MXPA98001124A - Low noise sphere valve assembly with current air sheet insert ab - Google Patents

Abstract

The present invention relates to a valve assembly for controlling the flow of fluid through a conduit, the valve assembly comprising a ball valve disposed in the conduit and having a transverse bore formed therein to receive the fluid, and an insert disposed therein. in the downstream duct of the ball valve and defining a plurality of small flow passages and at least one large flow passage, the valve being able to rotate in the duct to direct the fluid from its drilling through one or more flow passages, a portion of the insert forming an air sheet surface to prevent fluid separation as it passes through the relatively large flow passage

Description

LOW NOISE SPHERE VALVE ASSEMBLY WITH CURRENT DOWN AIR SHEET INSERT BACKGROUND OF THE INVENTION The present invention relates to a low noise ball valve assembly and, more particularly, to such an assembly for controlling the transmission and distribution of a compressible fluid. In the transmission and distribution of compressible fluids, such as natural gas, there are requirements for valves that control a variable, such as pressure or flow rate, and operate at high pressure drops, that is, high differences in pressure between the pressure upstream and downstream. As such, these valves are equipped with actuators and setters that respond to a control signal generated by a controller or computer. When a compressible fluid is throttled through a control valve at a high pressure drop, noise is generated in the fluid in an aerodynamic form, and subsequently it propagates through the fluid, exciting the walls of the tube (mainly downstream), and thereby causing the noise to propagate to the surrounding atmosphere. The result can be noise that exceeds the permissible limits for the conservation of the worker's hearing.

