WO2014202630A1

WO2014202630A1 - Mechanical sensor of the level of fill of a cavity, and method for measuring fill level using such a mechanical sensor

Info

Publication number: WO2014202630A1
Application number: PCT/EP2014/062757
Authority: WO
Inventors: Wolfgang Klaas; Rémi NIEBORAK; Kevin VIKTOR
Original assignee: Tmt - Tapping Measuring Technology Sàrl
Priority date: 2013-06-18
Filing date: 2014-06-17
Publication date: 2014-12-24
Also published as: LU92225B1

Abstract

The invention relates to a mechanical sensor (2) of the level of fill of a cavity (10), for example, a blast furnace, which is mounted on a fixed flange (12) provided on a dome (1) of the cavity (10). The mechanical sensor (2) includes a weight (3) suspended at the end of a chain (31) passing through the dome (11) of the cavity (10), and a winch (4) which includes a drum arranged to wind and unwind the chain (31) on the drum in order to cause the weight (3) to descend and ascend; and a means (40, 40') for controlling the drum to control the rotation or the stopping of the drum depending on the position of the weight (3). The winch (1) further includes a means for determining the length of the wound or unwound chain (31). According to the invention, the mechanical sensor (1) includes a force meter (5, 5') for detecting a decrease in the tension of the chain (31) when the weight (3) rests on a surface (S) of material loaded in the cavity (10). The meter (5) is mounted between the control means (40, 40') and a stationary mounting (22) that is rigidly connected to a drum casing. The control means (40, 40') of the winch (4) is rotatably mounted on the stationary mounting (22) by connecting means along a pivot axis (A) and by a rocker bar (45, 45') arranged at a distance from the pivot axis, the rocker bar (45, 45') including the meter (5) and the meter (5) being arranged such as to continuously measure the axial force applied on the rocker bar. The invention further relates to a method for determining the position of the level of material filled in a cavity and the variation in said position.

Description

Mechanical probe for loading level of a tank, and method of measuring the level of loading using such a mechanical probe

Technical area

The present invention relates to the determination of the level of loading of a tank, such as for example a furnace, a silo or a material hopper. The invention more particularly relates to a mechanical probe used to determine the altitude and speed of descent of the surface of a load in a blast furnace.

State of the art

The general principle of determining the level of loading in a tank, in particular in a blast furnace, is to measure the position of a suitable weight of shape to be able to rest freely on the load. This weight is suspended at the end of a chain or cable that takes slack when the weight, descended into the furnace, is able to rest on the load of material contained in the blast furnace. Subsequently, including in the claims, only the term "chain" will be used as a weight suspension means, it being understood that this term will be understood as being a chain, a cable or any other equivalent lifting element.

To this end, the known mechanical probes comprise a vertical tube mounted on the dome of the blast furnace and wherein the chain passes axially. At its upper end, the tube supports a motorized winch. The winch comprises a drum on which the chain is wound, and control means comprising a motor and a gearbox respectively a geared motor. The motor is a servomotor connected to the drum by a gear reducer. When the weight comes down, at the load, it rests on it and the slack that results in the chain is detected by the servomotor. The latter is then stopped and an encoder or position transmitter provided for this purpose to determine the chain length introduced into the blast furnace from a reference position corresponding to a maximum high position of the weight. It is thus possible to determine the height of the weight when it comes to rest on the load, and thus the altitude of the load in the blast furnace. A disadvantage of such a system is that it requires the use of a servomotor and that the detection of slack passes through a gears gear machined accurately.

[0005] Such systems with detection of slack are described for example in JP S56 142808 A, US 3,742,307 A, LU 59,418 A1 or EP 0 452 624 A1. These documents evoke systems operating by torque detection on a cable winding hoist system or suspension chain of a weight and measuring a length of chain unwound to detect a weight position when the one It comes to rest on the surface of the load. No. 3,500,546 A describes a system in which the slack is not detected by a torque variation, but by a tensioner.

[0006] ES 2 237 329 A1 discloses a substantially different system, in which a slack in a chain is not suspended from a weight, but the mass of the hanging portion of a chain whose weight of the end embedded in the load is supported by the load.

Object of the invention

An object of the present invention is to solve these problems and to propose an alternative solution to the use of a servomotor. Another object is to improve the accuracy of the measurement.

