Innovation and Technology


Construction of Float Glass Furnace

The quality of masonry in the float glass melting furnace directly affects the furnace’s service life and production operations. In recent years, the lifespan of float glass melting furnaces has been increasing, with some reaching over 8 years. Therefore, providing strong guarantees in terms of refractory brick materials, furnace construction, kiln roasting, and normal production operations is crucial. When constructing the furnace, corresponding refractory mortar should be used for different refractory brick materials, except for the dry-laid parts, and expansion joints of the masonry should be left according to the expansion coefficient of the refractory bricks.

Requirements for Float Glass Melting Furnace Masonry

The masonry of the float glass melting furnace is based on the vertical centerline of the furnace, the centerline of the No. 1 small furnace, and the benchmark elevation. The masonry requirements for various parts are briefly described as follows.

1. Flue

1.1 The construction of the flue in the float glass melting furnace is generally carried out in the first stage of furnace masonry. However, some manufacturers, in order to expedite ignition, complete the construction of the furnace body first and then proceed with the flue construction. In this case, attention should be paid to construction protection.

1.2 The construction of the flue is based on the centerline of the No. 1 small furnace and the centerline of the furnace. For convenience, at the junctions of the main flue and branch flues, as well as at the bends of the branch flues, heat-resistant concrete can be used for casting.

1.3 At the junctions where different flues meet, the joints should be constructed with straight seams, and the walls should be staggered. Pay attention to ensuring that the length of the bricks at the joint heads is not less than 120mm to prevent detachment.

1.4 Expansion joints of the flue wall should be left in sections, generally every 2 meters with an 8mm gap. The expansion joints should be constructed with staggered seams, and clay bricks should be used for the exterior of the expansion joints, not insulating bricks.

1.5 The outermost layer of the flue wall is made of red bricks. Due to the different thicknesses of red bricks and standard refractory bricks, mismatched construction is inevitable. Therefore, it is required to bite half a brick into the wall every 7-8 layers of red bricks towards the inside of the wall. The height of the biting can be adjusted by processing the thickness of insulating bricks.

2. Heat Storage Chamber

2.1 The wall thickness of the heat storage chamber is generally 578mm. The side walls and end walls are composed of one and a half refractory bricks and one insulating brick. Expansion joints can be left in sections during construction. Partition walls are all made of refractory bricks (two and a half bricks), and expansion joints must be left at both ends of the partition wall.

2.2 The furnace bar notch is a critical part of the heat storage chamber, and safety must be ensured. The notch should be constructed by pulling straight lines, and each furnace bar notch must not be inclined. Leveling bricks should be used to level the surface of the furnace bar notch bricks, ensuring a smooth surface for the stacking of grid bricks. Leveling work for the furnace bar notch of the float glass melting furnace takes a long time and must be finely constructed. The most common method currently is to process the lower surface of the leveling brick appropriately before masonry. After completion, according to the requirements of the furnace bar notch bricks, mark the elevation line and number each brick. Remove the leveling brick, cut it according to the marked line, then re-masonry with mud according to the numbered position, pull the line according to the elevation, and use an angle grinder to correct the height.

2.3 After the back side wall of the heat storage chamber is built to the height of the small furnace bottom plate, it should be paused for the construction of the breast wall and small furnace. The construction of the back side wall can only continue after the construction of the small furnace’s inclined notch and rear flat notch is completed.

2.4 The stacking of grid bricks requires vertical and horizontal alignment. After production inspection, grid bricks should be packaged and labeled with the tolerance range on the packaging box. The same tolerance range of grid bricks should be used for stacking on the same layer.

3. Pool Wall

  • The bricks of the float glass melting furnace pool wall are generally whole bricks in the vertical direction. When constructing, they should be placed according to the numbered codes on the drawings. To ensure the horizontal and vertical alignment of the pool wall bricks, a small amount of zirconium-based ramming material can be placed under the pool wall for adjustment if needed.

4. Breast Wall

4.1 Adjust the breast wall support plates to be on the same horizontal plane. Fix the jaw iron, determine the position of the hook bricks according to the centerline of the furnace, and snap a line above the pool wall bricks. At this time, each small furnace centerline should also be drawn, and then mark each brick’s position according to the drawing.

