U.S. patent application number 10/553392 was filed with the patent office on 2007-03-08 for pump drive head with integrated stuffing box and clamp.
Invention is credited to Mariano Pecorari, Pietro Pecorari.
Application Number | 20070051508 10/553392 |
Document ID | / |
Family ID | 37828992 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070051508 |
Kind Code |
A1 |
Pecorari; Mariano ; et
al. |
March 8, 2007 |
Pump drive head with integrated stuffing box and clamp
Abstract
The improved pump drive head (1) has an integrated stuffing box
(9) and comprises: a power transmission (3, 4) coupled to the
rotating pump driveshaft (8) within a crude oil well; a stuffing
box (9) to retain the pressure; a thrust assembly (6) adapted to
take the tensile force exerted on said pump shaft. It further has
said power transmission comprised of a tube (5, 16) arranged to be
rotated coaxially with the shaft (8) and having at least two
different diameters. The rotary seals (20; 50) fit over the small
outside diameter of the tube to establish fluid-tightness between
said tube and the body (19) of the stuffing box. The working
diameter (51) of the seals (20; 50) is smaller than the large
outside diameter of said tube (5, 16). Static seals (17) are
provided between the tube and the shaft (8). Thus, the static seals
(17) and rotary seals (20; 50) are adapted to come away along with
said tube and the retainer ring (22) for the seals. Advantageously,
associated with said head is the improved clamp (10) for locking
the rotary pump driveshaft (8) in crude oil wells, which clamp
includes a jaw pair (35, 36), a pull one (35) and a push one (36)
operated by means of a screw (38) acting with its end on one jaw
(35) and engaging a threaded hole in the other jaw (36).
Inventors: |
Pecorari; Mariano;
(Swarthmore, PA) ; Pecorari; Pietro; (fraz S.
Donnino N., IT) |
Correspondence
Address: |
MCGINN INTELLECTUAL PROPERTY LAW GROUP, PLLC
8321 OLD COURTHOUSE ROAD
SUITE 200
VIENNA
VA
22182-3817
US
|
Family ID: |
37828992 |
Appl. No.: |
10/553392 |
Filed: |
November 26, 2003 |
PCT Filed: |
November 26, 2003 |
PCT NO: |
PCT/IT03/00779 |
371 Date: |
July 27, 2006 |
Current U.S.
Class: |
166/68.5 ;
166/78.1; 166/84.1 |
Current CPC
Class: |
E21B 43/126
20130101 |
Class at
Publication: |
166/068.5 ;
166/078.1; 166/084.1 |
International
Class: |
E21B 43/00 20060101
E21B043/00; E21B 19/00 20060101 E21B019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2003 |
IT |
IT03/00233 |
Claims
1. An improved pump drive head having an integrated stuffing box
and comprising: a power transmission coupled to a rotating pump
drive shaft within a crude oil well; a stuffing box to retain the
pressure; and a thrust assembly adapted to take the tensile force
exerted on said pump shaft, wherein said power transmission
comprises a tube arranged to be rotated coaxially with the shaft
and having at least two different diameters, wherein the rotary
seals fit over the small outside diameter of the tube to establish
fluid-tightness between said tube and the body of the stuffing box,
the outside diameter of the seals being smaller than the large
outside diameter of said tube, and wherein the tube-to-shaft fit
incorporates static seals and the static ones and rotary ones of
the seals are adapted, by virtue of a retainer ring provided, to
come away along with said tube and the component parts associated
with the seals inside said stuffing box.
2. An improved head according to claim 1, wherein the tube, being
rotated coaxially with the shaft, is connected with its bottom end
axially to a sleeve for rotation therewith and jointly defining
said large and small diameters, the small diameter locating inside
the stuffing box and the tube and sleeve, once connected together,
forming a unitary piece.
3. An improved head according to claim 1, wherein a rotary gasket
is provided on the bottom end of said tube/sleeve for rotation
therewith, the outside diameter of the gasket being a labyrinth
pattern.
4. An improved head according to claim 1, wherein said gasket is
connected to the retainer ring of the seals on said tube/sleeve of
the stuffing box.
5. An improved head according to claim 1, wherein an
outside-communicated tapping hole is provided downstream of the
gasket and/or the respective oil seals in the direction of the
pressurized flow from the well.
6. An improved head according to claim 1, wherein, when the rotary
seals comprise packing seals, an oil seal is provided downstream of
the rotary seals and of the inlet hole for the liquid lubricant to
the packing, the packing being mounted between said tube/rotating
sleeve and the inner seat of the stuffing box.
