Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02954177 2017-01-10
RECIPROCATING ROD PUMPING UNIT
BACKGROUND OF THE DISCLOSURE
Field of the Disclosure
The present disclosure generally relates to a reciprocating rod pumping unit.
Description of the Related Art
To obtain hydrocarbon fluids, a wellbore is drilled into the earth to
intersect a
productive formation. Upon reaching the productive formation, an artificial
lift system is
often necessary to carry production fluid (e.g., hydrocarbon fluid) from the
productive
formation to a wellhead located at a surface of the earth. A reciprocating rod
pumping unit
is a common type of artificial lift system.
The reciprocating rod pumping unit generally includes a surface drive
mechanism,
a sucker rod string, and a downhole pump. Fluid is brought to the surface of
the wellbore
by reciprocating pumping action of the drive mechanism attached to the rod
string.
Reciprocating pumping action moves a traveling valve on the pump, loading it
on the
down-stroke of the rod string and lifting fluid to the surface on the up-
stroke of the rod
string. A standing valve is typically located at the bottom of a barrel of the
pump which
prevents fluid from flowing back into the well formation after the pump barrel
is filled and
during the down-stroke of the rod string. The rod string provides the
mechanical link of
the drive mechanism at the surface to the pump downhole.
One such surface drive mechanism is known as a long-stroke pumping unit. The
long-stroke pumping unit includes a counterweight which travels along a tower
during
operation thereof. Should the sucker rod string fail, there is a potential
that the
counterweight assembly will free fall and damage various parts of the pumping
unit as it
crashes under the force of gravity. The sudden acceleration of the
counterweight
assembly may not be controllable using the existing long-stroke pumping unit.
SUMMARY OF THE DISCLOSURE
The present disclosure generally relates to a braking system for a
reciprocating
rod pumping unit. In one embodiment, a reciprocating rod pumping unit
includes: a tower;
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a counterweight assembly movable along the tower; a drum connected to an upper
end
of the tower and rotatable relative thereto; a belt having a first end
connected to the
counterweight assembly, extending over the drum, and having a second end
connectable
to a rod string; a prime mover for reciprocating the counterweight assembly
along the
tower; a sensor for detecting sudden acceleration of the counterweight
assembly due to
failure of the rod string; at least one of: a braking system for halting free-
fall of the
counterweight assembly; and an arrestor system for absorbing kinetic energy of
the falling
counterweight assembly; and a controller in communication with the sensor and
operable
to activate the braking or arrestor system in response to detection of the
sudden
acceleration.
In one embodiment, a reciprocating rod pumping unit includes a tower; a
counterweight assembly movable along the tower; a drum connected to an upper
end of
the tower and rotatable relative thereto; a belt having a first end connected
to the
counterweight assembly, extending over the drum, and having a second end
connectable
to a rod string; a prime mover for reciprocating the counterweight assembly
along the
tower; a sensor for detecting a condition of the pumping unit; a brake system
for halting
free-fall of the counterweight assembly; and a controller in communication
with the sensor
and operable to activate the brake system in response to detection of the
faulty condition
of the pumping unit. In one example, the sensor is selected from the group
consisting of
a speed sensor for detecting a speed of the belt; a cycle sensor for detecting
a cycle of
the belt; a load sensor for detecting a change in load on the drum; a belt
alignment sensor
for detecting an alignment of the belt; a vibration sensor for detecting a
vibration of the
tower; and combinations thereof.
In another embodiment, a reciprocating rod pumping unit includes a tower; a
counterweight assembly movable along the tower; a drum connected to an upper
end of
the tower and rotatable relative thereto; a belt having a first end connected
to the
counterweight assembly, extending over the drum, and having a second end
connectable
to a rod string; a prime mover for reciprocating the counterweight assembly
along the
tower; a sensor for detecting a condition of the pumping unit; and a
controller in
communication with the sensor and operable to cause the counterweight assembly
to
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stop in response to the detected condition. In one example, the sensor is
selected from
the group consisting of a speed sensor for detecting a speed of the belt; a
cycle sensor
for detecting a cycle of the belt; a load sensor for detecting a change in
load on the drum;
a belt alignment sensor for detecting an alignment of the belt; a vibration
sensor for
detecting a vibration of the tower; and combinations thereof.
In another embodiment, a reciprocating rod pumping unit includes a tower; a
counterweight assembly movable along the tower; a drum connected to an upper
end of
the tower and rotatable relative thereto; a belt having a first end connected
to the
counterweight assembly, extending over the drum, and having a second end
connectable
to a rod string; a prime mover for reciprocating the counterweight assembly
along the
tower; a lubrication system for applying lubricant to at least one of a chain,
a bearing, and
combinations thereof; at least one of a lubrication sensor for detecting an
amount of
lubricant in the lubrication system, a pressure sensor for detecting a
pressure in the
lubrication system, and a flow meter for measuring a flow rate of the
lubricant; and a
controller in communication with the at least one of the lubrication sensor,
the pressure
sensor, and the flow meter, and operable to cause the counterweight assembly
to stop.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the present
disclosure
can be understood in detail, a more particular description of the disclosure,
briefly
summarized above, may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however, that the
appended
drawings illustrate only typical embodiments of this disclosure and are
therefore not to be
considered limiting of its scope, for the disclosure may admit to other
equally effective
embodiments.
Figures 1A and 1B illustrate a reciprocating rod pumping unit, according to
one
embodiment of the present disclosure. Figure 10 illustrates a braking system
of the
reciprocating rod pumping unit.
