GB2028619A

GB2028619A - Apparatus for damping vibrations in an arc furnace

Info

Publication number: GB2028619A
Application number: GB7928695A
Authority: GB
Original assignee: BBC Brown Boveri AG Switzerland; BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Switzerland; BBC Brown Boveri France SA
Priority date: 1978-08-21
Filing date: 1979-08-17
Publication date: 1980-03-05
Also published as: BR7905316A; DE2837741A1; IT7924912A0; JPS5528489A; IT1122419B; FR2434545A1; SE7906831L

Abstract

A vibration damping apparatus for damping the vibrations of the electrodes in an arc furnace comprises at least one damping device associated with at least one of the electrodes and/or its support system. In the embodiment shown, a housing 3 is coupled to an electrode support arm 1 and contains an inertial mass 4 and fluid 6 communicating between the opposed ends of mass 4 through a passage 7 having a constriction 8. Alternatively the electrode vibrations may be sensed and used to control a vibrator to produce vibrations which cancel the electrode vibrations. <IMAGE>

Description

SPECIFICATION Apparatus for damping vibrations in an arc furnace The present invention relates to a vibration damping apparatus for improving the operation of an arc furnace comprising at least one electrode and at least one electrode support system.

It has been established that in arc furnaces the electrodes and electrode support systems e.g., support arms, will vibrate. The article "Schwingungsverhalten von Elektroden und Tragarmen in Lichtbogen6fen" (vibration behaviour of electrodes and support arms in arc furnaces) in Stahl und Eisen 98 (1978) No. 14, 1 3th July, page 695 ff., describes measurements which were used to determine the type and magnitudes of these vibrations. These vibrations will also result in fractures in the electrodes. In the abovementioned article it was determined that the highest acceleration values of the vibrations occur in the horizontal direction, at right angles to the axis of the support arm, and that in the case described the amplitudes go up to about 13 mm at frequencies of 2.4 Hz.

it is also known that vibrations of this type can cause voltage fluctuations in the electric mains supply.

It would be theoretically possible to modify these interfering vibrations by rigidly dimensioning the vibrating parts in such a way that their resonant frequency is far enough removed from the exciting frequencies. This method, however, would lead to larger, more expensive components requiring high acceleration forces for regulation.

In accordance with the present invention, there is provided vibration damping apparatus in or for an arc furnace comprising at least one electrode and at least one electrode support system, said apparatus comprising at least one damping device provided for the electrode and/or electrode support system, for damping mechanical vibrations.

In embodiments of the invention to be described herein, the vibrations of the electrode support arm and of the electrode are reduced without having to make the dimensions of the whole support system too large. The vibrations are largely eliminated by means of relatively small damping devices.

The damping device may be arranged between the electrode support system and/or electrode and a fixed point, with the advantage that the damping effect with respect to the fixed point is achieved very effectively with very simple means. Instead, the damping device may be arranged between the support system and an additionally provided inertial mass, with the advantage that it saves space because the whole device is carried along with the movable support system. Again, the damping device may be arranged between the support systems of two or more electrodes and this does not require an additional mass and the spatial relationships are very favourable. Naturally, however, the regulation differences of the electrode support system must be bridged.In the arrangements with additional mass, this may be mounted by elements permitting mutual displacements in response to vibrations and this makes damping possible in several directions. An economic solution is where the elements permitting displacement also secure the damping effect. In another embodiment, the damping device may encircle the electrode or its support system, with the advantage that rotational movements, as well, may be damped effectively with a space-saving and solid type of construction.

In a further embodiment, the damping device may be connected to the support system by a rope, a constructionally simple possibility, with the damping device perhaps mounted on a fixed part outside the furnace.

Even though the most significant and most troublesome vibrations act in the horizontal direction at right angles to the axis of the support arm, the vibrations also contain components acting in other directions. At least two similar or different damping devices may be provided, therefore, arranged to dampen the vibrations in these different directions.

