GB2023784A - Gate valve for ladles - Google Patents

Abstract

A valve plate for a gate valve for controlling the flow of molten metal is formed from two or more identical ceramic plate sections (25) having mating semi circular recesses (26) to enclose and lock in position one or more tubular ceramic nozzles (45,48). The plate sections and nozzles are held together and supported by a metal case (41) which in the bottom valve plate shown in Fig. 7 has depending, metallic tubular casing sections (50) to encase the lower portions of nozzles (45,48) and lower nozzle extensions (52,54) which are releasably mounted by bayonet fittings in the casing sections (50). <IMAGE>

Description

SPECIFICATION Gates valves The present invention relates to gate valves for controlling molten metal flow and has particular, but not exclusive reference to rotary gate valves of the character disclosed in U.S. Patent 3,780,916; 3,912,134; and 3,764,047 all found in United States Classification 222, with varying subclasses.

In addition to the above-described patents, German Publication 2,411,800 and Swiss Patent 374,454 also discloses rotary valves all of which are basically provided for presenting two different nozzles or pour tubes to a single teeming opening at the bottom of a teeming vessel. The principle advantage of a rotary type valve is to provide a greater length of travel of the imperforate portion of the rotating member than with a reciprocating type valve, to the end that erosion and break-out can be reduced.

High manganese steels are highly erosive.

In a shop with a 300 ton ladle, where five ton ingots are being poured, 60 separate shut-offs are required in order to empty the ladle. A typical reciprocating sliding gate will not last for this many shut offs. Accordingly the advantage of a rotary valve, where that many shut-offs can be achieved, is self evident. The valves of the prior art, however, are of special construction, and do not provide for the easy and quick replacement of nozzles.

Another problem faced in teeming molten metal is a freezing of the metal at the lower edge of the pour tube. This phenomenon is referred to as bugging. Once bugging begins, the original build-up of frozen metal provides a surface for additional build-up. By utilizing low conductivity material, the phenomenon of freezing or bugging can be dealt with successfully, but such a material erodes more rapidly and consequently such a nozzle should be replacable during the life of the valve. In addition, if a replaceable lower nozzle is provided, a smaller hole can be used to start the pour with a high head and, as the head is reduced, the erosion will open the hole and thus maintain an even, teeming rate.

When using a submerged tube when the vessel is clogged it is very difficulty to open for a pour. With a rotary valve having a short tube an oxygen lance can be used to open and then the valve rotated to commence the pour through the submerged tube. The sub merged tube may also be attached after the ladle is filled using the same bayonent type attachment.

In accordance with a feature of the invention there is provided a valve plate made from a plurality of components, suitable for use in a gate valve for controlling molten metal flow, the components of the valve plate comprising a metallic housing for a first ceramic component which is a ceramic plate formed from a plurality of edgewise abutting, identicallyshaped plate sections which together define at least one opening in the said ceramic plate, a second ceramic nozzle component of the valve plate being seated in the opening and having a teeming aperture therein, the said components including a means for mechanically securing the apertured component to the ceramic plate.

With this arrangement replacement of the component defining the teeming aperture is facilitated and those skilled in the art will appreciate that the arrangement may be applied to sliding gate valves as well as to rotary gate valves.

The modular construction of the valve plates also facilitate selection of suitable materials for the apertured ceramic components, by reference to the erosion resistance and conductivity suitable for pouring different molten metals.

The invention also provides a rotary gate valve including valve plates of the construction specified above, and a method of making a valve plate for a gate valve, comprising assembling a plate member from two or more identical flat plate sections, each having indentations in neighbouring edges, with a nozzle component located in en opening defined by the indentations when the said edges are abutted, and securing the plate sections and nozzle component inside a metal case.

This method effectively permits the insertion of larger and smaller bore diameter nozzle extensions as well as the utilization of low conductivity, inserts to combact freezing and bugging which would otherwise occur in pouring certain steels with a high conductivity ceramic having better erosion characteristics.

