Control valve

Abstract: A control valve, which consists of a body (1) provided with flow-through channels (2, 3) and of a closing member (5) arranged rotatably in the body in an expansion (4) of the channel, the rotation shaft of which is eccentric in relation to the sealing surfaces of the closing member and the seal of the body. In an open position of the valve a circular flow is formed around the closing member between a wall of the body and the closing member (5), the main flow passage of which circular flow is located in a channel between the inner surface of the body and the upstream edge (16) of the closing member. The closing member (5) has an extension (17) in its upstream edge (16) in the open position, which extension in an initial phase of the opening reduces the cross-sectional area of the main flow passage.

Description: This invention relates to a control valve, which comprises a body provided with flow-through channels and a closing member, which is arranged rotatably in the body in an expansion of a flow-through channel, the rotation shaft of which closing member is eccentric in relation to the sealing surfaces of the closing member and the seal of the body, whereby in an open position of the valve a circular divided flow is formed around the closing member with one flow passage being on the side of the closing surface of the closing member and the other, main flow passage being formed on the side of the closing member adjacent the rotation shaft between an inner surface of the valve body and an upstream edge of the closing member. A valve similar to such as described is disclosed in GB-A-2000574. The present rotary plug valves have a poor characteristic curve (i.e. the flow volume of the medium in relation to the angle of opening) regarding adjustability, because the increase of the effective flow cross-sectional area of the main flow passage as a function of the opening is not affected. In addition to this, rotary plug valves at the market have poor cavitation properties. In order to throttle the medium flow flowing through the valve and to reduce noise and cavitation, it is known to use different kinds of perforated baffle plates attached in the closing member. This kind of construction in e.g. a closing member in form of a spheric calotte is described in e.g. FI-patent publication 70744 (see corresponding EP-A-0043193 R. Bey). EP-A-0376502 is concerned with changing the characteristic curve of a valve wherein the shape of the forward edge (8) of the closing face of the closing member or of the flow duct (11) in the closing member differs from the shape of the rearward edge (9), and both edges (8,9) of the closing face (7) of the closing member (3) of the flow duct (11) in the closing member are shaped in accordance with the desired different characteristic curves and/or maximum capacities, and wherein, in order to change the characteristic curve and/or the maximum capacity, either one of the directions of rotation may be chosen as the direction of opening of the valve. The closure member (3) is in continuous contact with the seal in the valve body and thus no significant flow passes between the housing (1) and the tightening surface of the closure member (3). The V-shape of the forward edge (8) influences the characteristic curve of the valve. The objective of the present invention is to improve the flow properties of the valve in a manner simpler and more effective than used before. Characteristic to the valve according to the invention as defined by claim 1 is that the closing member has an extension or protrusion at its upstream edge in the open position, which extension or protrusion in an initial phase of the opening procedure of the valve reduces the cross-sectional area of the main flow passage of the closing member. The closing member of the valve can be a rotary plug, an eccentric sphere segment or a crosscut of a segment or an eccentric cylinder or cone plug segment or a crosscut of a segment. The inner surface of the body is shaped so that the flow cross-section between the inner surface of the body and the closing member changes as a function of the opening in a desired manner. The extension in the edge of the closing member may be toothed so that the jet is divided in several smaller jets, whereby the intensity of the jets decreases. This reduces noise and cavitation. The forming of the main flow passage is preferably carried out so, that the total flow cross-sectional area follows the equation below: whereby N₁ = quality modification coefficient µ = correction coefficient, which takes constriction of the flow in flow opening into consideration h = relative aperture of the valve Cv f = capacity coefficient of a fully open valve A p = flow cross-sectional area of incoming side DP f = characteristic coefficient of the process pipework When the change in flow cross-sectional area in relation to the relative opening follows this formula, adjustability of the valve in the whole range of the opening thus improves, i.e. the whole opening is used for adjusting. With help of the formula it is found, how the flow cross-sectional area is to be changed as a function of the opening, in order for amplification of the valve installed to be constant. There is thus a linear connection between the volume flow flowing through the valve installed in the pipework and the opening of the valve, when pressure loss in the pipework is taken into consideration. The special shaping of the closing member and the body of the valve according to the invention does not cause any extra expenses, because it can be carried out by casting. The invention and its details will be described in more detail in the following with reference to the accompanying drawings, whereby: Fig. 1 shows a valve according to the invention cut in a plane perpendicular to the rotation shaft, Fig. 2 shows a section A-A of Fig. 1, Fig. 3 shows a member device of the valve alone, seen from the closing surface side and Fig. 4 shows the closing member seen in the direction of the rotation shaft. In the valve there is a body 1, in which there is a first flow-through channel 2 and a second flow-through channel 3. The flow direction is indicated by the arrow B. In the embodiment shown in the drawings, as a closing member arranged in the expansion 4 of the flow-through channel there is a sphere segment or calotte 5, to which a rotation shaft 6 extending through the body is connected. There is a closing seal 7 between the body and the closing member. The flow normally comes from the side of the seal 7 and meets the circular throttling area, which is adjusted by changing the opening angle of the closing member 5. The rotation shaft 6 is located eccentrically in relation to the centre line 8 of the flow-through channels 2 and 3 in a manner, that the distance of the rotation shaft from the body half 9, which is located on the other side of the plane passing via the centre line 8 and parallel to the rotation shaft 6, is bigger than from the sealing surface 10 of the seal 7. In a closed position the closing member 5 settles against the sealing surface 10 of the seal 7, whereas in an open position the closing surface 11 of the closing member stays at a distance from the above mentioned body half 9. In an open position there is thus formed a circular flow passage around the closing member on the side of the closing surface 11 of the closing member and on the side of the rotation shaft 6. In that edge 16 of the closing member 5, which comes behind when opening the valve, i.e. stays on the upstream side in an open position, there is an extension or a protrusion 17. There are comb-shaped cuts 18 in the edge of the extension. Purpose of the comb-shaped extension is in an initial phase of the opening to reduce the cross-sectional area of the flow passage on side of the rotation shaft. There are grooves 14 and between them ridges 15 in the extension 17. Direction of the grooves 14 is such, that in an open position they are transverse in relation to the flow direction thus forming sequential extension and throttling areas in the flow passage on the side of the body half 9. In the closing surface 11 of the closing member 5 there are grooves 14' similar to the grooves 14 in the extension. In an open position of the valve the pressure of flow medium creates a dynamic moment having influence on the closing member. Magnitude of this moment in the valve according to the invention can be influenced by the shaping of the outer surface of the extension 17 of the closing member. By changing the direction C of the outer surface of the extension 17 in the closing member in a plane perpendicular to the rotation shaft 6, the direction of the arm of the force F mom , which creates the moment, changes and thus the magnitude of the moment changes as well (Fig. 4). Thus when producing the valve, a suitable direction of the outer surface of the extension can be chosen and thus the moment can be affected. The invention is not limited only to the embodiment described above, but it can vary in different ways within the limits of the claims. The closing member can be not only a sphere segment or a cut of the segment, but also a cylinder or cone segment or a cut of the segment. The flow passage on side of the closing surface of the closing member can be created not only by means a rotation shaft located eccentrically as described above, but also by a suitable shaping of the inner surface of the expansion 4 in the body. Grooves 14' in the closing member are not necessarily needed. Also grooves 14 in the extension 17 can be omitted. The cut or cuts 18 in the extension can also be replaced by perforation or omitted. Instead of grooves and ridges also other kinds of recesses and protrusions can be used in order to create expansion and throttling areas.

