ROTATIVE VALVES FOR RECIPROCATING COMPRESSORS AND RELATED METHODS

Abstract

Reciprocating compressors having a rotative valve and related methods are provided. A reciprocating compressor has a compression chamber configured to compress a fluid that has entered the compression chamber via an intake, and it is discharged from the compression chamber, after being compressed, via a discharge, an actuator configured to supply an angular displacement, and a rotative valve configured to receive the angular displacement and to determine whether the intake and the discharge are opened or closed depending on the angular displacement. The rotative valve has a rotatable disk configured to rotate due to the angular displacement and having a first opening allowing a suction fluid flow to enter the compression chamber when the first opening overlaps the intake, and a second opening allowing a discharge fluid flow to exit from the compression chamber when the second opening overlaps the discharge.

Description

BACKGROUND

Embodiments of the subject matter disclosed herein generally relate to apparatuses and methods for using a single actuator to control both intake and discharge of fluid in a compression chamber of a reciprocating compressor; more particularly, to actuate a rotative valve configured to close or open an intake flow path and a discharge flow path to/from a compression chamber.

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 its volume. 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.

FIG. 1 is an illustration of a conventional dual chamber reciprocal compressor 10. The fluid compression occurs inside a body 20, usually having a cylindrical shape. A fluid to be compressed (e.g., natural gas) is input into the body 20 via an inlet 30 and suction valves 32 and 34, and, after the compression, the fluid is output via an outlet 40 and discharge valves 42 and 44. The compression is a cyclical process in which the fluid is compressed due to a movement of the piston 50 inside the body 20, between a head end 26 and a crank end 28. The piston 50 divides the body 20 into two compression chambers 22 and 24 that operate in different phases of the compression cycle, the volume of the 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 are configured to open to allow the incoming fluid (having a first pressure P₁) to enter into the compression chambers 22 and 24, respectively. Discharge valves 42 and 44 are configured to open to allow the outgoing compressed fluid (having a second pressure P₂>P₁) to be output from the compression chambers 22 and 24, respectively. The piston 50 moves due to energy transmitted from a crankshaft 60 via a crosshead 70 and a piston rod 80. The valves 32, 34, 42, and 44 are illustrated on side walls of the body 20, but they can also be located on the head end 26 and the crank end 28 of the body 20.

Conventionally, the suction and the discharge valves used in a reciprocating compressor are automatic valves that are switched between a closed state and an open state due to a differential pressure across the valve (i.e., between the pressure on one side of a mobile part of the valve and the pressure on the other side of the mobile part). The automatic valves have the disadvantage that they add significantly to the clearance volume of the compression chamber, the clearance volume (e.g., 25) being a volume that cannot be efficiently used in the compression cycle. The larger the clearance volume, the smaller is the compression efficiency.

Actuated rotary valves minimize the portion of the clearance volume of the compression chamber due to the valves, and increase the flow area. FIGS. 2A and 2B illustrate a conventional rotary valve 200 that may be placed opening or closing a flow pathway between the inlet 30 and the compression chamber 22. The valve 200 may be considered to be used instead any of the valves 32, 34, 42, and 44. The valve 200 includes a seat (or stator) 210 and a rotor 220. The seat 210 and the rotor 220 are coaxial disks with openings spanning a sector of the same size around a stem 230. The rotor 220 may be actuated to rotate around the stem 230 from a first position (FIG. 2A) in which the rotor's opening 222 overlaps the seat's opening 212, to a second position (FIG. 2B) in which the rotor's opening 222 and the seat's opening 212 (shown using dashed line) span different sectors. When the rotor 220 is in the first position, the rotary valve 200 is in the open state, allowing a fluid to flow through the valve. When the rotor 220 is in the second position, the rotary valve 200 is in the closed state, thus preventing the fluid from flowing through the valve.

The use of rotary valves is difficult if at all feasible for compressors used in the oil and gas industry. Compressors used in the oil and gas industry have to meet industry-specific requirements that take into consideration, for example, that the compressed fluid is frequently corrosive and flammable. American Petroleum Institute (API), the organization setting the recognized industry standard for equipment used in the oil and gas industry, has issued a document, API618, listing a complete set of minimum requirements for reciprocating compressors.

