Abstract:
Aspects of the invention are directed to a kit for use with a tube terminating in a flange, where the flange defines an outwardly projecting flange shoulder and is characterized by a maximum external flange diameter. The kit comprises a pairing ring, a nipple, and a nut. The pairing ring defines a pairing ring engagement feature. The nipple defines a nipple engagement feature and external nipple threads, and is characterized by a minimum internal nipple diameter greater than the maximum external flange diameter. Lastly, the nut defines internal nut threads and an inwardly projecting nut shoulder, and is characterized by a minimum internal nut diameter greater than the maximum external flange diameter. The kit is adapted to be configured such that, simultaneously: (i) the pairing ring surrounds a portion of the tube adjacent to the flange; (ii) the pairing ring abuts the outwardly projecting flange shoulder; (iii) the pairing ring abuts the inwardly projecting nut shoulder; (iv) the nipple at least partially surrounds the outwardly projecting flange shoulder; (v) the nipple at least partially surrounds the pairing ring; (vi) the nut at least partially surrounds the pairing ring; (vii) at least a portion of the internal nut threads engage at least a portion of the external nipple threads; and (viii) the nipple engagement feature engages the pairing ring engagement feature so as to inhibit relative rotation between the nipple and the pairing ring.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to the field of metal tube couplings and, more specifically, to improved assemblies for face sealed fittings. 
       BACKGROUND OF THE INVENTION 
       [0002]    Metallic tubes are commonly used for the transfer of fluids such as gasses or liquids. In particular, highly pure fluids, as well as toxic, corrosive, flammable or pyrophoric fluids are preferably handled within all-metallic delivery tubing and manifolds. The efficient construction of manifolds that include delivery tubing, valves, filters, control instruments and many other components invokes all-metallic couplings wherein sections of tubes, as well as other components are connected into spill-free manifolds. These couplings are known in the art as fittings. 
         [0003]    Face sealed fittings typically comprise opposed tube ends (frequently called “glands”) that define highly polished circular protuberances (“beads”). A coupling is created when a softened metallic gasket is compressed and deformed between two tube ends by means of two threaded nuts. Ideally, the contact between the glands and the deformed gasket corresponds to a spill and leak tight coupling. One such fitting is described in U.S. Pat. No. 3,521,910 to Callahan, et al. and entitled “Tube Coupling.” Another such fitting is described in U.S. Pat. No. 6,161,875 to Yamaji, et al. and entitled “Fluid Coupling.” 
         [0004]    A fitting assembly  100  in accordance with U.S. Pat. No. 3,521,910 is depicted in  FIGS. 1A and 1B , where  FIG. 1A  shows a sectional view, and  FIG. 1B  shows a perspective view. The fitting assembly  100  includes glands  110 ,  120 , which terminate in opposed flanges  112 ,  122 . Flanges  112 ,  122  are drawn together when female nut  130  (with internal threads  132 ) screwably engages male nut  140  (with external threads  142 ). Doing so has the effect of axially tightening beads  111 ,  121  into gasket  180  to form a seal. Unfortunately, at the same time, screwably engaging nuts  130 ,  140  also tends to generate relative rotation between circular beads  111 ,  121 , promoted by friction between female nut shoulder  131  and flange  112 , as well as friction between male nut tip  141  and flange  122 . This unwanted relative rotation can have serious consequences. The relative rotation may, for example, damage sealing surfaces, promote galling and build up a torque inside the assembly, resulting in compromised seal performance, wear and particle generation. Even worse, built-up torque has the tendency to unwind and undo the assembly, particularly when vibrations are present, leading to potentially catastrophic leaks and spills. Such torque buildup may therefore result in costly product and yield losses from leaks and particles, accelerated wear that requires costly and extensive maintenance and repair, and costly downtime, as well as numerous hazardous situations, accidents, spills and related costly cleanups and shutdowns. 
         [0005]    In spite of the torque buildup problem and its implications, fitting assemblies like fitting assembly  100  have become standard metal-to-metal seals in many different applications and industries. These fittings are entrenched into factories around the world and have become globally available from many manufacturers, with full compatibility between products from different suppliers. Becoming a standard in multiple industries has enabled advantageous mixing and matching of many different components from different manufacturers (i.e., modularity) with unprecedented design flexibility. 
