Abstract:
A method and apparatus for separating or spreading flanges of pipes is disclosed and includes two bolt hole engaging devices and a force transmission system. The force transmission system selectively couples with a bolt hole engaging device and is capable of exerting a force thereon for selective movement of the flanges relative to one another. The bolt hole engaging device comprises an expandable member that is arranged to be at least partially accommodated within the bolt hole before expansion, and an expander means arranged to expand the expandable member such that at least a portion of an outer surface of the expandable member is expanded to contact the bolt hole. The expander means may include at least one wedge shaped member and an actuator means for causing relative movement between the wedge shaped member and the expandable member.

Description:
RELATED APPLICATION 
     This Application is the U.S. National Phase Application of PCT International Application No PCT/GB2006/002473 filed Jul. 3, 2006. 
     FIELD OF THE INVENTION 
     This invention relates to apparatus and method for spreading flanges of pipes. 
     DESCRIPTION OF THE RELATED ART 
     Large diameter pipes are typically formed from a series of shorter pipe portions placed end to end. The portions of pipe are joined by bolting adjacent flanges that extend radially from the end of pipes to be joined. Bolts are inserted through holes in the flanges and typically a gasket is inserted between adjacent flanges before the bolts are used to draw the two flanges towards one another and create a substantially fluid-tight join. Gaskets occasionally require inspection or replacement and therefore there is an occasional need to access the area between adjacent flanges. 
     BRIEF SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided apparatus for spreading flanges of pipes comprising:
         one or more bolt hole engaging devices and a force transmission system arranged for selective coupling with the or each bolt hole engaging device and capable of exerting a force thereon for selective movement of the flanges relative to one another,   wherein the bolt hole engaging device comprises an expandable member arranged to be at least partially accommodated within the bolt hole before expansion and an expander means arranged to expand the expandable member such that at least a portion of an outer surface of the expandable member is expanded to contact the bolt hole.       

     The expandable member can be retained within a bolt hole by friction between the inner surface of the bolt hole and the outer surface of the expandable member, following expansion thereof within the bolt hole. The expandable member can optionally be provided with one or more friction-enhancing enhancing formations such as ridges extending radially outwardly, or other radial protrusions. The formations, ridges or other radial protrusions can be axially spaced along the outer surface of the expandable member, so that they are expanded into contact with the inner surface of the bolt hole at locations that are spaced along the axis of the bolt hole. 
     The expandable member typically has an inner bore to accommodate the expander device. 
     The expandable member can optionally comprise one or more tapered portions that can move relative to other portions of the member to radially expand the outer surface. The tapered and other portions moving relative to one another typically engage one another by means of bearing surfaces disposed between them. The bearing surfaces can be substantially planar or curved, and in most cases, the outer surface can be curved to match the inner surface of the bolt hole, which it engages. 
     The expandable member can comprise a generally cylindrical member having one or more slits extending through a sidewall thereof. The slits are typically parallel to one another and to the axis of the member. The slits are typically circumferentially spaced around the expandable member, and circumferentially adjacent slits typically extend from alternate ends of the member, so that the member can be expanded into a “zig-zag” configuration, with the elongate axial portions between the slits being interconnected at alternate ends of the member. 
     Preferably, one bolt hole engaging device can be used with several sizes of expandable members in order to engage different sizes of bolt holes. The different expandable members can typically have the same inner diameter and different outer diameters. Thus the bolt hole engaging device is adaptable and there is no requirement to have an entire device suitable for each particular bolt hole diameter. 
     The outer surface of the expandable member can typically be harder than the inner surface of the bolt hole. The expandable member can typically be made from mild steel which has been surface hardened. 
     The expander means can be arranged to exert a force on the expandable member to move the expandable member radially outwardly. 
     The expander means can comprise one or more frustoconical members and an actuator means to move the frustoconical member(s) relative to the expandable member. The frustoconical member can be arranged such that relative movement between frustoconical member and the expandable member causes the expandable member to expand. The angle of inclination of the tapered face of the frustoconical member(s) relative to the central axis thereof can be varied in order to adjust the amount of axial travel of the expander means or expandable member relative to the radial expansion of the expandable member. The frustoconical member can optionally have a substantially polygonal cross section. 
