CA2254530A1 - Plug valve - Google Patents

Abstract

A plug valve having a tapered plug that seats in a first flow passage in a valve body is disclosed. The plug defines a second flow passage cooperating with the first flow passage so that by rotating the plug through 90°
the plug valve is fully open or fully closed. The plug valve is opened by rotating the plug in a counterclockwise direction which also lifts the plug in an axial direction away from the valve seats. When the plug valve is rotated in a clockwise direction, the plug is rotated and moves in a downward axial direction into engagement with the valve seats. A resilient biasing member is provided between the valve seats and the valve body to continuously bias the valve seats into engagement with the plug.

Description

> CA 02254530 1998-11-26 PLUG VALVE
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to valves for use with fluid and gaseous systems and, more particularly, to a tapered plug valve having resiliently biased valve seats.

2. Description of the Prior Art Plug valves for use with fluid systems are well known. Plug valves have advantages over other known types of valves such as ball valves, globe valves and gate valves for applications that require straight through flow and quick on/off service. For example, other types of valves, such as ball valves, provide similar straight through flow and quick shut-off service, but tend to require a sealing member. Sealing members are expensive and cannot be used at high temperatures because of heat damage to the seal.
Additionally, plug valves are economical to produce, require a minimum amount of machining to fabricate and are relatively easy to assemble compared to other types of valves. Most importantly, however, plug valves can be quickly operated from a full open position to a full closed position by a one-quarter turn of a valve handle.
Generally, plug valves have been constructed to have a plug member wedge and seat against tapered valve seats. Consequently, to provide a fluid tight seal between the plug member and the valve seats a relatively large bearing force must be applied downward on the plug member.
Additionally, prior art plug valves generally have the plug member engaging a bearing surface within the valve body.
The frictional interaction between the working faces of the plug member and the bearing surface requires that a considerable operating force be employed to open and close the plug valve. Some plug valves employ a lubricant between the working faces of the plug member and the bearing surface to lessen the force required to operate the plug valve. However, the use of a lubricant makes the plug valve unsuitable for use at high temperatures or with food products.

One prior art solution to the above-discussed problems has been to provide O-rings between the valve seats and the plug member. The O-rings provide a fluid tight seal between the valve seats and the plug member.
Additionally, it is known to use O-rings to bias the valve seats into engagement with the plug member. This type of construction is not limited to plug valves, but is generally known in the art. For example, U.S. Patent No.
4,762,301 to Wozniak et al. discloses a ball valve incorporating O-rings that co-act with valve seats for both sealing and biasing the valve seats into engagement with a ball member.
Plug valves having tapered plug members are also known in the art as exhibited by U.S. Patent No. 4,239,185 to Lowe, incorporated herein by reference. The Lowe patent discloses a plug valve that when rotated to the open position causes the plug member to rotate and "lift"
slightly from the valve seats. Rotating the plug valve to the closed position causes the plug member to rotate and move downward to engage the valve seats. The combination of rotational and vertical movement, in effect, a spiral motion of the plug member, is known to provide a plug valve that has an effective seal, ease of manipulation and full throttling with a one-quarter turn of the tapered plug member.
The plug valve disclosed by the Lowe patent, however, tends to have a valve body which while in the open position of the plug valve, by its current design, creates a space between an outer surface of the valve seats and the outer surface of the plug member, or rotor. This space causes and allows any particles in the fluid or gaseous system, or media, to "set" or build-up in the space. The particles that become trapped into this space cause the valve to malfunction. When the operator attempts to close the plug valve and the plug member or rotor moves downward trying to engage the valve seats, the plug member encounters the particle build-up. As a result of the particle build-up, the plug valve will be prevented from being rotated a complete one-quarter turn and, hence, from being placed in the closed position. The plug valve will leak and/or seize-up. Therefore, it would be advantageous to provide an improved Lowe-type plug valve having a plug member that exhibits "spiral" motion and, further, has valve seats that are resiliently biased into engagement with the surface of the plug member at all times and in any position of the plug member.
Accordingly, it is an object of the present invention to provide a plug valve that has improved service characteristics over the above-discussed prior art valves.
It is a further object of the present invention to provide an improved plug valve that has ease of manipulation and full throttling with a one-quarter turn of a tapered plug member. It is still a further object of the present invention to provide a plug valve having improved leakage performance over the above-discussed Lowe-type plug valves.
SUMMARY OF THE INVENTION
The present invention relates to a plug valve that includes a valve body, a tapered plug positioned within the valve body, an elongated stem positioned in the valve body and having one end in engagement with the plug, seats engaging opposed sides of the plug and a resilient biasing member biasing each of the seats into engagement with the plug.
The valve body may deffine a ffirst flow passage and the plug may define a second flow passage. The plug may be positioned in the valve body such that in an open position of the plug valve, the second flow passage is substantially aligned and in fluid communication with the first flow passage. In a closed position of the valve, the plug may close the first flow passage to flow. The stem may co-act with the plug such that rotation of the stem simultaneously rotates the plug and moves the plug in an axial direction substantially perpendicular to a longitudinal axis of the first flow passage.

