Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02669870 2009-06-19
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ROTOR POLISHING SYSTEM
FIELD OF THE INVENTION
[0001] The present invention describes an improved method and apparatus for
polishing
rotors and specifically rotors for progressive cavity pumps (PCPs). In various
embodiments, the apparatus for polishing rotors is able to operate with a
sanding belt or
polishing wheel to achieve a desired finish. The apparatus for polishing
rotors is effective
at grinding and polishing progressive cavity pump (PCP) rotors used in
industrial
applications such as oil wells, gas wells or the like.
BACKGROUND OF THE INVENTION
[0002] During oil-well production, in-line pumps such as progressive cavity
pumps (PC
pumps or PCPs) are used to pump oil from the well bore to the surface. A
progressive
cavity pump system includes a surface driven rotor mounted with a downhole
stator that
is rotationally secured to production casing so as to prevent rotation of the
stator in
response to the rotation of the rotor. The shapes of the rotor and stator form
a series of
sealed cavities within the stator. As the rotor is turned, the cavities
progress to move
fluid from the intake to the discharge end of the pump.
[0003] As is well known, a surface driven rotor must be tightly encased within
a
downhole stator for a PC pump to form sealed cavities and result in a positive
displacement flow. The rotation of the rotor against the stator causes the
erosion of
material from the rotor resulting in degradation of the cavities' seal. A
reduced seal
results in a reduction of the positive displacement flow rate and pressure at
the
discharge end of the pump.
[0004] Furthermore, oil is generally obtained from the geosphere and wells are
often
drilled through clay, rock, sand or the like (hereafter referred to as
"mineral matter"). As a
result, when oil is pumped from the well bore to the surface, fragments of
mineral matter
are incorporated into the oil stream resulting in an abrasive fluid. The
abrasive fluid
enters the PC pump and contacts the surface of the rotor causing further
erosion of
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material on the rotor. Furthermore, fragments of mineral matter may become
caught
between the rotor and stator. As the rotor rotates against the stator, these
fragments of
mineral matter cause even further erosion of the material on the rotor.
Similarly, the
erosion of the rotor caused by mineral matter will reduce the seal of the
cavities resulting
in a decreased positive flow rate and pressure at the discharge end of the
pump.
[0005] Generally, rotors for PC pumps are expensive to manufacture and
replace.
Preferably, a worn rotor is repaired when the positive flow rate and pressure
at the
discharge end of the pump have decreased to a specified level.
[0006] A common method of repairing a worn PCP rotor is chromium
electroplating. The
process of chromium electroplating may include degreasing to remove heavy
soiling,
manual cleaning to remove traces of dirt or impurities, one or more
pretreatments,
submersion in a vat containing chromium ions and the subsequent application of
an
electrical current to the rotor and chromium vat. The rotor is left in the vat
with the
electrical current until the desired thickness of chromium is achieved.
Finally, the rotor is
removed and may be subjected to one or more post treatments.
[0007] During operation, one or more sections of a rotor may incur more wear
than other
sections of the rotor. As a result these sections may require different
thicknesses of
chromium to be plated. Chromium plating is an electrochemical process that is
difficult to
control with respect to the thickness of chromium along the length of the
rotor.
Furthermore, chromium plating may also result in small imperfections on the
surface of
the rotor. Therefore it is desirable to plate a rotor with chromium so that
the entire rotor is
a minimum thickness before grinding to remove excess chromium. Finally, a
rotor is
polished to ensure a consistent finish as required by the specifications of a
PCP.
[0008] Schuler Incorporated (Schuler), a provider of metal forming products
headquartered in Canon, Michigan, offers highly automated machinery to grind
and
polish a PCP rotor with a high level of precision. Schuler's technology can
repair a PC
pump rotor to an exact specification, however there is generally a high cost
associated
with the purchase, operation and maintenance of the automated machinery.
