AU8335087A

AU8335087A - Device relating to regulating- and cut-off valves

Info

Publication number: AU8335087A
Application number: AU83350/87A
Authority: AU
Inventors: Folke Hubertson
Original assignee: Somas Ventiler AB
Current assignee: Somas Ventiler AB
Priority date: 1986-12-11
Filing date: 1987-10-21
Publication date: 1988-06-30
Also published as: SE8605309L; SE8605309D0; SE455723B; WO1988004380A1

Description

DEVICE RELATING TO REGULATING- AND CUT-OFF VALVES

TECHNICAL FIELD The invention concerns a device related to control or shut-off valves of the type having a rotatable shut-off member in the form of a ball or of a segment or a sector of a ball, a valve housing with a valve seat in the form of a seat ring, which is lodged to slide in a recess in the valve housing or between the valve housing and a cover plate or a corresponding member integrated with the valve housing, and at the rear of the seat ring, as viewed in the direction from the axis of rotation of the shut-off member, an integrated springing and sealing member provided to press the seat ring against the sealing surface of the shut-off member and to prevent leakage in the region of the seat ring. Two different embodiments of the device of the above mentioned type are described in the Swedish patent specification No. 439 673. One of these embodiments, namely the one which is shown in Fig. 3 in the said patent publication, is today common. According to this known design there is used a ring of a compressed string of graphite as a sealing and springing member. A problem with this design is that the graphite ring is subject to an uneven pressure when the shut-off member is pressed against the valve seat. This implies that the graphite tends to flow away in that direction which is not subject to pressure. Successively a considerable displacement of material will take place. During the shut-off operation therefore a considerably greater torque may be required in order to close the valve than what is normal.

Another problem with the known design is that the graphite is sensitive to steam or gases. Just a very small leakage may be sufficient for the steam or gas in heavy turbulence to tear away parts of the graphite, which successively may cause a complete removal of the graphite locally, so that the raphite ring, and the bushings, respectively, which also are included in this known design, will loose their sealing as well as their springing function. Therefore, members containing asbestos have been used together with graphite. However, for well known medical reasons the use of asbestos is no longer allowed.

it is further conventional to provide a spring washer of acid resistant high grade steel in the recess at the rear of the seat ring between the main portion of the valve housing and the said cover plate in those cases when the seat ring consists of a plastic, comparatively soft material, as for example PTFE or the like. Known spring washers, however, cannot be used as a combined sealing and springing member in those cases when there is used a hard sealing comprising a seat ring of a hard alloy, such as stellite or the like or of a ceramic material. In these cases it is conventional to provide a PTFE-washer behind the seat ring instead of said graphite element, which PTFE-washer is pressed out to seal against the walls of the recess. Further, behind the PTFE-washer one has provided a steel ring which abuts against a number of coil springs provided in borings in the cover plate. The steel washer as well as the coil springs are made of stainless steel. In this case, however, one will face the problem that coil springs must have a high spring constant in order to work satisfactorily. When heated to 300-400°C coil springs will use their springing ability to such a degree that they cannot work properly. This severely reduces the applicability of this design, since designs of rhis type often shall be used for fluids at the said temperatures.

BRIEF DISCLOSURE OF THE INVENTION

It is an object of the invention to solve the above mentioned problems. According to the invention this can be achieved therein that there is used a combined first springing and sealing ring provided in said recess at the rear of the seat ring, said first combined springing and sealing ring having an inner first flange extending substantially parallel to the fluid passage through the valve and terminating with a narrow first edge which sealingly abuts against a first sealing surface on the seat ring, and an outer second flange extending substantially parallel to the first flange but in the opposite direction away from the seat ring towards the bottom of the recess and terminating with a narrow second edge which sealingly abut against a first sealing surface in the bottom of the recess. The cross-section of this first springing and sealing ring preferably has the substantial shape of a Z or an S, and wherein a web portion, connecting the two flanges, is substantially parallel to the plane of the ring, or is inclined at an angle of up to 30° against the ring in unloaded state at the same time as it forms an angle > 90° against the flanges. Preferably the first mentioned angles of inclination should be between 10 and 20° in the unloaded state of the ring.

Further, suitably a second springing and sealing ring, which is of essentially the same type as the first ring but having a smaller cross section, is provided in an annular recess in the seat ring on the opposite side of the seat ring with reference to the location of the said first ring, an inner first flange on said second ring extending substantially parallel to the first flange on the first ring and terminating with a narrow edge which abuts against a circumferential second sealing surface in the recess in the valve housing, and a second outer flange extending substantially parallel to and in the same direction as the said second outer flange on the first ring against a sealing surface in said recess in the seat ring.

