Abstract:
A top drive system for wellbore operations, the top drive system including motor apparatus, a main shaft driven by the motor apparatus, the main shaft having a top end and a bottom end, a quill connected to the main shaft, a gear system interconnected with the quill and the motor apparatus, and a multi-seal system for sealing against the quill. This abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims, 37 C.F.R. 1.72(b).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a division of U.S. application Ser. No. 11/414,512 filed Apr. 28, 2006 (issued as U.S. Pat. No. 7,401,664 on Jul. 22, 2008). The present invention and patent application claim priority under the Patent Laws from U.S. application Ser. No. 11/414,512 filed Apr. 28, 2006 (issued as U.S. Pat. No. 7,401,664 on Jul. 22, 2008) and from U.S. application Ser. No. 11/414,514 filed Apr. 28, 2006. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention is directed to wellbore drilling top drive systems; parts thereof; multi-seals for shafts thereof; and methods of their use. 
   2. Description of Related Art 
   The prior art discloses a variety of top drive systems; for example, and not by way of limitation, the following U.S. patents present exemplary top drive systems and components thereof: U.S. Pat. Nos. 4,458,768; 4,807,890; 4,984,641; 5,433,279; 6,276,450; 4,813,493; 6,705,405; 4,800,968; 4,878,546; 4,872,577; 4,753,300; 6,007,105; 6,536,520; 6,679,333; 6,923,254—all these patents incorporated fully herein for all purposes. 
   Certain typical prior art top drive drilling systems have a derrick supporting a top drive which rotates tubulars, e.g., drill pipe. The top drive is supported from a travelling block beneath a crown block. A drawworks on a rig floor raises and lowers the top drive. The top drive moves on a guide track. 
   The prior art reveals a variety of elastomeric lip seals for sealing against rotating shafts. Such seals are frequently used to contain lubricating oil in gear boxes and other mechanical assemblies. Because of their rubbing contact with an adjacent shaft, such seals eventually wear or are damaged to the point that the lubricant or oil they are meant to contain may leak out, causing various negative consequences. Repair or replacement of such seals can entail significant time and expense, and lost production, often requiring the removal of other machine components before clear access to the seal can be obtained. 
   In the prior art are a variety of top drives which have a rotating main shaft and a thrust bearing apparatus which bears the weight of the top drive and of tubulars connected thereto. In order to prevent lubricant for the thrust bearing apparatus from flowing down, a shaft seal is used with a seal member that contacts the exterior surface of the rotating shaft. When these seals wear out, it is an expensive and time-consuming task to access them and replace them. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention, in certain aspects, provides a top drive with a shaft sealing assembly with at least two seals: at least one primary seal for use initially and at least one secondary seal that is movable into place when the primary seal becomes ineffective due to wear or damage. 
   In one particular aspect the secondary shaft seal (or seals) is carried on a movable support which is selectively movable when the primary seal becomes worn. The secondary seals can be moved into place to sealingly contact the shaft exterior without accessing the primary seals and without removal of the primary seals. Multiple sealing surfaces are provided on the shaft so that the secondary seal(s) can be moved into sealing contact with corresponding sealing surface(s). 
   The present invention discloses, in certain embodiments, a top drive system with a drive motor; a gear system coupled to the drive motor; a drive quill and/or main shaft coupled to the gear system; a top drive support system for supporting various items; and a multi-seal apparatus according to the present invention for sealing against a shaft, (e.g. the main shaft, a quill, and/or a lowest rotating element) with a primary seal (or seals) and secondary seal or at least one secondary seal that can be moved into a sealing relationship with a shaft of the system, e.g. the main shaft and/or the quill, when the primary seal is no longer effective. In one aspect, the secondary seal (or seals) is isolated within part of a lubricant bath or gear box or gear housing with lubricant therein so that the secondary seal (or seals) is in a lubricant bath and is protected from external debris and contaminants prior to its movement and sealing engagement with a seal surface. Thus, the secondary seal (or seals) is maintained in a virtually new, pristine condition until it is placed in use. 
   What follows are some of, but not all, the objects of this invention. In addition to the specific objects stated below for at least certain preferred embodiments of the invention, there are other objects and purposes which will be readily apparent to one of skill in this art who has the benefit of this invention&#39;s teachings and disclosures. It is, therefore, an object of at least certain preferred embodiments of the present invention to provide: 
   New, useful, unique, efficient, non-obvious top drive systems, multi-seal shaft sealing assemblies for such systems, and methods of their use; and 
   New, useful, unique, efficient, non-obvious top drives with a shaft sealing apparatus with a first seal (or seals) and with a second seal (or seals), the second seal(s) movable into place to seal a shaft when the first seal(s) no longer seal effectively. 
   The present invention, in certain aspects, provides a top drive system for wellbore operations, the top drive system including: a main body; a motor apparatus (e.g. one motor, or two spaced-apart motors); a main shaft extending from the main body, the main shaft having a top end and a bottom end, the main shaft having a main shaft flow bore therethrough from top to bottom through which drilling fluid is flowable; a quill connected to and around the main shaft; a gear system interconnected with the quill, the gear system driven by the motor apparatus so that driving the gear system drives the quill and thereby drives the main shaft; upper components connected to the main body above the top end of the main shaft; and the main shaft removable from the top drive system by disconnecting the main shaft from the quill, by disconnecting the upper components from the main body, and by lifting the main shaft from the quill. In certain aspects such removal of the main shaft is done without any lubricant being lost from an enclosed space containing the gear system. 
