GB2032075A - Method of repairing furnace roofs during heat-up - Google Patents

Abstract

A method for preventing the dropping of individual bricks (20') from a sprung arch roof (11) employed in a continuous tank-type glass melting furnace, the dropping of the bricks normally occurring during heat- up of the furnace. The slightly tapered bricks (20) employed in constructing the roof are oriented with their long axis in the vertical direction and, as heating occurs and the structure differentially expands and the bricks dry out, some become sufficiently loose to drop from the roof into the tank of the furnace. In visually observing the interior surface of the roof during heat-up, it can be seen which bricks are settling and likely to drop therefrom. These bricks are pulled up through the roof from above by a suction cup and mortar is placed around the bricks. The bricks are then dropped back into place with the mortar holding the bricks until they become wedged firmly in place as the temperature of the roof increases. <IMAGE>

Description

SPECIFICATION Method of repairing furnace roofs during heatup This invention relates to spring arch roofs or crowns of continuous glass melting furnaces, and more particularly to the problems resulting from the non-uniform temperatures encountered during heat up of the furnace which cause portions of the overall structure, as well as the individual bricks employed in constructing the arched refractory roofs, to expand at different times.

Conventionally, sprung arch roofs as employed in continuous glass melting furnaces spring from skews running the entire length of the furnace, the skews being set on heel plates firmly attached to the buckstays forming part of the furnace superstructure. Conventionally, the roof is built up of individual, tapered, like-sized refractory bricks which may be set in an overlapping pattern like the checker pattern of a conventional brick wall.

An example of such a roof is shown in United States Patent No. 2,236,920 issued on April 1, 1941. The construction of such roof may be accomplished by simply dipping the individual bricks in a siliceous mortar and setting them in place on a form supported by scaffolding. When the form on which the roof has been laid during construction is removed, the slight elastic yielding of the buckstays and tie rods, together with the bedding in of the contacting surfaces of adjacent bricks against each other, allows the crown of the roof to drop slightly and small gaps to open between the lower ends of the bricks. Thereafter, when the furnace is heated up, the bricks expand and raise the crown to its original position.

Newly constructed roofs as above-described are often very damp, and they are slowly dried out over a period of time (10 to 12 days), by temporary burners such as salamanders placed at convenient locations about the furnace. During this time, the temperature throughout the furnace and the roof will not be uniform. It is the usual practice in glass melting furnaces to construct the arches of silica bricks, which exhibit their maximum thermal expansion at low temperatures such as those encountered during the drying-out period. Accordingly, it may be found that the bricks expand at different times or the crown may warp during the drying-out period by rising unequally in one part or another with respect to the plane of symmetry of the tank.Consequently, as heating occurs and the bricks dry out, some may become sufficiently loose to drop from the roof arches into the interior of the furnace.

In the past bricks dropping out of the roof have been replaced by driving larger, wedge-shaped bricks into the openings after the original bricks have fallen, with the new bricks being initially held in place due to their larger size, and then by their expansion as heat up continues. This procedure is not entirely satisfactory in that it requires the insertion of a cold, larger size brick into an arch of the heated bricks causing the pressure on the bricks to be increased as the heat-up continues since the ends of the arches are held in a fixed position by the skew backs. As a result, the bricks may spall or be crushed and a section of the roof may fall. Another disadvantage is that it is necessary to retrive the fallen bricks from the tank so that they will not contaminate the glass to be produced therein.

The above-mentioned disadvantages are overcome by the procedure of this invention which comprises the steps of visually inspecting the interior surface of the arches of the roof to see which bricks are settling and protruding from the interior surface, grasping the extending bricks from above by a suction cup; pulling the bricks back up the roof, coating the bricks with mortar and dropping them back into their place in the roof; the mortar holding the bricks until they become firmly wedged in place as the temperature of the roof increases.

An object of this invention is to provide a method for preventing the dropping of bricks from a sprung arch roof of a glass melting furnace during heat-up.