Figure 1D illustrates an accelerometer of the
reciprocating rod pumping unit.
Figure 2A is a partial perspective view of an exemplary carriage coupled to a
chain
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=
and a counterweight.
Figure 2B is a perspective view of the carriage of Figure 2A.
Figures 3A-3E illustrate another embodiment of a carriage. Figure 3A is a
perspective view of the carriage. Figure 3B is a cross-sectional view of the
carriage.
Figure 3C is a cross-sectional view of the bushing and bushing shaft. Figures
3D-3E are
different perspective views of the carriage.
Figure 4 illustrates an exemplary brake system coupled to a reducer.
Figures 5A-5E show an exemplary embodiment of a pillow block equipped with a
load cell.
Figure 6 shows an exemplary location of a nozzle of the lubrication system.
DETAILED DESCRIPTION
Figures 1A and 1B illustrate a reciprocating rod pumping unit 1k, according to
one
embodiment of the present disclosure. The reciprocating rod pumping unit 1k
may be
part of an artificial lift system 1 further including a rod string lr and a
downhole pump (not
shown). The artificial lift system 1 may be operable to pump production fluid
(not shown)
from a hydrocarbon bearing formation (not shown) intersected by a well 2. The
well 2 may
include a wellhead 2h located adjacent to a surface 3 of the earth and a
wellbore 2w
extending from the wellhead. The wellbore 2w may extend from the surface 3
through a
non-productive formation and through the hydrocarbon-bearing formation (aka
reservoir).
A casing string 2c may extend from the wellhead 2h into the wellbore 2w and be
sealed therein with cement (not shown). A production string 2p may extend from
the
wellhead 2h and into the wellbore 2w. The production string 2p may include a
string of
production tubing and the downhole pump connected to a bottom of the
production tubing.
The production tubing may be hung from the wellhead 2h.
The downhole pump may include a tubular barrel with a standing valve located
at
the bottom that allows production fluid to enter from the wellbore 2w, but
does not allow
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the fluid to leave. Inside the pump barrel may be a close-fitting hollow
plunger with a
traveling valve located at the top. The traveling valve may allow fluid to
move from below
the plunger to the production tubing above and may not allow fluid to return
from the
tubing to the pump barrel below the plunger. The plunger may be connected to a
bottom
of the rod string 1r for reciprocation thereby. During the upstroke of the
plunger, the
traveling valve may be closed and any fluid above the plunger in the
production tubing
may be lifted towards the surface 3. Meanwhile, the standing valve may open
and allow
fluid to enter the pump barrel from the wellbore 2w. During the downstroke of
the plunger,
the traveling valve may be open and the standing valve may be closed to
transfer the fluid
from the pump barrel to the plunger.
The rod string 1r may extend from the reciprocating rod pumping unit 1k,
through
the wellhead 2h, and into the wellbore 2w. The rod string 1r may include a
jointed or
continuous sucker rod string 4s and a polished rod 4p. The polished rod 4p may
be
connected to an upper end of the sucker rod string 4s and the pump plunger may
be
connected to a lower end of the sucker rod string, such as by threaded
couplings.
A production tree (not shown) may be connected to an upper end of the wellhead
2h and a stuffing box 2b may be connected to an upper end of the production
tree, such
as by flanged connections. The polished rod 4p may extend through the stuffing
box 2b.
The stuffing box 2b may have a seal assembly (not shown) for sealing against
an outer
surface of the polished rod 4p while accommodating reciprocation of the rod
string 1r
relative to the stuffing box.
The reciprocating rod pumping unit 1k may include a skid 5, a prime mover,
such
as an electric motor 6, a rotary linkage 7, a reducer 8, one or more ladders
and platforms
(not shown), a standing strut (not shown), a crown 9, a drum assembly 10, a
load belt 11,
one or more wind guards (not shown), a counterweight assembly 12, a carriage
13, a
chain idler 14, a tower 15, a chain 16, a hanger bar 17, a drive sprocket 18,
a tower base
19, a foundation 20, a control system 21, and a braking system 22. The control
system
21 may include a programmable logic controller (PLC) 21p, a hydraulic power
unit (HPU)
21h, a motor driver 21m, a tachometer 21t, a load cell 21d, and a sensor, such
as
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accelerometer 21a.
The foundation 20 may support the pumping unit 1k from the surface 3 and the
skid 5 and tower base 19 may rest atop the foundation. The PLC 21p and HPU 21h
may
be mounted to the skid 5 and/or the tower 15. Lubricant, such as refined
and/or synthetic
oil 23, may be disposed in the tower base 19 such that the chain 16 is bathed
therein as
the chain orbits around the chain idler 14 and the drive sprocket 18.
The electric motor 6 may be a one or more, such as three phase, electric
motor.
The motor driver 21m may be variable speed including a rectifier and an
inverter. The
motor driver 21m may receive a three phase alternating current (AC) power
signal from
a three phase power source, such as a generator or transmission lines. The
rectifier may
convert the three phase AC power signal to a direct current (DC) power signal
and the
inverter may modulate the DC power signal into a three phase AC power signal
at a
variable frequency for controlling the rotational speed of the motor 6. The
PLC 21p may
supply the desired rotational speed of the motor 6 to the motor driver 21m via
a data link.
Alternatively, the prime mover may be an internal combustion engine fueled by
natural gas available at the well site.
The motor 6 may include a stator disposed in a housing mounted to the skid 5.