   In one aspect, the present invention discloses a method for removing a main shaft from a top drive system, the method including: disconnecting the main shaft from a quill of the top drive system, the top drive system having a main body, a motor apparatus, a main shaft extending from the main body, the main shaft having a top end and a bottom end, the main shaft having a main shaft flow bore therethrough from top to bottom through which drilling fluid is flowable, a quill connected to and around the main shaft (the quill being a generally hollow cylindrical member or shaft), a gear system interconnected with the quill, the gear system driven by the motor apparatus so that driving the gear system drives the quill and thereby drives the main shaft, the main shaft passing through the gear system, upper components connected to the main body above the top end of the main shaft, the main shaft removable from the top drive system by disconnecting the main shaft from the quill, by disconnecting the upper components from the main body and moving the upper components from above the main shaft, and by lifting the main shaft from the quill; disconnecting the upper components from the main body; and lifting the main shaft from the quill. In certain aspects of the method wherein the gear system is in lubricant within an enclosed space and the main shaft is removed without loss of lubricant from the enclosed space. 
   Accordingly, the present invention includes features and advantages which are believed to enable it to advance technology. Characteristics and advantages of the present invention described above and additional features and benefits will be readily apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments and referring to the accompanying drawings. 
   Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures, functions, and/or results achieved. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention. 
   It is, therefore, an object of at least certain preferred embodiments of the present invention to provide: 
   New, useful, unique, efficient, non-obvious top drive systems, components and parts thereof, and methods of their use; 
   Such systems with an effective main-shaft/quill connection; 
   Such systems with a removable main shaft; and 
   Such systems with two supporting bails. 
   The present invention recognizes and addresses the problems and needs in this area and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one of skill in this art who has the benefits of this invention&#39;s realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of certain preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent&#39;s object to claim this invention no matter how others may later attempt to disguise it by variations in form, changes, or additions of further improvements. 
   The Abstract that is part hereof is to enable the U.S. Patent and Trademark Office and the public generally, and scientists, engineers, researchers, and practitioners in the art who are not familiar with patent terms or legal terms of phraseology to determine quickly from a cursory inspection or review the nature and general area of the disclosure of this invention. The Abstract is neither intended to define the invention, which is done by the claims, nor is it intended to be limiting of the scope of the invention or of the claims in any way. 
   It will be understood that the various embodiments of the present invention may include one, some, or all of the disclosed, described, and/or enumerated improvements and/or technical advantages and/or elements in claims to this invention. 
   Certain aspects, certain embodiments, and certain preferable features of the invention are set out herein. Any combination of aspects or features shown in any aspect or embodiment can be used except where such aspects or features are mutually exclusive. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     A more particular description of embodiments of the invention briefly summarized above may be had by references to the embodiments which are shown in the drawings which form a part of this specification. These drawings illustrate certain preferred embodiments and are not to be used to improperly limit the scope of the invention which may have other equally effective or equivalent embodiments. 
       FIG. 1  is a schematic view of a prior art top drive drilling system. 
       FIG. 2A  is a front view of a top drive system according to the present invention. 
       FIG. 2B  is a side view of a top drive system according to the present invention. 
       FIG. 2C  is a top view of the top drive system of  FIG. 2A . 
       FIG. 2D  is a rear isometric view of  FIG. 2A . 
       FIG. 2E  is a front isometric view of  FIG. 2A . 
       FIG. 2F  is a front isometric view of part of  FIG. 2A . 
       FIG. 2G  is a side view of the top drive system of  FIG. 2A  connected to a dolly. 
       FIG. 3A  is a front cross-section view of the top drive system of  FIG. 2A . 
       FIG. 3B  is a cross-section view showing part of the top drive system of  FIG. 3A . 
       FIG. 3C  is a cross-section view showing part of the top drive system of  FIG. 3A . 
       FIG. 3D  is a cross-section view showing part of the top drive system of  FIG. 3A . 
       FIG. 4  is a perspective view of part of the top drive system of  FIG. 2A . 
       FIG. 5  is a perspective view of part of the top drive system of  FIG. 2A . 
       FIG. 6  is a perspective view of part of the top drive system of  FIG. 2A . 
       FIG. 7  is a schematic view of a prior art top drive drilling system. 
       FIG. 8  is a front view of a top drive system according to the present invention with seal apparatus according to the present invention. 
       FIG. 9  is a cross-section view of part of the system of  FIG. 2 . 
       FIG. 9A  is a cross-section view of part of a system according to the present invention. 
       FIG. 10A  is a cross-section view of a system according to the present invention. 
       FIG. 10B  is an enlargement of part of the system of  FIG. 10A . 
       FIG. 10C  is a cross-section view showing a shift in part of the system of  FIG. 10A . 
       FIG. 10D  is a cross-section view of part of a system according to the present invention. 
   

   Presently preferred embodiments of the invention are shown in the above-identified figures and described in detail below. Various aspects and features of embodiments of the invention are described below and some are set out in the dependent claims. Any combination of aspects and/or features described below or shown in the dependent claims can be used except where such aspects and/or features are mutually exclusive. It should be understood that the appended drawings and description herein are of preferred embodiments and are not intended to limit the invention or the appended claims. On the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims. In showing and describing the preferred embodiments, like or identical reference numerals are used to identify common or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness. 
