GB2147389A - Sliding gate closures for high temperature liquids - Google Patents

Abstract

A sliding gate closure of a vessel for molten metal has a fixed plate (5), and a plate (8) slidable from a position (shown) in which bores in the plates (5, 8) are aligned, in either direction to reduce or shut off flow of liquid. Plate 8 is biased into face-to-face sealing engagement with the plate (5) by springs (35) which act between fixed pins (36) and fingers (33) which are engageable with projections (20, 32) integral with a support housing (13) for the movable plate (8). The springs (35) are located for free air circulation therearound and the housing (13) may be pivoted about fingers (33) on one side to obtain access to the mating surfaces of the plates (5, 8). <IMAGE>

Description

SPECIFICATION Outlet gate closures for high temperature liquids This invention refers to a series of improvements in closures used in outlet gates for liquids at high temperatures, in order to achieve a dimensionally balanced assembly from which the maximum economic-productive performance can be obtained, always bearing safety factors and human error in mind, as can be gathered from the foliowing description.

In accordance with the foregoing, the improvements are specially suitable for control gates for outlets of vessels such as ladles or melting kettles for metals, in steelworks and other similar installations.

It is a very well known fact that the most expensive refractory parts, subject to strain, are the closure plates and that these, in the majority of conventional systems, only close in one direction.

In such outlet gates the molten metal produces three types of erosion on the plates: a gradual enlargement of holes in the plates produced by the flow of the steel in a fully open position of the gate; progressive formation of a bevel edge of the holes and contact area between the plates, not only on the side where the closure is made, which is flangeshaped and which takes place when the jet is restricted, producing a semi-elliptical section shaping; and a channel which is the prolongation of the said bevel edge or flange, in the plate surface, the channel having a width proportional to the diameter of the hole and a depth proportional to the number of movements produced.

It is obvious that in conventional systems, in which closing takes place in a single direction, this type of erosion is centered permanently in one point of the periphery of the hole, which leads to rapid deterioration of the said plate.

Some of the improvements are directed specifically towards solving these problems, considerably limiting this erosion effect, and in this connection, provided that closing can take place in two diametrically opposed directions.

Due to the possibility of opening and closing in two directions, the problem existing in some current systems is solved, those which have the hole of the plate in the centre, and in which, to be able to use them in the other direction, the device has to be opened, dismantling the plates with the greatest care, turning both through 180 and putting them back again, with the disadvantages which this involves, among others regarding loss of time, subjecting the operator to tremendous heat, and the risk of cracking the plates by thermal attack on opening the device. With the system of the invention it is not necessary to open or dismantle the refractories to use the plates in any direction, nor even to inspect them.

In this connection, -and as is conventional, the device includes a nozzle-holder block in which the respective ladle nozzle is installed, provided with an axial bore for pouring the liquid, and to which nozzle a fixed plate is integrally joined, also of a refractory nature and likewise provided with an axial bore, which is the prolongation of that of the ladle nozzle.

The invention resides principally in provision of a mobile plate having a bore located under a fixed plate also provided with a bore, and is mounted on a sliding carrriage, acting in both directions by means of a hydraulic or pneumatic cylinder, whereby the gate can be closed by the mobile plate shifting in one direction, as in conventional systems, or in the opposite direction. It is obvious that this functional arrangement may at least double the working life of the assembly.

This arrangement together with other complementary features, mean that a closing system provided with these improvements has a much higher effective potentiality than that of conventional closing systems.

This double movement of the mobile closing plate in both directions, apart from the aforementioned improvement in the working life of the assembly, offers the possibility of inspecting the state of the work surface of the fixed plate in both directions, avoiding risks, which it is not possible to detect with conventional systems, without dismantling the whole device, also avoiding thereby cracking and strains in the refractory, through thermal shock.

Moreover, as is also known, sealing systems are coupled in one way or another to the pouring hole of the vessel; the main problems of these devices are the strains suffered by them, due to the thermal expansions and contractions to which they are subjected, determined by the presence or absence of the molten metal.

Though it is known to use refractory material plates conventionally of alumina, with a relatively small expansion coefficient, current technology recommends the use of magnesite, as against conventional alumina. Magnesite has a considerably higher expansion coefficient than that of alumina, which means that the closure has to be of the resilient type, in order to enable these expansions to be absorbed, without the closure suffering on this account.

