1. Field of the Invention
The present invention relates generally to ball valves, and more particularly, but not by way of limitation, to an improved bearing retainer and method of assembly for a trunnion ball valve.
2. Brief Description of Related Art
In the typical construction of a trunnion mounted ball valve, the ball is machined to provide “trunnions” that are mounted in bearings. The bearing-trunnion combination is intended to support the ball in a stationary position relative to the flow path, but allow rotation of the ball between an open position and a closed position. The ball engages a pair of seats to form a seal around the ball. The valve is sealed as a result of the upstream valve seat moving against the ball in response to the line pressure. This is in contrast to a floating ball valve where the ball moves along the flow path and seals against the downstream valve seat as a result of the pressure applied to the ball.
A variety of designs for trunnion type valves exist. Notable design differences include the manner in which an operating stem, used for rotating the ball, is assembled and retained. The stem can be inserted internally from within the body cavity. This is known as a “blow-out-proof” design because the stem cannot be removed without disassembling the valve. Another option is to assemble the stem externally and retain it with bolted glands or pins. Another notable difference is that the trunnions can be assembled internally or externally. When assembled externally they are commonly retained with bolted glands. Alternatively, the trunnions can be machined directly on the ball. The ball-trunnion combination can then be inserted internally along with a bearing retainer.
In designing a trunnion valve, the overall length is determined by industry accepted standards. Therefore, the body section of the valve is the only area that is subject to original design. To produce a valve which can compete economically in the market requires a design that minimizes the overall body size and total weight of materials used to produce the valve body.
The different types of valve construction noted above are the result of trading one feature to gain another with the usual result of a less than optimal design. For example, the “blow-out-proof” stem design is generally considered preferable because it cannot be accidentally removed under pressure. Its simplicity also makes it less expensive to produce when compared with all the extra pieces needed to retain an externally mounted stem. Unfortunately, the “blow-proof” stem is not often used because it requires the overall diameter of the valve body to be increased to allow enough room for the ball to be assembled with the stem protruding into the bore. The result of an increase in total weight negates any design savings because the body material is more expensive than the cost of the eliminated parts. The choice of trunnion design also has important tradeoffs. The external pins, bearings, and means of retention are expensive to produce but require a much smaller overall valve body diameter. Internal bearing retainers are simpler and less expensive to produce but generally require a considerable gap between the ball and the body. As a result, a much larger overall body diameter is needed.
A bearing retainer is used to retain a bearing through which the trunnion extends. The bearing retainer is also known as a “trunnion support” or a “trunnion block.” Some designs have modified the internal bearing retainer in an effort to minimize the necessary gap. For example, the bearing retainer can be provided with longitudinal edges that are shaped to better conform to the contour of the ball cavity of the body section. This reduces the gap considerably if an externally loaded stem is used. With an internally loaded stem design, the upper bearing retainer may be slotted on one side to permit the bearing retainer to be moved past the lower end of the stem during assembly of the ball and bearing retainer. However, a slotted bearing retainer reduces the bearing support area of the bearing retainer along the direction of the fluid flow. In turn, a larger bearing retainer and thus a larger valve body is often required to provide sufficient bearing support, thereby obviating the purpose of the slotted bearing retainer.
To this end, a need exists for an improved bearing retainer and method of assembly which permits a particularly small gap between the body and the ball while maintaining internal trunnions in a “blow-out-proof” stem and without sacrificing bearing load strength. It is to such an improved bearing retainer and method that the present invention is directed.
Referring now to the drawings, and more particularly to
The body assembly 12, as shown in
The body assembly 12 has a centrally disposed valve chamber 28, and an inlet passage 30 and an outlet passage 32 in communication with the valve chamber 28 to form a flow passageway through the body assembly 12 about a longitudinal flow axis 34. A first seat pocket 36 is formed about the inlet passage 30, and a second seat pocket 38 is formed about the outlet passage 32. The first seat pocket 36 is adapted to receive the seat assembly 18, and the second seat pocket 38 is adapted to receive the seat assembly 20.
The stem 16 extends through a stem bore 40 formed through the wall of the body 22. The stem 16 has a lower portion 44 with an enlarged diameter. The lower portion 44 is adapted to be received in a corresponding enlarged diameter portion 46 of the stem bore 40. The stem 16 is known as an “internally mounted” or “blow-out proof” stem. The stem 16 is mounted within the stem bore 40 in a manner well known in the art for rotation about a trunnion axis 48. A key 50 (shown in FIGS. 1 and 5–7) is formed on the lower end of the stem 16. The key 50 extends diametrically across the end of the stem 16 and is adapted to matingly engage with the valve member 14.
The valve member 14 is mounted within the valve chamber 28 for rotation about the trunnion axis 48 between the opened position and the closed position wherein the valve member 14 is rotated substantially 90 degrees from the opened position to the closed position. The valve member 14 has a central bore 52 which aligns with the inlet passage 30 and the outlet passage 32 to permit the passage of fluid through the valve 10 when the valve member 14 is in the open position thereof. In the closed position of the valve member 14, the seat assemblies 18 and 20 engage the exterior surface of the valve member 14 and internal surfaces of the body assembly 12 to form fluid tight seals which disrupt fluid communication between the inlet passage 30 and the outlet passage 32.