General description of the invention

With these objectives in view, the subject of the invention is a mechanical probe for the level of loading of a tank, for example a blast furnace, the mechanical probe being mounted on a fixed flange provided on a dome of the tank. The mechanical probe comprises a weight suspended at the end of a chain passing through the dome of the tank, and a winch which comprises a drum arranged to unroll or wind the chain on the drum to lower or raise the weight; and drum control means for controlling rotation or stopping of the drum in accordance with the position of the weight. The winch further comprises means for determining the unwound or rolled chain length. According to the invention, the mechanical probe comprises a force sensor for detecting a decrease in tension of the chain when the weight rests on a surface of material loaded in the reservoir. Thus, the variations of the tension exerted on the chain by the weight are directly measurable by the force sensor without the need to use a servomotor. In addition, the gear reducer can be replaced by a gear reducer machined less precisely.

The measurement of the tension force exerted on the chain is independent of any friction that may exist in the gearbox. Compared to systems with a servomotor, the invention makes it possible to economize the expensive apparatuses which are the servomotor, the frequency converter and the special cables required for the servomotor.

[001 1] The sensor is a force sensor mounted between the control means and a fixed support integral with a drum housing, the control means preferably comprising a motor and a gearbox - or a geared motor - for motor connection on the drum. The control means of the winch, preferably integrated in a control box, is pivotally mounted on the drum housing according to a pivot axis and by a rod arranged at a distance from the pivot axis, the force or force sensor. torque being arranged to continuously measure the axial force exerted on the link. Thus, the gearbox and the motor (or geared motor) are in fact pivotally mounted and the forces to which they are subjected, that is to say those resulting from its own mass and those resulting from the load transmitted to the chain by the weight , create a pivoting torque around the pivot axis, this torque being taken up by the rod connecting the control means to the fixed support. It is therefore sufficient to measure the axial tensile force, or compression, in said link, to evaluate the variations in the tensile force exerted by the weight suspended at the end of the chain, and in particular to immediately detect the decrease in this force. when the weight settles on the surface of material loaded in the tank.

The rod can be connected on one side to the control box pivotally mounted and on the other side to the fixed support. The force sensor can be a standard type torque sensor, with great precision and fidelity. Advantageously, the sensor will constitute in itself said link.

In one embodiment, the control means is located in a generally vertical position plumb with the pivot axis, and above this axis, the link extending substantially horizontally. An advantage of this embodiment is that the load due to the own weight of the control means comprising the motor and the gearbox (or geared motor) is essentially supported at the pivot axis, and the force at which the rod and the torque sensor are submissive is relatively weak, since it corresponds only to the forces transmitted by the chain.

In another embodiment, the control means is located in a generally horizontal position at the pivot axis, the link extending substantially vertically. In this case, the intrinsic mass of the control means comprising the motor and the gearbox (or geared motor) generates a relatively large pivoting torque of the winch, which is clearly greater than the torque generated by the weight suspended on the chain.

It should be noted that the horizontal or vertical arrangement of the control means represents only preferred embodiments and that any intermediate arrangement is also conceivable.

According to another particular provision, the winch motor is a two-speed motor. As will be seen later, this makes it possible to quickly move the weight at the beginning and at the end of the measuring cycle, between a high storage or standby position and the active position, where the weight rests on the surface of the loaded material. in the tank. On the other hand, the small displacements necessary for the measurement can be carried out at low speed, thus improving the measurement precision.

Advantageously, the drum may comprise a profile with two threads for winding the two-speed chain. Thus, even by not varying the speed of the motor, the movement of the weight can be done at two speeds.

The mechanical probe may comprise a vertical tube mounted between the winch and the fixed flange, the chain passing through said vertical tube. Such a vertical tube allows to locate the winch remote from the dome of the tank. This may be advantageous because of exposure to heat, or simply for access reasons.

The invention also relates to the method for determining the position of the level of loading of a tank, such as for example a blast furnace, and evolution of this position, using the mechanical probe according to one modes previously defined. For this, determining a reference position of the winch drum corresponding to a predetermined altitude of the weight. Then the winch is operated to lower the weight, the reeled chain length being measured. When the weight comes to rest on the surface of the material loaded in the tank, the resulting decrease in tension of the chain is detected by the force sensor and controls the stopping of the winch motor. The level of the load is then deduced from said predetermined altitude and the measured chain length unrolled at the time the engine is stopped.

