CA1043660A

CA1043660A - Oil pressure tank

Info

Publication number: CA1043660A
Application number: CA277,231A
Authority: CA
Inventors: Basil J. Head
Original assignee: Pirelli General Cable Works Ltd
Current assignee: Pirelli General Cable Works Ltd
Priority date: 1976-05-06
Filing date: 1977-04-28
Publication date: 1978-12-05
Also published as: AU504235B2; IE44816L; ES458682A2; IT1115459B; GB1513591A; JPS52135086A; ZA772215B; IE44816B1; AU2426477A; BR7702861A

Abstract

ABSTRACT OF THE DISCLOSURE

An oil pressure tank for use in a volume-compensating capacity in a pressurised oil system, particularly a system of oil-filled electric cables, comprises a vessel for receiving the oil and a stack of gas-filled cells within the vessel: each cell comprises two parallel plates each formed with a plurality of concentric annular corrugations, the cells being disposed with respective plates of adjacent cells in face-to-face contact with each plate of each cell having its corrugation peaks aligned with the corrugation peaks of the contacting plate of the ad-jacent cell; at least one plate of each contacting pair has the peaks of at least certain corrugations varying in height around their circumferences so that, in the event of evacuation of the vessel, movement towards each other of each pair of contacting plates is limited by the higher-peak portions whilst at least one radial passage exists between that pair, from periphery to centre of the cells, over the lower-peak portions.

Description

04~6~0 Tl~e present inventio1l 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 ca~les The present invention is an improvement in or modification of the invention which is the subject of our British patent 1 358 o88.
In a sygtem of oil-filled electric cables, the cables are provided with longitudinal oil ducts and in ; 10 service these ducts are connected to external sealed tanks containing degasified oil under pressure Some such cable systems are liable to suffer from the de$asified oil having ; ~ an undesirably high residual gas pressure and one of the actors leading to this pressure i9 gas-containing oil within - ~ prcssure tanks ' Known pressure tanks compr~se a vessel communicating with the cable oil ducts and containing a stack of flexi~le-walled cells filled with gas at atmocpheric or higher pressure ~;~; (dep-nding on the intended application of the tank), the ~ cells being disposed with ad~acent pairs in face-to-face alignment. In use, when the volume of oil in the tank vessel ~ increases due to expansion of *he oil in the cable system J~ on rl-- in temperature, the cells are compressed and vic~
~ ;; ~ers- on contraction of th oil The cells thus act as i~ 25 res-rvoirs for accommodating the volume variations of the oil and in this ~ay the oil pressure is kept within pre_ determined limits ,~
;~ uring manufacture, the pressure tanks are su~S-cted to vacuum treatment prior to filling ~ith de-gasified oil The faces of the cells are corrugated or~

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-10~ 0 other~ise shap~d to improve thcir flexibilit~, and t~e opposed races Or adjacent cells tend to lock ~o~ether ~hen the vacun~ is applied, with the tendenc~- for isolated air pockets to become entrappod bet~een the intcrl.ockcd cell faces. ~ese air pockets cannot be e~sily evacua~ed and subsequently once the tank has been filled witll oil, the air gradually dissolves into the de~asified oil over a period of ti~e and the residual gas pressure in the oil rices.
This problem is more acute ~ere the gas ~eithin the cells is under pressure; as the cell-pressure incre.ases so . . does the interfacial pressure between adjacent cclls ~hich occurs upon evacuation. Indeed evidence exists to show that increa es in cell-pressure lead to increa~es in thc resulting residual gas pressure in the oil.
The problem of residual gas pressurc can be overcome by prolonged oil recirculation througll a dcg~sifier but this is costly to the ma~ufacturer.
. . From one aspect, the invention which is the subject ~ of our British Patent 1 358 o~8 provides an oil pressure tank comprisirg a vessel for receiving oil under pressure and containin~ a 6tack of cell8 filled with gas and disposed ..
~ ith adjacent cells in face-to-face alignment, the faces of ,.
. . fiaid cells being formed with projections to facilitate the escape of gas from substantially the whole Or the region . between each pair of adjacent cells in the event of e~aouation of the vessel.
The present invention~ being an i~provement in or modification Or the invention uhich is the subject of our 30: British Patent 1 358 o88 , provides an oil pressure tan~

