Multiple orifice valve with low volume flow control

A multiple orifice flow control valve has a set of similar disks mounted in the body of the valve. A downstream disk is mounted in a fixed position in the valve body and an upstream disk is rotatable in the valve body in concentric face-to-face engagement with the downstream disk. There are two holes in the downstream disk and two holes in the upstream disk for control of the flow of fluids through the valve. The two holes in each disk are at non-adjacent apexes of a regular pentagon. By rotating the upstream disk 72.degree. in one direction the valve changes from closed to one-half open. By rotating the upstream disk through the same angle in the opposite direction, the valve changes from closed to fully open.

FIELD OF THE INVENTION 
The present invention relates to a multiple orifice valve comprising a set 
of disks used for controlling the flow of fluid with improved calibration 
at low flow rate. 
BACKGROUND OF THE INVENTION 
Multiple orifice valves are useful for control of flow of fluids such as 
fluids produced from oil and gas wells and the like. Orifice valves, for 
example, are used on a wellhead for control of the rate of flow of well 
production fluids from a well. Such valves are often referred to as 
chokes. Exemplary multiple orifice valves are described in U.S. Pat. Nos. 
3,207,181 and 3,331,396 by R. S. Willis, both of which are incorporated by 
this reference. 
The rate of flow of fluid through an orifice valve is in part determined by 
the number and size of holes in both a stationary disk and a rotatable 
disk mounted across a fluid path through a valve body. In an exemplary 
valve, there are two diametrically opposite holes in each of the upstream 
and downstream disks. The holes in the rotatable upstream disk are 
positioned in various degrees of alignment with the holes in the 
stationary downstream disk by angular movement of the rotatable disk. The 
rotatable disk can be moved from a fully closed position out of alignment 
with the holes in the downstream disk for blocking flow through the valve 
to a fully opened position with the holes aligned for providing maximum 
flow through the valve. 
Such a valve or choke is used for controlling the rate of production from 
an oil well by rotating the upstream disk to a position at an angle of up 
to 90.degree. from the closed position. At some position within this range 
20%, for example, of the cross-sectional area of each of the holes in the 
upstream disk overlaps 20% of the area of the holes in the downstream. The 
balance of each of the holes is occulted by the other disk. When in such a 
position the flow through the valve is 20% of the flow when the valve is 
fully open. This percentage and others can be indicated by indicia on the 
valve stem so that the valve can be set to a desired flow rate. 
It is desirable to reliably adjust such a valve to reproducible valve 
openings. This is difficult at low flow rates, however, since the 
percentage change in flow is rather large for a small angular displacement 
of the disk. Reproducible adjustment can therefore be difficult. 
Setting of an adjustable choke on an oil or gas well is quite often near 
the low end of the range of flow through the valve. This occurs because of 
the conservative design employed in the oil patch. A larger valve than 
might appear necessary is commonly used at the wellhead so that the valve 
can be left in place for a long time during the productive life of the 
well. Such a valve can be set with a small valve opening to obtain a 
desired production flow during early life of a well when production 
pressures are high. Thereafter, as production pressure gradually 
decreases, the valve can be gradually opened for maintaining a desired 
flow. Such a valve may be used in the low ranges of flow control, that is 
less than half open, for periods of months or years. 
Multiple orifice valves have a notoriously tight calibration range at low 
flow rates, particularly up to about 20% of maximum flow, and it is 
desirable to extend the calibration range that can be used reliably and 
reroducibly. 
SUMMARY OF THE INVENTION 
There is, therefore, provided in practice of this invention a multiple 
orifice flow control valve comprising a valve body having a downstream 
disk fixed in place in the valve body, an upstream disk is concentric with 
and in face-to-face engagement with the downstream disk. Each disk has a 
pair of fluid flow holes therethrough wherein each of the holes is located 
at an apex of a regular polygon having at least five sides concentric with 
the disks. The pair of holes in each such disk is separated by one 
imperforate apex of the polygon. By rotating the upstream disk through a 
selected angle in one direction, the valve moves from closed to fully 
open. When rotated in the opposite direction through the selected angle, 
the valve moves from closed to one-half open, thereby doubling the ability 
to control flow with precision between closed and one-half open.

