Abstract:
A connector for fastening a gas chromatography capillary column to chromatography equipment includes a securing nut and ferrule on a first portion of the connector for releasably holding the capillary column in a position relative to a second portion of the connector. The first portion rotates relative to the first portion and translates a limited amount relative to the first portion. A pin on the first portion extending into an annular groove around a circumference of the first portion may allow this rotation and limited translation. The second portion has a threaded end adapted to screw into the chromatography equipment with the first portion remaining relatively rotation free as the second portion is screwed into place.

Description:
BACKGROUND 
     Gas chromatography equipment requires connecting very thin capillary tubes to equipment, and often disconnecting and reconnecting the tubes during operations. Typically the installer passes the column through a threaded fastener containing a ferrule with the fastener screwed into/onto a mating inlet of the equipment. If the column installation depth is too long or too short, chromatographic problems may result. It is also difficult sometimes to reach the installation inlets, and if the column must be changed during use or immediately after use, the column and fastener are hot and the user must wait a long time until they cool. Because the installation port of the GC analyzers are hot after use, it is easy to burn fingers when connecting the columns, and in the rush to install hot parts threads are often cross-threaded, leading to further installation delays and damage to equipment. 
     After use, the oven needs to cool down to a temperature comfortable to the user&#39;s touch so the nut that holds the column in place can be loosened by hand. It can take up to 20 minutes to cool the parts. After detaching the nut, a new column is inserted through the nut and ferrule and positioned into the injector at a specified depth. The nut and ferrule are then finger-tightened and given an extra half turn with a wrench until the column is secured. If the oven is not cooled down enough, the user&#39;s fingers will be burned when they touch the capillary nut. Thermal installation gloves help prevent burns, but gloves fray or stretch and impair the sensitivity of tightening. 
     Setting an appropriate column depth is also important since the depth affects reproducibility of the results. The columns are often marked with correction fluid to denote the correct installation depth, but the correction fluids are messy, they smear and they burn in the oven. 
     An improved installation mechanism is needed. 
     BRIEF SUMMARY 
     A fastening assembly is provided which has an installation hub and a second securing nut. The hub is about ⅛ inch below or upstream of the optional wrenching surface of the main body, allowing the user&#39;s fingers to stay well below and to the outside of a mating inlet of the equipment which gets very hot during use. The hub&#39;s low thermal mass makes it more comfortable to install or manually remove without waiting for the inlet/detector to cool. The hub also acts as a tightening device so the GC column can be hand-tightened into place with a slight mechanical advantage over the traditional, smaller nut, thus eliminating the need for a wrench. 
     Upstream of the hub is a second nut with a compression ferrule that holds the column at a constant length during the installation process. An installation gauge can help set a proper and constant installation depth to assure the accuracy and reproducibility of the analysis. 
     The capillary GC column is threaded through a securing nut, and a main body which contains a securing base on the upstream side of the base. A lower or upstream ferrule is placed between the securing base and the main body and an upper or downstream ferrule is on the downstream side of the main body. Both ferrules point with their tapered end toward the column&#39;s end which extends through and past the main body. About 1 cm is trimmed from the end of the capillary using a scoring wafer or scoring pen to remove any graphite introduced inside the column from passing through the ferrules or main body. The securing nut is tightened to the securing base to compress the ferrule against the securing base and is tightened until the column can slide through the lower ferrules but with resistance. 
     If the column installation depth is known for the particular equipment, usually a GC injector/detector, then the column installation depth is adjusted to extend beyond the main body a distance specified according to the analytical equipment manufacturer&#39;s recommendations, and this adjustment is done while the securing body is apart and separate from the analytical equipment. When the desired length of the column extends beyond the main body the securing nut is tightened against the securing base so the column will not slide relative to the securing base. The securing base can rotate within the main body and slide slightly (about 1 mm) relative to the main body, along the column axis. The main body is then connected to the equipment. 
     The main body is rotated, typically threaded into, a standard mating aperture on the inlet of the gas chromatography inlet or detector to fasten the column to the equipment. The securing base is allowed to freely rotate relative to the rotating main body during this rotational fastening. As the main body is fastened to the equipment the upper ferrule is seated to the equipment and restrains movement and rotation of the column. 
