GB2178511A

GB2178511A - Fluid medium control valve

Info

Publication number: GB2178511A
Application number: GB08615252A
Authority: GB
Inventors: Lutz P Warlich
Original assignee: Garlock GmbH
Current assignee: Garlock GmbH
Priority date: 1985-08-02
Filing date: 1986-06-23
Publication date: 1987-02-11
Also published as: SE463733B; SE8602759L; GB8615252D0; SE8602759D0; FR2585800B1; GB2178511B; IT8648265A0; FR2585800A1; CH671441A5; DE3527738A1; IT1195858B; DE3527738C2

Abstract

To protect fluid media, in particular those with a high degree of purity, against bacterial pollution, a valve 1 of the disc or butterfly type having a disc 3 in a housing 2 is provided with a control spindle 4 which extends through the valve and is surrounded by fluid flow ducts 14 and is provided with inner and outer seal systems 9, 10. Sterile steam is distributed via an inlet valve 11 from an annular duct 12 to the steam ducts 14 disposed around the spindle and the steam exits from the control spindle cavity via an exit valve 17. The steam flow keeps the internal interstices of the valve sterile. <IMAGE>

Description

SPECIFICATION Fluid flow control valve This invention relates to a fluid flow control valve of the disc or butterfly type which is particularly intended for use with fluid media of high purity.

In many processes, more particularly those concerned with pharmaceutical products, the fluid media in various processing stages are subject to maximum purity demands. Fittings used in these processes must therefore be regularly disinfected or sterilised. A maximum degree of purity can be permanently and reliably achieved only by sterilisation, especially by steam sterilisation, which is more effective than hot air sterilisation. Steam under pressure with a temperature of up to 1350C is used for steam sterilisation.

Valves used in such processes should be so arranged that no bacteria are able to enter into the fluid media, despite the movable valve components. Especially in vacuum processes, no bacteria must be able to reach the media from the outside through the ingress of air.

The object of the invention is to provide a fluid flow control valve of the disc or butterfly type, in which, in use, a product stream is reliably protected against bacterial and other pollution from the ambient zone of the valve.

To this end, according to this invention, we provide a control valve of the disc or butterfly type for controlling the flow of fluid media comprising a control disc which is supported on a control spindle in a housing, wherein the control spindle extends through the disc and is surrounded by a fluid flow passage having an inlet for the flow of a sterile fluid, and a system of seals which seal the passage from the outside and from the inside of the housing, through which, in use, the fluid media flow.

The seal system preferably comprises an inner seal system disposed between an inner valve chamber and a housing lining, and an outer seal system, disposed between the housing lining and the housing and surrounding the spindle and being disposed at the position where the spindle extends from the housing. The through-extending control spindle permits a floating support to be provided for the disc, i.e. the disc is not rigidly fixed to the spindle but is guided thereby, so as to avoid stresses in the event of thermal expansion.

Proceeding from the knowledge that steam sterilisation ensures reliable and durable sterilisation, the fluid which, in use, flows through the passage can be sterile steam under pressure higher than that of the product medium controlled by the valve. The higher steam pressure prevents the ingress of bacterial contamination into the product stream even in the event of failure of the inner seal system, for example in vacuum processes; instead, only sterile steam can enter the product stream.

To ensure that the control spindle is uniformly surrounded by steam, it may be provided with longitudinal ducts, which communicate with an annular duct, supplied via a steam inlet valve.

If the inner seal system comprises a ring seal, disposed concentrically with respect to the control spindle at the top and bottom end of the contact surfaces between the disc and the housing lining, it is possible for the medium-accommodating space, hereinafter referred to as the process space, to be reliably sealed with respect to the cavity which accommodates the control spindle. To provide sealing with respect to the exterior for the steam chamber comprising the annular duct and the longitudinal ducts, for example against the atmosphere, an outer seal system may comprise a plurality of O-rings surrounding the control spindle and a ring seal, disposed concentrically with respect to the control spindle, between the housing lining and the housing.

Sterile steam, which enters into the steam chamber via the inlet valve can discharge through an exit valve, disposed in a closure stopper, which also seals the steam chamber with respect to the exterior.

The invention will be explained hereinbelow by reference to one exemplified embodiment with some modifications which are illustrated in the accompanying drawings, in which: Figure 1 is partial diametric section through the valve, shown with a valve disc in an open position; Figure 2 is a cross-section of a control spindle of the valve along the line ll-ll of Fig. 1; Figure 3 is a cross-section of the control spindle along the line Ill-Ill of Fig. 1; Figure 4 is a cross-section of the control spindle along the line IV-IV of Fig. 1; Figure 5 is a cross-section of the control spindle along the line V-V of Fig. 1; Figure 6 is a detail to a larger scale of part of the valve; Figure 7 shows an alternative seal in the detail of Fig. 6; and, Figure 8 shows another alternative seal in the detail of Fig. 6.