   As used herein and throughout all the various portions (and headings) of this patent, the terms “invention”, “present invention” and variations thereof mean one or more embodiment, and are not intended to mean the claimed invention of any particular appended claim(s) or all of the appended claims. Accordingly, the subject or topic of each such reference is not automatically or necessarily part of, or required by, any particular claim(s) merely because of such reference. So long as they are not mutually exclusive or contradictory any aspect or feature or combination of aspects or features of any embodiment disclosed herein may be used in any other embodiment disclosed herein. 
   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates a top drive system according to the present invention which is structurally supported by a derrick  11 . The system  10  has a plurality of components including: a swivel  13 , a top drive  14  according to the present invention (any disclosed herein), a main shaft  16 , a housing  17 , a drill stem  18 /drillstring  19  and a drill bit  20 . The components are collectively suspended from a traveling block  12  that allows them to move upwardly and downwardly on rails  22  connected to the derrick  11  for guiding the vertical motion of the components. Torque generated during operations with the top drive or its components (e.g. during drilling) is transmitted through a dolly to the derrick  11 . The main shaft  16  extends through the motor housing  17  and connects to the drill stem  18 . The drill stem  18  is typically threadedly connected to one end of a series of tubular members collectively referred to as the drillstring  19 . An opposite end of the drillstring  19  is threadedly connected to a drill bit  20 . 
   During operation, a motor apparatus  15  (shown schematically) encased within the housing  17  rotates the main shaft  16  which, in turn, rotates the drill stem  18 /drillstring  19  and the drill bit  20 . Rotation of the drill bit  20  produces an earth bore  21 . Fluid pumped into the top drive system passes through the main shaft  16 , the drill stem  18 /drillstring  19 , the drill bit  20  and enters the bottom of the earth bore  21 . Cuttings removed by the drill bit  20  are cleared from the bottom of the earth bore  21  as the pumped fluid passes out of the earth bore  21  up through an annulus formed by the outer surface of the drill bit  20  and the walls of the bore  21 . 
     FIGS. 2A-2G  illustrate a top drive system  100  according to the present invention (which may be used as the top drive system  10 ,  FIG. 1 ) which has supporting bails  104  suspended from a becket  102 . Motors  120  which rotate a main shaft  160  are supported on a main body  130 . A bonnet  110  supports a gooseneck  106  and a washpipe  108  through which fluid is pumped to and through the system  100  and through a flow channel  163  through the main shaft  160 . Within the bonnet  110  are an upper packing box  115  (connected to the gooseneck  106 ) for the washpipe  108 ; and a lower packing box  117  for the washpipe  108 . 
   A main gear housing  140  encloses a bull gear  142  and other associated components as described in detail below. 
   A ring gear housing  150  encloses a ring gear  152  and associated components as described in detail below. 
   A drag chain system  170  encloses a drag chain  172  and associated components including hoses and cables as described below. This drag chain system  170  eliminates the need for a rotating head used in several prior systems and provides sufficient rotation for reorientation of the link adapter  180  and items connected thereto. 
   Bolts  112  (see  FIGS. 2E and 2F ) releasably secure the bonnet  110  to the body  130 . Removal of the bolts  112  permits removal of the bonnet  110 . Bolts  164  through a load shoulder  168  releasably secure the main shaft  160  to a quill  190  (see  FIG. 3A ). The quill  190  is a transfer member between the main shaft  160  and the bull gear  142  and transfers torque between the bull gear  142  and the main shaft  160 . The quill  190  also transfers the tension of a tubular or string load on the main shaft to the thrust bearings  191  (not to the bull gear  142 ). The transfer of torque between the main shaft  160  and the quill  190  is effected with a plurality of spaced apart expandable tapered screw-in torque transfer bushings  159  which, in certain aspects, reduce or eliminate play between the main shaft  160  and the quill  190 . An end  160   a  of the main shaft  160  (see  FIG. 2F ) is referred to as the “washpipe end.” One or more seal retainer bushings  166  (shown schematically,  FIG. 2A ) are located above the load shoulder  168 . As described in detail below, removal of the bonnet  110  and bolts through the load shoulder  168  securing the main shaft  160  to a quill  190 , permits removal of the main shaft  160  from the system  100 . Upper quill bearings  144  are above a portion of the quill  190 . 
   As shown in  FIG. 2G , the system  100  is movable on a mast or part of a derrick (like the derrick  11  and on its rails  22 ) by connection to a movable apparatus like the dolly  134  ( FIG. 2G ). Ends of links  133  are pivotably connected to arms  131 ,  132  of the body  130 . The other ends of the links  133  are pivotably connected to the dolly  134 . This structure permits the top drive and associated components to be moved up and down, and toward and away from a well centerline, as shown by the structure in dotted line (toward the derrick when drill pipe is connected/disconnected while tripping; and to the well center during drilling). Known apparatuses and structures are used to move the links  133  and to move the dolly  134 . 
   Upper parts of the bails  104  extend over and are supported by arms  103  of the becket  102 . Each bail  104  has two spaced-apart lower ends  105  pivotably connected by pins  107  to the body  130 . Such a use of two bails distributes the support load on the main body and provides a four-point support for this load, economically reducing bending moments on the main body. 