The rotary linkage 7 may torsionally connect a rotor of the motor 6 to an
input shaft of the
reducer 8 and may include a sheave connected to the rotor, a sheave connected
to the
input shaft, and a V-belt connecting the sheaves. The reducer 8 may be a
gearbox
including the input shaft, an input gear connected to the input shaft, an
output gear
meshed with the input gear, an output shaft connected to the output gear, and
a gear
case mounted to the skid 5. The output gear may have an outer diameter
substantially
greater than an outer diameter of the input gear to achieve reduction of
angular speed of
the motor 6 and amplification of torque of the motor. The drive sprocket 18
may be
torsionally connected to the output shaft of the reducer 8. The tachometer 21t
may be
mounted on the reducer 8 to monitor an angular speed of the output shaft and
may report
the angular speed to the PLC 21p via a data link.
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The chain 16 may be meshed with the drive sprocket 18 and may extend to the
idler 14. The idler 14 may include an idler sprocket 14k meshed with the chain
16 and an
adjustable frame 14f mounting the idler sprocket to the tower 15 while
allowing for rotation
of the idler sprocket relative thereto. The adjustable frame 14f may vary a
height of the
idler sprocket 14k relative to the drive sprocket 18 for tensioning the chain
16.
The carriage 13 may longitudinally connect the counterweight assembly 12 to
the
chain 16 while allowing relative transverse movement of the chain relative to
the
counterweight assembly 12. The carriage 13 may include a block base 13b, one
or more
(four shown) wheels 13w, a track 13t, and a swivel knuckle 13k. The track 13t
may be
connected to a bottom of the counterweight assembly 12, such as by fastening.
The
wheels may be engaged with upper and lower rails of the track 13t, thereby
longitudinally
connecting the block base 13b to the track 13t while allowing transverse
movement
therebetween. The swivel knuckle 13k may include a follower portion assembled
as part
of the chain 16 using fasteners to connect the follower portion to adjacent
links of the
chain. The swivel knuckle 13k may have a shaft portion extending from the
follower
portion and received by a socket of the block base 13b and connected thereto
by bearings
(not shown) such that swivel knuckle 13k may rotate relative to the block base
13b.
Figures 2A and 2B illustrate another embodiment of a carriage 213. Figure 2A
is
a partial perspective view of the carriage 213 coupled to the chain 16 and the
counterweight 12 and located near the idler sprocket 14k. Figure 2B is a
perspective
view of the carriage 213. The carriage 213 may longitudinally connect the
counterweight
assembly 12 to the chain 16 while allowing relative transverse movement of the
chain 16
relative to the counterweight assembly 12. The carriage 213 may include a
block base
213b, one or more (eight shown) slide bearings 213s, two tracks 213t, and a
swivel
knuckle 213k. Upper and lower tracks 213t may be connected to the
counterweight
assembly 12, such as by fastening. The sliding bearings 213s may engage the
rails of
the upper and lower tracks 213t, thereby longitudinally connecting the block
base 213b
to the tracks 213t while allowing transverse movement between the
counterweight 12 and
the chain 16. As shown, the four slide bearings 213s engage the rail of the
upper track
213t, and four slide bearings 213s engage the rail of the lower track 213t.
However, it is
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contemplated that either or both tracks 213t may have one, two, four, or more
slide
bearings 213s engaged therewith. In one embodiment, the slide bearings 213s
engage
the tracks 213t without lubricant therebetween. Each slide bearing 213s may
include a
metal plate 213p engaged with the rail of the tracks 213t. In one embodiment,
the metal
plate 213p includes bronze and/or graphite and a steel backing. As shown, a
bearing
guide 213g is provided on the edge of the slide bearings 213s to keep the
slide bearings
213s on the tracks 213t.
Figures 3A-3E illustrate another embodiment of a carriage 613. The carriage
613
may include bushings 613s in place of the sliding bearings 213s. Figure 3A is
a
perspective view of the carriage 613, and Figure 3B is a cross-sectional view
of the
carriage 613. Figure 3C is a cross-sectional view of the bushing 613s and
bushing shaft
613t. Figures 3D-3E are different perspective views of the carriage 613. The
carriage
613 may longitudinally connect the counterweight assembly 12 to the chain 16
while
allowing relative transverse movement of the chain 16 relative to the
counterweight
assembly 12. The carriage 613 may include a block base (also referred to as
"housing")
613b, one or more (eight shown) bushings 613s, two tracks that are similar to
tracks 13t,
and a swivel knuckle 613k. Upper and lower tracks may be connected to the
counterweight assembly 12, such as by fastening. The swivel knuckle 613k is
rotationally
coupled to the housing 613b using one or more bearings 613h, as shown in
Figure 3B.
The chain 16 may be coupled to the swivel knuckle 613k via the chain pin 613p.
The
chain pin 613p may be attached to the swivel knuckle 613k using a pin retainer
613r. The
bushings 613s are rotationally coupled to the housing 613b via a bushing shaft
613t. The
bushing shaft 613t may extend across the housing 613b to support a bushing
613s on
each side of the housing 613b. Referring to Figure 3C, one or more bearing
assemblies
613j are used to facilitate relative rotation between the bushings 613s and
the bushing
shaft 613t. The bushings 613s may engage the rails of the upper and lower
tracks,
thereby longitudinally connecting the housing 613b to the tracks while
allowing transverse
movement between the counterweight 12 and the chain 16. As shown, a bushing
guide
613g is provided on the edge of the bushings 613s to keep the bushings 613s on
the
tracks. As shown, the four bushings 613s engage the rail of the upper track,
and four
bushings 613s engage the rail of the lower track. However, it is contemplated
that either
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or both tracks may have one, two, four, or more bushings 613s engaged
therewith. In
one embodiment, the bushings 613s engage the tracks 613t without lubricant
therebetween.