7. An improved head according to claim 1, wherein the packing is
mounted on said rotating sleeve through at least one detent ring
and a pre-load spring between the packing and said retainer
ring.
8. An improved head according to claim 1, wherein the packing is
mounted around the small diameter of said tube/rotating sleeve and
is held there by at least one axial retainer ring and a pre-load
spring placed between the packing and the axial thrust
assembly.
9. An improved head according to claim 2, wherein the static seals
are placed for reduced radial bulk in the joint region between said
tube and said sleeve, and are compressed there to make a tight seal
as said tube and sleeve are made fast together.
10. An improved head according to claim 1, wherein the static seals
are placed for convenient replacement in the joint region between
said tube and the shaft, and make a tight fit within the skirt of
the top cover.
11. An improved head according to claim 1, wherein said tube is
connected to the thrust assembly for rotation therewith by a
rotating hub held in place by a guiding tighten-down means.
12. An improved head according to claim 11, wherein said guiding
tighten-down means comprises a rolling thrust bearing and a bell
enclosing said hub and said thrust bearing.
13. An improved head according to claim 11, wherein said guiding
tighten-down means comprises a rolling thrust bearing disposed in
the upper portion of the drive housing and a bell covering said hub
and thrust bearing.
14. An improved head according to claim 11, wherein said hub is
formed on its inside diameter with an axial slot for pulling out
the connection tongue between said tube and the drive.
15. An improved head according to claim 6, wherein the packing
pre-loading spring in the stuffing box is disposed inside a split
casing to prevent overloading the spring when in the compressed
state.
16. An improved head according to claim 8, wherein a ring spacer is
provided in the stuffing box which is bored for communication with
the liquid lubricant inlet hole.
17. An improved head according to claim 16, wherein said bored ring
spacer is formed with an annular seat for a lip-type oil seal
arranged to contact the diameter of said tube/sleeve.
18. An improved head according to claim 16, wherein said bored ring
spacer is formed with an axial middle ledge for insertion past the
lip of an adjacent ring seal.
19. An improved head according to claim 1, wherein a gasket
carrying a labyrinth pattern on its inside diameter is keyed to the
bottom end of the sleeve for rotation therewith.
20. An improved head according to claim 1, wherein a shaft locking
clamp, placed within the body of the stuffing box, comprises a jaw
pair, one pulls and one pushes, operated through a screw arranged
to act with its end on one jaw and engaged in a threaded hole
formed in the other jaw.
21. An improved head according to claim 20, wherein said push and
pull jaws are operated through a screw arranged to act with its end
on the push jaw and engaged in the threaded hole formed in the pull
jaw.
22. An improved head according to claim 20, wherein the stem of the
screw is cylindrical and fits through a seal on the cover.
23. An improved head according to claim 20, wherein guide and
elastic bias members are provided between the pull jaw and the
cover.
24. An improved head according to claim 1, wherein a clamp with
self-centering jaws is associated with the body of the stuffing
box, the jaws gripping the shaft in a wedge contact relationship of
the outer surfaces of the jaws to the inner surface of the sliding
body of the clamp under the action of the tighten-down screw.
25. An improved head according to claim 24, wherein the wedge
contact is advantageously achieved by provision of a conical
surface taper.
26. An improved head according to claim 24, wherein the radial
gripping movement of the jaws is guided by a prismatic fit to the
clamp housing or cover.
27. An improved head according to claim 24, wherein an elastic
means is mounted between the two jaws to open them when the
clamping action is released.
28. An improved head according to claim 24, wherein the
shaft-gripping surfaces are semicircular about a center that is
offset from the shaft centerline in a direction toward the opposite
jaw.
29. A clamp for locking the rotary pump drive shaft in crude oil
wells, comprising: jaws adapted to be closed around the drive shaft
by screws, wherein said jaws are paired, one pulls and one pushes,
for operation by a screw acting with its end on one jaw and engaged
in a threaded hole formed in the other jaw.
30. A clamp according to claim 29, wherein it comprises a jaw pair,
one pulls and one pushes, for operation by means of a screw acting
with its end on the push jaw and engaged in a threaded hole formed
in the pull jaw.
31. A clamp according to claim 29, wherein the stem of the screw is
cylindrical and fits through a seal on the cover.
32. A clamp, according to claim 29, wherein between the pull jaws
and the cover there are guide and elastic-reaction parts.
