GB2215437A

GB2215437A - Rotary ball valve

Info

Publication number: GB2215437A
Application number: GB8805698A
Authority: GB
Inventors: Rutger Berchem; Georg Prokscha
Original assignee: Berchem and Schaberg GmbH
Current assignee: Berchem and Schaberg GmbH
Priority date: 1988-03-09
Filing date: 1988-03-10
Publication date: 1989-09-20
Anticipated expiration: 2008-03-10
Also published as: NL8800580A; GB2215437B; FR2628498B1; FR2628498A1; GB8805698D0

Abstract

A rotary ball valve more particularly for material streams carrying abrasive solid particles, has a pressure-tight housing (1), a valve seating (2) consisting of sintered ceramic seating rings (3), a sintered ceramic valve ball (4), and an actuating shaft (5) for the valve ball entering through a shaft seal (6) in the housing. The housing (1) has a single-piece jacket (7) with duct unions (8) attached to the jacket through intermediate seals (9), while resilient seals (12) which urge the seating rings (3) against the valve ball (4) under pre-stress are disposed on the duct unions (8). According to the invention the length (L) of the jacket (7) exceeds the overall length of the valve seating (2), between the duct unions (8) and the valve seating (2) there are inserted wear liners (10), the insides of which are flush with the seating rings (3), the wear liners bear on the resilient seals (12) at their endfaces further from the valve seating (2) and the outer peripheries (13) of the wear liners (10) are supported in the housing (1). <IMAGE>

Description

ROTARY BALL VALVE This invention relates to a rotary ball valve, more particularly for material streams carrying abrasive solid particles, having a pressure-tight housing, a valve seating consisting of sintered ceramic seating rings, a sintered ceramic valve ball, and an actuating shaft for the valve ball entering through a shaft seal in the housing, in which the housing has a single-piece jacket with duct unions attached to the jacket through intermediate seals, while resilient seals which urge the valve seating against the valve ball under pre-stress are disposed on the duct unions.

DE-PS 35 45 547.8-12 describes a rotary ball valve of this type in which the valve seating is set inside a pressure-tight housing jacket. The length of the jacket equals the overall length of the valve seating. On the endfaces there are duct unions each having a closure flange diameter corresponding to the effective section of the seating rings. The valve seating is held between the closure flanges through interposed resilient seals and it maintains a sealing contact with the valve ball by virtue of the resilient seals. The sintered wearing components float within the pressure-tight housing provided by the jacket and the duct unions. The radial component of the working pressure, the bending moments and the axial tensile loads from the adjacent ducts, are all transmitted to the housing.

In basic design, this rotary ball valve is intrinsically sound. Nevertheless, problems arise when the rotary ball valve is used as a throttle valve in systems handling liquids containing abrasive suspended solids. Increased stream velocities in the vicinity of the throttle aperture, and pronounced turbulence downstream of the throttle aperture, lead to intensive wear in the vicinity of the duct unions and adjacent ducts, which are frequently unprotected by positive anti-wear means.

The object of the invention is to provide an improved rotary ball valve of the type initially described, particularly for use as a throttle valve in systems handling gaseous and liquid material streams which carry abrasive solid particles, so that excessive wear in the vicinity of the duct unions and adjacent ducts is eliminated.

According to the present invention, the length of the jacket exceeds the overall length of the valve seating, wear liners are inserted between the duct unions and the valve seating, the insides of the wear liners are flush with the seating rings, the wear liners bear on resilient seals interposed between their endfaces further from the valve seating and the duct unions, and the outer peripheries of the wear liners are supported in the housing. The length of the jacket is preferably at least twice the outer length of the valve seating.

Wear liners are liners made from wear-resisting material, preferably a sintered ceramic. All the ceramic wear components are protected against bending and tensile loads inside a rigid jacekt. The rotary ball valve is intrinsically pressure-tight. If the internal pressure becomes excessive compared with the strength limits of the ceramic material, the wear components are backed up by the pressure-tight housing and the functional reliablity of the rotary ball valve remains unimpaired.

Whilst the sealing surfaces of the valve ball and the seating rings are wear resistant, the adjacent channel walls exposed to extreme abrasive loads are also protected against wear. The invention arises from the realisation that throttle valves are subjected to increased abrasive attack upstream and downstream of the throttle aperture. The worst effects are concentrated over a length corresponding to about three times the aperture diameter upstream and downstream of the throttle aperture. In this region, turbulence in the presence of suspended solids leads to intensive abrasive wear.