Referring back to Figures 1A and 1B, the counterweight assembly 12 may be
disposed in the tower 15 and longitudinally movable relative thereto. The
counterweight
assembly 12 may include a box 12b, one or more counterweights 12w disposed in
the
box, and guide wheels 12g. Orthogonally oriented guide wheels 12g may be
connected
at each corner of the box 12b for engagement with respective guide rails of
the tower 15,
thereby transversely connecting the box to the tower. The box 12b may be
loaded with
counterweights 12w until a total balancing weight corresponding to the weight
of the rod
string lr and/or the weight of the column of production fluid, such as equal
to the weight
of the rod string lr plus one-half the weight of the fluid column.
Figure 1C illustrates the braking system 22. The crown 9 may be a frame
mounted
atop the tower 15. The drum assembly 10 may include a drum 10d, a shaft 10s,
one or
more (pair shown) ribs 10r connecting the drum to the shaft, one or more (pair
shown)
pillow blocks 10p mounted to the crown 9, and one or more (pair shown)
bearings 10b for
supporting the shaft from the pillow blocks while accommodating rotation of
the shaft
relative to the pillow blocks. The braking system 22 may include one or more
(pair shown)
disk brakes. Each disk brake may include a disk 22k disposed around and
torsionally
connected to the shaft 10s, a caliper 22c mounted to the respective pillow
block 10p, one
or more (pair shown) pistons 22p disposed in a respective chamber formed in
the
respective caliper, and a brake pad 22b connected to each piston 22p. Each
piston 22p
may be movable relative to the respective caliper 22c between an engaged
position (not
shown) and a disengaged position (shown). The brake pads 22b may be clear of
the
respective disks 22k in the disengaged position and pressed against the disks
in the
engaged position, thereby torsionally connecting the shaft 10s to the pillow
blocks 10p.
Each piston 22p may be biased toward the disengaged position by a square-cut
seal
(shown) or a return spring (not shown). Each caliper 22c may have a hydraulic
port 22h
in fluid communication with the respective piston chambers. A hydraulic flow
line may
have a lower end connected to the HPU manifold and upper ends connected to the
caliper
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ports 22h. Supply of pressurized brake fluid to the caliper chambers by the
HPU 21h may
exert fluid force on the pistons 22p, thereby moving the pistons to the
engaged position
against the bias of the square-cut seals.
Alternatively, drum brakes may be used instead of the disk brakes.
Alternatively,
the braking system 22 may be pneumatically operated.
Figure 1D illustrates the optional accelerometer 21a. The accelerometer 21a
may
be mounted to a bottom of the carriage track 13t for sensing free fall of the
counterweight
assembly 12 due to failure of the rod string 1r. The accelerometer 21a may
include a cap
24c, a body 24b, a fastener 24f, an inertia mass 24m, a sensing element, such
as a
piezoelectric crystal 24p, a washer 24w, and a circuit 24c. The fastener 24f
may be
threaded for engaging a threaded socket formed in the body 24b to retain the
inertia mass
24m, the piezoelectric crystal 24p, and the washer 24w thereto. The preload on
the
fastener 24f may also be used to calibrate the piezoelectric crystal 24p. The
body 24b
may also have a second threaded socket formed therein for receiving a threaded
fastener
(not shown) to mount the body to the carriage track 13t. The circuit 24c may
include a
housing connected to the body 24b and an amplifier disposed therein and in
electrical
communication with the piezoelectric crystal 24p. The amplifier may be in
electrical
communication with the PLC 21p via a flexible cable. The flexible cable may
supply a
power signal to the amplifier from the PLC 21p while also providing data
communication
therebetween and accommodating reciprocation of the counterweight assembly 12
relative to the PLC.
Alternatively, a battery and wireless data link may be mounted to the bottom
of the
carriage track 13t. The battery may be in electrical communication with the
accelerometer
21a and the wireless data link for supplying power thereto. The wireless data
link may
be in data communication with the accelerometer 21a for transmitting
measurements
therefrom to a wireless data link of the PLC 21p. Alternatively, the
accelerometer 21a
may be magnetostrictive, servo-controlled, reverse pendular, or
microelectromechanical
(MEMS).
The PLC 21p may be programmed to monitor the accelerometer 21a for a
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threshold measurement indicative of failure of the rod string 1r.
The threshold
measurement may be substantially greater than routine downward acceleration
experienced by the counterweight assembly 12 during normal operation of the
pumping
unit lk. The threshold acceleration may be greater than or equal to one-half,
two thirds,
or three-quarters of the standard acceleration of the Earth's gravity. Should
the PLC 21p
detect the threshold acceleration measured by the accelerometer 21a, the PLC
may
operate a manifold of the HPU 21h to supply pressurized brake fluid to the
braking system
22, thereby engaging the braking system to halt downward movement of the
counterweight assembly 12. Advantageously, using the accelerometer 21a instead
of the
tachometer 21t to detect failure of the rod string 1r reduces latency in the
detection time,
which would otherwise allow the counterweight assembly 12 to accrue kinetic
energy
which would have to be dissipated by the braking system 22.