A second concern involved with the throttling of a compressible fluid through a control valve is that it often causes excessive mechanical vibration, resulting in problems consequent to the proper operation of the associated measurement and control equipment. In addition, vibration can also cause fatigue failure of welds or pipe. Frequently, ball valves are used as shut-off valves and control valves for special applications, such as the transmission and distribution of natural gas. In order to reduce noise and mechanical vibration when ball valves are used, inserts have been placed in the ball valves which are provided with a plurality of relatively small diameter passages through which the fluid passes under certain conditions of flow. However, the availability of inserts for ball valves that offer a considerable reduction in noise and mechanical vibration has been very limited. Likewise, ball valves of the above type are often limited to applications in which there is a high pressure drop across the entire travel range of the valve. In these cases, the valves are designed for the continuous reduction of noise and mechanical vibration throughout the range of displacement. However, there are applications involving a relatively high pressure drop at relatively low flow rates and small valve openings, and a relatively low pressure drop at maximum flow and relatively large valve openings. In the latter case of low pressure drop, a flow capacity is required that is greater than what would be possible using a valve designed for continuous noise reduction based on a high pressure drop across the entire travel range. The valve. Likewise, ball valves that have inserts of the above type that are welded, or otherwise bonded, into a ball valve, are difficult to manufacture and often cause distortion of the ball valve. In addition, ball valves that have inserts of the above type can cause gas flow to separate as it passes through the valve, resulting in losses in a pressure drop that compromises the performance of the valve. Therefore, what is needed is a ball valve that can reduce noise at relatively low flow rates and small valve openings at relatively high pressure drops, but which can respond to relatively low pressure drop situations and achieve maximum flow. Likewise, a ball valve of the previous type that reduces mechanical vibration is needed, that is relatively easy to manufacture, and that is not easily subject to distortions. In addition, a ball valve of the above type is necessary, to eliminate the separation of gas flow when passing through the valve. SUMMARY OF THE INVENTION The present invention, accordingly, provides a ball valve assembly for controlling the flow of fluid through a conduit in which a ball valve is provided and provided with a transverse perforation to receive the fluid. An insert is also provided in the downstream conduit of the ball valve and defines a plurality of relatively small flow passages and a relatively large flow passage. The valve is capable of rotating in the conduit to direct the fluid from its perforation through one or more of the flow passages, and a portion of the insert forms an air sheet surface to prevent separation of the fluid as it passes through. of the relatively large flow passage. A cavity is provided between some of the small flow passages to allow pressure reduction in two stages and thus reduction of increased noise. Major advantages are achieved with the ball valve assembly of the present invention as the noise and mechanical vibrations generated by the fluid flow are considerably reduced to small valve openings and low flow rates, while maximum flow can be achieved when the fall of pressure is relatively low. Also, the ball valve assembly of the present invention is relatively easy to manufacture, reduces distortion of the ball valve, and includes an air blade surface that eliminates fluid separation. BRIEF DESCRIPTION OF THE DRAWINGS Figures 1, 3 and 4 are cross-sectional views that sketch the ball valve assembly of the present invention in three modes of operation. Figure 2 is an isometric view of the ball valve assembly of Figures 1, 3 and 4. Description of the Preferred Embodiment Form Figure 1 of the drawings outlines an embodiment of the ball valve assembly of the present invention , which includes a ball valve 10 disposed in a valve body 12 formed by a cylindrical inlet section 14. An inlet bore 14a extends through the inlet section 14 and a circular flange 14b is provided in the wall external in the inlet section for connection to an inlet pipe (not shown) for supplying a compressible fluid, such as natural gas, to the inlet section. A cylindrical outlet section 16 is also provided, which has an outlet bore 16a and a circular flange 16b formed on its external wall for connection to an outlet pipe (not shown) to receive the fluid from the outlet section. An external support ring 20 extends between the sections 14 and 16, with the inner surface of the ring in a spaced relationship with the outer surface of the ball valve 10. The support ring 20 is connected between the sections 14 and 16 in any known shape, such as by means of bolts, or the like (not shown). A pair of axially spaced seal assemblies 22 and 24 are mounted in circular notches or grooves, provided in the inner end portions of the inlet section 14 and the outlet section 16, respectively. The support ring 20 and the seal assemblies 22 and 24 will not be described in any further detail as they do not form part of the present invention. The valve 10 is in the shape of a ball, or sphere, having a transverse central bore 10a. In this manner, two solid portions 10b and 10c are defined, each having a convex outer surface. In the closed position of the valve 10 shown in Figure 1, the solid portion 10b blocks the flow of fluid from the inlet section 14 to the outlet section 16. A pair of rods, one of which is shown in phantom lines and referenced with the reference number 28, are connected to the outer surface of the ball valve 10 in their diametrically opposed portions to allow the ball valve to be rotated in a manner that is will describe. The rods 28 are connected to conventional auxiliary equipment (not shown) that rotates the rods, and therefore the ball valve 10, about an axis that coincides with the axes of the rods, with the seals 22 and 24 functioning to provide a seal of fluids, all in a conventional way. According to a main aspect of the present invention, an insert 30 is provided in the outlet bore 16a of the inlet section 16 just downstream of the ball valve 10, and is designed to reduce the noise and mechanical vibrations generated as a result of fluid flow through the ball valve. As shown in Figures 1 and 2, the insert 30 is in the form of a plate-shaped member having a relatively small leg portion 30a, a relatively large leg portion 30b, and an elbow portion of enlarged width 30c connecting the leg portions 30a and 30b. The leg portion 30a extends from the elbow portion 30c substantially perpendicular to the axis of the perforation 10a, and the leg portion 30b extends from the elbow 30c, curves back to the rear end, or outflow, the outlet perforation 16a, and is configured so as to form a curved, smooth "air sheet" design. The respective distal ends of the leg portions 30a and 30b rest against corresponding inner surface portions of that portion of the outlet section 16 that define the outlet bore 16a so as to define an enclosed cavity 34. The outer surface of the portion of leg 30a is concave, with its curvature corresponding to the convex external surface of the portion 10c of the ball valve 10.