The invention also provides a method of accommodating deflection in a rotary gate valve having a stationary top plate, and a rotary gate having one or more depending nozzles comprising the steps of, retaining the stationary top plate and the rotary gate within a frame, providing a plurality of uniformly dispersed load pads interiorly of the frame and bearing upon the combination of the rotary gate and top plate, dispersing said load pads in surrounding, and, disposing the load pads adjacent the periphery of the rotary gate and top plate, whereby the pressure of the load pads causes the rotary gate to deflect into a position conforming to the warpage of the top plate resulting from warpage of the top plate backing.

Further features of the present invention will become apparent as the following description proceeds, taken in conjunction with the accompanying illustrntive drawings in which: Figure 1 is a front elevation of a lower portion of a pouring vessel utilizing a rotary valve in accordance with the present invention.

Figure 2 is a bottom view of the rotary gate valve of Fig. 1 and showing the same in the same scale.

Figure 3 is a transverse sectional view of the rotary valve of Fig. 2 taken along section line 3-3 of Fig. 2 showing the interior portion of the differing diameter nozzles in the rotary gate.

Figure 4 is a longitudinal sectional view taken along section line 4-4 of Fig. 2, showing in phantom lines the open and closed configuration of the rotary gate frame.

Figure 5 is a horizontal section taken along section line 5-5 of Fig. 3 showing the interior portion of the rotary valve and more particularly the gear mechanism for driving the same.

Figure 6 is an exploded perspective view illustrating the method of forming the top plate from two identical members.

Figure 7 is an exploded perspective view of the method of forming a rotary gate with two nozzles utilizing the two plate members also used in connection with the top plate, and further illustrating the method for removing the two lower nozzle extensions.

Figure 8 is an exploded perspective view of the rotary gate like Fig. 7 but directed to an alternative embodiment having a single nozzle.

Figure 9 like Figs. 8 and 7 is an exploded perspective view of the rotary gate but directed to yet another alternative embodiment having six nozzles.

The present invention finds its principal utility in conjunction with pouring vessel V, such as shown on Fig. 1, the pouring vessel primarily being a ladle for teeming molten metal, usually steel. Nonetheless other molten metals are contemplated. The rotary valve R, as shown in Fig. 1, is positioned beneath the vessel V, and has a single pouring opening operative at any one time extending beneath the casing 1 6 as shown in Fig. 1. More specifically, as viewed from the bottom, as shown in Fig. 2, the rotary valve R has a nozzle extension 52 with a large pour opening and a nozzle extension 54 with a small pour opening extending beneath a support ring 62 for the rotary gate carrier 61 Turning now to Fig. 3, it will be seen that the vessel V includes a metal shell 10 as its outer portion, and an interior refractory lining 11.A hble is provided in the lower central portion of the refractory lining 11 for the mounting of a well block 12, which further contains interiorly thereof a working nozzle 14, which is in teeming communication with the bottom of the vessel V.

Desirably a safety collar 1 5 is provided peripherally around the working nozzle 14, and is secured to the frame 1 6 and its mounting plate 1 8. The casing 16 of the rotary valve R extends around the rotary valve 5, but its upper portion 18 defines the mounting plate which, as seen in Fig. 4, is secured to the metal shell 10 of the pouring vessel V by means of mounting bolts 19.

A top plate 20 (as seen in Fig. 3) is positioned within a top plate blcok ring 1 7 which depends from the mounting plate 1 8. A rotary gate 40 is positioned beneath the top plate 20, and held thereagainst by means of the pressure devices 60 which are mounted within the rotary gate carrier 61. The rotary gate carrier, in turn, has a lower face which is positioned a top the support ring 62 which is secured by bolts (not shown) to a rotary gate frame 63. Further as will be noted in Fig. 3, a splatter shield 64 is provided in surrounding relationship to the nozzle cases 50.Provision for removing the top plate 20 as well as the rotary gate 40 is shown in Fig. 4 where it will be seen that the rotary gate frame 63 is secured within the casing 1 6 by means of a pivot toggle 65 secured to the mounting plate 18, which has a pivot toggle actuator 66 permitting the same to be pivoted to a distance in greater space relationship from the mounting plate 18 than in normal operation.