     The actuator means is provided to initiate relative movement of the frustoconical member and the expandable member. The actuator means can comprise a screw-threaded device. In some embodiments, the actuator means can act on the expandable member to urge it towards the larger diameter end of the frustoconical member. In other embodiments, it acts on the frustoconical member to move the frustoconical member relative to the expandable member, so that it moves farther into the bore of the expandable member, and radially expands the expandable member. Accordingly, a thread on one portion of the device and a nut having a corresponding thread can be driven relative to one another as an actuator means such the expandable member moves axially relative to the frustoconical member, and expands radially. The nut can have a collar which collar can be arranged to engage an end face of the expandable member. 
     The force transmission system can be coupled directly to the bolt hole engaging device. One bolt hole engaging device can be provided on each adjacent flange, in aligned bolt holes. The force transmission system can comprise two arms each connectable to a respective bolt hole engaging device at one end and to a driving mechanism at the other end. The driving mechanism can be a screw-threaded device that is capable of exerting an axial force to separate the two bolt hole engaging devices that are attached to the flanges, and thus to separate the flanges themselves. According to another embodiment of the invention the driving mechanism can comprise a hydraulic ram. 
     The force transmission system can be provided with a spacer bar connectable between pivot points on the arms. The length of the spacer bar can be adjustable to suit the distance between the flanges, and can be locked in a number of positions once the desired length has been determined. 
     The position of the pivot point on the arms can optionally be varied in order to change the lever ratio of the arms, and thereby modulate the amount of force applied to the bolt hole engaging device. 
     The force transmission system can be adjustable. The length of the spacer bar and the length of the driving mechanism can be adjustable to enable use of the force transmission system on a range of flange widths. 
     In certain embodiments, the force transmission system can be hydraulically operated. The bolt hole engaging device can have an axial bore to house a piston and form a hydraulic piston chamber for fluid to drive the piston relative to the device. The piston can be coupled to a driving pin that is coaxial with and retractable within the bore of the bolt hole engaging device. The driving pin can be driven out of the piston chamber by the force of the hydraulic fluid, out of the end face of the flange, and forced against the driving pin on the device located in the aligned bolt hole of the adjacent flange, or against another reaction surface. The driving pin can be provided with a protrusion or a recess on the end face that can be engaged with a recess or protrusion on the end face of the adjacent driving pin. This ensures that the driving pins are correctly aligned with respect to one another, and that the force exerted is perpendicular to the radial direction of the flanges. The protrusion and recess can be in the form of a ball and socket. The protrusion and recess can engage to prevent misalignment and shearing of adjacent driving pins. 
     According to a second aspect of the present invention there is provided a method for spreading flanges of pipes comprising the steps of:
         providing a bolt hole engaging device comprising an expandable member;   arranging the expandable member at least partially within a bolt hole on a flange;   actuating an expander means to expand an outer surface of the expandable member into contact with the bolt hole;   providing a force transmission system to act on the bolt hole engaging device; and   actuating the force transmission system to exert a force on the bolt hole engaging device tending to move the flanges relative to one another.       

     The steps of the method can be repeated so that another bolt hole engaging device is positioned in the aligned bolt hole of the adjacent flange. The method steps can be repeated further so that an additional two devices can be positioned in aligned bolt holes separated by 180° around the flange. If required, several devices can be arranged in corresponding bolt holes around the flange. 
     The method can also include the step of providing a frustoconical expander means and driving the frustoconical expander means and the expandable member relative to one another, in order to expand the expandable member. This can be achieved by turning a nut on a screw thread, which nut can act on the frustoconical expander means to push it into the expandable member. Alternatively, the nut can act on the expandable member to move it relative to the expander means. The method can include calculating or measuring the force required to pull the bolt hole engaging device out of the bolt hole. This can be achieved by recording the number of turns of the nut along the screw thread, or by a torque-measuring tool used to apply a predetermined torque to the nut. 