The damping device may comprise an hydraulic cylinder. An additional mass may be arranged with this cylinder so that, due to its inertia, it acts as a nearly fixed point and in this way causes the fluid of the hydraulic cylinder to accelerate. Instead, the additional mass may remain outside of but connected to the hydraulic cylinder which, therefore, can have smaller dimensions. In other embodiments, the damping device may comprise a brake, which in a simple manner converts the kinetic energy of the vibrations to heat.

In the arrangements with additional mass mounted by elements permitting mutual displacements, these elements may be springs with the advantage of mechanical reliability.

Instead, they may comprise diaphragms, which are spatially very advantageous and make it possible to create a closed damping system.

These elements may comprise a hollow body housing a movable body, thus structurally very simple and making it possible to dampen the vibrations in several directions. The hollow body may be symmetrical with respect to rotation. If, e.g., the spherical shape is selected damping is achieved in several directions. The movable body may consist of bulk material a solution which is even simpler and more economic. The movable body may instead be a liquid, e.g. a mineral or silicone oil, with the advantage that there is no wear to be taken into consideration.

In another embodiment, the vibrations of the electrode and/or the electrode support system are sensed and damped actively.

Embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings, in which: FIGURE 1 is a section through a first embodiment of damping device, comprising an additional mass arranged in a housing; FIGURE 2 is a similar section through a second embodiment in which an additional mass, has a connecting boring; FIGURE 3 is a similar section through a third embodiment in which the additional mass is mounted by means of diaphragms; FIGURE 4 is a schematic diagram of an apparatus in which four hydraulic cylinders are mounted between three support arms; FIGURE 5a and b are respectively a side view, partly in section, and a cross-section through a fifth embodiment in which two hydraulic cylinders are arranged in the interior of the additional mass;; FIGURE 6a and 6b are similar views of a sixth embodiment in which a mechanical brake is used for the damping device; FIGURE 7a and 7b are similar views of a seventh embodiment comprising a mechanical brake which encircles the electrode support arm; FIGURE 8 is a schematic diagram of an eighth embodiment comprising a mechanical brake which is connected to the electrode support arm by means of a rope; FIGURE 9 is a partial section through a ninth embodiment in which the vibrations of an electrode are damped by means of two rollers; FIGURE 10 is a section through a tenth embodiment in which inside a hollow sphere another one is supported to be rotatable with a centre of gravity arranged eccentrically;; FIGURE 11 is a similar section through an eleventh embodiment having a hollow sphere in which the interior is partially filled by bulk material or by a viscous fluid; and FIGURE 1 2 is a schematic diagram of a twelfth embodiment comprising a vibrator which actively dampens the vibrations.

According to Figure 1, on an electrode support arm 1 with a support 2 a housing 3 is mounted inside of which an additional mass 4 is centred by means of centering springs 5. Housing 3 contains a damping fluid 6, e.g., oil or glycerine. The left hand space and the right hand space in housing 3 on the side of the additional mass 4 are jointed by a connecting tube 7 in which an adjustable orifice 8 is arranged. For an 80-t furnace the additional mass is suitable 1 t.

The embodiment according to Figure 1 operates in the following manner: The vibrations of the support arm are transmitted to housing 3 via support 2. Due to its inertia the additional mass 4 remains relatively motionless in space so that housing 3 performs movements from right to left and conversely with respect to the additional mass 4. Thus the damping fluid 6 has to flow alternately in both directions through connecting tube 7 and through the adjustable orifice 8. In this way the kinetic energy of the vibrations is damped and converted to heat The embodiment according to Figure 2 essentially corresponds to that according to Figure 1 the same reference numbers are being used for Figure 2 and also for all further drawings for the same parts.According to Figure 2, the additional mass 4 contains a conecting boring 9 equipped with an orifice 8. This boring 9 replaces connecting tubb 7 according to Figure 1. The operation of the embodiment according to Figure 2 corresponds to that according to Figure 1.

In Figure 3 another illustrative embodiment of the subject of the invention is shown. In L,uusing 3 two diaphragms 10 are mounted which hold the additional mass 4 by means of connecting rods 11. The damping fluid 6 is present only outside of diaphragms 10 and in connecting tube 7 equipped with the adjustable orifice 8. The operation of the example according to Figure 3 corresponds to that according to Figure 1.