         [0006]    While fitting assemblies like fitting assembly  100  are in widespread usage, their less than ideal characteristics have spawned alternative designs that attempt to deal with torque buildup. New designs capable of working with at least some legacy parts are particularly desirable because these parts are so ubiquitous. One such alternative design is described in U.S. Pat. No. 5,887,876 to Aldridge, et al. and entitled “High Purity Gas Fitting with Grooved Gasket.” In this design, a modified thicker gasket includes circular grooves that increase the contact area and the friction between the circular beads and the gasket. Accordingly, higher friction at the seal is able to better balance off friction between the nuts and the flanges to suppress rotation and torque buildup. These modified gaskets are commercially available from Parker Hannifin Corporation (Mayfield Heights, Ohio, USA) with the trade name TorqTite. Unfortunately, this improvement does not consistently eliminate torque buildup problems. Moreover, the grooved gaskets tend to increase the potential entrapment of fluid at the seal, which is disadvantageous in many sensitive applications. 
         [0007]    Other designs have invoked the addition of thrust bearings to mitigate friction between the nuts and the flanges. While not suitable for straightforward upgrade of existing installations, some of these remedies are fully compatible and can fully mate with legacy fittings. For example U.S. Pat. No. 6,382,683 to Albright et al. and entitled “High Pressure Gas Fitting with Non-Rotatable Features” teaches a sliding ring within the construction of the female nut to mitigate transfer of torque from that nut to the remainder of the fitting. These fittings are commercially available from Parker Hannifin Corporation (Mayfield Heights, Ohio, USA) with the trade name Non-Rotational Female Nut. Similarly, legacy fittings that include torque mitigating ball bearings within extended-length female nuts are commercially available from Fujikin Incorporated (Santa Clara, Calif., USA) with the trade name PureRing. However thrust bearings at just the female nut do not mitigate the friction at the male nut, and, accordingly, do not consistently eliminate torque buildup problems. While this situation may be improved by also utilizing additional low profile thrust bearings between the male nut and the flange, the inventors of the present application have empirically found that such remedies still do not fully and consistently eliminate torque buildup issues. Likewise, the present inventors have further determined that other remedies that implement thrust bearings over modified glands such as the invention disclosed in U.S. Pat. No. 6,308,994 to Eidsmore and entitled “Fluid Fitting with Torque Suppression Arrangement” do not perform well enough to justify their additional cost and complexity. 
         [0008]    An entirely different approach is described in U.S. Pat. No. 5,066,051 to Weigl et al. and entitled “Anti-Twist Coupling Assembly with Biasing Means,” wherein a thrust bearing between the female nut and respective flange is restricted from rotation against the male nut by means of axially engaged portions. However, this improvement still lacks a thrust bearing or any other means to prevent the male nut from applying torque to its respective gland. That deficiency may be resolved in the remedy disclosed in U.S. Pat. No. 5,829,796 to Robinson and entitled “Protection of Sealing Surfaces of Metal Face Seals in Tubing Fittings,” wherein thrust bearings on both nuts are axially engaged to effectively prevent any transfer of rotation from the nuts to the glands. This apparatus does seem to eliminate the torque buildup problem. The fittings are commercially available with the trade name “Torque Suppressed Fittings” and sold by the Omnisafe Company (Sunnyvale, Calif., USA). 
         [0009]    Nevertheless, while having positive effects, torque suppressing improvements such as the ones described in the two just-referenced patents are not fully compatible and/or able to mate with legacy fittings. In particular, redesigned nuts that enable thrust bearing engagements cannot mate with legacy nuts. Legacy fittings are typically permanently attached to components and fluid delivery lines. For example in fitting assembly  100  of  FIGS. 1A and 1B , female nut shoulder  131  of female nut  130  has a minimum internal diameter that is smaller than the maximum external diameter of flange  112 . As a result, once gland  110  is welded to a fluid delivery line or a component, flange  112  prevents the removal of female nut  130 . Likewise, male nut  140  has a minimum internal diameter that is smaller than the maximum external diameter of flange  122 . Here again, once gland  120  is welded to a fluid delivery line or a component, flange  122  prevents the removal of male nut  140 . 
         [0010]    This permanent attachment prohibits a cost effective transition to the implementation of torque-free fittings in both existing and new plants. It also more than doubles the cost and logistic-related burdens of component inventories with many different varieties of female and male nuts. Hence, upgrading legacy fittings to use torque-suppressing nuts and axially engaged thrust bearings requires a substantial rework, including gland cutoff and reattachment by welding. Not surprisingly, such prohibitively expensive and disruptive upgrades have been avoided in almost 100% of worldwide plants. At the same time, the maintenance and repair of multimillions of fluid delivery lines and components within these plants keep the market for legacy-fitting-compatible components and gas lines in par with the market for new parts. Supporting both existing plants with their legacy fittings, and a transition of new plants and new equipment that use (incompatible) torque-suppressing fittings is prohibitively expensive and logistically difficult for most manufacturers and end-users since inventories would have to include both legacy and torque-suppressing parts. Alternatively, keeping parts without glands and fittings for a last minute weld-on per demand can stretch lead times and can severely impact the trend of “lean-manufacturing.” With such adverse economic impact, torque eliminating fittings have not gained widespread acceptance and are marginalized into a small portion of the worldwide market. 
