Note: Descriptions are shown in the official language in which they were submitted.
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SELF PILOTED CHECK VALVE
BACKGROUND OF THE INVENTION
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of U.S. Serial No.
13/066,817
filed April 26, 2011, entitled "Self Piloted Check Valve" by inventor Larry
Rayner Russell,
which claims the benefit under USC 119 of the filing date of provisional
application Serial No.
61/343,381 filed April 28, 2011 entitled "Check Valve."
FIELD OF THE INVENTION
[0002] The present invention relates in general to a method and apparatus
for controlling
fluid flow using a check valve. More particularly, the invention relates to a
self piloted check
valve for controlling fluid flow in high vibration environments.
DESCRIPTION OF THE RELATED ART
[0003] Check valves are used in a wide variety of applications.
Historically,
conventional check valves are generally the least reliable type of valve. This
is a consequence of
flow for an open valve continually passing both the seat and the sealing plug
or ball of those
check valves. This problem can lead to very rapid valve failure, particularly
in abrasive flow
applications or when larger objects pass by the valve. Oilfield applications,
particularly use in
the drilling of wells, typically cause conventional poppet valves or flapper
valves to leak in 15
hours or less of service. Such check valve applications are particularly
critical, since they
provide the first line of defense against well blowouts.
[0004] Another major problem for any check valve is survival in
high vibration
environments. Relative motion of components resulting from high vibrations can
rapidly induce
wear in the constituent valve components, particularly in abrasive
environments, such as oilfield
drilling muds or slurries. When a valve is used immediately above the bit in
oilfield drilling, it is
commonly termed a "float valve". Float valves are exposed to very high
vibratory accelerations
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of 10 times gravity or more while passing flows often in excess of 600 gallons
per minute.
Relative motion of adjacent parts in the abrasive drilling fluid environment
can cause rapid wear
sufficient to cause misalignment between the sealing member of a valve and its
valve seat.
[0005] The earlier self piloted check valve, covered by U. S.
Patents 4,220,176 and
4,254,836, performs exceptionally well in nonvibratory environments. While the
check valve
covered by these earlier patents is exceptionally durable and can in general
operate without
maintenance for much longer periods than other types of check valve,
improvements to the
existing design are needed in its resistance to vibration induced wear caused
by vibrational
relative motion between valve components.
[0006] A critical need exists for an improved check valve which has
enhanced resistance
to both flow induced and vibration induced wear.
SUMMARY OF THE INVENTION
[0007] Embodiments of the present invention include a self piloted
check valve which
utilizes closure of a piloting flapper valve to permit development of closure
forces for a ball
valve. The normally open ball valve has a central flow passage and
simultaneously rotates and
translates as it traverses between its fully open and fully closed positions.
An opening bias
system utilizes a combination of a first less stiff spring and a second
stiffer spring. Reversible
decoupling means disconnects and reconnects the second spring at a short
travel distance from
the normally open position of the ball, while the first spring always provides
opening bias forces
to the ball. The pressure induced force required to fully close the ball valve
following
decoupling of the second spring is more than the force required to overcome
the combination of
the first and second springs.
[0008] One embodiment of the present invention is a valve apparatus
comprising: (a) a
tubular body having a main counterbore; and (b) a plurality of internal
valving components
housed within the main counterbore, wherein the internal valving components
have a first end
and a second end transverse to the main counterbore, the internal valving
components including:
(i) a ball seat having a seat flow passage; (ii) a ball valve having a flow
passage, wherein the ball
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valve is movable with simultaneous directly related rotation and translation
to a first ball position
with the flow passage in axial alignment with the main counterbore of the
tubular body, a second
ball position abutting the ball seat wherein the flow passage is not in fluid
communication with
the seat flow passage such that the main counterbore of the tubular body and
the flow passage
are closed, and a third ball position intermediate between the first and
second ball positions; (iii)
a pilot valve mounted within the ball valve flow passage, the pilot valve
comprising a plurality of
flappers, wherein each flapper is rotatable between a closed position and an
open position and a
plurality of flapper bias springs wherein each flapper spring biases a flapper
toward the closed
position; and (iv) a spring biasing system for providing a bias on the ball
valve, the spring
biasing system including a first spring and a second spring, wherein the first
spring provides a
continuous bias on the ball valve to urge the ball valve towards the first
ball position and wherein
the second spring is activated to bias the ball valve towards the first ball
position only when the
ball valve is at the first ball position or when the ball valve is moving
between the first ball
position and the third ball position.
[0009] A second embodiment of the present invention is a valve apparatus
comprising:
(a) a tubular body having a main counterbore; and (b) a plurality of internal
valving components
housed within the main counterbore, wherein the internal valving components
have a first end
and a second end transverse to the main counterbore, the internal valving
components including:
(i) a ball seat having a seat flow passage; (ii) a ball valve having a flow
passage, wherein the ball
valve is movable with simultaneous directly related rotation about an axis of
rotation and
translation to a first ball position with the flow passage in axial alignment
with the main
counterbore of the tubular body and a second ball position abutting the ball
seat wherein the flow
passage is not in fluid communication with the seat flow passage such that the
main counterbore
of the tubular body and the flow passage is closed; (iii) a spring biasing
system for providing a
bias on the ball valve, the spring biasing system including a reciprocable
latching system, a first
spring and a second spring, wherein the first spring provides a continuous
bias on the ball valve
to urge the ball valve towards the first ball position and wherein the second
spring is activated
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only when the ball valve is at the first ball position or moving between the
first ball position and
the third ball position; and (iv) a pilot valve mounted within the ball valve
flow passage, the pilot
valve comprising a plurality of flappers wherein each flapper is rotatable
between a closed
position and an open position and a plurality of flapper bias springs wherein
each flapper bias
spring biases a flapper toward the closed position; whereby a fluid flowing in
a first direction
from the first end of the valving components toward the second end of the
valving components
with sufficient force to overcome the bias of the flapper bias springs rotates
the flappers to the
open position allowing fluid flow through the ball valve flow passage and
wherein the fluid
flowing in a second direction from the second end of the valving components
toward the first end
of the valving components with sufficient force against the flappers in the
closed position to
overcome the bias of the first and second springs will cause the ball valve to
rotate to the second
ball position.
[0010] A third embodiment of the present invention is A valve
apparatus comprising: (a)
a tubular body having a main counterbore; and (b) a plurality of internal
valving components
housed within the main counterbore, wherein the internal valving components
have a first end
and a second end transverse to the main counterbore, the internal valving
components including:
(i) a ball valve having a flow passage, wherein the ball valve is movable with
simultaneous
directly related rotation about an axis of rotation and translation to a first
ball position with the
flow passage in axial alignment with the main counterbore of the tubular body
and to a second
ball position such that the main counterbore of the tubular body and the valve
flow passage are
closed to fluid flow; (ii) a ball seat having a seat flow passage, wherein
when the ball valve is in
the second ball position a spherical surface of the ball valve sealingly abuts
a comatable
spherical surface of the ball seat such that fluid flow past the ball seat is
prevented and the ball
flow passage is not in fluid communication with the seat flow passage; (iii) a
ball cage that
supports the ball valve, wherein the ball cage is stationarily positioned in
the main counterbore of
the tubular body and eccentrically engages the ball valve eccentric to a ball
valve axis of rotation
through a pair of opposed eccentric pins mounted on the ball cage; (iv) a
spring biasing system
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for providing a bias on the ball valve, the spring biasing system comprising:
a ball pusher seat
having a ball side and an opposed side, wherein the ball side bears against a
first side of the ball
valve; a tubular ball pusher mounted on the opposed side of the ball pusher
seat, wherein the
internal diameter of the ball pusher equals the diameter of the flow passage
of the ball valve; a
spring retainer, wherein a portion of the spring retainer encircles a portion
of the ball pusher; a
first spring; a second spring; and a reciprocable latching mechanism, wherein
the latching
mechanism is coupled to the ball pusher when the ball valve is in the first
ball position, the
latching mechanism uncouples at an intermediate point when the ball valve is
moving from the
first ball position to the second ball position and recouples at the
intermediate point when the ball
valve is moving between the second ball position and the first ball position,
and the latching
mechanism is coupled to the spring retainer when the ball valve is in the
second ball position.;
and (v) a pilot valve mounted within the ball valve flow passage, the pilot
valve comprising a
plurality of flappers, each flapper rotatable between a closed position and an
open position,
wherein a flapper bias spring biases each flapper toward the closed position;
whereby a fluid
flowing in a first direction from the first end of the valving components
toward the second end of
the valving components with sufficient force to overcome the bias of the
flapper bias springs
rotates the flappers to the open position allowing fluid flow through the ball
valve flow passage
and wherein the fluid flowing in a second direction from the second end of the
valving
components toward the first end of the valving components with sufficient
force against the
flappers in the closed position to overcome the bias of the first and second
springs will cause the
ball valve to rotate to the second ball position.
[0011] The foregoing has outlined rather broadly several aspects of
the present invention
in order that the detailed description of the invention that follows may be
better understood.
Additional features and advantages of the invention will be described
hereinafter which form the
subject of the claims of the invention. It should be appreciated by those
skilled in the art that the
conception and the specific embodiment disclosed might be readily utilized as
a basis for
modifying or redesigning the structures for carrying out the same purposes as
the invention. It
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should be realized by those skilled in the art that such equivalent
constructions do not depart
from the spirit and scope of the invention as set forth in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a more complete understanding of the present invention,
and the advantages
thereof, reference is now made to the following descriptions taken in
conjunction with the
accompanying drawings, in which:
[0013] FIGURE 1 shows a longitudinal section taken of the check
valve housed in a
tubular body suitable for connection into an oilfield drill string, whereby it
can operate as an
inside blowout preventer valve.
[0014] FIGURE 2 shows a longitudinal section corresponding to Figure I, but
showing
only the internal component parts of the valve in its open, flowing condition.
In this case, the
ball is biased open by the action of two coacting, separate springs.
[0015] FIGURE 3 shows a longitudinal sectional view corresponding
to Figure 2, but
with the piloting flapper valve closed and the ball open. This view shows the
valve in its normal
position when flow has ceased, but there is no back pressure. In this
position, the ball is still
biased open by the action of two coacting, separate springs.
[0016] FIGURE 4 is a longitudinal section corresponding to Figures
2 and 3, but showing
the valve with the ball forced sufficiently upstream by back pressure from its
position in Figure 2
that the latch assembly with its secondary spring nearing disengagement or
reengagement from
the ball pusher. The ball pusher in this case continues to apply a reduced
opening spring bias
force from a single spring to the upstream side of the ball.