     To check and see if the upper ferrule is seated or swaged properly the securing base is urged gently upwards or downstream towards the equipment. If movement is noticed the securing base is pulled downward as far as it will go and the main body is retightened, with the securing base being urged upwards to recheck the seating. The column is ready to be leak checked when the securing base is no longer freely movable in and out of the main body. 
     The interface between the securing base and the main body is checked for leaks, as is the location where the column exits the securing base and also the location between the lower securing nut and the securing base. The column is then installed and ready for use. 
     There is thus advantageously provided a first embodiment of a connector for connecting a gas chromatography capillary column to chromatography equipment, where the equipment has a connection for releasably connecting to capillary columns. The connector has a longitudinal axis along which the capillary column extends during use. The connector includes a securing body, a securing nut and a main body. The securing body has an upstream and downstream end with a ferrule recess in the upstream end configured to receive an upstream ferrule. The securing body also has an annular recess extending around an exterior circumference of the downstream end of the securing body. The securing nut holds the upstream ferrule in the securing body. The main body has an upstream and downstream end with a recess in the upstream end of the main body that is sized to slidably and rotatably receive the downstream end of the securing body. The downstream end of the main body is configured to releasably connect with the releasable connection on the equipment. The downstream end of the main body has a ferrule recess into which a downstream ferrule can be placed during use. The main body has a part extending into the annular recess to limit motion of the securing body relative to the main body in at least one direction along the longitudinal axis, with the longitudinal axis extending through the securing nut, upstream ferrule, securing body and main body. 
     In further variations of this first embodiment, a finger gripping surface is connected to the main body and located outward from the longitudinal axis a distance sufficient to allow manual tightening of the connection with the chromatography equipment sufficient for use of the equipment and without using wrenches. The finger gripping surface may be on the outer periphery of a flange, where the flange having a plurality of holes there through. The securing nut may be threaded onto the upstream end of the securing body. The connection with the equipment may comprise a threaded connection and the main body may have external threads on the downstream end configured to mate with the threaded connection on the equipment. A wrenching surface is optionally provided on an exterior surface of the main body to allow one to mechanically tighten the main body to the connection on the equipment. A downstream ferrule can be seated in the recess in the downstream end of the main body during use. The annular recess may have an outwardly extending wall on opposing sides of the recess, with one wall abutting a shoulder on the main body to limit movement of the securing body along the longitudinal axis relative to the main body. 
     In a further embodiment there is advantageously provided a connector for connecting a gas chromatography capillary column to chromatography equipment having a releasable connection to connect the column to the equipment, where the capillary column and connector have a common longitudinal axis. The connector includes first means on a first portion of the connector for releasably holding the capillary column in a position relative to a second portion of the connector. The connector also includes means for adjusting the axial position of the first means relative to the second portion of the connector, and means for allowing the first means to rotate relative to the second portion of the connector as the connector is fastened to the equipment during use of the connector. The connector also includes means for connecting the second portion to the equipment during use of the connector. 
     The first means may include a threaded securing nut the tightening of which causes a ferrule to clamp against the column and the loosening of which allows the column to slide relative to the ferrule. The means for allowing the first means to rotate may include a pin on the second portion extending into a recess on the first portion. The means for allowing the first means to rotate may include a pin on the second portion extending into a recess on the first portion. The connector may further include an enlarged gripping means for manually tightening and cooling the connector. The connection on the chromatography equipment advantageously includes a threaded connection and the means for connecting comprises a threaded end on the connector configured to threadingly engage the threaded connection on the chromatography equipment. 
     There is also advantageously provided a method for using a connector to connect a gas chromatography capillary column to chromatography equipment having a releasable connection, where the capillary column and connector have a common longitudinal axis. The method may include passing the capillary column through a securing nut and first ferrule, where the securing nut threadingly engages the first body and the first ferrule held in a recess in the first body. The capillary column is passed through a second body main body and second ferrule so a distal end of the capillary column extends beyond the second ferrule. The first body rotates within the second body and relative to the second body. The first body is connected to the second body to allow the first body to slide within and relative to the second body a short distance to adjust the capillary column length but is prevented from being withdrawn from the second body by a restraint. The method further includes cutting off a portion of the distal end and tightening the first ferrule to limit motion of the capillary column relative to the first body before or after the cutting step. The method also includes rotating the second body relative to the first body to fasten the connector to the equipment while allowing the first body and second bodies to translate along the longitudinal axis. 