[0009] A review of the prior art indicates that while various systems for
polishing rotors
have been provided in the past, there continues to be a need for new designs
of such
systems that provide improvements over these past systems. In particular,
there is a
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need for a highly effective semi-automatic polishing system that enables PCP
rotors to
be polished in a cost-effective manner.
SUMMARY OF THE INVENTION
[0010] In accordance with the invention, there is provided a method and
apparatus for
polishing rotors and specifically rotors for progressive cavity pumps (PCPs).
[0011] More specifically, there is provided a progressive cavity pump (PCP)
rotor
polishing system comprising:
a frame;
a headstock assembly and tailstock assembly operatively connected to the
frame, the headstock assembly and tailstock assembly for operatively
supporting a PCP
rotor and enabling rotation of a PCP rotor mounted within the headstock and
tailstock
assemblies; and
a saddle assembly operatively connected to the frame, the saddle assembly
moveable along the frame and along the PCP rotor when mounted within the
headstock
and tailstock assemblies, the saddle assembly including a polishing system for
engagement against the PCP rotor, wherein the polishing system is vertically
and
rotationally moveable with respect to the PCP rotor.
[0012] In one embodiment of the invention, the frame of the progressive cavity
pump
rotor polishing system includes a rail system operatively supporting the
saddle assembly
and polishing system.
[0013] In another embodiment, the rail system of the progressive cavity pump
rotor
polishing system is a double rail and the saddle assembly includes a wheel and
bearing
system mounted on the double rail.
[0014] In yet another embodiment, the saddle assembly of the progressive
cavity pump
rotor polishing system includes a vertical support member operatively
connecting the
polishing system to the saddle assembly, wherein the vertical support member
enables
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vertical and rotational movement of the polishing system with respect to the
saddle
assembly.
[0015] Specifically, the polishing system of the progressive cavity pump rotor
polishing
system may be a belt sander or a polishing wheel.
[0016] In one embodiment of the invention, the wheel and bearing system of the
progressive cavity pump rotor polishing system includes at least four wheel
pairs for
engagement with the double rail wherein each wheel pair respectively engage
with an
upper surface and lower surface of one rail and wherein the wheel pairs are
horizontally
displaced with respect to one another to provide vertical, horizontal and
torsional stability
to the saddle system relative to the double rail.
[0017] In another embodiment of the invention, the progressive cavity pump
rotor
polishing system further comprises a control system on the saddle assembly for
operative control of the polishing system including start, stop and speed; and
the
headstock assembly including start, stop and speed.
[0018] In a further embodiment of the invention, the polishing system includes
a variable
frequency drive motor and the control system includes a display for providing
a pressure
reading of the relative force being applied to a rotor during polishing.
[0019] In yet another embodiment of the invention, the progressive cavity pump
rotor
polishing system further comprises a lower support rail enabling selective
positioning of
the tailstock assembly at a selected distance from the headstock assembly. The
lower
support rail may include rollers rotationally supporting a PCP rotor on the
lower rail.
BRIEF DESCRIPTION OF THE FIGURES
[0020] The invention is described with reference to the accompanying figures
in which:
FIG. 1 is an isometric view of an Apparatus for polishing rotors in accordance
with a first embodiment of this invention showing a frame assembly, a
headstock
assembly, a tailstock assembly, a saddle assembly and a polishing system.
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FIG. 2 is a front view of an Apparatus for polishing rotors in accordance with
a
first embodiment of this invention showing a frame assembly, a headstock
assembly, a tailstock assembly, a saddle assembly and a polishing system.
FIG. 3 is an end view of an Apparatus for polishing rotors in accordance with
a
first embodiment of this invention showing a headstock support member, a frame
assembly and a headstock assembly.
FIG. 4 is an isometric view of a headstock assembly in accordance with a first
embodiment of this invention.
FIG. 5 is an end view of a saddle assembly, a tailstock assembly, and a
polishing
system in accordance with a first embodiment of this invention.
FIG. 6 is an isometric view of a saddle assembly and polishing system in
accordance with a first embodiment of this invention.