In this connection, Spanish patent of invention number 403,522 is referred to, in which a special resilient type closing system enables expansions of the sealing plate to be absorbed, while maintaining a perfectly air-tight closure, although it is opened a considerable number of times throughout a single tapping, i.e. of a given load for the tank or vessel supplying the molten metal.

In the aforesaid patent, a series of springs are used, which give the closure its resilient nature, but with the particularity that these springs rest direct on the refractory, which implies problems in numerous aspects. Moreover, the refractory parts have to be specially shaped, to allow the springs to rest correctly and, furthermore, as these springs are in a position extremely near the refractory, i.e.

with respect to the outlet of the molten metal, these are permanently subjected to thermal action, so that they also suffer high temperatures to which the refractory plates are subjected, and the respective large thermal changes, which leads to their rapid deterioration.

The improvements which the present invention proposes also affect resilient closures, which allow the use of large expansion refractory plates, substantially avoiding the problems of current technology in this connection, and improving practical operativity and performance of the parts subject to wear, i.e. of the refractory parts, through a series of unique structural features which will also be disclosed below.

Basically, these improvements are centered on effectively thermally separating the pressure springs for the refractory parts, from the pouring hole of the liquid at high temperature, so that these springs, absorbing the expansions and contractions perfectly through thermal differences, are not themselves affected by them.

For this reason, these springs are installed on two spring-holder parts and, suitably preset, act in pairs on a series of closing fingers which, consequently, as explained above, are at a considerable distance from the heat centre. This layout of the springs not only involves their being removed some way from the heat centre, but also enables the surrounding air to be easily renewed, which means that the heat emission affects them to a virtually negligible extent. This leads to the working life of these springs being greatly lengthened, as opposed to what happens in current systems, in which, as the springs are housed in points very near the heat centres, and not easily accessible for cooling air, their working life is extremely short.

The spring-holders referred to above, apart from establishing joining links between the actual springs and the main housing on which the respective refractory closing plate rests, have as complementary aims that of blocking the said main housing in a working position, and that of achieving a hinge effect which enables the said housing to fold back, to open the device and have direct access inside it, in order to change worn parts or simply to inspect them.

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings. in which: Figure 1 shows a plan view of a closing device for outlet gates of liquids at high temperatures, executed in accordance with the improvements proposed in this invention.

Figure 2 shows a side elevation and crosssection view of the same assembly shown in the previous figure, on the level of the drive means for the lower or mobile plate of the closing system.

Figure 3 shows a similar illustration to that in figure 2 but with the cross-section made on a different plane, in order to show the tilting devices of the mobile closing part, and Figure 4 is a cross-section, similar to that in figure 3, of an alternative emodiment showing the layout of the elements which provide the closure with its resilient features.

As shown in Figures 1 to 3 the set of refractory parts which form part of the system includes a nozzle-holder block 1, which is placed inside the vessel and which has a dimension and cavity such that its working life is proportional to the life of the inner refractory lining covering the walls of that vessel. In its inside and outside part, the block 1 has a circular configuration, and fits into a complementary cavity in a metal ring 2; this ring is welded to the vessel and performs the duty of centering and supporting the block 1, since the block 1 rests exclusively on the ring 2 and, finally, of acting as a support for the remainder of the device. For the last two reasons, the said metal ring 2 has to be sufficiently strong to avoid strains.

In the central cavity of the block 1, a tapered inner ladle nozzle 3 is housed, which is inserted from outside and which includes an axial hole whose cross-section will be calculated according to the maximum flow rate required in each case. The tapered shape is provided to allow the self-centering of the nozzle 3. Sealing between the nozzle 3 and the block 1 is made with refractory cement.

At its bottom end the nozzle 3 has an annular boss 4, concentric with the said axial hole, which engages a complementary recess in a fixed plate 5. The boss 4 has a keystone shaped section, with both side walls slanting, which provides three simultaneous advantages: fixed plate 5 is easier to place in position, the plate 5 is self-centering on the nozzle 3, and there is labyrinth passage through which the liquid would have to flow, in the event of leakage through the joint between the nozzle 3 and plate 5, this joint also being sealed with a suitable refractory cement.

The fixed plate 5 is housed in a cavity made for this purpose in a fixed part 6 of the device, which in turn is screwed and centered to the ring 2. The plate 5 is ground on both sides, to form a good surface support against the face of the housing and also a perfect seat with a mobile plate 8, as will be described below.

In its top part the plate 5 has an annular recess 7, which is complementary to the boss 4. The plate 5 also has a central hole which is aligned with that of the nozzle 3. In the recess 7, also having a keystone-shaped section, the boss 4 of the inner ladle nozzle 3 is housed.

