U.S. patent application number 14/076437 was filed with the patent office on 2015-05-14 for plunger pump, plunger, and method of manufacturing plunger pump.
This patent application is currently assigned to National Oilwell Varco, L.P.. The applicant listed for this patent is National Oilwell Varco, L.P.. Invention is credited to Heath Gregory Folk, Manuel Moeller, Jason Neal Whaley.
Application Number | 20150132157 14/076437 |
Document ID | / |
Family ID | 51830217 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150132157 |
Kind Code |
A1 |
Whaley; Jason Neal ; et
al. |
May 14, 2015 |
Plunger Pump, Plunger, and Method of Manufacturing Plunger Pump
Abstract
A plunger pump includes a pump fluid end having a fluid chamber
and a suction bore, discharge bore, and plunger bore in
communication with the fluid chamber. A plunger is arranged to
reciprocate into and out of the fluid chamber through the plunger
bore. The plunger has a plunger body with an inner cavity and an
insert disposed in the inner cavity such that the combined
stiffness of the insert and plunger body is greater than the
stiffness of the plunger body. A crank mechanism is coupled to the
plunger and operable to reciprocate the plunger.
Inventors: |
Whaley; Jason Neal; (Bells,
TX) ; Moeller; Manuel; (Tulsa, OK) ; Folk;
Heath Gregory; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
National Oilwell Varco, L.P. |
Houston |
TX |
US |
|
|
Assignee: |
National Oilwell Varco,
L.P.
Houston
TX
|
Family ID: |
51830217 |
Appl. No.: |
14/076437 |
Filed: |
November 11, 2013 |
Current U.S.
Class: |
417/321 ;
29/890.09; 92/172 |
Current CPC
Class: |
F04B 47/02 20130101;
F04B 53/162 20130101; F04B 53/14 20130101; F04B 47/12 20130101;
Y10T 29/494 20150115; F16J 1/16 20130101; F04B 53/16 20130101; F16J
1/18 20130101 |
Class at
Publication: |
417/321 ; 92/172;
29/890.09 |
International
Class: |
F04B 53/14 20060101
F04B053/14 |
Claims
1. A plunger pump, comprising: a pump fluid end having a fluid
chamber, a suction bore in communication with the fluid chamber, a
discharge bore in communication with the fluid chamber, and a
plunger bore in communication with the fluid chamber; a plunger
arranged to reciprocate into and out of the fluid chamber through
the plunger bore, the plunger having a plunger body with an inner
cavity and an insert disposed in the inner cavity, wherein a
combined stiffness of the plunger body and insert is greater than a
stiffness of the plunger body; and a crank mechanism coupled to the
plunger and operable to reciprocate the plunger.
2. The plunger pump of claim 1, wherein the inner cavity occupies
30% to 60% of the volume of the plunger body.
3. The plunger pump of claim 1, wherein the insert is configured
such that there is an interference fit between an outer surface of
the insert and an inner surface of the plunger body.
4. The plunger pump of claim 3, wherein the insert is a hollow
insert.
5. The plunger pump of claim 3, wherein the insert is a solid
insert.
6. The plunger pump of claim 3, wherein a volume of the insert is
30% to 70% of a volume of the inner cavity.
7. The plunger pump of claim 1, wherein the crank mechanism
comprises a crosshead coupled to the plunger, a connecting rod
coupled to the crosshead, and a crankshaft coupled to the
connecting rod.
8. The plunger pump of claim 7, wherein a coupling between the
crosshead and connecting rod comprises a wrist pin coupled to the
crosshead and retained to the connecting rod such that there is no
relative rotation between the wrist pin and the connecting rod.
9. The plunger pump of claim 8, wherein the wrist pin is retained
to the connecting rod by inserting a retainer fastener through the
connecting rod into a hole inside the wrist pin.
10. The plunger pump of claim 7, wherein a coupling between the
crosshead and connecting rod comprises a pair of surface holes in
the connecting rod and a pair of wrist pins engaging the surface
holes and retained to the crosshead.