The valve member 14 has the general form of a spherical ball with the central bore 52 formed therethrough extending circumaxially about a diameter thereof. Portions of the valve member 14 are cut away to form a circular first trunnion 54 and a circular second trunnion 56 which is diametrically opposed to the first trunnion 54 and coaxial therewith. A central slot 58 is formed in the distal end of the first trunnion 54 and, for reasons to be discussed below, is preferably oriented along a line parallel to the plane defined by the axis of the central bore 52 and the common axis of the first trunnion 54 and the second trunnion 56 when the valve member 14 is in the open position. The slot 58 is sized to receive the key 50 of the stem 16 so that the valve member 14 can be rotated about the trunnion axis 48 via rotation of the stem 16.
A first trunnion bushing or bearing 60 is mounted on the first trunnion 54, and a second trunnion bushing or bearing 62 is similarly mounted on the second trunnion 56. A bearing retainer 64 is positioned about the first bearing 60 and extends longitudinally across the valve chamber 28 to engage opposing surfaces of the body assembly 12 so as to longitudinally support the first trunnion 54 of the valve member 14 within the valve chamber 28. The bearing retainer 64 includes a retainer body 65 and a pair of spacers 66a and 66b. The bearing retainer 64 is configured to allow for a small gap between the body 22 and the valve member 14 while permitting the use of an internally mounted stem without sacrificing bearing load strength. A bearing retainer 67 is positioned about the second trunnion bearing 62 and extends across the valve chamber 28 to engage opposing surfaces of the body assembly 12 so as to longitudinally support the second trunnion 56 within the valve chamber 28. The construction of the bearing retainer 67 is similar to that of the bearing retainer 64, except as noted below, in that it is configured to allow for a small gap between the body 22 and the valve member 14. However, it will be appreciated that the bearing retainer 67 may also take the form of any suitable bearing retainer known in the art.
Referring now to
As shown in
While the stem receiving slot 78 permits the retainer body 65 to be received about the key 50 of the stem 16, the formation of the stem receiving slot 78 significantly reduces the bearing support surface along the longitudinal axis of the stem receiving slot 78. The retainer body 65 is positioned in the valve body 22 or (valve chamber 28) with the longitudinal axis of the stem receiving slot 78 oriented in a parallel relationship with respect to the longitudinal flow axis 34. It is appreciated by those of ordinary skill in the art that maximum loads on the retainer body 65 will occur along the line extending parallel to the longitudinal flow axis 34. Therefore, when the retainer body 65 is positioned in the valve chamber 28 with the longitudinal axis of the stem receiving slot 78 oriented in a parallel relationship with respect to the longitudinal flow axis 34, the strength of the retainer body 65 is compromised due to the reduced bearing support surface at the critical point.
To overcome the loss of critical bearing surface area at the stem receiving slot 78, the retainer body 65 has a frusto-conical surface 82 (
As described above, the central slot 58 of the first trunnion 54 is preferably oriented along a line parallel to the plane defined by the axis of the central bore 52 and the common axis of the first trunnion 54 and the second trunnion 56. As show in
As best shown in
Returning to
The retainer body 65 further includes a third end 88 and a fourth end 90. The third and fourth ends 88 and 90 are arc shaped and intersect the frusto-conical surface 82.
It will be appreciated that when the retainer body 65 is formed to have a width from the first planar end 84 to the second planar end 86 that permits engagement of the first planar end 84 with the first end adaptor 24 and engagement of the second planar end 86 with the second end adaptor 26, the area of the first planar end 84 and the second planar end 86 will be a relatively small area. As such, the ultimate load carrying ability of the retainer body 65 is reduced. By decreasing the width between the first planar end 84 and the second planar end 86, the surface area of the first planar end 84 and the surface area of the second planar end 86 are caused to increase to provide a larger surface area to support increased loading. The manner of laterally supporting the retainer body 65 with a reduced width is described below.
Referring again to
Referring now to
In use, the ring spacer 100 positioned in a valve chamber 28a in a concentric relationship with respect to the longitudinal flow axis 34a with the second surface 108 engaged with the body 22a and rotated to a position where the spacer portion 104 is in a non-interfering relationship with rotation of the retainer body 65 between the assembly position and the operating position. After insertion of the retainer body 65 into the valve chamber 28a and rotation of the retainer body 65 to the operating position, the ring spacer 100 is rotated to position the spacer portion 104 between the first planar end 84 of the retainer body 65 and the body 22a. The ring spacer 100 may be rotated with any suitable device. A spacer 66a is positioned between the second planar end 86 of the bearing retainer 65 and the end adapter 26a in a substantially similar manner as described above.
Changes may be made in the combinations, operations and arrangements of the various parts and elements described herein without departing from the spirit and scope of the invention as defined in the following claims.
Number | Name | Date | Kind |
---|---|---|---|
3277919 | Piccardo | Oct 1966 | A |
3497178 | Priese | Feb 1970 | A |
4254793 | Scaramucci | Mar 1981 | A |
4342330 | Wieveg et al. | Aug 1982 | A |
4867414 | Hubacek | Sep 1989 | A |
Number | Date | Country | |
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20050269542 A1 | Dec 2005 | US |