         [0011]    Legacy fittings that are not permanently attached to components or fluid delivery lines with the trade name “Split Nut Assemblies” (SN Assemblies) are commercially available and sold by the Swagelok Company (Sohon, Ohio, USA). These fittings are disclosed in U.S. Pat. Nos. 5,547,229 and 5,636,876 to Eidsmore and entitled “Fluid Coupling Assembly.” In these designs, the male nut is split into two halves that are held together when fastened into a female nut. The male nut can be easily removed from gland  120  once the fitting is undone by splitting the nut into halves. The female nut comprises three components wherein the functionality of female nut shoulder  131  is provided by a split male nut with a left hand thread. This split male nut is threaded into a bushing adapter to create a female nut. The female bushing adapter comprises a left hand thread on one side and a right hand thread on the other side. The left hand thread matches the one on the left-hand threaded male split nut. The right hand thread matches the thread of a legacy male nut. The female nut is assembled over gland  110  by combining the left hand split nut behind flanges  112  and threading the split nut into the left hand thread part of the bushing. It is removed by the reverse operation. These split nuts are fully compatible with legacy fittings. Their higher cost is offset by reduced inventory costs and reusability. They also enable shorter components because the welding of shorter glands is possible in the absence of nuts (since nuts do not have to be assembled over glands  110 ,  120  during welding). 
         [0012]    In principle, SN fittings may pave a path for upgradeable torque-free fittings. For example, if the axially-engaged thrust bearings can be made in a split form (“Split Torque Eliminators”), such “field-attachable” fittings, if they existed, could break free from the impediment of incompatibility with legacy fittings. With such field-attachable fittings, new components and fluid delivery lines would ideally not include permanently attached fittings. Then torque eliminating field-attachable fittings could be used for new plants and equipment. Such components and fluid delivery lines without permanently attached fittings could also be suitable for use in maintenance, repair and upgrade of legacy plants and equipment by applying legacy (field-attachable) SN fittings. Moreover, in many cases, components and fluid delivery lines could be installed in legacy manifolds with torque-free field-attachable fittings. For example, in these cases, the permanently attached nuts could simply be pushed back, away from flanges  112 ,  122  to free up the glands  110 ,  120  for the field-attachable fittings. 
         [0013]    The additional cost of field-attachable torque-free fittings might be offset by the cost savings from improved reliability, avoiding downtime and catastrophic failure from torque-buildup-driven release, eliminated fittings wear, reduced inventories of components and fluid delivery lines (eliminating the need to keep separate inventories for female and male varieties), avoiding yield reduction from particles generated from gland/gasket galling, and fitting reusability. That said, inevitably higher cost could still limit these torque-free split fittings into a small portion of the worldwide market. In addition, the need to create room for the Split Torque Eliminators will inevitably cause the size of the nuts to grow. Moreover, Split Torque Eliminators could require even larger space and even larger nuts. These “footprint” issues may reduce the appeal of torque-free SN fittings and further reduce their market share. Unfortunately, market share restrictions would eliminate the cost benefits of reduced inventories and its related cost appeal. In the end, prospects of a limited market may reduce the drive to develop and commercialize such currently non-existing products. 
         [0014]    Thus, there is a need for cost competitive, field-attachable, torque-free fittings that are capable of mating with legacy face sealed parts. Such fittings should be restricted to a footprint similar or smaller than the footprint of legacy face sealed fittings. There is also a need for assemblies for gender-free fastening of face sealed fittings. 
       SUMMARY OF THE INVENTION 
       [0015]    Embodiments in accordance with aspects of the invention provide apparatus and methods that address the above-identified needs. 
         [0016]    Aspects of the invention are directed to a kit for use with a tube terminating in a flange, where the flange defines an outwardly projecting flange shoulder and is characterized by a maximum external flange diameter. The kit comprises a pairing ring, a nipple, and a nut. The pairing ring defines a pairing ring engagement feature. The nipple defines a nipple engagement feature and external nipple threads, and is characterized by a minimum internal nipple diameter greater than the maximum external flange diameter. Lastly, the nut defines internal nut threads and an inwardly projecting nut shoulder, and is characterized by a minimum internal nut diameter greater than the maximum external flange diameter. The kit is adapted to be configured such that, simultaneously: (i) the pairing ring surrounds a portion of the tube adjacent to the flange; (ii) the pairing ring abuts the outwardly projecting flange shoulder; (iii) the pairing ring abuts the inwardly projecting nut shoulder; (iv) the nipple at least partially surrounds the outwardly projecting flange shoulder; (v) the nipple at least partially surrounds the pairing ring; (vi) the nut at least partially surrounds the pairing ring; (vii) at least a portion of the internal nut threads engage at least a portion of the external nipple threads; and (viii) the nipple engagement feature engages the pairing ring engagement feature so as to inhibit relative rotation between the nipple and the pairing ring. 