Considering that valves used in oil and gas compressors typically have an actuation time of about 5 ms, in order to actuate rotary valves for such compressors, voluminous (relative to available space) actuators would be necessary. Due to potential danger of an explosion, electrical valve actuators (that are capable of providing the required actuation time) are preferably placed such as not to be in contact with the flammable gas, the motion generated by these actuators being mechanically transmitted to the valve's mobile part that is in contact with the fluid. The space necessary to place an actuator and a mechanism for transmitting a displacement generated by the actuator to the valve's mobile part may not always be available. Additionally, the crank end side of a dual reciprocating compressor usually has less room than the head end side.

Accordingly, it would be desirable to provide alternative solutions to the automated valves for reciprocating compressors used in the oil and gas industry, meeting the requirements and taking into consideration the limited space.

SUMMARY

Using rotative valves in reciprocating compressors has the advantage of controlling both suction and discharge flow pathways with a single actuator. Rotative valves may be mounted at the head end and at the crank end of a dual reciprocating compressor. Two rotative valves in a dual reciprocating compressor may be actuated using the same actuator.

According to an exemplary embodiment, a reciprocating compressor has (1) a compression chamber configured to compress a fluid that has entered the compression chamber via an intake, and is discharged from the compression chamber, after being compressed, via a discharge, (2) an actuator configured to supply an angular displacement, and (3) a rotative valve configured to receive the angular displacement and to control whether the intake and the discharge are opened or closed depending on the angular displacement. The rotative valve includes a rotatable disk configured to rotate due to the angular displacement and having a first opening, allowing a suction fluid flow to enter the compression chamber when the first opening overlaps the intake, and a second opening allowing a discharge fluid flow to exit from the compression chamber when the second opening overlaps the discharge.

According to another exemplary embodiment, a dual reciprocating compressor has (1) a body divided into two compression chambers, each compression chamber being configured to compress a fluid that has entered the compression chamber via an intake, and is discharged from the compression chamber via a discharge, (2) a piston configured to move along the body, thereby varying volumes of the two compression chambers, (3) an actuator configured to supply an angular displacement, and (4) two rotative valves located on opposite ends of the body and configured to receive the angular displacement and to control whether the intake and the discharge of a respective chamber are opened or closed depending on the angular displacement. Each rotative valve includes a rotatable disk configured to rotate due to the angular displacement and having (A) a first opening allowing a suction fluid flow to enter the respective compression chamber when the first opening overlaps the intake, and (B) a second opening allowing a discharge fluid flow to exit from the respective compression chamber when the second opening overlaps the discharge. The angular actuation of at least one of the two rotative valves is caused by the angular displacement.

According to another exemplary embodiment, a rotative valve useable at one end of a compression chamber having an end plate with a suction opening configured to allow a suction fluid flow to enter the compression chamber, and a discharge opening configured to allow a discharge fluid flow to exit the compression chamber. The rotative valve includes a rotatable disk having a first opening and a second opening positioned at different angular locations such that, when the first opening overlaps the suction opening, the suction fluid flow passes there-through, and when the second opening overlaps the discharge opening, the discharge fluid flow passes there-through.

According to another exemplary embodiment, a method of retrofitting a reciprocating compressor initially having two automated valves located on an end plate of a compression chamber of the reciprocating compressor is provided. The method includes (1) removing mobile parts of the valves, while leaving seats of the valves in place, each seat having an opening toward an inside of the compression chamber, (2) providing an actuator configured to supply an angular displacement, (3) mounting, outside the end of the compression chamber, a rotatable disk having two openings at different angular positions, such that one of the openings of the rotatable disk overlaps the opening of one of the seats at a first angular position, and another one of the openings of the rotatable disk overlaps the opening of another one of the seats at a second angular position, different from the first angular position. The method further includes (4) connecting the rotatable disk to the actuator to enable the rotatable disk to rotate due to the angular displacement to positions in which one of the openings of the rotatable disk overlaps the openings of one of the seats, respectively, allowing a fluid flow to pass there-through toward or from the compression chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:

FIG. 1 is a schematic diagram of a conventional dual chamber reciprocating compressor;

FIGS. 2A and 2B illustrate a conventional actuated rotary valve in an open state and in a closed state, respectively;

FIG. 3 is a schematic diagram of a single chamber reciprocating compressor according to an exemplary embodiment;

FIG. 4 is an illustration of a rotatable disk of a rotative valve according to an exemplary embodiment;

FIG. 5 is a schematic diagram of a double chamber reciprocating compressor according to an exemplary embodiment;

FIG. 6 is a schematic diagram of a double chamber reciprocating compressor according to an exemplary embodiment; and

FIG. 7 is a flowchart of a method of retrofitting a reciprocating compressor 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 compressors used in the oil and gas industry. However, the embodiments to be discussed next are not limited to these compressors, but may be applied to other systems that require the supply of force at a low price and with a reduced footprint.

