FIELD OF THE INVENTION

The present invention relates to an apparatus for heating a pipe that is used to transfer molten metal. In particular, the present invention is directed towards an apparatus for cleaning or unblocking a metal transfer siphon pipe.

BACKGROUND OF THE INVENTION

The present invention will be described with particular reference to a method of heating cast iron siphon pipes of the types used to transfer molten aluminium. However, it will be appreciated that the device of the present invention may be used for heating any suitable type of pipe used to tansfer any molten metal and no limitation is intended thereby.

In the metal processing industry, metal pipes are often used to transfer molten metal between crucibles and pots. In the aluminium industry, alumina is reduced in reduction cells known as pots. Molten aluminium is tapped using a tapping siphon from the base of the pot into a crucible which is then transported to the cast house, in which U shaped siphon pipes transfer molten aluminium from the crucible to holding furnaces. The siphoning action is controlled by a vacuum that is applied via a metal vacuum head to an opening in the U bend portion of the pipe.

In Australia, an automated aluminium siphoning system for transferring aluminium from crucibles to a holding furnace has been developed. The system has been designed to suit a smelter cast house arrangement with holding furnaces aligned adjacent to a hot metal delivery passage. Siphon pipes are parked overhead in the hot metal passage line with each furnace. When parked on stand-by, gas fired pre-heat burners maintain the pipes at a temperature to eliminate moisture, reduce metal chill and minimize thermal shock to the cast iron siphon pipes. When a crucible of metal arrives on a hot metal carrier, the siphon pipe is lowered to simultaneously enter the crucible and the holding furnace by a push button operation. The crucible is tilted to about 5- to concentrate the metal under the pipe inlet and so minimize the residual metal heel. Once the siphon pipe is in position, the siphon vacuum sequence is started which automatically empties the crucible at a controlled rate. When the crucible becomes empty, the vacuum is automatically released and the siphon pipe is returned home to its parked position.

A major problem with the use of siphon pipes to transfer molten metal is that the pipes are prone to becoming blocked due to build up of solidified aluminium Whilst pre-heating as described above, can reduce the amount of aluminium solidifying in the pipe, over time a degree of aluminium does build up in the pipe. Still further, impurities such as dross have a higher melting point than aluminium and simply pre-heating a pipe to about the melting point of aluminium will not avoid dross solidifying in the pipe. Thus, siphoning procedures are designed to minimize the amount of dross entering the siphon pipe- Regular cleaning and maintenance is required to avoid siphon pipe blockage. Reaming drills are used to periodically clean the siphon pipes. However, the process of cleaning the pipes takes time and whilst being cleaned the pipes are out of service. Thus, there is a compromise between cleaning and maintaining a high level of production. Over a period of time, siphon pipes inevitably become blocked to such an extent that they cannot be cleared by the reaming drills. Cast iron siphon pipes are expensive and it is desirable to be able to unblock the pipes for re-use. One method to unblock the pipes is to heat the pipe to a temperature above the melting point of aluminium so as to remelt the aluminium which then may flow from the pipe. Heating is performed by wrapping the pipe in an electric heating. Such a process consumes a large amount of errergy, is labour intensive and removes the pipe from operations for a period of time. It is known in the art of molten metal processing to induction heat and/or insulate stationary metal transfer pipes to reduce heat loss and to minimize metal solidification within the pipe. Such stationary pipes have one or both ends fluidly connected to another metal transfer pipe or metal holding fluid . It is clearly not possible to modify a pipe that in use is moveable between a metal transfer position and an isolated rest posrtion such that it is insulated and/or heated.

It is therefore an object of the present invention to provide an alternative device and method for heating molten metal transfer pipe.

SUMMARY OF THE INVENTION

According to a first broad from of the invention there is provided an apparatus for heating a molten metal transfer pipe, the apparatus having;

a heating chamber, an access opening through which a pipe can be positioned : within and removed from the chamber, an access opening closure device, and the chamber is inclined to provide a lower end and an upper end;

a heat source located at or near the lower end ; and

a vent located at or near the upper end.

The heating chamber typically has an open top defining the access opening so that the pipe can be lowered into and lifted from the chamber by a suitable lifting device. The access opening closure device may be a hinged door or cover. Alternatively, the cover may be completely detached from the chamber. The access opening closure device may be formed froma number of individual parts which may be opened and closed independently. This reduces the weight of the closure section to be removed.