33. A clamp for locking the rotary pump drive shaft in crude oil
wells, comprising: jaws adapted to be closed around the drive shaft
by means of a screw, wherein the self-centering jaws are operated
to close by a wedge contact relationship established between the
outer surfaces of the jaws and the inner surface of the sliding
body of the clamp under the action of the tighten-down screw.
34. A clamp according to claim 33, wherein the wedge contact is
achieved by provision of a conical surface taper.
35. A clamp according to claim 33, wherein the radial gripping
movement of the jaws is guided by a prismatic fit to the clamp
housing or cover.
36. A clamp according to claim 33, wherein an elastic means is
mounted between the two jaws to open them when the clamping action
is released.
37. A clamp according to claim 33, wherein the shaft-gripping
surfaces are semicircular about a center that is offset from the
shaft centerline in a direction toward the opposite jaw.
Description
[0001] The invention relates to an improved pump drive with
integrated stuffing box and clamp, i.e. a drive head for mounting
at the top of a crude oil well pipe for operating the pump
installed in the well, the pump being most commonly a positive
displacement rotary design having a progressing helical cavity.
[0002] Known in the prior art are a number of different drives
arranged to act on the ground surface end of the pump according to
the well delivery rate. Thus, constant delivery rate wells mount
electric motors connected drivingly to the pump shaft, the pump
being as mentioned most commonly a rotary positive displacement
type with a progressing helical cavity. Alternatively, a hydraulic
motor is provided with a variable ratio hydraulic drive for
tracking the well delivery rate up to steady state. The power
transmission of the drive may include a gear or belt arrangement.
In either case, however, the pump is to be coupled to the drive
somewhere above the stuffing box, such that the interior of the
well pipe, where the oil pressure is that created by the pump or is
the pressure of the well itself, can be held isolated and the drive
advantageously maintained at atmospheric pressure. Finally, under
the pulling force applied to the drive shaft by a particular pump
type, the transmission bearing block must withstand high axial
thrust forces.
[0003] Known in the art are several ways of arranging the
components of said head for easier servicing of parts that are more
likely to undergo wear or failure, such as stuffing box leakage due
to continual operation and the presence of silt deposits in the
crude oil, or possible thrust bearing failure under the axial force
exerted on the drive shaft by the pump. This involves periodical
servicing and daily monitoring, usually by a technician.
[0004] During such servicing, the pump in the well should be shut
down for the shortest possible time because, due to the mixed
nature of the fluid being pumped it can easily become clogged,
resulting in a costly well re-start procedure. Thus, quick
replacement of parts is of vital importance to a short-duration
stoppage of the well pump for service operations.
[0005] Known is, e.g. from US Patent Application 2001/0050168 A1, a
pump drive head with an integrated stuffing box, wherein the
stuffing box locates above the rotary drive and uses an internal
standpipe attached to the coupling flange at the top of the well
bore pipe. Thus, motion transmitted through the drive is used for
rotating a tube mounted outside the stuffing box, since the
coupling of the drive to the pump shaft is placed above the
components of the head. The stuffing box, therefore, intervenes
between the internal standpipe and the outside tube connecting the
drive to the coupling of said tube to the pump inner shaft.
[0006] While by having the stuffing box placed on the top side of
the head, a technician can reach it more conveniently, the stuffing
box is difficult to check for tightness because the seal is mounted
within a rotating part. The aforementioned patent application
teaches ways of pressurizing the seals from a suitable hydraulic
system to prevent leakage and spilling onto the ground. However,
this involves significant complication over the conventional
arrangement of the stuffing box below the drive head, whereby the
extent of a failure can be checked visually by tapping the stuffing
box at different levels.
[0007] In addition, the dual function of the drive main
bearings/pump shaft thrust bearing invariably involves overhauling
the whole drive, rather than just the thrust bearing as the
component most subject to fail. Field disassembly of the drive
requires more than an hour, compared to the 20 to 40 minute time
limit for the well shutdown.
[0008] Finally, for the operation to be performed in less time,
something has to be done to make the clamps on the underside of the
wellhead a more practical design. To lock the pump driveshaft, a
radial clamp means is closed around the shaft by means of two
screws operated from outside. The aforementioned patent application
illustrates a few designs for this means. The technician, before he
can act on the head, locks the shaft in order to prevent it from
dropping down the well; therefore, having to operate two screws may
lead unskilled or careless personnel to torque one screw more than
the other and cause the shaft to bend or become damaged.