   The quill  190  (see  FIG. 3A ) rests on main thrust bearings  191  which support the quill  190 , the main shaft  160 , and whatever is connected to the main shaft  160  (including whatever load is borne by the main shaft  190  during operations, e.g. drilling loads and tripping loads). The body  130  houses the main thrust bearings  191  and contains lubricant for the main thrust bearings  191 . An annular passage  145  (see  FIG. 3C ) provides a flow path for lubricant from the gear housing  140  to the thrust bearings. 
   Shafts  122  of the motors  120  drive couplings  123  rotatably mounted in the body  130  which drive pinions  124  in the main gear housing  140 . The drive pinions  124  drive a bull gear  142  which, connected to the quill  190  with connectors  192  (e.g., but not limited to, taper lock connectors in which turning bolts  193  ((see  FIG. 3D )) tightens the connectors screwing together parts  194  which push the parts  194  against the quill  190  and which push out wedges  195  against the bull gear  142  securing the bull gear  142  to the quill  190 ), drives the quill  190  and thus the main shaft  160  which is connected to the quill  190 . Radial bearings  197  support the bull gear  142 . 
   The bull gear  142  is within a lower portion  146  of the gear housing  140  which holds lubricant for the bull gear  142  and is sealed with seal apparatus  148  so that the lubricant does not flow out and down from the gear housing  140 . Any suitable known rotary seal  148  may be used or, as in one particular aspect the seal apparatus  148  is like the seal apparatus disclosed in co-owned U.S. application Ser. No. 11/414,514 filed Apr. 28, 2006 entitled “Multi-Seal For Top Drive Shaft”, which is incorporated fully herein for all purposes. With such a seal apparatus, which has rotatable bolts  149 , when a first seal structure no longer seals effectively, the bolts  149  are rotated and a second seal structure is shifted into place to effect a good seal. Within the gear housing  140 , the bull gear  142  and the drive pinions  124  sit in lubricating oil, eliminating the need for spray nozzles, distribution pumps, and flow or pressure sensors employed in various prior systems. 
   The ring gear housing  150  which houses the ring gear  152  also has movably mounted therein two sector gears  154  each movable by a corresponding hydraulic cylinder apparatus  156  to lock the ring gear  152  (see, e.g.,  FIGS. 3B and 4 ). With the ring gear  152  unlocked (with the sector gears  154  backed off from engagement with the ring gear  152 ), items below the ring gear housing  150  (e.g. a pipe handler on the link adapter) can rotate. The ring gear  152  can be locked by the sector gears  154  to act as a backup to react torque while drill pipe connections are being made to the drillstring. The ring gear  152  is locked when a pipe handler is held without rotation (e.g. when making a connection of a drill pipe joint to a drillstring). An hydraulic motor  158  (shown schematically), via gearing  159 , turns the ring gear to, in turn, rotate the link adapter  180  and whatever is suspended from it; i.e., in certain aspects to permit the movement of a supported tubular to and from a storage area and/or to change the orientation of a suspended elevator, e.g. so that the elevator&#39;s opening throat is facing in a desired direction. Typical rig control systems are used to control the motor  158  and the apparatuses  156  and typical rig power systems provide power for them. 
   In a variety of prior top drive systems a rotating head with a plurality of passageways therethrough is used between some upper and lower components of the system to convey hydraulic and pneumatic power used to control system components beneath the rotating head. Such a rotating head typically rotates through 360 degrees infinitely. Such a rotating head may, according to certain aspects of the present invention, be used with system according to the present invention; but, in other aspects, a drag chain system  170  is used below the ring gear housing  150  and above the link adapter  180  to convey fluids and signals to components below the ring gear housing  150  (see, e.g.,  FIGS. 3B and 5 ). The drag chain system  170  does not permit infinite 360 degree rotation, but it does allow a sufficient range of motion in a first direction or in a second opposite direction to accomplish all the functions to be achieved by system components suspended from the link adapter  180  (e.g. an elevator and/or a pipe handler), in one aspect with a range of rotative motion of about three-quarters of a turn total, 270 degrees. 
   Optionally, instead of a typical rotating head or a drag chain system according to the present invention, a variety of known signal/fluid conveying apparatuses may be used with systems according to the present invention; e.g., but not limited to, wireless systems or electric slip ring systems, in combination with simplified fluid slip ring systems. 
   Enclosed within a system housing  171  is a rotatable spool  174  which is rotated by a chain  176  made up of a plurality of interconnected chain sections  177 . In one position the chain  176  is wound around the periphery of the spool  174 . As the chain  176  unwinds from the spool  174  as the spool  174  is rotated by the hydraulic motor  158  rotating the ring gear  152 , the unwinding chain portion feeds into the housing  171  in which it resides until the spool  174  is rotated in the opposite direction and the chain  176  is again wound onto the spool  174 . 
   As the chain  176  winds and unwinds, hoses and cables  178  wind and unwind with the chain  176 . Sections  177  of the chain  176  have openings  179  through which pass the hoses and cables  178  so that the chain  176  supports the hoses and cables  178  and maintains them in an organized, untangled arrangement with respect to the spool  174 , both at rest and when the spool  174  is being rotated. One end of the chain  176  is secured to the spool  174 . The hoses and cables  178  project out from the spool  174  and extend downwardly to components of the system (one such item illustrated in  FIG. 3B  as hose or cable  178   a ). 
