DESC:FIELD OF THE INVENTION

The invention relates in general to basic oxygen furnace vessels and in particular to a basic oxygen furnace vessel suspension system. It discloses a converter vessel with a trunnion ring which surrounds the converter vessel which has two diametrically opposite trunnion pins respectively arranged as a drive pin and a non-drive pin and suspension systems for supporting the converter vessel on the trunnion ring. The suspension systems comprise at least four horizontal suspension bar which are symmetrically placed over the trunnion top and arranged at angles pointing the horizontal axis for self-aligning of the converter towards the charging and tapping side during rotation and at least eight vertical suspensions aligned to the bottom cone at an angular orientation that requires much lesser space around the converter.

This Complete Specification is filed in pursuance to the Provisional Specification filed on 07th October 2017 in respect of Patent Application No.201731035628.

BACKGROUND AND PRIOR ART

With abundant iron ore being available and shortage of quality scrap existing in India, an integrated steel plant is the ideal solution of capacity expansion of Indian steel industry. The most preferred route of steel making in an integrated steel plant is the Basic Oxygen Furnace (BOF) route. Worldwide share of steel through BOF route is around 74% of total production.

However, in India, share of BOF route in steel making is around 43%. Indian steel industry is aiming to produce 300 MT steel plant by the year 2030 from present 110 MT installed capacity. It is expected that majority of this steel is to be produced through BOF route for the upcoming plants.

In the BOF process, oxygen is blown into the BOF vessel (Converter) at supersonic speed with the help of retractable lance for refining of hot metal (Liquid Iron). BOF process was discovered in 1948 by Linz Donawitz of Austria. With the passage of time the BOF process has evolved into a highly efficient route owing to its sophisticated automation and process control.

The exothermic oxidation reactions which are generated in the converter produce a lot of thermal energy, more than the energy needed for reaching the determined temperature of the steel. This extra heat is used to melt the scrap metal and /or the added ferrous material. As the B.O.F. substantially is a furnace, it is also subject to thermal dilatations.

The converter consists of a container, defining the reactor and having a substantially cylindrical shape, supported by a trunnion ring, surrounding the container and appropriately distanced there from, provided with diametrically opposite supporting pins connected to trunnion, all supported by two bearings whose supports are anchored to the civil foundations above the ground. The rotating control of the container is fitted onto drive side pin of the trunnion ring. The function of the trunnion ring is to support the vessel at all phases of operation, while allowing it to undergo the thermal expansion necessitated by the process taking place within.

In the prior art, a series of suspension systems for supporting a converter vessel are known. Essential aims of these suspension systems are a low space requirement for the suspension systems with simultaneous use of the largest possible converter vessels, optimum support for the converter on the suspension systems, the accommodation of converter distortions by the suspension systems, as well as low maintenance and long working life for the suspension systems.

Existing technologies available in this area

In the BOF converter, the vessel is supported with the trunnion ring. The trunnion ring is connected with trunnion pins (drive and non-drive) which in turn are supported over spherical roller bearings at two diametrically opposite sides (fixed and expansion type). The drive side trunnion pin is connected with the tilt drive system of the converter which rotates the converter. This design concept is followed in most of the converters worldwide. However, the suspension system between trunnion ring and vessel is based on individual supplier’s patented design.

The converter vessel suspension systems in the prior art are mainly of following types:

BRACKET SYSTEM :

The bracket system as incorporated in earlier BOF design mainly consists of structural brackets welded/bolted to the vessel body and supported on the trunnion. Several kinds of designs are observed in this category offering very limited flexibility for vessel expansion and vibration. Due to its rigid assembly, there is little play room for vessel movement with respect to the trunnion ring. These kinds of suspensions generate higher stress on the converter shell and support bearings. Usually shell thickness of such converters is kept very high owing to the above.

DISK SUSPENSION SYSTEM:

This system relies on two main circular discs protruding from the trunnion ring center of rotation engaging into two large circular rings attached to the shell by welds and radially braced by heavy gussets. These guarantee the support of the vertical gravitational loads of the vessel and its auxiliary equipment while enabling the vessel to radially and longitudinally expand without restriction. To enable tilting the vessel without relative motion between the shell and the trunnion ring, a third bracket called a tilting claw or toggle is attached to the vessel at a point at the cross-axis of the vessel, supported on the trunnion ring, while a fourth member, called a guide claw, prevents lateral shifting of the vessel in the trunnion ring. This member does not take any gravitational or tilting load. The disc and ring are the supporting members and are in permanent engagement in all vessel tilting positions, thus avoiding shocks during tilting.