The surface of the nozzle 3 on which the boss 4, is fitted, is coplanar with the surface of the cavity in which the fixed plate 5 is housed, thus allowing a perfect fit. This plate 5 includes a simple armour-plating 9, consisting of sheet metal approximately 2 mm. thick, which extends around the whole of the periphery of the fixed plate 5, without covering its whole thickness. The armour-plating sheet 9 has a lower flange 10, which acts as a support or stop for the fixed plate 5 when the latter is mounted in the said armour-plating 9.

The fixed plate 5 is secured to the armourplating 9 by a suitable refractory cement.

The cavity of the device in which the fixed plate 5 is housed has a peripheral recess 11 which allows a lip or flange 10 of the armourplating 9 to be amply housed, and in turn enables the latter to be open to the air. With this arrangement, seating of the plate 5 on the flat surface of the part 6, is ensured and cannot be affected by strains in the sheet 9, so that the join between the nozzle 3 and the fixed plate 5 is maintained whatever the operating position of the device.

A mobile plate 8 is identical with the aforementioned fixed plate 5, and is provided with armour plating identical with the plate 9. The plate 8 is housed in a cavity also having features identical with those of the fixed plate 5, but this mobile plate 8 is mounted on a mobile carriage 1 2 which slides lengthwise, so that, according to its relative position with respect to the fixed plate 5, alignment of holes in the respective plates 5, 8 is variable, to obtain maximum opening for maximum flow rate or partial or complete reduction of the flowrate.

The housing 1 3 is pivotally mounted on hinges 1 9 by means of pins 20. A plurality of springs 1 8 are mounted in holders 1 7. A plurality of hooks 1 5 are integral with the housing 1 3 and are engageable with flanges 1 6 corresponding to the spring holders 1 7.

The pressure of the springs 1 8 is transmitted by reaction to the housing 1 3 which supports the carriage 1 2 and is communicated directly to the mobile plate 8, which presses on the fixed plate 11, keeping both plates at the correct pressure to ensure closing.

On removing the pressure of the springs 18, unhooking the fingers 16, by folding the spring-holder parts 17, the device can be opened by pivotting about the hinges 19, allowing access inside to change worn refractory parts. This design allows the device to be opened on one side or another, as suitable in each case, simply changing the pins 20 from one side to the other.

The refractory tapping pipe 21 is a simple sleeve, provided with an axial hole 22, which is a prolongation of that of the fixed and mobile plates and that of the actual ladle nozzle, quoted above, including a boss 23, circular shaped and concentric with the hole 22, which fits perfectly into the recess of the mobile plate 24. This join is sealed with special refractory cement. The pipe 21 also has an armour-plated sheet 25, with an approximate thickness of 2 mm., and which also has original features which solve problems existing until now in conventional systems, simplifying assembly and allowing maximum exposure to the air, avoiding breakage and cracking through thermal shock, keeping these pieces perfectly joined and absorbing the expansion which is produced in the refractory pipe due to the effect of the heat.

Another feature of this armour-plating is the existence of the flange 27, which it has in its top mobile part, and which acts as support for the pipe 21 on the mobile carriage 12.

The position of the said circular flange 27 is calculated so that, once placed in the device, it remains practically at the height of the metal surface on which the mobile plate 7 rests. Hence, the expansion of the plates 5, 8 absorbed by the springs 18, does not push the tapping pipe 21, but pushes the metal surface in which it is seated, thereby avoiding the strain of the said flange 27 through the possible thrust of the plates 5 and 8 on the said pipe 21.To keep the plate 8 and the pipe 21 independent, allowing maximum use of some parts, independent of others, without this affecting the perfect sealing and relative positioning between both, the level between the armour-plated flange 27 and the top boss of the pipe 21, will be previously calculated so that the seating is perfect in centering and sealing between the mobile plate 8 and the tapping pipe 21 and does not depend on the human factor. In other words, the aim of the flange 27 is for positioning and not for withstanding great stresses and strains.

The mobile carriage 1 2 is longitudinally movable by means of a hydraulic or pneumatic cylinder 31, although preferably it will be hydraulic, whose shank 28 is connected to a part 29 which is integrally joined to the mobile carriage 12. This cylinder 31 is mounted in a cylinder-holder part 30 which can be joined to the housing 1 3 on which the mobile carriage 1 2 slides or at the bottom of the vessel, according to the type of assembly, and a suitable in each case.