[0017] FIGURE 5 is a longitudinal section corresponding to Figures
2, 3, and 4, but
showing the ball fully seated in response to reverse flow so that reverse flow
through the self
piloted check valve is prevented.
[0018] FIGURE 6 is an exploded oblique view of the ball cage assembly.
[0019] FIGURE 7 is an exploded oblique view of the flappers and
seat of the piloting
flapper valve assembly.
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[0020] FIGURE 8 is an exploded oblique view of the latch assembly.
[0021] FIGURE 9 is an exploded oblique coaxially aligned view of
the piloting flapper
assembly and ball.
[0022] FIGURE 10 is an exploded oblique view of the components used
to retain the
valve internals within the body of the inside blowout preventer body.
[0023] FIGURE 11 is an axial view of the closed piloting flapper
and seat assembly for
the inside blowout preventer version of the self piloted check valve.
[0024] FIGURE 12 is an axial view of the closed flapper and seat
assembly for the choke
and kill manifold version of the self piloted check valve.
[0025] FIGURE 13 is a longitudinal sectional view of a choke and kill check
valve.
[0026] FIGURE 14 is a longitudinal sectional view of a float valve
version of the check
valve.
[0027] FIGURE 15 is a figure illustrating the valve opening bias
force versus distance
relationship.
[0028] FIGURE 16 is a detail view taken within the circle 16 shown in
Figure 4. The
view shows the relationship of the latch balls and their adjacent parts at the
time that a
disconnection or reconnection of the secondary spring biased trigger sleeve to
the ball pusher
occurs when the ball valve is respectively closing or reopening.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The self piloted check valve of the present invention is generally
suitable for high
reliability applications where no rapid cycling of the valve is required. The
materials of the
valve typically are low alloy steel, with elastomeric seals sealing between
parts as required. The
flappers will be an abrasion resistant material such as a wear resistant
cobalt alloy. With only
minor or no modifications, the basic internals of the self piloted check valve
are suitable for use
with several different housing body types, as described below in three
examples.
[0030] Inside Blowout Preventer Valve
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[0031] One embodiment of the check valve is suitable for placement
in an inside blowout
preventer valve (inside BOP). Referring to Figure 1, one embodiment of the
self piloted check
valve 10 is shown in a longitudinal sectional view as an inside blowout
preventer, wherein its
internal components 20 are mounted in a body 11 suitable for interconnection
into an oilfield
drillstring. Provision is also made to use a split retention ring 100 and an
interior support ring
101 with a snap ring 102 to retain the valve internal components 20 in the
body 11.
[0032] The exterior of the inside blowout preventer body 11 has a
constant outer
diameter over most of its length and a reduced diameter tapered male thread 12
at its first, lower
end. Herein, the terms upper and lower refer respectively to the normal flow
inlet and the
normal flow outlet. Sequentially from its upper end, the body 11 has a tapered
female thread 13,
a straight main bore 14 interrupted by an axially short retention groove 16
near its upper end and
having a transverse lower end, and a straight reduced diameter outlet bore 15
having a short
downwardly increasing diameter tapered bore at its lower end. To avoid stress
concentrations,
an ample radius is used at the transition between the lower end of the main
bore 14 and the outlet
bore 15. The external corners of the short retention groove 16 are also
radiused for the same
reason.
[0033] The primary check valve 10 internal components 20 include a
ball stop 21, a ball
cage assembly 24, a ball assembly 33 including an internal flapper valve
assembly 34 and a main
ball 53 valve, a ball pusher assembly 70, a main spring 78 and spacer sleeve
80, a latch assembly
84, a spring retainer 90, and a retaining means (e.g., split retention ring
100, interior support ring
101, and snap ring 102) to retain the inside blowout preventer internal
components in the
body 11.
[0034] Referring to Figure 2, the internal components 20 of the
valve 10 of Figure 1 are
shown removed from the inside of the blowout preventer body valve 11. At the
lower, normal
outflow end, the valve has a ball stop 21 with an integrally molded
elastomeric ball stop bumper
22 for cushioning the impact of ball 53 on the ball assembly 33 when the valve
10 opens rapidly.
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[0035] The ball stop 21 is an axially short annular ring which,
starting from its transverse
lower end, has on its exterior a large taper, a short constant diameter
section, a transverse
external upwardly facing shoulder, and a constant reduced diameter axially
upward extension.
The constant reduced diameter axially upward extension closely conforms to the
inner diameter
of the semicircular end arm 26 half rings on the ends of the ball cage halves
25 of the ball cage
assembly 24. The outer diameter of the short constant outer diameter section
of the ball stop is a
close slip fit to the main bore 14 of the body 11 of the inside blowout
preventer 10.
[0036] From its lower interior end, the ball stop 21 has a small
chamfer, a very short
constant diameter minimum bore, a frustroconical upwardly increasing bore, a
groove for
containing a molded-in elastomeric ball stop bumper 22, and a spherical bore
intersecting a
radially narrow transverse upper end. The spherical bore of the ball stop 21
has the same
diameter as that of the ball 53, so that the open ball 53 can abut the ball
stop with good support
over a relatively large contact surface. The elastomeric molded in ball stop
bumper 22 extends a
short distance inwardly from the spherical bore of the ball stop 21 so that it
cushions the contact
of the axially translating ball 53 with the ball stop 21 when the valve 10 is
opening.
[0037] The ball cage assembly 24, shown in Figure 6, consists of
two opposed mirror
image semicylindrical halves 25. Each ball cage half is symmetrical about its
midplane
perpendicular to the semicylindrical axis. At both its upper and lower ends, a
ball cage half 25
has identical thin, axially short semicylindrical end arms 26 which have a
constant rectangular
cross section, wherein the radial thickness of the arm is approximately a
quarter of the axial
length of the arm.
[0038] The outer diameter of the semicylindrical surface of the
arms 26 is a close slip fit
to the main bore 14 of the body 11 for the valve 10. The inner diameter of an
arm 26 closely
conforms to the constant reduced outer diameter portion of the lower ball stop
21, with which it
is mated in the assembled valve. The width of the arm 26 in the axial
direction is the same as the
length of the reduced constant outer diameter portion of the ball stop 21, and
the upward looking
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intermediate transverse external shoulder of the ball stop abuts the lower
side of the arm 26 of
each installed ball cage half 25.
[0039] The middle portion of the ball cage half 25 has a
cylindrical outer face 27 and a
flat internal face 28 which mounts an inwardly extending cylindrical camming
pin 29 which is
normal to the face 28. The outer diameter of the middle section cylindrical
surface 27 is the
same as that of the semicircular end arms 26 and is also a close slip fit to
the main bore 14 of the
body 11 for the valve 10. The middle portion of the ball cage half 25 is
symmetrically
positioned between the end arms 26 so that the cylindrical external face 27
matches the outer
diameter of the end arms 26. Also, the center of the middle portion of the
ball cage half 25
matches the center of the arc of each of the semicircular end arms 26.
[0040] Symmetrically placed in the middle of the middle portion of
each ball cage half
25 is a ball guide groove 30 parallel to the axis of the inside blowout
preventer internal
components 20. Groove 30 fully penetrates the middle section of the ball cage
half 25. The
groove 30 extends in the axial direction perpendicular to the flat internal
face 28 and has
semicircular ends with parallel flat sides. An inwardly extending cylindrical
camming pin 29 is
located at midlength of the ball cage half 25 and offset to one side of the
ball guide groove 20.
[0041] The ball assembly 33 consists of a ball 53, a snap ring 59,
and a piloting valve
assembly 34 which is mounted internally in the ball 53, as indicated in an
exploded view in
Figure 9. The flapper valve assembly 34 is shown in exploded view in Figure 7.
The flapper
valve assembly 34 primarily consists of a flapper seat ring 35, a flapper
shroud 40, and three
flappers 44. The flappers 44 are individually connected to trunnions 37 on the
flapper seat ring
35 by flapper pivot pins 48 and are biased to be normally closed by torsional
flapper springs 46.
[0042] The flapper seat ring 35 is a cylindrical ring having a
transverse seating surface 36
and a right circular cylindrical coaxial through bore. The diameter of the
through bore is the
same as the diameter of the through hole for the ball 53. On its exterior
surface, a short right
circular cylindrical surface adjoins the seating surface 36 and is joined by a
fillet to a
frustroconical end surface opposed to the seating surface 36. A male annular 0-
ring groove
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containing externally sealing 0-ring 50 is positioned on the frustroconical
face of the flapper seat
ring 35.
[0043] Mounted on 120 spacings on seating surface 36 of the
flapper seat ring 35 are
three flapper support trunnions 37. Each flapper support trunnion 37 consists
of a pair of mirror
image spaced apart projections normal to the seating surface 36. The trunnions
37 each have a
hinge bore parallel to the surface of the seating surface 36 and perpendicular
to the midplane of
that trunnion 37.
[0044] On the external cylindrical side of the flapper seat ring 35
between the trunnion
37 halves, flat bottom spring recesses parallel to the axis of symmetry of the
ring are machined to
provide clearance and support for the reaction arms of the torsional flapper
bias springs 46.
Equispaced on a circular pattern and symmetrically placed between each
adjacent pair of
trunnions 37 is a small diameter blind alignment pin hole 38 parallel to the
axis of symmetry of
the flapper seat ring and penetrating the seating surface. The alignment pins
39 are short roll
pins which have an interference fit with the alignment pin holes 38.
[0045] The flapper shroud 40 is a right circular cylindrical annular ring
having a length
equal to about 80% of its outer diameter. The outer diameter of the flapper
shroud 40 matches
that of the flapper seat ring 35. As seen in Figures 7 and 9, the flapper
recesses 41 are three
radially penetrating identical windows located at 120 spacings in the flapper
shroud. The
recesses 41 are cut in the flapper shroud 40 from its first end to closely
accommodate the open
flappers 44 of the flapper and seat assembly 34. The flapper recesses 41 are
symmetrical about
their radial midplanes and have parallel sides extending approximately half of
the axial length of
the shroud 40. The inner end of each flapper recess 41 has converging opposed
sides each
inclined at 60 from the radial midplane of the recess.
[0046] The first end of the flapper shroud 40 has three small
diameter blind holes parallel
to the part axis in the same pattern as the alignment pin holes 38 of the
flapper seat ring 35 and
with each hole located midway between adjacent flapper recesses 41. These
holes have an
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interference fit with the alignment roll pins 39 of the flapper seat ring 35
and serve to permit the
roll pins to firmly connect the shroud with the seat ring.