     In further variations, the method also includes translating the first body relative to the second body along the longitudinal axis to move the distal end of the capillary column away from the equipment. The method may also include rotating the second body relative to the first body to move the distal end of the capillary column toward the equipment. The relative rotation may be achieved by having a portion of the second body extend into an annular groove extending around a circumference of the first body. The first body may be prevented from being withdrawn from the second body by having a portion of the second body extending to an annular groove extending around a circumference of the first body. 
     The method may also include adjusting the distance by which the distal end of the capillary column extends beyond the second portion to a predetermined distance after cutting off a portion of the distal end. The adjusting may include the intermediate steps of rotating the second body relative to the first body to fasten the connector to a base having a connection like that of the equipment followed by extending the cut distal end through a hole in a base and along a scale until the distal end reaches a desired location on the scale, and then performing the tightening step of the originally described method. The rotating step may be achieved by manually rotating an enlarged hub on the second body to achieve a connection sufficient for use. 
     An apparatus is also optionally provided for adjusting the length of a gas capillary column. The scale has a base with a releasable connection just like the connection used to connect gas capillary columns to chromatographic analyzers. The base has a hole extending therethrough and aligned with a longitudinal axis of the connection so that a capillary column connected to the base can pass through the hole during use. A scale extends from the base and along the longitudinal axis opposite the connection. The scale has printed indicia thereon indicating the length by which a distal end of the capillary column extends beyond a predetermined location. The printed indicia is preferably fractions of an inch or centimeter, but could be length indications for specific types of applications or equipment. The releasable connection may include a female threaded coupling. The measurement device described here (but not the connection to the GC column) is commercially available from several GC manufacturers/vendors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers to like parts throughout, and in which: 
         FIG. 1  shows a perspective view looking downstream onto the connector assembly of this invention; 
         FIG. 2  shows a perspective view looking upstream onto the connector assembly of  FIG. 1 ; 
         FIG. 3   a  shows a side plan view of a main body used in the assembly of  FIG. 1 ; 
         FIG. 3   b  shows a sectional view of the main body of  FIG. 3   a  taken along section  3   b - 3   b  of  FIG. 3   a;    
         FIG. 4  shows a side plan view of the connector assembly of  FIG. 1 ; 
         FIG. 5  shows a top plan view of the connector assembly of  FIG. 3 ; 
         FIG. 6  shows a bottom plan view of the connector assembly of  FIG. 3 ; 
         FIG. 7  shows a cross sectional view taken along  7 - 7  of  FIG. 5 ; 
         FIG. 8  is a perspective view of an installation gauge especially useful with the connector assembly of  FIG. 1 ; 
         FIG. 9  is a front plan view of the gauge of  FIG. 8 ; 
         FIG. 10  is a left side plan view of the gauge of  FIG. 9 , with the opposing side view being the mirror image thereof; and 
         FIG. 11  is a sectional view taken along  11 - 11  of  FIG. 9 ; and 
         FIG. 12  is a schematic view of a gas chromatography column connected to equipment through a connector assembly 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-7  and  12 , a tubular gas chromatography (GC) column  10  is releasably connected to a sample injector  11  at one end and to a detector  12  at the other end of the column, both using a connector assembly  14 . The GC column  10  is typically placed inside an oven  13 , so the connector assembly  14  is hot. The analytical equipment  15  typically includes a GC analyzer that includes the injector  11 , detector  12 , column  10  and oven  13 , with the column and connector  14  typically located inside the oven. The GC analyzer has a threaded mating inlet  16  into which an end of the column  10  fits. As used herein, upstream and downstream refer to the flow direction in the GC column from the injector  11  toward the detector  13 , with a downstream part being closer to the detector  12  along the flow path of the capillary tube than is an upstream part, and an upstream part being farther from the detector  12  along the flow path than a downstream part. A downstream flow or direction is toward the detector  12 , and an upstream flow or direction is away from the detector  12 . These connectors and equipment are usually arranged so the connectors are oriented as in  FIGS. 4 and 7 , with upstream being down, and downstream being up as shown in those figures. Thus, upper and lower are with respect to these directions and  FIGS. 4 and 7 . 
