Ball valve for fluids with seatings comprising laminated rings

Abstract: Ball valve for fluids, with sealing seatings (14,15) comprising rings (16,17), disposed between the spherical surface of the valve and the interior of the valve body, composed of rings formed of superimposed layers (17) of plates of pure graphite alternating with plates (16) of stainless steel sheet, the whole being contained in a casing (18) of metal sheet covering the outer sides of the seating, except that in contact with the spherical sealing surface.

Description: The subject of the present invention is a ball valve for the shutting-off and/or deviation of fluids, including at high temperatures and pressures, of which the sealing seating for the ball is composed of ring seatings, each formed both from particular arrangements of laminated elements and from different materials, variously arranged. As is well known, the valves known as "ball" valves are composed of a valve body having a cylindrical cavity, into which lead two or more ducts connected to the supply of fluids to be distributed or intercepted, according to requirements, and of a ball inside said cylindrical cavity having an axial or cruciform duct and capable of being operated from outside, this ball being situated between the inlet and delivery ducts in such a way as to dispose the axial duct of the ball in alignment with the inlet and delivery ducts or to close one or the other of these ducts, and also to bring into communication with one another the various channels for a specific distribution of the fluid. Ball valves of known type are disclosed into US-A 3 649 035 where sealing seatings formed of superimposed layers of plates of pure graphite or the like alternating with plates of stainless steel or the like are located into a casing covering the outer sides of the seating itself. The problem that arises in said ball valves is concentrated especially in the ring seatings which surround the ball and which must make a seal both between che inlet and outlet ports in boch directions and between both the ports and the control shaft leading to the outside. Said seatings are, moreover, not subject to being compressed between the fixed and movable part, except during initial assembly, for which reason any wear must be avoided which might give rise to play between the parts, which cannoc be taken up. The seatings are also subject both to high temperatures, such as those of saturated and superheated steam, and to high differential pressures, while in these conditions also it must be possible to operate them without the need to apply excessive torque. The valve having the seatings forming the subject of the present invention solves the aforementioned problems, while also permitting classes of use at high temperatures and pressures. The solution of the a.m. problem is given by a ball valve according to claim 1. Each graphite plate, according to this invention, must be composed of graphite having a density of 1.4 to 2 kg/dm³, preferably from 1.6 to 1.8 kg/dm³, obtained by a pressure of 1.4 to 2 bar. Instead of the stainless steel, each reinforcing sheet could be of nickel sheet, also of thickness from 0.07 to 0.01 mm. The aforementioned casing containing said seating may extend over the three sides that are not in contact with the movable part or over only two sides, but in any case with application of a layer of graphite of 0.5 to 1.5 mm thickness, bonded onto the annular surface facing towards the fixed side. The side of the seating that is in contact with the movable part of the valve according to this invention is preferably inclined and rectilinear, so as to have only a single, circular line of contact with the spherical surface of the movable ball. The characteristics of the valve according to this invention will be more apparent from the attached drawings, in which there are shown: in Fig. 1, the valve in the closed position; in Fig. 2, the same valve in the open position and in Figures 3a, b, c, enlarged sections of various seatings. With reference to the figures, the valve is composed of a central body 1 and two flanged connections 2 and 3, disposed coaxially to the body 1 and connected to it by screws or stud bolts 4 and 5. The central body 1 has an internal cylindrical cavity 6 disposed in the axial direction and a cylindrical bore 7 perpendicular to the axis. The flanged connections 2 and 3 each have, inside them, an axial duct 2', 3', such that when said connections are fitted onto the central body 1, the axes of the internal ducts 2' and 3' shall intersect the axis of the cylindrical surface 6 of the central body 1. Inside the cylindrical surface 6 and on the axis of the ducts 2' and 3', is disposed the ball 8 equipped with a through hole 9 which, when the ball is in position inside the cavity 6, is coaxial with and substantially of the same dimensions as the ducts 2' and 3'. The rotation of the ball 8 is effected by means of a shaft 10, which can be operated from outside by a hand lever 11 or by motorized means, referenced generally 12. The drive shaft 10 for the ball 8, housed in the bore 7, is provided with seatings of known ring type or the like 13, disposed along its axis. The seatings 14, 15, of annular type, disposed with their axes coaxial with the ducts 2' and 3' and blocked between the spherical surface of the ball 8 and the flat surfaces of the flanges of the connections 2 and 3, act on the continuous spherical surface of the ball 8. The surface of said seatings 14, 15 in contact with the movable part of the ball is composed of the internal conical part, having a rectilinear generatrix, so as to have the sealing contact between said internal conical surface and the spherical surface of the valve solely along a continuous, circular line. As will be seen in Figure 3, the seating 15, according to section a, is composed of a series of parallel layers 16 of sheet metal, of stainless steel, pure nickel or the like, as discussed above, alternating with parallel layers 17 of pure graphite or the like, the whole contained in a sheet metal casing 18, which surrounds the three outer sides of the seating, while the side in contact with the fixed part is covered by a further layer of graphite 19, disposed on the outer surface of the sheet metal. In Figures 3b and 3c there are illustrated, in section, further solutions of seatings having the same layered composition as the seating indicated at a), but with the outer, containing metal sheet limited on the broader side, see section b), or limited to only the two remaining sides. As can be clearly seen from Figures 1 and 2, the sealing seatings 14, 15 are in contact with the spherical surface of the valve along continuous circular lines, coaxial with the ducts 2' and 3', so that the seal takes place not only between the ducts 2' and 3' but also between these ducts and the space which remains between the cylindrical surface 6 and the spherical surface of the valve. This prevents residues of fluid passing through from being able to penetrate into the casing of the valve and escape to the outside along the operating shaft of said valve. It will be understood that many variants of a constructional type may be applied to the valve described above, while still keeping the arrangement of the sealing seatings on the ball with the characteristics that form the subject of the present invention.

Claims: Ball valve for fluids with sealing seatings (14,15) comprised of rings, the ring seatings, disposed between the spherical surface of the valve and the interior of the valve body, are constituted of rings, characterised in that the ring seatings are formed of superimposed layers of plates of pure graphite (17) alternating with plates of stainless steel (16) sheet, the whole being contained in a sheet metal casing (18) covering the outer sides of the seating, except that side which is in contact with the spherical sealing surface. Ball valve according to Claim 1, characterized in that said ring seating has its sealing surface, for contact with the spherical surface of the valve, shaped as a truncated conical circular cavity having a rectilinear generatrix, the contact between the two parts being obtained along a continuous circular line coaxial with the ball. Valve according to the preceding Claims, characterized in that the outer surface of the ring seatings in contact with the flanges of the coaxial connections is covered with a layer (19) of pure graphite or the like, preferably from 0.5 to 1.5 mm in thickness, disposed on the surface of the seating or on the surface of the covering casing.

Inventors: BONETTI GIULIO, BONETTI, GIULIO
Applicants: BONETTI CESARE SPA, CESARE BONETTI S.P.A.
Application year: 1991
Main classification: F16K5
IPC codes: F16K5