A series of rows of parallel, spaced passages is formed through the insert 30, the passages 38 of each row (Figure 2) extending in a spaced, parallel relationship. The passages 38 receive the fluid from the ball valve 10 under conditions to be described, and the diameter of each passage 38 is considerably smaller than the diameter of the conduit 16a. As a result, the passages work to greatly reduce the level of noise that would otherwise be generated by the fluid flow through the assembly according to well-established thes, as explained above. The passages 38 extending through the leg portion 30a of the insert 30 extend from the ball valve 10 to the cavity 34, and the passages extending through the leg portion 30c extend from the cavity 34. to the exit perforation 16a. This allows pressure reduction in two stages and an increase in noise reduction, as will be described. The passages 38 in the lower row, as seen in Figure 1, extend from the ball valve 10 directly to the outlet bore 16a. The insert 30 occupies a portion of the cross section of the outlet bore 16a, the remaining portion of the latter bore forming a relatively large diameter flow passage for the fluid, under conditions to be described. When the ball valve 10 is in its closed position shown in Figure 1, the concave outer surface of the leg portion 30a receives a corresponding portion of the convex valve portion 10c. In this closed position, the solid portion 10b blocks the flow of fluid from the inlet bore 14a through the valve 10. In the case that fluid flow is desired, the valve is rotated by rotating the valve rods 28 in a clockwise direction, as shown by the arrow in Figure 1, until the inlet end of the bore 10a is exposed to the bore 14a as shown , for example, in figure 3. This movement also exposes one or more of the passages 38 of the insert 30 to the exit end of the perforation 10a, the number of passages exposed depending on the degree of rotation of the ball valve 10. Assuming that the valve 10 is moved to the position of Figure 3, in which all the passages 38 are exposed and the outlet bore 16a is blocked otherwise, the fluid flows from the inlet bore 14a, towards and through the exposed perforation 10a of the ball valve 10, and to the exposed passages 38. That portion of the fluid passing through the passages 38 in the leg portion 30a of the insert 30 enters the cavity 34, and passes from the cavity, through the passages 38 in the leg portion 30b, and to the exit perforation 16a. This achieves two-stage pressure reduction and increased noise reduction, according to well-known principles. The remaining portion of the fluid passes through the lower row of passages directly to the outlet bore 16a. The fluid leaves the outlet bore 16a and passes to the aforementioned outlet pipe connected to the outlet section 16. In case full flow is desired, the ball valve 10 is rotated further in the direction in the direction clockwise, until it reaches the fully open position shown in Figure 4. In this position, all the passages 38 in the insert 30, as well as the portion of the exit perforation 16a not occupied by the insert, are exposed to the fluid in the inlet bore 14a and the bore 10a in the ball valve 10. As this last portion of the outlet bore 16a is much larger in cross section than the cross section of each passage 38, it defines a flow passage which provides the minimum resistance to fluid flow. Therefore, the vast majority of the fluid flows from the inlet drilling 14a, through the bore 10a of the ball valve 10, and through the outlet bore 16a towards the aforementioned outlet tube. During this flow, the fluid is attached to the outer surface of the leg portion 30b of the insert 30 due to the smooth air blade design of the last leg portion, although a smaller portion of the fluid flows through the passages 38 of the Insert It will be understood that the position of the ball valve 10 sketched in Figure 3 is only for example purposes and that the valve can take any intermediate position between the closed position of Figure 1 and the fully open position of Figure 4, depending of the particular fluid flow desired. In this way, according to the present invention, the ball valve assembly and the method of the present invention achieve pressure reduction in two stages, when the ball valve 10 is partially open, as shown by way of example in Figure 3, which increases noise reduction when compared to reduction in a single stage and which produces a high attenuated peak frequency. Also, in the fully open position of Figure 4, relatively high flow capacity (with reduced noise reduction) is achieved, since the vast majority of the fluid flow exceeds the insert 30 as it flows from the perforation 10a to the exit perforation. 16a. The assembly of the present invention, in this way, is especially suitable for applications in which a relatively high pressure drop occurs at a relatively low opening of the ball valve 10, and the pressure drop is reduced to a relatively low value as the valve opening increases. In this way, the assembly of the present invention is operable in a relatively wide range of pressure drops and flow rates. Also, the mechanical vibrations generated by the fluid flow are considerably reduced to relatively small valve openings and low flow rates. In addition, as a result of the fact that the insert 30 is located downstream of the ball valve 10, the assembly of the present invention is relatively easy to manufacture and minimizes the distortion of the ball valve. Still further, due to the smooth "air sheet" design of the leg portion 30b of the insert 30, the fluid is attached to the outer portion of the last leg portion as it passes through the outlet bore 16a, thus allowing a significant recovery of pressure. It will be understood that variations may be made in the foregoing without departing from the scope of the invention. For example, the present invention is not limited to the number and specific arrangement of the passages 38 in the insert 30. For example, the passages 38 in the leg portion 30b may have diameters larger than the diameters of the passages in the portion of leg 30a (and / or 30c). Other changes, modifications and substitutions are intended in the above disclosure and in some cases some characteristics of the invention will be employed without corresponding use of other features. Accordingly, it is appropriate that the appended claims be interpreted broadly and in a manner consistent with the scope of the invention.