FIG. 6A is a side view of a saddle assembly, a power head assembly and a
polishing system in accordance with a first embodiment of this invention.
FIG. 6B is a top view of a saddle assembly, a power head assembly and a
polishing system in accordance with a first embodiment of this invention.
FIG. 7 is an isometric view of a tailstock assembly in accordance with a first
embodiment of this invention.
FIG. 8 is an isometric view of an Apparatus for polishing rotors in accordance
with a second embodiment of this invention.
FIG. 9 is a front view of an Apparatus for polishing rotors in accordance with
a
second embodiment of this invention.
FIG. 10 is an end view of an Apparatus for polishing rotors in accordance with
a
second embodiment of this invention.
FIG. 11 is an isometric view of the saddle assembly in accordance with a
second
embodiment of this invention.
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FIG. 12 is a schematic view of the operator control panel in accordance with
one
embodiment of the invention.
DETAILED DESCRIPTION
Overview
(0021] With reference to the figures, an Apparatus for Polishing Rotors (AFPR)
10 for
use in industrial applications is described. The system generally includes a
frame
assembly 12, a saddle assembly 200, a headstock assembly 300, a tailstock
assembly
400 and an operator control panel 201, as best shown in FIGS. 1 and 2.
[0022] In operation, a PCP rotor (not shown) is mounted between the headstock
assembly 300 and the tailstock assembly 400 such that the PCP rotor can rotate
between the headstock and tailstock assemblies. The saddle assembly is
operable to
lower a polishing system against the PCP rotor such that the surface of the
PCP rotor
can be polished. In addition, the saddle assembly can be moved along the
length of the
PCP rotor which in conjunction with rotation of the PCP rotor enables the
polishing
system to come into contact with all external surfaces of the PCP rotor.
Frame Assembly
[0023] Referring to FIG. 1, the frame assembly 12 generally includes at least
one
polisher support member 14, a headstock support member 16, a rail 18, an I-
beam 20
and an outer protective skin 22. The polisher support member 14 and the
headstock
support member 16 generally provide structural support for the AFPR.
[0024] The rail 18 preferably includes two diamond shaped beams mounted
generally
horizontally beneath the top(s) of the polisher support member(s) 14 as best
shown by
FIG. 3. The I-beam 20 provides a support rail for the tailstock assembly
allowing the
tailstock assembly to slide along the length of the AFPR to accommodate rotors
of
different lengths.
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[0025] The outer protective skin 22 is generally a sheet metal covering that
contains
shavings, sparks or the like from within the AFPR. The outer protective skin
is mounted
on the polisher support member(s) 14 and headstock support member 16 and is
generally located at the rear of the AFPR.
Saddle Assembly
[0026] In a first embodiment, as best shown in FIG. 5 and FIG. 6, the saddle
assembly
200 generally includes a saddle frame 203, a power head assembly 210 and a
polishing
system 213.
Saddle Frame
[0027] The saddle frame 203 preferably includes at least one U-shaped member
204, at
least one saddle wheel 205, at least one horizontal saddle rail 206, at least
one saddle
tube 208 and a saddle platform 209.
[0028] In the preferred embodiment, there are two U-shaped members 204 that
are
connected by four horizontal saddle rails 206. Eight saddle wheels 205 are
mounted on
the horizontal saddle rails 206 in a generally box-like arrangement for
sliding
engagement with the rail 18 such that the saddle assembly can move
horizontally along
the length of the rail 18 with directional stability while preventing motion
in the binormal
and tangential directions. There are preferably two saddle tubes 208 mounted
to the
undersides of the two U-shaped members 204. Two saddle sleeves 207 are
slidingly
engaged with the saddle tubes 208 and connected by the saddle platform 209.
The
saddle platform 209 and saddle sleeves 207 can slide as one unit horizontally
along the
length of the saddle tubes 208.
[0029] A rack 204c, pinion 204b and corresponding rail drive motor 204 is
configured to
the saddle assembly and frame 12 to enable controlled movement of the saddle
assembly with respect to the frame.