[0009] The prior art is open to considerable improvement in the way
of providing the head with a pump drive which can obviate the above
deficiencies and make the servicing procedures faster to complete
and more effective in a reliable manner.
[0010] In the light of the foregoing, the underlying technical
problem of the invention is to provide a pump drive head, the
stuffing box and/or thrust bearing of which can be readily replaced
without the drive having to be disassembled in the field, and while
still using the conventional checking method of tapping at
different levels. Another object is to allow for both standard and
packing-type seals to be replaced the same way. Not least an object
is to provide a clamp of simple construction to effectively hold
the rotary shaft locked during servicing operations.
[0011] The above technical problem is solved by the invention
providing an improved pump drive head having an integrated stuffing
box and comprising: a power transmission coupled to the rotating
pump driveshaft within a crude oil well; a stuffing box to retain
the pressure; a thrust assembly adapted to take the tensile force
exerted on said pump shaft; characterized in that said power
transmission comprises a tube arranged to be rotated coaxially with
the shaft and having at least two different diameters; that the
rotary seals fit over the small outside diameter of the tube to
establish fluid-tightness between said tube and the body of the
stuffing box, the outside diameter of the seals being smaller than
the large outside diameter of said tube; that the tube-to-shaft fit
incorporates static seals; and that the rotating and static seals
are adapted, by virtue of a retainer ring provided, to come away
along with said tube and the component parts associated with the
seals inside said stuffing box.
[0012] In a preferred embodiment, the tube, being rotated coaxially
with the shaft, is connected with its bottom end axially to a
sleeve for rotation therewith and to jointly define said large and
small diameters, the small diameter locating inside the stuffing
box and the tube and sleeve, once connected together, forming a
unitary piece.
[0013] In another preferred embodiment, a gasket is provided on the
bottom end of said tube/sleeve for rotation therewith, the outside
diameter of the gasket being a labyrinth pattern.
[0014] In another preferred embodiment, wherein the rotary seals
are packing seals, an oil seal is provided downstream of the rotary
seals and of the inlet hole for the liquid lubricant to the
packing; the packing being mounted between said tube/rotating
sleeve and the inner seat of the stuffing box.
[0015] In another embodiment, the packing is mounted on said
rotating sleeve through at least one detent ring and a pre-load
spring between the packing and said retainer ring.
[0016] In another embodiment, the packing is mounted around the
small diameter of said tube/rotating sleeve and is held there by at
least one axial retainer ring and a pre-load spring placed between
the packing and the axial thrust assembly.
[0017] In another embodiment, the static seals are placed for
reduced radial bulk in the joint region between said tube and said
sleeve, and are compressed there to make a tight seal as said tube
and sleeve are made fast together.
[0018] In another preferred embodiment, the static seals are placed
for convenient replacement in the joint region between said tube
and the shaft, and make a tight fit within the skirt of the top
cover.
[0019] In another preferred embodiment, said tube is connected to
the thrust assembly for rotation therewith by a rotating hub held
in place by a guiding tighten-down means.
[0020] In another preferred embodiment, said hub is formed on its
inside diameter with an axial slot for pulling out the connection
tongue between said tube and the drive.
[0021] In another preferred embodiment, the packing pre-loading
spring in the stuffing box is disposed inside a split casing to
prevent overloading the spring when in the compressed state.
[0022] In another preferred embodiment, a ring spacer is provided
in the stuffing box which is bored for communication with the
liquid lubricant inlet hole and is formed with an annular seat for
a lip-type oil seal arranged to contact the diameter of said
tube/sleeve.
[0023] In another embodiment, said bored ring spacer is formed with
an axial middle ledge for insertion past the lip of an adjacent
ring seal.
[0024] In another embodiment, a gasket with a labyrinth pattern on
its inside diameter is keyed to the bottom end of the sleeve for
rotation therewith.
[0025] In another preferred embodiment, a shaft locking clamp;
advantageously placed within the body of the stuffing box,
comprises a jaw pair, one pulls and one pushes, operated through a
screw arranged to act with its end on one jaw and engaged in a
threaded hole formed in the other jaw; said push and pull jaws
being operated through a screw arranged to act with its end on the
push jaw and engaged in a threaded hole formed in the pull jaw.