The combined sealing and springing rings normally are made of metal, suitably acid resistant spring steel. They can be made by turning, but in principle their shape also can be produced by pressing. The sealing narrow edges can be prepared by honing against their sealing surfaces on the seat ring and on the valve housing, respectively, and/or on the cover plate belonging to the valve housing. It is in principle also conceivable to make the rings, which are characteristic features of the invention, completely or partly of non-metallic materials, for example fibre reinforced composite materials.

Further features, aspects and advantages of the invention will be apparent from the appending claims and from the following description of a preferred embodiment. The device according to the embodiment of the invention concernes a ball segment valve, i.e. a very particular type of ball valve. It should, however, be understood that the principles of the invention can be applied also for other valves of the type defined in the preamble.

BRIEF DESCRIPTION OF DRAWINGS

In the following description of a preferred embodiment reference will be made to the attached drawings, in which,

Fig. 1 is an axial section through a ball segment valve having a valve seat flexibility and sealing according to the invention, and

Fig. 2 shows the encircled part of Fig. 1 at a larger scale.

DESCRIPTION OF PREFERRED EMBODIMENT

With reference to Fig. 1 a ball segment valve has been generally designated 1. It includes a valve housing 2 in two parts having a cover plate 3 which is secured to the valve housing 2 by screwing and which therefore in this text is considered as an integrated part of the valve housing 2. A shut-off member in a manner per se consists of a spherical segment 4. The shut-off member is rotatable in the valve housing 2 about an axis of rotation 5 by means of a stem 6 journalled In the valve housing. The inlet opening 7 of the passage through the valve is defined by the cover plate 3. The outlet opening has been designated 8 and the center line of the passage has been designated 9.

A valve seat 10 is provided in a recess 11 between the valve housing 2 and the cover plate 3. The ring 10 is homogenous and may consist of metal, of a hard alloy, as for example Stellit, of a comparative hard polymer, such as for example PTFE or PU, of a ceramic material, of a plurality of composite materials, or of any other suitable material or combination of materials. When the segment 4 is rotated in the valve housing 2 the spherical sealing surface 12 of the ball segment will slide against a corresponding sealing surface 13 having the shape of a concave spherical segment on the seat ring 10.

The seat ring 10 terminates with a rear annular surface 14, the inner part 15 of which constitutes the said first sealing surface on the seat ring. (The expression "rear" is used when viewing the device in a direction from the axis of rotation 5.) The surfaces 14, 15 lie in a plane which is perpendicular to the centre line 9 of the passage through the valve. The bottom of the recess 11 consists of an annular surface 16 on the cover plate 3, said annular surface facing the rear surface 14 of the seat ring and being parallel to said rear surface. The outer part 17 of said surface 16 defines the said sealing surface in the bottom of the recess. Between surfaces 14 and 16 there is formed a closed annular first space 18 which in a radial outward direction is limited by the valve housing 2 and inwards by a flange 19 on the cover plate 3 directed inwards towards the valve seat 10. The front edge on flange 19 extends into a first recess 20 on the seat ring 10 provided in that corner of the seat ring 10 which faces the passage of the valve but which is turne^'d from the spherical sealing surface 13 of the seat ring. The flange 19,^' however, does not sealingly contact the seat ring 10. In the corner 21 between the flange 19 and the surface 16 there is a certain radius which is due to production technical reasons.

In that corner of the seat ring 10 which is diagonal to the first recess 20 of the seat ring 10 (when viewing a cross section of the seat ring) there is a second recess 22. This recess is limited by an annular surface 23, which is parallel to the annular surfaces 14 and 16 and by an annular cylindrical surface 24 on the outer side of the seat ring 10. In the outer part of said annular surface 23 the said second sealing surface 25 of the valve seat 10 is provided. The recess 11 in the valve housing 2 is upwardly terminated by an annular surface 26 which is parallel to the surfaces 14, 16 and 23 and which faces the said surface 23. The surfaces 23, 24, 26 and the cylindrical wall of the recess 11 together form an annular second closed space 27. The corners 28 and 29 in this second space 27 as the corner 21 in the first space 18 has a certain radius.

In the first annular space 18 there is a combined first springing and sealing ring 30. This ring in cross section has the substantial form of a Z or an S (depending on which side of the ring the section is taken) . In cross section the ring 30 in other words consists of a first flange 31, a second flange 32 and therebetween a web portion 33. The web portion 33 is inclined at an angle of about 15° against the plane of the ring when the ring is unloaded. When the ring is loaded and located in the space 18 the web 33 will have a considerably smaller angle of inclination against its plane, preferably about 10°. The web portion 33 has a length which is only somewhat less than the breadth of the annular surfaces 14 and 16. The length of the flanges 31 and 32 is considerably smaller than the length of the web portion 33 and is each preferably not more than half and suitably not more than 1/3 of the length of the web portion 33.

