1. The retention of expansion joints in refractory castables
The thermal expansion of the refractory castable is mainly related to the aggregate of the aggregate, which is roughly the same as the thermal expansion of the refractory brickwork of the same material.
The furnace body built with refractory bricks, because the refractory mud in a large number of brick joints can be compressed, the expansion of the masonry after heating, so the total elongation is small, the refractory castable prefabricated parts or the on-site pouring furnace In the inner lining, the total elongation of the furnace body after thermal expansion is large. If there is no proper expansion joint, the lining will be bent, squeezed or deformed at the steel structure at both ends of the furnace body.
1. Expansion value of refractory castable
The setting of the integral cast refractory lining expansion joint shall be stipulated by the design. When the design does not specify the value of the expansion joint, for clay or high-aluminum refractory castables, the average value of the lining expansion joint per meter length can be as follows:
1 clay refractory castable is 4~6mm;
2 high alumina cement refractory castable is 6~8mm;
3 phosphate refractory castables are 6~8mm;
4 water glass refractory castable is 4~6mm;
5 Portland cement refractory castable is 5~8mm.
2. Expansion joint filler
The filler and thickness of the refractory castable expansion joint shall be designed according to the design. When the design is not specified, it shall be filled with asbestos board or plywood, and its thickness is 4~5mm.
3. The form of refractory castable expansion joint
The form of the expansion joint of the refractory castable is basically divided into two types: a through seam and a non-through seam.
4. Expansion joint expansion
The retention of the refractory castable expansion joint is mainly to select the spacing, width and form of the expansion joint. The pre-formed furnace body and the cast-in-place furnace have different distances between the expansion joints.
1The furnace body assembled by prefabricated components, if assembled with prefabricated parts, if the furnace body is short, there is no need to leave another expansion joint between the prefabricated parts, only need to leave a proper gap at both ends of the furnace body; if the furnace body is long, According to the temperature of each section of the furnace body, an expansion joint is left every 5~10m along the length of the furnace body. The joint is filled with asbestos rope impregnated with clay mud to prevent the smoke from escaping in the furnace at low and medium temperatures. Get angry.
2 On-site casting of the furnace body. The cast-in-place refractory castable furnace body is provided with the spacing and width of the expansion joints.
3 fixing of the filler. The material of the expansion joint in the refractory castable should be fixed in place before pouring or carefully filled in the pouring. When the block is poured, the refractory castable should be divided into several pieces according to the expansion joint and separated from the expansion joint by the template. Pouring, embedded in the joint filler after initial setting
a: δ=3~4mm
b: δ = 5mm
4 to prevent displacement. In order to prevent the displacement of the expansion joint filler or the local refractory castable adhesion, the filler layer should be cut accurately and tightly laid. If necessary, nails can be used to nail the castable to stabilize the filler layer.
5 isolation measures. When the packing layer is in the cold state in the construction environment, it is separated and contacted in the hot state, that is, when it becomes the slip surface, it is preferable to increase the separation layer to prevent the displacement of the packing, prevent the slurry from sticking or block the expansion gap.
5. Notes
Pipes and components that pass through the refractory castable shall be wrapped with asbestos rope and asbestos board.
For dense small tube bundles, you can pack 350 linoleum paper or brush asphalt (brush thickness is 2mm).
Second, the quality requirements of the expansion joints 1. Quality requirements
(1) The position, construction and filling of the expansion joint must meet the design requirements.
(2) There shall be no debris such as broken bricks or mud in the expansion joint. To this end, leave the expansion joints during the masonry, and fill them with foam, cardboard or wood chips of appropriate size to prevent falling into the debris. The filler in the seam must be tightly packed and must not be loose.
(3) The expansion joint should take anti-tempering measures.
2. Filler
The filler in the expansion joint must conform to the number of layers specified in the design, the number of layers, and plugged as required.
3. Allowable error of expansion joint
(1) The allowable error of the vertical expansion of the vertical expansion joint is not more than 2mm per meter height, and the full height is not more than 15mm.
(2) The horizontal tolerance of the horizontal expansion joint is not more than 2.5mm per meter and the total length is not more than 15mm.
(3) The wrong teeth of the expansion joint of the power station boiler are allowed to be 3~4mm.
(4) Allowable error of the width of the expansion joint
(5) All kinds of refractory castables cast on site shall be provided with expansion joints according to the design drawings. The width error shall be +3mm and shall not be less than the specified width.
The castable expansion joint is also related to the temperature of each small section when it is left behind. For example, in the high temperature section (greater than 600 °C), the slit width should be controlled to 3~4 mm according to the spacing of the expansion joints; Less than 400 ° C), the equipment shell does not need to use the thermal insulation layer directly to the part of the castable, insert 2 mm thick cardboard or plastic film every 1.5 m to meet the expansion space requirements.
Generally, the shrinkage and expansion of the refractory castable appear in the first heating process. At 50~200 °C and 900~1000 °C, there will be two volume shrinkage. Under other temperature heating conditions, the refractory castable will expand. After the first oven or after heating, the refractory castable generally does not shrink again.
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