[0026] In another preferred embodiment, a clamp with self-centering
jaws is associated with the body of the stuffing box, the jaws
gripping the shaft in a wedge contact relationship of the outer
surfaces of the jaws to the inner surface of the sliding body of
the clamp under the action of the tighten-down screw;
advantageously, this wedge contact is achieved by provision of a
conical surface taper.
[0027] In a further preferred embodiment, the radial gripping
movement of the self-centering jaws is guided by a prismatic fit of
the clamp on the box or the cover; an elastic means is mounted
between the two jaws to open them when the clamping action is
released; advantageously, the shaft-gripping surfaces are
semicircular about a center that is offset from the shaft
centerline in a direction toward the opposite jaw.
[0028] One possible embodiment of the invention is shown by way of
example in the accompanying ten drawing sheets, in which:
[0029] FIG. 1 is a longitudinal section view of the improved head
according to the invention, showing the overall configurations of
the stuffing box, drive (here a gear power transmission), thrust
bearing, and clamp for locking the pump driveshaft;
[0030] FIG. 2 is a partial enlarged view limited to the rotating
bearings of the drive, thrust bearing, and stuffing box;
[0031] FIG. 3 is a vertical cross-section view of the
self-centering clamp for locking the pump driveshaft;
[0032] FIG. 4 is a sectional plan view of the clamp of the
preceding Figure;
[0033] FIG. 5 is a longitudinal section view of the improved head,
with an unspecified drive, showing the overall configurations of
the stuffing box, thrust bearing, and clamp for locking the pump
driveshaft;
[0034] FIG. 6 is an enlarged detail view of the head shown in FIG.
5;
[0035] FIG. 7 is a sectional view of the stuffing box highlighting
the packing mount;
[0036] FIG. 8 is a sectional view of another embodiment of the
improved head incorporating a modification of the stuffing box and
the self-centering clamp;
[0037] FIG. 9 is an enlarged sectional view of the shaft power
drive and the stuffing box;
[0038] FIG. 10 is an enlarged sectional view of the self-centering
jaw clamp for the rotating shaft; and
[0039] FIG. 11 is a sectional plan view of the clamp shown in the
preceding Figure, with one of the jaws being shown in section.
[0040] In FIG. 1, the wellhead 1 is shown to include the drive 2
with gears 3, 4 that are driven by the motor M, the gear 4 being
keyed to a rotating tube 5 connected upwardly to the thrust
assembly 6 and, through the conventional coupling 7, to the
rotating driveshaft 8 of the pump down the well bore. Also, the
stuffing box 9 is shown beneath the drive 2 and as being
advantageously integrated here to the self-centering clamp 10 with
jaws for locking the shaft 8.
[0041] FIG. 2 shows in greater detail the main bearings 11 for the
gear wheel 4 on the housing 12 of the drive 2. The rotating tube 5
is keyed to the gear wheel 4 by the tongue 13 and extends coaxially
within the gear wheel 4. The bottom end 14 of the tube 5 is
threaded at 15 for engagement with the rotating sleeve 16 of the
stuffing box. Static ring seals 17 are held compressed between said
end 14 and the sleeve 16, these being the parts that would bear on
the rings during rotation. The rotating sleeve 16 of the stuffing
box carries the axial thrust bearing 18 arranged, inside the body
19 of said box, to take the axial load from the well pressure
acting on the seals 20. Engaged threadably with the bottom end 21
of said rotating sleeve 16 is the retainer ring 22 arranged to
retain said seals and used for pulling them off, the seals being
shown held apart by spacers 23 that abut against said thrust
bearing 18. A rubber gasket 24 is connected to the retainer ring 22
which is formed with a peripheral labyrinth pattern 25 on its
outside diameter to catch as much as possible of the solids trapped
in the pumped fluid. A radial tapping hole 26 is formed above the
gasket 24 and at each oil seal 20 for use, when required, to check
the respective upstream seal for leakage under the well
pressure.
[0042] Also in FIG. 2, said tube 5 is shown connected rotatably to
the hub 27 of the thrust bearing, to which it is fastened together
with the top cover 28 by the screws 29. This hub can rotate under
the bell 30 covering the bearing 31 of the thrust assembly 6, and
has an upper oil seal 32. This bell is fastened to the housing 12
of the drive 2 by screws 33. Said hub 27 is formed with an axial
slot 34 on its inside diameter to allow the tongue 13 to be pulled
away without the thrust assembly 6, i.e. the hub 27, bell 30 and
bearing 31 having to be disassembled.