     The or each expandable member can be provided with slits extending through a sidewall thereof. The method can include the step of increasing the friction between the expandable member and bolt hole by increasing the amount of surface area of the expandable member in contact with the bolt hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Several embodiments of the present invention will now be described with reference to and as shown in the accompanying drawings, in which:— 
         FIG. 1  is a sectional side exploded view of a bolt hole engaging device in accordance with one embodiment of the present invention; 
         FIG. 2   a  to  2   c  are sectional side views showing the device of  FIG. 1  in progressive stages of assembly; 
         FIG. 3  is a sectional side view of the assembled device of  FIG. 1 ; 
         FIG. 4   a  is a side view of two adjacent devices of  FIG. 3 ; 
         FIG. 4   b  is a side view of the devices of  FIG. 4   a  with an expanded collet; 
         FIGS. 5   a  to  5   e  are sectional views showing progressive stages of insertion of the device of  FIG. 3  into empty aligned bolt holes to achieve separation of flanges; 
         FIGS. 6   a  to  6   e  are side views of progressive stages of assembly of a bolt hole engaging device according to another embodiment of the present invention; 
         FIG. 7   a  is a side view of the device shown in  FIG. 6   e;    
         FIG. 7   b  is a side view of the device of  FIG. 7   a  with the collet partially expanded; 
         FIGS. 8   a  to  8   c  are sectional views of progressive stages of insertion of the device shown in  FIG. 6   e  into empty aligned bolt holes; 
         FIGS. 9   a  and  9   d  are sectional side views showing the progressive stages of coupling a force transmission system to the bolt hole engaging device and separating adjacent flanges; 
         FIG. 10   a  is a side view of a force transmission system attached to the bolt hole engaging device of  FIG. 7   a;    
         FIG. 10   b  is a side view of the force transmission system of  FIG. 10   a  after a force has been applied to the bolt hole engaging device; 
         FIG. 11  is a perspective view of an unexpanded collet; 
         FIG. 12  is an exploded perspective view of another embodiment of part of a bolt hole engaging device in accordance with the present invention; and 
         FIG. 13  is an exploded perspective view of an alternative embodiment of a bolt hole engaging device according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to one embodiment of the present invention, component parts of a bolt hole engaging device, indicated generally at  20 , are shown in an exploded view in  FIG. 1 . The bolt hole engaging device  20  comprises a body portion  38  that forms part of an expander means, a collet  40 , which acts as an expandable member, a nut  54  and an end cap  64 . 
     The body portion  38  includes a first end portion  22  and a second end portion  26  with a frustoconical portion  24  therebetween. The large diameter end of the frustoconical portion  24  is contiguous with the first end portion  22  and the small diameter end of the frustoconical portion  24  is contiguous with the second end portion  26 . 
     The first end portion  22  houses a hydraulic system. The hydraulic system includes an open-ended chamber  84  in which a piston  86  is sealed. The piston  86  is moveable within the chamber  84  to drive corresponding movement of a driving pin  36  protruding from the open end of the chamber  84 . The second end portion  26  is provided with a screw thread  28  on its outer surface. The frustoconical portion  24  and the second end portion  26  have a continuous bore  32  extending therethrough to allow hydraulic fluid to be transmitted from an external supply to the chamber  84 . The bore  32  within the second end portion  26  has an enlarged portion  33 , the inner surface of which is provided with a thread  34 . 
     The collet  40  has a substantially cylindrical outer shape and is made up from four separate segments  42 . Each segment  42  has a number of mutually parallel circumferential ridges  44  protruding radially from its outer surface and a lip  46  extending radially outwardly from one end. An inner surface  48  of the collet  40  is substantially frustoconical in shape and the profile of the inner surface matches a portion of the outer surface of the small diameter end of the frustoconical portion  24 . 
     The nut  54  is provided with a collar  58  attached thereto and has an inner thread  56  matching the thread  28  on the second end portion  26 . The end cap  64  bears a hydraulic connector, and is also provided with a thread  66  that matches the thread  34 . 