The resilient biasing members may be O-rings or springs. If the resilient biasing members are O-rings, the O-rings may provide a fluid tight seal between the valve body and the seats. The plug may define a slot in an upper end of the plug. The stem may include a flat end portion engaging the slot permitting movement of the plug relative to the stem in a direction substantially perpendicular to a longitudinal axis of the stem.
The valve body may include a first valve body member connected to a second valve body member. The stem may extend through the first valve body member and into the second valve body member. The first valve body member may define a first recess adjacent the second valve body member. The first valve body member may further define a second recess having an O-ring positioned therein providing a fluid seal between the first valve body member and the stem. The second valve body member may define an opening connected to the first flow passage. The opening may have the plug partially positioned therein. The first valve body member may be connected to the second valve body member such that a cavity is formed between the first recess and the plug. The stem may include a threaded portion received in the cavity.
A mounting nut may be positioned in the cavity and a sealing ring may be positioned around the mounting nut forming a fluid seal between the first valve body member, the second valve body member and the mounting nut.
The threaded portion of the stem may engage internal threads of the mounting nut. The first valve body member may be connected to the second valve body member such that the mounting nut is nonrotatably held in the cavity.
The first flow passage may include an inlet port and an outlet port each having internal threads for connecting to threaded conduit. Alternatively, the inlet port and the outlet port may have flanges for connecting to flanged pipe. The first valve body member may be welded or mechanically fastened to the second valve body member.