[0043] FIG. 3 shows the pull and push jaws 35 and 36 around the
outside diameter of the shaft 8. For enhanced grip, the contact
areas are knurled horizontally as at 37. The jaw pair are closed by
the outside-operated screw 38, which screw is provided with a seal
39 around its stem 40 to stop leakage of pressurized fluid. The
female threadway is formed on the body of the pull jaw 35, and the
end of the screw 41 acts on the push jaw 36. In FIG. 3, the clamp
10 is shown open, and is shown closed in FIG. 4. For guiding and
elastic bias purposes, at least two pins 43 and two springs 44 are
placed between the pull jaw 35 and the cover 42, which are
effective to keep the jaws from turning and bias them to the open
position.
[0044] Shown in FIG. 5 is the head for the power transmission 45 to
the shaft of the pump 8 of a crude oil well; when the head is
constructed other than from gears, e.g. comprises a pulley (not
shown) keyed to the tube 46 by the tongue 47 to rotate with the
tube. The thrust assembly 6 is provided with a hub 48, similar to
the hub 27 described above but formed with no axial slot. This
thrust assembly, having to take radial forces on said tube 46 as
well, additionally includes a radial bearing 49 and the sleeve 16
of the stuffing box 9. FIG. 6 shows in further detail the stuffing
box with the oil seals 20 and intervening rings 23, and the static
seals 17 held tight on said shaft 8 by the end 14 of the tube 46.
It can be seen that the hub 48 guides the sleeve 16 of the stuffing
box, and above this, said tube 46. In this it differs from the
embodiment shown in FIG. 2, wherein the sleeve 16 of the stuffing
box and the tube 5 are guided on the hub of the gear wheel 4.
[0045] Furthermore, FIG. 7 shows the bottom end 21 of said rotating
sleeve 16 engaged threadably with the ring 22 to retain said
packing 50, itself located between said sleeve and the inner seat
51 of the stuffing box 9. The packing is retained on said sleeve by
the retainer ring 22, the detent rings 52 and spring 53 against
said axial thrust bearing 18. A bored ring spacer 54 and an oil
seal 55 are provided between the packing 50 and said bearing 18.
Said inner seat 51 has a shoulder 56 for abutment by the ring 52 in
the assembled state. The spring 53 is to pre-load the packing 50,
and in the assembled state, the ring 22 will be held spaced apart
from the bottom detent ring 52. The tapping holes 57, where
provided, are covered by the packing 50. The hole 58 is to admit
lube oil to the inside diameter of the packing as this is sliding
across the outer surface of said rotating sleeve 16. On possible
collapsing failure of the packing 50, the well fluid would rise
above the bearing 18 and overflow through the vent hole 59 at
atmospheric pressure.
[0046] Another embodiment of the head is illustrated by FIGS. 8 to
11. In FIG. 8, there is shown the integrated stuffing box 60, where
a sleeve 61 is rotated rigidly with the shaft 8 in rubbing
relationship to the packing 50. This sleeve extends coaxially with
and is firmly coupled in sealed relationship to the tube 62 that
transfers the motion from the gear 4 to the coupling 7 via the
skirt 63 of the cover 28. The static seals 64 are placed between
the cover skirt and the shaft 8, so that the seals 64 can be
readily pulled off by first uncoupling the coupling 7 and removing
the cover 28 with the skirt 63. Furthermore, the clamp 65 is shown
located beneath said integrated stuffing box with its
self-centering jaws 66 closed by actuation of just the lead screw
67 and by effect of the conical fit 68 provided between the jaws
and the sliding body 69.
[0047] Shown in FIG. 9 is the body 12 of the head 1, whose upper
portion 70 receives the thrust assembly 6 mounted under the bell
71, the latter being fastened by screws 72. The body 73 of the
stuffing box 60 is an integral part of the drive housing 12 and is
formed with two radial holes, of which the lower one 74 is located
upstream of the packing 50 same as the lowermost one of the holes
57, and the upper one 75 same as hole 58, for supplying clean lube
oil to the rotary packing-type seal 50 acting on the outside
diameter of the sleeve 61. The gasket 76 with labyrinth 77, in
static contact with the shaft 8, is keyed to the bottom end of the
sleeve 61 for rotation therewith. Said bottom end of the sleeve
also carries the axial retainer ring 78 for pulling off the
internal components of the stuffing box 60. An axial retainer ring
79, being larger than ring 78, is mounted between the lowermost
packing 50 and an axial ledge 80 on the body 73. Next to said
packing is a casing split into two halves 81 and 82 that are spaced
apart to enclose the packing pre-load spring 83. The casing
contacts with its top portion the ring 84, which ring is drilled
radially to provide a passage for the pressurized lube oil from the
hole 75. The bottom portion of this ring is formed with an inner
seat 85 receiving a rotary lip seal 86, the top portion of the ring
being formed with a middle, axially extending ledge 87 for
insertion between the outer metal shell and the outer/inner lip of
a seal ring 88 on the surface of said rotating sleeve 61. This
middle ledge 87 is to transfer a possible axial thrust load
directly to the axial thrust bearing 18. Last, an isolating ring
89, provided for the thrust bearing 31, fits over the outer
diameters of the hub 27 and the hub of gear 11.
