The invention relates to a pressure casing for a machine, especially for a turbomachine, which casing comprises a plurality of casing shell sections which are interconnected in a gastight manner.
In such a pressure casing, the casing shell sections have contact faces, which customarily are pressed against each other by means of a respective threaded connection outside the sealing zone, so that so-called parting joints are created between adjacent casing shell sections.
If three or more casing shell sections are to be interconnected at the same time, as exemplarily shown in
The prior art recognizes a plurality of solution proposals for sealing a cross flange with four casing shell sections which adjoin each other. The documents DE 27 55 356 or CH 625 025, as the case may be, disclose known solution proposals, according to which the parting joints of a pressure vessel, which extend in a cross-form manner, are sealed by means of a bolt in the intersection region of the parting joints. Welding of the abutting ends of the casing shell sections, as already known, is also described.
The use of a cover flange, which by means of a seal is sealed on a seating face which is incorporated in the casing shell sections, is described as new in the mentioned document.
All these known solution proposals, however, have disadvantages which counteract a reliable, maintenance-friendly, i.e. easily disassemblable and reassemblable, sealing of the cross flange:
The invention starts at this point. The invention, as it is characterized in the claims, deals with the problem of providing a reliable, non-destructively detachable seal for the intersection region of three or more parting joints for a casing of the type described in the introduction, in which the disadvantages of the known seals are avoided and, by constructionally simple measures, leaks are prevented during all operating conditions.
This problem is solved according to the invention by the subject of the independent claim. Advantageous embodiments are the subject of the dependent claims.
The invention is based on the general idea that a seat for a plug is provided on the outer faces of the casing shell sections in the intersection region of the parting joints, and that the plug is detachably fastened in this seat and is sealed in the plug seat by means of a permanently elastic, high pressure-resistant sealing compound.
Such a sealing of cross joints, which is formed according to the invention, is especially suitable for sealing steam turbine casings.
The invention is basically applicable for sealing the intersection region of three or more parting joints of a pressure casing, wherein both an overpressure and a vacuum can prevail in the interior of the casing.
An important advantage of the invention is now that the sealing plug is embedded in a quasi-floating manner in an elastic sealing compound under an overpressure. As a result of this, thermal distortions of the casing shell sections can be compensated without the sealing integrity being impaired. This is achieved by the sealing compound in its liquid, not yet set, state, being poured into the plug and then, by means of a pressure screw, being guided through suitable passages inside the plug to the actual sealing chambers. These sealing chambers, for example, are formed as annular grooves in the outer wall of the plug, and are preferably interconnected so that when pouring the sealing compound into the plug, all regions of the sealing chambers are exposed to through-flow one after the other and therefore no cavities are created in the sealing compound. This is also boosted due to the fact that the displaced air and a surplus amount of the sealing compound can escape from the plug through a vent hole from the sealing chamber which is last exposed to through-flow. By means of a suitable closure, like, for example, a threaded bolt, the vent hole can be sealed off and some of the sealing compound displaced back into the inside of the plug, wherein an overpressure is created in the sealing compound which presses the sealing compound into the sealing chambers against the plug seat and therefore creates a solid, elastic seal after hardening of the sealing compound.
The pressing action of the seal can be advantageously further augmented during operation of the turbomachine by a sealing compound being used which has a higher thermal volumetric expansion (beta coefficient in m3/m3K) than the material of the pressure vessel.
For securing the plug against a possible slipping out from its seat, the plug, by means of a plug flange which is preferably formed as an integral part of the plug, can be fastened on the casing shell sections, for example by means of screws. In this case, it is advantageous that the plug flange has no sealing function and therefore damage or thermal distortions of the flange seat on the casing shell sections do not impair the sealing function of the plug. To the person skilled in the art, however, other methods of fastening are also known, like, for example, caulking of the plug in its seat by means of a spring expanding ring or other mechanical locking devices.
A further advantage of the sealing of cross joints according to the invention is that, for maintenance or overhauling of the affected machine, the plug can be non-destructively removed and, after corresponding cleaning of plug and plug seat, the same plug can be reused without mechanical reworking being necessary on plug seat or plug. For this purpose, preferably 2 adjacent casing shell sections are opened, as a result of which the plug becomes accessible from the side and can be removed perpendicularly to its axis. With a suitable solvent for the sealing compound, the latter can be removed, free of residue, from the plug and from the plug seat on the casing shell sections, so that the plug can be used anew for sealing according to the invention by means of sealing compound.
Further important features and advantages of the seal according to the invention result from the dependent claims, from the drawings, and from the associated figure description, with reference to the drawings.
Preferred exemplary embodiments of the invention are shown in the drawings, and are explained in detail in the following description, wherein all like designations refer to the same components.
In the drawing,
The pressure casing according to the invention, which is partially shown in
In
The perspective drawing in
The intersection region (3) of the parting joints (2), with a plug (7) inserted, is shown in
After pouring the liquid sealing compound (19) into the plug (7), the pressure screw (16) is screwed into the filling hole (10) in the plug flange (8), and as a result the liquid sealing compound (19) is pressed into the plug (7) (
In
After the setting of the liquid sealing compound (19), as a result of this a reliable, elastic and disassemblable sealing of an intersection region (3) of the parting joints (2) on a pressure vessel is achieved, which maintains its sealing action even during thermal distortions of the casing shell sections (1). Within the scope of overhauling a turbomachine, the plug (7) can be removed in a problem-free and non-destructive manner after opening the casing shell sections (1). After the cleaning of plug (7) and plug seat (4) in the casing shell sections (1) by means of suitable solvents, the plug (7) can be used again during the reassembly of the turbomachine without, as a rule, the plug seat (4) in the casing shell sections (1) having to be reworked.
The embodiments which are shown here are purely exemplary and therefore without limitation of the generality, in particular the principle according to the invention of the cross flange sealing can also be used on 3, 5 or more casing shell sections which are to be sealed at a common point.
Number | Date | Country | Kind |
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1103/06 | Jul 2006 | CH | national |
Number | Name | Date | Kind |
---|---|---|---|
2677149 | Fineran | May 1954 | A |
3240379 | Bremer et al. | Mar 1966 | A |
3434743 | Boeker | Mar 1969 | A |
3726319 | Patterson | Apr 1973 | A |
3861646 | Douglas | Jan 1975 | A |
4044798 | Feldstein et al. | Aug 1977 | A |
4165080 | Adams | Aug 1979 | A |
5076311 | Marschke | Dec 1991 | A |
5143498 | Whitman | Sep 1992 | A |
5328300 | Fischer et al. | Jul 1994 | A |
5360302 | MacMartin | Nov 1994 | A |
6468010 | Sager et al. | Oct 2002 | B2 |
6902366 | Ducker et al. | Jun 2005 | B2 |
20040033120 | Ducker et al. | Feb 2004 | A1 |
Number | Date | Country |
---|---|---|
26 39 533 | Jun 1977 | DE |
27 55 356 | Jun 1978 | DE |
35 45 849 | Jul 1987 | DE |
2 335 786 | Jul 1977 | FR |
Entry |
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International Search Report dated Jul. 11, 2006 (with English translation of category of cited documents). |
European Search Report (with English language translation of category of cited documents) dated Nov. 5, 2007. |
Number | Date | Country | |
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20080012241 A1 | Jan 2008 | US |