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.

As discussed relative to the background art, one technical problem related to the use of actuated valves in reciprocating compressors is that an actuator capable of providing an angular displacement in a very short time (i.e., approximately 5 ms) is relatively voluminous and electrical. Due to the flammable nature of the fluid in the oil and gas industry, the actuator is not to be in contact with the fluid, and the actuation motion has then to be transmitted to the valve's mobile part, which is in contact with the fluid. The space necessary to fit an actuator and the transmission mechanism for each valve may not be available in meaningful proximity to the reciprocating compressor's valves. Some of the embodiments described below use a single actuator for controlling (i.e., opening and closing) two flow paths to/from a compression chamber. Moreover, in some embodiments, the same actuator controls all four flow paths to/from two compression chambers of a dual reciprocating compressor.

According to an exemplary embodiment illustrated in FIG. 3, a single chamber reciprocating compressor 300 has a compression chamber 310 configured to receive a fluid via an intake 320, compress the fluid and then discharge it from the compression chamber 310 via a discharge 330. Whether the fluid flow pathways to the compression chamber 310 from the intake 320 and from the compression chamber 310 to the discharge 330 are opened depends on the position of openings of a rotatable disk 340 which rotates due to an angular displacement supplied by an actuator 350. The rotatable disk 340 is the switching (moving) component of a rotative valve that controls whether the fluid flows toward and from the compression chamber 310. The openings of the rotatable disk 340 are configured to match the intake 320 and the discharge 330 at certain angular positions. The intake 320 and the discharge 330 are formed in a head end 360 of the compression chamber 310. A cover 365 separates the ambient from the volume in which the rotatable disk 340 is located.

The fluid compression is performed cyclically due to a back-and-forth motion of a piston 370 along an axis 375 correlated with timely opening or closing of the intake 320 and the discharge 330 by the rotatable disk 340.

A frontal view of the rotatable disk 340 is illustrated in FIG. 4. The rotatable disk 340 has a first opening 342 through which the fluid flow enters the compression chamber 310 when the first opening 342 overlaps the intake 320. The rotatable disk 340 also has a second opening 344 through which the fluid flow exits the compression chamber 310, when the second opening 344 overlaps the discharge 330.

An angular displacement of the rotatable disk 340 is transmitted from the actuator 350 via a gear mechanism. The angular displacement may be a continuous rotation (one direction) or an alternating (clockwise and counter-clockwise) rotation. The actuator 350 is, in an embodiment, placed outside the fluid for avoiding the danger of explosion (given that fluids are likely flammable). The gear mechanism includes a valve stem 380 penetrating through the cover 365. A gear 382 is attached to the end of the valve stem 380 and meshed with the rotatable disk 340 (i.e., teeth 382A of the gear 382 engage teeth 340A of the rotatable disk 340), inside the volume filled with fluid between the disk 340 and the cover 365. Another gear 384 is attached to the other end of the valve stem 380. One end of an actuator stem 390 is attached to the actuator 350, and the other end is attached to a gear 392, which is meshed with the gear 384 (i.e., teeth 384A of the gear 384 engage teeth 392A of the gear 392). The valve stem 380 may have collars 386 and bushings 388 on both sides of the cover 365 to enhance its stability in operation.

In FIG. 3, the actuator 350 and the gear mechanism are illustrated to be located closer to the intake 320. However, in other embodiments it may be closer to the discharge 330 or located at another location around the compression chamber 310. No relative dimensional relationship between components should be inferred from FIG. 3 or other exemplary embodiments illustrated in the figures.

A dual chamber (or action) reciprocating compressor is more frequently employed in the oil and gas industry than the single chamber (or action) reciprocating compressor. FIG. 5 illustrates a dual chamber reciprocating compressor 500 according to another exemplary embodiment. The fluid is compressed due to the back-and-forth movement of a piston 510 provided inside a body 520, between a head end plate 530 and a crank end plate 540. The piston 510 divides the body 520 into two compression chambers 522 and 524 that operate in different phases, the volume of compression chamber 522 being at its lowest value when the volume of compression chamber 524 is at its highest value and vice-versa. The piston 510 moves back and forth due to energy received, for example, from a crankshaft (not shown) via a crosshead (not shown) and a piston rod 512.