[0047] The flappers 44 are three identical abrasion resistant metal
pieces made of a
material such as a wear resistant cobalt alloy. The flappers 44 have a planar
sealing face on a
first side and have a single plane of symmetry perpendicular to their sealing
face. A second
planar face is opposed and parallel to the planar flapper sealing face and
extends in the direction
of the plane of symmetry. The width of the second planar face is approximately
30% of the
width of the flapper 44 perpendicular to its plane of symmetry. Outboard of
the second planar
face on each side, the thickness of the flappers 44 is reduced linearly as a
function of the distance
from its intersection with the second planar face.
[0048] Viewing a flapper 44 normal to its sealing face, two mirror
image first planar
edge faces, each normal to the sealing face, are each inclined at 60 from the
plane of symmetry
and extend to small planar edge outer ends parallel to the plane of symmetry.
The first planar
edge faces will be adjacent to corresponding faces of adjacent flappers 44
when they are
assembled in their closed positions in the flapper and seat assembly 34, as
shown in Figure 11.
[0049] Short second planar edge faces, inclined at 45 from the
plane of symmetry and
perpendicular to the sealing surface 36, extend inwardly towards the plane of
symmetry from the
small planar outer ends of the flapper 44. Adjoining the second planar faces
on the side towards
the plane of symmetry are symmetrically placed short planar faces
perpendicular to both the
plane of symmetry and the sealing surface on the first side of the flapper.
These second planar
edge faces on their inward ends are joined by third planar edge faces
perpendicular to the sealing
surface 36 and parallel to the plane of symmetry. The separation of the third
planar edge faces is
approximately the width of the second planar face which is opposed to the
sealing surface on the
first side of the flapper.
[0050] On the third planar edge faces, through hinge holes are drilled at
mid thickness of
the flappers 44 and perpendicular to the midplane of symmetry. The outer end
of a flapper 44
where its hinge holes are positioned is radiused about the axis of the hinge
holes. A central gap,
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with sides parallel to the plane of symmetry, extending inwardly in the
direction of the plane of
symmetry is cut between the third planar faces. This central gap is wide
enough to accommodate
a torsional flapper bias spring 46. The second planar face opposed to the
sealing face of the
flapper 44 has a shallow central notch parallel to the sealing face and plane
of symmetry and
intersecting the central gap of the flapper 44. This shallow central notch
provides a spring slot
for a reaction point for an arm of the torsional flapper bias spring 46.
[0051] The flapper pivot pins 48 are elongated cylindrical rods
with multiple
symmetrically placed molded narrow elastomerie rings on their outer ends. The
flapper pivot
pins 48 are engaged both in the hinge holes of the flappers 44 and in the
trunnion holes of the
flapper seat ring 35. The elastomeric rings permit the flappers to seal with
the seating surface 36
of the flapper seat ring 35 in spite of small deviations in hole locations for
the flappers 44 and the
trunnions 37 of the flapper seat ring.
[0052] Referring to Figures 7 and 11, the flapper and seat assembly
34 is seen to have
three flappers 44 mounted to the flapper seat ring 35 by flapper pivot pins
48. The individual
torsional flapper springs 46, seen in Figure 7, are located surrounding the
pins 48 in the central
gaps of the flappers 44 with one arm of the spring bearing on the shallow slot
of a flapper and the
other on a spring slot on the outer diameter of the flapper seat ring 35.
[0053] To complete the flapper and seat assembly 34, an 0-ring 50
is installed into the
groove on the frustroconical face of the flapper seat ring 35 and the flapper
shroud 40 is attached
to the flapper seat ring by alignment roll pins 39 engaged in the holes 38 of
the ring 35 and the
corresponding holes in the flapper shroud 40. The closed set of flappers 44
has only a slight
clearance between adjacent flappers to prevent mutual interference. For this
reason, the flappers
44 do not form a bubble tight seal when seated on the flapper seat ring 35.
[0054] The open flappers 44 also fit with only small clearance gaps
into the flapper
recesses 41 of the flapper shroud 40. The large planar sealing faces of the
open flappers 44 are
open sufficiently to permit passage of a body having the same outer diameter
as the bore through
the flapper seat ring 35. While the flapper valve assembly is shown with three
flappers herein,
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closure of the flow passage of the ball can be achieved with only one or two
flappers or more
than three. Utilizing three flappers permits a reduction in the mass of
individual flappers while
minimizing leak paths. Additionally, use of three flappers simplifies
construction of the shroud
40.
[0055] As seen in Figure 9, the ball 53 has a spherical outer surface with
two mirror
image parallel flats on its exterior. The outer diameter of the spherical face
of the ball 53 is only
slightly less than the main bore 14 of the flowpath of the valve body 11. Each
flat of the ball 53
has a central cylindrical guide pin 55 which is normal to its flat and is a
close slip fit to a ball
guide groove 30 of a ball cage half 25. The opposed guide pins 55 are located
on a common ball
diameter. Parallel to and centrally located between the opposed flats of the
ball 53 is a through
bore 57. From its large end, the through bore 57 has a long larger straight
bore with a snap ring
groove 58 near its outer end, an inwardly extending frustroconical face, and a
shorter smaller
straight fluid entry bore.
[0056] The smaller bore diameter for the ball 53 is the same as the
central bore through
the flapper seat ring 35. These two bore diameters determine the through
clearance hole for the
valve 10. A fillet connects the frustroconical face and the larger bore. The
snap ring groove 58
accommodates snap ring 59 so that when the flapper and seat assembly 34 is
inserted in the
larger portion of the bore 57 of the ball 53 with the orientation shown in
Figure 9, it is retained
with the 0-ring 50 in the annular groove of the flapper seat ring sealing
between the ball and the
flapper seat ring 35.
[0057] A shallow camming groove 56 is cut into each flat of the
ball in a radial direction
of the face, with the opposed grooves being parallel and mirror images
relative to the midplane
of symmetry of the ball. The inner ends of the camming grooves 56 are radiused
and spaced
apart from the guide pins 55. The camming grooves 56 extend outwardly to the
spherical surface
of the ball 53. The orientation of the camming grooves 56 is such that the
through bore 57 of the
ball 53 is aligned with the valve axis when the ball is open and engaged in
the ball cage assembly
24.
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[0058] When the valve 10 is closed by the ball, the longitudinal
axis of the valve 10
penetrates the spherical face of the ball 53 midway between the exits of the
large exit hole and of
the small exit hole of bore 57 of the ball on the plane of symmetry of the
ball. This necessitates
that the axis of the camming grooves 56 to be inclined from the axis of the
ball bore 57 by an
angle of more than 45 .
[0059] The main seat 62 of the valve, shown in Figure 2, is an
axially relatively short
hollow cylinder having a transverse upper end with a smaller relieved
transverse face on its
interior side. The relieved face, which provides clearance for a snap ring 74
of the ball pusher
assembly 70, is connected to the larger transverse end by a short
frustroconical section. The bore
of the main seat 62 is straight and larger than the smaller bore through the
ball 53 in order to
permit a slip fit of the lower exterior end of the ball pusher assembly 70.
[0060] The exterior cylindrical face of the main seat 62 has, from
its upper end, a
constant diameter first section extending about half of the axial length of
the seat and with an
intermediately placed male 0-ring groove containing an 0-ring 65 and a backup
ring 66. The
outer diameter of the first section of the exterior cylindrical face of the
main seat 62 is a close
slip fit to the main bore 14 of the body 11 of the valve 10. The 0-ring 65
seals between the main
seat 62 and the main bore 14 of the body 11.
[0061] On its lower end, the exterior cylindrical face of the main
seat 62 has an inwardly
extending transverse shoulder facing downwardly. A second section having a
reduced diameter
cylindrical section extends downwardly to a short inwardly extending
transverse shoulder. The
outer diameter of the second cylindrical section is a close fit to the inner
cylindrical face of the
semicircular end arms 26 of the ball cage halves 25, and the length of the
second cylindrical
section is the same as the axial length of a ball cage end arm 26.
[0062] On its lower end, the main seat 62 has on its interior side
a spherical face 63
having the same diameter as the ball 53 and having an intermediate seal ring
groove. The seal
ring groove is undercut and contains a molded in elastomeric face seal 64
which extends radially
inwardly from the spherical face 63 of the seat 62. However, the net volume of
the molded in
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elastomeric face seal is less than the volume of the groove in the main seat
62 due to molded
ridging of the exposed face of the seal 64. This permits the avoidance of
extrusive seal damage
when the ball 53 forcefully abuts the spherical face of the main seat 62.
[0063] When the inside blowout preventer internal components 20 of
the valve 10 are
being assembled, the ball assembly 33 with its ball 53 and flapper and seat
assembly 34 is held
between two opposed ball cage halves 25 so that its guide pins 55 are engaged
in the ball guide
grooves 30 of the ball cage assembly 24 and the camming pins 29 of the ball
cage assembly are
engaged with the camming grooves 56 of the ball.
[0064] The lower ball stop 21 is then engaged with the lower
semicircular end arms 26 of
the ball cage assembly 24 so that the side of the lower ball stop with the
molded in ball stop
bumper 22 is facing the ball. Following this, the main seat is engaged with
the upper
semicircular end arms 26 of the ball cage assembly so that the side of the
main seat with the
spherical face 63 is facing the ball. The resultant subassembly has a slip fit
with the main bore
14 of the body 11. An 0-ring 65 with a backup ring 66 seals the annular gap
between the main
seat 62 and the main bore 14 of the body 11.
[0065] The ball pusher assembly 70 consists of ball pusher body
71, a ball pusher seat
73, a snap ring 74, and a spring washer 75. The ball pusher body 71 is an
elongated thin wall
right circular cylindrical tube having a transverse external annular latch
groove 72 located at
about 30% of the length of the ball pusher body from its upper end.
Additionally, an external
snap ring groove mounting snap ring 74 is located at about 60% of the length
of the ball pusher
body 71 from its upper end. The bore of the ball pusher body 71 is the same as
the smaller bore
through the ball 53. The latch groove 72 is relative shallow and narrow, with
frustroconical
radially outwardly opening faces inclined at approximately 60 from the axis
of the ball pusher
body 71 joining the groove to the outer diameter portion of the ball pusher
body 71.
