DE29923799U1 - Double-seat valve with flushable valve rod bushing on the valve housing - Google Patents

Description

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Double seat valve with flushable valve rod feedthrough

on the valve housing

The innovation relates to a double seat valve with a flushable valve rod passage on the valve housing according to the preamble of claim 1.

A double seat valve of the generic type is known, for example, from EP 0 039 319 B1 or US 4 605 035 , whereby the focus in connection with the present innovation is on the flushable valve rod passages on the valve housing. Such a valve rod passage is known to be a critical area, since product that inevitably adheres to the part of the valve rod that extends into the valve housing can be carried into the area behind the valve rod seal in the valve housing during the opening movement of the valve. This carryover or the so-called "elevator effect" is unavoidable because the surface of the valve rod, seen microscopically, has roughness depths in which product residues accumulate that cannot be or can only be inadequately removed by the stripping effect of the rod seal that seals the valve rod in the valve housing. Once product residues have been carried into the area behind the seal, they can become contaminated there and then, during the further production process and as a result of new switching movements of the valve, can be transported from this area back into the valve housing via the reverse "elevator effect". The product can then become contaminated with these germs, which must be avoided at all costs.

In order to avoid the aforementioned effects, such valves, especially when special requirements are placed on the hygienically perfect handling of the product, are provided with flushable valve rod passages, as shown in the two aforementioned publications. At certain intervals, the annular space formed between a housing connected to the outside of the valve housing and the valve rod leading through and out of the valve housing is

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flushed with cleaning and/or disinfectant agents via an inlet and outlet connection.

Flushing the valve rod passage is particularly necessary when the valve rod has a relatively large diameter, which in turn requires a correspondingly large valve rod seal with a correspondingly large carryover cross-section. Such large valve rods are always required when the latter are provided with a compensating piston, a so-called balancer, for the purpose of compensating for pressure forces exerted on the closing element by the fluid in the valve housing. These pressure forces can be compensated as far as possible when the compensating piston has the same diameter as the passage cross-section of the respective associated valve seat. The publications EP 0 039 319 B1 and US 4 605 035 show such designs with valve rod passages that are particularly critical in terms of hygiene because of their large diameter. The annular space surrounding the valve rod, which is provided with an inlet and outlet connection, has a certain axial extension, and the arrangement of the outlet connection at the lowest point of the annular space ensures that it can drain.

The publication DE 35 16 128 C2 describes a so-called double-sealing valve which has a single closing element with two seals arranged at an axial distance from one another and whose valve rods arranged on both sides of the closing element are provided with a flushable annular space in the area of their respective valve housing passage. In this valve too, the respective annular space ends directly at the rod seal, as far as can be seen from the rather schematic representation, and it can be completely emptied of cleaning and/or disinfectant via a drain connection provided at its lower end.

The complete emptying of the annular space described above is important, as it has been shown that the rinsing agents used can be aggressive and that

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Even water used to rinse the annular space, if it contains a particularly high level of chlorine, for example, can lead to pitting of the metallic materials involved if it remains in the annular space for a long period of time.
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The arrangement of the rod seal which delimits the annular space on the housing side and the arrangement of the annular space itself have disadvantages in the double seat valves mentioned above (EP 0 039 319; US 4 605 035). For example, the said rod seal is not extended to the interior of the valve housing, but there is a relatively narrow annular gap between the valve housing and the valve rod, which represents a critical point for cleaning, which can at best be reached by cleaning fluid from the valve housing.

This problem is solved, for example, by a known device for cleaning a seal for a rod that is guided in a valve housing so that it can move mainly axially (DE 38 41 301 CZ). In this device, the rod seal on the housing side is guided directly up to the interior of the valve housing and ends there essentially flush with the boundary surface of the interior. The device shows the sealing and cleaning of the valve rod lead-through on a valve rod that extends downwards in relation to the position shown. The solution is also particularly suitable for a double-seat valve in which the valve rod is guided upwards through the valve housing and out of it. When the device is rotated by 180 degrees, it reveals that, in contrast to the double-seat valves according to EP 0 039 319 or US 4 605 035, no so-called "dome" is formed in the valve housing in the area of the rod seal on the housing side, in which gas can collect or in which liquid can stagnate.

If, for example, one considers the known double seat valve according to EP 0 039 319 or US 4 605 035 from this perspective, one can see that in the area of the housing-side rod seal a relatively pronounced "dome"

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is formed. To avoid such a dome, the rod seal in connection with the adjacent valve housing part, similar to the valve according to DE 38 41 301 C2, would have to be brought up to the highest point in the valve housing, in relation to the height of the pipe socket connected to the valve housing. In this case, however, the annular space, which is also displaced by this amount towards the interior of the valve housing, could no longer be completely emptied via a drain connection arranged in the immediate vicinity of the housing-side rod seal. The same problem also arises with the double seat valve according to DE 35 16 128 C2.