       FIGS. 2   a  to  2   c  show the bolthole engaging device  20  in various stages of assembly. As shown in  FIG. 2   b , the collet  40  fits over the second end portion  26 . The taper on the conical inner surface  48  of the collet  40  matches the taper on the outer face  24   f  of the frustoconical portion  24 , so that the two surfaces  48 ,  24   f  can bear against one another so that the collet  40  is fully supported by the portion  24 . The nut  54  can then be assembled over the second end portion  26  and the threads  56  and  28  engaged. When the nut  54  is at the position shown in  FIG. 2   c , close to the open end of the thread  28 , the collar  58  is pressed lightly against the lip  46  of the collet  40 , the faces  24   f  and  48  are lightly pressed against one another, and the collet  40  is unexpanded. In the final stage of assembly, the end cap  64  is fixed to the body portion  38  by engaging the threads  66  and  34  at the enlarged portion  33  at the end of the bore  32 .  FIG. 3  shows the assembled bolt hole engaging device  20 . 
       FIG. 4   a  shows two adjacent bolt hole engaging devices  20  facing one another in the position in which they would be located when assembled (but not expanded) within aligned bolt holes in adjacent flanges. When the devices are in place, the lips  46  of the collets  40  are pressed against the outer surfaces of the flanges, and the unexpanded collets  40  would be located within the bolt holes. When the collet  40  is to be expanded, the nut  54  is driven along the thread  28  relative to the collet  40 . The collet  40  is of course held stationary relative to the flange by the lip  46  being pressed hard against the outer surface of the flange. As the nut  54  moves along the thread  28 , the collar  58  reacts against the lip  46  of the stationary collet  40  and pulls the frustoconical portion  24  through the bore of the collet  40 . The tapered surfaces  24   f  and  48  slide against one another, and the relative axial movement is translated into radial separation of the collet segments  42 . The nut  45  is driven in this manner until the collet expands to the desired extent to lock the device  20  within the bolt hole. 
       FIGS. 5   a  to  5   e  show the steps involved in engaging bolt holes in order to separate two adjacent flanges  70 . Portions of pipeline  76  are provided with flanges  70  extending radially therefrom at each end. Adjacent flanges  70  are joined by bolts (not shown) positioned in bolt holes  72  on each flange. There is a small initial gap  74  between adjacent flanges  70 . A gasket (not shown) is usually positioned in the gap  74  between adjacent flanges  70 , normally radially inside the bolt holes  72 . 
     The first step in the method of separating the flanges  70  is to position a bolt hole engaging device  20  within each bolt hole  72 . Once the bolt hole engaging devices  20  are located within the bolt holes  72 , the collets  40  may then be expanded as shown in  FIGS. 5   c  and  5   d  by driving the nut  56  along the thread  28 . This drives the outer surface of segments  42  radially outwards against the inner surfaces of the bolt holes  72 , and relative movement between the bolt holes  72  and the collets  40  is restrained by friction due to the expanded surface area of the collet  40  and formations  44  on the outer surface thereof gripping the inner surface of the bolt hole  72 , adopting the configuration shown in  FIG. 5   d.    
     In order to separate the flanges  70 , a supply of hydraulic fluid under pressure (not shown) is attached to the end cap  64  and hydraulic fluid is pumped down the bore  32  and into the chamber  84 . The hydraulic fluid within the chamber  84  acts on the seals of the piston  86  to move the piston  86  out of the chamber, and to push mating faces  37  of the driving pins  36  into contact with one another. The opposing forces push the mating faces  37  of the driving pins  36  apart, and widen the gap  74  between the flanges  70  as shown in  FIG. 5   e.    
     As the nut  56  is turned along the thread  28 , the precise number of revolutions of the nut  56  can be measured. Since the collet typically behaves in a predictable way and expands in a consistent manner, the measured number of revolutions can be used to calculate the pull-out force of the bolt hole engaging device  20 . The calculated pull-out force of the bolt hole engaging device  20  can be adjusted to exceed the force applied by the hydraulic pressure to each driving pin  36 , so that the hydraulic pressure acting to separate the flanges  70  does not pull the devices  20  out of the bolt holes  72 . Alternatively, the torque on the nut  54  can be measured by a conventional torque wrench, and the desired pull out force can be calculated from that indication. 