[0066] At its lower end, the ball pusher body 71 has a female thread which
is threadedly
engaged with the male thread of a ball pusher seat 73. The ball pusher seat 73
is axially short
and has the same inner and outer diameters as the ball pusher body 71. The
ball pusher seat 73 is
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fabricated from either an elastomer or a plastic polymer such as a glass
filled
polytetrafluoroethylene. The lower face of the ball pusher seat 73 has a
concave frustroconical
or spherical face which is able to sealingly bear on the spherical face of the
ball 53. At its upper
end, the ball pusher seat 73 has a reduced diameter male thread comatable with
the female thread
on the ball pusher body 71.
[0067] The spring washer 75 is a relatively thin cylindrical flat
washer with a central hole
which is a close slip fit to the outer diameter of the ball pusher body 71.
The outer diameter of
the spring washer 75 is slightly less than the bore of the spacer sleeve 80 so
that it also has a
close slip fit to that sleeve. The spring washer 75 is located on the upper
side of the mounted
snap ring 74 and bears against the snap ring. In turn, the lower end of the
helical main spring 78
bears against the upper side of the spring washer 75 and when the spring is
compressed, it urges
the ball pusher assembly 70 downwardly so that the ball pusher seat 73
normally remains in
contact with the ball 53. The upper end of the main spring 78 bears against a
downwardly facing
transverse shoulder of the spring retainer 90.
[0068] The spacer sleeve 80 is a thin wall right circular cylindrical
sleeve with transverse
ends and the central portion of its outer diameter slightly relieved. The
outer diameter of the
spacer sleeve is a slip fit to the main bore 14 of the body 11 of the valve
10. The outer diameter
of the main spring 78 has sufficient clearance with the bore of the spacer
sleeve 80 to ensure
clearance, even when the main spring is fully compressed. The spacer sleeve 80
has a length
equal to about 75% of its outer diameter and abuts against both the upper end
of the main seat 62
and the larger diameter lower transverse face of the spring retainer 90.
[0069] The latch assembly 84 consists of an axially short thin wall
right circular
cylindrical latch sleeve 85, multiple latch balls 86, and a secondary spring
87. The inner
diameter of the latch sleeve 85 is a slip fit to the outer diameter of the
ball pusher body 71. The
latch sleeve 85 is provided with multiple equispaced radial holes in a
transverse plane located at
midlength of the sleeve. The radial holes are close tits to the latch balls
86.
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[0070] The radial wall of the latch sleeve 85 is approximately 60%
of the diameter of the
latch balls 86. When the radial holes of the latch sleeve 85 are positioned to
be coplanar with the
middle of the annular latch groove 72 of the ball pusher body 71, the latch
balls 86 positioned in
the radial holes and abutting the minimum diameter portion of the latch groove
72 do not extend
beyond the outer diameter of the latch sleeve 85.
[0071] The secondary spring 87 of the latch assembly 84 is a stiff
short helical spring
with an inner diameter slightly larger than the outer diameter of the ball
pusher body 71 and an
outer diameter slightly smaller than that of the latch sleeve 85. The
secondary spring 87 is
mounted coaxially with the spring retainer 90 and the latch sleeve 85 of the
latch assembly 84.
The secondary spring 87 bears against the upper end of the latch sleeve 85 and
a downwardly
facing transverse end of a downwardly opening interior secondary spring recess
92 of the spring
retainer 90.
[0072] The spring rate of the secondary spring 87 is higher than
that of the main spring
78, but the maximum axial force applied to the ball pusher assembly 70 by the
secondary spring
87 is less than the maximum force ever applied to the spring washer 75 of the
ball pusher by the
main spring 78. Further, the maximum combined force of the main spring 78 and
the secondary
spring 87 is less than the peak force on the ball pusher assembly 70 applied
by the main spring
78 alone.
[0073] The force from the secondary spring 87 acts on the latch
sleeve 85 and also the
ball pusher assembly 70 as long as the latch sleeve is engaged with the ball
pusher assembly by
the latch balls 86. The releasable interconnection which permits axial loads
to be transferred
from the radial holes of the latch sleeve 85 to the annular latch groove 72 of
the ball pusher body
71 is provided by the radially reciprocable latch balls 86, which are radially
reciprocable in the
radial holes of the latch sleeve.
[0074] The spring retainer 90 is a right circular cylindrical sleeve with a
length slightly
longer than its outer diameter. From its upper end, the spring retainer 90 has
on its exterior side
a first cylindrical section which has an outer diameter which is a close slip
fit to the main bore 14
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of the body 11 of the valve 10. This first section has a length equal to
approximately half of the
total length of the spring retainer and contains an annular male 0-ring groove
91 mounting an 0-
ring 96 and backup ring 98 which provide sealing between the spring retainer
90 and the main
bore 14 of the valve body 11.
[0075] An inwardly extending downwardly facing intermediate transverse
shoulder on
the lower end of the first cylindrical section connects to a reduced diameter
second external
cylindrical section which extends to the lower end of the spring retainer 90.
The outer diameter
of the second external cylindrical section is such that it provides clearance
to the inner diameter
of the main spring 78. The intermediate downwardly facing shoulder abuts both
the upper end of
the main spring 78 and the upper end of the spacer sleeve 80. A chamfer joins
the lower end of
the second external cylindrical section to a narrow downwardly facing
transverse end.
[0076] From its lower end, the bore of the spring retainer 90 has a
first counterbore with
a transverse inner end serving as a secondary spring recess 92 and containing
an intermediate
female annular latch groove 93. The annular latch groove 93 has a short
central enlarged
constant diameter section with radially inwardly opening chamfers at its upper
and lower ends
extending to the counterbore for the secondary spring recess 92. The angle of
these chamfers
from the axis of the spring retainer 90 is approximately 60 .
[0077] The depth of the annular latch groove 93 is such that, when
a latch ball 86 is
positioned in the groove at its maximum radially outward position, the
innermost portion of the
ball will clear the outer diameter of the ball pusher assembly 70. The
diameter of the
counterbore of the secondary spring recess 92 is a close slip fit to the outer
diameter of the latch
sleeve 85. The length of the secondary spring recess is sufficiently long to
fully contain the
installed secondary spring 85 and most of the length of the latch sleeve 85
when the secondary
spring 87 is fully compressed.
[0078] Adjoining the secondary spring recess 92 at its upper end is a
smaller short
straight bore which contains an intermediate female 0-ring groove 94 mounting
0-ring 97. The
diameter of this bore is such that it has a close slip fit with the outer
diameter of the ball pusher
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body 71. The 0-ring 97 seals between the spring retainer 90 and the outer
diameter of the ball
pusher assembly 70.
[0079] At the upper end of the short straight bore with 0-ring
groove 94, an intermediate
complex counterbore provides a female landing profile 95 for a lock-open tool
which is not
described herein. This concave profile varies, depending upon the type of lock-
open tool to be
used with the valve. Upwardly sequentially from the lower end of profile 95
are located an
outwardly opening chamfer, a first profile counterbore, another upwardly
opening chamfer, a
larger second profile counterbore, a narrow female groove, and a short
inwardly extending
shoulder which has a counterbore smaller than that of the second counterbore.
[0080] The inwardly extending shoulder and the female groove of the landing
profile 95
permit the extraction, using a puller device, of the spring retainer 90 from
the main bore 14 of the
body 11 of the valve 10 during valve disassembly. For the assembled valve 10,
the upper
transverse face of the spring retainer 90 is adjacent to the lower end of the
latch groove 16 of the
body 11 of the valve.
[0081] The inside blowout preventer internal components 20 of the valve 10
are retained
within the body 11 of the valve by the combination of the installed split
retention ring 100, the
solid interior support ring 101, and the male snap ring 102. Referring to
Figure 10, these
components can be seen in an exploded view. The split retention ring 100 has a
cross section
with a straight interior bore having near its upper end a female snap ring
groove for the mounting
of snap ring 102. The lower transverse end of the cross section of the split
retention ring 100 is
joined to the right circular cylindrical external side by a liberally radiused
corner.
[0082] Near its upper end, the cross section of the external
cylindrical side of the split
retention ring 100 has a short reduced diameter section joined to the larger
diameter section
below, with a second radiused upper corner serving as the transition to the
reduced diameter
section. The radius of both external corners of the larger outer diameter
section is the same. The
outer diameter of the split retention ring is a close fit to the diameter of
the groove 16 of the body
11. The outer diameter of the reduced diameter section at the upper end of the
ring 100 is a slip
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fit to the main bore of the body 11 of the valve 10. The length of the larger
diameter portion of
the split retention ring 100 is equal to or slightly less than the axial
length of the latch groove 16
of the valve body 11.
[0083] As seen in Figure 10, the split retention ring 100 is
separated into four parts by
two parallel cuts made parallel to but equally offset to opposite sides from
the axis of symmetry
of the part. The length of the longer segments of the ring 100 is less than
the diameter of the
main bore 14 of the body 11 of the valve 10. This permits the radial insertion
of the
diametrically opposed longer segments of the split retention ring 100 into
groove 16 of the body
11 followed by the radial insertion of the shorter segments of the split ring
100 into the gaps
between the longer segments. The upper transverse end of the spring retainer
90 of the other
assembled valve internals 20 is abutted on its upper end by the downwardly
facing transverse
shoulder of the split retention ring 100.
[0084] The interior support ring 101 has an outer diameter which
is a close slip fit to the
straight interior bore of the installed split retention ring 100. The length
of the interior support
ring 101 is just slightly less than the distance from the lower transverse end
to the lower side of
the female retaining ring groove of the split retention ring 100. The interior
support ring 101 has
two opposed narrow transverse ends. The interior side of the interior support
ring has from its
upper end a frustroconical converging counterbore, a downwardly facing
transverse shoulder,
and a downwardly facing short counterbore engagable by a puller tool so that
the ring can readily
be extracted during valve 10 disassembly.
[0085] When the interior support ring 101 is inserted within the
bore of the assembled
split retention ring 100, the split retention ring is trapped within the
groove 16 of the body 11 of
the valve 10. In this position, the split retention ring 100 abuts the upper
end of the spring
retainer 90 so that the internal components 20 of the inside blowout preventer
are maintained in
position within the body 11 of the valve.
[0086] This is the case even when the closed valve 10 is resisting
high pressures from
reverse flow tendencies acting on its ball 53. The forces from pressure on the
closed ball 53 and
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seat 62 are transferred through the split ring and into the groove 16 of the
body 11. Insertion of
the snap ring 102 into the female snap ring groove of the split retention ring
retains the interior
support ring 101 within the bore of the split retention ring, but when removed
readily permits
selective disassembly and removal of the rings 100, 101 so that the valve
internals 20 can be
removed.