         [0017]    Additional aspects of the invention are directed to an assembly comprising a first tube, a first flange, a first pairing ring, a nipple, and a nut. The first flange is disposed at a terminus of the first tube, defines a first outwardly projecting flange shoulder, and is characterized by a first maximum external flange diameter. The first pairing ring defines a first pairing ring engagement feature. The nipple defines a first nipple engagement feature and first external nipple threads, and is characterized by a first minimum internal nipple diameter greater than the first maximum external flange diameter. The first nut defines first internal nut threads and a first inwardly projecting nut shoulder, and is characterized by a first minimum internal nut diameter greater than the first maximum external flange diameter. When assembled: (i) the first pairing ring surrounds a portion of the first tube adjacent to the first flange; (ii) the first pairing ring abuts the first outwardly projecting flange shoulder; (iii) the first pairing ring abuts the first inwardly projecting nut shoulder; (iv) the nipple at least partially surrounds the first outwardly projecting flange shoulder; (v) the nipple at least partially surrounds the first pairing ring; (vi) the first nut at least partially surrounds the first pairing ring; (vii) at least a portion of the first internal nut threads engage at least a portion of the first external nipple threads; and (viii) the first nipple engagement feature engages the first pairing ring engagement feature so as to inhibit relative rotation between the nipple and the first pairing ring. 
         [0018]    Even additional aspects of the invention are directed to a method for mating tubing. A first tube, a first flange, a first pairing ring, a nipple, and a first nut are initially received. The first flange is disposed at a terminus of the first tube, defines a first outwardly projecting flange shoulder, and is characterized by a first maximum external flange diameter. The first pairing ring defines a first pairing ring engagement feature. The nipple defines a first nipple engagement feature and first external nipple threads, and is characterized by a first minimum internal nipple diameter greater than the first maximum external flange diameter. The first nut defines first internal nut threads and a first inwardly projecting nut shoulder, and is characterized by a first minimum internal nut diameter greater than the first maximum external flange diameter. The elements are assembled such that: (i) the first pairing ring surrounds a portion of the first tube adjacent to the flange; (ii) the first pairing ring abuts the first outwardly projecting flange shoulder; (iii) the first pairing ring abuts the first inwardly projecting nut shoulder; (iv) the nipple at least partially surrounds the first outwardly projecting flange shoulder; (v) the nipple at least partially surrounds the first pairing ring; (vi) the first nut at least partially surrounds the first pairing ring; (vii) at least a portion of the first internal nut threads engage at least a portion of the first external nipple threads; and (viii) the first nipple engagement feature engages the first pairing ring engagement feature so as to inhibit relative rotation between the nipple and the first pairing ring. 
         [0019]    Notably, in one or more embodiments of the invention, each of the above-identified pairing rings may comprise a respective first pairing ring portion and a respective second pairing ring portion, where the second pairing ring portion is manually separable from the first pairing ring portion. 