It is within the scope of the invention to make the wear liners of equal wall thickness to the seating rings and fit them directly into the supporting jacket walls.

However, the wear resistance of sintered ceramics is so high that it is not fundamentally essential to fit wear liners of such substantial thickness. For this reason and on practical grounds it is preferable to fit the wear liners inside spacer liners which. in turn fit. against the jacket walls. When the rotary ball valve is used for liquids in which crystallisation can develop, the risk arises that the spacer liners will seize and become difficult, if not impossible, to withdraw. For this particular application, the duct unions are preferably formed as withdrawable sleeves and inserted endwise into the jacket, each withdrawable sleeve having a holding face for the respective seating ring and an annular chamber accommodating the respective wear liner. The withdrawable sleeves are obviously made accessible to withdrawal tools.Each withdrawable sleeve preferably has an outer flange fitting within a recess in the respective endface of the jacket and secured to the housing by countersunk screws, and only a sealing collar on the withdrawable sleeve protrudes beyond the endface of the jacket. It is preferable on practical grounds to make the rotary ball valve symmetrical, with inlet and outlet wear liners of equal length. However, the wear beyond a throttle aperture is intrinsically greater than that upstream of the aperture. This fact can be and is utilised in a preferred embodiment of the invention within the valve ball is offset from the longitudinal midpoint and the length of the downstream wear liner exceeds that of the upstream wear liner.

A further advantageous preferred feature of the invention is that a supporting ring of wear-resisting material is disposed round the perimeter of the valve ball, fitting in the jacket and having an orifice for the actuating shaft, the ring being held in the axial direction beween two stopfaces against longitudinal movement. The supporting ring is also preferably made from a sintered ceramic. The provision of a sintered ceramic supporting ring is advantageous when the jacket consists of a relatively soft material. Because of the high finish and wear resistance of the contact faces between the valve ball and the supporting ring, adhesion between them can be prevented and easy actuation of the valve ball is retained over long periods.

Furthermore, sudden throttling can set up stream-induced vibrations acting on the contact faces on the perimeter of the valve ball. The stopfaces between which the supporting ring is held can be provided by spacing sleeves secured between the duct unions. Preferably, however, a duct union component is provided with one stopface for the supporting ring, and the supporting ring together with an interposed seal is held between the other stop face on a shoulder in the jacket and the stopface on the duct union component, optionally along with washers. The rigid shoulder in the jacket facilitates the insertion and positioning of the supporting ring. It is also obvious that the duct union component can be adapted to act simultaneously as a withdrawable sleeve for the seating ring and th-e wear liner.

In this case, the duct union component has a first stopface for the supporting ring, a second holding face and an annular chamber accommodating a wear liner.

Thus protected against wear by the wear liners upstream and downstream of the valve ball, the jacket can be made from either metallic or nonmetallic materials, as required. On the assumption that metallic materials are used, the jacket is formed as a thickwalled cylindrical hollow forging and the shaft seal for the actuating shaft is disposed in a hole in the jacket. If minimising weight is particularly important, the jacket can be a thickwalled hollow cylinder of fibre-reinforced synthetic material, the shaft seal again being disposed in a hole in the jacket.

The rotary ball valve of the invention has an outstandingly high functional reliability. It is intrinsically pressure-tight. If the ceramic fails under pressure overloads or thermal shock, the failed ceramic components are backed up by the pressure-tight jacket and the functional reliability of the valve remains unimpaired. The advantages over the known valves of this type are to be seen in a superior protection against wear. The features of the invention are particularly significant when the rotary ball valve is used as a throttle valve in systems handling gaseous or liquid material streams containing abrasive suspended solids. Turbulence is dissipated in the regions of the valve protected against wear. Accordingly, abrasive attack on the ducts connected to either union is greatly reduced.

The rotary ball valve of the invention is particularly useful as a throttle valve in systems which have no special wear protection. Moreover, the valve of the invention is of simple design and the ceramic components are outstandingly easy to assemble and dismantle. Easy dismantling is an important practical consideration, since cermaic components which have failed under pressure overload or thermal shock must be replaced without delay. Moreover, easy dismantling is essential when the rotary ball valve of the invention is required for handling liquids prone to crystallising out.

After shutdowns or lengthy stoppages, the rotary ball valves must be dismantled and cleaned.

A number of embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through a rotary ball valve in accordance with the invention; Figure 2 shows a modified form of rotary ball valve in accordance with the invention, again in longitudinal section; Figure 3 is a part-sectional part-elevational detail of the duct union component as in Figure 2; Figure 4 shows, again in longitudinal section a preferred embodiment of rotary ball valve in accordance with the invention and having a wear-resisting supporting ring for the valve ball; and Figure 5 shows a longitudinally asymmetric version of the rotary ball valve of Figure 4.