11. The plunger pump of claim 7, wherein the crank mechanism
further comprises an extension rod coupling the plunger to the
crosshead.
12. The plunger pump of claim 7, wherein the crank mechanism
further comprises an adapter plate coupling the plunger to the
crosshead.
13. The plunger pump of claim 7, wherein the wrist pin is received
in a hole in the connecting rod, and wherein the hole and wrist pin
are configured such that there is an interference fit between the
wrist pin and the connecting rod.
14. The plunger pump of claim 1, wherein the suction bore
intersects the plunger bore, and wherein a transition between the
suction bore and plunger bore comprises a fillet surface.
15. The plunger pump of claim 14, wherein the discharge bore
intersects the plunger bore, and wherein a transition between the
discharge bore and plunger bore comprises a combination of a fillet
surface, a reduced diameter bore, a tapered surface, and an
enlarged diameter bore.
16. The plunger pump of claim 14, wherein a tapered valve seat is
formed in each of the suction bore and discharge bore.
17. A plunger for a plunger pump, comprising: a plunger body having
an inner cavity defined therein and an open end; and an insert
disposed in the inner cavity, the insert being configured such that
a combined stiffness of the insert and plunger body is greater than
a stiffness of the plunger body; and an end cap mounted at the open
end and adapted for coupling to an adapter plate or extension rod
of a crank mechanism.
18. The plunger of claim 17, wherein the inner cavity occupies 30%
to 60% of the volume of the plunger body.
19. The plunger of claim 17, wherein the insert is configured such
that there is an interference fit between an outer surface of the
insert and an inner surface of the plunger body.
20. The plunger of claim 17, wherein the insert is a hollow
insert.
21. The plunger of claim 17, wherein the insert is a solid
insert.
22. The plunger of claim 17, wherein a volume of the insert is 30%
to 70% of a volume of the inner cavity.
23. A method of manufacturing a plunger pump, comprising: forming a
pump fluid end having a fluid chamber, a suction bore and a
discharge bore disposed along a first axis and intersecting with
the fluid chamber, and a plunger bore disposed along a second axis
that is perpendicular to the first axis and intersecting with the
fluid chamber; forming a plunger having a plunger body with an
inner cavity; disposing an insert in the inner cavity such that a
combined stiffness of the plunger body and insert is greater than a
stiffness of the plunger body; arranging the plunger in the plunger
bore; and coupling a crank mechanism to the plunger to reciprocate
the plunger into and out of the fluid chamber through the plunger
bore.
24. The method of claim 23, wherein coupling the crank mechanism
comprises coupling a crosshead of the crank mechanism to the
plunger and coupling a connecting rod of the crank mechanism to the
crosshead, wherein coupling the connecting rod comprises retaining
a wrist pin coupled to the crosshead to the connecting rod such
that there is no relative motion between the wrist pin and the
connecting rod.
25. The method of claim 23, wherein forming the pump fluid end
comprises forming a first transition between the suction bore and
plunger bore comprising a first fillet surface and forming a second
transition between the discharge bore and plunger bore comprising a
second fillet surface.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
FIELD
[0003] The field relates to construction of high pressure plunger
pumps.
BACKGROUND
[0004] Well service pumps are used in the oil and gas industry to
pump fluids down a well for various purposes. One common use of
well service pumps is in hydraulic fracturing of formations. The
pump can be used to pump a high pressure fluid containing solids
into the well, where the high pressure fluid will expand fractures
in the formation or fracture the formation, leaving larger fluid
passages through which formation fluids can flow into the well. The
solids in the fluid will remain in the larger fluid passages to
prop the fluid passages open, thereby increasing well
production.
[0005] Well service pumps are commonly plunger pumps, which are a
type of reciprocating positive displacement pumps. In these pumps,
a plunger reciprocates axially in a fluid end, with a packing
retained between the fluid end and plunger preventing leakage
during the reciprocating motion of the plunger. A small annular gap
is typically provided between the outer diameter of the plunger and
the inner diameter of the packing to prevent galling or surface
damage to the plunger as the plunger reciprocates. However, slight
increases in gap clearance may have a detrimental effect on the
life of the packing due primarily to accelerated packing material
extrusion.