Power Head Assembly
[0030] As best shown in FIG. 6A and FIG. 6B, the power head assembly 210 is
affixed
to the underside of the saddle platform 209 and generally includes a power
head motor
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211, a power head belt 211 a, a power head pulley 211 b, a power head shaft
211 c, a
power head support member 212a and a power head lifting member 212b.
[0031 ] The power head motor 211 drives the power head pulley 211 b to rotate
in a
clockwise or counterclockwise direction. The power head belt 211 a runs around
the
power head pulley 211 b and the power head shaft 211 c such that the rotation
of the
power head pulley is transferred through the power head belt to cause vertical
movement of the power head shaft via an internal threaded shaft and nut (not
shown).
Polishing System
[0032] The polishing system is mounted laterally on the power head assembly
210 such
that the polishing system can move vertically by means of the vertical
movement of the
power head assembly 210, and horizontally by means of the saddle sleeve 207
and
saddle platform 209 sliding along the saddle tube 208. In one embodiment, the
polishing
system is a sander 213, as shown in FIG. 5. In a second embodiment, the
polishing
system is a polishing wheel, as best shown in FIG. 11.
Polishing Sander
[0033] In one embodiment, the polishing system is a sander 213, as best shown
in FIG.
6A. The sander 213 generally consists of a sander motor 214, a sander drive
pulley 215,
a sander idler pulley 216, a sander belt 217, a sander belt guard 218 and a
belt pressure
cylinder 219.
[0034] The sander belt encircles the sander drive pulley 215 and the sander
idler pulley
216. The sander motor 214 is attached to the sander drive pulley 215, and
drives the
sander drive pulley which frictionally engages the sander belt 217 and causes
the
rotation of the sander belt about the sander idler pulley 216. The sander
motor 214 is
preferably a variable frequency drive (VFD) to allow for the sander belt to
operate at
various speeds. The sander belt guard 218 protects an operator from any debris
coming
off the sander belt while in operation and protects the sander belt from
coming into
contact with an external object, such as an operator or another machine. The
sander belt
pressure cylinder 219 partially supports the sander 213 to allow an operator
to manually
apply a more even pressure to the sander as explained in greater detail below.
The
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sander 213 may further include an appropriate handle (not shown) to allow an
operator
to move the sander into and out of an operative position.
[0035] As is well known to those of skill in the art, the sander belt 217
consists of a loop
of sandpaper. The sandpaper is a coated abrasive generally consisting of a
backing, an
abrasive and an adhesive to bind the abrasive to the backing. Backings may
consist of
paper, cloth, biaxially-oriented polyethylene terephthalate polyester film
(Mylar) or the
like. Abrasives generally consist of one or a mix of the following: glass,
flint, garnet,
emery, aluminum oxide, silicon carbide, alumina-zirconia, chromium oxide,
ceramic
aluminum oxide or the like. Adhesives generally consist of glue or the like.
The sander
belt 217 is sized to be frictionally engaged by the sander drive pulley 215
and the sander
idler pulley 216.
Polishing Wheel
[0036] In a second embodiment, the polishing system 213 consists of a
polishing wheel
220 and a polishing wheel motor 221 that is attached to the power head 210 as
shown in
FIG. 11. The polishing wheel motor 221 turns the polishing wheel 220 and a
polishing
wheel cover 222 protects the polishing wheel 220 and the operator, similar to
the
protection the sander belt guard 218 provides in the first embodiment. The
polishing
wheel motor 221 is preferably a variable frequency drive (VFD) to allow for
various
speeds for the polishing wheel. A handle (not shown) is preferably provided to
allow the
operator to move the system into and out of an operative position.
[0037] The polishing wheel 220 may be composed of a variety of materials to
provide
different finishes for polishing the rotor 30. Materials may include, but are
not limited to,
felt, canvas or a fine abrasive. A polishing compound such as TripoliTM or
RougeTM may
also be used as required.
