Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02591186 2013-04-16
1 ADDITIVE PUMP
2 FIELD OF THE INVENTION
3 10001) The present invention relates to injection pumps, in
particular to ini'ection pumps for
4 injecting an additive into a pipeline.
6 SUMMARY OF THE INVENTION
7 100021 It is well known to inject an additive into a fluid
pipeline, such as a gas pipeline to
8 enhance the serviceability of the pipeline. Typically, such additives are
injected to inhibit
9 corrosion or to enhance lubrkation of components in the pipeline. The
additive is injected in
relatively small volumes compared to the volume of fluid carried by the
pipeline but the
11 additive's effect is significant.
12 100031 The additives need to be injected periodically into the
fluid and, as such, additive
13 stations are placed at spaced locations along the length of the
pipeline. Because of the nature of
14 the pipeline and the terrain through which it must pass, the additive
stations are typically located
in remote areas and beyond access to normal services. The injection stations
!Mist therefore be
16 self contained and capable of working without undue supervision over
long periOds of time.
17 RON] The siting of additive stations at remote locations also
requires the environmental
18 impact of such stations to be minimized. The additives may in some cases
be toxic or potentially
19 hazardous and accordingly it is necessary to ensure that any spillage of
such additives is
minimized.
21 100051 One such an arrangement that addresses these concerns is
shown in US Publication
22 No. 2004/0206229 in which the fluid in the pipeline is used as a motive
force for an injection
23 pump and the fluid is returned to the pipeline to avoid any egress into
the atmosphere. The
24 motive force available from such an arrangement is significant due to
the pressure differential
that exists in the pipeline and accordingly conventional sealing can be
utilized within the plunger
26 to inhibit leakage of additives.
t -
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1 to utilize a battery powered pump with the battery being recharged from
solar cells. With this
2 arrangement however the conventional sealing arrangement used on additive
pumps imposes a
3 high load upon the piston of the pump and thereby increases the energy
consumption of the
4 additive station beyond that that may typically be available from a solar
powered source.
Conventional sealing arrangements utilize a packing gland whose sealing
capability depends in
6 part on the radial load applied to the shaft on which it is mounted. Such
seals are relatively easy
7 to install but impose significant drag on the piston. There is also a
need with such additive
8 pumps to provide control of the injection rate of the additive to suit
varying conditions and for
9 adjustment of that rate from station to station as circumstances differ.
[0007] It is therefore an object of the present invention to provide an
additive pump in which
11 the above disadvantages are obviated or mitigated.
12
13 BRIEF DESCRIPTION OF THE DRAWINGS
14 [0008] An embodiment of the invention will now be described by way
of example only with
reference to the accompanying drawings in which:
16 [0009] Figure 1 is a general side view showing an additive
station.
17 [0010] Figure 2 is an enlarged sectional view of the portion of
Figure 1 shown within the
18 circle identified as II.
19 [0011] Figure 3 is a schematic representation of the controller
shown in Figure 1.
21 DETAILED DESCRIPTION OF THE INVENTION
22 [0012] Referring therefore to Figure 1, a pipeline indicated at P
is supplied with an additive
23 from a reservoir R through a conduit C. The additive is moved through
the conduit C by an
24 additive pump assembly generally indicated 10. Energy for the operation
of the pump assembly
10 is obtained from a solar panel 12 that is used to charge a battery 14 and
provide a reserve of
26 electrical energy for the assembly 10.
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1 [0013] The assembly 10 includes a pump 16 located in a housing 17
and a controller 18 that
2 controls the operation of the pump 16. The pump 16 includes a stepper
motor 20 that is
3 controlled by the controller 18 as will be described in more detail
below. The stepper motor is
4 available from Haydon Switch and Instrument, PO Box 3329, 1500 Meridian
Road, Waterbury
Connecticut 06705, under the Series 57000, size 23 and Series 87000, size 34
motors. The
6 motor 20 includes an armature that cooperates with a drive shaft 24
through a lead screw 25.
7 Rotation of the drive shaft 24 is inhibited so that rotation of the
armature 22 induces a linear
8 axial displacement of the drive shaft 24 through the action of the lead
screw 25.
9 [0014] The drive shaft 24 is connected to a transfer shaft 26 that
is attached through a
coupling 28 to a piston 30. The coupling 28 is of known construction that
permits alignment
11 between the transfer shaft 26 and the piston 30 and inhibits lateral
loads being placed upon the
12 piston during reciprocal movement. The piston 30 communicates with a
pumping chamber 32 of
13 a positive displacement fluid end 34 that may be of any convenient form
known in the industry.