The cylinder 31 is so dimensioned that it can overcome friction forces produced between the fixed plate 5 and the mobile plate 8 and between the mobile carriage 1 2 and the support housing 13, when the system is in its work position with the springs 1 8 compressed. Both the packing and the oil in the piston 31 and the hydraulic unit which assists and drives it, must withstand high temperatures and be non-inflammable.

The run of the cylinder 31 is calculated so that it is identical to the run performed by the mobile plate 8 in its two end positions of the closed system. This run is the result of a thorough and detailed study, starting from the way in which the liquid works in its most aggressive state, such as effervescent steel, on the refractory plates, which are the parts of the assembly most affected, and with most responsibility.

As mentioned above, steel produces three types of erosion on the plates 5 and 8, consisting of a gradual enlargement of the holes, produced by the flow of steel in its fully open position, a bevel-edge which forms around the holes on the sides on which closure takes place, and a channel which is the prolongation of the said bevel edge in the plate surfaces which has a width proportional to the diameter of the hole and a depth proportional to the number of movements produced.

With the materials foreseen in the application for manufacturing the plates 5, 8, this depth is practically negligible; it has been found that it is reduced to a simple shape, whose depth is so small that it does not allow liquid to be housed in its surface.

However, these three types of erosion have been taken carefully into account in dimensioning the plate surfaces, so that there are always safety areas of the plates which are never in contact with the liquid and that, whatever the relative position between them, those areas will always be in close contact.

These details, together with the maximum run of the mobile plate 8, which has also been optimized, and its end closing positions, with relation to the fixed plate 5i are what have served to determine the dimensions of the plate surface which covers the triple aim of safety, maximum working life of the refractory, and economy.

Regarding the thickness of the plates 5 and 8, although the seating is perfect throughout the surface, as both the metal and refractory surfaces have been ground, the unforseen circumstances of incorrect seating in the weakest part of the plate, i.e. in its centre, has been taken into account, that is, where the hole is placed, and the concentric recess, so that with maximum closing pressures, it withstands the stress without the plate breaking, disregarding the armour-plating. These cases of incorrect seating can occur when the sealing cement between the fixed plate and the inner ladle nozzle 3 sets prematurely.

Another advantage of the improvements, as mentioned above, is centered on the fact that by closing the mobile plate 8 in two directions there is the possibility of inspecting the state of the work surface of the fixed plate 5 in both directions, without having to open the device.

Referring now to figure 4, and in accordance with the improvements affecting the resilient closure, in which it can be seen how integral side arms 32 of the support housing 1 3 carry coupling bars 20 engageable with fingers 33 which form part of spring-holders 34, in which springs 35 are installed. Preferably four spring holders 34 are provided on each side of the housing 1 3.

The vertical travel of each spring holder 34 is limited by a pin 36 which is secured to the ring 2 and which passes through slots 37 in the spring-holders 34. The springs 35 surround respective guides 38. The springs 35 keep the mobile plate 8 pressed against the fixed plate 5 and, in view of the expansion of these elements, caused by their increase in heat, the downward movement of the mobile plate 8 is absorbed by the compression of the springs 35, also quoted; the mobile plate 8 is perfectly adapted to the fixed plate 5 at all times, which in turn ensures that the closed position is maintained between both plates.

The springs 35 are located away from the heat centre and in a position easy to ventilate by jets of cooling air, and can thus be kept at near ambient temperature, hence lengthening their working life since they are not affected by the tapping process.

The spring-holder parts 34, apart from the function disclosed, i.e. of keeping the fixed and mobile plates 5, 8 closed, prior to tapping and during this process, in which the expansion of the plates takes place, enable a hing effect, since if the relevant coupling bar 20 at one of the sides is disengaged from its associated fingers 33, the assembly pivot about the coupling bar 20 on the opposite side. This pivotting enables the device to be opened to provide direct access inside it, to check the installation and, if necessary, to replace worn parts.

It will be noted that the forces of the springs 35 are applied to the actual springholder 34 in which they are housed and to the pin 36 around which the spring-holders 34 pivots to release the coupling bar 20.

The forces of the springs 35 are transmitted to the fingers 33, which are integral with the spring-holder 34 and which in their working position engage their respective coupling bars 20 which form part of the main support housing 1 3 through the side 32 of the latter.

