IE44816B1 - Oil pressure tank - Google Patents

Abstract

1513591 Hydraulic accumulators PIRELLI GENERAL CABLE WORKS Ltd 8 Feb 1977 [6 May 1976] 18653/76 Addition to 1358088 Heading F1D In an improvement in the accumulator of the Parent Patent each gas-filled cell comprises a pair of plates having annular corrugations, some or all of the corrugations varying in height around their periphery so that when two cells are placed face to face the corrugations of the respective plates coincide and also provide a generally radial path from the centre to the periphery of the cells for the escape of any gas trapped between the cells. Thus some or all the corrugations may have raised portions, or all the corrugations may have depressed portions. The raised and/or depressed portions may be located in one or more radial zones.

Description

The present invention relates to an oil pressure tank for use in a volume-compensating capacity in a pressurised, oil system, particularly a system of oil-filled electric cables.

The present invention in an improvement in or modification of the invention which is the subject of Patent Specification No. 36828.

In a system of oil-filled electric cables, the cables are provided with longitudinal oil ducts and in service these ducts are connected to external sealed tanks containing degasified oil under pressure. Some such cable systems are liable to suffer from the degasified oil having an undesirably high residual gas pressure and one of the factors leading to this pressure is gas-containing oil within the pressure tanks.

Known pressure tanks comprise a vessel communicating with the cable oil ducts and containing a stack of flexiblewalled cells filled with gas at atmospheric or higher pressure (depending'on the intended application of the tank), the cells being disposed with adjacent pairs in face-to-face alignment. In use, when the volume of oil in the tank vessel increases due to expansion of the oil in the cable system or rise in temperature, the cells are compressed and vice versa on contraction of the oil. The cells thus act as reservoirs for accommodating the volume variations of the oil and in this way the oil pressure is kept within predetermined limits.

During manufacture, the pressure tanks are subjected to vacuum treatment prior to filling with, degasified oil.

The faces of the cells are corrugated or otherwise shaped 4481c to improve their flexibility, and the opposed faces of adjacent cells tend to lock together when the vacuum is applied, with the tendency for isolated air pockets to become entrapped between the interlocked cell faces. These air pockets cannot be easily evacuated and subsequently once the tank has been filled with oil, the air gradually dissolves into the degasified oil over a period of time and the residual gas pressure in the oil rises.

This problem is more acute where the gas within the cells is under pressure; as the cell-pressure increases so does the interfacial pressure between adjacent cells which occurs upon evacuation. Indeed evidence exists to show that increases in cell-pressure lead to increases in the resulting residual gas pressure in the oil. Λ IS The problem of residual gas pressure can be overcome by prolonged oil recirculation through a degasifier but this is costly to the manufacturer.

From one aspect, the invention which is the subject of Patent Specification No. 36828, provides an oil pressure tank comprising a vessel for receiving oil under pressure and containing a stack of cells filled with gas and disposed with adjacent cells in face-to-face alignment, the faces of said cells being formed with projections to facilitate the escape of gas from substantially the whole of the region between each pair of adjacent cells in the event of evacuation of the vessel.

The present invention, being an improvement in or modification of the invention which is the subject of Patent Specification No. 36828, provides an oil pressure tank - 3 ^44816 .=,- -comprising a v.esse-l for receiving oil under”pressure and containing a stack of cells each filled with gas, each cell comprising two generally parallel plates each formed with a plurality of concentric annular corrugations, the cells being disposed with respective said plates of adjacent cells in face-to-face contact, each said plate of each cell having its corrugation peaks aligned with the corrugation peaks of the contacting plate of the adjacent cell, and at least one plate of each contacting pair of plates having at least certain corrugations the peaks of which vary in height around the circumference thereof, the arrangement being such that, in the event of evacuation of the vessel, the movet ment towards each other of each pair of contacting plates is limited by contact of the pair of plates at the higherpeak portions'of Said certain corrugations, whilst at least one generally radially extending passage exists between each pair of contacting plates, from the periphery of the cells to the axis of the stack, over the lower20 peak portions of said certain corrugations.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 is a side view of a pressure tank, partly cut away; FIGURE 2 is a plan, view, on an enlarged scale, of a gas cell, showing the corrugations over only a part Of the circumferencej and FIGURE 3 is a cross section, on a further enlarged scale, through a gas cell. - 4 44816 Referring to the drawings, an oil pressure tank (Figure l) comprises a vessel 10 for receiving the oil and a stack of cells 12, each cell being filled with gas and sealed. Adjacent cells are in face-toface alignment. Each cell (see Figure 3) comprises two circular sheet metal plates 12ei, 121a, each having a cylindrical skirt 12c_, 12ti turned down therefrom around the periphery. The skirts of the two plates interfit and the cell is sealed by welding around the edge 13 of the outer skirt. In Figure 3i the thickness of the sheet metal of which the plates are formed and fhe height of the corrugations are shown exaggeratedly large. The cell also includes a supporting ring 15 within and adjacent the inner skirt 12ci.