14 The fluid end 34 incorporates an inlet check valve 36 and an outlet
check valve 38 to ensure
transfer of fluid from the reservoir R to the pipeline P as the piston 30
reciprocates.
16 [0015] The connection of the fluid end 34 to the piston 30 is best
seen in Figure 2. The
17 piston 30 is slidably supported in a seal assembly 40 that is supported
on an end face 41 of pump
18 housing 17. The seal assembly 40 includes a seal carrier 42 formed from
an inner sleeve 44 and
19 an outer nose 46. The sleeve 44 and nose 46 are axially aligned to
define a central bore 60 in
which the piston 30 is a close sliding fit. The bore 60 is in fluid
communication with the
21 pumping chambers 32 so that reciprocal motion of the piston 30 within
the bore 60 induces flow
22 from the reservoir R to the pipeline P.
23 [0016] The sleeve 44 has a pair of stepped counter bores 48, 49
formed at one end adjacent
24 to the wall 42 to carry circumferential lip seals 50, 51. The seal 50
acts as a wiper to prevent
contaminants from entering the central bore 60 and the seal 51 acts as a seal
to inhibit egress of
26 fluid from the chamber 60. The opposite end of the sleeve 44 has a
reduced shoulder 52 that is
27 nested within a counter bore 54 of the nose 46. The shoulder 52 and
counter bore 54 define a
28 cavity 56 in which a circumferential lip seal 58 is carried and
functions in a manner to the seal 51
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1 to prevent egress of fluid. It will be noted that the lip seals 50, 51,
58 are located at opposite end
2 faces of the sleeve 44 so that the seals can be readily assembled.
3 [0017] The outer surface of the sleeve 44 has an undercut recess
57 in which a face seal 59 is
4 located to but against the radial face of one end of the nose 46. The
face seal therefore provides
a static seal between the two components of the carrier, namely the sleeve 44
and nose 46.
6 Again therefore, the seal may be easily assembled with the seal carrier.
7 [0018] The sleeve 44 and nose 46 are supported in a collar 62
having a central boss 64 and a
8 radial flange 66. The boss 64 is counter bored to receive the sleeve 44
and nose 46 and has a pair
9 of circumferential grooves, 67, 68 that locate static seals 70, 72 to
seal between the nose 44 and
the counter bore of the boss 64.
11 [0019] The radial flange 66 is located against the wall 42 by a
retaining cap 74 with a seal 76
12 sealing between the cap 74 and the radial outer face of the flange 66. A
similar seal 78 is
13 provided between the outer surface of the boss 64 and the cap to ensure
fluid tight fitting. The
14 outer surface of the flange 66 is bevelled as indicated at 80 to define
an annular gallery that is
intersected by a drainage port 82. The drainage port also communicates through
cross drillings
16 84 with the bore 60 at a location between the two seals 51, 58. Any
fluid entering between the
17 two seals is therefore drained by the port 82 to the reservoir R as
shown in Figure 1.
18 [0020] The inner surface of the boss 64 is threaded to receive a
threaded male fitting 86 of
19 the fluid end 34. The fluid end 34 has a elongate cylindrical recess 90
into which the nose 46 is a
sliding fit. The distal end of the nose 46 is undercut to provide a notch 92
to form a seat for a
21 high pressure face seal 94. The notch 92 has a radial face 96 that
opposes a complimentary
22 radial face 98 on the fluid end so that the seal 94 is held between a
pair of radial faces. Rotation
23 of the fluid end within the boss 64 therefore applies a compressive load
to the nose 46 and sleeve
24 44 to maintain the face seals 59,94 in compression.
[0021] In operation, reciprocation of the piston 30 within the bore 60
causes fluid to be
26 initially drawn into the chamber 32 through a check valve 36 as the
piston 30 is retracting and
27 subsequently to expel fluid from the bore 60 through the check valve 38
as the piston 30
28 advances. During such reciprocal motion, the seals 50, 58 bear against
the piston but in view of
29 the fact that the piston itself is a close sliding fit within the bore
and the seals utilized are
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1 preferably a lip seal, the passage of fluid past the seals is minimal.
The drag on the piston due to
2 the use of the pair of seals is also minimized and therefore the piston
30 has relatively low
3 resistance to such axial movement. Any fluid that does pass through the
seal 58 is drained
4 through the port 82 back to the reservoir and thereby inhibits any loss
of the additive during the
pumping action.
