Patent Application
20150008351
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1. Field of the Invention
This invention relates generally to large industrial valves for controlling the flow of fluids therethrough. More particularly, this invention pertains particularly to the trunnions that pivotally support valve plugs relative to the valve housings in which they are mounted.
2. General Background
Industrial valves of the type used in water or sewage treatment plants, as well as in other industries, preferably must remain fully operational for appreciably long periods of time. Additionally, it is preferable for such valves to be serviceable in situ.
Various styles of industrial valves include butterfly valves, sleeve valves, and ball valves. Some types of valves, such as butterfly valves and ball valves, comprise a pivotal plug/gate. Pivotal plugs are typically supported by the housing of the valve via a pair of coaxial trunnions that extend from opposite sides of the plug. One of the trunnions typically also serves as the drive shaft that is rotationally driven to control the rotational position of the plug within the housing and to thereby control the fluid flow through the valve. Valve housings typically comprise bushings for pivotally supporting the trunnions and some form of seals for preventing fluid from leaking through the housing around the trunnions.
It is preferable to configure the bearings of industrial valves such that the maximum bearing pressure will not exceed approximately 2000 psi (13.8 MPa). Unfortunately, this relatively low pressure requires rather large bearing diameters, and therefore large diameter trunnions. As a result, the trunnion diameters tend to be much larger than is needed to handle the driving torque for adjusting the valve. Larger trunnions result in larger valve housings, greater weight, and greater material costs.
The present invention is directed to ball valves having trunnions that comprise shaft portions and larger diameter bearing portions. The larger bearing portions ensure that bearing pressures will be low. Smaller shaft portions reduce material costs and minimize the overall size of the valves. Preferably the bearing portions are formed out of a different material than are the shaft portions. This allows the bearing portions to be formed out of a lower strength (and therefore lower cost) material. Conversely, it also allows the shaft portions to be formed out of a higher strength material to thereby minimize the size of the trunnion shafts without impacting the bearing size and cost. Additionally, each bearing portion is preferably a cylindrical sleeve and is preferably heat-shrunk around part of the shaft portion.
In one aspect of the invention, a ball valve comprises a valve housing and a ball plug. The valve housing comprises an inner cavity. The ball plug is positioned within the inner cavity and comprises a main body portion and a pair of trunnions. The trunnions are fixed to the main body of the ball plug so as to pivot therewith and pivotally connect the ball plug to the valve housing. Each of the trunnions comprises a bearing portion and shaft portion. Each of the bearing portions encircles a respective one of the shaft portions and is fixed to said shaft portion via a cylindrical interference fit so as to pivot therewith.
Another aspect of the invention pertains to a method of assembling a ball valve having a ball plug and valve housing. The method comprises assembling a trunnion and attaching the ball plug to the valve housing via the trunnion. The trunnion comprises a cylindrical shaft portion and a bearing sleeve portion. The bearing sleeve portion comprises an annular bearing surface and a cylindrical opening. The annular bearing surface and the cylindrical opening are coaxial. The cylindrical opening has a first diameter and the shaft portion has a second diameter. The first diameter is less than the second diameter when the cylindrical shaft portion and the bearing sleeve portions are at equal temperatures. The assembly of the trunnion comprises causing the bearing sleeve portion to have a temperature above that of the shaft portion in a manner such that the first diameter becomes greater than the second diameter, thereafter extending the shaft portion through the cylindrical opening of the bearing sleeve portion while the first diameter is greater than the second diameter, and thereafter allowing the shaft portion and the bearing sleeve portion to reach an equal temperature to thereby form an interference connection between the bearing sleeve portion and the shaft portion. The valve housing comprises a trunnion bearing and the attaching of the ball plug to the valve housing comprises engaging the bearing sleeve portion of the trunnion with the trunnion bearing such that the trunnion and the ball plug are pivotally supported by the trunnion bearing.
Yet another aspect of the invention pertains to a method of assembling a ball valve. The ball valve comprises a ball plug and a valve body. The method comprises attaching a bearing sleeve to a trunnion shaft via an interference fit. The bearing sleeve and the trunnion shaft are configured and adapted to at least partially pivotally attach the ball plug of the ball valve to the valve body. The interference fit between the trunnion shaft and the bearing sleeve rotationally and axially fixes the bearing sleeve to the trunnion shaft.
Further features and advantages of the present invention, as well as the operation of the invention, are described in detail below with reference to the accompanying drawings.
Reference numerals in the written specification and in the drawing figures indicate corresponding items.
A ball valve in accordance with the invention is shown in
The housing 22 comprises a generally cylindrical and tubular valve body 26 that is preferably formed as a monolithic part. The valve body 26 comprises a cavity 28, opposite front and rear fluid openings 30, 32, a plug seal replacement port 34, and a pair of axially aligned trunnion openings 36. The plug seal replacement port 34 preferably extends through the top of the valve body 26 to provide access to the cavity 28. The trunnion openings 36 preferably define a horizontally oriented axis that lies directly beneath the plug seal replacement port 34.
