[1]3 @ 3 5 7 @ 7 0 7 United States Patent Office Patented Dec. 12, 1967 1 3,357,707 SHAFT SEALING SYSTEMS Frank Whittle, Walland Hill, Chagford, and John Frank Saunders, Bristol, England; said Saunders assi-,Uor to Bristol Siddeley Engines Limited, Bristol, England, a 5 British compazay Filed July 7, 1965, Ser. No. 470,040 Cl,qims priority, application Great Britain, July 10, 1964, 28,663/64 12 Claims. (Cl. 277-23) 10 ABSTRACT OF THE DISCLOSURE I n a seal assembly comprising inner and outer sleeve members and two sealing devices acting between the sleeve 1 5 members, there is pumping means driven by relative rotati on of the sleeves, and preventing the pressure between t he sealing devices,from substantially exceeding the press ure at the low pressure end of the assembly, and there is c ontrol means arranged to control flow past the sealing 2 0 d evice at the high pressure end so as to prevent the press ure between being less than the presstire at the low p ressure end. The invention relates to shaft sealing systems of the 2 5 k ind in which a high pressure zone on one side of the s ystem is separated frorn a low pressure zone on the other si de by two sealing devices with an inter-seal space bet ween them, and a pump is provided to return fluid leaki ng from the high pressure zone into the inter-seal space 3 0 b ack to the high pressure zone, the pressiire in the inter. s eal space not being allowed to fall below that of the low p ressure zone. One object of the invention is to provide a system of 3 5 t his kind adapted for use where no space is available for mounting pumps and other equipment externally of the a nnular space occupied by the sealing devices, and the o peratipg conditions are very arduous and exacting, as f or example in well-diilling eqtiipment including a tur4 0 b ine operated at the bottom of the bore hole by drilling fl uid ptimped down to it at high pressure. In this case a v ery effective seal is required to pr@-vent the escape of l ubricant from the lubr.;cation system of the turbine and it s replacement by drilling iluid laden with rock debris, a nd the problem is made more acute by the severe vibraA5 ti on to which the eqtiipment is subjected, and the relatively s mall radial dimeiision of the annular space available for t he sealing system between the hollow rotary shaft conv eying the drilling fluid and the casing of the turbine. According to the invention a seal assembly for 'mser5 0 ti on is an annular space between relatively rotatable shaft a nd casing parts, to prevent escape of fluid from a high p ressure end of the said space to a low pressure end, c omprises inner and outer sleeve members for fittina on t he shaft and in the casing respectively, two sealing d,- ,vices 5 5 e ach actiiig between the inner and otiter sleeve members a nd separated by an inter-seal space, positive displacement ptimping means arranged between the innermost i nner sleeve surface and the outermost outer sleev@, Surf ace and having an inlet opening from the inter-seal space 6 0 a nd ari outlet opening to the high pressure side of the s ealin- device at the high pressure end, and including an i nlet valve and an outiet valve, ptimp driving means arr anged so as to drive the pumping means during relati-,,e r otation of the sleeves, the pumping means preventing 6 5 t he pressure in the inter-seal space substantially exce-edin.- t he pressure at the low pressure end of the assem@ly while t here is relative rotation between the inner and outer sl eeves, and control means in the assembly responsive to 7 0 p ressure difference across the sealing device at the low pressure end and arranged to control a flow past the seal. 2 ing device at the hi.-h pressure end so as to prevent the pressure in the inter-seal space being less than the pressure at the low pressure end of the assembly, at least while there is relative rotation between the inner and outer sleeves. The flow past the sealing device at the high pressure end contro'lled by the control means may be either the discharge of the pumping means or a flow into the interseal space. When the discharge of the pumping means is controlled, the control may operate on the pump driving means, on the pump inlet or outlet valves or on a valve by-passing one or other of these valves. 