     The lip  46  provides a surface against which the collar  58  provided on the nut  54  can react. Furthermore; the lip  46  is generally radially wider than the bolt hole  72 . Therefore, the lip  46  optionally acts as an indicator to the user of the bolt hole engaging device  20 , to limit the depth of insertion of the collet into the bolt hole and maintain the required distance into the bolt hole  72 . However, the lip  46  is an optional feature, and it can be omitted, with the collet being able to penetrate entirely into the bolt hole and be expanded at any desired axial position therein. 
     According to another embodiment of the invention shown in  FIGS. 6 to 11 , an alternative bolt hole engaging device is shown generally at  90 . The device  90  comprises a body portion  92 , a nut  110 , a washer  112 , a first frustoconical member  114 , a collet  100  and a second frustoconical member  116 . 
     The body portion  92  comprises a pin  94  having a head  96  at one end and an external thread  124  provided therebetween. At the other end of the pin  94 , a thread  126  is provided. The head  96  has two cylindrical protrusions  98  extending laterally from opposing sides thereof. 
     The nut  110  has an internal thread  108  that cooperates with the external thread  124  on the body portion  92 . 
     The first frustoconical member  114  is provided with a throughbore  115 , which is of a diameter sufficient to accommodate the pin  94 . The second frustoconical portion  116  is similar to the first frustoconical position  114  and has a throughbore  117 . The inner surface of the throughbore  117  is provided with a thread  118 . At the larger diameter end of the second frustoconical portion  116 , an end stop  120  is provided to prevent the pin  94  from protruding beyond the second frustoconical portion  116 . 
     A detailed perspective view of the collet  100  is shown in  FIG. 11 . The collet  100  has a throughbore  106  and is provided with axial slits  102  extending from one end towards the other end of the collet  100 . Each slit  102  is blind-ended, and extends from one end of the collet  100  to a position just short of the other end. The slits  102  are arranged at 45° intervals around the circumference of the collet  100 , and adjacent slits extend from alternate ends of the collet  100 . The end portions of the collet  100  are provided with radial protrusions  104  on the outer surface. 
     Assembly of the bolt hole engaging device  90  is shown from  FIGS. 6   a  to  6   e . The nut  110  is inserted over the pin  94  and the thread  108  engages with the corresponding thread  124 . Once the nut  110  is in position, the washer  112  is inserted over the pin  94 . The first frustoconical portion  114  is assembled such that the pin  94  is positioned within the throughbore  115 , with the wide end of the first frustoconical portion  114  being offered to the pin first, so that the narrow end faces outwards. The collet  100  is also offered to the pin  94  so that the pin is co-axial with the throughbore  106  of the collet  100 . An end portion of the collet  100  contacts and partially overlays part of the small diameter end of the first frustoconical member  114 . The second frustoconical member  116  is screwed onto the end of the pin  94  via the co-operating threads  126  and  118 , but is reversed with respect to the first frustoconical portion  114 , so that the small diameter ends of the two frustoconical portions  114 ,  116  face one another, and are received within respective ends of the throughbore  106  of the collet  100 . The end stop  120  prevents the pin  94  from protruding beyond the second frustoconical portion  116 . The assembled bolt hole engaging device  90  is shown in  FIG. 7   a , in its unexpanded configuration. 
     In order to expand the collet  100 , the nut  110  is driven along the thread  124  to urge the washer  112  and the first frustoconical member  114  towards the second frustoconical member  116 . This action forces the frustoconical members  114 ,  116  into respective ends of the collet  100  so that the collet  100  engages the tapered inner surfaces of the frustoconical members  114 ,  116 . As the frustoconical members  114 ,  116  are driven into the ends of the collet  100 , the portion of the inner diameter of the members  114 ,  116  in contact with the collet  100  becomes progressively larger. The resultant expansion force on the collet  100  causes the slits  102  to separate at the ends of the collet  100 , thereby expanding the collet  100 . 