An intake 532 and a discharge 534, which communicate with the compression chamber 522, are formed through the head end plate 530. Similarly, an intake 542 and a discharge 544, which communicate with the compression chamber 524, are formed through the crank end plate 540. Outside the body 520, rotatable disks 550 and 560, are disposed at the head end and at the crank end, respectively. The rotatable disks 550 and 560 are configured to rotate due to the angular displacement received from actuators 570 and 580, respectively. Each of the rotatable disks 550 and 560 has a first opening allowing a fluid flow to enter the respective compression chamber, 522 or 524, when the first opening overlaps the intake 532 or 542, respectively. Further, each of the rotatable disks 550 and 560 has a second opening allowing the fluid flow to exit from the respective compression chamber, 522 or 524, when the second opening overlaps the discharge, 534 or 544, respectively. A structure of the rotatable disks 550 and 560 may be similar to the rotatable disk 340 shown in FIG. 4. Some of the details at the crank-end side (i.e., around the rotatable disk 560) are omitted to keep the relevant details clear.

Gear assemblies 575 and 585 are configured to transmit the angular displacement from the actuators 570 and 580, respectively, to the rotatable disks 550 and 560, respectively. Covers 555 and 565 separate a fluid volume from the ambient. A detailed description of each of the components of the gear assemblies is omitted because the gear assemblies are similar to the gear assembly described for the single chamber compressor 300.

Although in FIG. 5, the dual chamber reciprocating compressor 500 is illustrated as having rotative valves (as defined by the rotatable disks) 550 and 560 at both a head end and at a crank end thereof, alternative embodiments may have a rotative valve only at one of the head end and the crank end, having other types of valves at the other end of the compression chambers.

FIG. 6 illustrates a dual chamber reciprocating compressor 600 having rotative valves at both the head end and at the crank end. The rotative disks 550 and 560 of the compressor 600 are actuated by the same single actuator 590 instead of two actuators 570 and 580 in FIG. 5. Description of the components of the reciprocating compressor 600 similar to those of the reciprocating compressor 500 is not repeated.

Existing reciprocating compressors with automated valves can be retrofitted to use actuated rotative valve(s). A method 700 of retrofitting a reciprocating compressor initially having two automated valves located on an end plate of a compression chamber of the reciprocating compressor is illustrated in FIG. 7. The method 700 includes removing mobile parts of the automated valves, while leaving seats of the automated valves in place, each seat having an opening toward an inside of the compression chamber at S710. The seat of a suction valve may serve as the intake, and the seat of the discharge valve may serve as the discharge.

The method 700 further includes providing an actuator configured and connected to supply an angular displacement, at S720, and mounting, outside the end of the compression chamber, a rotatable disk having two openings at different angular positions, at S730.

The method 700 also includes connecting the rotatable disk to the actuator to enable the disk to rotate due to the angular displacement to positions in which one of the openings of the disk overlaps the opening of one of the seats, respectively, allowing a fluid flow to pass there-through toward or from the compression chamber, at S740.

The method 700 may further include mounting a gear mechanism to transmit the angular displacement from the actuator to the rotatable disk. The gear mechanism may be configured to penetrate though a cover of the reciprocating compressor separating a volume filled with fluid from ambient, where the actuator is located.

If the retrofitted reciprocating compressor is a dual chamber reciprocating compressor having two back-to-back compression chambers in a body, and initially having two other automatic valves located on an opposite end of the body than the end on which the two automatic valves are located, the method 700 may further comprise steps to replace the two other automatic valves with another rotative valve. Thus, the method 700 may further include (1) removing mobile parts of the other two valves while leaving seats of the other two valves in place, each seat having an opening toward an inside of another compression chamber, (2) mounting, outside the opposite end, another rotatable disk having two other openings at different angular positions, and (3) connecting the other rotatable disk to the actuator, to enable the other rotatable disk to rotate due to the angular displacement to positions in which one of the openings of the other rotatable disk overlaps one of the two other openings, respectively, allowing a fluid flow to pass there-through toward or from the other compression chamber.