Similarly, at a station on the opposite side of the rotary gate frame 63 provision is made for a latch toggle 68 which is engaged by a latch toggle activator 69, permitting a lowering and tilting of the rotary gate frame 63 to a position such as shown in phantom lines in Fig. 4 for removal and servicing.

Turning now to Fig. 5 it will be seen that the rotary gate carrier 61 has a bull gear 70.

A rotary gate recess 72 is provided interiorly of the bull gear 70, and receives the rotary gate 40, the same being secured in place by means of the flats in the rotary gate recess which engages corresponding flates 44 on the rotary gate and the curvilinear portion 42 on the rotary gate as shown in Fig. 7. The bull gear 70 is driven by means of a drive pinion 75 the peripheral teeth 74 of which engage the teeth 71 of the gear 70, and through a drive mechanism 76 (see Fig. 2) the drive pinion 75 is actuated to perform a rotation of the rotary gate 40.

The specific construction of the top plate 20 is highlighted in Fig. 6 where it will be seen that a metallic case 21 is provided having opposed curved depending side walls 22, and opposed locking flats 44. A pair of identical refractory plates 25 are provided, each of which has two semi-circular recesses 26 containing a locking collar 28 and an undercut 29. A top plate nozzle 30 is engaged by two of the opposed semi-circular recesses 26, the top plate nozzle 30 having a pour opening 31 at a central portion, and a locking groove 32 around its periphery, the locking groove being engaged by the opposed locking collars 28 of the semi-circular recesses 26 in the refractory plates 25.This permits the upper portion of the top plate nozzle 30 to extend above the metallic case 21, and (as shown in Fig. 3) be received by the safety collar 1 5 provided beneath the working nozzle 14 of the teeming vessel V. The safety collar ring 34 of the top plate nozzle thus is secured to the principal teeming opening in a safety relationship. Also to be noted is the provision of a top plate plug 35 which also has a locking groove 36, which is received by the opposed locking collars 28 of the refractory plates 25 and which engage the locking grooves 36. The mount lock extension 38 of the top plate plug 35 fits within a plug recess 33 provided at a lower portion of the mounting plate 1 8 as shown in Fig. 3.Nozzle access ring 37 and plug access ring 39 are provided in the metallic case 21 and the parts when assembled are mortared into and securely bound within the metallic casing 21 to thus define a completed top plate 20.

Turning now to Fig. 7 it will be seen that a rotary gate 40 also contemplates a metallic case 41, and the utilization of the same identical refractory plates 25 as utilized in the top plate 20, and where parts are common, common reference numerals will be employed. The refractory plates 25 thus employed in the rotary gate 40, also are provided with a semi-circular pair of recesses 26, and a locking collar 28 with a corresponding undercut 29. The metallic case 41 has curved side walls 42, as well as opposed locking flats 44. Provision is made for a large bore nozzle 45 having a locking groove 46, which is matingly engaged by one of the locking collars 28 of the opposed refractory plates 25.

The large bore nozzle 45 is proportioned so that its upper surface does not extend above the upper surface of the opposed refractory plates 25. Corresondingly, a small bore nozzle 48 is provided having a locking groove 49 which similarly is engaged by the opposed locking collars 28.