[0087] Choke and Kill Manifold Check Valve
[0088] Figure 13 shows a longitudinal sectional view of one
embodiment of the self
piloted check valve mounted in a body arrangement having weld neck flanges
suitable for
connection into an oilfield drilling choke and kill piping system. This choke
and kill valve 200
has internal components which are functionally the same as those of the inside
blowout preventer
valve 10 with the exception of the structure and behavior of the flappers of
the flapper and seat
assembly 234 of the valve 200. Where minor structural differences exist
between the inside
blowout preventer 10 and the choke and kill valve 200, the modifications are
described herein.
[0089] In the case of the flappers 244, the structural change is minor and
produces only a
slightly exaggerated valve behavior which is exhibited to some degree for all
versions of the
valve. Most of the internal parts of the choke and kill manifold check valve
200 are structurally
identical to those of the inside blowout preventer 10. Other than the changes
to the flappers 244,
minor changes to some parts are necessitated for mounting the valve internals
in a different type
of body, but both those parts and the choke and kill manifold valve 200
function in substantially
the same manner as the inside blowout preventer 10.
[0090] Referring to Figure 13, the choke and kill valve body 201 is
a right circular
cylindrical body with a constant outer diameter equal to approximately 65
percent of its length.
At its first end, the body 201 has a short fluid entry bore 202 which has a
diameter equal to the
inner diameter of the valve internals 220. The main bore 203 is a counterbore
for the entry bore
202 and enters from the end opposed to the end with the fluid entry bore 202
and has a diameter
which is a close slip fit to the choke and kill valve internal components 220.
The length of the
22
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main bore 203 is such that the valve internals 220 can be fitted into the bore
both with allowance
for fabrication tolerances and without interfering with mounting of the large
seal 208 and the
large flange 215.
[0091]
Both ends of the choke and kill valve body 201 are provided with regular
arrays
of drilled and tapped holes for engagement by flange bolting. The
drilled and tapped holes
are parallel and equally offset from the longitudinal axis of the body 201. On
its outer end the
fluid entry bore 202 has a short inwardly converging frustroconical small seal
recess 204 which
mounts a commercially available small diameter metallic seal 205.
[0092]
The annular small metallic seal 205 has a thin central flange on its outer
side with
a straight through bore equal to that of the short fluid entry bore 202. The
seal 205 has mirror
image seal surfaces which externally radially inwardly taper with distance
from the central
flange. The tapered seal surfaces seal with an interference fit with the small
seal recesses 204
and 211 when the seal flange is clamped between the body 201 and the small
flange 210.
[0093]
On its outer end the main bore 203 has a short inwardly converging
frustroconical
large seal recess 207 which mounts a large diameter metallic seal 208. The
annular large
diameter metallic seal 208 has the same type of construction and operation as
that of the small
metallic seal 205, with the only difference being related to seal size. The
tapered large seal
surfaces seal with an interference fit with the large seal recesses 207 and
216 when the seal
flange is clamped between the body 201 and the large flange 215.
[0094] The
small flange 210 is a typical bolted weld neck flange, but it has a seal
groove
appropriate for use with seal 205. The outer diameter of the small flange 210
is the same as that
of the body 201 and its through bore is the same as that of the valve
internals 220. Flange 210
has a regularly spaced pattern of bolt holes offset from its axis of symmetry
corresponding to
those on the inlet end of the body 201 and a cylindrical weld neck that
extends outwardly on the
back side of the flange. On the entry to the through bore on the side facing
the valve body 201,
the flange 210 has a small seal recess 211 identical to the small seal recess
204 of the body.
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Studs 212 and nuts 213 are used to clamp the small flange 210 to the body 201
and to energize
the seal 205.
[0095] The large flange 215 also is a typical bolted weld neck
flange, but thicker than the
small flange 210. The outer diameter of the large flange 215 is the same as
that of the body 201
and its through bore is the same as that of the valve internals 220. Flange
215 has a regularly
spaced pattern of bolt holes corresponding to those at the exit of the main
bore 203 of the body
201.
[0096] On its axis of symmetry, the large flange 215 has a
cylindrical weld neck which
extends outwardly on the outer side of the flange. On the entry to the through
bore on the side
facing the valve body 201, the flange 215 has a large seal recess 216
identical to the large seal
recess 207 of the body. Studs 212 and nuts 213 are used to clamp the large
flange 215 to the
body 201 and to energize the seal 208.
[0097] As shown herein, the seal groove diameter for mounting the
small flange 210 is
smaller than that for the large flange 215, although the groove and flange for
the fluid entry bore
end could alternatively be made identical with that for the fluid exit end of
the valve 200.
[0098] The choke and kill valve internal components 220 include a
choke and kill valve
lower ball stop 221, a choke and kill flapper assembly 234 with flappers 244,
and a choke and
kill spring retainer 290. Other than the flappers, these components differ
only slightly
structurally but not functionally from the corresponding components of the
inside blowout
preventer 10. The other choke and kill valve internal components 220 are the
same as for the
inside blowout preventer 10, with the exception that the split retention ring
100, the interior
support ring 101, and the snap ring 102 are omitted. These omitted parts are
not required
because the large flange 215 serves to retain the valve internal components
220 in the valve body
201 so that they bear against the inwardly extending shoulder at the small
flange end of the valve
200.
[0099] Referring to Figure 13, the choke and kill lower ball stop
221 with its molded-in
ball stop bumper 22 does not need the large chamfer on its external flow
outlet corner that the
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inside blowout preventer ball stop 21 requires to fit in body 11. That corner
for the choke and
kill ball stop 221 is only lightly chamfered, and the axial length of the ball
stop 221 is slightly
reduced from that of ball stop 21 for the inside blowout preventer in order to
limit the overall
length of the valve. Otherwise, the ball stop 221 and its molded in bumper are
structurally and
functionally identical to the lower ball stop 21 of the inside blowout
preventer 10.
[00100] For the choke and kill manifold valve 200, the ball cage
assembly 24, ball 53, and
main seat 62 are the same as for the inside blowout preventer 10 and are
assembled with the
same relationships. The ball stop 221 and the main seat 62 support the opposed
halves 25 of the
ball cage assembly 24. The ball 53 has its guide pins 55 engaged in the ball
guide groove 30 of
the ball cage assembly 24 in the same way as for the inside blowout preventer
10. The camming
grooves 56 of the ball 53 are engaged by the camming pins 29 of the ball cage
halves 25 in the
same manner as for the inside blowout preventer 10.
[00101] The flapper and seat assembly 234 of the valve 200 is
identical to the
corresponding assembly 34 for the inside blowout preventer except for use of
flappers 244 for
valve 200. Referring to Figures 11 and 12, the flapper and seat assemblies 34
of the inside
blowout preventer 10 and 234 of the valve 200 are respectively shown in axial
views seen from
their outlet sides.
[00102] Only small clearance gaps sufficient for operating
clearances between adjacent
flapper 44 faces are provided for the inside blowout preventer 10 flapper and
seat assembly 34
shown in Figure 11. However, some limited backflow is necessary for the choke
and kill
manifold valve 200 in order to accommodate valve backflows due to fluid
displacement during
wireline or coiled tubing operations while still providing protection against
dangerous higher
flows. For the choke and kill manifold valve 200, the gaps between adjacent
flapper faces 244
are made larger to permit this additional reverse flow, as seen in Figure 12.
The desired size of
the gap for the flappers 244 can be determined readily by calculation.
[00103] The ball pusher assembly 70, the main spring 78, the spacer
sleeve 80, and the
latch assembly 84 are common to both the choke and kill check valve 200 and
the inside blowout
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preventer 10 and function the same in both devices. The choke and kill spring
retainer 290 is
different from the spring retainer 90 for the inside blowout preventer valve
10 because no
provision for lock open tools is required for valve 200. However, the bore on
the inlet end of the
spring retainer 290 is enlarged sufficiently to permit engagement with puller
or pusher means
(not shown) to forcibly extract the choke and kill valve internals 220 from
the body 201 for
servicing.
[00104] Drilling Float Valve
[00105] Figure 14 shows a longitudinal sectional view of one
embodiment of a drilling
float valve 300 installed in a housing for mounting between a drill bit and
the drill collars of a
drill string. Drilling float valves are routinely used near the drill bit to
avoid uncontrolled
backflows through the drillstring during the making of connections. The
primary differences
between float valves and inside blowout preventers are related to their bodies
and provisions for
the severe vibrational environment near the bit for float valves. Float valves
are used routinely,
rather than for emergencies, and are particularly important when the well is
being drilled in an
underbalanced condition.
[00106] The float valve 300 uses the same self piloted check valve
with internal
components which are functionally the same as those of the inside blowout
preventer valve 10.
The float valve body 301 differs from those of the inside blowout preventer 10
and the choke and
kill valve 200. Most of the internal parts of the drilling float valve 300 are
structurally identical
to those of the inside blowout preventer 10 or the choke and kill manifold
valve 200. Minor
changes to some internal parts are necessitated for mounting the valve
internals in a different
type of body, but both those parts and the assembled valve 300 function in the
same manner as
for the inside blowout preventer 10. Some additional parts are required to
ameliorate the high
vibration problem for the float valve 300, but those parts do not affect the
principles or manner
of the flow controlling operation of the key valve components.
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[00107] Referring to Figure 14, the drilling float valve body 301
has a right circular
cylindrical body with a constant outer diameter equal to approximately 25% of
its length. At its
transverse upper first end, the body 301 has a tapered female drill pipe
thread so that it can be
threadedly interconnected into a drill string. At the lower end of the upper
thread, a
frustroconical transition section that downwardly reduces in diameter connects
to a straight fluid
entry bore 303 which has a diameter equal to or slightly greater than the
inner diameter of the
float valve internal components 320.
[00108] The initial length of the fluid entry bore 303 is between 50
percent and 100
percent of the diameter of body 301. This length permits several recuts of the
threads on the
upper end of the body 301. The fluid entry bore 303 is joined to the larger
main bore 302 by a
transverse shoulder 305 which has a filleted intersection with the transverse
shoulder. At its
lower fluid outlet end 304, the body 301 has a female drill pipe thread for
connection with the
threaded shank 308 of a drill bit. A slightly tapered, upwardly converging
short frustroconical
transition connects the lower female thread with the main bore 302.
[00109] The transverse shoulder 305 forms the upper end of the main bore
303 of the body
301. The main bore 302 has a diameter which is a close slip fit to the float
valve internal
components 320, permitting the male 0-rings of the float valve internal
components to seal
against the main bore. The length of the main bore 302 is such that the valve
internals 320 can
be fitted into the bore along with upper 310 and lower 314 damper assemblies
and axial space
filler rings 318, 319.
