Short lift valve

Details Short lift valve Short lift valve

1999-03-12

2001-09-25

Shaver, Kevin (Department: 3754)

Valves and valve actuation

Reciprocating valve

C251S333000

Reexamination Certificate

active

06293518

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a lift valve in accordance with the preamble of claim
1
.
In relatively large installations, lift valves are used almost exclusively with a flange casing. In the flange casings, the connection sides of the casings are provided with protruding flange plates which have a sealing face and interact with corresponding counter-flanges located on the pipeline elements to be connected. Sealing elements are arranged between the flanges in the region of the sealing faces, screw elements which penetrate the flange plates producing the necessary prestressing forces for a sealing connection. In order to ensure that the screw elements can be accessed, the flange plates are arranged exposed on the lift-valve casing. The significant advantage of such lift valves with flange elements is also that easy replacement is possible when required. By loosening the screw elements, the lift valve can simply be pulled out between the flanges of the adjacent pipelines and installed between the flanges and sealed again in the same way.
So that installation manufacturers can be equipped with respectively suitable fittings for various applications, there are further casing designs. In the case of sleeve valves, pipeline ends are screwed or soldered into the sleeves. In the case of other valve designs, the connections are designed as welding ends to be welded to associated pipeline ends in a fluid-tight fashion. The effort for the installation and removal of such valves is considerably greater. Owing to the different design series, these various designs require a large logistical outlay both on the part of the manufacturer and on the part of the customer.
GB-A 1 359 755 shows a lift-valve design which is intended to allow costs to be reduced and to involve a reduced material outlay and reduced processing effort as well as a simple design. For this purpose, a valve is proposed in whose tubular casing a cylindrical passage is provided. This passage serves to receive a replaceable cylindrical insert which abuts against a shoulder within the tubular casing. The insert contains flow conducting paths for a fluid which is to be blocked off and a valve seat and requires positioning elements which can be used to align its position within the casing precisely and hold it in this position. In a corresponding way, a cap, in which a replaceable insert, which receives the activation elements of a valve stem, is mounted, is arranged in the outer cylindrical casing of the valve. This solution is suitable both for valve casings which are clamped in between flanges and for casings which are equipped with flange plates. In comparison with a conventional valve, this design is however considerably more expensive since, owing to the casing which is complicated to fabricate, and to the additional insert, the processing outlay is substantially greater than that for cast valve casings. In addition, the material-removing processing of the inserts give rise to serious material losses, and, as a result of the inserts, connection points arise which also have to be sealed and at which corrosion problems may occur under certain circumstances. Furthermore, this valve has a comparatively large overall length. Therefore, long screw bolts are required for the clamping in procedure. Said screw bolts give rise to significant handling disadvantages, since a large amount of space is required to remove and install the valve, and this is not available in many installation situations.
Existing standards define the overall lengths of the lift valves. In principle, a lift valve comprises a casing region, which contains a movably arranged closure element, and has an associated valve seat in a dividing wall. Flange plates are arranged on both sides of this casing region using junctions. A medium flowing linearly to a lift valve through a pipeline is deflected, after passing through the first flange in the junction region, in order to pass a valve seat with associated closure element and be directed from a casing junction region lying opposite in the axial direction again to the continuing pipeline. Such a wave-shaped path through a lift valve with vertically arranged stem inevitably increases the overall length of the valve casing and causes flow losses, for which reason lift valves usually have a high flow coefficient &xgr;. Said coefficient is usually of the order of magnitude of approximately 4.
Different designs have been developed in order to obtain flow coefficients which are more advantageous for lift valves. One of these designs are so-called slanted seat valves, in which the flow path between the connecting flanges is as linear as possible, into which flow path a closure element which is arranged obliquely thereto dips. The disadvantage of such a design is the oblique course of the valve stem. Depending on the installation position, such a lift valve can be less convenient to use, is more difficult to insulate and has a large overall length.
A lift valve with low flow losses, an advantageous &xgr; value of approximately 1.2 and a shorter overall length is the KSB development BOA-Compact, which has made a shorter overall length possible than is the case with traditional lift valves with a valve stem which is arranged perpendicularly with respect to the pipeline. The flange-type designs available on the market require respectively different design series for the different rated pressure levels. This requires a high logistical outlay on manufacture, storage and mounting.
DE-A 20 48 580 presents a valve design which is resistant to corrosive chemicals and has two different overall lengths. The lift valve is implemented in a mixed design, using standardized semifinished products made of special metals, in order to reduce the high costs of the special materials which are necessary. In this respect,
FIG. 1
shows a pure welded design, while
FIG. 5
shows a short design of the lift valve in which an external, cast housing made of a cheap material which comprises metal or plastic is used. This external housing is provided with a corrosion-resistant internal housing. In its dimensions, the internal housing corresponds, with its closure part and the functional elements which interact with it, to the corresponding parts of the housing design according to FIG.
1
. Thus, given two different designs, the manufacturing costs of the parts which are composed of special metals, can be reduced owing to the relatively large number of identical parts.
A round massive valve cone, which is pressed into an eliptical opening of a valve seat which is arranged obliquely in the housing, is intended, whatever its state of wear, to have a sealed termination at the edge of an elliptical opening which forms the valve seat. A prerequisite of this is a rotatable arrangement of the massive valve cone over its lifting range in order to come to bear against other parts of the seat face of the valve cone in each case.
The short valve design which is shown in FIG. 5 of DE-A-20 48 580 can be used only in conjunction with 4-hole flanges. In the case of relatively large flanges or when it is used in pipeline systems with relatively high pressures, which require flanges with more than 4 screwed holes to be used, the clamping-in design which is shown can no longer be used. This is because the flange screws which are used to hold the armature between two flanges cannot be guided past the housing in the region of the valve stem owing to the reciprocal hole for the round valve cone, said hole being located in the housing and running perpendicularly with respect to the through-flow direction. The overall length of the lift valve in FIG. 5 which has a short effect on first impression, is almost 60% larger than the corresponding nominal diameter.
The invention is based on the problem of developing a lift valve which reduces the aforesaid outlay and has a versatile field of application with low flow losses. The solution of this problem provides for a lift valve in accordance with the invention as described hereinafter. The advantages of th

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