[0006] High plunger compressive strength is typically needed to
help maximize packing life and the operational efficiencies of the
pump. Many conventional high pressure well service plunger pumps
use plungers of solid construction to achieve high plunger
compressive strength. However, larger diameter and/or longer stroke
plungers with solid construction are often unwieldy to handle
during routine maintenance operations. Hollow plungers have been
proposed, but these hollow plungers tend to deflect diametrically
under loads.
[0007] Plunger pumps use a crank mechanism to provide the
reciprocating motion of the plunger. The crank mechanism typically
includes an extension rod that is rigidly attached to a crosshead
that is constrained to move axially by the frame of the pump. The
crosshead is coupled to an eccentric crankshaft via a wrist pin and
connecting rod. As the crankshaft rotates, the connecting rod
transfers this motion to the crosshead. Because the crosshead is
constrained to move axially, the rotational motion will be
converted into reciprocating motion, which is transferred to the
plunger via the extension rod.
[0008] The wrist pin is retained to the crosshead and is supported
using a bearing located internally within the connecting rod. An
annular gap is typically provided between the outer diameter of the
wrist pin and the inner diameter of the wrist pin bearing to allow
distribution of a lubrication film and to prevent load transfer
from the relatively large rod to the much smaller wrist pin. This
annular gap allows deformation of the connecting rod bearing
surface during high load conditions, which can create uneven
loading and premature bearing failure, such as galling.
[0009] Many conventional fluid ends feature a valve over valve
arrangement, where the suction and discharge valves are positioned
vertically, one valve above the other, and perpendicular to the
intersecting plunger bore. This provides a rather compact fluid end
design, which is desirable for mobile applications. However, the
intersection of these two bores creates a surface discontinuity,
significantly increasing stresses within these highly localized
areas. These surfaces normally fail due to fatigue as they are also
exposed to cyclical loadings.
SUMMARY OF THE DISCLOSURE
[0010] The subject matter disclosed herein relates to improvements
in a plunger pump. In one illustrative embodiment, a plunger pump
comprises a pump fluid end having a fluid chamber and a suction
bore, discharge bore, and plunger bore in communication with the
fluid chamber. A plunger is arranged to reciprocate into and out of
the fluid chamber through the plunger bore. The plunger has a
plunger body with an inner cavity and an insert disposed in the
inner cavity to increase the stiffness of the plunger. A crank
mechanism is coupled to the plunger and operable to reciprocate the
plunger.
[0011] It is to be understood that both the foregoing general
description and the following detailed description are exemplary of
certain embodiments of the invention and are intended to provide an
overview or framework for understanding the disclosure. The
accompanying drawings illustrate various exemplary embodiments of
the invention and are included to provide a further understanding
of the disclosure and the principles and operation of the disclosed
embodiments.
BRIEF DESCRIPTION OF DRAWINGS
[0012] The following is a description of the figures in the
accompanying drawings. The figures are not necessarily to scale,
and certain features and certain views of the figures may be shown
exaggerated in scale or in schematic in the interest of clarity and
conciseness.
[0013] FIG. 1A shows a cross-section of an illustrative embodiment
of a plunger pump.
[0014] FIG. 1B shows a cross-section of another illustrative
embodiment of a plunger pump.
[0015] FIG. 2 shows an enlarged portion of the cross-section of
FIG. 1A.
[0016] FIG. 3 shows a cross-section of an illustrative embodiment
of a plunger.
[0017] FIG. 4A shows an illustrative embodiment of a connecting rod
and crosshead assembly.
[0018] FIG. 4B shows a cross-section of FIG. 4A along line
4B-4B.
[0019] FIG. 4C shows a cross-section of FIG. 4A along line
4C-4C.
[0020] FIG. 5 shows a cross-section of an illustrative embodiment
of a crosshead and connecting rod assembly.