The PLC 21p may be in data communication with a home office (not shown) via
long distance telemetry (not shown). The PLC 21p may report failure of the rod
string lr
to the home office and maintain engagement of the braking system 22 until a
workover
rig (not shown) may be dispatched to the well site to repair the rod string
1r.
Returning to Figures 1A and 1B, the load belt 11 may have a first end
longitudinally
connected to a top of the counterweight box 12b, such as by a hinge, and a
second end
longitudinally connected to the hanger bar 17, such as by wire rope. The load
belt 11
may extend from the counterweight assembly 12 upward to the drum assembly 10,
over
an outer surface of the drum 10d, and downward to the hanger bar 17. The
hanger bar
17 may be connected to the polished rod 4p, such as by a rod clamp, and the
load cell
21d may be disposed between the rod clamp and the hanger bar. The load cell
21d may
measure tension in the rod string 1r and report the measurement to the PLC 21p
via a
data link.
In operation, the motor 6 is activated by the PLC 21p to torsionally drive the
drive
sprocket 18 via the linkage 7 and reducer 8. Rotation of the drive sprocket 18
drives the
chain 16 in an orbital loop around the drive sprocket and the idler sprocket
14k. The
swivel knuckle 13k follows the chain 16 and resulting movement of the block
base 13b
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along the track 13t translates the orbital motion of the chain into a
longitudinal driving
force for the counterweight assembly 12, thereby reciprocating the
counterweight
assembly along the tower 15. Reciprocation of the counterweight assembly 12
counter-
reciprocates the rod string 1r via the load belt 11 connection to both
members.
In one embodiment, the pumping unit 1k may include a speed monitor system 500
to facilitate operation of the pumping unit 1k. The speed monitor system 500
may be
configured to protect the pumping unit 1k by monitoring and controlling one or
more
devices on the pumping unit 1k. Exemplary devices include a lubrication system
300, a
brake system 200, speed sensors, load cell 400, and belt alignment switch. By
monitoring
one or more of these devices, the speed monitor system 500 may be able to
identify
conditions such as rod part, stuck pump, excessive vibration, speed and
acceleration of
the pumping unit, lubrication errors such as low lubricator level, and other
conditions that
may damage the pumping unit 1k. The speed monitor system 500 may be operated
as
an add-on to or integrated with the PLC 21p of the pumping unit 1k.
In one embodiment, the speed monitor system 500 includes a programmable logic
controller ("SMS PLC") 505, an integrated power supply, input circuits, and
output circuits
disposed in a housing. The speed monitor system 500 may include a PROFINET
port for
communication over a PROFINET network and an optional load cell conditioner.
The
speed monitor system 500 is equipped with a display that may function as a
touch screen
interface.
In one embodiment, an optional brake system 200 may be coupled to the reducer
8, as illustrated in Figure 4. The brake system 200 includes one or more disk
brakes 201.
In the example of Figure 4, the disk brake 201 includes a disk 202
rotationally coupled to
the input shaft of the reducer 8, such as by fastening. Alternatively, the
disk 202 and the
input shaft may be integrally formed. In another embodiment, the disk 202 is
coupled, or
integral, with the output shaft. The disk brake 201 includes a caliper and a
piston 204
located in a cylinder housing 203. The caliper may be actuated by the piston
204 to urge
the brake pads between an engaged position with the disk 202 and a disengaged
position
with the disk 202. In the disengaged position, the brake pads are clear of the
disk 202.
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In the engaged position, the brake pads engage the disk 202, thereby
restricting the
rotational movement of the disk 202. In turn, the disk 202 restricts the
rotational
movement of the input shaft.
In one embodiment, the brake system 200 is spring-activated. For example, a
spring, or other suitable bias members, may be disposed in the housing 203 and
arranged
to bias the piston 204. The spring is configured to bias the piston 204 and
the brake pads
towards the engaged position. In one embodiment, the cylinder housing 203
includes a
hydraulic port in fluid communication with a hydraulic flow line connected to
the HPU
manifold. Supply of hydraulic fluid to the cylinder housing 203 by the HPU 21h
exerts a
fluid force on the piston 204. When the fluid force on the piston 204 is
greater than a bias
force provided by the biasing member, the piston 204 moves towards the
disengaged
position. When the bias force on the piston 204 is greater than fluid force,
the piston 204
moves toward the engaged position. An exemplary spring actuated brake system
is
disclosed in U.S. Patent No. 5,033,592, assigned to Hayes Industrial Brake,
Inc.
During operation of the pumping unit 1k, hydraulic fluid is supplied to the
cylinder
housing 203 such that the fluid force is greater than the bias force and, as a
result, the
piston 204 remains in the disengaged position. Upon encountering a triggering
event,
such as a rod part or some other failure, the speed monitor system 500 sends
an electrical
signal to relieve the hydraulic fluid in the cylinder housing 203 such that
the bias force
overcomes the resulting fluid force. In turn, the spring moves the piston 204
(and the
brake pad) against the disk 202, thereby stopping the rotation of the drive
sprocket 18
and stopping the downward movement of the counterweight 12w. In one
embodiment,
the brake system 200 moves the piston 204 into the engaged position within 0.2
seconds
to 1.0 seconds, such as 0.5 seconds, of a rod part. Alternatively, the brake
system 200
is pneumatically operated. It is contemplated this brake system 200 may be
used in
conjunction with, or as an alternative to, the brake system 22 coupled to the
drum
assembly 10.