   Fasteners  183  secure the spool  174  to the link adapter  180 . The combination of the spool  174  and ring gear  152  (and, therefore, the link adapter  180  and whatever is suspended from it) is permitted some limited degree of vertical movement due to the dimensions of the ring gear housing  150  and the ring gear  152 —the ring gear  152  can move up and down within the housing  150 , e.g., in one particular aspect, about 0.25 inch, and the link adapter  180  can move a limited distance (a load ring/link adapter gap  181 ) with respect to a load ring  184  as described in detail below. 
   A spring cartridge apparatus  182  with a top ring  182   a  and a bottom ring  182   b  has plurality of spaced-apart springs  188  which urge the two rings apart (see, e.g.,  FIGS. 3B and 6 ). The spring cartridge  182  is within the link adapter  180  and surrounds a stem  186  that is secured with bolts  185  to the gear housing  140 . A ring  189  projecting into the wall of the stem  186  projects outwardly therefrom and supports the spring cartridge apparatus  182 . The stem  186  acts as a guide for movement of the link adapter  180 , maintains centering of the link adapter  180 , and supports the link adapter  180 , via the spring cartridge apparatus  182 , during certain operations, e.g., drilling. 
   The springs  188  within the spring cartridge  182  push upwardly on the spool  174 , lifting the spool  174  and maintain the gap  181  between the link adapter  180  and the load ring  184  (secured to the main shaft with a split ring  167 ); so that, e.g., during drilling, the main shaft  160  can rotate independently of the link adapter  180  and whatever is connected thereto. The springs  188  can support the weight of the link adapter, the links (or bails) connected to the link adapter, and an elevator apparatus. When tubular(s) are engaged by the elevator apparatus, the springs  188  collapse, the link adapter  180  moves down to rest on the load ring  184 , the load then passes to and through the main shaft  160 . Thus, the link adapter  180  (and whatever is connected thereto) can be maintained stationary while drilling. When a sufficient load is placed on the link adapter  180  (e.g. when hoisting the drillstring with an elevator or running casing), the forces of the springs  188  are overcome, the link adapter  180  is moved down to close the gap  181 , and the link adapter  180  rests on the load ring  184  so that the link adapter load is transferred to the load ring  184 . 
   Thus, certain systems according to the present invention provide two ways to transfer the load of tubular(s) supported by the system: first, the load of tubulars connected to the main shaft passes from the main shaft, to the quill, to the main thrust bearings, to the main body, to the bails, to the becket, to the hook and/or block, and to the derrick; and, secondly, when a string, e.g. a drillstring, is being raised or lowered without being rotated (e.g. when tripping pipe or lowering casing) the tubular load passes from a tubular support (e.g. an elevator) to the link adapter, to the load ring, to the split ring  167  and thence to the main shaft, and thence, as in the first load transfer path described above, to the derrick. 
   Drilling loads (the load of the drillstring, bit, etc.) passes through a threaded connection at the end of the main shaft  160  to the main shaft  160 . Tripping loads (the load, e.g., of tubular(s) being hauled and manipulated) pass through the link adapter  180  and through the load ring  161 , not through the threaded connection of the main shaft and not through any threaded connection so that threaded connections of the top drive are isolated from tripping loads. 
   In certain aspects as compared to certain prior system, the spring cartridge  182  with the plurality of springs  188  is a simpler, passive apparatus which requires relatively less maintenance and can result in reduced system downtime. 
   The main shaft can be removed from the system  100 , to repair the main shaft or to replace the main shaft, without disturbing and without removing the gear case and gearing of the system. To remove the main shaft, the bonnet, gooseneck, washpipe, and associated packing are removed, preferably together as a unit. The bolts  164  that hold the main shaft down are removed. The split ring  167  is removed. The main shaft is disconnected from the quill. After the load ring and the split ring are removed, the main shaft is then removed from the system. During this removal process, all the system gearing and seals have remained in place and no lubricant has been removed or drained. 
   The present invention, therefore, provides in some, but not in necessarily all, embodiments a top drive system for wellbore operations, the top drive system including: a main body; a motor apparatus; a main shaft extending from the main body, the main shaft having a top end and a bottom end, the main shaft having a main shaft flow bore therethrough from top to bottom through which drilling fluid is flowable; a quill connected to and around the main shaft; a gear system interconnected with the quill, the gear system driven by the motor apparatus so that driving the gear system drives the quill and thereby drives the main shaft, the main shaft passing through the gear system; upper components connected to the main body above the top end of the main shaft; and the main shaft removable from the top drive system by disconnecting the main shaft from the quill, by disconnecting the upper components from the main body and moving the upper components from above the main shaft, and by lifting the main shaft from the quill. 