However, this suspension method requires a larger space between the vessel and the trunnion ring than usually required when utilizing other suspension systems. So, it would be difficult or even impossible to use this system in the case of a replacement BOF vessel, where the available space is already dictated.

The disc suspension system is more vulnerable in the case of a breakout due to a burn-through, by virtue of the large shell area required by the ring and its bracing gusset. Repairing a damaged shell and/or suspension system component in this area becomes more difficult, as the majority of this area is inaccessible behind the trunnion ring.

LAMELLA SYSTEM:

In lamella system, the suspension is done using lamellar plates. Each set of lamellar suspension has one pair of lamella plates (separated with spacer) connected between the lower shell and trunnion using several high strength bolts. Generally, eight pairs of lamellar plates are used in a converter. The system provides the required flexibility of movement between vessel and the trunnion due to deflection of plates at their weaker axis. However, each lamella plate is approx. 800mm wide. As a result, eight sets of Lamella system occupy major area in the lower shell region and more prone to metal damage in case of melt through. The lamella plates are made of special grade steel and are generally procured only through OEMs and mostly imported.

LINK SYSTEM:

The link suspension system consists of horizontal and vertical link connections between the vessel and trunnion. The link is equipped with planer bearings, which allow for swiveling motion of the vessel. The links are connected by pins to fixation brackets welded to the vessel shell and the trunnion ring. The link system requires elaborate fixing arrangement, larger space and diameter of trunnion and also heavier brackets owing to its bearing size. The system requires special guides for preventing the vessel from lateral shift during tilting.

TENDON SYSTEM:

The tendon system uses high strength pre-stressed tendons for supporting the vessel. Four sets of tendons are suspended from trunnion top and connected with the lower portion of the shell with bracket connection. For horizontal loads transverse tendons are used above and below the trunnion. The tendon system is not being used in the present-day converters. The lower brackets require large areas and extend into the barrel portion. These are difficult to repair in case of metal through.

TIE ROD SYSTEM

The tie rods are arranged at four locations around the vessel shell. Each location incorporates four sets of vertical tie-rods which are flexible for radial deformation and stiff in the longitudinal and circumferential directions. Additionally, two horizontal supports are arranged underneath the trunnion ring in order to take most load of the converter in the 90° tilted position. Here vessel movement is taken care of by bending of the elastic bar due to its slenderness and use of spring material. Moreover, here in vertical suspension, top end of each elastic bar is mounted over the top plate of trunnion ring (fixed type connection). Each elastic bar has to be punctured through the trunnion ring. The trunnion will have several holes and sleeves for this purpose.

It is to be noted that inside the trunnion ring there are also utility pipe lines (Argon/Nitrogen) for bottom stirring whose access will become difficult during installation, repair and maintenance work inside trunnion ring.

At the bottom side of the suspension, the mounting has a very large and heavy bracket with long outer projection. The elastic bar is held by split plates joined with two smaller bolts. Clearance for lateral shift has been kept to take care of misalignment of the elastic bar using sliding plates. There are also two numbers of spherical spacers for taking care of the misalignment of the nut due to bending. Here, the horizontal suspensions mounted over the trunnion as well as under the trunnion.

The present invention has the purpose of overcoming the disadvantages and difficulties described above.

OBJECTS OF THE INVENTION

Accordingly, the primary object of the present invention is to provide a basic oxygen furnace vessel suspension system built on modular concept.

Another object of the present invention to provide a basic oxygen furnace vessel suspension system that requires lesser space compared to the latest lamella, link or bracket systems.

Yet another object of the present invention is to provide sturdy design of entire basic oxygen furnace vessel suspension system with ease of assembly/replacement/repair.

A further object of the present invention is to provide a non-rigid basic oxygen furnace vessel suspension system for allowing flexibility of vessel movement and thermal expansion.

Yet another object of the present invention is to provide a self-aligning basic oxygen furnace vessel suspension system, both in vertical and tilted condition.

A further object of the present invention is to provide a basic oxygen furnace vessel suspension system which has lower manufacturing cost than other available suspension systems.