[0021] FIG. 6 shows a cross-section of an illustrative embodiment
of a crosshead and connecting rod assembly.
[0022] FIG. 7 shows a cut-away of the pump fluid end of FIG.
1A.
DESCRIPTION OF EMBODIMENTS
[0023] In the following detailed description, numerous specific
details may be set forth in order to provide a thorough
understanding of the disclosed embodiments. However, it is to be
understood that other embodiments of the invention may be practiced
without incorporating some or all of the specific details that are
a part of these disclosed embodiments. In other instances,
well-known features or processes may not be described in detail in
the disclosed embodiments so as not to unnecessarily obscure the
disclosure. In addition, like or identical reference numerals may
be used to identify common or similar elements between the
embodiments.
[0024] FIG. 1A is an illustrative embodiment of a plunger pump 10
having a pump fluid end 12 coupled to a pump power end 14 via stay
rods 13. The pump fluid end 12 includes a fluid chamber 16. The
pump fluid end 12 further includes a suction bore 18a, a discharge
bore 18b, a plunger bore 20a, and an access bore 20b, all of which
intersect with the fluid chamber 16. The suction and discharge
bores 18a, 18b are opposed and generally axially aligned along axis
17a, and the plunger bore 20a and access bore 20b are opposed and
generally axially aligned along axis 17b. Axis 17b is perpendicular
to axis 17a. The suction bore 18a is in communication with a
suction manifold 21 via a suction valve 23a. Similarly, the
discharge bore 18b is in communication with a discharge port 25 via
a discharge valve 23b.
[0025] A plunger 28 is arranged in the plunger bore 20a and may
reciprocate into and out of the fluid chamber 16. The reciprocating
motion is provided by a crank mechanism 34 that is located in the
pump power end 14. During the suction stroke of the plunger 28, the
plunger 28 is withdrawn from the fluid chamber 16 into the plunger
bore 20a, and fluid is drawn from the suction manifold 21, through
the suction valve 23a, into the fluid chamber 16. During the
discharge stroke of the plunger 28, the plunger 28 is extended from
the plunger bore 20a into the fluid chamber 16, whereby the plunger
28 forces the fluid in the fluid chamber 16 through the discharge
valve 23b and into the discharge port 25.
[0026] The plunger 28 slides through a packing arrangement 30
mounted at an end of the plunger bore 20a. In one illustrative
embodiment, as shown in FIG. 2, the packing arrangement 30 includes
a packing housing 31 that is attached to the pump fluid end 12,
near the end of the plunger bore 20a, by removable attachment means
such as a threaded connection and the like. The packing housing 31
carries a packing assembly 33, which comprises a set of seals 35.
The packing assembly 33 circumscribes the outer diameter of the
plunger 28. The arrangement of the packing assembly 33 is such that
there will be a small clearance between the opposing surfaces of
the packing assembly 33 and the plunger 28 so as to avoid damage to
the surface of the plunger 28 as the plunger 28 slides through the
packing assembly 33. By removably attaching the packing housing 31
to the pump fluid end 12, replacement of the packing assembly 33
will be relatively easy during maintenance of the plunger pump
10.
[0027] In one illustrative embodiment, as shown in FIG. 3, the
plunger 28 has a plunger body 36 with an inner cavity 38, a closed
end 39, and open end 40. The plunger body 36 may have a cylindrical
shape, for example. An end cap 42 covers the open end 40 of the
plunger body 36. The end cap 42 has an opening 45 that is
configured to receive one end of an adapter plate (50 in FIG. 1A)
of the crank mechanism (34 in FIG. 1A). In an alternate embodiment,
the end cap 42 may be adapted for connection to an extension rod
instead of an adapter plate. The joint 43 between the end cap 42
and plunger body 36 may be fluid tight. Such fluid tightness may be
achieved by welding, seals, and the like. In one embodiment, the
plunger body 36 and end cap 42 are made of weldable materials and
are joined together by welding. After the welding, a hardened
coating is applied to the surface of the plunger 28 to protect the
plunger 28 from the environment and improve wear characteristics.
