Abstract:
A drive apparatus for a drill stem, in particular for de-coking systems, has a feeder ( 4 ) connected to a water supply ( 8 ) via a first interface ( 6 ) and connected to a drill stem ( 12 ) via a second interface ( 10 ), as well as a drive ( 14 ) and a gearbox ( 16 ) for rotatably driving said feeder ( 4 ) and said drill stem ( 6 ), characterized in that said feeder ( 4 ) has a first section ( 20 ) connected to the water supply ( 8 ) and a second section ( 40 ) connected to the drill stern ( 12 ) and the first ( 20 ) and second ( 40 ) sections are releasably connected to each other.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a drive apparatus for a drill stem, in particular for de-coking systems. 
         [0002]    In oil refineries, the last otherwise unusable fraction of the crude oil is transformed into coke. This transformation is performed by feeding this fraction into drums which are filled with coke as the operation proceeds. Once the maximum filling level of the drums has been reached, the coke is cut out from the drums. 
         [0003]    This so-called “de-coking” is usually carried out using high-pressure water jets which disintegrate the coke and wash it out of the drums. The tool for generating these high-pressure water jets is inserted into the drums from the top using a drilling rig. The subject of the present invention is in particular the construction of the drill stem drive and therefore the transition from the water supply to the drill stem. 
         [0004]    In prior art generic systems, this transition from the water supply to the drill stem is formed as an integral feeder. The first, top end is connected to a water supply via a flange. The second, bottom end of the feeder is connected to the flange of the drill stem. This second, bottom end is usually supported in thrust and journal bearings in order to ensure smooth rotation. At the second end of the feeder there is also a gear box which causes the drill stem to rotate in operation. The water supply, the feeder and the drill stem are connected in an aligned and liquid-tight fashion so that a tool attached to the free end of the drill stem for de-coking is supplied with the requisite water in an operating state. 
         [0005]    In the area of the feeder, the sealing rings, which are positioned at the transition between stationary and rotating structural elements, are particularly subject to wear and tear and must be replaced at regular intervals. Wear and tear shows at the first end of the feeder, where a fluid-tight connection is to be established to the water supply and at the same time fixed and rotating parts of the drive apparatus are adjacent to each other. In prior art systems, the sealing rings acting as sealing elements at the transition between fixed and rotating structural parts must be replaced in the steel frame of the de-coking system while the drill stem drive is in place, which contributes to maintenance overhead. 
       SUMMARY OF THE INVENTION 
       [0006]    It is therefore an object of the present invention to simplify the structure of such a drive apparatus for a drill stem and to make the replacement of the sealing elements more maintenance friendly and more economical. 
         [0007]    This object is achieved by a drive apparatus according to claim  1 . A drive apparatus with a feeder comprising first and second sections, enables faster and error-free replacement. A second section, which extends from the drill stem and is virtually wear-free, remains in a state securely bolted to the gearbox and the drill stem. Malfunctions resulting from repeated interference with these structural elements are thus reliably ruled out. 
         [0008]    The first section of the feeder may be released by simple means and is otherwise connected to the second section in a safe and liquid-tight manner. The connection, in particular the sealing elements between the first section of the feeder and the water supply, which is subject to wear and tear, does not have to be replaced in order to use the drilling apparatus of the present invention. The type of connection between the water supply and the feeder does not necessarily have to be changed. All that remains to be done is to replace a compact and complete assembly. 
         [0009]    The advantage of replacing a compact, complete assembly is that the sealing elements no longer have to be replaced while the drill stem drive is in place and under spacially difficult conditions. The assembly, comprising the first section of the feeder of the drill stem drive with the worn out sealing rings, may now be cleaned and repaired at leisure and provided with new sealing rings. The repaired assembly is then ready to be reused in a drill stem drive. Since the attachment to the second section is via a relatively simple connection, the drill apparatus of the present invention can be repaired in much shorter time. 
         [0010]    The drill apparatus is not weakened by partitioning the feeder as long as the type of connection between the two sections takes the loads into account that have to be absorbed. In particular it is preferred to design this releasable connection between the two sections as a clamp, bolt or flange. A clamp connection preferably provides a means for clamping, connecting the first and the second section of the feeder. In the same way, a bolting means according to a preferred embodiment provides a means for bolting which connect the first and second sections of the feeder. Such connections are known as such, and a person skilled in the art will be well acquainted with the corresponding approaches. 
         [0011]    With drilling apparatus of the prior art, the gear box causing the feeder and the drill stem to rotate was usually individually manufactured because of the predominant opinion that this was a special application which required special measures when designing and adapting the gearbox. The gear boxes of the prior art are enclosed by a housing filled with oil. 
         [0012]    It is to be seen as an autonomous inventive step that the drill apparatus of the present invention is structurally simplified by the consistent use of standardized structural parts that are available from a supplier catalogue. By using standardized parts, the operational safety of the apparatus is usually also increased, since these parts have already been tested in numerous other applications. Additionally, the cost of the drill apparatus is advantageously reduced. 