The embodiment according to Figure 4 shows three electrode support arms 1 equipped with levers 12. The device contains four hydraulic cylinders 14 which are connected with their mounting rods 13 and their piston rods 1 6 to pivot with levers 12. Pistons 1 5 are arranged to move inside hydraulic cylinders 14 and the interior of hydraulic cylinders 14 is filled with damping fluid 6. In this example, too, a connecting tube 7 with adjustable orifice 8 is being used. The normally non-synchronous vibrations of the different electrode support arms 1 are damped by small movements of pistons 1 5. Due to pistons 1 5 and the hinged mountings of the hydraulic cylinders with supports 12 also mutual, greater regulating movements of the electrode support arms 1 are possible.

According to Figure 5a and Sb the additional mass 4 is constructed with a hollow space 18. The additional mass 4 is supported on the electrode support arm 1 by means of a spring 17 for weight compensation. Inside hollow space 18 two hydraulic cylinders 14 are mounted to pivot. The operation of these hydraulic cylinders corresponds to that of the hydraulic cylinders 14 according to Figure 4. Hydraulic cylinders 14 are attached by means of mountings 20. Additional mass 4 is connected laterally with supports 2 via elastic rings 21 of rubber. These elastic rings 21 will dampen the vibrations also in the direction of axle 19.

The embodiment according to Figure 6a and 6b shows a solution in which the vibrations are damped with a mechanical brake. Friction plates 22 are constructed as additional mass on both sides and are joined by means of screws 23 equipped with cup springs 24. Friction bodies 25 are provided with borings 26 providing free passage for screws 23 so that friction bodies 25 can swing freely with respect to friction plates 22.

Friction plates 22 are supported by means of springs 17 and mountings 27.

Figure 7a and 7b show a similar embodiment as Figure 6a and 6b but the electrode support arm passes through borings in friction plates 22 and friction bodies 25 so that they encircle the electrode support arm 1. The remaining parts correspond to those according to Figure 6a and 6b.

Figure 8 shows an embodiment in which an electrode 28 is connected to support column 29 by means of electrode support arm 1. Electrode support arm 1 is connected to support column 29 by means of insulating mounting 30. Support column 29 is supported in guide rollers 31 mounted on support 32. As well, on this support 32 a bearing bracket 33 is arranged which carries a first deflection pulley 34. A second deflection pulley 35 is attached to wall 36. A rope 37 fixed in mounting 38 is passed over pulleys 34 and 35; a friction body 39 supported between two friction plates 40 is attached to the rope. These friction plates 40 are pressed together by means of a spring 41. The friction body 39 is joined to a weight 42. The operation of the device is clear from the drawing and corresponds to that according to Figure 6a and 6b.

Figure 9 shows an electrode 28 supported by means of two pressure-loaded rollers 43. These rollers are held in forks 45 via axles 44. Forks 45 are connected to hydraulic cylinders 1 4 known from previous examples. In this example these hydraulic cylinders 14 are provided additionally with compression springs 46 and are supported on the furnace cover acting as fixed point.

Naturally, this arrangement must be made resistant against heat radiation, or protected against it. instead of rollers 43 clamps can also be provided which encircle the electrode at least partially.

Figure 10 shows another illustrative embodiment. Electrode support arm 1 is connected, with the aid of support 2, to a hollow sphere 47 inside of which another, smaller hollow sphere 48 is arranged to move. The space between the two hollow spheres 47 and 48 is filled with a viscous fluid 49. Inside the inner, movable hollow sphere 48 an additional mass 50 'is mounted eccentrically. Above the additional mass 50 there is a hollow space 51. During the vibrations the inner hollow sphere 48 will move inside hollow sphere 47 and will act as a damping device due to the eccentric additional mass 50 and by virtue of being supported in viscous fluid 49.

The embodiment according to Figure 11 works in a similar fashion but has a simpler structure.