In one embodiment, the brake system 200 may utilize a cylinder that is primed
to
a predetermine pressure so that there is sufficient pressure to actuate the
piston. In this
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CA 02954177 2017-01-10
respect, the brake system may include an optional pressure sensor such as a
pressure
transducer to measure the pressure in the cylinder. For example, either or
both of the
brake systems 22, 200 may be equipped with this pressure sensor. If a measured
pressure is at or below the minimum pressure needed to actuate the piston,
then the
speed monitor system 500 may send a warning to the operator or stop the
pumping unit
1k.
In yet another embodiment, the brake system 200 may include one or more
sensors for determining the position of the brake pads relative to the disk
22k, 202. The
position data may be used to prevent the brake pads from touching the disks
22k, 202,
thereby preventing inadvertent wear down of the brake pads.
In one embodiment, one or more pillow blocks 10p are configured to provide a
measurement of a change in load on the drum 10d. For example, the pillow block
10p is
instrumented to provide a measurement of the change in load. Figures 5A-E show
an
exemplary embodiment of a drum assembly 410 equipped with a load cell 400
disposed
in the pillow block 410p. The drum assembly 410 includes a drum 410d, a shaft
410s,
one or more (pair shown) pillow block 310p mounted to a top plate 409 of the
crown 9.
Bearings may be used to facilitate rotation of the shaft 410s in the pillow
block 410p. An
optional belt retainer 410r may be counted on the top plate 409 to retain the
position of
the belt 11. At least one of the pillow blocks 410p may be configured to
receive the load
cell 400. As shown, each of the pillow blocks 410p is equipped with two
openings 411
for receiving a load cell 400. In this example, only one load cell 400 has
been positioned
in each pillow block 410p. The load cell 400 is configured to measure a change
in load
exerted on the drum 10d by the load belt 11. An exemplary load cell 400 is a
strain gage.
A suitable strain gage is an Under Pillow Block Washdown-Duty load cell
commercially
available from Cleveland Motion Controls, a Lincoln Electric Company.
In the event of a rod part, the load exerted by the load belt 11 on the drum
10d,
and thus the pillow block 410p, will rapidly decrease. In turn, the load cell
400 recognizes
the change in load and transmits a signal to the PLC 21p or the speed monitor
system
500 to stop operation of the pumping unit 1k. The signal may be transmitted
via an electric
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CA 02954177 2017-01-10
. .
cable or wirelessly. For example, after receiving the signal, the speed
monitor system
500 may activate the brake system 200 to stop rotation of the sprocket 18,
thereby
stopping the free fall of the counterweight 12w. It is contemplated that any
location of the
pumping unit 1k can be provided with a strain gage to sense a rapid loss of
load on the
drum 10d. In another embodiment, the speed monitor system 500 may be
programmed
to automatically stop the pumping unit 1k in response to a measured load. For
example,
the speed monitor system 500 may have a default setting to stop the pumping
unit 1k if
the measured load is within 5% or within 10% of the maximum load capacity.
Additionally,
or alternatively, the operator may set a load limit such that the pumping unit
1k will be
stopped when the load limit is reached.
In one embodiment, the reciprocating rod pumping unit 1k includes a
lubrication
system 300. The lubrication system 300 is configured to apply lubricant, such
as refined
oil, synthetic oil, and/or grease, to the chain 16 and/or bearings in the
pumping unit 1k
during artificial lift operations. The lubrication system 300 may include a
pump configured
to move lubricant from a lubricant tank to the applicators 302. A centralized
lubrication
manifold may be used to distribute the lubricant to the various applicators
302.
The lubrication system 300 includes one or more applicators 302 positioned
adjacent the chain 16 or the bearings. Exemplary applicators 302 include one
or more
nozzles, brushes, sponges, fittings, and combinations thereof. One or more
applicators,
such as nozzles, may be positioned at multiple locations of the pumping unit
1k. The
nozzles 302 may be positioned at any appropriate position on the pumping unit
1k such
that lubricant can be applied to the chain 16 during operation of the pumping
unit 1k.
Figure 6 shows an exemplary location of a nozzle for lubricating the chain 16.
In one
example, the nozzles 302 are positioned on the idler 14 of the pumping unit
1k. In another
example, the nozzles 302 are positioned on the tower base 19 to apply
lubricant to the
chain 16 and the sprocket 18. In another example, grease may be applied to the
bearings
using a centralized grease distribution system or grease fittings at
predetermined
locations.
Operation of the lubrication system 300 is controlled by the speed monitor
system
CA 02954177 2017-01-10
500. The speed monitor system 500 controls the duration, frequency intervals,
and
amount of lubricant provided to the applicators 302. The lubrication system
300 is
configured to apply lubricant at regular intervals. In one embodiment, the
lubrication
system 300 applies lubricant at intervals between 20 minutes and 40 minutes,
such as 30
minute intervals. The lubrication system 300 applies lubricant for a
predetermined
duration. For example, the predetermined duration is between 30 seconds and 2
minutes,
such as 1 minute.
