BACKGROUND
TECHNICAL FIELD
Embodiments of the subject matter disclosed herein generally relate to actuated valves
used in reciprocating compressors for oil and gas industry, and, more particularly, to
mechanisms and techniques related to valves in which valve closing members are attached
to actuated counter-seats.
DISCUSSION OF THE BACKGROUND
Compressors are mechanical devices used to increase the pressure of a gas and can be
found in engines, turbines, power generation, cryogenic applications, oil and gas
processing, etc. Due to their widespread use, various mechanisms and techniques related
to compressors are often subject to research for improving the compressor efficiency and
solving problems related to specific situations. One particularity that has to be considered
for compressors used in oil and gas industry is that the compressed fluid is frequently
corrosive and inflammable. American Petroleum Institute (API), the organization setting
the recognized industry standard for equipment used in oil and gas industry has issued a
document, API618, listing a complete set of minimum requirements for reciprocating
compressors.
The compressors may be classified as positive displacement compressors (e.g.,
reciprocating, screw, or vane compressors) or dynamic compressors (e.g., centrifugal or
axial compressors). For positive displacement compressors, the compression is achieved
by trapping the gas and then reducing volume in which the gas is trapped. For dynamic
compressors, the gas is compressed by transferring kinetic energy, typically from a rotating
element such as an impellor, to the gas being compressed by the compressor.
Figure 1 is an illustration of a conventional dual chamber reciprocal compressor 10 useable
in oil and gas industry. Compression occurs in a cylinder 20. A fluid to be compressed
(e.g., natural gas) is input into the cylinder 20 via an inlet 30, and, after being compressed,
it is output via an outlet 40. The compression is a cyclical process in which the gas is
compressed by movement of the piston 50 along the cylinder 20, between a head end 26
and a crank end 28 of the cylinder 20. In fact, the piston 50 divides the cylinder 20 in two
2
compression chambers 22 and 24 operating in different phases of the compression cycle,
the volume of compression chamber 22 being at its lowest value when the volume of the
compression chamber 24 is at its highest value and vice-versa.
Suction valves 32 and 34 open to allow the fluid that is going to be compressed (i.e.,
having a first pressure PI) from the inlet 30 and through the suctions valves 32 and 34 into
the compression chambers 22 and 24, respectively. Discharge valves 42 and 44 open to
allow the fluid that has been compressed (i.e., having a second pressure P2) to be output
from the compression chambers 22 and 24, respectively, via the outlet 40. The piston 50
moves due to energy transmitted from a crankshaft 60 via a crosshead 70 and a piston rod
80.
Conventionally, the suction and the compression valves used in a reciprocating compressor
are automatic valves that are switched between close and open due to a differential
pressure across the valve. Figures 2A and 2B illustrate the operation of an automatic valve
100 having a seat 110 and a counter-seat 120. A distance d between the seat 110 and the
counter-seat 120 is constant throughout the compression cycle (for example, a spacer 115
may be located there-between). Figure 2A illustrates the valve 100 in an open state and
Figure 2B illustrates the valve 100 in a close state.
In the open state illustrated in Figure 2A, the valve closing member 130 is pushed down
into the counter-seat 120 allowing the fluid to flow through a inlet port 140 and outlet ports
150. The shape of the valve closing member130 may be a disc, a poppet, multi-poppet or
rings, which difference in shape gives the name of the valve: disc valve, poppet valve,
multi-poppet valve or ring valve. Figures 2A and 2B represent a generic configuration
independent of the details related to the actual shape of the valve closing member 130.
Figure 3 illustrates components of a ring valve which operate as in Figures 2A and 2B: the
seat 110 and the counter-seat 120 having circular openings of the ports 140 and 150 on
their surfaces, springs 160 on the counter-seat 120 and rings 131 (which are the valve
closing member).
In Figure 2A, a spring 160 is located between the valve closing member 130 and the
counter-seat 120. Depending on its state of deformation, the spring 160 actively
participates in establishing a valve opening point, the elastic deformation force
superimposing a pressure along the flow path equal to the force divided by the area of the
3
valve closing member 130. In the open state, the first pressure PI before the inlet port 140
is larger than the pressure P2 at the destination of the fluid after the outlet ports 150. If the
spring 160 is deformed when the valve closing member 130 is pushed down into the
counter-seat 120 (as shown in Figure 2A), the difference (PI- P2) between the pressures
before and after the valve has to be larger than the pressure due to the spring 160 (i.e., a
ratio of the elastic deformation force divided by the area of the valve closing member).