Claims (14)

1. CLAIMS 1. A valve assembly for controlling the flow of fluid through a conduit, the valve assembly comprising a ball valve disposed in the conduit and having a transverse perforation there formed to receive the fluid; and an insert disposed in the downstream conduit of the ball valve and defining a plurality of small flow passages and at least one large flow passage, the valve being able to rotate in the conduit to direct the fluid from its bore through of one or more flow passages, a portion of the insert forming an air sheet surface to prevent separation of the fluid as it passes through the relatively large flow passage. The assembly of claim 1, wherein the valve directs the fluid through one or more relatively small flow passages or through the relatively small flow passages and the large flow passage. The assembly of claim 1, wherein the flow of fluid through the relatively small flow passages reduces the flow velocity and the noise generated by the fluid flow, and the fluid flow through the passage of relatively diameter large increases the flow velocity. The valve assembly of claim 1, wherein the relatively small flow passages are formed through the insert; and where the insert, and that portion of the conduct not occupied by the insert, form the relatively large flow passage. The assembly of claim 4, wherein the insert defines with the corresponding surface defining the passage a cavity, so that a portion of the fluid flows from some of the passages of the insert into the cavity, and through other passages in the passageway. the insert, to achieve pressure reduction in two stages. The assembly of claim 1, wherein, upon rotation of the ball valve from its open position to its closed position, the valve directs the fluid through the relatively small flow passages before the relatively large flow passage. The assembly of claim 1, wherein, in the fully open position of the valve, the fluid flows through the relatively small flow passages and the relatively large flow passage. 8. A method of controlling the flow of fluid through a conduit, comprising the steps of providing a sphere valve in the conduit having a transverse perforation therein formed to receive the fluid, defining a plurality of relatively small flow passages and at least one relatively large flow passage in the downstream conduit of the ball valve, rotating the valve to direct the fluid from its perforation through one or more of the flow passages, and prevent fluid separation during passage through the relatively large flow passage. The method of claim 8, wherein the fluid is directed through one or more of the relatively small flow passages or through the small flow passages and the large flow passage. The method of claim 8, wherein the flow of fluid through the relatively small flow passages reduces the flow velocity and noise generated by the fluid flow, and the flow of fluid through the passage of relatively large diameter. large increases the flow velocity. The method of claim 8, further comprising the step of directing the fluid through some of the passages, into a cavity, and through the other passages to achieve pressure reduction in two stages. The method of claim 8, wherein, during the step of rotating, the valve directs the fluid through the relatively small flow passages before the relatively large flow passage. The method of claim 8, wherein, in the fully open position of the valve, the fluid flows through the relatively small passages and the relatively large flow passage. The method of claim 8, wherein the step of preventing comprises providing an air sheet surface in the conduit downstream of the ball valve.