Static structures (e.g. – buildings) – Sheetlike element assembled parallel to existing wall,... – For furnace or refrigeration
Reexamination Certificate
2001-02-05
2004-08-31
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Sheetlike element assembled parallel to existing wall,...
For furnace or refrigeration
C052S406200, C052S404200, C052S509000, C052S512000, C110S336000, C110S338000
Reexamination Certificate
active
06782669
ABSTRACT:
This invention relates to a furnace lining. By “furnace” we mean a furnace, kiln, oven or the like where there is a chamber which is heated, and into which articles are placed for heat treatment.
Furnaces tend to be dusty, particularly where there is provided a fan or high velocity burner or the like for circulating hot air within the furnace, and dust is undesirable, particularly in the case of a kiln in which ceramic articles/glazes are fired, or in an oven where vitreous enamel is baked dry. The problem of dust is aggravated where there is provided an insulating lining which is of a fibrous nature which may contain silica, which may also present a potential health hazard if the fibres become airborne.
To reduce the amount of dust contributed by the furnace lining it is common to cover the lining with a protective covering such as high-temperature resistant textile material which is attached to the lining e.g. by pins. Another approach is to cement anchors into the fibres of the insulating lining.
Yet another approach is to attach to the hot face of the lining, i.e. the face of the lining facing inwards of the furnace, ceramic plate-like members. This is used where the underlying lining requires protection from deleterious atmospheres, e.g. aggressive gases such as vanadium pentoxide which can eat away the fibrous lining material.
This latter approach provides the advantage that the ceramic plates, being generally rigid, may be used as supports for, for example, heating elements. Such ceramic plates are typically attached to the hot face with a cement material, but the adhesive effect of such cements tends to deteriorate in use with the effect that the ceramic plates separate from the insulating lining. It will be appreciated that a falling ceramic plate can cause substantial damage to articles in the kiln, particularly where the ceramic plate is attached to the lining of a roof of the kiln, and results in damage occurring to the lining.
More expensive furnace lining materials are known such as that sold under the name “Saffil”. These do not contain silica but are about 90% alumina based fibrous insulation. Another alternative is a glass based fibre such as “Superwool”.
As these do not contain silica, they are not subject to health and safety legislation controlling the use of silica based materials. Saffil is a more expensive furnace lining material than silica based materials and Superwool, and thus tends only to be used in environments where higher temperatures are experienced. Hence for economy's sake, the furnace lining has to be designed with the temperature to which the furnace is to be heated in mind, and once designed there is, conventionally, little scope for improving the thermal resistance of the lining.
In some circumstances it is desirable to have a protective element at the cold face between the furnace wall and the furnace lining.
According to a first aspect of the invention we provide a lining for a furnace the lining having insulating material attached to an inside wall of the furnace, the insulating material in use having a hot face which faces inwardly of the furnace and a cold face at or adjacent the furnace wall, characterised in that a protective element is provided at least partially to cover the hot and/or the cold face, the protective element being secured relative to the face by a securing means which co-operates with a member which is embedded in the insulating material.
Thus particularly but not exclusively where the protective element is secured relative to the hot face of the insulating material the invention may provide the advantage of a conventional furnace lining which comprises a protective ceramic plate or plates attached to the hot face of the insulating material, but the manner by which the ceramic plate is attached is more secure than a simple cement attachment.
It is envisaged that a ceramic plate type protective element may be attached by both adhesive cement and the securing means/embedded member so that in the event that the cement fails, the co-operation between the securing means/embedded member will prevent the protective element becoming detached from the face of the insulating material, and vice versa.
Alternatively, the advantages of non-silica containing insulating materials may be provided by attaching one or more layers of non-silica containing material, e.g. in the form of a blanket, to a conventional silica-containing insulating material lining. Thus an existing lining may be adapted for use in higher temperature applications by applying a layer of Saffil or the like particularly to the hot face of the insulating material, as the higher grade, non-silica containing material is tolerant to higher surface temperatures.
Where the lining does not require upgrading but it is desired to provide a protective element to isolate the silica containing materials, a layer of Superwool or the like may be attached.
Where it is desired to do so, a layer or layers of conventional silica-containing lining materials may be added to the hot face of the insulating material of an existing lining structure, to upgrade the lining, although some means to protect the silica-containing lining materials from becoming airborne may be necessary to comply with health and safety legislation.
In one embodiment the securing means comprises a headed fastener a shank of which co-operates with the embedded member. For example, most conveniently the shank of the headed fastener has provided thereon, a screw thread, e.g. a male screw thread, and the embedded member includes a corresponding opposite screw thread, e.g. female threaded opening, with which the shank is in use engaged. Thus the fastener may be unscrewed for maintenance of the lining as and when required. However it is envisaged that the shank of the headed fastener may otherwise co-operate with the embedded member to attach the protective element at the respective face.
The shank of the threaded fastener may pass through a passage of the protective element into co-operation with the embedded member. For example, the passage may comprise a pre-formed opening through the protective element or a cut-out at a side of the protective element as desired.
Of course, in the construction of the first embodiment of the invention where the protective element is provided at the hot face, the headed fastener will be subjected to the heat within the furnace and so preferably the fastener is made at least substantially, and preferably totally, of a ceramic material. In low temperature environments though or at the cold face, the fastener could be made of, for example, nickel chrome or another suitable metal.
In another embodiment, the embedded member comprises an integral shank or is adapted to have a shank secured thereto, and the securing means is engageable with the shank to secure the protective element to the respective face.
Either the securing means or the shank may pass through the protective element for securing to the shank or the securing means respectively.
In each case, whether the protective element is secured to the hot or the cold face, because the securing means co-operates with the embedded member, there is no path for the conduction of heat from the hot to the cold face and hence to the inside furnace wall, via the securing means.
The protective element is preferably as light as possible and may conveniently be of plate-like configuration, made at least substantially and preferably totally, of a ceramic material. However, the protective element could comprise a blanket of silica free insulation such as Superwool or a high-temperature resistant textile material, and/or a higher temperature resistant high alumina insulation than other insulating material of the lining.
However, the protective element could comprise additional layers of the same insulating material as that from which the remainder of the lining is made.
Whether the protective element is provided at the hot and/or cold face a furnace lining typically includes a plurality of individual blocks or modules of insulating material
F. C. S. Dixon Limited
Friedman Carl D.
Horton Yvonne M.
MacMillan Sobanski & Todd LLC
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