This enables the device to remain closed in its working position at the desired pressure, to avoid leakage through loss of airtightness, since the said springs 35 will have been previously prestressed and will offer a degree of elasticity which will allow expansion and contraction, produced through the effect of heat, in the parts affected, whether they are metal or refractory, without stresses, since this expansion is absorbed by the springs 35.

The prestressing and dimensions of the springs 35 is calculated in advance, so that they allow pressure between the refractory plates, in the working position, of approximately 7.5 kg per cm2, which means a total force applied of approximately 4,200 kg., implying a stress per spring, in the working position, of approximately 525 kg. Regarding their operation once prestressed, this will be calculated so that they do not start to work until the fingers 33 come into contact with the sliding surface of the respective coupling bars 20. The dimensions of the slots 37 are such that when the spring-holder parts 34 are pivotted out of engagement with the bars 20 the springs 25 do not press on the pin 36, thus allowing the parts 34 to fold back freely without friction.

The compression of the springs 35 from their free set position to their working position, is approximately 5 mm. Logically, there is an intermediate position of greater compression between these two positions, as can be gathered in detail on observing the profile of the fingers 33 in Figure 4, thus ensuring that the device does not open accidentally. The slot 37 has a 5 mm.

clearance on each side of the pivoting pin 36, i.e. a total of 10 mm., which allows the spring-holder part 34 to move over the anticipated thermal expansion.

With the principle disclosed, a resilient closure is obtained, at the desired pressure, in a single movement without requiring more joints or torque wrenches which complicate the system. This effects a considerable saving in maintenance, inspection and, especially, possible problems caused by the human factor. The figures disclosed herein are calculated taking all the factors of the system into account, such as the static pressure of the liquid at maximum load, the actual weight of the assembly and possible inertial blows, with their respective safety coefficients.

The dimensioning and materials of the assembly have also been studied to avoid strains and to withstand maximum stresses produced by this type of work, subject to so much strain and affected basically by heat.

Also, the different refractory parts forming part of the system have been thoroughly studied, so that they form a dimensionally balanced assembly, and to get the maximum economic production performance out of them, always bearing in mind factors of safety and human error, with a priority nature.

Claims (11)

1. An outlet gate closure for use with liquids at high temperatures, comprising first and second plates having through bores, said first plate being adapted to be sealingly and fixedly secured to a container for a high temperature liquid, and means for moving said second plate in sliding and sealing contact with said first plate in either direction from a position in which said bores are aligned, to positions in which flow of liquid through said bores is prevented.

2. A closure as claimed in claim 1 in which said means for sliding the second plate comprises a fluid pressure operated piston and cylinder arrangement.

3. A closure as claimed in claim 1 or claim 2 which includes a nozzle aligned with the bore in said first plate, said nozzle having an annular boss of keystone-shaped cross section which engages a complementary recess coaxial with the bore of said first plate, said nozzle being sealingly secured to said first plate.

4. A closure as claimed in any preceding claim in which said first plate has a protective metal element extending around its periphery, said metal element having an angle section which provides a flange directed inwardly of said first plate.

5. A closure as claimed in any preceding claim in which said second plate has a protective metal element extending around its periphery, said metal element having an angle section which provides a flange directed inwardly of said second plate.

6. A closure as claimed in any preceding claim which includes an outlet pipe aligned with the bore in second plate, said outlet pipe having an annular boss of keystone-shaped section which engages a complementary recess co-axial with the bore of said second plate, said outlet pipe being sealingly secured to said second plate.

7. A closure as claimed in any preceding claim in which said second plate is supported on a housing, and which includes springs cooperating with said housing for urging said second plate into sealing contact with said first plate, whereby thermal expansion of components of said closure is absorbed by said springs.

8. A closure as claimed in claim 7 in which said springs act between a relatively fixed structure and fingers which are engageable with projections on said housing, said fingers having a profile which causes the force applied by said springs to be a maximum as said projection pass an intermediate part of said profile when moving towards full engagement with said fingers, so as to retain said projections in their fully engaged positions.

9. A closure as claimed in claim 7 or claim 8 in which said fingers are mounted on said relatively fixed structure for limited linear movement relative thereto, and for pivotal movement to permit said projections to be disengaged.

10. A closure as claimed in claim 9 in which said springs act on said housing at locations thereon on opposite sides of the bore in said second plate, and said housing is pivotable about the interengagement of said projections and said fingers on one of said sides.

11. An outlet gate closure for use with liquids at high temperatures, substantially as hereinbefore described with reference to and as shown in Figures 1 to 3 or Figure 4 of the accompanying drawings.