Claims: A control valve, which comprises a body (1) provided with flow-through channels (2,3) and a closing member (5), which is arranged rotatably in the body in an expansion (4) of a flow-through channel, the rotation shaft of which closing member is eccentric in relation to the sealing surfaces of the closing member and the seal (7) between the body (1) and the closing member (5), whereby in an open position of the valve a circular divided flow is formed around the closing member (5) with one flow passage being on the side of the closing surface (11) of the closing member (5) and the other, main flow passage being formed on the side of the closing member adjacent the rotation shaft (6) between an inner surface of the valve body (1) and an upstream edge (16) of the closing member (5), characterized in that the closing member (5) has an extension or protrusion (17) at the upstream edge (16) of the closing member (5) relative to the normal direction of flow in the open position, which extension or protrusion in an initial phase of the opening of the valve reduces the cross-sectional area of the main flow passage. A control valve as in Claim 1, characterized in that the outer edged of the extension (17) extending to the flow passage in an initial phase of the opening has a cut or cuts (18). A control valve as in Claim 1 or 2, characterized in that there is one or several grooves (14) and ridges (15) in the outer surface of the extension (17) of the closing member, which grooves and ridges in an open position form sequential extensions and throttling areas in the flow passage. A control valve as in Claims 1-3, characterized in that by the shaping or the direction (C) of the extension (17) surface facing the flow, a dynamic moment caused by pressure distribution F mom on the surface of the closing member (5) is reduced. A control valve as in claims 1-4, characterized in that there are sequential expansion or throttling areas in the outer surface of the closing member (5) formed by one or several recesses and protrustions, e.g. by grooves (14') and ridges (15'). A control valve as in claim 5, characterized in that the grooves (14') and ridges (15') of the closing member (5) are located in a closed position of the closing member in the outer surface (11) facing the flow in an area, which in a closed position stays inside of the sealing circle (10) between the closing member and the body, and in an open position form sequential expansions and throttling areas in the flow passage, and that the height of the closing member ridge (15') does not exceed the height of the outer surface of the corresponding closing member with smooth surface. A control valve as in any of the claims 1-6, characterized in that the flow cross-sectional area changes as a function of an aperture according to the following formula: whereby N₁ = quality modification coefficient µ = correction coefficient, which takes constriction of the flow in flow opening into consideration h = relative aperture of the valve Cv f = capacity coefficient of the fully open valve A p = flow cross-sectional area of incoming side DP f = characteristic coefficient of the process pipework.

Inventors: PYOETSIAE JOUNI, ROHWEDER REIMER, PYOETSIAE, JOUNI, ROHWEDER, REIMER, Pyötsiä, Jouni
Applicants: NELES JAMESBURY OY, NELES-JAMESBURY OY
Application year: 1991
Main classification: F16K1
IPC codes: F16K5, F16K3, F16K47, F16K1, F16K25