The heat source is preferably a gas burner and an atmospheric burner is particularly suitable. In this case, the chamber includes a burner port to introduce heat from the burner into the chamber. The apparatus may include one or more further heat sources located between 1he upper and lower ends. Typically, the chamber has a shape that corresponds to the shape of the pipe. As understood in the pipe arts,, shape of a pipe refers to whether the pipe is straight, U shaped, S shaped, curved or the like. Thus, the chamber will correspondingly be straight, U shaped or otherwise curved to match the curvature of the pipe.

According to a further broad form of the invention there is provided an apparatus for heating an uninsulated moften metal transfer pipe, the apparatus having;

a heating chamber, an access opening through which a pipe can be positioned within and removed from the chamber, an access opening closure device, and the chamber is inclined to provide a lower end and an upper end;

a heat source located at or near the lower end ; and

a vent located at or near the upper end.

Preferably the chamber is sized . and dimensioned to accommodate the pipes such that the distance between the outer walls of the pipe to the inner walls of the chamber are less than a distance corresponding to a distance equal to about 3 times the external diameter of the pipe, preferably a distance equal to about 0.5 to about 2 times the external diameter of the pipe, preferably a distance equal to about 0.75 to about 1.25 times the diameter of the pipe.

Typically, the chamber has a pipe support for supporting a pipe above the base of the chamber. This can protect the surface of the pipe from damage that may lead to corrosion, further, lifting the pipe above the base of the chamber allows air to flow around the full circumference of the pipe. Typically the pipe support includes a series of paced stools or supports having a convex pipe supporting surface.

When the pipe is a metal transfer siphon pipe, the chamber is U shaped with two upwardly Inclined leg sections joined together by an upper U-bend section. Preferably, in this case, a heat source is located at the .lower end of each leg. Most preferably, additional heat sources are located at one or more positions on one or both. The vent is located in the U bend section.

According to a further broad form of the invention there is provided an apparatus for heating U shaped molten metal transfer pipe, the apparatus having;

a U shaped heating chamber, an access opening through which a pipe can be positioned within and removed from the chamber, an access opening closure device, and the chamber is inclined to provide a lower end and an upper end; a heat source located at or near the lower end; and

a vent located at or near the upper end.

The heating chamber is inclined, typically at an angle of between 10° and 45° to the horizontal preferably about 20' to about 30' to the horizontal

The heating chamber is suitably lined with a refractory material. Such materials are known in the art. A preferred material is kaowool.

In an alternative form of the invention, the heating chamber may not necessarily be inclined but may be formed so that the pipe is inclined. For example,, the chamber may have an inclined base or inclined internal supports

According to a further broad form of the invention there is provided an apparatus for heating a molten metal transfer pipe, the apparatus having;

a heating chamber corresponding in shape to the pipe to be heated, an acess opening through which a pipe can be positioned within and removed form the chamber, an access opening closure device, and the chamber is formed to enclose the pipe such that the pipe has a lower end and an upper end;

a heat source located at or near the lower end of the pipe; and

a vent located at or near the upper end of the pipe. A particular application of the apparatus of the present invention is to heat a pipe block by solidified metal to a sufficient temperature to at least partially melt the metal so a to unblock the pipe.

In the present specification and claims, the term blocked, and its variants, such as block, blockage and the like, with reference to a pipe refers to complete and partial blockage of the pipe sufficient to reduce flow of liquid therethrough.

In the present specification and claims, the term unblock means to completely or at least partially remove a blockage or part thereof from the pipe so as to increase the flow of liquid through the pipe prior to being unblocked.

In use, a pipe to be unblocked is placed in the heating chamber and heated. The pipe is typically heated to at least a temperature at which the metal that the pipe is used to transfer melts.

Typically, the temperature required to clear aluminium blockages in a cast iron ^' aluminium siphon pipe is between about 700° to about 750°, However, the pipe may also be blocked by impurities having a higher melting point than the transfer metal. Difficulties occur when the melting point of the impurities approaches or exceeds that of the pipe. For example, cast iron has a melting point of about 1200°C.

Thus, in a preferred embodiment, the apparatus further includes an impact device for physically impacting a blockage in the pipe. Typically, the impact device includes a rod that can be inserted through a bottom end of -the chamber and into the pipe. The rod may be agitated to clear the blockage. Agitation of the rod may be manual or automatic.

According to a further form of the invention there is provided a method of unblocking a molten metal transfer pipe blocked with transfer metal, comprising providing an apparatus having a heating chamber with a shape with an access opening through which a pipe can be positioned within and removed from the chamber, an access opening closure device, the heating chamber being inclined to the horizontal such that it has a lower end and an upper end, placing the pipe in the heating chamber and heating the chamber to a temperature sufficient to soften or rneft the transfer metal.