Further details and advantages of the present invention will become apparent with the following detailed description, in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic side view of a plug valve in accordance with the present invention having flanges;
Fig. 2 is a sectional view of the plug valve in an open position;
Fig. 3 is a sectional view of the plug valve in a closed position;
Fig. 4 is a perspective view of a stem and tapered plug of the plug valve;
Fig. 5 is a partial sectional view of the plug valve of Fig. 2;
Fig. 6 is a partial sectional view of the plug valve of Fig. 3;
Fig. 7 is a secticnal view of the plug valve in the closed position and under pressure; and Fig. 8 is a partial sectional view of a plug valve in accordance with the present invention having resilient biasing members in the form of springs.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to Figs . 1-3 , a plug valve 10 made in accordance with the present invention is shown. The plug valve 10 includes a valve body 20 having an upper or first valve body member 22 connected to a lower or second valve body member 24. A cap member 26 is connected to the first valve body member 22. The first valve body member 22 is preferably welded to the second valve body member 24 to provide a fluid tight seal therebetween. Figs. 2 and 3 show a weld 28 between the first valve body member 22 and the second valve body member 24. Alternatively, the first valve body member 22 can be mechanically fastened to the second valve body member 24 by bolts, or by any other means known in the art.
The second valve body member 24 defines a first f low passage 30 extending therethrough. The first f low passage 30 includes an inlet port 32 and an outlet port 34 that are threaded for coupling to threaded conduit (not shown). Alternatively, as shown in Fig. 1, flanges 36 may be provided around the inlet port 32 and the outlet port 34 for connection to flanged conduit (not shown) by socket welding or butt welding as is well known in the art.
The first valve body member 22 is substantially annular-shaped and defines a first recess 38 and a second recess 40. The first recess 38 is defined adjacent the second valve body member 24. The second valve body member 24 defines an opening 42 connected to the first flow passage 30 and substantially aligned with the first recess 38. The cap member 26 includes internal threads 44 removably engaged with external threads 46 on the first valve body member 22.
Referring now to Figs. 2-4, a tapered plug 50 is positioned within the second valve body member 24. The plug 50 is substantially cylindrical-shaped and includes a tapered side wall 52. An exemplary taper of the side wall 52 is about 7°. The plug 50 defines a second flow passage 54. A dove tail slot 56 is defined in an upper end 58 of the plug 50. The plug 50 is positioned in the second valve body member 24 so that the tapered side wall 52 extends into the first flow passage 30. The plug 50 is at least partially received in the opening 42. The first valve body member 22 is connected to the second valve body member 24 so that a cavity 59 is formed between the first recess 38 and the upper end 58 of the plug 50. The cavity 59 bridges the first valve body member 22 and the second valve body member 24.
An elongated stem 60 extends through the first valve body member 22 and into the second valve body member 24. The stem 60 is configured to co-act with the plug 50.
The stem 60 includes a threaded portion 62 adjacent a flat dove tail end portion 64. The flat end portion 64 engages the dove tail slot 56 defined in the upper end 58 of the plug 50. The threaded portion 62 of the stem 60 is received within the cavity 59. The other end of the stem 60 preferably includes a handle 66 connected thereto for operating the plug valve 10 from an open position to a closed position as discussed hereinafter.
An O-ring 67 is positioned in the second recess 40 defined by the first valve body member 22 to provide a fluid tight seal between the first valve body member 22 and the stem 60, making the plug valve 10 suitable for vacuum service in addition to liquid and gaseous service.
Conventional packing rings 68 are provided around the stem 60 between the stem 60 and the first valve body member 22 as is well known in the art.
A mounting nut 70 is positioned in the cavity 59.
The cavity 59 is formed and the first valve body member 22 is connected to the second valve body member 24 so that the mounting nut 70 is nonrotatably held between the first valve body member 22 and the second valve body member 24.
A sealing member 72, or gasket, provides a fluid tight seal between the first valve body member 22 and the second valve body member 24. The sealing member 72 is preferably used in the embodiment of the plug valve 10 in which the first valve body member 22 is mechanically fastened to the second valve body member 24 with bolts. The threaded portion 62 of the stem 60 co-acts with internal threads of the mounting nut 70. The stem 60 co-acts with the mounting nut 70 to create the upper and lowering movements of the plug 50 when the handle 66 is operated as discussed fully hereinafter.
The plug 50 is seated in sealing relation and for 3 0 rotation in the first f low passage 3 0 by valve seats 8 0 .
The seats 80 are positioned between the second valve body member 24 and the plug 50 on opposed sides of the plug 50.
The seats 80 are tubular-shaped and have slanted tapered surfaces 82 for engaging the tapered side wall 52 of the plug 50. The seats 80 are supported in the first flow passage 30 and are free to move in a direction substantially perpendicular to the plug 50 so as to form a - 7 _ continuous fluid tight seal with the plug 50, as described hereinafter.
A resilient biasing member 84 is located between each of the seats 80 and the second valve body member 24.
The resilient biasing members 84 provide a resilient biasing force against the seats 80 so that the tapered surfaces 82 of the seats 80 continuously engage the tapered side wall 52 of the plug 50 at the opposed sides of the plug 50. The tapered surfaces 82 of the seats 80 thereby form a fluid tight seal with the tapered side wall 52 of the plug 50. The resilient biasing members 84 are preferably O-rings that will also form a fluid tight seal between the second valve body member 24 and the seats 80.
Alternatively, the resilient biasing members 84 may be springs 86, as shown in Fig. 8, continuously biasing the seats 80 into engagement with the plug 50 at opposed sides of the plug 50. The resilient biasing members 84 in either embodiment permit rotation. of the plug 50 in the seats 80.