How the foregoing objects are achieved will be clear from the following description. In this context it is clarified that the description provided is non-limiting and is only by way of explanation.

SUMMARY OF THE INVENTION

A basic oxygen furnace vessel suspension system for a converter which can be tilted is disclosed. The converter has a converter vessel having a vertical axis and a trunnion ring surrounding the converter vessel at a distance with a drive end pin and a non-drive end pin. The vessel suspension system comprises of four sets of vertical suspensions arranged at 100° and 80° apart to ensure a fairly uniform vessel load distribution all around the vessel. Four sets of horizontal suspension system comprising of a single suspension bar in each set are placed at angular positions of 37° to the converter horizontal center axis. Each vertical suspension set is connected to the bottom cone at an angular orientation of 22.5° with respect to the vertical axis. Two horizontal suspension bars on each side are mirrored at an angle of 37° towards the horizontal center line passing through the tap hole and converter center.

Each set of the vertical suspension consists of two suspension bars arranged in parallel configuration. The top end of each suspension bar is connected with upper brackets welded to the trunnion with two sets of thrust spherical plain bearings type I and type II to take care of the thermal expansion. The bottom part of the suspension bars is connected in similar pattern with the lower brackets welded to the bottom cone where the skin temperature is in the range of 150° C-200° C.

The angular position of the suspension rods ensures that the vessel is aligned automatically towards vertical central axis and also prevents vessel deformation (creep) in the vertical direction.

Each horizontal bar is coupled with thrust spherical plain bearing sets type I and type II at both ends. One end of the suspension bar is connected with the welded brackets in the barrel section and the other end is connected with the brackets welded to the trunnion ring top plate.

The tap hole position and converter mouth are automatically aligned towards converter center line due to inward forces acting on angular suspensions during tilting operations of the vessel.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The nature and scope of the present invention will be better understood from the accompanying drawings, which are by way of illustration of a preferred embodiment and not by way of any sort of limitation. In the accompanying drawings: -

Figure 1 shows the elevation of the Basic Oxygen Furnace Vessel with the suspension system according to the present invention.

Figure 1A shows the top view of the Basic Oxygen Furnace Vessel with the suspension system according to the present invention.

Figure 1B shows the enlarged view of the vertical suspension system, assembled with the BOF converter as per detail “A” of figure 1.

Figure 1C shows the enlarged view of the horizontal suspension system, assembled with the BOF converter as per detail “B” of figure 1.

Figure 2A shows the detailed elevation of the vertical suspension system.

Figure 2B shows the detailed side view of the vertical suspension system.

Figure 3A shows the detailed elevation of the horizontal suspension system.

Figure 3B shows the detailed side view of the horizontal suspension system.

Figure 4 shows the elevation of the suspension bar.

Figure 5A shows the top view of thrust spherical plain bearing type-I.

Figure 5B shows the elevation of thrust spherical plain bearing type-I.

Figure 6A shows the top view of thrust spherical plain bearing type-II.

Figure 6B shows the elevation of thrust spherical plain bearing type-II.

Figure 7A shows the side view of the Basic Oxygen Furnace Vessel with suspension system during hot metal charging condition at an angle of 45-60° with the vertical axis.

Figure 7B shows the side view of the Basic Oxygen Furnace Vessel with suspension system during steel tapping condition at an angle of 65-115° with the vertical axis.

Figure 7C shows the side view of the Basic Oxygen Furnace Vessel with suspension system during oxygen blowing condition at an angle of 0° with the vertical axis.

Figure 7D shows the side view of the Basic Oxygen Furnace Vessel with suspension system during full emptying condition at an angle of 180° with the vertical axis.

Figure 8A shows the arrangement of horizontal suspension system on top of the trunnion ring.

Figure 8B shows the arrangement of vertical suspension system on bottom side of the trunnion ring.

DETAILED DESCRIPTION OF THE INVENTION

Having described the main features of the invention above, a non-limiting description of a preferred embodiment will be given in the following paragraphs with reference to the accompanying drawings.

In all the figures, like reference numerals represent like features. Further, the shape, size and number of the devices shown are by way of example only and it is within the scope of the present invention to change their shape, size and number without departing from the basic principle of the invention.