According to a first variant, after determining the level, the weight is raised by means of the winch, in a predetermined waiting position, or a predetermined height, and, at predetermined time intervals or at the request, we again control the descent of the weight to perform a new measurement. We can repeat this operation as many times as desired.

According to a second variant, which makes it possible to continuously monitor the evolution of the level of the charge and its rate of descent into the tank, a tolerance range is first determined on the force measured by the sensor, between a minimum threshold. and a maximum threshold. For example, during a first descent of the weight, the motor is stopped when the force measured by the sensor reaches the minimum threshold, indicating that the weight is totally on the surface of the loaded material. Then, when, following a descent of the loaded material, the chain is again subjected to a pull exerted by the weight, and the force measured by the sensor reaches the maximum threshold, the winch is controlled in the direction of the descent of the weight, until the measured effort reaches the minimum threshold again. At each stop of the motor, the length of the unrolled chain is measured and the level of the load can be deduced therefrom.

Advantageously, the time elapsed between two measurements is simultaneously measured, and the rate of descent of the loaded material can thus be deduced therefrom.

Alternatively, instead of directly triggering the descent of the weight in response to the attainment of the maximum threshold, it is also possible to order a rise in weight over a predetermined distance, then lower the weight until the minimum threshold is reached, etc. . This variant makes it possible to release the weight each time out of contact with the loaded material, and thus to avoid any jamming of the weight in the loaded material. Preferably, the first descent and the subsequent ascent are performed with the high speed of the winch, and the descent with the load is performed at low speed.

Brief description of the drawings

Other features and features of the invention will become apparent from the description of two non-limiting embodiments presented below, by way of illustration, with reference to the accompanying drawings. These show:

Fig. 1: a radial section of the upper part of a blast furnace comprising a mechanical level probe of loading in a blast furnace;

Fig. 2: a view illustrating two typical arrangements possible for the sensor and the control means;

Fig. 3: a side view of the connection between the control means and the fixed support;

Fig. 4: a left view of the link of FIG. 3; and 5: a top view of the connection of FIG.

Description of a preferred execution

In the drawing of Figure 1, there is shown only the upper part of a tank 10, here a tank of a blast furnace, surmounted by a dome 1 1. The upper surface of the blast furnace charge is represented by the line S.

The mechanical probe 2 of the load level is mounted on a fixed flange 12 provided on the dome 1 January. It comprises a vertical tube 21 in which passes a chain 31 at the end of which is hung a weight 3. The chain 31 is wound on the drum (not shown) of a winch 4 fixed on an upper end of the tube 21 .

The drum of the winch 4 is rotated by a control means 40 comprising a geared motor 42. The control means 40 is pivotally mounted relative to the fixed support 22 along the axis A of rotation of the drum. The drum is arranged so that the unwound chain of the drum is substantially in the axis of the vertical tube 21. The chain length unwound or wound during the measurement is determined by an encoder, not shown.

The control means 40 comprises an arm 44 connected to the fixed support 22 by a rod 45 equipped with a torque sensor 5. Advantageously, the link may be constituted in itself by a commercial load cell.

Figure 2 illustrates two arrangements of the control means of the winch.

In the arrangement shown in continuous pattern, the control means 40 is arranged substantially vertically, with the geared motor 42 located above the pivot axis A, and the torque sensor 5 extending horizontally between the arm 44 and a fixed point on the fixed support 22.

In the arrangement shown in mixed pattern, the control means 40 'is arranged substantially horizontally, with the geared motor 42' located horizontally of the pivot axis A, and the torque sensor 5 's' extending vertically.

Before carrying out the measurement, the weight 3 is raised in the vertical tube 21 in a waiting position represented by 3a of Figure 1. To perform the measurement, the winch is controlled to unwind the chain. When the weight 3 comes to rest on the surface of the loaded material, as represented by 3b, the winch is no longer subjected to the force generated by this weight, which is detected by the dynamometric sensor 5. The measurement then takes place according to the one of the possibilities mentioned above. At the end of the measurement, the weight is raised to its waiting position 3a.