Referring to Figs. 5-7, operation of the plug valve 10 will now be discussed. Fig. 5 shows the plug valve 10 in the open position in which the first flow passage 30 is substantially aligned and in fluid communication with the second flow passage 54. The resilient biasing members 84, in this case O-rings, provide a resilient biasing force urging the seats 80 into engagement with the opposed sides of the plug 50 so that a continuous fluid tight seal exists between the seats 80 and the plug 50. Additionally, the O-rings provide a fluid tight seal between the seats 80 and the second valve body member 24. As the valve handle 66, shown in Fig. 2, is rotated 90° in a clockwise direction, the stem 60 will rotate the plug member 50 to the closed position of the plug valve 10 shown in Fig. 6.
Referring now to Fig. 6, the plug valve 10 is shown in the fully closed position. The plug 50 has been rotated 90° so that the second flow passage 54 is no longer aligned with the first flow passage 30 and now lies _ g _ substantially perpendicular thereto. The resilient biasing members 84 continue to bias the seats 80 into engagement with the opposed sides of the plug 50. As discussed above, as the stem 60 is rotated the plug 50 will also rotate in the seats 80. It will be apparent that as the stem 60 is rotated clockwise, the threaded portion 62 of the stem 60 further engages the internal threads of the mounting nut 70 thereby causing the stem 60 and, therefore, plug 50 to move in a downward axial direction substantially perpendicular to a longitudinal axis L of the first flow passage 30. The combined rotational and downward translational movement of the plug 50 is provided by the operative engagement of the flat end portion 64 of the stem 60 with the slot 56 defined in the upper end 58 of the plug 50. A full 90° clockwise rotation of the stem 60 causes the plug 50 to move downward to its lowest position within the second valve body member 24 as shown in Fig. 6. Preferably, the bottom surface of the plug 50 will not engage the interior of the second valve body member 24.
In Fig. 6, it will be apparent that the resilient biasing members 84 are compressed relative to when the plug 50 is in the open position of the plug valve 10 shown in Fig. 5 due to the tapered side wall 52 of the plug 50. As the plug 50 rotates and moves downward in the seats 80, the increasing diameter of the plug 50 pushes outward on the seats 80 compressing the resilient biasing members 84 and, therefore, causing a concurrent increase in the biasing force exerted by the resilient biasing members 84. The combination of rotation and downward translational movement of the plug 50 tends to increase the resilient biasing force exerted on the seats 80 by the resilient biasing members 84. Consequently, the plug valve 10 provides a plug 50 that exhibits rotational and axial vertical movement relative to the longitudinal axis L of the first flow passage 30 and, further, resilient biasing members 84 that provide a greater sealing force against the seats 80 when the plug valve 10 is in the closed position.
_ g _ Furthermore, as shown in Fig. 7, when fluid flow F is introduced under pressure into the inlet port 32 of the first flow passage 30, the plug 50 exhibits movement in a direction substantially perpendicular to a longitudinal axis L' of the stem 60, or relative lateral movement in the direction of fluid flow F. This is because when the plug valve 10 is rotated to the closed position, the dove tail slot 56 defined in the upper end 58 of the plug 50 permits the plug 50 to "slide" relative to the flat dove tail end portion 64 of the stem 60. In the closed position of the plug valve 10, the dove tail slot 56 and flat dove tail end portion 64 are substantially aligned with the direction of fluid flow F. Additionally, as a result of the force of the fluid flow F in the first flow passage 30 and the accompanying movement of the plug 50 in the direction of fluid flow F, the resilient biasing member 84 on the downstream side of the plug 50 will be further compressed, which is exaggerated in Fig. 7 for clarity. The resilient biasing member 84 on the upstream side of the plug 50 expands as the plug 50 moves in the direction of the fluid flow F, which is exaggerated in Fig. 7 for clarity. The resilient biasing member 84 on the downstream side of the plug 50, due to its increased compression, will exert a greater biasing force against the seats 80 than will the upstream resilient biasing member 84. However, it will be understood that the resilient biasing members 84 are chosen such that the seats 80 are at all times continuously biased into engagement with the plug 50.
Referring again to Fig. 1, a stop (not shown) may be provided on the valve body 20 and positioned to coincide with the fully open position of the plug valve 10. The handle 66 is preferably formed to co-act with the stop so that the user of the plug valve 10 can easily determine the open and closed positions of the plug valve 10.
The plug 50 and seats 80 can be made from any compatible combination of metals, such as, straight chromium ferritic stainless steels of the 400 series (ferritic) such as 416; chromium nickel steels (austenitic) of the 300 series such as 316; hard faced combinations of the above or various combinations of bronzes such as ASTM
B-61, B-62 or B-198. The valve body 20 can be of any material compatible with the operating conditions intended for the plug valve 10. Most services are within the scope of ASTM-A-105-II.
The valve will appropriately have two ratings.
The first will be a temperature rating, e.g., 850° F which would be the maximum operating temperature limited to 800 psig. Thus, the valve can be used in steam applications anywhere within the two given parameters. The second rating is a water, oil or gas rating, called WOG in the valve industry, which is an operating pressure for and of water, oil or gas at ambient temperature (70° F). With the proper materials selected, the plug valve 10 can be used on any service within its ratings.
The plug valve made in accordance with the present invention combines a tapered plug that exhibits "spiral" motion with resiliently biased valve seats resulting in a plug valve having improved service characteristics over the prior art. Additionally, the plug valve of the present invention provides the ease of manipulation and quick on/off characteristics known with other types of valves. Furthermore, the plug valve of the present invention has improved leakage performance over prior art plug valves because of the combination of spiral motion of the plug and resiliently biased valve seats.
Although this invention has been described with reference to a preferred embodiment, obvious modifications and alterations of the invention may be made without departing from the spirit and scope of the invention. The scope of the present invention is defined by the appended claims and equivalents thereto.
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Claims (20)