Headstock Assembly
[0038] The headstock assembly 300 is mounted on the headstock support member
16
at one end of the frame assembly 12 and generally includes a chuck 302, a
sheave 306,
one or more chuck belts 310, a headstock motor 308, and a chuck housing 304
that
forms the support means for the other components of the headstock assembly, as
best
shown in FIG. 4. When the AFPR 10 is in use, one end of the PCP rotor may be
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attached to the chuck 302, which causes the PCP rotor to rotate while
remaining in a
horizontal plane.
[0039] The chuck belt(s) 310 is frictionally engaged in a loop around the
headstock
motor 308 and the sheave 306, and the sheave 306 is attached to the chuck 302.
In
operation, the rotation of the headstock motor 308 drives the rotation of the
chuck belt(s)
310, the sheave 306, and the chuck 302. The headstock motor 308 may be
Variable
Frequency Drive (VFD) to allow the chuck 302 and PCP rotor to rotate at
different
speeds as desired.
Tailstock Assembly
[0040] Referring to FIG. 1, the tailstock assembly 400 is mounted at the
opposite end of
the frame assembly 12 to the headstock assembly 300 and is designed to hold
one end
of the PCP rotor in place while the AFPR is in operation. As shown in FIG. 7,
the
tailstock assembly 400 generally includes a ram 402, a ram sleeve 403, a
handwheel
404 and a pylon 406, as known to those of skill in the art. The pylon 406 is
mounted on
the I-beam 20 and can move horizontally along the I-beam 20 to allow
horizontal
positioning of the tail stock assembly 400 as required to fit the length of
the PCP rotor
being polished. The ram sleeve 403 is mounted to the top of the pylon 406 and
the ram
402 can move horizontally within the ram sleeve 403 by turning the handwheel
404 to
aid in the operative engagement of the ram 402 with the PCP rotor.
Rotor Rollers
[0041] In a further embodiment shown in FIG. 8, the headstock assembly 300,
tail stock
assembly 400 and I-Beam 20 may be replaced by one or more sets of rotor
rollers 32
located along the bottom length of the frame that support a rotor 30. The sets
of rotor
rollers 32 rotate passively as the polishing system is frictionally engaged
with a rotor.
Operator Control Panel
[0042] In a preferred embodiment, an operator control panel 201 is mounted on
the
saddle assembly 200. The operator control panel 201 is best shown in FIG. 12.
The
operator control panel will provide appropriate controls to enable the
operator located at
the polishing system to effectively control operation of the system. In
particular, the
control panel will preferably include appropriate controls to operate the
headstock motor
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308 to control the rotation of the PCP rotor (speed and direction), the
polisher motor 214
or polishing wheel motor 221 (speed), the speed of traverse of the polishing
system
along the rails as well as vertical movement of the polishing system. An
emergency stop
button 500 will preferably be provided to allow an operator to shut-down the
system and
may include prohibiting means as understood to those skilled in the art to
rapidly slow
and subsequently stop the rotation of the headstock assembly 300, sander belt
217 or
polishing wheel 220 and the translational movement of the saddle 203 or power
head
210.
[0043] As shown in FIG. 12, the operator control panel 201 may specifically
include
controls for the headstock assembly 300 such as start 502, stop 503, forward
504,
reverse 505 and speed 506. The speed 506 control may control the speed of the
variable frequency drive (VFD) motor.
[0044] In addition, the operator control panel may further include controls
for the sander
motor or polishing wheel motor including start 508 and stop 509 and traverse
speed 510
and traverse direction 510a, 510b.
[0045] In another embodiment, the control panel 201 may include a display,
touch
screen display or the like 511. In a preferred embodiment, the display will
indicate the
relative pressure an operator is applying to the polisher that may be measured
from the
operating frequency of the motor. Other control parameters may also be
displayed.