The housing 22 also comprises a plug seal replacement port cover 38, trunnion bearings 40, and front and rear ring-flanges 42, 44, and trunnion seal rings 46. The plug seal replacement port cover 38 is bolted over the plug seal replacement port 34 to close the port during normal operation, but can be removed when access to the cavity 28 of the valve body 26 is desired. The trunnion bearings 40 are bushing-style bearings that are configured to be inserted into the trunnion openings 36 of the valve body 26 and bolted to the valve body from outside the valve body. The trunnion seal rings 46 are bolted to the trunnion bearings 40 and are configured to seal against trunnions to prevent fluid from leaking out of the valve 20 through the trunnion openings 36. The front and rear ring-flanges 42, 44 are aligned with and bolted to the front and rear fluid openings 30, 32, respectively, and provide means for attaching the valve 20 in-line between pipes of a fluid system. Additionally, the front ring-flange 42 comprises a removable annular valve seat 48 that is configured to seal against a valve seat of the ball plug 24 (described below) to prevent fluid from passing through the valve 20 when the ball plug is in the closed position.
The ball plug 24 assembly is shown in an exploded view in
As mentioned above, the trunnions 52 of the ball plug 24 each comprise a cylindrical bearing portion 62 and cylindrical shaft portion 64. Preferably those portions are initially fabricated as separate components, as shown in
Forming cylindrical bearing portions 62 and cylindrical shaft portions 64 of the trunnions 52 as separate parts has additional advantages. The low required bearing pressure discussed above is well below the yield strength of most metals and therefore the cylindrical bearing portions are preferably formed out of relatively low cost metals such as 304 stainless. Conversely, the shaft portions 64 can preferably be formed out of a stronger material, such as 17-4 stainless, which, although more expensive per pound, allows the shaft portions to be formed out of relatively little material (i.e., with a relatively small diameter).
The bearing portions 62 of the trunnions 52 are preferably formed as cylindrical sleeves having an inner diameter that is slightly less than the outer diameter of the shaft portions 64 to thereby create an interference fit between said components when they are joined. Although the bearing portions 62 could be press-fit over the shaft portions 64, the bearing portions are preferably heat shrunk to the shaft portions using any method involving heating the bearing portions and/or cooling the shaft portions. The interference fit locks the bearing portions 62 to the shaft portions 64 and prevents and fluid from passing therebetween.
The ball valve 20 is assembled by inserting the main body portion 50 of the ball plug 24 into the valve body 26 of the housing 22 through either the front or rear fluid openings 30, 32 of the valve body. The trunnions 52 are thereafter inserted through the trunnion openings 36 of the valve body 26 of the housing 22 from outside the valve body, and the ends of the shaft portions 64 of the trunnions are then secured into the trunnion holes 68 of the main body portion 50 of the ball plug 24 via the locking pins 54 and set screws 56. The trunnion bearings 40 of the valve body 26 of the housing 22 are also inserted into the trunnion openings 36 from outside the valve body. The other components are then assembled to the valve 20.
When the valve seat 58 of the ball plug 24 is in need of replacement, it can be replaced via the seal replacement port 34 of the housing 22 (with the ball plug 24 in the open position) without disconnecting the valve 20 from the pipes (not shown) to which the valve is assembled. Similarly, worn trunnion bearings 40 can be replaced by removing the trunnion seals 46 of the housing 22 and thereafter extracting the worn trunnion bearings from outside the housing. It should also be appreciated that, in use, the pressure equalizing through holes 65 of the bearing portions 62 of the trunnions 52 allow fluid pressures on the axially opposite sides of said bearing portions to equalize. This prevents such fluid pressures from exerting side loads on the ball plug 24 relative to the housing 22. Additionally, although the valve 20 is adapted to be driven by only the longer of the trunnions 52, it can, if necessary, be driven by the other of the trunnions.
In view of the foregoing, it should be appreciated that the invention has several advantages over the prior art.
As various modifications could be made in the constructions and methods herein described and illustrated without departing from the scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.
It should also be understood that when introducing elements of the present invention in the claims or in the above description of exemplary embodiments of the invention, the terms “comprising,” “including,” and “having” are intended to be open-ended and mean that there may be additional elements other than the listed elements. Additionally, the term “portion” should be construed as meaning some or all of the item or element that it qualifies. Moreover, use of identifiers such as first, second, and third should not be construed in a manner imposing any relative position or time sequence between limitations. Still further, the order in which the steps of any method claim that follows are presented should not be construed in a manner limiting the order in which such steps must be performed, unless such an order is inherent.