'vvhen flow into the inter-seal space is controlled, the control preferably operates on a valve by-passing the seal at the high pressure end. The pumping means preferably comprises at least one cylinder formed in an annular member of the asseinbly, and a plunger operating in the cylinder and having an end cooperating directly or indirectly with a cam track formed on another annular member of the assembly which, in operation, rotates relatively to the firstmentioned annular member. These and other features of the invention are illustrated in the accompanying drawings showing as examples four arrangements in well-drilling turbines. FIGURES I to 7 relate to the first example, FIGURES 8 to 12 to the second example, while FIGURES 13 and 14 illustrate other arrangements semidiagranimatically. In the drawings: FIGURE IA is a section taken radially through the first example on one side of the axis of rotation, FIGURE IB is a continuation of FIGURE IA towards the left, showing other parts of the lubrication system, FIGURE 2 is a partial transverse section at the line 2-2 in FIGURE 1A, FIGURES 3 and 4 are fragmentary sections at the lines 3-3 and 4-4 respectively in FIGURE 2, FIGURE 5 is a partial transverse section at the line 5-5 in FIGURE 1A, FIGURE 6 shows part of one of the components as seen in the direction of the arrow 6 in FIGURE 1A, FIGURE 7 is a diagram showing the timing of pump inlet and discharge valves, FIGURE 8 is a section taken radially through the secoiid example on one side of the axis of rotation, FIGURE 9 is an enlarged partial transverse section at the lipe 9-9 in FIGURE 8, btit stepped axially as shown by the line 9-9 in FIGURE 10, FIGURE 10 is a partial sectioii taken at the stepped line 10-10 in FIGURE 9, FIGURE 1 1 is a partial transverse section at the line 11-11 in FIGURES 10 and 12, FIGURE 12 is a partial radial section at the line 1212 in FIGURE I 1, FIGURE 13 is a partial axial section illustrating a third arrangement, and a FIGURE 14 is a Dartial "taTi,-ential" section ill ustratin.fourth arrangement. In the example shown in FIGURES I to 7 the turbine parts adjacent to the seal assembly comprise a tubular shaft 20, the axis of which is shown at 21, journalled in a casin@ ing ' 22 by means of a double taper roller bear23a, 23b. The shaft has a spli-Tied part 24 on which an output coupling member 25 for attachment to a drill bit is mounted. To the left of the bearing 23b, as seen in FIGURE 1B, the clearance space between the shaft and the casing is closed by a pair of lip seals 19 arran,@ed back to back, and the shaft is formed with an annular cavity divided by a flexible sleeve 13 into an i-iiner lubricant reservoir 17 and an outer pressurising chamber 16.
[2]3 The lubricant reservoir is connected to the bearin.- space 10 by a passage 15, while the pressurising chamber is connected by passages 13 and 14 to the space 11 to the left of the seals 19, in which the pressure is substantially equal to that at the inlet to the turbine. A further connection throtigh a restrictor 12 to the bore of the shaft 20 may be provided to prevent accumulation of sediment in these spaces 11, 13, 14. The axis 21 is vertical during normal use, the left hand end of FIGURE IB being uppermost, and drilling fluid which has been pumped down to the turbine leaves through the bore of the shaft. The fluid at hi,-h pressure is ejected through jets in the drHI bit to assist the cuttin.- action, and returns up the bore hole, around the casing 22, laden with rock debris. The reservoir 17 and the bearin.- space 10 are fitted with lubricating oil at turbine inlet pressure so that, althou.-h there is substantially no pressure difference across the seals 19, there is a larae pressure difference between the bearing cavity and the outside of the casing, and an effective sealing system is necessary below the bearings to prevent escape of oil and contaniination of the oil by sand from the drilling fluid or by rock debris. The solution of the problem is made more difficult by the severe vibration which is produced by the operation of the drill bit in hard rock formations. In this example the sealing system below the bearings comprises inner sleeve members 26 and 27 which engage one another by means of dog teeth 28 and are mounted on the coupling niember 25, rotation relatively thereto bein- prevented by a number of dowels 29 engaging recesses 30 in the member 27. An outer sleeve member 31 is fitted in the bore of the casin.- 22 and is held between a screw threaded locking ring 32 and a spacin.@ sleeve 33 en.-aging the outer race of the bearing 23a. The outer sleeve 31 is formed at its left-hand end, as seen in FIGURE IA, with a flat face-seal surface 34 which is engaged by a counter face-seal surface 35 on a seal rina. 36 havin.@ an axial flange 37 and a radial flange 38. The inner surface of the axial flange 37 slides on an otitwardly flanged part of the inner sleeve 26, a secondary 0 ring seal 39 being interposed, and the sealin.@ surfaces 34 and 35 are held in inter-engagement by springs 40, housed in pockets in the sleeve 26 and bearina on the radial Ran-,e 38. The surface engaged by the secondary seal 39 is preferably at a radius such that the seal ring 36 is substantially balanced between the pressures in the bearing cavity and the inter-seal space 41. Dowel pins, not sho@vn, disposed at an.-ular spacings between the sprin,@s 40 ensure that the seal ring 36 rotates with the inner sleeve 26. Leakage froqi the bearing cavity between the inner sleeve and the couplin.- member 25 to the interseal space is prevented by an 0 ring 42, while further 0 rings 43 and 44 prevent leakage between the inner sleeve 27 and the coupling member 25 and between the outer sleeve 31 and the casin.