[0048] FIGS. 10 and 11, illustrating another embodiment of the
self-centering clamp 65 for locking the shaft 8, show recesses 90
provided in the body 69 for the shaft 8 to go through during the
clamp-down operation. Each said self-centering jaw 66 is provided
with a pin 91 for guided movement in the slot 92 formed in the
cover 93 of the clamp casing 94. Each jaw has a prismatic guide 95
that lies normal to the direction of the jaw radial gripping
movement, the guide tapering along the radial direction of the
shaft 8. The prismatic guide 95 fits for radial sliding movement in
a circular groove 96 cut in said cover 93, with the jaw being
guided by said pins 91. Two springs 97 are received in sockets
along a parallel direction to the clamping direction to bias the
jaws 66 to the open position upon removal of the clamp-down force.
A socket 98 is provided in the area of the screw 67 on the body 69
to allow the screw head through, and rotation-preventing pins 99
ensure an orientated setting of the body 69 within the casing 94.
The shaft-gripping surfaces 100 are semicircular about a center
which is offset toward the opposite jaw with respect to the
centerline of shaft 8, and are slightly roughened with circular
cross-section knurled formations.
[0049] The wellhead and drive disassembling/re-assembling for
servicing is effected, upon the shaft 8 being stopped from
rotating, by operating the screw 38 to close the clamp 10 such that
its jaws 35, 36 will grip the shaft; the jaws self-centering
themselves around the shaft without damaging it. Once the shaft is
clamped down and the well pressure exhausted, a conventional device
is used for loosening the coupling 7 and releasing the connection
between the shaft 8 and the rotating tube 5 or 46. By removing the
screws 29 and cover 28, the sleeve 16, static seals 17 and oil
seals 20 of the stuffing box 9 can be slipped off for quick
replacement. In the embodiment of FIG. 2, the tongue 13 would not
interfere with removal of the tube 5 because of the slot 34
provided in the hub 27. Replacement of the tube assembly 5 or 46,
sleeve 16 with the static seals 17, bearing 18, rotary seals 20,
oil seals or packing, retainer ring 22, and gasket 24 is quickly
effected for a minimum of well shutdown. Assembly would proceed in
the reverse order.
[0050] To also take down the thrust assembly 6, by loosening the
screws 33 the thrust bearing 32 is released. Where both the
stuffing box and thrust assembly are to be replaced, by merely
loosening the screws 33 the thrust assembly 6 and stuffing box
assembly can be removed in a single, readily performed operation.
In this respect, the embodiments of FIG. 2 and FIG. 6 would be
dealt with in a slightly different manner from each other, namely
the gear transmission 2 would remain connected to the body 19 of
the stuffing box 9, as would the respective bearings 11, and the
bearing 49 removed together with the thrust assembly 6 and the
inner parts of the stuffing box 9.
[0051] Finally, the holes 26, in addition to being useful to tap
off leakage past the oil seal 20 or the gasket 24 located upstream,
may be used to introduce fluid, advantageously oil, under a
pressure in order to enhance the sealing action of the affected oil
seal 20, the pressure being propagated to the next oil seals in the
direction toward the thrust bearing 18.
[0052] When the packing 50 is employed, the ring 22 would be
retaining the packing 50 and detent rings 52 for assembling. For
disassembling, the ring 22, by acting against said detent rings 52
and the fully compressed spring 53, would urge the compressed
packing against the inner wall 51 of the box 9 and loosen it, thus
allowing it to be removed as a whole.