In the accompanying drawings: Fig. 1 is a transverse fragmentary perspective view, partly in section, showing a portion of the interior and illustrating bricks settling in the roof; Fig. 2 is an enlarged, fragmentary, sectional view of one of the arches of the roof showing a brick settled from its normal position just prior to being removed from the arch; and Fig. 3 is a view similar to Fig. 2 but showing a removed brick coated with mortar just prior to its being reset in the arch.

According to the present invention, there is provided a method of preventing individual bricks from dropping from a sprung arch roof of a furnace during initial heat-up thereof, characterized by the steps of visually observing the interior surface of said sprung arch roof and detecting any individual brick which changes position and projects below said surface, grasping said individual brick projecting from the top and removing said brick from said roof, applying mortar to the sides of said removed brick, and reinserting said mortar coated brick in said roof.

As illustrated in Fig. 1, only the upper portion of a glass melting furnace 10 is shown as the invention relates specifically to a sprung arch roof or crown 11 therefor. As therein illustrated, the melting furnace 10 includes a chamber 12 bounded by jamb walls 1 3 and 1 4, buttressed by buckstays 1 5 connected together by tie rods 1 6 for stabilizing the furnace structure.

Located on the top of each of the jamb walls 13 and 14 are skew blocks 1 7 and 18 which run the entire length of the chamber 12 and are suitably supported as upon longitudinally extending Ibeams 19, for example, which are rigidly secuted to the buckstays 1 5.

Springing from the skew blocks 1 7 and 1 8 is the sprung arch roof 11 which is normally built-up of a plurality of individual refractory bricks 20 measuring 1 8 inches (45.72 cm) in length, 9 inches (22.86 cm) in width and tapering from a thickness of 3 inches (7.62 cm) across the top to 2-7/8 inches (6.30 cm) across the bottom. As is common practice, the brick s 20 are layed in overlapping courses 21 with their long axes oriented in a vertical direction with a heat setting mortar 22, one that sets at about 20000F (1 0930C), (see Fig.

2) between their joints. Accordingly, the roof 11 as a whole is composed of a series of these courses 21 interlocked together and becomes a monolithic structure after the mortar sets.

With the sprung roof 11 formed as just described, it will be obvious that as the furnace is initially heated and the drying out and heating up process proceeds, the individual bricks 20 in the roof will expand as they absorb heat, and that since they are set with a morar that does not hardened until it reaches a relatively high temperature, the bricks will be free to move relative to each other.

As previously indicated, the furnace is initially heated by temporary burners placed at various locations about the furnace, and thus the temperature throughout the furnace may not be uniform. Thus, the individual bricks 20 will absorb heat at different rates and expand accordingly. This differential absorption of heat by the bricks will loosen some to the point that they settle and project through the interior surface of the roof 11.

In accordance with the invention, the interior surface of the roof 11 is kept under visual surveillance and when an individual brick 20' is observed to settle and project into the chamber 12, the top of the brick 20' is grasped by a suction device 23 (see Figs. 2 and 3) connected to a source of vacuum pressure (not shown) by a hose 24. As indicated in Fig. 3, the brick 20' is lifted out of the roof 11, coated with additional mortar such as the heat setting mortar 22, and then pushed back into place in the roof. It has been found that this additional mortar will hold the brick until it becomes wedged firmly in place as the heat-up continues and the temperature of the roof increases.

Claims (4)

1. A method of preventing individual bricks from dropping from a sprung arch roof of a furnace during initial heat-up thereof, characterized by the steps of visually observing the interior surface of said sprung arch roof and detecting any individual brick which changes position and projects below said surface, grasping said individual brick projecting from the top and removing said brick from said roof, applying mortar to the sides of said removed brick, and reinserting said mortar coated brick in said roof.

2. A method of preventing individual bricks from dropping from a sprung arch roof as claimed in Claim 1, characterized in that the top of said brick is grasped by a vacuum device.

3. A method of preventing individual bricks from dropping from a sprung arch roof as claimed in Claim 1 or Claim 2, characterized in that said mortar is a heat setting mortar which does not set until it reaches a temperature of about 20000F (1 0930C).

4. A method of preventing individual bricks from dropping from a sprung arch roof of a furnace during initial heat-up substantially as described in the specification.