Another disadvantage with the use of vacuum operated siphon metal transfer pipes is that in some cases the cooled metal fuses the metal vacuum head to the pipe. In a further preferred embodiment, the heating chamber is complimentary to the shape of a pipe with a fused vacuum head. Alternatively, the apparatus further includes a heating chamber extension that can be removeably attached to the heating chamber. The shape of the extension unit is complimentary to that of the vacuum head. In this way, a fused vacuum head may be heated together with the pipe thereby enabling the vacuum .head to be separated from the pipe.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is an isometric view of a preferred apparatus of the present invention;

Figure 2 is a plan view of the apparatus shown in figure 1 ;

Figure 3 is a front view of the apparatus shown in figure 1 ; and

Figure 4 is a section view of the apparatus shown in figure 1 .

DETAILED DESCRIPTION OF THE FIGURES

Figure 1 shows a preferred apparatus 11 of the present invention. The apparatus is for heating a U shaped aluminum siphon pipe. The apparatus has a U-shaped heating chamber 12 that corresponds to or is complimentary to the shape of the aluminum siphon pipe. The heating chamber has a short leg 13, a long leg 14 and a U-bend section 15. The apparatus has a frame 16 for supporting the heating chamber at an angle of about 10° to the horizontal, with the U-bend section being at the highest point - The heating chamber 12 has four heat inlet ports 17, 18, 19, 20 which may be seen In figure 2. Atmospheric burners are located In the ports. Two ports 17, 18 are located at the end of a respective leg 14, 15. Two further ports 19, 20 are located on either side of the long leg 14.

Adjacent the inlet ports 17, 18 located at the end of the legs are apertures 30 which allow a rod 31 to be inserted into the heating chamber. The apertures are located such that when the rods are inserted, they pass into the interior of the pipe towards a blockage.

A vertical extending exhaust port 21 is located in the U bend section. A side port 22 is also located in the U bend section. The side port 22 is adapted to be connected to a heating chamber extension unit (not shown). The purpose of this extension unit will be discussed below.

Figure 4 shows a cross section of the heating chamber. The heating chamber has a . series of shoes 24 or supports upon which in use a cast iron siphon pipe 25 may rest.

The heating chamber 12 has an upper section 26 that is composed of a number of removable lid sections. Handles (not shown) are provided to allow the sections to be lifted from the base 27. This allows a pipe to be placed on the shoes 24. Typically, a fork lift or other mechanical lifting device may be used to place the pipe in positions. The lid sections are then replaced. The atmospheric burners in each of the ports are ignited and heating commences. The pipe is heated to a temperature at just above the melting point of aluminum but below the melting temperature of the cast iron pipe. The temperature will usually be in the range of between about 700°C to about 950°C When the heating chamber reaches the desired temperature the rods are moved towards a blockage and are manually forced against the blockage. The present inventor has surprisingly discovered that a combination of heating the blockage together with agitating or striking the blockage can clear pipes that would have been unable to be cleared using conventional heating techniques. Blockages that have previously been difficult or not possible to clear are those having a high degree of high, melting point dross, rather than lower melting point aluminium. When heated to temperatures above the melting point of aluminium, the aluminium in the blockage will melt and because of the angle of the pipe within the heating chamber, molten aluminium will run out of the ends of the pipe. The heating chamber is lined with a hard refractory material such as refractory cement at those points where molten metal drains from the pipe. The remainder of the heating chamber is lined with a soft refractory material such as kaowool.

As discussed above, aluminium siphons are charged under vacuum. Vacuum heads are mounted to the U shape bend section of the pipe. If molten aluminium contacts the vacuum head, the head may become fused to the pipe. Generally, when this occurs, both the vacuum head and pipe are rendered inoperable and must be discarded. Pipes having a fused vacuum head may be heated in an apparatus of the present inventor by joining a chamber extension unit to the side port 22 so as to accommodate the fused vacuum head. In this way, the aluminium fusing the vacuum head to the pipe may be melted, thereby freeing the vacuum head from the pipe.

The present inventor has surprisingly found that the heating chamber may be heated to the desired temperature in a very fuel efficient and therefore cost effective manner. Still further, the apparatus of the present invention is able to clear blockages that had previously been considered to be unblockable.

It will be appreciated that various changes and modifications may be made to the present invention as described and claimed herein without departing from the spirit or scope thereof.