[00110] The axial space filler rings 318, 319 are required to fill
axial gaps between the
valve internals 320 and the upper end of the drill bit shank 308 without
interfering with the
threaded make up of a drill bit shank into the female oilfield thread at the
outlet lower end of the
body 301. The depth of the internal shoulder 305 of the body 301 is initially
made larger in
order to provide space for recutting worn lower end threads. This initial
extra length creates the
need for the first 318 and second 319 filler rings. The axial length of the
individual filler rings
318, 319 corresponds to the length of the body 301 removed during a thread
recutting operation.
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[00111] The upper damper assembly 310 consists of an upper damper
retainer ring 311, an
annular upper damper elastomeric element 312, and a upper damper abutment ring
313. The
outer diameter of the upper damper assembly 310 is a slip fit to the main bore
302 of the body
301. The outer diameters of the rings 311 and 313 are close slip fits to the
main bore 302 of the
body 301. Typically, the upper and lower ends of the elastomeric element 312
are bonded
respectively to the end rings 311, 313. The upper damper retainer ring 311 has
a straight bore, a
narrow transverse lower end, an upwardly extending external cylindrical face,
a downwardly
facing and outwardly extending transverse face, and a radiused shoulder
connecting to a narrow
transverse upper end which extends to the straight bore.
[00112] The upper damper elastomeric element 312 is an annular cylinder
which has equal
transverse ends. The outer cylindrical face has a reduced diameter in its
central portion, while
the inner cylindrical face has an increased diameter in its central portion.
Multiple equispaced
radial holes penetrate through the middle portions of the elastomeric element
312. The upper
damper abutment ring 313 has a right circular cylindrical outer face adjoined
to two relatively
narrow transverse ends. The bore through the ring 313 is frustroconical and
opens upwardly.
The outer diameters of rings 311 and 313 and the transverse ends of the
elastomeric element 312
are the same. The inner diameters of the rings 311 and 313 are less than the
inner diameter of
the elastomeric element 312.
[00113] The lower damper 314 is a cylindrical assembly of end
support rings and an
elastomeric element which is symmetric about its transverse midplane and which
has a loose slip
fit with the main bore 302 of the body 301. The cross-sections of the upper
312 and the lower
316 elastomeric damper elements differ, so that they exhibit different
stiffness properties. Two
opposed identical thin flat annular rings serve as lower damper support rings
315. The lower
damper elastomeric element 316 is constructed similarly to the upper damper
elastomeric
element 312. The rings 315 are respectively bonded to the opposed upper and
lower transverse
ends of the lower damper elastomeric element 316. Different properties of the
elastomeric
elements 312 and 316 may be selected. For example, durometers, compositions,
and hence
28
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stiffness properties of the elastomers of different embodiments of the
elastomeric elements 312
and 316 may be selectively varied. Thus, the cross-sectional profiles of the
elastomeric elements
312 and 316 may be varied as required for different operating conditions.
[00114] Both the upper 310 and the lower 314 dampers are required
to be compressed
when the valve internals 320 are retained in the body 301 by the drill bit
shank 308. By
supporting the valve internals between the elastomeric upper 310 and lower 315
dampers, the
accelerations and resultant forces applied during drilling to the float valve
internal components
are reduced by energy absorption in the elastomeric elements 312 and 316. The
differences in
cross-sections and elastomeric properties cause the two dampers 310 and 314 to
have different
frequency responses and vibrational energy absorption characteristics.
[00115] Because the body 301 of a float valve is subject to severe
operating conditions, its
end threads are frequently recut with associated shortening of the valve body.
First 318 and
second 319 filler rings may be used to avoid the need to remachine the main
bore 302 of the
valve 300 whenever the threads at the lower end of the body 301 are recut.
[00116] Each cylindrical lower filler ring 318, 319 has a length equal to
the length
removed during a single thread recut. The first filler ring 318 has a
downwardly extending
annular outer ridge on its lower transverse face which closely comates with a
corresponding
outer annular groove on the upper transverse face of the second filler ring
319 in order to
maintain axial alignment of the rings. Both rings 318 and 319 are a close slip
fit to the main bore
302 of the float valve body 301. After the first thread recut on the lower
flow outlet end of the
body 301, the first filler ring 318 is removed and only the second ring 319 is
used. Following a
second thread recut on the lower end of the float valve body, the second
filler ring 319 is also
removed.
[00117] With the exception of the upper 310 and lower 314 dampers,
the first 318 and
second 319 filler rings, and the flappers 44 of the flapper and seat assembly
34, the float valve
internal components 320 are identical to those of the choke and kill manifold
valve 200. The
primary components include a choke and kill valve lower ball stop 221 and
spring retainer 290
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that differ structurally but not functionally from the corresponding
components of the inside
blowout preventer 10. The split retention ring 100, the interior support ring
101, and the snap
ring 102 are omitted. These omitted parts are not required because the shank
308 of the drill bit
serves to retain the components 320 in the valve body 301.
[00118] The float valve 300 internal components 320 also include a ball
cage assembly 24,
a ball assembly with internal flapper and seat assembly 34 using flappers 44,
a ball 53, a main
seat 62, a ball pusher assembly 70, and a latch assembly 84 with latch balls
86. Other than the
flappers, these components are common to all three types of valve.
[00119] OPERATION OF THE INVENTION
[00120] The unidirectional flow control provided by the self piloted
check valve works
substantially the same in all configurations 10, 200, and 300 despite their
being housed in a
variety of bodies and minor component changes to accommodate those bodies and
their service
conditions. For simplicity, the description of valve operation first will
treat the inside blowout
preventer embodiment 10 of the self piloted check valve, since all embodiments
work in the
same manner with only minor differences. For the other two versions of the
valve, the
differences in behavior from that exhibited by the inside blowout preventer 10
will be noted.
[00121] As seen in Figures 1, 2, 3, 4, and 5, the self piloted check
valve 10 disclosed
herein uses a ball valve 53 with a central flow passage 57 to seal against
reverse flow by
blocking the cylindrical axial flow path through the body 11 and, excluding
the piloting flapper
valve assembly 34, the assemblage of other internal parts of the valve. The
valve 10 prevents
backflows by using a ball 53 having a through flow passage 57 which is
supported in a ball cage
24 so that it simultaneously translates axially on the longitudinal axis of
the valve 10 and rotates
about a ball axis transverse to the longitudinal axis of the valve 10. The
axis of rotation of the
ball 53 is also the axis of the guide pins 55 of the ball. The ball 53 moves
between a fully open
first position with the ball flow path aligned with the axis of valve 10 and a
fully closed second
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position with the ball bore flow path out of alignment with the valve axis and
the ball 53 bearing
against the main seat 62 and sealing against the main seat.
[00122]
The ball 53 of the improved self piloted check valve 10 has two spaced apart
opposed limits to its movements along the valve axis. The lower ball stop 21,
shown in Figures
1, 2, and 3, determines a first limit to ball 53 travel at the valve open
position, while abutting the
main seat 62 as seen in Figure 5 determines a second limit to ball travel at
the valve closed
position. The positioning of the spherical face of the ball stop 21 and the
spherical face of the
main seat 62 relative to the camming pins 29 of the ball cage halves 25
determines the
alignments of the ball bore 57 at the limits of its axial travel in the valve.
[00123] An
analytically determinable relationship relates rotation of ball 53 from its
fully
open position to the linear travel distance of the ball from its fully open
position. If is the
rotation of the ball from its fully open position, x is the linear movement of
the ball from its fully
open position, y is the lateral offset of the camming pins 29 from the plane
of the ball guide
grooves 30 of the installed ball cage assembly 24, and xma) is the distance
from the middle of the
range of ball travel to the fully open ball position, then = Arctangent
XMID -
Arctangent ((xlvan - / 31).
[00124]
At the middle of the range of ball travel, the axis of the ball guide pins
57 and the
axis of the camming pins 29 lie in the same plane transverse to the axis of
the valve body 11.
[00125]
The ball 53 is provided with a stepped cylindrical internal through flow
passage
bore 57 which can permit flow when the ball 53 is in its first, open position
with its bore 57
aligned with the valve 10 longitudinal axis. When the ball 53 is in its
second, closed position,
the flow passage bore 57 of the ball 53 is out of alignment with the
longitudinal axis of the valve
10 and the outer spherical surface of the ball is in engagement with the
molded-in elastomeric
seal 64 of the valve seat 62 to block flow through the valve, as seen in
Figure 5. When the ball
53 is closed and seated, flow around the main seat 62 is blocked by both the 0-
ring 65 with its
backup ring pair 66 and the molded-in elastomeric seal 64.
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[00126] The opposed ball flats parallel to and laterally offset from
the flow passage 57 of
the ball 53 mount central guide pins 55 which have axes that intersect the
axis of the ball through
bore 57 at right angles. These ball guide pins 55 and the flats of the ball 53
coact with the ball
guide grooves 30 and flat internal faces 28 of the ball cage halves 25 to
maintain the ball guide
pin 55 axis perpendicular to and intersecting with the longitudinal axis of
the valve 10.
[00127] The two mirror image ball camming grooves 56 are cut into
the face of each
opposed flat of the ball 53 with one groove per side. These grooves 56 extend
outwardly in the
radial direction relative to the guide pins 55 on the flats of the ball 53.
The axes of the camming
pins 29 of the stationary ball cage halves 25 are laterally offset from the
ball rotational axis
defined by the pins of the mounted ball. The camming pins 29 are also offset
from the
longitudinal axis of the valve 10 and are engaged with the camming grooves 56
of the ball 53.
[00128] When force acting along the longitudinal axis of the valve
is applied to the ball
53, the ball tends to translate along the valve axis. At the same time, the
eccentric camming pins
29 abut the sides of the camming grooves 56 of the ball 53 to produce reaction
forces on the
sides of the ball grooves 56. The component parallel to the axis of valve 10
of these reactions on
the sides of the ball grooves 56 acting at a separation from the ball
rotational axis, together with
the force tending to move the ball 53 along the valve axis, constitute a force
couple acting on the
ball. This resultant force couple produces the simultaneous rotation of the
ball 53 to accompany
its axial movement.