     Referring to  FIGS. 1-7  and  12 , the GC column typically comprises a long, thin capillary tube of silica having a distal end  17  connected to the equipment  15  so that gases passing through the tube  10  enter the detector  12 . The connector assembly  14  contains a securing nut  18 , lower ferrule  20 , securing base  22 , main body  24  and upper ferrule  26 , with the GC column passing sequentially through these parts, namely the securing nut  18 , lower ferrule  20 , securing base  22 , main body  24  and upper ferrule  26 , respectively. The securing nut may be a cup-shaped part with a wrenching or hand gripping surface  28  on the exterior for easy tightening by hand, with the inside  30  configured to receive the lower ferrule  20  and a hole  32  in the otherwise closed end through which the GC column passes. The depicted configuration has a rounded exterior with opposing flattened sides to form the wrenching surface  28 , but other exterior configurations could be used, such as a knurled surface  28  for hand tightening. The interior  30  opens downstream toward GC column end  17  and may be threaded. The lower and upper ferrules  20 ,  26 , respectively, are typically of graphite, vespel/graphite, or other malleable, temperature resistant materials and cylindrical with a tapered surface on one end. Preferably both ferrules  20 ,  26  preferably point with their tapered side toward the column distal end  17 . A hole extends through the ferrules  20 ,  26  through which the GC column passes. 
     The securing base  22  has a male end projecting upstream and threaded to engage with the threads on the interior  30  of the securing nut. The securing base  22  has a tubular downstream end  34  ( FIG. 7 ) extending downstream toward the detector  12  with an annular groove or recess  36  ( FIG. 7 ) extending around an outer periphery of the securing base  22 , which recess may be adjacent downstream end  34 . The upstream end of the securing base  22  preferably has wrenching surface  35 , which may comprise a plurality of opposing flats or a knurled surface. 
     The main body  24  has a tubular body  40  with outwardly extending hub  42  preferably having a knurled exterior surface. A cylindrical internal passage  44  extends through the main body  24  with an inwardly stepped shoulder  46  ( FIG. 7 ) or other partial obstruction located toward the downstream end  48  of the body  40 . Advantageously, the end  48  is about an inch from the hub  42  to help distance a user&#39;s fingers gripping the hub  42  from the hot connection with the equipment  15 . The upstream end of the passage  44  is sized slightly larger than the downstream end  34  of the securing base so the end  34  slides (and rotates) within the passage  44  until the end  34  abuts shoulder  46 . A fastener  38  such as a pin, set screw or set pin extends through main body  24  and fits into recess  36  in the securing base when end  34  abuts shoulder  46 . The recess  36  allows limited axial movement of securing base  22  along the GC axis through the securing base  22 . About 0.05 inches of travel is believed suitable but the amount of travel can vary. Optionally, a plurality of holes  50  can be placed in the outwardly extending flange portion of hub  42 . Ten such holes  50  are shown ( FIGS. 5-6 ), but the number can vary. The downstream end  48  of main body  24  has threads configured to mate with the mating inlet  16  of the equipment  15 . A wrenching surface  52  can optionally be provided on the exterior surface of body  40 . 
     The depicted configuration can be machined, formed or cast into a solid tubular part of a single piece of material. Alternatively, a plug  54  ( FIG. 7 ) is optionally placed into the downstream end  48  of the main body  24 . The plug  54  has a hole  56  sized to GC column  10  passes therethrough at the center of the tubular body  40 . A cup-shaped recess  58  is formed in the downstream end of the plug  54  and faces downstream toward detector  12  to receive upper or downstream ferrule  26  ( FIG. 7 ). 
     In use, the GC column  10  passes through securing nut  18 , lower ferrule  20 , securing base  22 , main body  24 , plug  54  and upper ferrule  26 . Tightening the threaded connection between the securing nut  18  and securing base  22  allows the lower ferrule to adjustably grab the GC column  10  and hold it. The sliding and rotating of the securing base  22  relative to the main body allows rotational and axial movement of the GC column  10  between the securing base  22  and main body  24 . That allows the securing nut and securing body to grip the GC column  10  and allow it to move while the threaded end  48  of the main body is rotatably screwed into the mating connector  16  of the GC equipment  15 . The movement allows rotation and limited axial movement to more accurately engage distal end  17  of the GC column with the equipment  15 . 