- 22 respectively. The inter-seal space 41 is separated from space outside the casing by a low pressure seal consisting of a pair of lip seals 45 arranged back-to-back in a sleeve 46 mounted to slide in the outer sleeve 31 with the interposition of an 0 rin.- 47, the seals engagin- an external surface part of the inner sleeve 27. Rotation of the sleeve 46 relative to the outer sleeve 31 is prevented by a dog connection 48, and, for a reason presently explained, the low pressure seal assembly is urged against the pressure in the inter-seal space 41 by a circular multiple-leaf spring 49 (see FIGURE 6) the outer periphery of which is clamped betweeri the sleeve 31 and the locking rin.- 32. Oil leakin- from the bearing cavity into the inter-seal space 41 is retumed by a pump system comprising six plungers 50 operating in cylinders 51 (see FIGURE 5) fornied at equal angular spacings in an inwardly projectin,a flange part of the outer sleeve 31, the plungers being urged axially by springs 50a towards engagenient with a cam surface 52 formed on an outwardly projecting flange part of the inner sleeve 27. However, ex<:ept when there 3,357,707 4 is leaka,-e from the bearing cavity into the inter-seal space 41, the plungers 50 are held out of en.-agement with the cam surface 52 by a head portion 53 of the sleeve 46, this sleeve 46 being moved to the left by the pressure of the leaf spring 49. If oil leaks from the bearin-. cavity into the inter-seal space 41, the pressure in this space increases above that in the bore hole outside the casing until the low pressure seal assembly is driven to the right a.-ainst the leaf spring 49 sufficienti.y far to give the pump plun.-ers 10 50 a workina. stroke which just returns the leakage to the bearin-, cavity. Should the leaka.-C increase to an exient beyond the capacity of the pumping system, a sealin@. face on the head 53 enaages a counter surface 54 of the sleeve 27. These surfaces will of course be rotating 15 relatively to one another, but as this is only an emergency sealing device, the possibility of wear at this point can be tolerated. The inlet and discharge passage system of the pumps can be seen in FIGURES IA,,2 and 5 and comprises a 20 bore 55 extending radially outwards from each pump cylinder and having inner and outer branch bores extending axially to the face seal surface 34, the inner bore 56 operatin-, as an inlet passage and the outer bore 57 as an outlet passace, the outer end of the radial bore 25 being plugged at 55a. The counter face seal surface 35 on the rotating seal ring 36 is provided with alternate recesses 58 and 59 in its inner and outer edges (see FIGURES 2 to 4), and these recesses co-operate with the bores 56 and 57 to form a mechanically operated inlet 30 and discharge valve system. Part of the face seal surface 35 is shown in developed form in FIGURE 7 to illustrate diagrammatically the forniation of the recesses in relation to the contour of the cam surface 52, which rotates with the surface 35 in the 35 direction of the arrow 60, the pistons 50 and the ports 56 and 57 remaining in fixed angular positions. The cam surface has two crests, at the O' and 180' positions respectively, -and two valleys at the intervening 90' and 270' positions. There is a short dwell at each of these posi40 tions, during which both the ports 56 and 57 of the cylinder are closed by parts of the face seal surface 35 free from recesses. Considering the plunger 50 at the O' position in FIGURE 7, as the cam 52 and the face seal surface 35 move to the left, the plunger. makes an outward 45 stroke under the pressure of its spring, the inlet port 56 being open to the inter-seal space 41 during this period so that oil enters the cylinder' There is then a dwell with both ports closed, followed by an inward stroke and opening of the dischar@,e port 57 to allow the oil in the cylin50 der to be discharged back into the bearing cavity. The plungers operate oppositely in pairs, thus avoiding pressure fluctuations in the inter-seal space 41 which mi-,ht tend to cause mud from the bore hole to be drawn in past the low pressure seal assembly. The pressure in the interr)5 seal space 41 is in fact always sli.-htly higher than the bore hole pressure on the other side of the low pressure seal assembly by virtue of the force of the spring 49. In the second example, shown in FIGURES 8 to 12, an inner sleeve 70 fitted on the hollow turbine shaft 20 is 60 locked in place between the inner race of the bearing 23 and the output coupling member 25. Outer sleeves 71 -and 72 fitted in the casing 22 are connected together by bolts 73, a sealing gasket being interposed, and are locked in place between the outer race of the bearing 23 and a 65 screw-threaded locking ring 74. A groove 75, constituting an oil return passage as will presently bo explained, is formed along part of the external surfaces of the outer sleeves, these external parts being sealed from the bearing cavity by an 0 ring 76 and from the bore hole space 70 outside the casing by an 0 ring 77. The high pressure end seal is constituted by two face seal rings 78 and 79 having abutting flat sealing faces at 80. The left-hand ring 78, as seen in FIGURE 8, is axially slidable on a cylindrical surface 81 formed on the 75 outer sleeve 71, an 0 ring seal 82 being interposed, but