Further, when in the following it is referred to “top”, “bottom”, “upward”, “downward”, “above” or “below”, “right hand side”, “left hand side” and similar terms, this is strictly referring to an orientation with reference to the apparatus, where the base of the apparatus is horizontal and is at the bottom portion of the figures. The number of components shown is exemplary and not restrictive and it is within the scope of the invention to vary the shape and size of the apparatus as well as the number of its components, without departing from the principle of the present invention.

All through the specification, the technical terms and abbreviations are to be interpreted in the broadest sense of the respective terms and include all similar items in the field known by other terms, as may be clear to persons skilled in the art. Restriction or limitation if any referred to in the specification, is solely by way of example and understanding the present invention.

BOF converters have to handle high dynamic load during charging and operation stages. The entire suspension system has to be very sturdy and fail proof. The present invention looks into this aspect with each set of suspension set being designed to take any unnatural distribution of load. There are very few parts in the suspension which ensures sturdiness. Unlike in other suspension systems, the use of smaller fasteners has been avoided. Standard and proven material has been considered for each element. Suspension bars and bearing assembly are easier to handle than other suspensions due to their compact size and simpler members and can be quickly replaced in case of any metal through or other damages.

Both the horizontal and vertical suspensions are exactly the same with all common parts. The dimensions of the suspension bars, bearings and fasteners are same in all units. Commonality of parts is very helpful for manufacturing as well as maintenance, when required. The design, due to its less space requirement, allows more free area in the vessel, especially in the bottom part. The manufacturing cost is substantially lower than other available suspension systems due to its simpler design and use of standard material.

The major design/operating parameters of the basic oxygen furnace suspension system according to the present invention are outlined below; The BOF suspension system is provided with these features which affect the vessel campaign life and its flexibility. It is designed to meet the intended target:

A) Main technical parameters of the BOF converter vessel:
Nominal Heat size (Capacity of the vessel) : 100 t hot metal
Maximum heat size : 110 t
Total weight of the vessel considered : 588 t
Vessel height : 8520 mm (from Lip-ring top)
Vessel diameter : 6600 mm (Shell outside)
Trunnion inner diameter : 6960 mm
Trunnion outer diameter : 8360 mm
Top cone angle : 300
Bottom cone angle : 22.50

B) Technical details of the suspension system proper:

a) Suspension bars
Horizontal suspension bar
Set of suspension bar : 4 sets.
No. of bars in each set : 1 nos.
Length of each bar : 2740 mm
Diameter : 150mm
: 160mm (Threaded portion)
Angle with vessel centerline : 370
Material of construction : High strength, fine grain forged
quality steel bar
Vertical suspension bar

Set of suspension bar : 4 sets.
No. of bars in each set : 2 nos.
Length of each bar : 2740 mm
Diameter : 150mm
160mm(Threaded portion)

Angle with vessel centerline : 22.50
Material of construction : High strength, fine grain
forged quality steel bar
b) Thrust spherical plain bearing
Bearing (Type-1)
Outer diameter : 400 mm
Rotational radius : 980 mm
Max angular rotation : 50

Bearing (Type-2)
Outer diameter : 400 mm
Rotational radius : 800 mm
Max angular rotation : 50

c) Fasteners :
Lock nut (Bearing) : M160
Hexagonal nut : M160
Sleeve : 180 mm outer diameter
Sleeve nut : M180
Washer : 160 /215 /200 mm (inner diameter)

d) Supporting Brackets :
Plate thickness : 60 / 70 mm
Material of construction : Boiler quality steel plate
Welding electrodes : E7018 (low hydrogen)

During steel making, oxygen is blown at approx. Mach 2 velocity inside the bath in the converter. The bath undergoes a vigorous reaction producing axial vibrations in the vessel to the tune of 0.3-0.4 Hz. The bath temperature goes up to 17500C. The inner surface of the BOF vessel is protected with refractory lining which insulates the bath from the shell. In modern BOFs maximum shell temperature may go up to 3000C. Due to thermal stress, expansion of the vessel shell takes place both in vertical and radial directions. The flexible suspension system of the present invention accommodates the various movements of the vessel due to vibration and thermal expansion, which also result in increase in fatigue life of the vessel. This also protects the trunnion bearings from damage in long run. Refractory lining inside the vessel also undergoes thermal expansion, which induces additional mechanical stress in the shell. The vertical suspension bar restricts the vertical movement of the shell and prevents critical downward vertical creep in the long run. The horizontal suspension helps in reducing bulging of the vessel into oval shape by restricting the permanent deformation along the horizontal center axis.