The small bore nozzle 48 portion of the rotary gate 40 also has a locking groove 49, which is engaged by the opposed locking collars 28 of the refractory plates 25. Both of the nozzles 45, 48 extend downwardly through nozzle access rings 59 in the metallic case 41. Both of them extend into the depending nozzle cases 50 which have an extension lock 51 at their lower portion. When the rotary gate 40 is assembled, it may or may not contain the large bore exentsion 52 and the small bore extension 54 as shown. The opposed refractory plates 25 and the nozzles 45, 48 are securely mounted into plate within the metallic case 41 to thus define the rotary gate 40. As pointed out earlier, the type of ceramics as well as the size of the bore of nozzles 45,48 can be preselected for the particular pouring conditions.In addition, a large bore extension and small bore extension 52,54 may be secured independently interiorly of the nozzle case 50 and locked by means of the extension lock 51 because, as shown, each of the extensions 52,54 is provided with a lock undercut 55, and;a lock shoulder 56 which finds itself positioned above the extension lock 51 of the nozzle case 50 and rotate it until engaging the lock stop 58. Thus each of the extensions 52, 54 may be removably secured beneath the permanently installed nozzle 45, 48 either immediately prior to use, at the-time of shipment, or during the course of use based upon the amount of erosion or other damage which may occur to the extension.

Single Nozzle Embodiment As shown in Fig. 8 a single nozzle rotary gate 80 plate (not shown) can be fabricated having only one teeming opening 81. This permits the use of larger bores within a given outside configuration or even in an existing valve. As an example the illustrated single hole gate 80 may have a nozzle as large as 7 inches and yet it fits within the outer dimension of a two hole gate that is limited to a maximum bore of 5 inches. The flow rate of the 7 inch bore is twice that of a 5 inch bore.

This increase in available flow rate would allow application of the valve to charging ladles torpedo cars, and even to furnaces.

SIX NOZZLE EMBODIMENT The six hole gate 90 shown in Fig. 9 provides at least two functional advantages.

The use of several different bore sizes allows uniform teeming rates when the ladle is full as well as when it is nearly empty without throttling or at least with minimal throttling. Metalurgical quality of steel ingots is adversely effected by both non-uniform teeming rates and by the flaring stream that results from throttling. Too fast or slow a fill rate is detrimental to ingot quality. A flaring stream reoxidizes during teeming resulting in ingot inclusions and a flaring stream sticks to ingot mold sidewalls and results in poor surface quality. Continuous cast steel also suffers from re-oxidizing due to a flaring stream and absolutely demands a constant teeming rate in order to maintain constant withdrawal rate from the mold.

The use of multiple bores provides more "shutoffs" between plate changes saving time and permitting teeming of more smaller ingots from a given ladle size.

As illustrated in Fig. 9, the six hole gate has two series of three bore sizes. As an example these are 2 1/1" 91, 1 3/4" 92 and 1 1/4" 94. The 1 3,4" inch allows flow rates of one half the 2 1i2 inch and the 1 1 /4 inch would provide flow rates of one half the 1 3,4 inch or one quarter the flow rate of the 2 1i2 inch.

MATERIALS The preferred material for the plates is a highly shock-resistant refractory that also has a high abrasion resistance. Generally this is an 85 to 95% alumina refractory body made from tabular alumina. The material used for the nozzle in the top plate must be highly erosive resistant. The top plate assembly shown keeps the amount of material in the orifice nozzle to a minimum which permits the economical use of some of the more expensive refractory materials such as the zirconium oxides.

The material used for the gate nozzles also must be highly abrasion resistant. The thru bore design shown allows the nozzle, which is all that is exposed to the flowing stream, to be of a different material than the plates.

The assemblies illustrated allows use of different materials in the top plate nozzle and gate nozzles. These can be varied to better accomodate the steel to be teemed. A few examples of this are outlined below.

Aluminum killed steels are soft and do not abrade refractories but rather they tend to precipitate aluminum oxide which adheres to the refractory and restricts the flow. A low alumina, clay type refractory can be used for these grades as they are less expensive, better insulators, resist aluminum oxide deposits and the fact that they are poor from an errosion resistant standpoint is not a disadvantage with these grades of steel.

Rimming grades of steel contain much dissolved oxygen and they chemically errode many refractories. In some cases it has been found that magnesium oxide or "basic" refractories resist this action best.