The two plates of each cell are formed with a plurality of concentric annular corrugations l4, and a central portion l6 which is flat. In the embodiment shown, fhe corrugation peaks (pointing outwards of the cell) of all corrugations are locally raised at certain regions. These regions are arranged as four main radial zones l8, spaced at 90° around the corrugations, and each zone l8 includes three radial sub-zones l8ja, l8t>, l8£ for which the peaks aro raised, these sub-zones being separated by two narrower sub-zones 20a^, 20(b for which the peaks are of the same height as for the portions between the main zones. The peaks of successive corrugations of'the facing plates of adjacent cells are aligned·, i.e. at the same successive radii.

Accordingly, in the event of evacuation of the vessel, the cells will all expand. The facing plates of - 5 44816 each adjacent pair Of cells will move towards each ι , 1 other and the higher-peak portions of the pair of 1 facing plates will contact to limit further approach of these plates. However, passages will exist, radially of the-cells and between the facing plates of adjacent pairs of cells, from the periphery of the cells to the centre. Specifically, passages.will exist along the two narrow sub-zones 20a, 20b of each main zone, and also the entire sector between adjacent main zones will provide a passage to the centre of the cell. All of these, passages will communicate with all of the corrugations and accordingly the escape of gas from between adjacent cells will be facilitated.

Instead of the corrugation regions l8a, l8b., l8c. being of greater peak height than the general height of the corrugations, they may be of lesser height, so that'the facing plates of adjacent cells will come into contact over the general stretches of the corrugations and over the narrow sub-zones 2Oja, 20b, whilst the subzones l8ei, l8b, l8_£ will provide the radial passages for escape of gas.

Any convenient number of radial main zones l8 may be provided, with any convenient number Of radial sub-zones in,each main zone.

Another modification would be for only certain ones, for example alternate ones, of the corrugations to be formed with raised-peak regions. In one particular arrangement, one or more of the corrugations might be raised in peak height for the full circumference, apart - 6 i j — ' ') from one or two small regions of lesser height which provide passages for the escape of gas.

Also, of each facing pair of plates of adjacent cells, one may be formed with varying-height corrugations whilst the other is formed of corrugations all of a constant height.

Claims (11)

1. An oil-pressure tank,' comprising a vessel for receiving oil under pressure and containing a stack of cells each filled with gas, each cell com5 prising two generally parallel plates each formed with a plurality of concentric annular corrugations, the cells being disposed with respective said plates of adjacent cells in face-to-face contact, each said plate of each cell having its corrugation peaks 10 aligned with the corrugation peaks Of the contacting plate of the adjacent cell, and at least one plate of each contacting pair of plates having at least certain corrugations the peaks of which vary in height around the circumference thereof, the arrangement being 15 such that, in the event of evacuation of the vessel, the movement towards each other of each pair of contacting plates is limited by contact of the pair of plates at the higher-peak portions of said certain corrugations, whilst at least one generally radially 20 -extending passage exists between each pair of contacting plates, from the periphery of the cells to the axis of ihe stack, over the lower-peak portions of said certain Corrugations. (

2. An oil-pressure tank as claimed in claim 1, in 25 which the peaks of said certain corrugations are locally raised at certain regions. - 8 448lg

3. · An oil-pressure tank as claimed in claim 2, in which said certain regions are arranged as at least one radial zone in each said plate.

4. An oil-pressure tank as claimed in claim 3, in which each said radial zone includes a plurality of radial sub-zones over which said certain corrugation peaks are locally raised, adjacent sub-zones being separated by a radial sub-zone in which said certain corrugations have peaks lower in height than over said raised sub-zones.

5. · An oil-pressure tank as claimed in claim 4, in which each main radial zones includes three said raised sub-zones.

6. An oil-pressure tank as claimed in any one of claims β to 5, in which said certain regions are arranged as four main zones in each plate.

7. - An oil-pressure tank as claimed in claim 1, in which the peaks of all said corrugations in each said plate are locally reduced at least at one region.

8. An oil-pressure tank as claimed in claim 7, in which said at least one region over which all corrugation peaks in each plate are reduced comprises a radially extending zone.

9. - An oil-pressure tank as claimed in any one of the preceding claims, in which each said plate comprises a central portion which is flat. J ‘ 4481®

10. An oil-pressure tank as claimed in any one of the preceding claims, in which.each said plate includes a cylindrical skirt turned down therefrom around ihe periphery, the-skirts of the 5 two plates of epch cell interfitting.

11. An oil-pressure tank substantially as herein described with reference to the accompanying drawings. 1