The rotary ball valves shown in the drawings are suitable for use more particularly as throttle valves for material streams carrying abrasive solid particles. Each consists basically of a pressure-tight housing 1, a valve seating 2 consisting of sintered cermaic seating rings 3, a sintered ceramic valve ball 4, and an actuating shaft 5 which enters through a shaft seal 6 in the housing 1, which consists of a single-piece jacket 7 and duct unions 8, attached to the jacket 7 through intermediate jacket seals 9.

The length L of the jacket 7 exceeds the overall length a of the valve seating 2. The jacket length L is preferably at least twice the overall length a of the valve seating. Between the duct unions 8 and the valve seating 2 there are inserted wear liners 181 which internally are flush with the seating rings 3 and which in Figure 1 bear on resilient seals 12 interposed between their endfaces 11 further from the valve seating and the duct unions 8. Also in Figure 1, the outer faces 13 of the wear liners 18 are surrounded by spacer liners 14 which fit against the jacket 7. The resilient seals 12 are held under elastic prestress. On the one hand, they function as static seals, while on the other hand they give the seating rings 3 a low mobility and urge the seating rings 3 under pre-stress against the valve ball 4.

In the embodiment shown in Figure 2 the duct unions are formed as withdrawable sleeves 15 and inserted endwise into the jacket 7. Reference to Figure 3 will show that each withdrawable sleeve 15 has a holding face 16 for the respective seating rings 3 and an annular chamber 17 accommodating the respective wear liner 1. Each withdrawable sleeve 15 also has an outer flange 18 with a sealing face 2 on a sealing collar 19 for a flange seal (not shown) for connecting to the respective duct (not shown).

The outer flange 18 of each withdrawable sleeve fits flush within a recess in the respective endface of the jacket 7 and is secured thereto by countersunk screws 21, the arrangement being such that only the sealing collar 19 with its sealing face 2 protrudes beyond the endface 22 of the jacket 7.

The countersunk screws 21 merely facilitate assembly and transmit no significant forces. Seals 23b are provided between the holding faces 16 and the seating rings 3, and seals 23a are provided between the outer collars 18 and the wear liners 18, which seals can consist of O-ring seals.

They act on the seating rings 3 as both static seals and resilient cushions.

Figure 4 depicts a preferred embodiment of rotary ball valve in accordance with the invention, in which a supporting ring 24 of wear-resisting material, preferably sintered ceramic, is disposed round the perimeter of the valve ball 4.

The supporting ring 24 fits within the jacket 7 and has an orifice 25 for the actuating shaft 5. In the axial direction, it is held between stopfaces 26, 27, the stopface 26 being provided as a shoulder in the jacket, while a duct union component 28, which is also formed as a withdrawable sleeve for the seating rings 3 and the wear liners l, is provided with the other stopface 27 for the supporting ring 24. On the stopface 27 of the duct union component 28 there is also provided a seal 29, which can be an O-ring seal.

Washers 3 are also provided, between the supporting ring 24 and its stopfaces 26, 27, the washers also extending into the region of the seating rings 3 and acting as additional securing components for the seating rings.

In Figures 1 to 4, the wear liners 1111 on the inlet and outlet sides are equal in length. According to a further feature of the invention, and as shown in Figure 5, the valve ball 4 may be offset from the longitudinal midpoint of the housing, in which case the length la of the downstream wear liner la exceeds the length lb of the upstream wear liner 1 orb. The length of the downstream wear liner IBa is preferably sufficient for the dissipation of stream turbulence. The preferred length 1a for the downstream wear liner la is three times the diameter d of the valve ball aperture.

The jacket 7 in all the embodiments shown is formed as a thickwalled cylindrical hollow forging. The shaft seal 6 for the actuating shaft 5 is disposed in a hole 31 in the jacket 7. The jacket also has a plane assembly face 32 for the attachment of actuating componenets and setting means.

Claims

1. A rotary ball valve having a pressure-tight housing, a valve seating consisting of sintered ceramic seating rings, a sintered ceramic valve ball, and an actuating shaft for the valve ball entering through a shaft seal in the housing, in which the housing has a single-piece jacket with duct unions attached to the jacket through intermediate seals, while resilient seals which urge the seating rings against the valve ball under pre-stress are disposed on the duct unions, and wherein the length of the jacket exceeds the overall length of the valve seating, wear liners are inserted between the duct unions and the valve seating, the insides of the wear liners are flush with the seating rings and the wear liners bear on resilient seals interposed between their endfaces further from the valve seating and the duct unions, and the outer peripheries of the wear liners are supported in the housing.