[0053] In the embodiment of FIGS. 8 and 9, the stuffing box
operates as explained here below. Upon assembly, the packing 50
would be forced by the spring 83 against the axial retainer ring 79
and ledge 80; the packing being compressed between the outside
diameter of the rotating sleeve 61 and the bore in the body 73. The
sleeve turns together with the shaft 8 and the gasket 76 with
labyrinth 77 to stop slime in the crude oil being lifted from
reaching, under the pressure, the static seals 64 between the shaft
8 and the sleeve 63 at the top end of the head. The additional
axial retainer ring 78 is utilized as the packing and internal
components of the stuffing box 60 are taken out; it functions as an
axial retainer to prevent components from coming off. The split
casing 81, 82 allows the spring to preload the packing at the same
time as it prevents overloading the spring 83 should the
backpressure of the clean oil outflowing from the hole 75 vanish
while in operation. In the last-mentioned case, the axial thrust
would be transferred from the packing 5 to the casing, and thence
directly to the ring 84; from this ring, it would be further
propagated to the axial thrust bearing 18 via the axial middle
ledge 87. Thus, the thrust force would leave the lip seal 86
unaffected and free to cling firmly; nor
[0054] would it affect the seal ring 88, because the axial middle
ledge 87 transfers the thrust directly to that portion of the seal
ring which is strongest in the axial direction. The ring 88 stops
the clean lube oil from entering the upper chamber outside the
stuffing box 60, and the lip seal or oil seal 86 allows the clean
lube oil from the hole 75 to flow through, but prevents clean oil
and crude oil from flowing back to the bored ring 84. The lip or
oil seal 86 would not wear out, because in general, well pressure
only makes itself felt while the shaft is held stationary. In
operation, the clean lube oil to the packing is admitted through
the hole 75 and distributed between said seal ring 88 and the
packing 50 to also fill the annular chamber inside the split casing
81, 82. The lube oil pressure is maintained above the well pressure
to prevent dripping past the packing to the head, so that the
dripping is conveyed into the well and the contact between the
packing and the sleeve 61 can be kept in a suitable condition for
proper performance and a long life.
[0055] For servicing, the hole 74 is used for draining the stuffing
box 60 before disassembly, thereby avoiding undesirable splashes as
may foul the thrust bearing 31 and besmear the operator. In
addition, said hole allows the stuffing box 60 to be flushed clean
with its internal components and the packing in place before the
well is re-started.
[0056] The shaft locking clamp 65 with its self-centering jaws 66
is operated by first tightening down the screw 67 to urge the clamp
body 69 in a radial direction of the shaft 8 against the jaws 66
and cause the latter to close around the shaft 8 along normal
directions to the body direction of displacement. The contact
between the body and the jaws occurs across the inside taper 68 of
the body and the mating outside taper of the jaws 66. The jaws will
be guided in their movement toward each other by the taper 68, the
prismatic guide 95, and the pins 91 in the slot 92. At the end of
the clamp-down step, the springs 97 will move the jaws 66 away as
the body 69 is pushed back by turning the screw 67 in the opposite
direction.
[0057] Advantages of this invention are that: by having the
stuffing box 9 mounted below the thrust assembly 6 and the drive
components, full operational control of the rotating seals 20 or 50
and the gasket 24 is achieved; by having the thrust assembly placed
at the top, with the inner components of the stuffing box 9
removable through the top, replacement is quickly effected with
only a very short well shutdown; the operator can thus maintain a
comprehensive stock of spare parts that may include the thrust
assembly 6, and directly replace any worn out or failed items in a
wellhead.
[0058] In practicing the invention, the materials used, the
dimensions and construction details may be other than those
described hereinabove, yet be technical equivalents thereof,
without departing from the juridical domain of the present
invention. The tube 62/sleeve 61 combination could be manufactured
as a unit, although this would entail a more complicated
construction and be cost-intensive.
[0059] Thus, the clamp 10 or analogously the clamp 65 could be
provided, although less conveniently, as an independent unit rather
than as an attachment to the body 19 of the stuffing box 9.
[0060] An unrelated construction, as provided by the invention, of
the stuffing box 9 to the thrust assembly 6, although feasible,
would be less convenient. In fact, the more readily damaged items
in use would be the seals between rotating parts, oil seals or
packings, thrust bearing 31, and static seals 17 and 64. A separate
construction, although feasible, would impair simultaneous quick
replaceability of the parts when damaged, the rotating seals 20 or
50, the thrust assembly 6, and the gasket 24. On the other hand,
the shaft locking clamp 10 or 65 could be a separate construction,
unlike that shown in FIGS. 1, 5 and 8 having the clamp integral
with the body of the stuffing box.
* * * * *