Operation of the AFPR
[0046] In operation, the operator places the rotor 30 in the AFPR 10 using an
appropriate lifting device (not shown) and positions one end of the rotor 30
at the
headstock assembly 300 for operative attachment to the chuck 302. The tail
stock
assembly 400 is moved horizontally along the I-Beam 20 until the ram 402
contacts the
rotor 30. The chuck 302 is tightened to secure the rotor in place and
subsequently the
handwheel 404 is turned until the ram 402 frictionally engages the rotor 30,
allowing
rotational movement of the rotor but preventing any horizontal or vertical
movement.
[0047] Using the operator control panel 201, the operator sets the chuck 302
of the
headstock assembly 300 to rotate, causing rotation of the rotor 30. The
operator may
rotate the rotor whenever the operator requires the rotor to rotate, or he/she
may set the
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chuck to rotate continuously at any given speed or to rotate at given
intervals. The
operator may adjust the rotation of the chuck to provide an even and
consistent polish to
the rotor.
[0048] The saddle assembly 200 may be moved laterally along the rail 18 to
position the
power head assembly 210 and polishing system 213 above any given section of
the
rotor 30. The saddle assembly 200 may be moved along the rail 18 with the aid
of the
rail drive motor.
[0049] The power head assembly 210 is moved vertically by the power head motor
211
of the polishing system 213 in a direction binormal to the rail 18 and saddle
tube 208.
[0050] The pivoting vertical and horizontal pivoting motion of the power head
is
generally caused by the operator applying up/down and/or side to side pressure
to one
or more handles (not shown) located on the polishing system 213.
[0051] The polishing system 213 can be moved horizontally at a right angle to
the rail 18
by means of the saddle sleeve 207 moving on the saddle tube 208, as previously
described. This horizontal movement of the saddle sleeve 207 is generally
accomplished
by the operator manually applying pressure to the handle(s) on the polishing
system
213. In one embodiment where the polishing system is a sander 213a, the
operator
moves the sander belt 217 down towards the rotor 30 by means of the handle(s)
on the
polishing system. When the sander belt 217 touches the rotor 30, the movement
of the
abrasive on the sander belt causes the removal of chrome from the rotor 30.
The
operator may apply physical pressure on the polishing system as required to
achieve the
desired thickness of finish. Generally, the more pressure that is applied, the
more
chrome is removed.
[0052] In the second embodiment where the polishing system is a polishing
wheel 220,
the operator moves the polishing wheel 220 towards the rotor 30 with the
handle(s). The
operator may apply a polishing compound to the polishing wheel 220 or rotor 30
to aid in
the polishing of the rotor. When the polishing wheel 220 touches the rotor 30,
the
rotational movement of the wheel causes the polishing of the rotor. The
operator may
apply physical pressure as required to achieve a desired finish.
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[0053] In one embodiment, the rotor 30 may rotate slowly as the operator
operates a
sanding belt or polishing wheel. Alternatively, the operator may sand or
polish an entire
side of a rotor before rotating the chuck a few degrees and polishing another
side of the
same rotor.
[0054] To ensure the rotor is polished to desired dimensions, the operator
generally
uses a measurement device such as calipers, electronic lasers or the like to
determine
the thickness of the rotor. The operator may then make a decision to grind or
polish an
area more or less thoroughly.
[0055] The present system is advantaged over previous polishing systems by
providing
an effective and efficient polishing system that enables the rapid polishing
of PCP rotors
to desired finishes and tolerances. For example, a typical 20 foot PCP rotor
that has
been chrome plated may be polished to specification (typically 2 thousandths
of an
inch) in approximately less than 1 hour. A large power rotor of 20-25 feet
could be
polished in approximately 2.5 hours. Prior art systems would take
approximately 30
hours to polish a large power rotor. As well as being substantially faster
than prior art
systems, the capital cost of the present semi-automatic system is much lower
than fully
automatic systems.
[0056] Although the invention has been described with reference to a
particular
arrangement of parts, features and the like, these are not intended to exhaust
all
possible arrangements or features, and indeed many other modifications and
variations
will be ascertainable to those of skill in the art.
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