         [0013]    It is therefore considered an inventive step to suggest a gear box for drilling apparatuses, in particular for use in de-coking systems, which is formed as an open, greased gear-rim drive. Surprisingly, such gear boxes, which are known for swivelling applications, have proven to be sufficiently robust for the use in drilling apparatuses. The maintenance and repair of such gear boxes is particularly simple and quick. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    One of the possible embodiments of the invention is described in more detail with reference to  FIG. 1 , in which: 
           [0015]      FIG. 1  is a longitudinal sectional view of a drive apparatus of a drill stem according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Apparatus  2  of the present invention for driving the drill stem comprises a feeder  4  with a first connection  6  to a water supply  8  and a second connection  10  to a drill stem  12 , as well as a drive  14  for a gear box  16  causing feeder  4  and drill stem  12  to rotate in operation. 
         [0017]    Water supply  8 , only schematically shown in the FIGURE, is usually formed as a goose-neck. It ends in a flange  18  at which a first section  20  of the feeder  4  abuts. The connection to the first section  20  is provided by a first interface  6 . Interface  6  has a contacting surface  22  contacting flange  18 . In order to make the connection liquid tight, a standardized seal  24  is provided between interface  6  and flange  18 . 
         [0018]    Interface  6  is releasably connected to flange  18  by bolts  26 , only schematically shown in the FIGURE. Interface  6  embraces sealing packings  32  surrounding the first section  20 . To counteract the water pressure in feeder  4 , packings  32  are releasably secured by bolts  28  at the bottom through a support  30 . In order to ensure effective sealing between water supply  8 , stationary interface  6  and the first section  20  of feeder  4 , which rotates in operation, a plurality of sealing packings  32  completely fill an annular cavity  34  between interface  6  and first section  20 . 
         [0019]    The first section  20  is connected to the second section  40  via a clamp  36  engaging the first section via contacting surfaces  38 ,  38   a . A sealing  42  is inserted between the two sections  20 ,  40 . Clamp  36  contacts the second section  40  via contacting surfaces  44 ,  44   a . Sections  20 ,  40  are formed to be planar on the surfaces  46 ,  46   a  facing each other, and on their outer circumferences they only have the above-described contacting surfaces  38 ,  38   a  and  44 ,  44   a . The manufacture, assembly and disassembly of the first section  20  thus require little cost and time. 
         [0020]    Once the packings  32  are worn out, they have to be replaced. In order for the replacement to be simple, safe and quick, an assembly comprising first section  20 , packings  32  and interface  6  is taken out of drive apparatus  2  after clamp  36  and interface  6  have been released. An identical assembly provided with new packings  32  is inserted in drive apparatus  2 . Clamp  36  and interface  6  are then closed again in a sealing relationship. Drive apparatus  2  may be put back in operation after only a short standstill. 
         [0021]    The second section  40  is formed to be integral with interface  10 , to which gear  16  is attached. A further element of interface  10  is flange  48 , to which drill stem  12  is bolted. Bolts  50  are only schematically shown. The circumferential surface  52  of interface  10 , i.e. the end of second section  40  facing drill stem  12  is formed as an outer gear rim. A gear  54  is in mesh with this outer gear rim  52 , wherein gear  54  is caused by drive  14  to rotate in operation. 
         [0022]    Drive  14  comprises a motor  56 . In the present case, this is an electric motor. However, hydraulic or pneumatic motors could also be used. A gearbox  58  is connected down-stream of motor  56 , wherein the output gear of gearbox  58  is in mesh with gear  54 . Outside gear rim  52 , gear  54  and output gear  60  form gearbox  16 . Outside gear rim  52  and gears  54  and  60  are formed to be an open, greased gearbox  16 . A closed gearbox housing is not necessary, and this is why the need for large quantities of gearbox oil is eliminated. The approach of using an open gearbox  16  of the present invention is particularly simple and easy to maintain. It has the additional advantage that outside gear rim  52  does not have to be specially manufactured for each new feeder  4 , which must be regularly replaced when worn out. 
         [0023]    The parts with reference numerals  54 ,  56 ,  58 , and  60  are all standardized components as offered in suppliers&#39; catalogues and tested in numerous other applications. 
         [0024]    A thrust bearing  62  and a journal bearing  64  are also positioned in the area of interface  10 , i.e. at the end facing the second section  40 . These bearings  62  and  64  support the loads applied by gearbox  16  and drilling apparatus  2  as well as by the drilling apparatus&#39;s own weight and ensure smooth rotation of drilling apparatus  2  when in an operative state. 
         [0025]    To cover feeder  4  rotating in an operating state, drill apparatus  2  has a lantern  66 , representing the connection between water supply  8  and gearbox unit  16 . The drill stem drive is mounted and held by lantern  66 . Lantern  66  is simple to mount and to remove, since it must always be removed when first section  20  of feeder  4  is to be replaced. It has an access window in the area of packings  32  so that complete safety is ensured for operating personnel if the state of packings  32 , and therefore the degree of wear and tear, has to be checked, which are sometimes in the immediate vicinity of rotating, high-pressure parts. 
         [0026]    In the context of the present invention, repeated reference has been made to the use of seals. It is quite obvious that a drilling apparatus transporting water having a pressure in excess of 100 bars from the water supply to a tool must be made liquid tight. Seals must therefore be provided in all places that cannot be made liquid-tight in any other way, regardless of whether or not this has been mentioned in the above description.