         [0020]    The above-identified embodiments provide several advantages. More particularly, embodiments in accordance with aspects of the invention may, as just a few examples, provide one or more of:
       1. fittings that are symmetrical/genderless;   2. fittings that are field-attachable/removable over previously welded glands;   3. fittings that are torque free; and   4. fittings that have footprints comparable or smaller than legacy assemblies.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
           [0026]      FIG. 1A  shows a sectional view of a prior art fitting assembly; 
           [0027]      FIG. 1B  shows a perspective view of the  FIG. 1A  fitting assembly; 
           [0028]      FIG. 2A  shows a sectional view of a fitting assembly in accordance with a first illustrative embodiment of the invention; 
           [0029]      FIG. 2B  shows a perspective view of the  FIG. 2A  fitting assembly; 
           [0030]      FIG. 2C  shows an exploded perspective view of the  FIG. 2A  fitting assembly; 
           [0031]      FIG. 3A  shows a sectional view of a fitting assembly in accordance with a second illustrative embodiment of the invention; 
           [0032]      FIG. 3B  shows a perspective view of the  FIG. 3A  fitting assembly; 
           [0033]      FIG. 3C  shows an exploded perspective view of the  FIG. 3A  fitting assembly; 
           [0034]      FIG. 4A  shows a sectional view of a fitting assembly in accordance with a third illustrative embodiment of the invention; 
           [0035]      FIG. 4B  shows a perspective view of the  FIG. 4A  fitting assembly; 
           [0036]      FIG. 4C  shows an exploded perspective view of the  FIG. 4A  fitting assembly; 
           [0037]      FIG. 5A  shows a perspective view of a coupling in accordance with an illustrative embodiment of the invention; 
           [0038]      FIG. 5B  shows a perspective view of a legacy coupling; 
           [0039]      FIG. 5C  shows a perspective view of a plug in accordance with an illustrative embodiment of the invention; 
           [0040]      FIG. 5D  shows a perspective view of a legacy cap; 
           [0041]      FIG. 5E  shows a perspective view of a legacy plug; 
           [0042]      FIG. 5F  shows a perspective view of a coupling-to-bulkhead in accordance with an illustrative embodiment of the invention; 
           [0043]      FIG. 5G  shows a perspective view of a legacy coupling-to-bulkhead; and 
           [0044]      FIG. 6  shows an exploded perspective view of a fitting assembly in accordance with a fourth illustrative embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    The present invention will be described with reference to illustrative embodiments. For this reason, numerous modifications can be made to these embodiments and the results will still come within the scope of the invention. No limitations with respect to the specific embodiments described herein are intended or should be inferred. 
         [0046]    Many of the elements described herein are associated with tubing. As used herein, the “axial” direction is defined as a direction that parallels the central longitudinal axis of the associated tubing. At the same time, an element is “outwardly projecting” if it projects away from the associated tubing. Finally, an element is “inwardly projecting” if that element projects towards the associated tubing. 
         [0047]    Aspects of fitting assembly  200  in accordance with a first illustrative embodiment of the invention are depicted in  FIGS. 2A-2C , where  FIG. 2A  shows a sectional view;  FIG. 2B  shows a perspective view; and  FIG. 2C  shows an exploded perspective view. In the fitting assembly  200 , a seal is created between glands  110 ,  120  and gasket  180 , all of legacy design. Coupling nuts  230 ,  240 , having internal threads  233 ,  243 , are assembled over glands  110 ,  120  by sliding over flanges  112 ,  122 , respectively. The openings  232 ,  242  of nuts  230 ,  240  at shoulders  231 ,  241 , respectively, are larger than flanges  112 ,  122 . Therefore, the nuts  230 ,  240  can be assembled over previously welded glands  110 ,  120 . Pairing ring counterparts  260 ,  260 ′ are placed over gland  110 . Likewise, pairing ring counterparts  270 ,  270 ′ are placed over gland  120 . Pairing ring counterpart  260  includes ribs  261 ,  262 , tooth  263  and flange  264 . Similarly, pairing ring counterpart  260 ′ includes ribs  261 ′,  262 ′, tooth  263 ′ and flange  264 ′. Pairing ring counterparts  270 ,  270 ′ further comprise ribs  271 ,  271 ′,  272 ,  272 ′, teeth (i.e., projections)  273 ,  273 ′ and flanges  274 ,  274 ′. Nut  230  fits over assembled pairing ring  260 + 260 ′, causing combined ribs  261 + 261 ′ to be contained inside opening  232 . Similarly, assembled pairing ring  270 + 270 ′ is surrounded by nut  240  after being placed over gland  120 . 
         [0048]    Nipple  250  is initially assembled over one of the glands  110 ,  120 . Nipple  250  includes leak testing holes  251 ,  251 ′ and male threads  252 . Nipple  250  further defines two pairs of notches (i.e., slots): notches  253 ,  253 ′ overlying gland  120 , and notches  254 ,  254 ′ overlying gland  110  (where notch  254 ′ is opposite notch  254  but is not visible). Bore (i.e., internal opening)  256  of nipple  250  is larger than the diameter of glands  110 ,  120 . Teeth  263 ,  263 ′ of assembled pairing ring  260 + 260 ′ fit and axially engage notches  254 ,  254 ′. Likewise, teeth  273 ,  273 ′ of assembled pairing ring  270 + 270 ′ fit and axially engage notches  253 ,  253 ′. Fastening is accomplished when nuts  230 ,  240  are tightened over nipple  250 . As a result of this tightening, nut  230  applies force against flange  264 + 264 ′, which is axially transferred to flange  112 . Likewise, nut  240  applies force against flange  274 + 274 ′, which is axially transferred to flange  122 . Axial engagement of pairing ring  260 + 260 ′ via teeth  263 ,  263 ′ and notches  254 ,  254 ′, and axial engagement of pairing rings  270 + 270 ′ via teeth  273 ,  273 ′ and notches  253 ,  253 ′, prevent the transfer of any rotation from nuts  230 ,  240  to glands  110 ,  120 . Accordingly, torque free fastening is readily accomplished. 