The object of the present innovation is to create a double-seat valve of the generic type which, with a dome-free design of the valve housing, has a completely drainable, flushable valve rod passage in the penetration area with the valve rod.

The object is achieved by the features of claim 1. An advantageous embodiment of the proposed double seat valve is the subject of subclaim 2.

The proposed solution can always be used when the valve rod performs a lifting movement leading out of the associated valve housing at its sealing point during the opening movement of the valve. In this case, the outlet of the drainage line on the annular space side remains in the annular space throughout the entire opening and closing movement of the closing element. The annular space is completely emptied when the valve is in the closed position, since in this position the valve is directly or indirectly connected to the leakage cavity via at least one drainage line formed within the valve rod in the immediate vicinity of a rod seal that seals the valve rod against the associated valve housing.

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The innovation is applicable to any double seat valve in which a valve rod, based on the installation position of the double seat valve, is guided upwards through the associated valve housing and out of it. It is irrelevant whether the valve rod is one for actuating the closing element, as is the case according to EP 0 039 319 with the valve rod designed as a hollow rod for the upper closing element, or whether it is a valve rod which is guided through and out of the associated valve housing solely for the purpose of guiding and/or for the purpose of supplying or removing leakage and/or cleaning fluid from the leakage cavity. The only decisive factor is that this valve rod meets the kinematic requirements mentioned above and that the valve rod, based on the installation position of the valve, penetrates the valve housing upwards. The latter case would arise, for example, if the double-seat valve according to US 4 605 035 were to be arranged overhead, i.e. if, for structural reasons or for reasons of the space available, the drive is to be provided below the double-seat valve and the annular space surrounding the valve rod extending upwards is to be completely emptied.

The proposed innovation is particularly advantageous when the valve rod, as provided for in a further embodiment, is designed as a compensating piston in the area of its sealing passage through the valve housing, which is shaped to largely compensate for pressure forces exerted on the closing element by the fluid in the valve housing. In this case, due to the large diameter design of the valve rod, a correspondingly large-volume dome in the penetration area between the valve housing and the valve rod is avoided.

An embodiment of the innovation is shown in the drawing and is described below. The only figure in the drawing shows a central section through a preferred embodiment of a double seat valve, which has an independently driven closing element designed as a slide piston and

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a dependently driven closing element designed as a seat plate, which opens upwards in the preferred installation position of the double seat valve and in which the respective valve rod leading upwards and downwards through the associated valve housing and out of it is each provided with a so-called pressure compensation piston.

The double seat valve 1 consists of a first and a second valve housing 1a and 1b. Both are connected to one another via a connecting bore 1c. A first closing element 2 (active closing element) designed as a slide piston is sealingly received in the cylindrical connecting bore 1c when the double seat valve 1 is in the closed position. For this purpose, a radial sealing means 12 is provided on the slide piston 2. A second closing element 3 (passive closing element) designed as a seat plate seals on a seat surface 1d when the valve is in the closed position. The slide piston 2 is connected to a drive 14 via a first valve rod 2a, which is guided upwards through the valve housing 1a and out of it. The seat plate 3 is connected to the drive 14 via a second valve rod 3a designed as a hollow rod, which concentrically encloses the first valve rod 2a and which is also guided upwards through the valve housing 1a and out of it. In addition, the slide piston 2 is equipped with a further valve rod 2a* on its side opposite the first valve rod 2a, which is guided through and out of the associated second valve housing 1b. The valve rod 2a* is designed as a first compensating piston 2b in the area of its sealing passage through the second valve housing 1b, which is shaped to largely compensate for pressure forces exerted on the slide piston 2 by the fluid in the second valve housing 1b. The valve rod 2a* is provided on the inside with a drain hole 2c, which connects a leakage cavity 4 formed between the seat plate 3 and the slide piston 2 in both the closed and open positions of the double seat valve 1 with the surroundings of the double seat valve 1 via connecting holes 2d.

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A second connection path between the leakage cavity 4 and the environment of the double seat valve 1 is realized by an annular gap 13 formed between the first valve rod 2a and the hollow rod 3a surrounding it. On the environment side, this annular gap 13 is provided with a connection 13a for supplying, for example, cleaning and/or disinfection agents.

The opening movement of the double seat valve 1 takes place in such a way that the slide piston 2 first carries out an upward partial stroke movement until it comes into contact with the seat plate 3 and also moves this into the open position during the further opening movement. The closing movement of the double seat valve 1 takes place in the reverse order. The second valve rod 3a is designed in the area of its sealing passage through the associated first valve housing 1a in the form of a second compensating piston 3b, which is shaped to largely compensate for pressure forces exerted on the seat plate 3 by the fluid in the first valve housing 1a.