DETAILED DESCRIPTION 
The multiple orifice valve illustrated semi-schematically comprises a valve 
body 11 divided by a set of disks 12 and 13 into an upstream chamber 14 
and a downstream chamber 16. There is an inlet opening 17 into the 
upstream chamber for entrance of fluids and an outlet opening 18 from the 
downstream chamber for fluid egress. 
Although not shown in the drawings, suitable means for connecting the valve 
body to inlet and outlet conduits are provided. These can comprises 
flanges, threads, or the like at the inlet and outlet of the valve body. 
Minimal details of the valve are included herein since they are 
conventional and not needed for an understanding of the invention. 
Additional details of multiple orifice valves can be found in the 
above-mentioned U.S. Patents. 
The set of disks comprises an upstream disk 12 and a downstream disk 13 
which are preferably composed of erosion resistant materials, such as 
aluminum oxide, tungsten carbide, or the like. Two holes (one of which, 
19, is illustrated in the upstream disk in FIG. 1) are provided through 
each disk at the same radial distance from the center of the disk. When 
the holes through the disks do not overlap to any degree, that is, when 
the holes are completely out of alignment with each other, fluid flow from 
the upstream chamber to the downstream chamber is blocked. When the holes 
through the disks are at least partly in alignment with each other, that 
is, when portions of the holes are superimposed, fluid introduced into the 
upstream chamber through the inlet 17 can flow through holes in the disks 
into the downstream chamber and exit the valve at the outlet 18. The 
amount of fluid flow through the valve is controlled by the degree of 
alignment of the holes. 
In an exemplary embodiment, the circular downstream disk 13 is mounted in a 
fixed position in the valve body across the fluid flow path between the 
upstream and downstream chambers. The downstream disk is mounted in an 
annular ring 21 which surrounds the circumference of the disk and is 
affixed to the disk by epoxy resin or like adhesive, brazing, and/or by 
other securing means such as pins. The ring in turn is fixed by bolts, 
pins, or the like to the valve body. 
The circular upstream disk 12 is rotatably mounted in the valve body 
concentric with and in face-to-face engagement with the downstream disk. 
In the exemplary embodiment each of the disks has about equal radial and 
axial dimensions, although disks of differing dimensions can be used, if 
desired. 
The upstream disk is mounted in an annular ring 22 which surrounds the 
circumference of the disk and is affixed thereto by epoxy resin or similar 
adhesive, brazing, and/or by other securing means such as pins. 
The upstream disk can be rotated relative to the downstream disk for 
superimposing holes in the upstream disk in various degrees of overlap or 
alignment with holes in the downstream disk. The disks are flat and the 
facing surfaces are smooth to provide ease of movement of the disks 
relative to each other and a seal when the valve is closed. In an 
exemplary embodiment the facing surface of each disk has an eight 
microinch RMS finish. 
A valve stem 22 passes through an opening at one end of the valve body for 
adjusting the valve. The valve stem is sealed to prevent passage of fluids 
between the stem and the valve body by O-rings or the like (not shown). A 
forked turning member 23 is provided on the inner end of the valve stem in 
the upstream chamber. The two arms or tines of the forked memer 23 engage 
slots in the upstream face of the annular ring 22 holding the upstream 
disk. When the valve stem is rotated, the tines engaged in the slots cause 
rotation of the ring which in turn provides rotation of the upstream disk. 
Graduated markings (not shown) can be provided on the valve body and valve 
stem to indicate the position of the valve as the disk is rotated between 
its open and closed positions. 
FIG. 2 is a face view of the upstream disk 12 atop the downstream disk 
which is hidden except where seen through two circular holes 19 through 
the upstream disk. Two holes 24 are also provided through the downstream 
disk. In this view the upstream disk is in a position where the holes 19 
in the upstream disk are not in alignment with the holes 24 in the 
downstream disk. This represents the closed position for the valve. 