         [0049]    In forming fitting assembly  200 , the axial depth of notches  253 ,  253 ′,  254 ,  254 ′ preferably exceed the axial length of respective teeth  273 ,  273 ′,  263 ,  263 ′ so as to create gaps  258 ,  258 ′,  259 ,  259 ′, respectively (where gaps  258 ′,  259 ′ are opposite gaps  258 ,  259  but are not visible). These gaps  258 ,  258 ′,  259 ,  259 ′ are preferably designed to limit the axial tightening of fitting assembly  200  and prevent possible bead damage from over-tightening and/or tightening with a missing gasket  180 . 
         [0050]    Fitting assembly  200  may provide several cost benefits to the user. Fitting assembly  200  is, for example, preferably implemented with identical nuts  230 ,  240 , identical pairing ring counterparts  260 ,  260 ′,  270 ,  270 ′, and nipple  250 . As a result, a total of seven parts of three different varieties are needed. This part count compares favorably with two different parts per standard legacy fitting, five parts of five different varieties per legacy split fitting, or four parts of three different varieties per Torque Suppressed Fitting. 
         [0051]    Additional cost benefits may also include reduced inventories of components and fluid delivery lines by eliminating the redundancy of permanently attached male and female nuts, as well as cost benefits associated with avoiding fitting wear, leaks and spills, and yield loss from particles. As discussed above, these cost benefits have a straightforward path into existing applications. There are also additional cost benefits from reusing field-attachable/removable fittings in accordance with aspects of the invention when components and fluid delivery lines are replaced as part of maintenance and repair. Finally, those who are skilled in the art will appreciate that, in spite of their seemingly more complicated assembly, fittings falling within the scope of the invention actually simplify and reduce the effort and duration of fastening face sealed fittings by eliminating an assortment of awkward attempts to minimize torque buildup in legacy fittings. 
         [0052]    Once understood from the teachings provided herein, the various elements of fitting assembly  200  may be formed from conventional materials utilizing well-understood manufacturing techniques. Fitting assembly  200  may, for example, be implemented in stainless steel. For example, pairing ring counterparts 260, 260′, 270, 270′ may be implemented in heat treated 17-4 PH stainless steel, coupling nuts  230 ,  240  may be implemented in tempered 416 stainless steel, and nipple  250  may be implemented in 416 or 304L stainless steel. That said, these specific materials are merely illustrative and other equally suitable materials will also fall within the scope of the invention. In any case, as part of manufacture, the three different parts of fitting assembly  200  are preferably implemented in different corrosion resistant alloys and/or temper varieties to suppress galling and wear. Coupling nuts  230 ,  240  and nipple  250  may be suitable for low cost, Swiss screw-machine manufacturing. Similarly, pairing ring counterparts  260 ,  260 ′,  270 ,  270 ′ may be formed by Metal Injection Molding (MIM) manufacturing. Both manufacturing techniques and equally suitable alternatives will be familiar to one having ordinary skill in the art. Reference is also made to H. Youssef et al.,  Machining Technology: Machine Tools and Operations , CRC Press, 2008; and D. Heaney,  Handbook of Metal Injection Molding , Elsevier, 2012, which are both hereby incorporated by reference herein. 
         [0053]    A fitting assembly  300  in accordance with a second illustrative embodiment of the invention is depicted in  FIGS. 3A-3C , where  FIG. 3A  shows a sectional view;  FIG. 3B  shows a perspective view; and  FIG. 3C  shows an exploded perspective view. In  FIGS. 3A-3C  (and in the remainder of the figures), elements identical to those shown in  FIGS. 2A-2C  are identified with like reference numerals. In contrast to fitting assembly  200 , in assembly  300 , coupling nuts  230 ,  240  and pairing rings  360 ,  370  (with each of the pairing rings  360 ,  370  now consisting of only a single respective element) are permanently attached to the fittings once glands  110 ,  120 , respectively, are welded to their respective components or fluid delivery lines. The seal is created between glands  110 ,  120  and gasket  180 , all of legacy design. Nut  230  fits over pairing ring  360 , allowing rib  361  to be contained inside opening  232 . Similarly, rib  371  of pairing ring  370  is contained inside opening  242 . Fitting assembly  300  is not field-attachable but is, nevertheless, genderless and fully compatible with field-attachable fitting assembly  200 . Fitting assembly  300  is suitable for applications when components and/or gas lines are not expected to be replaced during maintenance, repair or upgrade. In another application, pairing ring  360  is suitable for fastening a blind gland to create a plug. 