In the close state illustrated in Figure 2B, the valve closing member 130 prevents the fluid
flowing from the inlet port 140 towards the outlet ports 150. The spring 160 is often
configured to favor a faster closing of the valve, and, therefore, it is known as a "return"
spring closing the valve 100 even if the pressures at the source PI and the destination P2 are
equal (PI= P2).
As described above, the valves in a reciprocating compressor may be switched between the
open state and the close state due to the pressure difference between the pressure PI at the
source of the fluid and the pressure P2 at the destination of the fluid. The springs are used
to accelerate the switching between the open and close states, while the pressure difference
across the valve (PI- P2) may change dynamically. Alternatively, the valve closing
member may be actuated by an electromagnetic or hydraulic actuator applying a force to
move the valve closing member.
The spring is a part of the valves that frequently fails, affecting reliability of the valve, and,
thus, of the whole reciprocating compressor. Additionally, in time, fluttering may occur,
that is asymmetries due to the springs may disrupt the motion of the valve closing member
allowing leakage. When actuators are used, the force due to the spring may have to be
overcome by the actuator force in some situations occurring during the valve operation.
Further, one inefficiency to the reciprocating compressor is related to the clearance
volume, that is, a volume from which the compressed fluid cannot be evacuated. Part of
the clearance volume is due to volume related to the valves. A design objective is to make
this clearance volume as small as possible.
Accordingly, it would be desirable to provide valves without springs that avoid the aforedescribed
problems and drawbacks.
SUMMARY
Embodiments of the inventive concept set forth in this application have one or more of the
4
following advantages: valves useable in reciprocation compressors for oil and gas industry
that do not include springs that frequently fail, are thinner and have an increased flow area.
According to one exemplary embodiment, a valve assembly in a reciprocating compressor
used in oil and gas industry includes an actuator configured to provide a valve actuating
motion and a valve. The valve has: (1) a valve seat configured to allow a fluid to flow
through the valve seat, via an inlet port thereof, (2) a counter-seat attached to the actuator
and configured to allow the fluid to flow through the counter-seat, via an outlet port
thereof, and (3) a valve closing member attached to the counter-seat, located and
configured to cover the inlet port when the counter-seat is in a closed position. The
counter-seat receiving the linear motion from the actuator, moves between the closed
position and an opened position corresponding to the inlet port being open thereby
allowing the fluid to flow on a flow path including the inlet port and the outlet port.
According to another exemplary embodiment, a reciprocating compressor includes an
actuator configured to provide a valve actuating motion, and a valve. The valve has: (1) a
valve seat configured to allow a fluid to flow through the valve seat, via a inlet port
thereof, (2) a counter-seat attached to the actuator and configured to allow the fluid to flow
through the counter-seat, via a outlet port thereof, and (3) a valve closing member attached
to the counter-seat, located and configured to cover the inlet port when the counter-seat is
in a closed position. The counter-seat moves closer or father to the seat due to the linear
motion received from the actuator during each cycle of the reciprocating compressor,
between the closed position and an opened position in which the inlet port is open allowing
the fluid to flow on a path including the inlet port and the outlet port.
According to another exemplary embodiment, a method of retrofitting a compressor
initially having a valve with a spring between a valve closing member and a counter-seat
of the valve, the valve initially closing due to a differential pressure, to have the valve
actuated and the valve closing member attached to the counter-seat of the valve is
provided. The method includes (1) fixedly attaching the valve closing member to the
counter-seat of the valve, on a surface of the counter-seat towards a seat of the valve, and
(2) connecting an actuator to the counter-seat, to enable the counter-seat to receive an
actuating motion to move between a closed position in which the valve closing member
covers an inlet port through a seat of the valve, and an opened position in which the valve
5
closing member does not cover the inlet port.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated III and constitute a part of the
specification, illustrate one or more embodiments and, together with the description,
explain these embodiments. In the drawings:
Figure I is a schematic diagram of a conventional dual chamber reciprocal compressor;
Figures 2A and 2B are schematic diagrams illustrating operation of an automatic valve;
Figure 3 is an illustration of components of a conventional ring valve;
Figures 4A and 4B are schematic diagrams illustrating operation of a valve according to an
exemplary embodiment;
Figure 5 illustrates a reciprocating compressor according to an exemplary embodiment;
and
Figure 6 is a flow chart illustrating a method for retrofitting a compressor to have a valve
with valve closing member attached to the counter-seat according to an exemplary
embodiment.