The two holes in each of the disks are located at non-adjacent apexes of a 
regular pentagon 25 indicated by a phantom line in FIG. 2. That is, the 
holes are all at the same radial distance from the center of the disk and 
the two holes in each disk are 144.degree. apart. When the valve is in its 
closed position, the four holes through the two disks are at four of the 
five apexes of the pentagon 25. The fifth apex of the pentagon has no 
holes in either disk. 
When the upstream disk is rotated in one direction relative to the 
downstream disk, such as clockwise as illustrated in the perspective views 
of FIGS. 4 and 5, the two holes 19 in the upstream disk overlap increasing 
areas of the two holes 24 in te downstream disk as illustrated in FIG. 4. 
Upon full rotation through 72.degree. in that direction the valve reaches 
a fully open position as illustrated in FIG. 5 with the two holes in the 
upstream disk in alignment with the two holes in the downstream disk. This 
permits maximum flow of fluid through the valve. 
When the upstream disk is rotated in the opposite direction, for example, 
counterclockwise as illustrated in FIGS. 6 and 7, the valve moves from the 
closed position illustrated in FIGS. 2 and 3 towards a one-half position 
as illustrated in FIG. 7. In this direction of rotation one of the holes 
in the upper disk progressively overlaps larger areas of one of the holes 
in the downstream disk as illustrated in FIG. 6. The other hole in the 
upstream disk lies opposite an imperforate area on the downstream disk 
corresponding to the fifth, unoccupied apex of the pentagon. Similarly, 
the other hole in the downstream disk lies adjacent the imperforate area 
on the upstream disk corresponding to the fifth, unoccupied apex of the 
pentagon. When the upstream disk has been rotated 72.degree. from the 
closed position, it is one-half open. 
When the valve is rotated towards this half open position, a given angular 
displacement of the upstream disk increases the overlap areas of the 
holes, and hence the flow rate through the valve, only one-half as much as 
a corresponding angular rotation in the opposite direction where both 
holes in the upstream disk overlap both holes in the downstream disk. 
Since a given angular displacement opens the valve only half as much when 
rotated in this direction, the ability to control the flow through the 
valve is doubled. This is particularly important when the desired valve 
setting is up to about 20% of the full flow. Close control of flow at a 
valve opening of less than 20% has previously been quite difficult. With a 
set of disks as described herein, flow control at valve openings down to 
10% or less is readily obtained. 
It might be noted that with the circular holes described and illustrated 
herein, the total flow through the valve at the fully open position is 
somewhat less than obtained through a multiple orifice valve where the 
holes are diametrically opposite. The reason lies in the somewhat smaller 
area of the holes in this embodiment to assure that adequate area remains 
between adjacent holes to assure good closure by the valve. Total flow 
through the valve can be enhanced if desired by employing larger holes 
having shapes other than round. 
Stated in another way, the pair of holes in each disk can be considered to 
lie in a pair of equiangular sectors of the disk with one intervening 
imperforate sector between the sectors containing the holes. When the 
sectors containing holes are aligned with imperforate sectors, the valve 
is closed. When sectors containing holes are aligned, the valve is open 
either half way or completely depending on the direction of rotation. 
The preferred embodiment of disks for a multiple orifice valve has four 
holes in two disks with the two holes in each disk being located at 
non-adjacent apexes of a regular polygon having a minimum of five sides. 
It should be apparent that variations in this hole location cna be used 
for providing one range of valve opening by rotation in one direction and 
another range of valve opening by rotation in the opposite direction. For 
example, holes could be provided at two alternate apexes of a regular 
hexagon. Alternatively, holes could be spaced similarly on the two disks 
where the included angle between radii to the two holes is different from 
144.degree.. In any such embodiment the areas of the holes are less than 
the areas in the preferred embodiment so as to leave an adequate seal area 
between holes, hence, the maximum flow through the valve is reduced. 
Although but one embodiment has been described and illustrated herein, many 
modifications and variations will be apparent to one skilled in the art. 
For example, the holes through the disks are illustrated as round. Other 
hole shapes for modifying the calibration of flow versus disk rotation or 
for increasing maximum flow can be used. It is therefore to be understood 
that within the scope of the appended claims, the invention may be 
practiced otherwise than as specifically described.