In one embodiment, the speed monitor system 500 periodically monitors
movement of the pump piston. For example, the speed monitor system monitors
the
pump piston using a proximity switch located inside the lubrication pump and
configured
to detect the pump piston. When the pump is active, the speed monitor system
500 may
read the proximity switch at 30 minute intervals; at 15 to 45 minute
intervals; 30 to 90
minute intervals; or 15 to 300 minute intervals. In one example, during each
interval, the
speed monitor system 500 may read the proximity switch for 0.3 seconds of each
second
for a period of 30 seconds. If movement of the pump piston is not detected,
the speed
monitor system 500 may trigger an alarm. If the pump piston is still not
detected after a
longer period of time, such as after twenty-four hours, the speed monitor
system 500 may
shut down the lubrication system 300. The lubrication system 300 may
optionally include
lubrication sensors configured to determine the amount of the lubricant in the
lubrication
tank. Pressure sensors may optionally be provided to monitor the pressure of
oil in the
lubrication system to ensure the pressure is sufficient for the applicator 302
to supply the
lubricant. A flow meter may optionally be provided to measure the flow rate of
the
lubricant. The sensors are configured to communicate sensed data to the speed
monitor
system 500 via an electronic cable or wirelessly.
In another embodiment, the speed monitor system 500 is configured to provide
overspeed protection of the pumping unit lk. In one embodiment, one or more
proximity
sensors 510 may be provided at the lower end of the tower 15 to monitor the
speed of
the belt 11. An exemplary proximity sensor is a Hall effect sensor or any
proximity sensor
suitable for measuring the speed of the lower sprocket 18, chain 16, and the
brake disk
202. In one example, the pulse signals from a rotating target wheel are
counted to
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CA 02954177 2017-01-10
determine the speed of the belt 11. If the speed of the belt ills above a
predetermined
limit, then the speed monitor system 500 will stop the pumping unit 1k.
Optionally, the
position of the belt 11 may be determined from the pulse signals and
illustrated on a
display.
In another embodiment, one or more proximity sensors 520 may be located at an
upper end of the tower 15 to monitor the time required to complete a cycle of
the belt 11.
If the belt 11 does not complete the cycle in a predetermined number of
pulses, more time
may be added to allow for tolerances. For example, between 5 percent and
fifteen
percent of the cycle time may be added. If the cycle is not completed within
this extra
number of pulses, then the speed monitor system 500 will stop the pumping unit
1k. If
the pumping unit 1k is stopped, the speed monitor system 500 may optionally
turn on a
stop indicator lamp and log the alarm.
In another embodiment, the proximity sensors 510 located at the lower end of
the
tower 15 may be used to monitor acceleration of the belt 16. For example, the
pulse
signals from these proximity sensors 510 can be used to calculate the speed of
the belt
16, which can be converted to acceleration by determining the change in speed
over time.
If the acceleration is above a predetermined limit or is outside a
predetermined
acceleration range, the speed monitor system 500 may stop the pumping unit 1k.
In
another embodiment, both a warning limit and an upper limit may be set to
monitor
acceleration. In one example, the upper limit is set at a threshold value
indicative of a
rod part condition. The threshold value may be substantially greater than
routine
downward acceleration experienced by the counterweight assembly 12 during
normal
operation of the pumping unit 1k. The threshold acceleration may be greater
than or
equal to one-half, two thirds, or three-quarters of the standard acceleration
of the Earth's
gravity. Should the SMS PLC 505 detect the threshold value as calculated from
the
measured speed of the belt 16, the speed monitor system 500 may activate the
brake
system 200 to stop free-fall of the counterweight 12w. In particular, the SMS
PLC 505
may relieve hydraulic pressure in the cylinder to allow the spring to urge the
brake pads
into engagement with the brake disk 202, thereby stopping rotation of the
input shaft of
the reducer 8. Alternatively, SMS PLC 505 may send a signal to the PLC 21p to
operate
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CA 02954177 2017-01-10
a manifold of the HPU 21h to supply pressurized brake fluid to the braking
system 22,
thereby engaging the braking system 22 to halt downward movement of the
counterweight assembly 12.
In yet another embodiment, the expected acceleration necessary to stop the
counterweight 12w can be calculated from the measured velocities. The speed
monitor
system 500 may pre-emptively stop the pumping unit 1k if the acceleration
necessary to
stop the counterweight 12w is above a predetermined safe limit.
In another embodiment, a belt alignment sensor 530 may be provided to measure
the sway of the belt 16 relative to its vertical axis, as shown in Figure 1B.
An exemplary
alignment sensor is a capacitance sensor. The alignment sensor 530 may be
positioned
at predetermined outer limits of the sway of the belt 16 and configured to
monitor the
belt's 16 presence at these outer limits. For example, one alignment sensor
530 may be
positioned on the left and right outer limits of the allowable sway range of
the belt 16. If
the belt 16 moves into the monitored areas, the speed monitor system 500 may
stop the
pumping unit 1k.
In yet another embodiment, the tower 15 may be provided with one or more
vibration sensors 540 to determine the amount of vibration on the tower 15, as
shown in
Figure 1C. Any suitable vibration sensors known may be used. In one example,
the
vibrations sensors 540 may be a normally open vibration switch. When the
vibration is
within an acceptable range, the vibration sensor 540 remains open. The
vibration sensor
540 will close when the vibration is outside of the acceptable range or above
a
predetermined limit. If this occurs, a signal may be sent to the speed monitor
system 500
to shut down the pumping unit 1k, such as by activating the brake system 200
as
discussed above. Optionally, the speed monitor system 500 can log the alarm.
In yet another embodiment, the temperature of the bearings 10b supporting the
drum 10d may be monitored to prevent overheating. For example, one or more
temperature sensors 550 may be used to monitor the temperature of the bearings
10b.