DETAILED DESCRIPTION
The following description of the exemplary embodiments refers to the accompanying
drawings. The same reference numbers in different drawings identify the same or similar
elements. The following detailed description does not limit the invention. Instead, the scope
of the invention is defined by the appended claims. The following embodiments are
discussed, for simplicity, with regard to the terminology and structure of reciprocating
compressor used in oil and gas industry. However, the embodiments to be discussed next are
not limited to these systems, but may be applied to other systems.
Reference throughout the specification to "one embodiment" or "an embodiment" means that
a particular feature, structure, or characteristic described in connection with an embodiment is
included in at least one embodiment of the subject matter disclosed. Thus, the appearance of
the phrases "in one embodiment" or "in an embodiment" in various places throughout the
specification is not necessarily referring to the same embodiment. Further, the particular
features, structures or characteristics may be combined in any suitable manner in one or more
embodiments.
In order to overcome the problems caused by the springs in the valves used in reciprocating
6
compressor for oil and gas industry, in some embodiments the valve closing member is
attached to the counter-seat to be moved together by an actuator thereby opening and closing
the valve. Removing the springs lowers the number of parts of the valve and removes one of
the parts most prone to fail or to induce failure of the other parts (e.g., fluttering of the ring in
a ring valve).
Figures 4A and 4B illustrate the operation of an automatic valve 200 according to an
exemplary embodiment. The automatic valve 200 has a seat 210 and a counter-seat 220
moving jointly with a stem 225. A valve closing member 230 is attached to the counterseat
220. Figure 4A illustrates the valve 200 in an open state and Figure 4B illustrates the
valve 200 in a close state.
In the open state illustrated in Figure 4A, the valve closing member 230, which is attached
to the counter-seat 220, is positioned away from the seat 210 allowing the fluid to flow via
(l) an inlet port 240 through the seat 210, (2) a space between the seat 210 and the counterseat
220, and (3) outlet ports 250 through the counter-seat 220. The shape of the valve
closing member 230 may be a disc, a poppet, multi-poppet or rings, which difference in
shape gives the name of the of valve: disc valve, poppet valve, multi-poppet valve or ring
valve. Figures 4A and 4B represent a generic configuration independent of the details
related to the actual shape of the valve closing member 230.
The inlet port 240 and the outlet port(s) 250 may pass through the seat 210 and the
counter-seat 220, respectively, along substantially parallel directions. However, this
parallel orientation is not a requirement.
The valve seat and the counter-seat may be made of metallic material (e.g., stainless steel
and alloy steel). The counter seat may also be made of composite material which is lighter
than the metallic material. The valve closing member may be made of a non-metallic
material such as polyether ether ketone (PEEK) or stainless steel. In one embodiment, the
valve closing member and the counter-seat may be formed as a single piece, for example
made of stainless steel. In another embodiment, the valve closing member may formed
separately from (and from a different material than) the counter-seat and attached to the
counter-seat.
In one embodiment, as illustrated in Figures 4A and 4B, the counter-seat may have a
groove inside which the valve closing member is placed, a height of the groove being
7
smaller than a height of the valve closing member. In another embodiment, the valve
closing member may be glued, attached with screws or welded to the counter-seat
(depending also ofthe material used to manufacture the valve closing member).
One of the advantages of the actuated valve with the valve closing member attached to the
counter-seat is that an enlarged flow area may be achieved while a smaller distance is
created between the seat and the counter-seat to open the valve. Thus, the clearance
volume due to the valve may be reduced.
In the close state illustrated in Figure 4B, the valve closing member230 with the counter-seat
220 has been moved towards the seat 210 for a distance h' (marked on Figure 4A) so the
valve closing member covers an opening of the inlet port 240 through the seat 210, thereby
~ preventing the fluid from flowing through the valve. Note that the distance h' may be smaller
than a maximum distance h between the seat 210 and the counter-seat 220 when the valve is
open, because the valve closing member 230 may protrude from the surface of the counterseat
220 towards the seat 210. In one embodiment, the valve closing member 230 and the
surface of the seat 210 towards the counter-seat 220 may be machined such as to fit together
so that h '=0.