The vertical suspensions are radially arranged at an angle of 22.50 with respect to the vertical central axis of the converter. The reactionary force of the suspension bars act at this angle towards the vertical center axis of the converter. As a result, the converter will always remain aligned to the center line in vertically upright condition. The two horizontal suspension bars on each side are mirrored at an angle 370 towards the horizontal center line passing through the tap hole and converter center. Due to this, the furnace is always aligned to the horizontal center axis in tilting positions. During tilting operation, the converter is automatically centered and does not require any additional centering guide.

We now refer to the accompanying drawings.

Figure 1 shows an elevation view of a converter (1) which can be tilted. The tiltable converter (1) comprises of a converter vessel (2) having a converter vertical axis (3), a trunnion ring (4) surrounding the converter vessel (2) at a distance with a drive end pin (6) and a non-drive end pin (7).

For the exemplary embodiment described here, a converter vessel of 100 t heat size has been considered. However, with the modular approach it can be easily adapted to different sizes of converter vessels by increasing the number of suspension systems and adjusting the length of the suspension bars.

Figure 1A shows a top view of a converter (1) which can be tilted. Horizontal suspensions (4 nos.) are symmetrically placed over the trunnion top and arranged at angles pointing the horizontal axis which will result in self aligning towards the charging and tapping side during rotation.
Vertical suspensions are angular and aligned to the bottom cone. Angular alignment requires shorter brackets to be mounted on the bottom cone and the suspensions requires much lesser space around the converter

The suspension arrangement according to this invention mainly comprises of following:

Vertical suspension system:

We refer to Figures 1B, 2A, 2B, 8A and 8B.

The vertical suspension system is the main suspension for the converter in vertical position (Upright position at 00 and full emptying position at 1800). Each set of vertical suspension consists of two numbers of suspension bars (8) arranged in parallel configuration. Each set is connected to the bottom cone at an angular orientation w.r.t vertical axis (22.50). In the vertical upright position of the converter, the top end of each suspension bar is connected with the upper brackets (9) welded to the trunnion (4) with two sets of thrust spherical plain bearings type I and type II (11, 12). The bottom part of the suspension bars is connected in similar pattern with the lower brackets (10) welded to the bottom cone where the skin temperature is on lower side (2000C-1500C ).

The thermal expansion of the vessel during the process is taken care of by the movement in the two types of thrust bearing sets (Type-1 and 2) (11,12). Based on geometric arrangement, the bearing Type-1 and Type-2 will have different rotation radii.

Four sets of such vertical suspension systems are arranged at 100 and 80 degrees apart. The distribution of the suspensions ensures a fairly uniform vessel load distribution all around the vessel. The angular position of the suspension rods (8) ensures that the vessel is aligned automatically towards vertical central axis. This arrangement also prevents vessel deformation (creep) in the vertical direction as the vessel is restricted in its downward movement. The selected curvature of the thrust spherical plain bearing ensures that the vessel is well supported even if there is extreme radial deformation of up to 150 mm in the long run.

The suspension bar design considers the safety factor comparable to any other prior art system. Converter in empty and frozen bath condition (with solidified metal) can be rotated upto 3600. In the vertically downward condition the suspension assists centering the converter along with its horizontal suspension system.

The suspension bar is a short rigid bar where slenderness is not a factor and bending of the bar is not envisaged. The vessel movement is taken care of by the flexible connection at both ends which allows rotation of the bar. The suspension bar has two sections i.e. threaded (18) and unthreaded (19), best shown in figure 4.

b) Horizontal bar system:

Now we refer to Figures 1C, 3A, 3B, 8A and 8B.

The horizontal suspension system (13) comprises of a single suspension bar in each set. Similar to the vertical suspension, each converter vessel has four sets of horizontal bars (13) at angular positions of 370 to the converter horizontal center axis. During hot metal charging, converter is tilted between 450-600 towards charging side, best shown in figure 7A, and during tapping, best shown in figure 7B, the converter is tilted between 650-1150 towards tapping side. During these tilting operations, the tap hole (16) position and converter mouth is automatically aligned towards converter centerline due to inward forces acting on angular suspensions. Unlike other suspensions of the prior art, no separate guide is required for alignment and for preventing lateral shift. Flexibility of the horizontal suspension also ensures shock absorption during various operations such as de-bricking, scrap charging and hot metal charging.