1. A plug valve, comprising:
a valve body defining a first flow passage having a longitudinal axis;
a tapered plug defining a second flow passage and extending into the first flow passage;
an elongated stem positioned in the valve body having one end in engagement with the plug, the stem having a longitudinal axis;
a seat engaging each of the opposed sides of the plug, each of the seats supported in the first flow passage; and a resilient biasing member located between each of the seats and the valve body continuously biasing the seats into engagement with the opposed sides of the plug, wherein in an opened position of the valve the second flow passage is in fluid communication with the first flow passage and in a closed position of the valve the plug closes the first flow passage to flow, and wherein the stem co-acts with the plug such that rotation of the stem simultaneously rotates the plug and moves the plug in an axial direction substantially perpendicular to the longitudinal axis of the first flow passage.

2. The plug valve of claim 1, wherein the resilient biasing member is an O-ring forming a fluid seal between the valve body and the seats.

3. The plug valve of claim 1, wherein the resilient biasing member is a spring.

4. The plug valve of claim 1, wherein the stem includes an end engaging a slot defined in the plug permitting movement of the plug relative to the stem in a direction substantially perpendicular to the longitudinal axis of the stem.

5. The plug valve of claim 1, wherein the valve body further includes a first valve body member connected to a second valve body member, the first valve body member having the stem extending therethrough and defining a first recess adjacent the second valve body member, the second valve body member defining an opening connected to the first flow passage and having the plug partially received therein, wherein the first valve body member is connected to the second valve body member such that a cavity is formed between the first recess and the plug, and wherein the stem includes a threaded portion received within the cavity.

