LU82962A1 - IMPROVEMENTS IN LEVEL DETECTION DEVICES AND METHODS - Google Patents

Description

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* ’BL-3019 / EM / BM

Claim of priority of a jV patent application filed in Belgium on December 3, 1979 / ‘under No. 880.407 /" C. 1999/7912.

»Your METALLURGICAL RESEARCH CENTER -CENTRUM VOOR RESEARCH IN DE METALLURGIE,

Nonprofit organization -

Vereniging zonder winstoogmerk, in BRUXELLES, (Belgium).

Improvements to level detection devices and methods.

I 1

The present invention relates to improvements to a device for detecting the level of a liquid bath Ä in a container, in particular a bath of molten steel in an intermediate basket for continuous casting.

In a previous application, a method of detecting the level of a liquid bath in a container has been proposed, based on the measurement of the Archimedes thrust to which a bar immersed in this bath is subjected. More precisely, we measure according to this previous process, the buoyancy Archimedes • that exerts on a stopper a steel bath contained in a basket 2 * intermediate continuous casting and in which said stopper rod is immersed. This measurement makes it possible, by an adequate regulation loop, to modulate the steel flow rate so as to maintain in the basket a substantially constant level of metal.

The object of the present invention is to provide an appropriate sensor making it possible to continuously detect the Archimedes' pressure experienced by the submerged body and consequently the level of the liquid in the container.

Another object of the invention is to provide a level detection device whose response time is very short and makes it possible to follow, almost instantaneously, any variation of said level.

The device for detecting the level of a liquid in a container, object of the present invention, which comprises a rod immersed in said liquid and connected by an arm to a support integral with said container, and a sensor for measuring the thrust of Archimedes undergone by the said bar, is essentially characterized in that the said sensor consists of a pneumatic system and an apparatus for measuring the pressure prevailing in the said pneumatic system.

According to a preferred embodiment of the invention, said sensor consists of a pneumatic cylinder, equipped with a system for pressurizing the gaseous fluid and of a> device for measuring the pressure applied to said gaseous fluid.

In the present description, reference will be made more particularly to the use of compressed air.

It goes without saying, however, that the use of other gaseous fluids, for example compressed nitrogen, is by no means excluded.

The present invention also relates to a method of implementing the device which has just been described.

j The process which is the subject of the present invention .. jr * "" * r 3 tion is essentially characterized in that the pressure applied to the gaseous fluid is measured under the combined action of the self-weight of the arm system -bar and the Archimedes push suffered by the said bar, and in that we deduce the level of liquid in the container.

According to a preferred embodiment, an initial pressure is applied to the gaseous fluid and the "variation of the pressure in the pneumatic system is measured when the buoyancy increases with the level of the metal.

A particularly advantageous variant of implementing the method of the invention consists in using a pneumatic jack of the "bellows" type working under load in its static position, that is to say in its natural position in the absence of load and pressure.

This type of actuator works in such a way that its active member always occupies the same position, whatever the effort it supports. Any variation in this force requires a corresponding variation in the pressure applied to the jack, so as to maintain the active member in its static working position. The relationship between the pressure to be applied and the force exerted depends on the geometry of the cylinder and is provided by the manufacturer.

With this in mind, it has proven advantageous to dimension the system in such a way that in the absence of any Archimedes push, the initial pressure applied to the gaseous fluid brings the pneumatic cylinder to its static position and the supporting arm. the bar - in a horizontal or substantially horizontal position.

Under these conditions, when the bar is subjected to a certain Archimedes thrust, the force exerted by the jack decreases and it is necessary to reduce the pressure applied to the gaseous fluid, in order to maintain the jack in a static position and the arms in horizontal position.

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To this end, it has proved to be advantageous to use a device such as a servo valve.

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4

A preferred embodiment of the invention will now be described, with reference to the appended figure, which represents a system for detecting the level of the metal in an intermediate basket for continuous casting.

The device shown in the figure comprises an intermediate basket for continuous casting 1 in which a stopper 4 made of refractory material is immersed. This stopper rod is fixed to an arm 5 articulated at 3 to the support 2 secured to the basket. The level detection system according to the invention consists of a pneumatic cylinder 6, of the bellows type, disposed between the support 2 and the arm 5, in the vicinity of the joint 3. In the rest position, the arm 5 is supported on a stop 7 fixed to the support 2.

To put the device into service, in the absence of any Archimedes push on the stopper rod. 4, a pressure is applied to the gaseous fluid such that the force exerted by the jack on the arm 5 lifts the latter and brings it into a horizontal position; the cylinder is adjusted so as to be, at this time, in its static working position. The feeler of the servo valve 8 is in contact with the arm 5. When the metal level rises in the basket, Archimedes' push tends to lift the arm 5, which breaks contact with the feeler of the servo valve 8 The latter reacts and reduces the pressure applied to the jack 6. The force exerted by the jack 6 on the arm 5 decreases and the arm 5 can thus be brought back to the horizontal. The decrease in pressure applied to the cylinder 6 is measured by the pressure gauge 9, which can therefore express a measure of the variation in the level of the metal in the basket.

The valve 10 supplies the system with compressed gas. An auxiliary pneumatic system (not shown in the figure) allows the introduction and removal of the pneumatic measurement system.

As indicated in the previous proposal from the same applicant, it is possible, in addition to the pressure gauge 9, to provide a device (not shown in the figure) delivering an electrical signal which makes it possible to modulate the emptying operation of the feed bag f jp . ' 5 "ration and / or to ensure the control of the continuous casting operation.

It goes without saying that the invention is not limited to the embodiments described here, but that it also covers any equivalent technical solution which respects the spirit thereof.

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Claims (7)

1. Device for detecting the level of a liquid in a container, in particular liquid steel in an intermediate basket for continuous casting, in which a rod immersed in said liquid is integral with an arm connected by an articulation to a support fixed to said container, a force sensor being interposed between said arm and said support, characterized% in that said sensor consists of a pneumatic system and an apparatus for measuring the pressure prevailing in the says pneumatic system. 2. Device according to claim 1, characterized in that the pneumatic system is a pneumatic cylinder acting vertically on the said arm, and in that it comprises a system for adapting the pressure of the gaseous fluid. 3. Device according to either of Claims 1 and 2, characterized in that the pneumatic cylinder is of the so-called "bellows" type, working under load in its static position, and in that it is associated with a servo valve intended to adapt the pressure so that the cylinder works in its static position. 4. Method for implementing the device “according to either of claims 1 to 3, characterized in that the pressure applied to the gaseous fluid is measured under the combined action of the self-weight of the arm-bar assembly and the Archimedes push undergone by said bar, and in that one deduces the level of the liquid in the container. 5. Method according to claim 3, characterized in that an initial pressure is applied to the gaseous fluid, in that the variation of the pressure in the pneumatic system is measured under the effect of the variation of the thrust d 'Archimedes. applied to the bar by the liquid, and in that one deduces therefrom “9 the variation of the level of the liquid in the container. 6. Method according to claim 5, characterized in that an initial pressure is applied to the gaseous fluid such that the force applied to the arm by the jack brings said arm to a horizontal or substantially horizontal position. 7. The method of claim 6, charac- _ = ‘terized in that if the cylinder is of the type called" bellows ", it is in its static position when the arm is in a horizontal or substantially horizontal position. ^ "! Te! j