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104;~660 comprising a vessel 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 celis 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 move-, I ment towards each other of each pair of contacting plates; 15 is limited by contact of the pair of plates at the higher-peak portions of said certain corrugations, whilst at least one generally radially extending pa~sage exists ~ between each pair of contacting plates, from the periphery :~l of the cells to the axis of the stack, over the lower-~ 20~ ~ :peak portions of said certain corrugations.
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An embodiment of the present invention will now ;l - 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;
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FIGURE 2 is a plan view, on an enlarged scale, of a gas cell, showing the corrugations over only a part of the circumference; and FIGURE 3 is a cross section, on a further : enlarged scale, through a gas cell.
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10436~0 Referring to the drawings, an oil ~)ressure tank (Figure 1) comprises a vessel 10 for receiving the oil and a stack of cells 12, each cell bcing filled with gas and sealed. Adjacent cells are in face-to-face alignment. Each cell ~see Figure 3) comprises two circular sheet metal plates 12a, 12b, each having a cylindrical skirt 12c, 12d 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 3, the thick-ness of the sheet metal of which the plates are formed and the height of the corrugations are shown exagger-- atedly large. The cell also includes a supporting ring 15 within and adjacent the inner skirt 12d.
The two plates of each cell are formed with a plurality of concentric annular corrugations 14, and a central portion 16 which is flat. In the embodiment shown, the 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 18, spaced at 90 around the corrugations, and each zone 18 includes three radial sub-zones 18a, 18b, 18c for which the peaks are raised, these sub-zones being separated by two narrower sub-zones ZOa, 20b 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 ` ............ . ... ~ . -: . .

~0436f~0 each adjacent pair of cells will move towards e~ch other and the higher-peak portions of the pair of 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 al60 the entire sector between ; .
- 10 adjacent main zones will provide a passage to the centre of the cell. All of these.passages will com--~ municate with all of the corrugations and accortingly ~ .
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: th- escape of gas from between~adjacent.cells will be facilitated.
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.15 ~ In~tead of the corrugation regions 18a, 18b, ~.
lôc being of greater peak height than the ~eneral height ~:
of the corrugations, they may be of lesser height, so ~ .
that.the facing plates of adjacent cells will come into cont-ct over the general stretches of the corrugations 20~ and~over th~e narrow~sub-zones 20a, 20b, whilst the sub-zones:~18a~ 18b~ lôc will provide the radial passages for~escape of gas. :
Any convenient number of radial main zones 18 ~ .may be provided, with any ~convenient number of radial ; ~ ~25:~ s`ub-zones~in each~main zone.:
. s~ Another modification would be for only certain ;~ one ,;for example alternate ones, of the corrugations :~ to~be formed with raised-peak regions. In one particular arrangement, one or more of the corrugationc might be :~ raised in peak height for the full circumference, apart - 6 - .
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:, lQ43660 from one or two small regions of lesser height ~hich 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 ~hilst the other is formed of corrugations all of a constant height.
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Claims

WHAT WE CLAIM IS:

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 com-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 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 movement towards each other of each pair of con-tacting 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 extending passage exists between each pair of contacting plates, from the periphery of the cells to the axis of the stack, over the lower-peak portions of said certain corrugations.

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

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 sub-zones.

6. An oil-pressure tank as claimed in any one of claims 3 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 com-prises a radially extending zone.

9. An oil-pressure tank as claimed in claim 1 or 2 or 3, in which each said plate comprises a central portion which is flat.

10. An oil-pressure tank as claimed in claim 1 or 2 or 3, in which each said plate includes a cylindrical skirt turned down therefrom around the periphery, the skirts of the two plates of each cell interfitting.