During a compression cycle, the pressure difference between the source of the fluid (PI) and
the destination of the fluid CP2) may vary. The valve being an actuated valve, the actuator
may be controlled to change the timing of the valve opening or closing (making it earlier or
later than when automated valves are used) in order to increase the compressor's efficiency.
Since the valve closing member 230 is attached to the counter-seat 220, no ring fluttering (i.e.,
deformations) occurs. This shape stability, further allows designing the profile of the valve
closing member 230 or the seat 220, particularly around the opening of the inlet port 240
towards the counter-seat 220 such that to lower the flow resistance. The flow resistance to
fluid flow passage is given (in a first approximation) by a product of the viscosity of the fluid
and the length of the path. The comers prolong the path and thus increase the resistance.
Shorter path may be achieved by designing the valve closing member 230 and/or the opening
of the inlet port 240 towards the counter-seat 220 to have smooth curved shapes instead ofthe
comers thereby lowering the flow resistance.
Figure 5 illustrates a reciprocating compressor 300 having one or more valves similar to
the valves illustrated in Figures 4A and 4B. The compressor 300 is a dual chamber
8
reciprocating compressor. However, valves according to embodiments may be used also in
single chamber reciprocating compressors. The compression occurs in a cylinder 320. A
fluid to be compressed (e.g., natural gas) is input into the cylinder 320 via an inlet 330,
and, after the compression, is output via an outlet 340. The compression occurs due to the
back-and-forth movement of the piston 350 along the cylinder 320, between a head end
326 and a crank end 328. The piston 350 divides the cylinder 320 in two compression
chambers 322 and 324 operating in different phases of the compression cycle, the volume
of compression chamber 322 being at its lowest value when the volume of the compression
chamber 324 is at its highest value and vice-versa.
Suction valves 332 and 334 open to allow the fluid that is going to be compressed (Le., having
a first pressure PI) from the inlet 330 into the compression chambers 322 and 324,
respectively. Discharge valves 342 and 344 open to allow the fluid that has been compressed
(i.e., having a second pressure 1'2) to be output from the compression chambers 322 and 324,
respectively, via the outlet 340. The piston 350 moves due to energy received for example
from a crankshaft (not shown) via a crosshead (not shown) and a piston rod 380.
At least one of the valves 332, 334, 342 and 344 is a valve with valve closing member
attached to the counter-seat as illustrated in Figures 4A and 4B. In Figure 5, valve 332, which
is a suction valve, is illustrated to be an actuated valve with the valve closing member
attached to the counter-seat. However, actuated valves with valve closing member attached to
the counter-seat may be used as discharge valves (e.g., 342, 344) as well. In fact, all the
valves 332, 334, 342 and 344 may be actuated valves with valve closing member attached to
the counter-seat.
The counter-seat 333 of the valve 332 is attached to a stem 335, which moves (in a vertical
direction in Figure 5) due to an actuator 337. Preferably, the actuator 337 is located outside
the fluid path to avoid the danger ofexplosions cause by sparks in the inflammable fluid.
The valve closing member may include one or more disc shaped parts or one or more ring
shaped parts. The opening shapes of the ports correspond to the type of valve. For example,
in a ring valve, the inlet port comprises a plurality of first concentric ports having a first set of
diameters, the outlet port comprises a plurality of concentric outlet ports having a second set
of diameters, any diameter of the first set is different from any diameter of the second set, and
the valve closing member comprises a plurality of rings, that covers all the first concentric
9
ports, when the valve is closed.
Valves with springs currently used in reciprocating compressors in oil and gas industry may
be retrofitted to include one or more actuated valves having the valve closing member
attached to the respective counter-seat. A flow diagram of a method 400 to retrofit a
reciprocating compressor is illustrated in Figure 6. The method 400 includes fixedly
attaching the valve closing member to the counter-seat on a surface of the counter-seat
towards the seat, at 8410. Further, the method includes connecting an actuator to the counterseat,
to enable the counter-seat to receive an actuating motion to move between a closed
position in which the valve closing member covers an inlet port through a seat of the valve,
and an opened position in which the valve closing member does not cover the inlet port, at
8420.
The method 400 may further include removing a spring between the counter-seat and the
valve closing member before attaching the valve closing member to the counter-seat, and/or
removing a spacer (such as 115 in Figures 2A and 2B) originally located between the seat and
the counter-seat. The method 400 may also include adding the actuator to the reciprocating
compressor ifthe original valve was an automated valve (i.e., without an actuator).