   The present invention, therefore, provides in some, but not in necessarily all, embodiments a top drive system for wellbore operations, the top drive system including: a main body; a motor apparatus; a main shaft extending from the main body, the main shaft having a top end and a bottom end, the main shaft having a main shaft flow bore therethrough from top to bottom through which drilling fluid is flowable; a quill connected to and around the main shaft; a gear system interconnected with the quill, the gear system driven by the motor apparatus so that driving the gear system drives the quill and thereby drives the main shaft, the main shaft passing through the gear system; a link adapter having a central bore therethrough, the main shaft passing through the central bore of the link adapter; a load ring connected to the main shaft; the link adapter positioned above the load ring; upper components connected to the main body above the top end of the main shaft; and the main shaft removable from the top drive system by disconnecting the main shaft from the quill, by disconnecting the load ring from the main shaft, by disconnecting the upper components from the main body, and by lifting the main shaft from the quill. Such a system may have one or some, in any possible combination, of the following: wherein the upper components include a bonnet connected to the main body, a washpipe in fluid communication with the top end of the main shaft, a gooseneck in fluid communication with the washpipe, and the upper components are movable from above the main shaft; wherein the gear system is in lubricant within an enclosed space and the main shaft is removable without lubricant draining from the enclosed space; wherein the quill is connected to the main shaft with first connectors through which tension on the main shaft is transferred to the quill, and with second connectors through which torque is transferred from the quill to the main shaft; two spaced-apart bails, each bail with two spaced-apart lower ends, and each lower end connected to the main body thereby providing a four-point connection between the bails and the main body for the bails to support the top drive system; a spring cartridge apparatus having a top ring, a bottom ring, a plurality of springs positioned between and urging apart the top ring and the bottom ring, the spring cartridge apparatus located within the link adapter and urging the link adapter away from the load ring so that a gap is maintained between the link adapter and the load ring until sufficient weight is supported by the link adapter to overcome the urging of the springs; a drag chain system for allowing rotation of the link adapter, the drag chain system including a housing, a spool rotatably mounted within the housing, a chain with a first end and a second end, the first end connected to the spool, the second end connected to the link adapter, the chain able to be wound onto and unwound from the spool, unwound chain received within the housing, a plurality of conduits carried by the chain, the conduits for transmitting signal or power fluids between the drag chain system and items below the link adapter, and a rotation system connected to the spool for rotating the spool and the link adapter; wherein the rotation system includes a ring gear housing, a ring gear rotatably mounted in the ring gear housing, a gearing system interconnected with the ring gear, a motor for driving the gearing system to rotate the ring gear to rotate the spool and the link adapter, winding and unwinding the chain as the link adapter is rotated; and/or wherein the rotation system includes locking apparatus for selectively preventing rotation of the ring gear thereby selectively preventing rotation of the link adapter. 
     FIG. 7  shows a typical prior art drilling system with a derrick DK supporting a top drive TD which rotates drill pipe DP. The top drive is supported from a travelling block TB beneath a crown block CB. A drawworks, DS, on a rig floor RF raises and lowers the top drive. The top drive moves on a guide track GT. 
     FIG. 8  shows a system S according to the present invention with a top drive  201  with a drive motor  202 ; a gear system  203  coupled to the top drive  201  with a bearing support  204  and support links  204   a ; a washpipe apparatus  209 ; a gooseneck  214 ; an elevator load ring  205 ; a mud saver system  211 ; a lower internal blowout preventer  206 ; a saver sub  207 ; a top drive main shaft  212 ; a pipe gripper  208  with support  208   a ; and a seal system  210  (shown schematically) according to the present invention. 
     FIG. 9  illustrates components for a system  210  e.g., as in  FIG. 8  (like numerals indicate like parts). One embodiment of the seal system  210  for a main shaft  212  of the top drive system S has a primary seal  214  on a support  216  of a seal carrier  220  that seals against a lower exterior surface  218   a  of a seal ring  218 . The seal carrier  220  is bolted with bolts  213  to a support member  224  which is connected adjacent structure of the top drive. Fluid, (e.g. oil, lubricant in a gear box or housing  226 ) is prevented from going past this seal  214 . Optionally, a split ring  230  with a connecting bolt  231  (or bolts) hold the seal ring  218  on the shaft  212 ; or the seal ring is secured directly to the shaft. Optionally, the seal ring itself can be fixed or adhered to the main shaft with an interference fit, suitable fasteners, connectors, and/or adhesives, with or without the split ring  230 . Seals  223   a  and  223   b  seal a member- 224 /carrier- 220  interface. 
   The support  216  is bolted to (or formed integrally of) a body  242 . The bolt  213  secures the support  216  to the support member  224 . The support  216  and body  242  are movable up and down by rotating the bolt  213  (multiple bolts may be used). 
   Part of a typical lower radial bearing apparatus  250  is above the support member  224 . A main thrust bearing apparatus  252  is located within the box or housing  226  (shown schematically in dotted lines). The lubricating oil for these bearings is maintained on these bearings without leaking past the seal system  210 . 
   A secondary seal  234  is secured to the body  242  (e.g. by an interference fit, fastener(s), and/or adhesives). The secondary seal  234  does not initially contact the surface  218   a  since it is smaller in diameter than the primary seal  214 . In order to utilize the secondary seal  234  to seal against the seal ring  218 , the bolt  213  (or bolts) is turned to raise the support  216  and the body  242  so that the secondary seal  236  is moved adjacent a secondary surface  218   b  of the seal ring  218 . The secondary surface  218   b  has a larger diameter than the surface  218   a  so that when the secondary seal  235  is raised, it sealingly contacts the secondary surface  218   b . Optionally, additional seal(s) like the seal  234  are positioned above the seal  234  and the seal ring  218  has additional sealing surfaces for the additional seal(s) to sealing contact when the seal(s) are raised into seating position. Each additional seal surface (higher than the preceding seal surface) has a larger diameter than the preceding (lower) seal surface and each additional seal (higher than the preceding seal) has a smaller diameter than the preceding (lower) seal. It is to be understood that  FIG. 9  illustrates one half of the seal system  210  (on the left side in  FIG. 9 ) and that ring, seals, etc. on the right side (not shown) mirror the left side. The seal  214  inhibits the flow of debris and contaminants to the seal  234 . In one aspect the seal  234  is within the space of the housing  226  and is bathed in lubricant, further protecting the seal  234  until it is used. 