         [0054]    Nipple  250  is assembled over one of the glands  110 ,  120 . Teeth  363 ,  363 ′ of pairing ring  360  fit and axially engage into notches  254 ,  254 ′ (where tooth  363 ′ is opposite tooth  363  but is not visible; and where notch  254 ′ is opposite notch  254  but is not visible). Likewise, teeth  373 ,  373 ′ of pairing ring  370  fit and axially engage into notches  253 ,  253 ′ (where tooth  373 ′ is opposite tooth  373  but is not visible). Fastening is accomplished when nuts  230 ,  240  are tightened over nipple  250 . In so tightening, nut  230  applies force to flange  364 . This force is axially transferred to flange  112 . Likewise, nut  240  applies force to flange  374 , which is axially transferred to flange  122 . Axial engagement of teeth  363 ,  363 ′ with notches  254 ,  254 ′, as well as axial engagement of teeth  373 ,  373 ′ with notches  253 ,  253 ′, prevent the transfer of any rotation from nuts  230 ,  240  to glands  110 ,  120 . Accordingly, torque free fastening is again readily accomplished. 
         [0055]    A fitting assembly  400  in accordance with a third embodiment of the invention is depicted in  FIGS. 4A-4C , where  FIG. 4A  shows a sectional view;  FIG. 4B  shows a perspective view; and  FIG. 4C  shows an exploded perspective view. In fitting assembly  400 , a seal is created between solid male-nut-and-gland combination (hereinafter “bulkhead”)  410 , gland  120  and gasket  180 , all of legacy design. Bulkhead  410  is fixated to the remainder of the fitting assembly  400  via adapter  450 . While a solid-male-nut-and-gland combination is shown, in other embodiments of the invention, adapter  450  may fixate gland  120  to other bodies such as, but not limited to, double-male unions, union elbows, union tees, union crosses, components with integral male body fittings and a variety of union adapters. Alternatively, adapter  450  is suitable to adapt fittings in accordance with the invention to legacy glands and male nut combinations. 
         [0056]    Coupling nut  240  is assembled over gland  120  by sliding over flange  122 . The opening  242  at shoulder  241  is larger than flange  122 . Therefore, nut  240  can be assembled over a previously welded gland  120 . Likewise, adapter  450  is assembled over gland  120  by sliding over flange  122 . The opening  456  and thread  454  of adapter  450  are larger than the diameter of glands  120 . After placing nut  240 , adapter  450  is tightened over the male thread of bulkhead  410 . Adapter  450  includes leak testing holes  451 ,  451 ′ (where testing hole  451 ′ is opposite testing hole  451  but is not visible), internal adapting thread  454 , male thread  452 , and two notches  453 ,  453 ′ on the edge of thread  452 . In addition, adapter  450  includes hex nut  455  for the purpose of tightening adapter  450  over male thread  414  of bulkhead  410 . When assembled, adapter  450  is tightened to reach contact between end surface  457  and step  413  of bulkhead  410 . Bulkhead  410  also includes bead  411 , hex  415 , thread  416  and nut  417 , as known in the art. 
         [0057]    Pairing ring counterparts  270 ,  270 ′ are placed over gland  120 , as depicted in the figures. 
         [0058]    Pairing ring counterparts  270 ,  270 ′ may be two identical parts. Pairing ring counterpart  270  includes ribs  271 ,  272 , tooth  273  and flange  274 . Similarly, pairing ring counterpart  270 ′ includes ribs  271 ′,  272 ′, tooth  273 ′ and flange  274 ′. Nut  240  fits over assembled pairing ring  270 + 270 ′ with combined ribs  271 + 271 ′ contained inside opening  242 . Teeth  273 ,  273 ′ of pairing ring  270 + 270 ′ fit and axially engage notches  453 ,  453 ′. Fastening is accomplished when nut  240  is tightened over thread  452  of adapter  450 . So tightened, nut  240  applies force to flange  274 + 274 ′. The force is axially transferred to flange  122 . Axial engagement of pairing ring  270 + 270 ′ via teeth  273 ,  273 ′ and notches  453 ,  453 ′ prevents the transfer of any rotation from nut  240  to gland  120 . Accordingly, torque free fastening is accomplished. When tightening nut  240 , hex  415  serves as an anchor for a second wrench. Likewise, when adapter  450  is used for torque-free fastening over legacy male nut and gland combinations, the male nut hex may be used to anchor the second wrench. 