The valve 1 comprises an annular housing 2, a control disc 3, which when closed extends across and closes the housing, and a control spindle 4, which extends wholly or partially through the housing 2 and extends fully through the disc 3. The valve housing 2, comprising two parts, merges in its upper half into a neck 5 with a flange 6 and is provided with a lining 7 of high density. Two resilient half shells 8, which do not come into contact with the medium and cannot therefore be attacked thereby, and are disposed between the housing 2 and the housing lining 7, provide a sealing-tight seating for the disc 3 in the closed position.

Ring seals 9 and 10, disposed at the top and bottom in the region in which the control spindle 4 extends from the housing 2 into the housing lining 7 and from there into the disc 3, reliably and permanently seal the process chamber, which is not shown, but is fixed to the housing 2, even under conditions of alternating temperature loading, with respect to the control spindle 4 and therefore with respect to the exterior. Figs. 6 to 8 show different possible embodiments of the ring seals 10 which are constructed in the same way as the ring seals 9.

Additional sealing of the process chamber against external effects is achieved by steam sterilisation of the control spindle 4. Sterile steam passes into an annular duct 12 via an inlet valve 11 which extends into a bore that penetrates the neck wall 5. A locking screw 13 is situated opposite to the inlet valve.

From the annular duct 12, the steam passes via four steam ducts 14, disposed uniformly around the circumference of the control spindle 4, into the control spindle locating bore 15, which is sealed by a closure stopper 16 with integrated or separately arranged exit valve 17, and to the lower half of the housing 2.

On the other side, i.e. on the end opposite to a spindle closure stopper 16, the locating bore 15 of the control spindle is sealed by a plurality of O-rings 18, which surround the control spindle 4 and are surrounded by the housing 2.

That part of the control spindle 4, which projects from the housing 2, is of square cross-section and that part which is surrounded by the housing 2 and the housing lining 7 is of circular cross-section (Figs. 2, 3, 5), housing disposed below the annular duct four semi-circular notches, which are uniformly distributed over the circumference and represent the steam ducts 14 and communicating with the notches of that cross-section of the control spindle 4 (Fig. 4) which is substantially square in the region of the check disc 3.

Figs. 2 to 5 illustrate the changing crosssection of the control spindle 4 above and below the annular duct 12 and the end of the control spindle 4, nearest to the closure stopper 16 is journalled into a bush 19, embodied as a maintenance-free plain bearing.

The valve, suitable especially in the field of chemistry for shutting-off, restricting and regulating corrosive and abrasive media, is not only of light weight and space saving because of its simple construction, but can also be simply installed and operated; it is diffusiontight but especially because of its double seal system it is gas-tight and liquid-tight as well as vacuum tight. More particularly, the valve according to the invention ensures that no impurities can reach the process chamber from the exterior via the control spindle.

In tests extending over several months, a valve according to the invention was innoculated at particularly critical places, namely in the region of the inlet valve 11, the ring seals 9 and the closure stopper 16, with a biological indicator, which was applied to a nutrient solution after sterile steam with a temperature of 131"C had been conveyed for 30 minutes along the control spindle as well as through the process chamber and after both chambers had been blown through with sterile air. All tests showed that the entire biological indicator had been killed. All seal systems functioned perfectly.

Claims

1. A control valve of the disc or butterfly type for controlling the flow of fluid media comprising a control disc which is supported on a control spindle in a housing, wherein the control spindle extends through the disc and is surrounded by a fluid flow passage having an inlet for the flow of a sterile fluid, and a system of seals which seal the passage from the outside and from the inside of the housing, through which, in use, the fluid media flow.

2. A valve according to Claim 1, in which the control spindle is provided with at least one longitudinal duct, through the disc, which forms the passage and is connected to an annular duct which, in use, is supplied with steam via an inlet valve.

3. A valve according to Claim 1 or Claim 2, in which the seal system comprises an inner seal system which seals the passage from the inside of the housing and which comprises a ring seal which is disposed concentrically with respect to the control spindle and defines the contact surfaces of the disc and a housing lining, the ring seal engaging respectively with the disc and with the housing lining.

4. A valve according to Claim 1, substantially as described with reference to Figs. 1 to 6 of the accompanying drawings.

5. A valve according to Claim 4, but modified substantially as described with reference to Fig. 7 or Fig. 8 of the accompanying drawings.