     In use, the GC column  10  is threaded through securing nut  18 , lower ferrule  20 , securing base  22 , main body  24 , plug  54  and upper ferrule  26 . Again, both ferrules  20 ,  26  point with their tapered end toward the column&#39;s end  17  which extends through and past the main body  24 . About 1 cm is trimmed from the end of the capillary column  10  using a scoring wafer or scoring pen to remove any graphite introduced inside the column  10  from passing through the ferrules  20 ,  26 , main body  24  or other parts. The securing nut  18  is then tightened to the securing base  22  to compress the lower ferrule  20  against the securing base and is tightened until the column  10  can slide through the lower ferrule but with resistance. 
     If the installation depth of the GC column  10  is known for the particular equipment  15 , then the column installation depth is adjusted to extend beyond the main body a distance specified according to the analytical equipment manufacturer&#39;s recommendations, and this adjustment is done while the securing body is apart and separate from the analytical equipment. When the desired length of the column extends beyond the main body the securing nut  18  is tightened against the securing base  22  to fix the length of column extending beyond end  48  of main body  24 , so the column  10  will not slide axially relative to the securing base  22 . 
     The securing base  22  can rotate within the main body  24  and slide slightly (about 1 mm) relative to the main body, along the column axis. The fastener, such as set pin  38  and recess  36  allow rotation and can define some or all of the axial movement, although the end  34  abutting shoulder  46  can also limit the axial movement in the upstream direction toward detector  12 . This allows the main body  24  to be screwed into the equipment  15  without twisting the column  10 , and it allows for minor length adjustment. 
     The main body  24  is then connected to the equipment  15 , but the connection is typically 1 inside oven  13 , or affixed to oven  13  so the connection becomes hot. The main body  24  is rotated, typically threaded into/onto, the mating fitting/inlet  16  on the inlet of the gas chromatography sample inlet  11  or detector  12  or other equipment  15  to connect the column  10  to the equipment. The securing base  22  is allowed to freely rotate relative to the main body  24  as the main body is screwed into the equipment  15 . As the main body  24  is fastened to the equipment  15  the upper ferrule  26  is seated to the equipment  15  and also grips the column  10  to restrain movement and rotation of the column. When installed, the upper and lower ferrules  20 ,  26  grip column  10 , and the connector assembly  16  is of fixed configuration and does not rotate or translate. 
     To check and see if the upper ferrule  26  is seated or swaged properly against the column  10 , the securing base  22  is urged gently upwards or downstream towards the equipment  15 . If movement is noticed the securing base  22  is pulled upstream as far as it will go (set pin  38  and groove  36  limit this movement) and the main body  24  is retightened. The check and retighten procedure is repeated until the column is fully seated in the equipment  15 . The column  10  is ready to be leak checked when the securing base  22  is no longer freely movable in and out of the main body  24 . 
     The interface between the securing base  22  and the main body  24  is then checked for leaks, as is the location where the column exits the securing base and also the location between the lower securing nut and the securing base. The column is then installed and ready for use. The wrenching surfaces  35 ,  52  allow the use of tools if desired, while also allowing manual manipulation. But the hub  42  is larger in diameter than the traditional fastening nut, preferably with a diameter of about one inch, and that larger diameter allows greater tightening force by using fingers alone, and can allow installation without the use of tools. 
     To disconnect the GC column, the oven  13  is programmed to ambient conditions and the oven is allowed to cool. Because the column  10  and connector assembly  14  get very hot during use, the system gas flows are turned off. After the connector assembly  14  is cooled enough, the hub  42  is manually manipulated so the main body  24  and end  48  of tube  40  are unscrewed from the equipment  15 . The column  10  can then be removed by loosening the securing nut  18  and withdrawing the column  10  for reuse. Alternatively, another connector assembly  14  can be previously installed onto another column  10  for immediate reconnection. 
     The ability to adjust the extension of the column  10  by using the connector assembly  14  and to hold that adjusted configuration can save a lot of time. The ease of manipulation while the thin tube is inserted into the mating connector  16  of the GC equipment is also very useful. The larger diameter hub provides for easy gripping, while the securing nut  18  and securing base  22  hold the GC column in position relative to the threaded end  48  of the main body. The hub  42  and the longer upstream tube  40  allows easier insertion and manipulation of the GC column  10 , and the connector assembly  14  allows rotation without twisting and breaking the column during the rotation needed to connect to the equipment. The ability to axially move the GC column relative to the partially engaged main body  24  allows fine adjustment to more securely and safely seat the thin GC column into the equipment  15  without damage. Moreover, the larger main body  24  provides a larger heat conduction surface and radiating surface so the hub  42  cools faster. The GC column  10  and assembly  14  get hot during use, too hot to comfortably handle. The improved heat dissipation is believed to help the hub  42  cool faster so an operator can unfasten the main body  24  faster than with the prior art. The hub  42  can optionally be made of aluminum to further enhance cooling, and the holes  50  are believed to increase radiation area while increasing conduction to air passing through the holes. 