The first valve housing 1a is adjoined on the outside by a first housing 5 through which the second valve rod 3a is guided. Between the first housing 5 and the second valve rod 3a, a first annular space 5a is formed, which is connected to the surroundings of the double seat valve 1 via an inlet connection 5b and an outlet connection 5c, which is preferably arranged diametrically to this. Viewed in the axial direction, the first annular space 5 is delimited on the housing side by a first rod seal 6a and on the surrounding side by a first annular space seal 6b. The annular space 5 is flushed in such a way that the flushing agent to be used is fed to the inlet connection 5b and from there is fed to the first rod seal 6a via an inlet path 5d directed from top to bottom. From there, the flushing agent then flows upwards through the first annular space 5a in order to leave it via the outlet connection 5c.

The first valve housing 1a is equipped with a first clamping flange 1e in the area of the first housing 5, which in conjunction with a complementary

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formed second clamping flange 7a secures the first housing 5 on and in the first valve housing 1a. By means of an insert 8, which is fixed between the valve housing 1a and the first housing 5, the first rod seal 6a is secured on the rod side and a housing seal 11 is secured on the housing side. The second clamping flange 7a marks the end of a lantern 7, which leads to the drive 14. A so-called clamping ring 9 acts as a connecting means between the second clamping flange 7a and the first clamping flange 1e, which is complementary to the first valve housing 1a.

The passage of the valve rod 2a* through the associated second valve housing 1b in connection with a second housing 5* and its design is analogous to the above description. The corresponding components are marked with an asterisk (*). In contrast to the first housing 5, the insert 8 is omitted in connection with the second housing 5*, the function of which, namely the fixing of the second rod seal 6a* and the second housing seal 11*, is taken over by the housing 5* itself.

The proposed innovation is implemented in a surprisingly simple manner in that, in the closed position of the double seat valve 1, the annular space 5a in the immediate vicinity of the first rod seal 6a sealing the valve rod 3a against the associated first valve housing 1a is directly connected to the leakage cavity 4 via at least one drainage line 10 formed within the valve rod 3a. In any position other than the closed position of the double seat valve 1, the outlet of the drainage line 10 on the annular space side remains in the annular space 5a. In the closed position of the double seat valve 1, this outlet is located at the lowest point of the annular space 5a, so that it can be completely emptied into the leakage cavity 4 and from there via the connecting holes 2d and the drain hole 2c into the area around the double seat valve 1. 30

When flushing the annular space 5a with cleaning and/or disinfectant, part of it also reaches the drainage line 10, so that this

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is subjected to sufficient cleaning and/or disinfection. The division of the flushing agent flow supplied via the inlet connection 5b into a first flow which leaves the outlet connection 5c and a second flow which flows out via the drainage line 10 depends on the ratio of the respective pressure losses of these flow paths.

The direct connection of the first annular space 5a with the leakage cavity 4 makes it possible to flush the first annular space 5a independently of the flushing of the leakage cavity 4 via the annular gap 13. However, it is also possible to let the drainage line 10 flow into the annular gap 13, whereby the first annular space 5a is indirectly connected to the leakage cavity 4. In this case, flushing the first annular space 5a and the leakage cavity 4 independently of one another is not possible.

In the event that the second annular space 5a* is to be completely emptied under the necessary conditions, i.e. in the case of an overhead arrangement, a second drainage line 10* (not shown) would have to be provided, which connects the second annular space 5a* in the immediate vicinity of the second rod seal 6a* to the drain hole 2c, preferably by the shortest route. However, this makes no sense in the case of the given double seat valve 1, since the necessary kinematic requirements are not met in the given closing element configuration, namely that the valve rod 2a* executes a lifting movement leading out of the second valve housing 1b at its sealing point during the opening movement of the double seat valve 1.

Claims (2)

1. Double seat valve with a flushable valve rod passage on the valve housing, equipped with two closing elements arranged in series and movable relative to one another, which in the closed position of the valve prevent fluids from flowing over from one valve housing part to another, and which in both the closed and open positions delimit a leakage cavity which has at least one connection path to the surroundings of the valve, with a first, independently driven closing element which, during its opening movement, comes into contact with a second one and also moves this into the open position, with valve rods for the closing elements which are led either on one side through the associated valve housing part or through the valve housing part assigned to the respective closing element and out of it, and with an annular space which is formed between a housing adjoining the valve housing on the outside and the valve rod which is led through and out of the valve housing and which is connected to the surroundings of the valve via an inlet and an outlet connection, characterized in that the valve rod ( 3 a) during the opening movement of the valve at its sealing point with the respective valve housing ( 1 a) executes a lifting movement leading out of the latter, and that in the closed position of the valve the annular space ( 5 a) in the immediate vicinity of a rod seal ( 6 a) sealing the valve rod ( 3 a) against the associated valve housing ( 1 a) is directly or indirectly connected to the leakage cavity ( 4 ) via at least one drainage line ( 10 ) formed within the valve rod ( 3 a). 2. Double seat valve according to claim 1, characterized in that the valve rod ( 3 a) in the region of its sealing passage through the valve housing ( 1 a) is designed as a compensating piston ( 3 b) which is shaped to largely compensate for pressure forces exerted on the closing member ( 3 ) by the fluid present in the valve housing ( 1 a).