6 [0022] The seal carrier 42 itself provides a sealed environment to
inhibit egress of fluid
7 under high pressure by providing a pair of face seals between radially
opposed faces of the seal
8 carrier. The seal 94 and seal 59 effectively inhibit the flow of fluid
radially outwardly beyond
9 the seal carrier 42 due to the compressive loads that act on the seals.
It will also be noted that by
forming the seal carrier in two parts namely the sleeve 44 and the nose 46,
the seal 59 is readily
11 located on the seal carrier as is the face seal 94. Accordingly, the
optimum installation and
12 sealing conditions can be provided for the face seals without inhibiting
the operation of the
13 piston. The seal 58 is preferably a dynamic spring energized rod seal
with a high density,
14 solvent resistant polymer sealing material. Such seals are capable of
providing 90% sealing
efficiency at pressures greater than 3200 psi. The seals 50, 51 are lower
pressure lip seals
16 designed to operate at slightly elevated pressures and essentially
inhibiting the carriage of fluids
17 on the piston into or from the housing. The face seals 59, 94 are static
face seals of the 0-ring
18 type which provide 100% sealing at pressures over 3200 psi.
19 [0023] As noted above, reciprocal motion of the piston 30 is
derived from the stepping motor
20. The controller 18 provides control pulses through the field coils of the
motor 20 which in
21 turn produce a defined rotational output. By varying the frequency of
the pulses and their
22 polarity, the rate of rotation of the armature and its direction of
rotation may be regulated as
23 illustrated in Figure 3.
24 [0024] The controller 18 has a program more programmable interface
100 providing keys
102, 104 to permit adjustment of the control. The interface 100 communicates
with a processor
26 106 that includes memory 108. The memory has a pair of registers, one
for forward operation
27 110 and the other for reverse operation 112. Each of the registers 110,
112 includes settings for
28 the torque required, the ramping of the onset of the torque and the
acceleration required. The
29 memory 108 also includes a stroke setting 114 that determines the number
of pulses that
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1 constitute the full stroke of the piston. Each of these setting are
manually adjustable through the
2 interface 100.
3 [0025] The current supplied to the field windings of the motor 20
is determined by the
4 current logic module 118. The rate at which the current is supplied is
determined from the
ramping and acceleration values in the registers 110, 112. The modules 118,
120 are used to
6 drive a pulse generator 122 that outputs pulses of the appropriate
amplitude, frequency and
7 polarity to drive the armature in the desired direction of the desired
rate. The pulses generated
8 by the pulse generator 122 are monitored by a counter 124 and used to
control the selection of
9 the registers 110, 112. Each time the counter 124 attains a value
corresponding to that of the
stroke register 114, the register currently in use is terminated and the other
register condition is
11 loaded in through the modules 118, 120 to reverse the direction of
motion.
12 [0026] By providing separate adjustment of the forward and reverse
motion, different rates
13 of movement can be attained and, with a rapid retraction of the piston,
a substantially continuous
14 injection of fluid can be attained if required.
[0027] The manual interface 100 permits the selection and setting of the
conditions
16 implemented by the control logic. The controller may be implemented on a
control logic unit
17 available from Trinanic Motion Control GmbH and Co. KG of Hamburg,
Germany.
18 [0028] It will be see therefore that the use of the controller
provides enhanced flexibility over
19 the rate of injection and in particular with a differential rate of
advance and retraction to permit
enhanced control. The provision of the seal assembly with minimal resistance
to motion also
21 ensures that the current available from the solar source and batteries
is sufficient for continuous
22 operation.
23 [0029] As described above, the reciprocation of the piston 30 is a
linear reciprocation with
24 the drive shaft 24 secured to the housing of motor 20. To enhance the
performance and life of
the seals, it is also possible to incorporate into the coupling 28 a helical
drive such that the linear
26 reciprocation of the transfer shaft 26 is converted to a helical motion
of the piston 30 thus, the
27 piston will both rotate and move axially past the seals 50, 51, 58 to
further in prolong the life of
28 the seals.
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1 100301 The preferred embodiment of seal assembly has been described in
conjunction with a
2 solar powered electrical supply and controller. It will be appreciated,
however, that the seal
3 assembly may be used with other forms of drive of plunger and may be used
as a retrofit to
4 existing seal assemblies used on additive pumps.
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