Cleaning and liquid contact with solids – Apparatus – Sequential work treating receptacles or stations with means...
Reexamination Certificate
1999-07-02
2001-07-17
Stinson, Frankie L. (Department: 1746)
Cleaning and liquid contact with solids
Apparatus
Sequential work treating receptacles or stations with means...
C134S12200P, C134S200000
Reexamination Certificate
active
06260564
ABSTRACT:
The present invention relates to a device for closing an oblong tank containing a corrosive product, in particular an acid pickling tank for a strip-type product such as a metal sheet.
The metal strips produced in a rolling installation must normally undergo a pickling operation, in particular after hot rolling and before cold rolling, in. order to eliminate the oxide formed at their surface during hot rolling as well as other deposits or contaminations liable to nest into the sheet during cold rolling.
Generally, sheet pickling is performed while passing the metal strip through a series of tanks containing a hot sulphuric or hydrochloride acid solution. At each extremity of a tank, the strip passes over a threshold placed above the upper level of the acid bath, then is immersed into the said bath while forming a catenary loop up to the threshold placed at the other extremity of the tank. The strip must be stretched sufficiently to be immersed over a certain length inside the bath without increasing the height of the tank excessively.
Each tank must therefore be very long, for instance 20 to 30 meters with a constant width over its whole length, which depends on the maximum width of the strips thus treated.
A pickling bath consists therefore, generally, of a vessel exhibiting a rectangular bottom whose length is quite impressive with respect to its width, and a vertical lateral wall comprising two longitudinal faces and two transversal faces.
The installation generally comprises several tanks in succession and the assembly is placed inside a large-sized building. As the acid is hot, vapours are emitted, liable to corrode all the material placed above and around the tanks and must therefore be detected, then directed towards depollution units.
To this end, each tank is generally closed by a lid applied as tight as possible onto the upper rim of the lateral walls and connected to a suction means enabling to depressurise the inside of the tank as far as acceptable in relation to the outside, in order to prevent any leaks.
It is therefore necessary to guarantee tightness of the seal between the lid and the lateral side and, in this view, it is advantageous to use a so-called ‘water seal’ device, composed of a U-section gutter open upwards and filled with water, arranged along the upper rim of each longitudinal wall of the tank and in which a lateral rim of the lid is partially immersed.
However, because of the very great length of the tanks, it is necessary, in order to manipulate them, to cover each tank using several lids placed in. succession. Accordingly, it has seemed natural, up to now, to place water seals exclusively on the longitudinal walls of each tank, whereas tightness along each transversal sealing plane between two successive lids is ensured by rubber seals or any other sealing material, which are placed along adjacent transversal rims of both successive lids and overlap one another.
Similarly, at both extremities of each tank, the strip passes generally over a threshold or between rinsing rolls placed in a cover over which the corresponding transversal rim of the first or the last lid presses, via a sealing joint.
However, further to high corrosive power of acid vapours, the sealing joints wear rapidly and tightness is not always ensured perfectly, even if the seals are replaced periodically. Moreover, taking into account that the transversal seals between two successive lids overlap each other, they may deteriorate if the lids are not lifted in the correct order.
These deteriorations call for increasing the suction rate in order to maintain the inside of the tank depressurised with respect to the outside, but this increases air drafts at the surface of the bath, therefore evaporation and, consequently, vapour formation, as well as energy consumption of the line.
The invention aims at remedying these shortcomings thanks to new arrangements enabling better tightness over the whole circumference of each lid.
The invention relates therefore to a device for closing an oblong tank containing a corrosive product, whereas the said tank contains a rectangular bottom surrounded by a lateral wall with an upper rim and comprising two longitudinal sides and two extreme transversal sides delineating an upper aperture,
whereby the closing system comprises:
at least two successive lids extending respectively on either side of at least one sealing plane, whereas each lid has a lateral rim comprising two longitudinal sides and at least one transversal side extending along the sealing plane,
two longitudinal U-section gutters, arranged respectively along the upper rims of both longitudinal sides of the lateral wall of the tank,
at least one medial transversal gutter extending along at least one sealing plane between both longitudinal gutters,
whereby the said longitudinal and transversal gutters are filled with water,
whereby the longitudinal sides and at least one transversal side of each lid engage, upon closing, respectively into the said longitudinal and transversal gutters in order to constitute an efficient ‘water seal’ on at least three sides of the said lid.
Preferably, each longitudinal gutter is fitted, at each medial gutter, with an aperture enabling both gutters, respectively longitudinal and transversal gutters, to communicate, in order to provide a continuous water seal.
Usually, each tank is fitted, at each extremity, with a threshold above the bath, to allow passage of the strip, whereas the said threshold can consist of two superimposed rolls between which the strip passes so that the latter can be rinsed.
Particularly advantageously, such a threshold is covered with a cover along which is placed a transversal gutter linking with the corresponding extremities of both longitudinal gutters in order to establish tightness via a water seal on the four sides of each lid.
According to another advantageous characteristic, the medial transversal gutters can be fitted, at each extremity, with removable junction means with the corresponding side of each longitudinal gutter, in order to allow disassembly of the medial gutters if necessary.
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Bonhomme Henri
Sylvain Daniel
Arent Fox Kintner & Plotkin & Kahn, PLLC
Stinson Frankie L.
Vai Clecim
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