The coating may be surface ground to a desired finish.
[0028] The inner cavity 38 occupies a substantial volume of the
plunger body 36. For example, the inner cavity 38 may occupy 30% to
60% of the volume of the plunger body 36. The plunger 28 with the
inner cavity 38 will have a substantially reduced weight compared
to a solid plunger made of the same material and size.
[0029] In one embodiment, an insert 44 is disposed inside the inner
cavity 38 to increase the stiffness of the plunger 28 and prevent
diametric deflection of the plunger 28 under load. That is, the
combined stiffness of the insert 44 and plunger body 36 is greater
than the stiffness of the plunger body 36 alone. In one embodiment,
one of the properties of the insert 44 is that the shape and size
of the insert 44 are such that there is an interference fit between
the inner surface 46 of the plunger body 36 and the outer surface
48 of the insert 44. The interference fit between the surfaces 46,
48 will place the plunger body 36 in tension during the relaxed
state of the plunger pump, such as during the suction stroke of the
pump. This tension will act as a pre-tension that will help to
partially counteract hydraulic forces encountered during the
discharge stroke of the pump. Another property of the insert 44 may
be that the stiffness of the insert 44 is comparable to, e.g.,
approximately equal to, or higher than the stiffness of the plunger
body 36. Stiffness is a measure of rigidity of a body and is a
function of material properties and geometry.
[0030] In one embodiment, the shape of the insert 44 is the same as
the shape of the inner cavity 38. For example, both the insert 44
and inner cavity 38 could be cylindrical in shape. In one
embodiment, the volume of the insert 44 is substantially less than
the volume of the inner cavity 38. For example, the volume of the
insert 44 may be 30% to 70% of the volume of the inner cavity 38.
The length of the insert 44 may be the same as or may be shorter
than the length of the inner cavity 38. The insert 44 may be hollow
as shown or may be solid. In general, a hollow insert will add less
weight to the plunger 28 compared to a solid insert of the same
material and length. For overall weight management of the plunger
28, the insert 44 along with the plunger body 36 and end cap 42 may
be made of lightweight material such as aluminum. However, it is
possible to use alternate materials for construction of these
parts, from low cost steel to extremely lightweight composites.
Also, it is not necessary that the material of the insert 44 is the
same as that of the plunger body 36 and end cap 42.
[0031] Returning to FIG. 1A, the crank mechanism 34 includes,
generally in order, an adapter plate 50, a crosshead 54, a
connecting rod 56, and a crankshaft 60. One end of the adapter
plate 50 is inserted into an opening in the end cap 42 of the
plunger 28 (also, see FIG. 3). The adapter plate 50 may be secured
to the end cap 42 using any suitable means, such as a welded or
threaded connection. The other end of the adapter plate 50 is
rigidly attached to one end of the crosshead 54. Therefore, the
adapter plate 50 couples the plunger 28 to the crosshead 54. In an
alternate embodiment, the adapter plate 50 could be replaced by an
extension rod, where the extension rod would couple the plunger 28
to the crosshead 54.
[0032] The crosshead 54 is arranged inside a cylinder 26 supported
inside the pump power end 14. The axial axis of the cylinder 26 is
generally aligned with that of the plunger bore 20a. The connecting
rod 56 is coupled at one end to the crosshead 54 and at the other
end to the crankshaft 60. As the crankshaft 60 rotates, the
connecting rod 56 will transfer this rotational motion to the
crosshead 54. Because the crosshead 54 is constrained to move
linearly by the cylinder 26, the rotational motion will be
converted into reciprocating motion, which will be transferred to
the plunger 28 via the adapter plate 50.