     Alternatively, the collet  100  could be replaced with a segmented collet similar to that described for the first embodiment and having an inner tapered surface at each end of the segment, which tapered surface is substantially complementary with the angle of taper of the frustoconical portions. Indeed, the expandable member of any of the embodiments described herein (e.g. the collets  40 ,  100 ,  196  and  240 ) can be used interchangeably with any expander device. In particular, the expandable collet  100  is especially suited for use with any embodiment of expander device. 
     As described for the previous embodiment, the flanges  70  shown in  FIGS. 8 and 9  are provided to join portions of pipeline  76  and have a bolt hole  72  and a small gap  74  therebetween.  FIGS. 8   a  to  8   b  show the bolt hole engaging devices  90  being inserted into the adjacent bolt holes  72  and the collet  100  expanded in the manner previously described such that the formations  104  and a substantial proportion of the outer circumference of the collet  100  is in contact with the bolt hole  72 . 
       FIGS. 9 and 10  show a force transmission system  140 . The force transmission system  140  comprises a drive mechanism  154 , a spacer bar  166  and two arms  144 ,  170 . The first arm  144  has a hooked portion  146  at its lower end, and at its upper end the arm  144  is pivotally connected to the drive mechanism  154  by pivot pin  150 . The second arm  170  has a lower hooked portion  172 , and a hook  176  at the upper end of the arm  170 . A spacer bar  166  is pivotally connected between the arms  144 ,  170  at respective pivot pins  148  and  174 , located between the two ends of each arm  144 ,  170 . 
     The drive mechanism  154  has a tube  158  that is internally threaded to receive a threaded bolt  156 . The bolt  156  is axially moveable with respect to the tube  158  by means of the threads (not shown). One end of the bolt  156  is provided with a head  160  to retain the end of the bolt  156  in the hook  176  of the arm  170 . The bolt  156  terminates in a nut  161  that is used to apply torque to the bolt  156 . A thrust bearing  162  is positioned between the head  160  and the nut  161 . The thrust bearing  162  has a washer  163  on each side thereof. 
     The force transmission system  140  is attached to the bolt hole engaging devices  90  by positioning the hooks  146 ,  172  around the protrusions  98  as shown in  FIG. 9   b . The drive mechanism  154  is then pivoted around the pivot pin  150  into a position parallel with the spacer bar  166  and the head  160  locates in its seat on the outer side of the hook  176 . The nut  161  of the bolt  156  is then turned to drive the bolt  156  into the tube  158  and draw the ends of the arms  144 ,  170  closer together. As the nut  161  is turned, the thrust bearing  162  reduces the amount of torque required to drive the nut  161  and spread the flanges. Since the spacer bar  166  is maintained in position throughout the operation, the arms  144 ,  170  pivot around pivot pins  148 ,  174  and push the lower hooked ends  146 ,  172  outwards. This separates the flanges  70  as shown in  FIG. 9   d.    
     The positioning of the spacer bar  166  can be altered to vary the direction of movement of the bolt hole engaging devices  90  or to vary the force applied to them. A shorter length between the hooked ends  146 ,  172  of the arms  144 ,  170  and the pivot points  148 ,  174  and a relatively longer length between the pivot points  148 ,  174  and the ends  150 ,  176  attached to the drive mechanism  154  results in a greater force being applied to the bolt hole engaging devices  90 . However, the path followed by the ends  146 ,  172  of the arms  144 ,  170  tends to be more arcuate with smaller distances between the pivot points  148 ,  174  and the ends  146 ,  172 . Thus the ratio of the distance between the end of each arm  144 ,  170  and the pivot points  148 ,  174  can be varied in order to control the force applied, and the radius of movement of the devices  90 . 
