central section  110  has a pair of laterally spaced apart, inwardly projecting walls  116 , 118  which cooperatively defines a channel  120 . A fill port  122  communicates with the channel  120 . Each of the side sections  112 , 114  extends outwardly from the section  110  and is spaced above the inner faces of the walls  116 , 118 , thereby defining respective side recesses  124 , 126 . As best seen in  FIGS. 14 and 15 , the inner surface of each side section  112 , 114  includes a surface  128 , 130  which is substantially parallel with the underlying pipe surface, and a sloped surface  132 , 134 , and a terminal butt end surface  136 , 138 ; locating bores  139  are provided in these end surfaces as illustrated in  FIG. 11 . Thus, the sections  112 , 114  effectively define restricted throats  140 , 142  adjacent the outboard ends thereof. The outer surface of the body  104  presents a series of concavities  144  which are important for purposes to be described. 
     The opposed clamp body  106  mates with body  104  and is likewise arcuate so as to mate with the pipe ends  22 , 24 . Specifically, the section  106  is essentially a mirror image of section  104 , and accordingly like reference numerals are used throughout. As shown, the two bodies  104 , 106  cooperatively surround the ends  22 , 24  of the pipes  26 , 28 . 
     The clamping mechanism  108  includes a pair of yokes  146 , 148  having apertured, endmost connection blocks  150 , 152 . The yokes  146 , 148  are designed to overlie the respective side sections  112 , 114  as depicted in  FIG. 14 . The yokes  146 , 148  are secured in place by means of a plurality of integral, continuous U-bolts  154  which seat within the concavities  144  of body  104  and extend through the apertures of the blocks  150 , 152 . Nuts  156  are used to tighten the mechanism  108  and thus secure the bodies  104 , 106  in place. 
     The overall assembly  102  further includes a plurality of tooth members  158  secured to the side sections  112 , 114 . Referring to  FIGS. 12 and 13 , it will be seen that each of the members  158  includes an inboard gripping section  160  having lowermost pipe-gripping teeth  162 . The sections  160  also have an inclined upper surface  164  which is complemental with the surfaces  132 , 134  of the side sections  112 , 114 . In addition, each of the members  158  has a relatively thin neck section  166  which is designed to fit within restricted throats  140 , 142  previously described. Finally, each member  158  includes an upstanding flange section  168  having a pair of threaded bores respectively carrying spaced connection screws  170 . 
     The members  158  are secured to the side sections  112 , 114  by positioning the screws  170  within the bores  139 . These would be initially loosely installed on the butt ends of the sections  112 , 114 , followed by application of the latter to the pipe ends  22 , 24  using mechanism  108 . After the latter is installed over the bodies  104 , 106 , the screws  170  are used to preload the respective members  158  and create a tight gripping engagement between teeth  162  and the pipe ends. The surfaces  164  of the members  158  are thereby brought into tight complemental engagement with the surfaces  132 , 134  of the side sections  112 , 114 . 
     The final step in the attachment of assembly  102  involves filling the continuous channel  120  with resilient sealing fill material  172 . 
     The use of assembly  102  involves initial attachment thereof to the pipe ends  22 , 24  as previously described. In the event of relative separation movement between the end sections, the preloaded members  158 , because of the angularly oriented teeth  162  and the mechanical advantage gained by the mating oblique surfaces  164  and  132 , 134 , causes the gripping force exerted on the pipe end sections to be increased. This prevents catastrophic failure of the pipe assembly and permits continued use thereof until a permanent repair can be made. 
     The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.