         [0059]    Unlike legacy fittings, hex sizes of nuts  230 ,  240  and hex  455  of adapter  450  are preferably the same. For example, 7/16 inch, ¾ inch, ¾ inch and 1 1/16 inch may be utilized for face sealed fittings of tube sizes ⅛ inch, ¼ inch, ⅜ inch and ½ inch, respectively. These hex sizes match the hex sizes of legacy female nuts. The respective hex sizes of the legacy male nuts are presently ⅜ inch, ⅝ inch, ⅝ inch and 15/16 inch. 
         [0060]    The above-described embodiments have footprints that are smaller than, or comparable to legacy fittings. A comparison is made in  FIGS. 5A-5G , where:  FIG. 5A  shows a perspective view of a coupling in accordance with an illustrative embodiment of the invention;  FIG. 5B  shows a perspective view of a legacy coupling;  FIG. 5C  shows a perspective view of a plug in accordance with an illustrative embodiment of the invention;  FIG. 5D  shows a perspective view of a legacy cap;  FIG. 5E  shows a perspective view of a legacy plug;  FIG. 5F  shows a perspective view of a coupling-to-bulkhead in accordance with an illustrative embodiment of the invention;.  FIG. 5G  shows a perspective view of a legacy coupling-to-bulkhead. These figures are approximately drawn to scale. It will be noted that the coupling embodiment in  FIG. 5A  is shorter than the legacy coupling in  FIG. 5B . Likewise, the plug embodiment in  FIG. 5C  is shorter than the legacy cap and plug in  FIGS. 5D and 5E , respectively. Finally, the coupling-to-bulkhead embodiment in  FIG. 5F  is about equal in length to the legacy coupling-to-bulkhead in  FIG. 5G . 
         [0061]    The above-described embodiments, and, more generally, embodiments falling within the scope of the invention, thereby provide cost- and size-competitive, Attachable, Removable Torque-less (ARTless) fittings that, for the first time, are both torque-free and field-attachable/removable . By virtue of being field-attachable/removable, and for the benefits of torque-less manifolds, ARTless fittings may be used along with components and fluid delivery lines with glands only (i.e. without permanently attached legacy fittings). These gland-only components and fluid delivery lines, when used with legacy SN fittings, are fully compatible with legacy installations. Alternatively, when coupled with ARTless fittings, such gland-only components and fluid delivery lines facilitate a straightforward transition into torque free fittings with few or any presently known downsides. 
         [0062]    Instead of just using legacy SN fittings, legacy fittings may be upgraded to apply ARTless fittings when, for example, components or lines are replaced during maintenance or repair, or preemptively to prevent loosening in areas with a lot of vibration. In many cases, legacy nuts may simply be pushed back to clear the gland area for installation of ARTless fittings. Otherwise, tight space fittings with male nuts may be upgraded to use ARTless fittings via adapters like adapter  450  set forth above. Lastly, tight space fittings with female nuts may be upgraded by cutting the female nut off. 
         [0063]    In summary, aspects of the invention provide at least four unique key features:
       1. fittings that are symmetrical/genderless;   2. fittings that are field-attachable/removable over previously welded glands;   3. fittings that are torque free; and   4. fittings that have footprints comparable or smaller than legacy assemblies.       
 
         [0068]    In closing, it should again be emphasized that the above-described embodiments of the invention are intended to be illustrative only. Other embodiments can use different types and arrangements of elements, as well as different method steps, for implementing the described functionality. These numerous alternative embodiments within the scope of the invention will be apparent to one skilled in the art. 
         [0069]    As just one example, while the above-described embodiments describe pairing rings having teeth (i.e., projections) that axially engage notches (i.e., slots) in nipples in order to inhibit relative rotation between the pairing rings and nipples, one having ordinary skill in the art will recognize that a multiplicity of alternative designs for these engagement features may be utilized. These alternative designs will also fall within the scope of the invention.  FIG. 6 , as just one example, shows an exploded perspective view of an alternative fitting assembly  600  similar to fitting assembly  200 , but where pairing rings  605  define four pairing ring engagement features  610  in the form of shallow, curved peaks and valleys. Nipple  615 , in turn, defines four complementary nipple engagement features  620  in the form of shaped grooves. When pairing ring engagement features  610  and nipple engagement features  620  axially engage one another, relative rotation between the pairing rings  605  and the nipple  615  is constrained, allowing torque free tightening. Additional alternative embodiments falling within the scope of the invention may have the nipples define the projections and the pairing rings define the complementary slots. 
         [0070]    All the features disclosed herein may be replaced by alternative features serving the same, equivalent, or similar purposes, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.