[3]3,357,707 5 is fixed against rotation relatively thereto by dowels, not shown, which are located at angular intervals between springs 83 housed in pockets in the ring and reacting against a flange 84 projecting inwards from the sleeve 71 to ur.-e the rin.- to the right. The right-hand ring 79 is axially slidable on -a cylindrical surface 85 formed on the inner sleeve 70, an 0 ring seal 86 being interposed, but is connected for rotation therewith by dowels, not shown, which are located at angular intenals between springs 87 housed in pockets in the sleeve 70 and reacting against the ring 79 to urge the ring to the left. The cylindrical surfaces 81 and 85 are equal in diame-ter so that the hydraulic pressures acting on the rings 78 and 79 do not tend to move them axially. In operation, the lefthand end of the assembly is uppermost, and the rings 78 and 79 float between the pressures of the springs 83 and 87 and are thereby to a large extent isolated from shocks travelling up the assembly from the drill bit, which is connected directly or indirectly to the output couplin@ member 25. Scaling assemblies of this kind are described in United States patent application Ser. No.- 381,832. Any lubricating oil escaping from the bearing cavity outwardly between the rings 78 and 79 enters an interseal space 88 separated from space outside the casin.by a low pressure seal consisting of a number of rin.-s of packing material 89 compressed in a recess in the inner sleeve 70 by a screw threaded gland nut 90 and bearing -against a cylindrical surface 9il on the outer sleeve 72. At each of two diametrically opposite positions, the outer sleeve 72 is provided with an axially extending pump cylinder bore 92 in which operates a plunger 93 havin.a tappet 94 engaging a cam surface 95 formed on the inner (rotating) sleeve 70. The cam contour is a simple "swash" surface providing one suction and one delivery stroke per revolution, the pump plungers moving oppositely so as to avoid pressure flucti-iations in the inter-seal space 88. The plungers are maintained in contact with the cam 95 by springs 96. As shown in FIGURES 9 and 10, each pump has an inlet valve 97 operating in a sleeve 98 housed in a bore 99 extending eircumferentially into the outer sleeve 72. The sleeve 98 has an external anniilar recess 100 communicating with an axial passage 101 opening into the int&r-seal space 88. From the recess 100, holes 102 lead to the interior of the sleeve and, when the valve is open, flow occurs past a valve seating stirface 103 to an internal recess 104 which is in comniunication with the interior of the valve by way of holes 105 and with the cylinder 92 ,by way.of a passage 106. A light spring 107 keeps the inlet valve closed except dur.,n.- pump suction. The delivery valve system is also shown mainly i@i FIGURES 9 and 10 and comprises a delivery valve 108 operating in an axially extending bore 109 in the outer sleeve 72 and urged against a scatin-. 110 by a light spring 111 reactilig against a plug 112. The bore 109 communicates with the pump cylinder 92 by a passage 113, and on the other side of th-- seating 110 has an external annular recess 114 which, as shown in FIGURE 9, is connected to the oil return groove 75 by a radial passage 115. From the groove 75 the oil returns to the bearin.cavity by way of a suppl@ementary non-return valve comprising a screw 116 (FIGURE 8) with a central bore leading into a stem part 117 carrying a rubber sleeve 113 covering branch outlet holes from the ccntral bore. To prevent the pumps reducing the pressure in th,@ inter-seal space 88 to below the pressure in the bore hole outside the casing, which would encourage er@try of grit past the low pressure seal, a system for by-passing the inlet valves 97 is provided. For each pump cylinder this comprises a shtittle valve 119 operating il an axial bore 120 in the outer sleeve 72 and having an external groove 121 which, in one end Dosition of the valve 119, connects a passa,@e 122 from the inlet valve recess 100 to the interior of the pump cylinder 92 by way of a passage 123, 6 passage 113. The shuttle valve 119 is urged to the said end position by a spring 124 and by hydraulic pressure transmitted through a passage 125 from the interior of a rubber capsule 126 which, as shown in FIGURES 11 and 12, is clamped in a recess 127 in the sleeve 72 by a plug 123, the extorior of the capsule being subjected to bore hole pressure by way of a passage 129. The other end of the shuttle valve 119 is subjected to the pressure in the inter-seal space 38 by way of a branch 130 from 10 the passage 122. When the inter-seal space pressure exceeds the bore hole pressure plus the force of the spring 124, the shuttle valve 119 is displaced axially so that connection between the parts 122 -and 123 of the passage by-passing the pump inlet valve 97 is interrupted and jr, the pump becomes operative to return oil from the interseal space to the bearing cavity by the route already 4escribed. If th@. turbine is stalled, the pressure in the inter-seal space will rise, and sufficient leakage may occur past the 20 piston of the shuttle valve 119 into the capsule 126 to over-extend and damage it. To prevent this, a relief valve with @a low opening pressure may be connected between the passage 125 and the space outside the low pressure seal 89 to prevent the pressure in the capsule rising sub25 stantially above that in the bore hole, The seal assembly shown in FIGURES 8 to 12 has the advantage that it can be tested before installation, and then installed without separatioi of the co-acting sealiiig members, so as to avoid the possibility of a defect being 30 introduced during re-assembly of coniponent parts. , In both the arrangements already described, the pump cylinders are formed in a sleeve member which is in d relation to the casing, but th,ey could equally well be formed in a member which is in fixed relation to the shaft, 35 both arrangements enabling the pressure difference across the low pressure sealing rneans to be applied in a convenient manner to lift the pump pistons off their driving cams or to control the operation of the pump inlet and/or discharge valves. FIGURE 13 illustrates a further ar40 rangement ii, which the pump cylinders are forined in one of the axially slidable face seal rings. In FIGURE 13, the upstream face seal ring 140 slides axially on a surface 141 on a sle,-ve member 142 fixed to the casing, which is considered to be the nonrotating 45 member, while the rotating face seal ring 143 slides axially on a surface 144 on a sleeve member 145 fixed to the shaft. Two or more equally spaced radial cylinder bores 146 are formed in the rin.- 143, and each bore contains a pump piston 147 havir.,g a slipper 143 at its radially outer end engaging a cam surface 149 on the sleeve 142. The piston has an @axial bore 150 constituting an inlet passage from the ititer-seal space 151. This inlet passage 150 is closed dur-,'-q.- the pumping stroke by a ball 152. At its radially inner end the cylinder has a discharge pas55 sage 153 communicating with the bearing cavity. This passa,-e 153 is closed during the suction stroke by a ball 154. To prevent the pumps reducing the pressure in the inter-seal space 151 to below the pressure outside the 60 casing, a passage 155 is provided from the bearing cavity to the inter-seal space, and this passage 155 is controlled @by a valve 156 operated by a diaphragm 157 subjected on one side to the pressure in the inter-seal space and on the other side to the pressure outside the casing. In 65 effect, the valve 156 allows sufficient oil to pass the seal betiveen the rings 140 and 143 to preve-iit the pumps reducing the pressure in theinter-soal space 151 to below that outside the casing. FIGURE 14 illustrates another convenient arrangement in which the control acts on a transmission system be70 tween a cam follower and a pump piston. FIGURE 14 is analo.@ous to FIGURE 10 and is a diagrammatic "tangential" section throagh part of a sleeve member, fixed either to the casing or to the shaft. A cam follower an end portion of the valve cylinder bore 109 and the -1 r) piston 160 operates in a bore 161 in the sleeve member
[4]7 162 and is held in engagement with a cam 163 on an adjacent relatively rotatable member by a @li.-bt spring 164. The space 165 is part of the inter-seal space. From behind the piston 160 a branch 166 from the cylinder leads to the end of a pump cylinder 167 containing a pump piston 168 operating against a light spring 169, the cylinder having an inlet passage 170 from the interseal space 165 controlled by -an automatic inlet valve 171, and a discharge passage 172 to the bearing cavity controlled by an automatir, discharge valve 173. Also branching from the cylinder 161 is a passage 174 leading to the inter-seal space 165 and controlled by a shut-off valve 175 operated by a piston 176 moving in a cylinder 177. A passage 178 from the inter-seal space to the cylinder 177 allows the interseal space pressure to act on tb.piston 176 in the shut-off direction in opposition to a spring 179 plus the pressure outside the casing, transmitted through a rubber capsule 180 as described in connection with FIGURE 12 With this arrangement, reciprocation of the cam follower piston 160 merely displaces oil in and out of the inter-seal space until the inter-seal space pressure rises sufficiently above the pressure outside the casing to cause the piston 176 to close the valve 175. The oil trapped in the cylinder 161 and the passage 166 then acts as a transmission element to operate the pump piston 168. The particular advantage of this arrangement is that it allows great latitude in the positioning of the various components and thus simplifies their accommodation in a sleeve member of small cross sectional dimensions. We