[00129] A downwardly acting spring bias is used to urge the ball valve 53
to its normally
open condition where it permits exiting flow through the valve 10, while
separate torsional
spring 46 biases are used to urge the flappers 44 of the piloting flapper
valve 34 to their normally
closed positions. With the flapper and seat assembly 34 mounted in the
counterbored annular
recess in the through bore 57 of the ball 53, closure of the flappers 44
prevents or strongly
restricts reverse flow through the ball. The flappers 44 readily open in
response to forces
induced on them by exiting flows moving in the normal flow direction through
the valve 10,
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ATTORNEY DOCKET NO. PATENT
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thereby permitting minimally restricted exiting flow from the valve whenever
the ball 53 is in its
fully open position.
[00130] The opening spring bias for the ball valve 10 is provided by
combining two
separate springs 78 and 87 with different properties working in parallel. The
main spring 78 is
stronger at its maximum deflection than the secondary spring 87 at its
respective maximum
deflection, but the main spring is less stiff. Because the travel of the main
spring 78 is relatively
long and a large bias force resisting full ball closure is undesirable at the
closed second ball
position, a low stiffness for the main spring is required. However, at and
near the first ball
position, axial vibrations of the open ball 53 lead to wear in the ball guide
grooves 30 of the ball
cage halves 25, the ball grooves 56, on the cylindrical surfaces of the guide
pins 55 of the ball 5,
and the camming pins 29 of the ball cage.
[00131] In order to aid in suppressing these vibrations while the
ball is in its first position,
the application of additional spring bias force for holding the ball 53
against the ball stop 21 is
necessary. However, application of the downward biasing force of the secondary
spring 87 over
the full range of travel of the ball is undesirable, since full closure of the
ball 53 would then
require an appreciably higher back pressure. For these reasons, provision of a
latch mechanism
84 is necessary for disengaging and reengaging the secondary spring 87 at an
intermediate ball
third position a short distance from the first ball position. The preload and
stiffness of the
secondary spring 87 are selected so that the peak combined spring bias force
from the springs 78
and 87 applied to the ball pusher 70 and hence the ball 53 at the third
position of the ball is less
than the maximum force applied by the main spring 78 alone when the main
spring is at its
maximum deflection with the ball 53 at its second position.
[00132] A tubular ball pusher assembly 70 having a ball pusher seat
73 bears on the
spherical surface of the ball valve 53 and transmits the forces of the opening
spring biases to the
ball. The biasing forces applied by the main spring 78 continuously act on the
ball pusher
assembly 70 through the spring washer 75 and the snap ring 74.
33
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[00133] Biasing forces from the secondary spring 87 react against
the latch sleeve 85 of
the latch assembly 84. The multiple small diameter latch balls 86 engaged in
the radial holes
through the latch sleeve 85 are not completely housed in the radial direction
within those radial
holes, but rather can protrude radially either outwardly or inwardly or both
since their diameters
are greater than the radial thickness of the latch sleeve 85. The body 71 of
the ball pusher
assembly 70 has a close fit to the inner diameter of the latch sleeve 85 of
the latch assembly 84,
while the secondary spring recess 92 of the spring retainer 90 has a close fit
to the outer diameter
of the latch sleeve 85.
[00134] The male annular latch groove 72 of the ball pusher assembly
70 has a radial
depth sufficient to permit the radially inwardly urged balls 86 of the latch
assembly 84 to not
extend radially outwardly of the outer diameter of the latch sleeve 85 when
the holes in the latch
sleeve groove 72 are adjacent the ball pusher latch groove 72. Likewise, the
radial depth of the
female annular groove 93 of the spring retainer 90 is sufficient to allow the
latch balls 86
engaged in the latch sleeve 85 to extend radially inwardly no farther than the
inner diameter of
the latch sleeve 85 when the spring retainer latch groove 93 is adjacent the
holes of the latch
sleeve. When the annular latch groove 72 of the ball pusher body 71 is in
close proximity to the
annular latch groove 93 of the spring retainer 90, the latch balls 86 can be
partially engaged in
both grooves.
[00135] Whenever the latch balls 86 are engaged in the both the
latch sleeve 85 and the
annular latch groove 72 of the ball pusher 70 and held there by the radial
reaction of the balls
against the cylindrical surface of the secondary spring recess 92 of the
spring retainer 90, the
application of axial forces on the ball pusher acting through its lower
inclined face of the latch
groove 72 urges the balls radially outwardly. This situation is shown in
Figures 1, 2, and 3.
[00136] Likewise, whenever the latch balls 86 are engaged in the
both the latch sleeve 85
and the annular latch groove 93 of the spring retainer 90, the balls are held
there by the radial
reaction of the balls against the outer diameter of the ball pusher body 71.
At that time, the
application of axial forces from the secondary spring 87 on the latch sleeve
urges the latch balls
34
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ATTORNEY DOCKET NO. PATENT
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radially inwardly due to reactive forces applied to the balls from the lower
inclined face of the
latch groove 93 of the spring retainer 90. This situation is shown in Figure
5. The radial forces
urging radial movement of the balls 86 result from the interaction of the
balls with the
frustroconical ends of the grooves 72, 93 whenever loadings in the axial
direction of the valves
10, 200, and 300 are applied to the balls.
[00137] Thus the balls 86 shift outwardly when they reach the
annular latch groove 93 of
the spring retainer 90 when the main spring 78 is sufficiently compressed
during the closure of
the ball 53. Likewise, the balls 86 shift inwardly when they reach the annular
latch groove 72 of
the ball pusher body 7 l when the main spring 78 is sufficiently decompressed
during the opening
of the ball 53.
[00138] Figure 4 and the detail view Figure 16 show the balls 86
when they are almost
fully shifted into full engagement with the spring retainer latch groove 93 as
the ball 53 nears its
third position during its closure. When the balls 86 move close enough to the
annular latch
groove 93 in this situation, they will fully shift out of engagement with the
groove 72 of the ball
pusher assembly 70 and into full engagement with the groove 93. The ball
pusher 70 is then
fully decoupled from the latch assembly 84, as shown in Figure 5.
[00139] Further upward movement of the ball pusher 70 as the main
ball 53 moves
upwardly past its third position then causes the balls 86 to be trapped in
their outward position in
groove 93 by contact with the outer cylindrical wall of the ball pusher 70.
When this condition
exists, the ball pusher assembly 70 only transmits downward main ball opening
bias forces from
the main spring 78 to the main ball 53. Neglecting frictional effects, any
biasing forces from the
secondary spring 87 do not act on the main ball 53 for this situation, since
the downward bias
force from the secondary spring 87 bearing on the latch sleeve 85 of the latch
assembly 84 is
fully decoupled from the ball pusher 70 and transmitted only to the spring
retainer 90.
[00140] When the ball pusher assembly 70, biased by only the main spring 78
acting on
the spring washer 75 and snap ring 74, is moving downwardly as the main ball
53 moves from its
second position towards its third position, the spring bias from the secondary
spring 87 urges the
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= RUSS-P023C1PUS
latch balls 86 inwardly so that they will begin to shift into engagement with
the latch groove 72
of the of the ball pusher assembly 70 when that groove comes sufficiently
near. Figures 4 and 16
also illustrate the situation when the balls 86 are in the process of
disengaging from the female
latch groove 93 of the spring retainer 90 and reengaging with the male latch
groove 72 of the ball
pusher. When the balls 86 move close enough to the annular latch groove 72 in
this situation,
they will fully shift out of engagement with the groove 93 of the spring
retainer 90 and into full
engagement with the groove 72. The ball pusher 70 is then fully recoupled to
the latch sleeve 85
and the bias force from the secondary spring 87 again contributes to the
downward urging of the
ball pusher.
[0014]] As a consequence of this unlatching and relatching action of the
secondary spring
87 biased latch assembly 84, between the first and third ball positions the
main ball 53 is strongly
biased towards the ball stop 21 by both the main spring 78 and the secondary
spring 87. This is
the case when downward flow, zero flow, or any level of reverse flow occurs.
However,
whenever the ball 53 is moved upwardly towards its main seat 62 more than a
short distance,
I 5 decoupling of the latch assembly from the ball pusher assembly 70 when
the main ball is just
past its third position reduces the opening bias forces on the ball to only
those provided by the
main spring 78. The resulting higher spring forces biasing the open ball 53
against the ball stop
21 when the main ball is between its first and third positions, compared to
those obtained by
using the main spring 78 alone, greatly aid in minimizing vibratory relative
motion in the axial
direction between the main ball and the ball cage 24.
[00142] During closure of the main ball 53 induced by reverse flow
in the valve 10, the
ball pusher seat 73 continues to seal against the main ball between the first
and third ball
positions. The inner and outer diameters of the ball pusher seat 73 are
selected to ensure that this
is the case. This sealing action blocks off any reverse flow passing through
the clearance gap
between the main ball and the main bore 14 of the valve body 11, thus ensuring
maximization of
the back pressure force acting on the flappers 44 mounted in the ball. This
prevention of
bypassing flow during the initial closing action of the main ball thus aids in
overcoming the extra
36
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resistance to closure of the main ball provided by the secondary spring 87
between the first and
third main ball positions.
[00143] After the main ball moves upwardly past its third position,
the seal between the
ball pusher seat 73 and the main ball is broken. This opens a small additional
flow path for
backflow, so less backflow induced force acting to close the ball 53 is
available. However, as
shown in Figure 15, the spring resistance to closure is relatively reduced
from its value between
the first and third main ball positions for most of the remaining closing
travel of the ball.
[00144] While both the main spring 78 and the secondary spring 87
are active in biasing
the ball 53 towards its open position, a relatively high force is available to
urge the ball 53
against the lower ball stop 21. When the latch assembly 84 is released from
the ball pusher
assembly 70, the resistance to closure drops. However, further upward travel
of the ball towards
its closed position leads to the maximum opening bias force being applied to
the ball when the
ball is fully closed. The relatively high initial force resisting ball
movement away from its open
position is highly desirable to minimize ball vibratory motions while at the
same time keeping
the maximum force required for closure to reasonable levels.
[00145] Additional resistance to vibratory motion of the ball 53 is
provided by fluid
damping. The close fit of the spring washer 75 to both the spacer sleeve 80
and the ball pusher
body 71 results in sufficient flow restriction in those annular gaps to
provide additional
resistance to vibratory motion of the ball pusher assembly 70 and hence the
ball 53. As a
consequence, a further reduction to wear tendencies from the axial motion of
the ball 53 is
provided by the resultant fluid damping.
[00146] During vibration when the displaced ball pusher assembly 70
attempts to return to
its maximum downward position following its fluid damped upward displacement,
the spring
bias provided by the secondary spring 87 will cause the ball pusher body 71
with its attached
snap ring 74 to continuously urge the main ball 53 towards the ball stop 21.