If the temperature is above an acceptable temperature limit, then the speed
monitor
system 500 may shut down the pumping unit 1k such as by activating the brake
system
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CA 02954177 2017-01-10
200 as discussed above. Optionally, the speed monitor system 500 can log the
alarm.
In yet another embodiment, the pumping unit 1k may include an emergency stop
switch. The emergency stop switch may be activated by the PLC 21p, the speed
monitor
system 500, an operator, or any other suitable controller capable of detecting
a faulty
condition on the pumping unit 1k. The emergency stop switch may be located at
any
suitable location on or proximate the pumping unit 1k.
In one embodiment, a reciprocating rod pumping unit includes a tower; a
counterweight assembly movable along the tower; a drum connected to an upper
end of
the tower and rotatable relative thereto; a belt having a first end connected
to the
counterweight assembly, extending over the drum, and having a second end
connectable
to a rod string; a prime mover for reciprocating the counterweight assembly
along the
tower; a sensor for detecting a condition of the pumping unit; a brake system
for halting
free-fall of the counterweight assembly; and a controller in communication
with the sensor
and operable to activate the brake system in response to detection of the
faulty condition
of the pumping unit.
In another embodiment, a reciprocating rod pumping unit includes a tower; a
counterweight assembly movable along the tower; a drum connected to an upper
end of
the tower and rotatable relative thereto; a belt having a first end connected
to the
counterweight assembly, extending over the drum, and having a second end
connectable
to a rod string; a prime mover for reciprocating the counterweight assembly
along the
tower; a sensor for detecting a condition of the pumping unit; and a
controller in
communication with the sensor and operable to cause the counterweight assembly
to
stop in response to the detected condition.
In another embodiment, a reciprocating rod pumping unit includes a tower; a
counterweight assembly movable along the tower; a drum connected to an upper
end of
the tower and rotatable relative thereto; a belt having a first end connected
to the
counterweight assembly, extending over the drum, and having a second end
connectable
to a rod string; a prime mover for reciprocating the counterweight assembly
along the
tower; a lubrication system for applying lubricant to at least one of a chain,
a bearing, and
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CA 02954177 2017-01-10
combinations thereof; at least one of a lubrication sensor for detecting an
amount of
lubricant in the lubrication system, a pressure sensor for detecting a
pressure in the
lubrication system, and a flow meter for measuring a flow rate of the
lubricant; and a
controller in communication with the at least one of the lubrication sensor,
the pressure
sensor, and the flow meter, and operable to cause the counterweight assembly
to stop.
In one or more of the embodiments described herein, the sensor is one of a
speed
sensor for detecting a speed of the belt; a cycle sensor for detecting a cycle
of the belt; a
load sensor for detecting a change in load on the drum; a belt alignment
sensor for
detecting an alignment of the belt; a vibration sensor for detecting a
vibration of the tower;
and combinations thereof;
In one or more of the embodiments described herein, the unit further includes
a
gearbox, and the braking system includes a disk torsionally coupled to the
gearbox; a
piston disposed in a cylinder; a caliper connected to the piston; and a brake
pad mounted
to the caliper and movable by the piston between an engaged position and a
disengaged
position relative to the disk; and a bias member configured to bias the piston
and the
brake pad toward the engaged position.
In one or more of the embodiments described herein, the unit includes the
speed
sensor; and the detected speed of the belt is above a predetermined limit.
In one or more of the embodiments described herein, the speed sensor comprises
a proximity sensor.
In one or more of the embodiments described herein, the unit includes the load
sensor; and the detected change in load is above a predetermined limit.
In one or more of the embodiments described herein, the load sensor is
disposed
in a pillow block supporting the drum.
In one or more of the embodiments described herein, the unit includes the
vibration
sensor.
In one or more of the embodiments described herein, the unit includes a
lubrication
CA 02954177 2017-01-10
system for applying lubricant to at least one of a chain, a bearing, and
combinations
thereof.
In one or more of the embodiments described herein, the lubrication system
includes at least one of a lubrication sensor for detecting an amount of
lubricant in the
lubrication system; a pressure sensor for detecting a pressure in the
lubrication system;
and a flow meter for measuring a flow rate of the lubricant.
In one or more of the embodiments described herein, the controller is in
communication with the at least one of the lubrication sensor, the pressure
sensor, and
the flow meter, and operable to activate the brake system in response to
detection of a
faulty condition of the lubrication system.
In one or more of the embodiments described herein, the controller is
configured
to calculate an acceleration of the belt using the speed measured by the speed
sensor.
In one or more of the embodiments described herein, the controller is operable
to
activate the brake system when the calculated acceleration is above a
predetermined
limit.
In one or more of the embodiments described herein, the unit includes a chain
coupled to the prime mover and a carriage for coupling the chain to the
counterweight.
In one or more of the embodiments described herein, the carriage is coupled to
the counterweight using one or more slide bearings or one or more bushings.
In one or more of the embodiments described herein, the one of more slide
bearings or the one or more bushings are coupled to one or more tracks on the
counterweight.
In one or more of the embodiments described herein, the unit includes the
cycle
sensor; and the detected cycle was not completed within a predetermined time
period.
In one or more of the embodiments described herein, the unit includes the
alignment sensor; and the alignment sensor detected the presence of the belt.
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While the foregoing is directed to embodiments of the present disclosure,
other
and further embodiments of the disclosure may be devised without departing
from the
basic scope thereof, and the scope of the invention is determined by the
claims that follow.
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