     Alternatively, a fixed length bar  166  can be provided. According to this simplified embodiment, in order to cater for different widths of flange  70 , several nuts  110  having different lengths of collar can be provided so that the correct length of collar can be selected depending on the distance between adjacent flanges  70 . This ensures that the tool is adaptable to be used on different flange widths without changing the length of the spacer bar and enabling the collet to be correctly positioned within the bolt hole  72 . Also, several different lengths of engaging devices  90  can be supplied, optionally with expander devices lacking the optional lip  46 , so that the devices can be inserted into the bolt holes  72  and expanded at any required depth to suit the width of the flanges. Thus, with a wide flange, the collet can be inserted deep into the bolt hole before being expanded close to the inner end of the bolt hole, without having to adjust the spacer bar  166 . Likewise, with a narrow flange, the collet can be inserted just inside the outer end of the bolt hole before being expanded closer to the outside of a smaller flange, again without having to adjust the position of the spacer bar  166 . 
     Rather than driving the expanded bolt hole engaging devices  90  apart using drive mechanism  154  having the internally threaded tube  158  which receives the bolt  156 , the force transmission system  140  can use a hydraulic system. The hydraulic system can comprise a piston retractably accommodated within a chamber. A supply of hydraulic fluid from an external source can be used to fill the chamber and push the piston axially outwardly so that it acts to separate the arms  144 ,  170  in the same manner as the tube  158  and bolt  156 . This system allows accurate monitoring of the force applied to the bolt hole engaging devices  90 , and higher forces can be applied. 
     An alternative embodiment is shown in  FIG. 12 , which is a perspective view of part of a bolt hole engaging device  190 . The bolt hole engaging device  190  comprises a frustoconical portion  192 . The frustoconical portion  192  has four outer faces  194 . A collet  196  is provided in four segments  198 . The profile of the inner face of the segments  198  matches the profile of the outer faces  194  of the frustoconical member  192 . 
     The embodiment shown in  FIG. 12  is a partial hybrid between the first described hydraulic embodiment and the second described mechanical embodiment. The particular embodiment in  FIG. 12  is mechanically driven by advancing a nut (not shown) along the threads  197 . However, the collet  196  is segmented. Also, the tapered bearing surfaces between the collet  198  and the frustoconical portion are flat, rather than conical. 
     Similarly,  FIG. 13  is an alternative embodiment that combines different aspects of the embodiments previously described. An exploded perspective view of the bolt hole engaging device  220  is shown in  FIG. 13 . The device  220  comprises a body portion  222 , a nut  236  and collet  240 . 
     The body portion  222  comprises a head  224  having two cylindrical protrusions  228  on opposing sides thereof. The body portion  222  also has a pin  230  with a frustoconical end portion  232  integrally formed at one end of the pin  230 . A threaded portion  226  is provided between the pin  230  and the head  224 . 
     The nut  236  has a thread  238 , which cooperates with the thread  226  of the body portion  222 . The collet  240  is provided in four segments  242  and at one end  244  each segment  242  is tapered to match the shaped frustoconical portion  232 . 
     In operation, the bolt hole engaging device engages the bolt hole  72  by advancing the nut  236  along the threads  226  to the pin  230  axially with respect to the segments  242  and pull the tapered parts of the frustoconical portion  232  against the matching tapered end portion  244  to thereby expand the collet  240 . Once the bolt hole engaging device  220  is forced against the bolt hole  72 , the force transmission system  140  described for the second embodiment can be coupled around protrusions  228 . The force transmission system  140  is operated to separate adjacent flanges  70  in the same manner as previously described for the second embodiment. 
     Modifications and improvements can be made without departing from the scope of the invention. For example, the angle of inclination of the tapered portions can be varied in order to adjust the amount radial expansion relative to the amount of axial travel of the expandable member or collet, and thereby change the force that must be applied in order to expand the device. The tools can be modified slightly to accommodate different collets which can be used interchangeably in combination with the different expender tools. For example, the body portion  38  can be provided with two frustoconical portions with the small diameter ends facing one another so that the collet  100  from the second embodiment that expands into a zigzag configuration can be used with the expander tool of the first embodiment.