     The connector assembly  14  thus helps reduce the time waiting for the inlet or detector on the equipment  15  to cool before installing the column because the connector  14  is handled and distances the user&#39;s fingers from the inlet and other hot equipment. The elimination of the need to cool the injector and detector also reduces the time for the equipment  15  to heat back up to operating time and stabilize before resuming analysis. The cooler hub  14  also allows a user to use bare fingers rather than thermal insulating gloves and that allows for greater finger sensitivity on tightening the mating parts. The ability to pre-determine the length of the GC column  10  beyond the end  48  of the main body  24  allows for more accurate installation where the distance is predetermined and known. The adjustment of the length and the ability to secure that length with a compression system, eliminates the possibility for errors while ensuring proper seating and installation. The installation maintains the upper ferrule  26  away from the distal end  17  of the column  10  and in the cup  58  so the end  17  cannot slip into the ferrule during installation. The installation does not require correction fluid or a septum to ensure correct column installation depth. 
     Referring to  FIGS. 8-11 , an installation gauge  70  is preferably used to ensure the appropriate length of the column  10  in the connector assembly  14 . The gauge  70  has a graduated scale  72  typically a flat ruler marked with appropriate dimensions such as mm or inches and fractions thereof to gauge the length of the column  10 . The scale  72  is fastened to a base  74  that may be adapted to be held by the user&#39;s hand. The depicted base  74  has a circular disc about 2-3 cm in diameter and 0.5 cm thick, with a flange  76  extending upward from the disk at a right angle. The scale  72  is fastened to the flange  76 . Various fastening mechanisms can be used, including adhesives, welding, or threaded fasteners. In the depicted embodiment a set pin  78  holds the scale  72  to the flange  76 , with a square end of the scale resting against the upper surface of the base  74 . 
     A hole  80  extends through the base  74 , with the hole sized to allow capillary tube  10  to pass therethrough. The bottom of the base  84  is configured to resemble the mating inlet  16  on GC equipment  15 , so there is a conical surface  82  surrounding hole  80  into which upper ferrule  26  fits during use of the gauge  70 . The tapered surface  82  is surrounded by a female connector  84  with internal threads configured to threadingly engage threads on out outer surface of end  48 . A wrenching or tightening surface  86  may be placed on the exterior of the connector  84 . 
     In use, the column  10  is inserted through the connector assembly  14  as described earlier and the column  10  is cut leaving about 1 cm or more of the column extending beyond the upper ferrule  26 . The column end  17  and end  48  are inserted into/onto the mating inlet of the equipment  84  and the column  10  through hole  80 . The hub  42  is rotated and threaded into the female connector  84  until the upper ferrule  26  starts to compress. The length of the column is adjusted to the desired length, using the scale  72  to measure the desired insertion distance into the equipment  15 . When the length of the column is adjusted then the connector  84  can be tightened to clamp the ferrule  26  against the column  10  and restrain movement of the column relative to the gauge  70 . The securing nut  18  is then tightened so the lower ferrule  20  clamps the column  10  to restrain axial movement of the column  10  relative to the connector assembly  14 , and this should be done with the securing base in the fully extended position to achieve the correct premeasured position and to allow for proper leak checking. This tightening of the nut  18  could be done without tightening the connector  84  on the gauge  70 . 
     In short, the bottom of the gauge  70  simulates a connector with the equipment  15  and allows the length of column  10  to be visually adjusted outside of the equipment, at which time the desired column length is either marked or set by clamping the column  10  in the connector assembly  14  (via securing nut  18  and lower ferrule  20 ). 
     If the connector assembly  14  is not being used, the column can be marked at the base of the column nut to identify the correct depth after installation. The mark on the column allows correctly positioning the column relative to the equipment  14  before tightening the nut ¼ to ½ turn past finger tight. 
     The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.