Hollow sphere 47 contains a viscous fluid 52 which only partially fills the interior of hollow sphere 47. Above liquid 52 there is a hollow space 51. The viscous fluid 52 can be replaced by bulk material such as sand or metal particles.

Figure 12 shows a further development of the subject of the invention. The vibrations of electrode 28 are measured with the aid of a laser beam 53 with measuring instrument 54. This method is known in itself and described, e.g. in the article "Schwingungsverhalten von Elektroden und Tragarmen in Lichtbogenöfen" (vibration behaviour of electrodes and support arms in arc furnaces), mentioned initially, and illustrated. The values measured are evaluated in a regulating and control unit 55. This regulating and control unit 55 then controls a vibrator 56 which is in mechanical contact with electrode 28 by means of a roller 57 (or a clamp) held in a fork 58. The vibrations of vibrator 56 act in opposition to the vibrations of electrode 28 and thus produce effective active damping. Naturally, the active damping according to Figure 12 can also be performed in two or more directions.

The subject of the invention is, of course, not restricted to the representations in the drawing.

Thus, instead of rubber rings 21 metallic felt-like damping bodies or other resilient and energy absorbing elements can be used. Instead of mechanical brakes with dry lining other types of brakes known in themselves can also be used, such as brakes with viscous layers or viscous fluids. The shape of hollow bodies 47 could be other than spherical. In the embodiment according to Figure 12 the vibrations of electrode 28 or of the electrode support system 1 could also be measured by a different method from the one shown.

Claims

1. Vibration damping apparatus in or for an arc furnace comprising at least one electrode and at least one electrode support system, said apparatus comprising at least one damping device provided for the electrode and/or electrode support system, for damping mechanical vibrations.

2. Apparatus according to claim 1, in which the damping device is arranged between the electrode support system and/or the electrode and a fixed point.

3. Apparatus according to claim 1, in which the damping device is arranged between the electrode support system and an additionally provided mass.

4. Apparatus according to claim 1, comprising at least two electrode support systems, in which the damping device is arranged or mounted between the electrode support systems.

5. Apparatus according to claim 3 in which the additional mass is mounted on the electrode support system by means of elements permitting mutual displacements in response to vibrations.

6. Apparatus according to claim 1, in which the damping device contains at least one part consisting of an energy absorbing material.

7. Apparatus according to claim 1, in which the damping device encircles the electrode support system and/or the electrode.

8. Apparatus according to claim 1, in which the damping device is connected to the electrode support system by means of a rope.

9. Apparatus according to claim 1, in which at an arc and/or at an electrode support system and/or at an electrode at least two similar or different damping devices are provided which are preferably arranged in different planes.

10. Apparatus according to claim 1, in which the damping device contains at least one hydraulic cylinder.

11. Apparatus according to claim 10, in which inside the hydraulic cylinder at least one additional mass is arranged.

1 2. Apparatus according to claim 10, in which the hydraulic cylinder and/or its piston rod are connected to an additional mass.

13. Apparatus according to claim 1, in which the damping device comprises at least one brake.

14. Apparatus according to claim 5, in which the elements permitting mutual displacements comprise springs.

1 5. Apparatus according to claim 5, in which the elements permitting the mutual displacements comprise diaphragms.

1 6. Apparatus according to claim 5, in which the elements permitting the mutual displacements comprise at least one hollow body inside of which at least one movable body is located.

17. Apparatus according to claim 16, in which the hollow body and/or the movable body are symmetrical with respect to rotation.

18. Apparatus according to claim 16, in which the movable body consists of bulk material.

19. Apparatus according to claim 16, in which the movable body consists of a liquid.

20. Apparatus according to claim 1, in which the damping device comprises at least one measuring instrument for measuring the vibrations of the electrode and/or the electrode support system and at least one vibrator which is in mechanical contact with the electrode and/or the electrode support system, a regulating and control unit being provided for the evaluation of the values measured with the measuring instrument and for controlling the vibrations of the vibrator with corresponding amplitudes opposing the measured amplitudes.

21. Vibration damping apparatus in or for an arc furnace, substantially as herein described with reference to any one of Figures 1 to 12 of the accompanying drawings.