6. The plug valve of claim 5, further including a mounting nut positioned in the cavity, wherein the threaded portion of the stem engages internal threads of the mounting nut.

7. The plug valve of claim 6, wherein the first valve body member is connected to the second valve body member such that the mounting nut is nonrotatably held in the cavity.

8. The plug valve of claim 5, wherein the first valve body member defines a second recess having an O-ring positioned therein providing a fluid seal between the first valve body member and the stem.

9. The plug valve of claim 5, wherein the first valve body member is welded to the second valve body member.

10. The plug valve of claim 1, wherein the first flow passage includes an inlet port and an outlet port, and wherein a flange is provided around the inlet port and the outlet port.

11. A plug valve, comprising:
a valve body defining a first flow passage having a longitudinal axis;
a tapered plug defining a second flow passage and extending into the first flow passage;
an elongated stem positioned in the valve body having one end in engagement with the plug, the stem having a longitudinal axis;
a seat engaging each of the opposed sides of the plug, each of the seats supported in the first flow passage; and an O-ring located between each of the seats and the valve body continuously biasing the seats into engagement with the opposed sides of the plug and forming a fluid seal between the valve body and the seats, wherein in an open position of the valve the second flow passage is in fluid communication with the first flow passage and in a closed position of the valve the plug closes the first flow passage to flow, and wherein the stem co-acts with the plug such that rotation of the stem simultaneously rotates the plug and moves the plug in an axial direction substantially perpendicular to the longitudinal axis of the first flow passage.

12. The plug valve of claim 11, wherein the stem includes an end engaging a slot defined in the plug permitting movement of the plug relative to the stem in a direction substantially perpendicular to the longitudinal axis of the stem.

13. The plug valve of claim 11, wherein the valve body further includes a first valve body member connected to a second valve body member, the first valve body member having the stem extending therethrough and defining a first recess adjacent the second valve body member, the second valve body member defining an opening connected to the first flow passage and having the plug partially received therein, wherein the first valve body member is connected to the second valve body member such that a cavity is formed between the first recess and the plug, and wherein the stem includes a threaded portion received within the cavity.

14. The plug valve of claim 13, further including a mounting nut positioned in the cavity, wherein the threaded portion of the stem engages internal threads of the mounting nut.

15. The plug valve of claim 14, wherein the first valve body member is connected to the second valve body member such that the mounting nut is nonrotatably held in the cavity.

16. The plug valve of claim 13, wherein the first valve body member defines a second recess having an O-ring positioned therein providing a fluid seal between the first valve body member and the stem.

17. The plug valve of claim 11, wherein the first flow passage includes an inlet port and an outlet port, the inlet port and the outlet port each having internal threads.

18. The plug valve of claim 11, wherein the first flow passage includes an inlet port and an outlet port, and wherein a flange is provided around the inlet port and the outlet port.

19. The plug valve of claim 13, wherein the first valve body member is welded to the second valve body member.

20. A plug valve, comprising:
a valve body defining a first flow passage having a longitudinal axis;
a tapered plug defining a second flow passage and extending into the first flow passage, the tapered plug defining a slot;
an elongated stem positioned in the valve body and having an end in engagement with the slot, the stem having a longitudinal axis;
a seat engaging each of the opposed sides of the plug, each of the seats supported in the first flow passage; and an O-ring located between each of the seats and the valve body continuously biasing the seats into engagement with the opposed sides of the plug and forming a fluid seal between the valve body and the seats, wherein in an open position of the valve the second flow passage is in fluid communication with the first flow passage and in a closed position of the valve the plug closes the first flow passage to flow, wherein the stem co-acts with the plug such that rotation of the stem simultaneously rotates the plug and moves the plug in an axial direction substantially perpendicular to the longitudinal axis of the first flow passage, and wherein the stem co-acts with the plug to permit movement of the plug relative to the stem in a direction substantially perpendicular to the longitudinal axis of the stem.