4.2 When the construction of the small furnace flat notch is completed, the notch form should not be removed. It should be retained until the construction of the breast wall in the clarified section is completed. It can only be removed after securing the ends tightly to avoid sinking.

4.3 The electrically fused zirconia corundum bricks in the breast wall area are all dry-laid. It is important to note that when constructing the hook bricks, wooden wedges must be inserted between the pool wall bricks and the hook bricks, ensuring the hook bricks are horizontal.

4.4 Due to the large and heavy bricks in the breast wall area, some even reaching several hundred kilograms, special attention should be paid to safety during construction.

5. Large Notch

5.1 The float glass melting furnace adopts a structure of steel notches and chamotte. The steel notches must be accurately and stably placed. Along the longitudinal direction of the furnace on the same side, steel wires are drawn, adjusting the inclined surface of the steel notches to be on the same plane. Thin steel plates can be used if necessary, but it must ensure sufficient contact area and stability.

5.2 Supporting notches. Since the thickness of the large notch bricks in the float glass melting furnace is generally 400-500mm, and the mass is large, it is required that the notch supports have sufficient strength and ensure the overall stability of the notches. After the notches are properly supported, measurements and adjustments should be repeatedly made using a level to ensure they are at the same height.

5.3 Before starting to build the notches, 2-3 rings of notch bricks should be dry-stacked for each section of the notches. This allows for a clear understanding of the size of the mud joints during construction.

5.4 The locking bricks of the large notches should be 100-150mm higher than the top of the notches. Locking bricks for the same section of the large notches should be hammered simultaneously to ensure even force on the entire notch.

5.5 The suitability of siliceous mud for construction is not very good. Since the large notch bricks are large, to quickly and evenly apply the mud to the brick surface, it is required that the siliceous mud must have sufficient mixing time. From mixing to use, a maturation time of 4 hours is needed. Therefore, the mud pool should be slightly larger, and the materials should be prepared in advance.

5.6 The joint at the top of the notch bricks must be strictly controlled during construction and kiln roasting. During thermal insulation, fine construction should be done using sealing materials. The joint structure at the top of the notch adopts a stepped design, and after kiln roasting, it should be sealed with silica-based heat-resistant material.

5.7 The large notches of the float glass melting furnace are relatively long. When tightening the wire, multiple adjustments with a small degree of tightening are required. To ensure the synchronous lifting of the large notches, it is best to set three measuring points along the longitudinal direction of the furnace on each section of the large notches. Use a level to observe, measure, and adjust while tightening the wire. This ensures that the entire large notch rises by a similar amount. Generally, when the large notch rises by 10mm, the large notch will detach from the notch supports. At this time, the wire can be tightened, and the notch supports can be removed, starting the disassembly of the notch form.

The construction of the pool bottom, small furnace inclined notch, and other parts is similar to that of other industrial kilns. However, it should be emphasized that the refractory materials used in various parts of the small furnace currently almost all adopt electrically fused AZS bricks, and the shapes of the bricks are complex, making installation difficult. To ensure construction quality, it is required that these refractory bricks must be finely ground and processed. They should be pre-arranged, numbered, and labeled on the drawing to reduce the difficulty of construction. The installation of L-shaped hanging walls, according to the current situation, whether imported or domestically produced hanging walls, is constructed and installed by the supplier, and design and technical personnel provide on-site guidance.

Control of Construction Quality in Float Glass Melting Furnace

1. Material Entry and Steel Structure Fabrication

1.1 All materials or finished products entering the construction site of the melting furnace, such as refractory materials, furnace building materials, steel, and steel components, should comply with the current national product standards and design requirements.

1.2 All steel components, processed parts, and fabricated parts entering the construction site should meet the design requirements and relevant specifications. The installation and supervisory units should inspect and accept them. If necessary, personnel can be stationed at the factory for supervision.

1.3 Quality certification documents and test reports should be provided for refractory materials, furnace building materials, and steel used at the construction site. Amorphous refractory materials for furnace building should also come with usage instructions. Materials with quality disputes should undergo re-inspection. Only qualified materials can be used, and unqualified materials should be removed from the site.