The disclosed exemplary embodiments provide valve assemblies without springs and
reciprocating compressors using these valve assemblies. It should be understood that this
description is not intended to limit the invention. On the contrary, the exemplary
embodiments are intended to cover alternatives, modifications and equivalents, which are
included in the spirit and scope of the invention as defined by the appended claims.
Further, in the detailed description of the exemplary embodiments, numerous specific
details are set forth in order to provide a comprehensive understanding of the claimed
invention. However, one skilled in the art would understand that various embodiments
may be practiced without such specific details.
Although the features and elements of the present exemplary embodiments are described in
the embodiments in particular combinations, each feature or element can be used alone
without the other features and elements of the embodiments or in various combinations with
or without other features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to enable any person
skilled in the art to practice the same, including making and using any devices or systems and
10
perfonning any incorporated methods. The patentable scope of the subject matter is defined
by the claims, and may include other examples that occur to those skilled in the art. Such
other examples are intended to be within the scope of the claims.

WE CLAIMS:
1. A valve assembly used in a reciprocating compressor for oil and gas industry,
comprising:
an actuator configured to provide a valve actuating motion;
a valve having
a valve seat configured to allow a fluid to flow through the valve seat, via an inlet port
thereof;
a counter-seat configured to allow the fluid to flow through the counter-seat, via an outlet
port thereof; and
a valve closing member attached to the counter-seat, located and configured to cover the
inlet port when the counter seat is in a closed position,
wherein the counter-seat receiving the valve actuating motion moves between the closed
position and an open position in which the valve closing member does not cover the inlet
port thereby selectively allowing the fluid to flow on a flow path including the inlet port
and the outlet port.
2. A reciprocating compressor, comprising:
an actuator configured to provide a valve actuating motion;
a valve having
a valve seat configured to allow a fluid to flow through the valve seat, via an inlet port
thereof;
a counter-seat configured to allow the fluid to flow through the counter-seat, via an outlet
port thereof; and
a valve closing member attached to the counter-seat, located and configured to cover the
inlet port when the counter seat is in a closed position,
wherein the counter-seat receiving the valve actuating motion moves between the closed
position and an open position in which the valve closing member does not cover the inlet
port thereby selectively allowing the fluid to flow on a flow path including the inlet port
and the outlet port.
3. The reciprocating compressor of claim 2, wherein the valve closing member
12
comprises one or more disc shaped parts.
4. The reciprocating compressor of claim 2, wherein the valve closing member
comprises one or more ring shaped parts.
5. The reciprocating compressor of claim 2, wherein the valve closing member and
the counter-seat are formed as a single piece.
6. The reciprocating compressor of claim 2, wherein the valve closing member is
formed separately from the counter-seat and attached thereof.
7. The reciprocating compressor of claim 6, wherein the valve is configured according
to at least one of the following characteristics:
the counter-seat is configured to have a groove inside which the valve closing member is
placed, a height of the groove being smaller than a height of the valve closing member,
the valve closing member is glued, attached with screws or welded to the counter-seat, and
at least one of an opening of the inlet port on a surface of the seat towards the counter-seat,
and the valve closing member have profiles shaped to lower flow resistance along the flow
path.
8. The reciprocating compressor of claim 2, further comprising:
a compression chamber, wherein the outlet port opens to the compression chamber.
9. A method of retrofitting a compressor initially having a valve with a spring
between a valve closing member and a counter-seat of the valve, the valve initially closing
due to a differential pressure, to have the valve actuated and the valve closing member
attached to the counter-seat of the valve, the method comprising:
fixedly attaching the valve closing member to the counter-seat of the valve; and
connecting an actuator to the counter-seat, to enable the counter-seat to receive an
actuating motion to move between a closed position in which the valve closing member
covers an inlet port through a seat of the valve, and an opened position in which the valve
closing member does not cover the inlet port.
10. The method of claim 9, further comprising at least one of:
removing a spring between the counter-seat and the valve closing member before attaching
the valve closing member to the counter-seat.
(ADR/Pa)
Do..L.-d ~ --tfu cJ.-o:J d ~b-d~' 2-
~~Q' 13 a..v...
IvfANISHA SING NAIR
~gent for the Applicant [IN/PA-740]
~EX ORBIS
Intellectual Property P t'
7091710 T rae Ice . ' olstoy House,
.1~-17, Tolstoy Marg,
New Dclhi-llOOOJ