The bracket design of the horizontal bar system has been done by clubbing other functionality such as support for the main vessel during assembly and maintenance. It is to be noted that both vertical as well as horizontal suspensions have commonality of parts such as suspension bars, bearings (type-1 and 2) and fastener system. Sturdy and high strength standard fasteners are used for adequate load bearing.

Operating mechanism of the BOF converter

Now we refer to figures 7A, 7B, 7C and 7D.

In BOF steelmaking, the converter is charged with hot metal (molten iron) from blast furnace along with 7% to 20 % scrap. Oxygen is blown into the bath at high velocity with the help of retractable oxygen lance system. During this process, the oxidation of silicon, manganese and carbon takes place which are all exothermic, resulting in an increase in bath temperature.

After refining, the furnace is rotated and liquid steel is tapped into a ladle through the tap hole.

After tapping the liquid steel, the furnace is rotated in the opposite direction and de-slagging is carried out into a slag-pot.

Towards the end, slag splashing is carried out to spread the remaining slag over the lining in order to increase the lining life.

The basic oxygen furnace operates as a batch melting process producing batches of molten steel known as ‘Heats’. The furnace operating cycle is called the tap-to-tap cycle and is made up of the following main operational steps:

• Hot metal charging: Vessel tilting by 45-60° (charging side)
• Oxygen Blowing : Vessel in upright position (0°)
• Tapping : Vessel tilted from 65 to115°(tapping side)
• De-Slagging : Vessel tilted from 103 to 180°(charging side)
• Slag splashing : Vessel in upright position (0° )

Modern operation of BOF has a tap-to-tap time of less than 50 minutes. During the process, the converter is rotated to various angles (0-360°) under varying load conditions. The converter suspension system plays a very critical role for the same.

The present invention has been described with reference to some drawings and a preferred embodiment purely for sake of understanding and not by way of any limitation and the present invention includes all legitimate developments within the scope of what has been described herein before and claimed in the appended claims.
,CLAIMS:We claim:

1. A basic oxygen furnace vessel suspension system for a converter (1) which can be tilted, the converter comprising of a converter vessel (2) having a vertical axis (3), a trunnion ring (4) surrounding the converter vessel (2) at a distance with a drive end pin (6) and a non-drive end pin (7), the vessel suspension system comprising of four sets of vertical suspensions arranged at 100° and 80° apart to ensure a fairly uniform vessel load distribution all around the vessel and four sets of horizontal suspension system comprising of a single suspension bar (13) in each set and placed at angular positions of 37° to the converter horizontal center axis (3), each vertical suspension set being connected to the bottom cone at an angular orientation of 22.5° with respect to the vertical axis (3), two horizontal suspension bars on each side being mirrored at an angle of 37° towards the horizontal center line passing through the tap hole and converter center.

2. The basic oxygen furnace vessel suspension system as claimed in claim 1, wherein each set of said vertical suspension consists of two numbers of suspension bars (8) arranged in parallel configuration, the top end of each suspension bar being connected with upper brackets (9) welded to the trunnion (4) with two sets of thrust spherical plain bearings type I and type II (11, 12) to take care of the thermal expansion and the bottom part of the suspension bars being connected in similar pattern with the lower brackets (10) welded to the bottom cone where the skin temperature is in the range of 150° C-200° C.

3. The basic oxygen furnace vessel suspension system as claimed in claims 1 and 2, wherein the angular position of the suspension rods (8) ensures that the vessel is aligned automatically towards vertical central axis and also prevents vessel deformation (creep) in the vertical direction.

4. The basic oxygen furnace vessel suspension system as claimed in claim 1, wherein each horizontal bar (13) is coupled with thrust spherical plain bearing sets type I and type II (11,12) at both ends, one end of the suspension bar being connected with welded brackets (14) in the barrel section (2) and the other end being connected with brackets (15) welded to the trunnion ring (4) top plate.

5. The basic oxygen furnace vessel suspension system as claimed in claim 1, wherein the tap hole (16) position and converter mouth are automatically aligned towards converter centerline due to inward forces acting on angular suspensions during tilting operations of the vessel.