1.4 Steel components and refractory materials should be neatly stacked to prevent deformation and scattered stacking. Magnesia bricks, prone to moisture-induced deterioration, must be kept dry. Amorphous refractory materials and binders must be stored separately and should not be confused. Refractory materials should be protected from rain. During transportation and unloading, handling should be gentle to avoid collisions.

1.5 Measurement instruments and tools used in the fabrication, assembly, and quality inspection of steel structures should be regularly calibrated, complying with the relevant regulations of the national metrology department. In the fabrication and processing processes, procedural inspections should be carried out, allowing production to proceed only after passing the inspection. The fabrication, processing, assembly, splicing, and installation of steel structures should comply with design requirements and current national standards and specifications.

1.6 Finished steel structural components should be promptly rust-treated according to design requirements and coated with anti-rust paint or liquid to prevent corrosion during transportation and use. Components with threads should also be fitted with protective covers to prevent damage and ensure usability. During transportation and storage, steel structural components should be reasonably stacked to prevent deformation that may affect installation.

1.7 Steel structural components should be produced according to the drawings, with smooth and even edges, free from burrs or irregularities. Round holes must be drilled, and on-site cutting into holes is not allowed. All welding quality should meet the requirements of the current national standards, and the welding quality should comply with the provisions of the “Code for Acceptance of Construction Quality of Steel Structures” (GB50205-2001).

2. Main Beams, Secondary Beams, and Doghouse Beams Installation

2.1 The longitudinal centerline of the furnace, the centerline of furnace No. 1, and design elevations delivered by the civil engineering unit should be rechecked and permanently positioned first. This is a critical dimensional positioning for furnace construction, and efforts should be made to accurately position it, with a measurement error controlled within 1mm.

2.2 Carefully check the elevation of the supporting concrete column for the furnace. It should be controlled within the negative tolerance range of the design elevation, without positive tolerance. Generally, it should be controlled within -3~-4mm. If it is positive tolerance, it must be rectified. The secondary pouring of the column head plate must be compact, with no hollow shell phenomenon allowed.

2.3 The fabrication of the main beams must meet the design requirements. After hoisting into place, check the top elevation of the main beams, controlling it within the negative tolerance range of the design elevation, generally within -3mm. If controlled according to the design elevation, the allowable errors accumulated from the main beams above, the secondary beams above, the doghouse beams, and the bricks of the doghouse and pool bottom can lead to the top elevation of the pool wall bricks exceeding the design elevation range. This results in too small a gap between the pool wall bricks and hook bricks, posing risks and affecting production due to the glass liquid level exceeding the standard.

2.4 When measuring the top elevation of the main beams, special attention should be paid. It is necessary to measure the highest point on the top surface of the main beams, which can be found using a level ruler to identify the highest point. As shown in Figure 6-1, the secondary beams are laid on the highest point of the main beams.

In actual construction, many construction units have not paid attention to this point. Often, what is measured is the central position of the main beams②. Although the elevation of the main beams is appropriate, after installing the secondary beams, it is discovered that the elevation of the secondary beams is excessively high. The reason is that during the fabrication of the main beams, welding deformations can cause the top surface of the main beams to tilt or twist. As a result, the center position ② is not the highest point of the top surface of the main beams. The same applies to the installation of secondary beams; the highest point of the secondary beams must be measured, or else the design elevation of the doghouse beams will rise. Therefore, it is essential to require the main and secondary beams to be fabricated flat, straight, and non-twisted.

2.5 After the installation of the secondary beams, the elevation should be controlled within the negative tolerance range of the design elevation, generally within -2~-3mm. In places where it exceeds the elevation, a clamp can be used to tighten the secondary beams against the main beams or temporarily spot-weld them. Temporary welding points should be removed before kiln roasting.

2.6 Doghouse beams should be placed flat and straight on the secondary beams. The claws of the insulation support plate should be spot-welded underneath the doghouse beams. First, turn the doghouse beams upside down, weld the claws, and then flip them back for installation to prevent welding deformations. Some construction units do not use spot welding but weld directly, resulting in deformation of the doghouse beams. This is an incorrect practice that must be avoided. Some construction units first install the doghouse beams, then lay the doghouse bricks, and later weld the claws. This approach is also incorrect, as it is cumbersome and provides no room for adjustment after welding deformations. Graphite grease should be applied between the doghouse beams and the secondary beams, as well as between the secondary beams and the main beams, facilitating expansion displacement of the pool bottom.