The main spring 78
will also urge the spring washer 75 downwards at this time. However, the
spring washer 75 is
not restrained axially on its upper side, so typically the spring washer will
lag behind the ball
37
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pusher body 71 due to fluid damping. For the spring washer 75 the amount of
fluid damping in
this return motion case is somewhat reduced, as the spring washer no longer
abuts the snap ring
74 to restrict flow between the spring washer and the ball pusher. Ensuring
the rapid return of
the main ball 53 to the ball stop 21 under urging of the secondary spring 87
acting through the
ball pusher seat 73 results from this arrangement, and this further aids in
minimizing vibratory
motion of the main ball
[00147] Fluid induced forces also act on the ball 53 and the
flappers 44. The flapper and
seat assembly 34 is fixedly mounted in the ball 53 with 0-ring 50 sealing
between the ball bore
57 and the flapper seat ring 35. The springs 46 urge the flappers 44 to their
normally closed
position, but are easily overcome by minor flows from the inlet end of the
valve 10. However,
when there are no or reverse flow conditions for the valve, the flappers 44
are firmly biased
against their seating surface 36 by their flapper springs 46. When the
flappers 44 are seated
against the seating surface 36 of the flapper seat ring 35, the combination of
the ball 53 and the
flappers 44 functions like a piston for reverse flow.
[00148] Of necessity, operating clearances have to exist between adjacent
flappers when
multiple flappers 44 used. The use of multiple flappers to close the flow
passage for the valve 10
permits a reduction in the outer diameter of main ball 53 and, hence, the size
of body 11 when
compared to the case for use of a single flapper for closure of the flow path
through the main ball
53. For a valve 10 newly in service, the resultant clearance gaps result in
some small flow past
the closed flappers when reverse flow conditions exist, and the gaps can grow
over time in
abrasive flow conditions. However, the amount of reverse flow allowed by the
flappers 44 in
any case is minor and flapper wear will require only a very small increase in
reverse flow from
that required for the unworn full flapper closure condition to produce
sufficient force to bias the
ball 53 to full closure against its main seat 62.
[00149] Whenever the main ball 53 moves in the upward direction a short
distance beyond
its third position, the ball pusher seat 73 loses its seal with the spherical
face of the ball. This
opens an additional extraneous flow path first through the gap between the
main ball and the
38
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main bore 14 of the valve bodyl 1 and then between the ball pusher seat and
the main ball.
Restricting the clearance between the main ball and the body minimizes the
resulting extraneous
flow so that only minor increases in back flow pressure are required to
overcome the resulting
loss of force urging the main ball to close at its second position.
[00150] Figure 15 illustrates the variation in the opening spring bias
forces on the main
ball 53 as a function of the displacement of the ball from its fully open
first position resting
against the ball stop 21. Between the first and third ball positions, a
relatively high force
produced by reverse flow in the valve 10 is required to initiate valve
movement sufficiently away
from the ball stop 21 to decouple the biasing forces of the secondary spring
87 from biasing the
ball toward its open position. However, once the bias of the secondary spring
87 is removed by
displacing the ball towards the second closed position past its third
position, the fluid induced
closure forces needed to produce full ball closure at the second ball position
against the main seat
62 are relatively reduced for much of the travel of the ball between its third
and second positions.
When the main ball 53 is in its second position fully closed against the main
seat 62, the flappers
44 are pressure balanced and play no role in resisting back pressure.
[00151] When normal flow from the inlet end of the valve 10
initiates with the valve in its
closed second position, the spring bias force from the main spring 78 and any
flow induced
pressure on the main ball 53 from flow in the normal direction of the valve 10
urge the ball
towards its normally open first position against the ball stop 21. When the
opening ball passes
its third position, the bias forces from the secondary spring 87 again
contribute to the forces
urging the ball towards its first position. The opening bias forces on the
main ball are always
active unless the flow induced loads on the ball cause it to move more rapidly
toward its ball stop
21 than the ball pusher assembly 70 can follow. Opening bias forces on the
ball pusher assembly
are always active.
[00152] The choke and kill manifold check valve 200 has deliberately
enlarged clearances
between adjacent faces of its individual flappers 244. The resulting increased
flow leakage area
in the choke and kill flapper assembly 234 causes the valve 200 to act as a
hydraulic fuse. While
39
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this behavior occurs to some extent for each of the valve types 10, 200 and
300, it is deliberately
enhanced for this application.
[00153] Thus, the valve 200 will close only when the backflow
through the flappers 244
exceeds an analytically determinable desired level. As a consequence of this
increased flapper
leakage flow area, the choke and kill manifold check valve will not close
during the relatively
low flows associated with normal wireline or coiled tubing operations.
However, if the well to
which the valve 200 is connected loses stability during such operations so
that excessive
outflows tend to occur through the valve, the valve 200 will shut to isolate
the well.
[00154] The conventional approach to wireline or coiled tubing
operations in a well is to
remove the internal components from a conventional poppet type choke and kill
manifold check
valve. This action removes necessary blowout protection during operations
which can
inadvertently start a well to flow uncontrollably. Thus, use of the choke and
kill manifold check
valve 200 provides necessary enhanced safety to wireline and coiled tubing
operations in live
wells.
[00155] The float valve version of the check valve is functionally
identical to the inside
blowout preventer version 10 of the valve, with the exception of the vibration
damping provided
by the elastomeric upper 310 and lower 314 damper assemblies. These dampers
act to reduce
vibratory movement of the valve internals and the resultant wear.
[00156] The cross-sections of the upper 312 and lower 316 damper
elastomeric elements
differ, and their elastomer compositions may also be different. Consequently,
their axial
stiffnesses differ and their vibrational energy absorptions differ.
Additionally, the axial
stiffnesses of these elastomeric elements also change as a function of their
amounts of axial
compression, due to geometry changes during compression. The consequence of
these effects is
that the elastomeric elements 312 and 316 have different frequency responses
and hence damp
different portions of the vibration amplitude spectrum to which the valve 300
is exposed. The
use of elastomeric dampers having different stiffnesses and energy absorption
characteristics
permits improving motion damping for the valve elements suspended between the
two dampers.
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Since both dampers 310 and 314 are installed in compression, both are
generally active at the
same time.
[00157] When the float valve 300 is closed, sufficient upwardly
axial pressure load acting
on the closed valve internal components will cause the upper elastomeric
damper element 312 to
be so strongly compressed that the upper damper retainer ring 311 and the
upper damper
abutment ring 313 will come in contact to support the retained axial pressure
load. This
abutment of the rings 311 and 313 prevents the upper elastomeric element 312
from
overstressing and extruding while the axial pressure load is transferred into
the body 301 of the
float valve 300.
[00158] ADVANTAGES OF THE INVENTION
[00159] The embodiments of the self-piloted check valve described
herein offer numerous
benefits compared to conventional check valves. Because of its full opening
construction, the
valve has very low pressure losses, even with unusually high flow rates. The
full opening
construction also permits the unimpeded passage of objects through the bore of
the valve when
normal flow is occurring. This feature is useful in some service conditions.
The low flow
restriction is a result of minimal flow turbulence due to the straight flow
path through the valve,
which leads to a consequent reduced tendency for wear from abrasive flows.
[00160] While the piloting flappers are always susceptible to
abrasive and other types of
fluid erosion, they do not have to fully seal when closed to pilot the valve.
With the ball closed
against its seat, the flappers are pressure balanced and inactive in
preventing reverse flow. Only
engagement of the ball and its seat prevent reverse flow. As the flappers
wear, the reverse flow
necessary to obtain ball valve closure increases, but the valve still
functions.
[00161] The primary reason for the long life of the improved self-
piloted check valve is
the protection of both the spherical sealing surface of the ball and its seat
from all flow except
the low flows passing the ball and its seat during bidirectional shifting of
the valve between its
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open and closed positions. These low bypass flows are sufficiently slow to not
present an
erosion problem to the sealing surfaces of the ball and seat.
[00162] When the improved self piloted check valve is used as either
an inside blowout
preventer or a float valve in a drillstring or as a drilling choke and kill
manifold check valve, it is
actually desirable that the flappers not be pressure tight. The inherent
leakiness of the flapper
valve utilized permits the transmission of pressure downstream of the valve
through the normally
closed flappers and normally ball valve so that it can be measured by gauging
means if all flow is
temporarily prevented. This capability of pressure measurement through the
improved self
piloted check valve is critical for safety in drilling applications.
[00163] Likewise, permitting some limited reverse flow through the open
ball and closed
but deliberately leaky valve flappers shown in Figure 12 for the choke and
kill manifold check
valve is essential to allowing necessary fluid displacements from wireline or
coiled tubing
operations through the valve while still having reliable closure for
undesirably large reverse
flows.
[00164] Provision of a two stage ball opening bias, such as that indicated
in Figure 15, is
important for avoiding excessive ball motion whenever the valve is strongly
vibrated, such as is
the case for drilling float valves. If the contacts between the ball and its
ball cage are subject to
excessive vibration, such as can occur in near bit drilling applications of
the float valve version
of the valve, then the provision of the higher opening bias on the ball due to
use of the secondary
spring can substantially limit wear on the ball and its ball cage.
[00165] Having to overcome a higher initial ball opening spring bias
is also desirable to
ensure the development of sufficient force from reverse flow to ensure
complete displacement of
the ball from its open position to its sealing position abutting its seat.
This is particularly
advantageous when the valve is to be used in film forming fluids, such as
crude oils with high
paraffin contents. Also, isolating the exterior of the open ball from film
forming fluids due to
sealing of the ball pusher seat with the ball when the valve is open further
minimizes the
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tendencies for the valve to stick partially open or closed due to film
buildup. These and other
advantages will be apparent to those skilled in the art.
[00166] The space between the main seat of the valve and the spring
retainer is essentially
isolated by the 0-ring of the spring retainer. This permits the spring washer
to provide damping
for upward movement of the ball pusher and ball. As a result, component wear
is reduced by this
feature. Engaging the spring washer on both sides by snap rings can permit
bidirectional
damping. Bidirectional damping of ball motion is important to reduce wear in
high vibration
situations such as those encountered by float valves.
[00167] Various changes can be made to the construction of the self
piloted check valve
described above without departing from the spirit of the invention. Different
materials can be
used for reasons of corrosion or temperature resistance. Different spring
types can also be
substituted for the coil springs, such as the use of a wave spring instead of
the coil spring used
for the secondary bias spring. A metal-to-metal seat can be substituted for
the elastomeric ball
seat seal. Minor changes can render the valve fire safe. These and other
changes do not depart
from the spirit of the invention.
43