High manganese grades of steel and particularly those having high manganese and high carbon are highly abrasive and "acid" refractories of the high alumina type or even zirconium oxides resist this best.

The generally preferred material for the gate nozzle extension is a good insulator to reduce "bugging" or freezing of the teeming steel on the edge of the extension orifice. When this occurs the stream is deflected and flared badly causing an increase in reoxidation. Most good insulators are not highly errosion resistant so extensions of these materials need to be replaced before the other refractories of the gate and top plate. The bayonet attachment allows this to be done easily and quickly.

When a submerged pouring tube or long tube is used, it is attached in the same manner and then lowered so that its discharge end extends into the molten pool below.

These tubes are generally made of one of two materials. Fused silica tubes are used with aluminum killed and other low abrasive steels as they have good shock resistance so that they do not require preheating and they minimize aluminum oxide deposit problems being non-alumina and an excellent insulator. Alumina graphite tubes must be used with highly abrasive steels such as high manganese, high carbon grades even though they require preheating before installation.

THE METHOD The method of the present invention, as summarized above, is directed primarily to a sequence of steps whereby identical refractory plates 25 can be employed with a top plate metallic case 41 and a rotary gate metallic case 41 to economically fabricate the replaceable parts of a rotary gate R. The economies are achieved by means of utilizing a single identical refractory plate 25 to define the interface between the top plate 20 and the rotary gate 40. By selecting a particular type top plate nozzle 30, the top plate nozzle 30 may have a pour opening 31 in accordance with the use intended, as well as a ceramic material with the erosion, conductivity, and other properties desired for the operation. Similarly, the top plate plug 35 may be formed of the ceramic of the choice for the particular pour.Once the selections of the top plate nozzle and top plate plug are made, the parts are secured in place within the metallic case 21, mortared for a secure connection therewith, and then desirably ground to provide a smooth surface at the interface between the top plate 20 and the sliding gate 40. Further as pointed out above, both the top plate plug 35, and the top plate nozzle 30 extend upwardly through the nozzle access ring 37 and plug access ring 39 for their ultimate secured relationship with the mounting plate 18 as shown in Fig. 3.

The method of forming the rotary gate 40, as illustrated in Fig. 7, contemplates using the same identical refractory plates 25 as used with the top plate, and thereafter selecting nozzles 45, 48 with the appropriate bore or pouring diameter, as well as material, for the intended operation. Thereafter the two top plates 25 are pressed into position to lockingly engage the nozzles 45, 48 and the same are mortared into the metallic case 41. Thereafter, different extensions 52, 54 may be positioned in the nozzle case 50, again with the pour diameter or through bore being preselected for the particular operation involved, as well as the material.

The method of forming a single nozzle rotary gate and top plate, as shown in Fig. 8, is essentially the same. When more nozzles are employed, such as six as shown in Fig. 9, a second diamond shaped section 95 is employed but used in opposed relationship to itself against the locking flats 95.

Often it is desirable to use a submerged pour tube or nozzle. They can be used in conjunction with a short tube or nozzle such as in the two nozzle embodiment.

In the event the steel becomes frozen in the pouring vessel, the short tube is positioned in the operating configuration, arid an oxygen lance applied thru the short tube in order to open or start the pour. Thereafter, the submerged tube is rotated into position, and pouring continues. It is virtually impossible to oxygen lance through a long, submerged tube, some such tubes being as long as 4 and 5 feet.

The extension can be replaced during a pour in the shutoff condition by using a remote handling device, the operative portion of which is essentially a screw extractor. The extensions are preferably mortared in with a non-binding type clay mortar which renders removal and replacement easy.

Also, as shown in Fig. 9, it is possible to fabricate the gate plate of three or more pieces, thereby having more than two depending nozzles. As the number of nozzles are increased, naturally the shutoff distance upon rotation is decreased, and there comes a time, depending upon the radius of rotation where further pouring tubes become impractical.

Nontheless, the invention is capable of such variations.