The narrow edges 34 and 35 of the flanges 31 and 32, respectively, abut against the said first sealing surface 15 on the seat ring 10, and against the said sealing surface 17 in the bottom 16 of the recess 11, respectively. By turning the ring 30 so that the first inner flange 31 is turned upwards against the seat ring 10, contact with the radius in the corner 31 is avoided. The edges 34, 35 therefore sealingly will abut against the sealing surfaces 15 and 17, respectively. In the second annular closed space 27 there is provided a second springing and sealing ring 40. This ring has the same general form as the first ring 30 but is smaller than the first ring in cross section. In a manner analogous with the ring 30 the parts have been designated in the following way; a first inner flange 41, a second outer flange 42, a web portion 43 and edges 44 and 45 on flanges 41 and 42, respectively. The edge surfaces 44 and 45 sealingly abut against an annular sealing surface 36 in the inner part of the annular surface 26 in the recess 11, and against the second sealing surface 25 on the seat ring 10, respectively. The relative dimensional conditions between on one hand the flanges 41 and 42 and on the other hand the web portion 43 substantially are the same as for the first ring 30. By arranging the ring 40 with its first inner flange 41 turned upwards, i.e. from the seat ring 10 and with the second outer flange 42 turned downwards against the outer part of the annular surface 23 on the seat ring 10 it will be possible to avoid contact with the radii in the corners 28, 29 such that also in this case the whole breadth of the space 27 can be utilized.

Prior to assembly the edge surfaces 34, 35 and 44 and 45, respectively, are adjusted to their sealing surfaces 15, 17 and 36, 26, respectively, by manually rotating the rings repeatedly against their respective sealing surfaces, which therebefore have been provided with an abrasive material. Prior to final assembly the grinding material is removed.

Claims

1. Device relating to control- or shut-off valves having a rotatable shut-off member (4) in the form of a ball or of a segment or a sector of a -ball, a valve housing (2) with a valve seat in the form of a seat ⁵ ring (10) which is lodged to slide in a recess (11) in the valve housing or between the valve housing and a cover plate (3) or corresponding member integrated with the valve housing, and at the rear of the seat ring, as viewed in the direction from the axis (5) of rotation of the shut-off member, an integrated springing and sealing

! member (30) provided to press the seat ring against the sealing surface (12) of the shut-off member and to prevent leakage in the region of the seat ring, said integrated springing and sealing member including a first combined springing and sealing ring (30) in said recess (11) at the rear of the seat ring (10), said first combined

15 springing and sealing ring (30) having an inner first flange (31) extending substantially in parallel with the fluid passage through the valve towards the seat ring and terminating by a narrow first edge (34) which sealingly abuts a first sealing surface (15) on the seat ring or on a member between the first combined springing and sealing

20 ring (30) and the seat ring at the rear of-the seat ring, c h a r a c t e r i z e d in that the combined first springing and sealing ring (30) also includes an outer second flange (32) extending substantially parallel to the first flange but in the opposite direction away from the seat ring towards the bottom of the recess and

25 terminating with a narrow second edge (35) which sealingly abuts a first sealing surface (17) in the bottom (16) of the recess, and that the said first combined springing and sealing ring (30) has a web portion (33) connecting the two flanges (31, 32).

30 2. Device according to claim 1, c h a r a c t e r i z e d in that the springing and sealing ring (30) in cross section has the substantial form of a Z or an S.

3. Device according to claim 1 or 2, c h a r a c t e r i z e d in 35 that the web portion (33) is substantially horizontal or is inclined at an angle up to 30° against the plane of the ring, at the same time as it forms an angle > 90° against the flanges.

4. Device according to claim 3, c h a r a c t e r i z e d in that the said angle between the web portion and the plane of the ring is between 10 and 20°.

5. Device according to any of claims 1-4, c h a r a c t e r i z e d in that the sealing surfaces which cooperate with the edges (34, 35) on the ring (30) are provided on the seat ring (10) and on a cover plate (30), respectively, or corresponding member forming the bottom of the recess (11).

6. Device according to any of claims 1-5, c h a r a c t e r i z e d in that a second springing and sealing ring (40), which is of essentially the same type as the first ring (30) but having a smaller cross section, is provided in an annular recess (27) in the seat ring on the opposite side of the seat ring with reference to the location of the said first ring, an inner, first flange (41) on said second ring extending substantially parallel to the first flange on the first ring and terminating with a narrow edge (44) which abuts against a circumferential second sealing surface (36) in the recess in the valve housing, and a second, outer flange (42) extending substantially parallel to the said second outer flange on the first ring (30) and terminating with a narrow edge (45) which sealingly abuts a sealing surface (26) in the outer part of said second annular recess (27).

7. Device according to claim 6, c h a r a c t e r i z e d in that the sealing surfaces (36 and 26, resp.) cooperating with the edges (44, 45) on said second ring (40) are provided in the valve housing in an inner part of the recess (11) and on the seat ring (10), respectively in the outer part of an outer recess in the seat ring.