In order to calibrate the mechanical probe 2, the weight 3 can be moved to a calibration position as represented by 3c. Reference signs

10 tank 4 winch

1 1 dome 40, 40 'control means

12 fixed flange 42, 42 'geared motor

2 mechanical probe 44 arms

21 vertical tube 45 connecting rod

22 fixed support 5, 5 'dynamometric sensor

3 weight A axis of rotation of the drum 31 chain 5 surface of the loaded material

Claims

claims

1. Mechanical probe for loading level of a tank (10) such as for example a blast furnace, the mechanical probe being mounted on a fixed flange (12) provided on a dome (1 1) of the tank (10), the mechanical probe comprising a weight (3) suspended at the end of a chain (31) and a winch (4) comprising

a drum arranged to unroll or wind the chain (31) on the drum to lower or raise the weight (3),

control means (40, 40 ') of the drum for controlling rotation or stopping of the drum according to the position of the weight (3), and

means for determining the length of the chain (31) unwound or wound,

a force sensor (5) for detecting a decrease in tension of the chain (31) when the weight (3) rests on a surface (S) of material loaded into the reservoir (10), said sensor (5) being mounted between the control means (40, 40 ') and a fixed support (22) integral with a drum case

characterized in that the control means (40, 40 ') of the winch (4) is mounted on the fixed support (22) by rotationally connecting means along a pivot axis (A) and by a connecting rod (45, 45 ') arranged at a distance from the pivot axis, said rod (45, 45') comprising said sensor (5) and the sensor (5) being arranged to continuously measure the axial force exerted on the rod.

2. Mechanical probe according to claim 1, wherein the control means (40, 40 ') of the winch (4) is located in a generally vertical position in line with the pivot axis (A), the link ( 45) extending substantially horizontally.

3. Mechanical probe according to claim 1, wherein the control means (40, 40 ') of the winch (4) is located in a generally horizontal position at the pivot axis (A), the link (45' ) extending substantially vertically.

4. Mechanical probe according to any one of claims 1 to 3, wherein the sensor (5) is a load cell.

A mechanical probe according to any one of the preceding claims, wherein the drum control means (40, 40 ') comprises a two-speed motor.

The mechanical probe of any preceding claim, wherein the drum comprises a two-threaded profile for winding the two-speed chain.

7. Mechanical probe according to one of the preceding claims, characterized in that the control means (40, 40 ') comprises a geared motor (42, 42') or a motor and a gearbox for connection to the drum.

8. Mechanical probe according to one of the preceding claims, characterized by a vertical tube (21) mounted between the winch (4) and the fixed flange (12), the chain (31) passing in said vertical tube (21).

9. A method for determining the position of the level of material loaded in a tank such as for example a blast furnace and the evolution of this position, using the mechanical probe according to any one of the preceding claims, wherein

a reference position of the winch drum (4) corresponding to a predetermined altitude of the weight (3) is determined,

- The winch (4) is operated to lower the weight, the chain length (31) unwinding being measured; when the weight (3) comes to rest on the surface (S) of the material loaded in the tank (10), the decrease in tension of the chain (31) which results is detected by the sensor (5) effort , and controls the shutdown of the winch motor (4),

the level of the load being deduced from said predetermined altitude and from the measured chain length (31) unwound at the moment when the engine is stopped.

The method according to claim 9, wherein after determining the level, the weight (3) is raised by means of the winch (4), in a predetermined holding position or at a predetermined height and at intervals of predetermined time or on demand, the descent of the weight (3) is again ordered to perform a new measurement.

1 1. Process according to claim 9, wherein

a tolerance range is firstly determined on the force measured by the sensor (5), between a minimum threshold and a maximum threshold.

during a first descent of the weight (3), the motor is stopped when the force measured by the sensor (5) reaches the minimum threshold,

- when, following a descent of the loaded material, the chain (31) is again subjected to traction exerted by the weight (3), the force measured by the sensor (5) reaches the maximum threshold, the winch (4) ) is controlled in the direction of the descent of the weight (3), until the measured effort reaches the minimum threshold again, and at each stop of the motor, the length of chain (31) unwound is measured and deduces the level of the surface (S) of the loaded material.

12. The method of claim 1 1, wherein one simultaneously measures the time elapsed between two measurements, and deduced the rate of descent of the loaded material.

13. The method of claim 1 1, wherein, before controlling the winch (4) in the direction of descent, it controls a rise in weight (3) for a predetermined distance, then we go down the weight (3) until 'to reach the minimum threshold.

14. The method of claim 1 1, wherein the first descent and the subsequent ascent are performed with the high speed of the winch, and the descent with the loaded material is performed at low speed.