THE METHOD OF SEALING A further problem addressed by another aspect of the present method arises from the warpage of the back plate 1 8 of the rotary valve assemblage "R". In virtually all valve installations, even though the steel back plate behind the stationary top plate is some three inches thick, at temperatures of 900"F, this temperature is some 300 above the "creep" temperature for steel. Accordingly during successive pours, the back plate or steel casing 10 of the vessel, as well as the back plate 1 8 of the valve is inclined to warp at a rate and intensity which is not predictable. Nor can this be controlled adequately by known forms of cooling.

To accomodate the above problem, it is contemplated that the rotary valve top plate 20 which is stationary, as well as the rotary gate 40 are spring loaded in such a fashion as to cause a deflection corresponding mutually with the deflection or warpage of the back plate, to the end that the interface between the two ceramic members will be in constant fluid tight pressure relationship. This method is carried out through the means of a plurality of load pads 60, distributed as shown best in Fig. 5 (in conjunction with Fig. 3) in such a manner that they surround the nozzles, as well as uniformly or dispursed over the ceramic members.

Although particular embodiments of the invention have been shown and described in full here, there is no intention to thereby limit the invention to the details of such embodiments. On the contrary, the intention is to cover all modifications, alternatives, embodiments, usages and equivalents of the subject invention as fall within the spirit and scope of the invention, specification and the appended

Claims (28)

claims. CLAIMS

1. A valve plate made from a plurality of components suitable for use in a gate valve for controlling molten metal flow, the components of the valve plate comprising a metallic housing for a first ceramic component which is a ceramic plate ormed from a plurality of edgewise abutting identically shaped plate sections which together define at least one opening in the said ceraic plate, a second ceramic nozzle component of the valve plate being seated in the opening and having a teeming aperture therein, the said components including a means for mechanically securing the apertured component to the ceramic plate.

2. A valve plate according to claim 1, wherein the ceramic plate is formed from at least two plate sections having semi-circular indentations in abutting edges thereof to form the at least one opening.

3. A valve plate according to claim 1 or 2 suitable for use as a top plate, wherein the ceramic plate has two openings, the nozzle component being seated in one opening and a third ceramic component of the valve plate, which is an imperforate plug, being seated in the other opening, the plate, second and third components including interlock means for mechanically securing the second and third components in their respective openings.

4. A valve plate according to claim 1 or claim 2, suitable for use as a bottom plate, wherein the ceramic plate has two or more openings and seated in each is a ceramic nozzle component having a teeming aperture therein, and respective means mechanically secure the nozzle components in their respective openings.

5. A valve plate according to any of claims 1,2 or 4 including a further ceramic component, comprising a tubular ceramic member or nozzle end piece for the or each nozzle component to form an extended teeming passage therewith, and one or more depending sleeve elements forming part of the metallic housing to encase the or each nozzle end piece, which is lockable in place against the nozzle component.

6. A valve plate according to claim 5, wherein the nozzle end piece is lockable against its associated nozzle component by a bayonet locking means which secures the end piece into the associated sleeve element.

7. A valve plate according to claim 6, wherein the bayonet locking means comprises undercuts in the nozzle end piece and mating inward protrusions in the sleeve element.

8. A valve plate according to any of claims 1 to 7, wherein the means, securing in the or each opening the associated ceramic component,comprises a central peripheral groove in the latter components and an interfitting locking collar of the opening, the said component when secured to the ceramic plate protruding from at least one face of the ceramic plate.

9. A valve plate for a gate valve for controlling molten metal flow, substantially as herein described with reference to and as shown in Fig. 6 or Fig. 7 or Fig. 8 or Fig. 9 of the accompanying drawings.

10. A gate valve, for controlling molten metal flow, which includes a valve plate as claimed in any one of the preceding claims.