2. A rotary ball valve as in Claim 1, wherein the length of the jacket is at least twice the overall length of the valve seating.

3. A rotary ball valve as in Claim 1 or Claim 2, wherein the outer peripheries of the wear liners bear on spacer liners supported against the jacket.

4. A rotary ball valve as in Claim 1 or Claim 2, wherein the duct unions are formed as withdraw able sleeves and inserted endwise into the jacket, each withdrawable sleeve having a holding face for the respective seating ring and an annular chamber accommodating the respective wear liner.

5. A rotary ball valve as in Claim 4, wherein each withdrawable sleeve has an outer flange fitting within a recess in the respective endface of the jacket and secured to the housing jacket by countersunk screws, and only a sealing collar on the withdrawable sleeve protrudes beyond the endface of the said jacket.

6. A rotary ball valve as in an one of Claims 1 to 5, wherein the valve ball is offset from the longitudinal midpoint, and the length of the downstream wear liner exceeds that of the upstream wear liner.

7. A rotary ball valve as in an one of Claims 1 to 6 wherein a supporting ring of wear-resisting material is disposed round the perimeter of the valve ball, fitting in the jacket and having an orifice for the actuating shaft, the supporting ring being held in the axial direction between stopfaces.

8. A rotary ball valve as in Claim 7, wherein a duct union component is provided with one stopface for the supporting ring, and the supporting ring together with an interposed seal is held between the other stopface on a shoulder in the jacket and the stopface on the duct union component.

9. Rotary ball valves substantially as hereinbefore described with reference to the accompanying drawings.

9. A rotary ball valve as in any one of Claims 1 to 8, wherein the jacket is formed as a thickwalled cylindrical hollow forging, and the shaft seal for the actuating shaft is disposed in a hole in the jacket.

1B. A rotary ball valve as in any one of Claims 1 to 8, wherein the jacket is formed as a thickwalled cylinder of fibre-reinforced synthetic material, and the shaft seal for the actuating shaft is disposed in a hole in the jacket.

11. Rotary ball valves substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS

1. A rotary ball valve having a pressure-tight housing, a valve seating consisting of sintered ceramic seating rings, a sintered ceramic valve ball held under prestress between the seating rings, and an actuating shaft for the valve ball entering through a shaft seal in the housing, in which the housing has a single-piece jacket with duct unions attached to the jacket through intermediate seals, and wherein the length of the jacket exceeds the overall length of the valve seating, wear liners are inserted between the duct unions and the valve seating, the insides of the wear liners are flush with the seating rings and the wear liners bear on resilient seals interposed between their endfaces further from the valve seating and the duct unions, the duct unions are formed as withdrawable sleeves and inserted endwise into the jacket, each withdrawable sleeve having a holding face for the respective seating ring and an annular chamber accommodating the respective wear liner, and each withdrawable sleeve also having outer flange secured to the end of the jacket.

3. A rotary ball valve as in Claim 1 or Claim 2, wherein the outer flange of each withdrawable sleeve fits within a recess in the respective endface of the jacket and is secured to the housing jacket by countersunk screws, and only a sealing collar on the withdrawable sleeve protrudes beyond the endface of the said jacket.

4. A rotary ball valve as in any one of Claims 1 to 3, wherein the valve ball is offset from the longitudinal mid-point, and the length of the downstream wear liner exceeds that of the upstream wear liner.

5. A rotary ball valve as in any one of Claims 1 to 4, wherein a supporting ring of wear-resisting material is disposed round the perimeter of the valve ball, fitting in the jacket and having an orifice for the actuating shaft, the supporting ring being held in the axial direction between stopface s.

6. A rotary ball valve as in Claim 5, wherein a duct union component is provided with one stopface for the supporting ring, and the supporting ring together with an interposed seal is held between the other stopface on a shoulder in the jacket and the stopface on the duct union component.

7. A rotary ball valve as in any one of Claims 1 to 6, wherein the jacket is formed as a thickwalled cylindrical hollow forging, and the shaft seal for the actuating shaft is disposed in a hole in the jacket.

8. A rotary ball valve as in any one of Claims 1 to 6, wherein the jacket is formed as a thickwalled cylinder of fibre-reinforced synthetic material, and the. shaft seal for the actuating shaft is disposed in a hole in the jacket.