[0033] As mentioned earlier, an extension rod may be used in lieu
of an adapter plate to couple the plunger to the crosshead. FIG. 1B
shows a pump 10a including an extension rod 55 extending between a
plunger 28a and a crosshead 54a. One end of the extension rod 55 is
secured to the plunger 28a by a clamp 57. Other attachment methods
besides a clamp may be used between the extension rod 5 and plunger
28a, such as a threaded connection. The other end of the extension
rod 55 may include a flange that is secured to the crosshead 54a by
means of bolts. It is also possible to attach the extension rod 55
to the crosshead 54a by other methods besides a bolted flange. The
plunger 28a is similar in structure to the plunger 28 of FIG. 1A,
and the crosshead 54a is similar in structure to the crosshead 54
of FIG. 1A. The other parts of pump 10a not described are similar
to the corresponding pump parts in FIG. 1A. Extension rods are more
common in mobile short stroke pump applications to help isolate the
power end from potential contamination from either the fluid end or
ambient environment and to help ease routine maintenance.
[0034] FIG. 4A shows a connecting rod and crosshead assembly
including the crosshead 54 and the connecting rod 56. The crosshead
54 has a crosshead body 62, which may be generally cylindrical in
shape. In the cross-section shown in FIG. 4B, there is a divider
wall 64 inside the crosshead body 62, with openings 66, 68 on
either side of the divider wall 64. The opening 66 is for receiving
one end of the adapter plate (50 in FIG. 1A) or extension rod (55
in FIG. 1B). The end of the adapter plate (or extension rod)
received through the opening 66 will be rigidly attached to the
side of the divider wall 64 facing the opening 66. The opening 68
is for receiving one end of the connecting rod 56. The divider wall
64 includes a surface 70 shaped to mate with a head 72 of the
connecting rod 56. (The entire length of the connecting rod 56 is
not shown in FIG. 4B.) A bearing 73 is mounted to the surface 70 to
support pivoting or rotation of the head 72 relative to the surface
70. The bearing 73 will be between the surface 70 and the head 72
when the connecting rod 56 is coupled to the crosshead 54. The
bearing 73 may be retained to the divider wall 64 by means of a
retainer plate 75 or other suitable means.
[0035] In FIG. 4C, holes 71, 74 are formed in the wall of the
crosshead body 62. The holes 71, 74 are axially aligned and both
intersect with the opening 68 of the crosshead body 62. A hole 76
runs through the connecting rod head 72. To couple the connecting
rod 56 to the crosshead 54, the connecting rod head 72 is inserted
into the crosshead body opening 68 such that hole 76 in the head 72
is axially aligned with the holes 71, 74 in the wall of the
crosshead body 62. Then, a wrist pin (or retainer pin) 78 is
inserted into the aligned holes 71, 74, 76. In one embodiment, the
wrist pin 78 is retained to the connecting rod 56 such that the
wrist pin 78 does not rotate relative to the connecting rod 56 but
rotates in unison with the connecting rod 56. In one embodiment,
the sizing of the wrist pin 78 and connecting rod head hole 76 is
such that there is an interference fit between the connecting rod
56 (or the connecting rod head 72) and the wrist pin 78, thereby
increasing the compressive stiffness of the assembly. The wrist pin
78 also can rotate within the holes 71, 74 and relative to the
crosshead body 62. Bushings 77, 79 may be arranged in the holes 71,
74 to support rotation of the wrist pin 78 within the holes 71,
74.
[0036] Retaining the wrist pin 78 to the connecting rod 56 as
described above eliminates the need to provide a wrist pin bearing
internally within the connecting rod, i.e., within the hole 76, to
support rotation of the wrist pin 78. If a wrist pin bearing had to
be provided in the hole 76, it would be necessary to maintain an
annular space between the wrist pin and the wrist pin bearing for
lubrication film and to prevent load transfer from the relatively
large connecting rod end to the much smaller wrist pin, especially
during the pump's discharge stroke. However, the annular space will
allow deformation of the connecting rod bearing surface during high
load conditions, creating uneven loading and premature bearing
failure, such as galling. The need for a wrist pin bearing, and
annular space between the wrist pin and wrist pin bearing, is
eliminated by retaining the wrist pin 78 to the connecting rod 56
such that the wrist pin 78 and connecting rod 56 essentially form a
single body.