   It is within the scope of the present invention to provide a seal ring  218  with two (as shown) surfaces (one a stepped surface) or with three, four or more such steps and with three, four, or more corresponding additional secondary seals. 
     FIGS. 10A-10C  show a seal system  300  according to the present invention for sealing against a quill  352  (shown partially) of a top drive system. The quill  352  is connected to a top drive main shaft  362  (connection not shown) and the quill  352  rotates with the main shaft  362 . The quill  352  has an exterior surface  354  and a primary seal  302  of the seal system  300  sealing contacts this exterior surface  354 . 
   The quill  352  has a circumferential groove  356  and a secondary seal  304 , as shown in  FIGS. 10A and 10B , is adjacent the groove  356  and is not yet in contact with the quill  352 . The seals  302 ,  304  are circumferential seals that extend around the circumference of the quill  352 . A seal  316  seals a carrier- 310 /member- 315  interface. 
   The seals  302  and  304  are secured to a seal carrier  310 . Rotatable bolts  312  (or a single bolt) rotatably connected to the seal carrier  310  project through a member  314  (e.g., but not limited to a stem associated with a lower link adapter). Rotating the bolts  312  moves the seal carrier  310  down with respect to a member  315 , as shown in  FIG. 4C , to move the secondary seal  304  down past the groove  356  until the seal  304  sealingly contacts the exterior surface of the quill  352 . Optionally and/or alternatively, the bolt(s)  312  are rotatable to raise the seal carrier  310  to move the seal  304  up into sealing contact with the quill  352  (with sufficient space provided above the seal carrier to accomplish this). 
   Gearing  360  of the top drive, driven by a top drive motor (not shown) is connected with and drives the quill  352  (which drives the main shaft  362 ). Lubricant for the gearing  360  is prevented from flowing down by the seal system  300 . 
   Optionally and/or alternatively, the groove  356  is on the main shaft and the seal system is located so that seal system&#39;s seals seal against the main shaft (with or without a quill). 
   Optionally and/or alternatively, a seal carrier according to the present invention may have a threaded outside diameter that threadedly mates with a corresponding threaded part adjacent a rotating shaft so that the seal carrier may be moved up or down with respect to the shaft by rotating the seal carrier and moving it up or down as the seal carrier&#39;s threads engage the adjacent part&#39;s threads. 
   As shown in  FIG. 9A , a system  210   a  (like the system  10 ,  FIG. 3 ; like numerals indicate like parts) has a seal carrier  220   a  with a threaded side  220   b  which threadedly mates with threads  224   b  of a support member  224   a . Rotating the seal carrier  220   a  moves the seal  234  up to sealingly contact the surface  218   b.    
   As shown in  FIG. 10D , a system  300   a  (like the system  300 ,  FIG. 10A ; like numerals indicate like parts) has a seal carrier  310   a  with a threaded side  310   b  that threadedly mates with threads  315   b  of a member  315   a . Rotating the seal carrier  310   a  moves the seals  302 ,  304  with respect to the quill  352  and its groove  356 . Rotating the seal carrier  310   a  in either direction sufficiently will move the seal  304  into sealing contact with the quill  352 . 
   The present invention, therefore, provides in some, but not in necessarily all, embodiments a top drive system for wellbore operations, the top drive system including: motor apparatus; a main shaft having a top end and a bottom end; a gear system driven by the motor apparatus and interconnected with the main shaft for driving the main shaft; a sealing assembly adjacent the main shaft for sealing against the main shaft, the sealing assembly having a seal carrier adjacent the main shaft, a primary seal member on the seal carrier, the primary seal member sealingly contacting the main shaft, at least one secondary seal on the seal carrier, and the seal carrier selectively movable to move the at least one secondary seal into sealing contact with the main shaft. Such a system may have one or some, in any possible combination, of the following: wherein the main shaft has a seal ring connected to the main shaft, the seal ring having a first portion with a first diameter and a second portion with a second diameter the first diameter smaller than the second diameter, the primary seal member is sealing contact with the first portion of the seal ring, the secondary seal member adjacent the second portion of the seal ring, and the seal carrier movable to move the secondary seal into sealing contact with the second portion of the seal ring; a retainer releasably securable to the main shaft to hold the seal ring in place; wherein the seal carrier is releasably secured to part of the top drive adjacent the main shaft with at least one rotatable bolt threadedly mated with the part of the top drive so that rotating the at least one bolt moves the at least one secondary seal into sealing contact with the main shaft; and/or wherein the seal carrier has a carrier threaded surface and part of the top drive system adjacent the main shaft has a part threaded surface, the seal carrier rotatable with the carrier threaded surface threadedly engaging the part threaded surface so that the seal carrier is movable to move the at least one secondary seal into sealing contact with the main shaft. 