11. A rotary gate valve for controlling the teeming of metal from the lower portion of a teeming vessel having an aperture therein, comprising a frame for securing the valve to the lower portion of the teeming vessel, a rotary drive means positioned within the frame for operating the valve, a top plate in teeming communication with the vessel aperture, the top plate having a ceramic nozzle insert therein secured to two or more abutting ceramic slabs which form the plate, a rotary gate comprising a metallic case having a depending sleeve portion for a ceramic pour tube two or more abutting ceramic plates in the case and a pour tube secured in a seating therefor provided by an opening defined by the ceramic plates, the valve including means engageable with the rotary drive means for rotating said rotary gate in fluid tight relationship to the underside of the top plate to control or terminate teeming by rotation of the rotary gate.

1 2. A valve according to claim 11, wherein the nozzle insert is mechanically interlocked to the abutting ceramic slabs.

1 3. A valve according to claim 11 or claim 12, wherein the pour tube is mechanically interlocked to the abutting ceramic plates.

14. A valve according to any of claims 11,12 and 1 3 wherein the abutting ceramic slabs and the abutting ceramic plates are identically shaped.

1 5. A valve according to any of claims 11 to 14, wherein the nozzle insert and the pour tube each have a central peripheral groove and each is mechanically interlocked with a locking collar coextensive with respective receiving openings in the top and rotary plates.

1 6. A valve according to any of claims 11 to 15, further including a removable and replaceable ceramic member comprising an extension of the said pur tube.

1 7. A valve according to claim 16, including bayonet fastening means for releasably securing the replaceable pour tube extension to the pour tube.

1 8. A valve according to claim 17, wherein the bayonet fastening means comprises inward protrusions from the depending sleeve portion of the rotary gate case and undercuts in the pour tube extension engageable by the protrusions.

1 9. A valve according to any of claims 11 to 1 8 wherein the top plate has two openings defined by the ceramic slabs, the nozzle insert being seated in one opening and an imperforate plug in the other, mechanical interlocking means being furnished respectively to lock the insert and the plug in their associated openings.

20. A valve according to any of claims 11 to 19, wherein the ceramic plates forming the rotary gate define two or more openings in each of which an associated pour tube is seated and mechanically secured by respective interlocking means.

21. Rotary gate valve substantially as herein described with reference to and as shown in Figs. 1 to 6 or Figs. 1 to 6 when modified by substituting the rotary gate shown therein by the rotary gate shown in Fig. 7 or Fig. 8 or Fig. 9 of the accompanying drawings.

22. A method of making a valve plate for a gate valve, comprising assembling a plate member from two or more identical flat plate sections, each having indentations in neighbouring edges, with a nozzle component located in an opening defined by the indentations when the said edges are abutted, and securing the plate sections and nozzle compoent inside a metal case.

23. A method according to claim 22, wherein the plate sections together define more than one opening, the nozzle component being secured in one of the openings and an imperforate plug being secured in the or each of the remaining openings.

24. A method according to claim 22, wherein the nozzle component is a pour tube and is assembled to the plate sections so as to depend therefrom, the metal case being furnished with a depending sleeve and the pour tube is located inside the depending sleeve.

25. A method according to claim 24, wherein the said sleeve is provided with means to secure a nozzle extension piece to the pur tube, and a nozzle extension piece is removably fitted into the sleeve.

26. A method according to any of claims 22 to 25, for making either top or bottom slide plates, which uses identical plate sections irrespective of whether a top or a bottom plate is being made.

27. A method of accomodating deflection in a rotary gate valve having a stationary top plate, and a rotary gate having one or more depending nozzles comprising the steps of, retaining the stationary top plate and the rotary gate within a frame, providing a plurality of uniformly dispersed load pads interiorly of the frame and bearing upon the combination of the rotary gate and top plate, dispersing said load pads in surrounding relationship to the nozzle in its pour configuration, and disposing the load pads adjacent the periphery of the rotary gate and top plate, whereby the pressure of the load pads causes the rotary gate to deflect into a position conforming to the warpage of the top plate resulting from warpage of the top plate backing.

28. A method of making a valve plate for a gate valve, substantially as herein described with reference to the accompanying drawings.