[0037] The wrist pin 78 may be retained to the connecting rod 56 by
a suitable retainer fastener. In the embodiment of FIG. 4B, the
connecting rod head 72 has a side hole 84 that intersects with the
hole 76 in the connecting rod head 72. Also, the wrist pin 78 has a
hole 82 that can be aligned with the side hole 84. A retainer
fastener 80 is inserted through the side hole 84 in the connector
rod head 72 into the hole 82 in the wrist pin 78. In one
embodiment, the retainer fastener 80 is in the form of a bolt with
a threaded shank. The retainer fastener 80 is threaded through the
side hole 84 until its tip is received in the hole 82 of the wrist
pin 78. With the retainer fastener 80 extending into the hole 82,
the wrist pin 78 will be prevented from rotating within the hole 76
in the connecting rod head 72. The retainer fastener 80 is retained
to connecting rod head 72, e.g., by means of a threaded connection
or other means, thereby ensuring that the retainer fastener 80 will
not pop out of the hole 82 in the wrist pin 78. With this
arrangement, the wrist pin 78 will rotate in unison with the
connecting rod 56. The crosshead body 62 may have an access port 86
to allow access to the side hole 84 after the connecting rod head
72 has been inserted into the crosshead body opening 68.
[0038] FIG. 5 shows another illustrative embodiment of a connecting
rod and crosshead assembly including a crosshead 54a and a
connecting rod 56a. (The entire length of the connecting rod 56a is
not shown in FIG. 5.) In the embodiment of FIG. 5, the crosshead
54a has a crosshead body 62a with a divider wall 64a inside the
crosshead body 62a and openings 66a, 68a on either side of the
divider wall 64a. Axially aligned holes 71a, 74a run through the
wall of the crosshead body 62a. The head 72a of the connecting rod
56a has a hole 76a that is axially aligned with the holes 71a, 74a
when the head 72a is inserted in the opening 68a. A wrist pin (or
retainer pin) 78a is inserted through the aligned holes 71a, 74a,
76a, thereby coupling the connector rod 56a to the crosshead 54a.
In one embodiment, the wrist pin 78a is retained to the connecting
rod head 72a by means of a retainer fastener 80a. The retainer
fastener 80a is inserted through an interior hole 84a running down
the length of the connecting rod 56a into an aligned hole 82a in
the wrist pin 78a. With the retainer fastener 80a extending into
the hole 82a in the wrist pin 78a, the wrist pin 78a will be
prevented from rotating within the hole 76a in the connecting rod
head 72a. The retainer fastener 80a is retained to the head 72a,
e.g., by means of a threaded connection or other means, thereby
ensuring that the retainer fastener 80a will not pop out of the
wrist pin hole 82a. With this arrangement, the wrist pin 78a will
rotate in unison with the connecting rod 56a. A bearing 73a may be
provided between the connecting rod head 72a and the surface 70a of
the divider wall 64a to support rotation of the connecting rod 56
relative to the crosshead 54a. Similarly, bushings 77a, 79a may be
provided between the wrist pin 78a and the crosshead body 62a to
support rotation of the wrist pin 78a within the holes 71a,
74a.
[0039] FIG. 6 shows another illustrative embodiment of a connecting
rod and crosshead assembly including a crosshead 54b and a
connecting rod 56b. (The entire length of the connecting rod 56a is
not shown in FIG. 6.) The crosshead 54b is similar to the crosshead
54a described with reference to FIG. 5. In the embodiment of FIG.
6, surface holes 96, 98 are formed in the sides of the head 72b of
the connecting rod 56b. To couple the connecting rod 56b to the
crosshead 54b, the connecting rod head 72b is inserted into the
opening 68b of the crosshead body 62b such that the surface holes
96, 98 are aligned with the holes 71b, 74b in the wall of the
crosshead body 62b. Wrist pins (or retainer pins) 78b1, 78b2 are
inserted into the aligned holes 71b, 96 and 74b, 98, respectively.