   The present invention, therefore, provides in some, but not in necessarily all, embodiments a top drive system for wellbore operations, the top drive system including: motor apparatus; a main shaft having a top end and a bottom end; a gear system driven by the motor apparatus and interconnected with the main shaft for driving the main shaft; a sealing assembly adjacent the main shaft for sealing against the main shaft, the sealing assembly having a seal carrier adjacent the main shaft, a primary seal member on the seal carrier, the primary seal member sealingly contacting the main shaft, at least one secondary seal on the seal carrier, and the seal carrier selectively movable to move the at least one secondary seal into sealing contact with the main shaft. Such a system may have one or some, in any possible combination, of the following: wherein the main shaft has a seal ring connected to the main shaft, the seal ring having a first portion with a first diameter and a second portion with a second diameter the first diameter smaller than the second diameter, the primary seal member is sealing contact with the first portion of the seal ring, the secondary seal member adjacent the second portion of the seal ring, and the seal carrier movable to move the secondary seal into sealing contact with the second portion of the seal ring; a retainer releasably securable to the main shaft to hold the seal ring in place; wherein the seal carrier is releasably secured to part of the top drive adjacent the main shaft with at least one rotatable bolt threadedly mated with the part of the top drive so that rotating the at least one bolt moves the at least one secondary seal into sealing contact with the main shaft; and/or wherein the seal carrier has a carrier threaded surface and part of the top drive system adjacent the main shaft has a portion with a mating, threaded surface, the seal carrier rotatable with the carrier threaded surface threadedly engaging the part&#39;s mating threaded surface so that the seal carrier is movable to move the at least one secondary seal into sealing contact with the main shaft. 
   The present invention, therefore, provides in some, but not in necessarily all, embodiments a seal system for sealing against a shaft, the seal system including: a first surface area on a shaft, the shaft being generally cylindrical; at least one second surface area on the shaft; the first surface area and the at least one second surface area on the shaft extending circumferentially around the shaft; the first surface area having a diameter different from a diameter of the at least one second surface area; a seal carrier; a first seal on the seal carrier, the first seal in sealing contact with the first surface area of the shaft; at least one second seal on the seal carrier, the at least one second seal initially not in contact with the shaft; and the seal carrier movable to move the at least one second seal into sealing contact with the at least one second surface area. Such a system may have one or some, in any possible combination, of the following: the first surface area has a diameter smaller than the at least one second surface area; the first surface area has a diameter equal to the second surface area, the shaft has a circumferential groove therearound and the at least one second seal is initially adjacent and not in contact with the groove, the seal carrier movable to move the at least one second seal into sealing contact with the second surface area; wherein the seal carrier is releasably secured to a part of a mechanical system including the shaft with at least one rotatable bolt threadedly mated with the part so that rotating the at least one bolt moves the at least one secondary seal into sealing contact with the shaft; and/or wherein the seal carrier has a carrier threaded surface and a part of a mechanical system adjacent the shaft has a part threaded surface, the seal carrier rotatable with the carrier threaded surface threadedly engaging the part threaded surface so that the seal carrier is movable to move the at least one secondary seal into sealing contact with the shaft. 
   The present invention, therefore, provides in some, but not in necessarily all, embodiments a method for sealing against a shaft of a mechanical system, the mechanical system including motor apparatus, a shaft having a top end and a bottom end, a gear system driven by the motor apparatus and interconnected with the shaft for driving the shaft, a sealing assembly adjacent the shaft for sealing against the shaft, the sealing assembly having a seal carrier adjacent the shaft, a primary seal member on the seal carrier, the primary seal member for sealingly contacting the shaft, a second seal on the seal carrier, the second seal not initially in contact with the shaft, and the seal carrier selectively movable to move the second seal into sealing contact with the shaft, the method including: locating the seal carrier so that the primary seal sealingly contacts the shaft, and moving the seal carrier so that the second seal sealingly contacts the shaft. Such a method may have one or some, in any possible combination, of the following: wherein the shaft is a main shaft driven by the motor; wherein the shaft is a quill of a top drive system positioned around and connected to a main shaft of the top drive system, the gear system connected with the quill to drive the quill to drive the main shaft; wherein the mechanical system is a top drive system for wellbore operations; and wherein the shaft is a main shaft driven by the motor. 
   In conclusion, therefore, it is seen that the present invention and the embodiments disclosed herein and those covered by the appended claims are well adapted to carry out the objectives and obtain the ends set forth. Certain changes can be made in the subject matter without departing from the spirit and the scope of this invention. It is realized that changes are possible within the scope of this invention and it is further intended that each element or step recited in any of the following claims is to be understood as referring to the step literally and/or to all equivalent elements or steps. The following claims are intended to cover the invention as broadly as legally possible in whatever form it may be utilized. The invention claimed herein is new and novel in accordance with 35 U.S.C. §102 and satisfies the conditions for patentability in §102. The invention claimed herein is not obvious in accordance with 35 U.S.C. §103 and satisfies the conditions for patentability in §103. This specification and the claims that follow are in accordance with all of the requirements of 35 U.S.C. §112. The inventors may rely on the Doctrine of Equivalents to determine and assess the scope of their invention and of the claims that follow as they may pertain to apparatus not materially departing from, but outside of, the literal scope of the invention as set forth in the following claims. All patents and applications identified herein are incorporated fully herein for all purposes. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph  6  for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function. In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.