The disclosed exemplary embodiments provide reciprocating compressors with at least one rotative valve and a method for retrofitting existing reciprocating compressors to have at least one rotative valve. 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 performing 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.

Claims

1. A reciprocating compressor, comprising:

a compression chamber configured to compress a fluid that has entered the compression chamber via an intake, and it is discharged from the compression chamber, after being compressed, via a discharge;

an actuator configured to supply an angular displacement; and

a rotative valve configured to receive the angular displacement and to control whether the intake and the discharge are opened or closed depending on the angular displacement, the rotative valve comprising: a rotatable disk configured to rotate due to the angular displacement; a first opening allowing a suction fluid flow to enter the compression chamber when the first opening overlaps the intake; and a second opening allowing a discharge fluid flow to exit from the compression chamber when the second opening overlaps the discharge.

2. The reciprocating compressor of claim 1, further comprising:

a gear mechanism located outside of the compression chamber and configured to transmit the angular displacement from the actuator to the rotatable disk of the rotative valve.

3. The reciprocating compressor of claim 2, wherein the gear mechanism comprises:

an actuator stem connected to the actuator; and

at least two gears comprising a first gear being attached to and rotating with the actuator stem, and a second gear transmitting the angular displacement to the rotatable disk of the rotative valve.

4. The reciprocating compressor of claim 3, further comprising:

a cover, the actuator being located outside the cover and the rotative valve being located inside the volume,

wherein the gear mechanism further comprises: a valve stem configured to penetrate through the cover and having the second gear at one end, and a third gear connected to another end of the valve stem and meshed with the first gear.

5. The reciprocating compressor of claim 4, wherein:

the valve stem is configured to have a first collar between the cover and the second gear, and a second collar between the cover and the third gear, and

the gear mechanism further comprises a first bushing placed between the first collar and the cover, and a second bushing placed between the second collar and the cover.

6. The reciprocating compressor of claim 1, wherein the reciprocating compressor is a dual reciprocating compressor comprising two compression chambers, and the rotative valve is located on a head end or on a crank end thereof, wherein the compression chamber is one of the two compression chambers.

7. The reciprocating compressor of claim 6, further comprising:

a second rotative valve configured to control whether an intake and a discharge of another one of the two compression chambers, to be opened or closed depending on an angular actuation applied to a second rotatable disk configured to rotate due to the angular actuation and comprising: another first opening allowing a suction fluid flow to enter the another one of the two compression chambers, when the another first opening overlaps the intake; and another second opening allowing a discharge fluid flow to exit from the another one of the two compression chambers, when the another second opening overlaps the discharge.

8. The reciprocating compressor of claim 7, further comprising:

at least one gear mechanism configured to transmit the angular displacement from the actuator to cause the angular actuation of the rotatable disk of at least one of the rotative valve and the second rotative valve.

9. A rotative valve useable at one end of a compression chamber, wherein the compression chamber comprises an end plate with a suction opening configured to allow a suction fluid flow to enter the compression chamber, and a discharge opening configured to allow a discharge fluid flow to exit the compression chamber, the rotative valve comprising:

a rotatable disk configured to be rotated and comprising a first opening and a second opening positioned at different angular locations, wherein, when the first opening overlaps the suction opening, the suction fluid flow passes there-through, and when the second opening overlaps the discharge opening, the discharge fluid flow passes there-through.

10. A reciprocating compressor, comprising:

a compression chamber configured to compress a fluid that has entered the compression chamber via an intake and to be discharged from the compression chamber after being compressed via a discharge,

an actuator configured to supply an angular displacement; and

the rotative valve according to claim 9 to receive the angular displacement.

11. The reciprocating compressor according to claim 1, further comprising the rotative valve according to claim 9.

12. A method of retrofitting a reciprocating compressor initially comprising two automated valves located on an end plate of a compression chamber of the reciprocating compressor, the method comprising:

removing mobile parts of the valves, while leaving seats of the valves in place, each seat comprising an opening towards an inside of the compression chamber;

providing an actuator configured to supply an angular displacement;

mounting, outside the end of the compression chamber, a rotatable disk comprising two openings at different angular positions, such that one of the openings of the rotatable disk to overlap the opening of one of the seats, at a first angular position, and another one of the openings of the rotatable disk to overlap the opening of another one of the seats, at a second angular position different from the first angular position; and

connecting the rotatable disk to the actuator, to enable the rotatable disk to rotate due to the angular displacement.