The wrist pins 78b1, 78b2 are retained to the crosshead body 62b by
retainer rings 101, 103. In this embodiment, the wrist pins 78b1,
78b2 will be stationary relative to the crosshead body 62b and will
not rotate in unison with the connecting rod 56b. The connecting
rod 56b will rotate relative to the wrist pins 78b1, 78b2 and the
surface 70b of the crosshead body 62b. A bearing 73b can be mounted
in between the surface 70b and the connecting rod head 72b to
support rotation of the connecting rod 56b.
[0040] In all the embodiments described above, lubrication ports
may be provided as necessary to allow lubricant to be applied to
the bearing and bushing surfaces.
[0041] Returning to FIG. 1A, an end cover 100 is mounted at an end
of the discharge bore 18b. The end cover 100 is held in place by a
retainer 102 that is secured to the pump fluid end 12 by means of,
for example, a threaded connection. The discharge valve 23b is
mounted below the end cover 100 and is biased against a discharge
valve seat 104b by means of a spring 106b. The discharge valve 23b
is lifted off the discharge valve seat 104b when the force of the
fluid from the fluid chamber 16 overcomes the force of the spring
106b. When the discharge valve 23b is lifted off the discharge
valve seat 104b, fluid will flow into a space 108b in between the
discharge valve 23b and the end cover 100 and then exit through the
discharge port 25.
[0042] A valve cage retainer 110 is arranged in the fluid chamber
16 and attached to the pump fluid end 12. The suction valve 23a is
mounted below the valve cage retainer 110 and is biased against a
suction valve seat 104a by means of a spring 106a. The suction
valve 23a is lifted off the suction valve seat 104a when the force
of the fluid from the suction manifold 21 overcomes the force of
the spring 106a. When the suction valve 23a is lifted off the
suction valve seat 104a, fluid will flow into the fluid chamber 16.
The arrangement of the valve cage retainer 110 is such that the
valve cage retainer 110 does not prevent the plunger 28 from
extending into the fluid chamber 16. A removable end cover 112 may
be mounted in the access bore 20b opposite to the plunger 28.
[0043] In FIG. 1A, the suction bore 18a intersects with the access
bore 20b and the plunger bore 20a. Also, the discharge bore 18b
intersects with the access bore 20b and the plunger bore 20a. The
fluid chamber 16 is defined at the intersection of all these bores.
Abrupt transitions at these intersections are avoided through the
use of tapered bores and fillet surfaces. This has the effect of
reducing localized stress concentrations inside the pump fluid end
12.
[0044] FIG. 7 shows a fluid passage geometry of the pump fluid end
12 according to one illustrative embodiment. The suction bore 18a
includes a tapered suction valve seat bore 114 and a straight
suction valve bore 116. The straight suction valve bore 116 is
connected to the plunger bore 20a and the access bore 20b by a
fillet surface 124. The discharge bore 18b includes a tapered
discharge valve seat bore 120 and a straight discharge valve bore
122. The discharge bore 18b is connected to the plunger bore 20a
and access bore 20b via a combination of a fillet surface 126, a
reduced diameter bore 128, a tapered bore 130, and an enlarged
diameter bore 132. The bores 128, 132 are straight bores in one
embodiment. In alternate embodiments, they could be tapered
bores.
[0045] The fillet surfaces 124, 126 remove the material that
typically exhibits high stress levels in the pump fluid end,
greatly improving the overall strength of the pump fluid end. The
reduced diameter bore 128 also helps improve the structure
integrity of the discharge bore 18b. In addition, the tapered
discharge valve seat bore 120 is translated away from the plunger
axis 134. This allows a smoother transition between the fluid
chamber 16 and the discharge valve seat bore 120.
[0046] While exemplary embodiments of the invention have been
described herein, skilled in the art, having benefit of this
disclosure, will appreciate that other embodiments can be devised
which do not depart from the scope of the invention as claimed
herein. Accordingly, the scope of the invention should be limited
only by the attached claims.
* * * * *