2.7 After the installation of the main and secondary beams and doghouse beams, inspection and acceptance should be conducted. Construction of the next process should proceed only after passing the inspection.

3. Installation of Melting Furnace Columns, Chest Wall Support Plates, and Deflector Beams

3.1 Columns entering the site of the melting section should comply with relevant steel structure fabrication standards and design requirements. The overall height bending radius of the column should not exceed 5mm, the flange inclination should not exceed 2mm, and the flatness should not exceed 3mm. It should not be twisted or deformed.

3.2 Columns should be hoisted into place according to the positioning dimensions. The positioning error should not exceed 2mm. Columns should be installed vertically, with an inclination not exceeding 1mm. After adjustment, they should be temporarily fixed. Considering that columns bear heavy loads during the installation of chest wall support plates, deflector beams, and chest wall masonry, to prevent the columns from tilting inward, during the adjustment of column verticality, based on installation experience, the columns can be tilted outward by about 4mm to ensure they remain vertical after installing heavy loads. Another approach is to weld adjustable flange screws on the temporary fixed angle iron, allowing for real-time adjustment of the columns to keep them vertical. Some construction units, after adjusting the verticality of the columns during installation, only provide temporary fixation. After installing chest wall support plates and deflector beams, if the columns are slightly inclined without causing concern, and if verticality is not adjusted in a timely manner, it may be discovered after the masonry of the chest wall is completed that the columns and chest wall are inclined inward. At this point, it is impossible to adjust, directly affecting the quality of the subsequent processes, such as the masonry of border bricks and large bricks. This is something that must be paid attention to during column installation.

3.3 After the installation and adjustment of columns, beams, top wire plates, top wires, chest wall support plates, deflector beams, and platform supports can be installed.

3.4 Chest wall support plates should be made flat and straight, without bending or twisting. During installation, the top surface elevation of the support plates should be controlled within the positive tolerance range of the design elevation, generally ideal at +2mm of the design elevation. The expansion joints between support plates should meet requirements, generally 20mm, with consistent heights between adjacent support plates. The spacing with columns should comply with design requirements, typically 90mm.

3.5 The fabrication of deflector beams should meet design requirements. The contact surface with border bricks should be flat, and if possible, the manufacturing unit should plane it. During installation, the elevation, span, and angle of the deflector beams should all meet design requirements. Slight adjustments can be made based on the masonry situation of the chest wall to ensure the border bricks are well-aligned. Deflector beams must be closely supported by columns, and if there are gaps, they must be shimmed with thin steel plates of varying thicknesses. The use of other materials for shimming is not allowed to prevent the deflector beams from loosening during the masonry of large bricks.

3.6 Whether the border bricks fit with the deflector beams and are straight along the chest wall when masonry is directly reflected in the quality of steel structure fabrication and installation, and also directly reflects the quality of chest wall masonry. The fabrication and installation errors of column deflector beams, chest wall support plates, and chest wall brick materials, masonry errors will all prevent the border bricks from fitting closely with the deflector beams or being straight along the inner edge of the chest wall. Simply by observing the masonry of border bricks, the quality of the preceding processes in installation and masonry can be known. There are many examples of such instances in construction. For example, during the masonry of border bricks in a certain melting furnace, it was found that the border bricks protruded 3cm from the chest wall. After inspection, it was discovered that the spacing between the chest walls on both sides did not comply with design requirements, but it was impossible to rectify. It was necessary to grind off 3cm of the thickness of the border bricks, otherwise, it would affect the construction quality of large bricks. When pre-arranging border bricks in a certain melting furnace, it was found that there was a gap between the border bricks and the plane of the deflector beam. After inspection, it was found that the installation angle of the deflector beam did not comply with design requirements. The deflector beam must be reinstalled and adjusted.

4. Construction of Dog Bricks, Pool Bottom Bricks, and Pool Wall Bricks

4.1 The construction of dog bricks should be flat and straight, with the elevation controlled within the negative range of the design elevation, generally -3 to -2mm. Sufficient expansion joints should be left between dog bricks, and any mud or debris within the expansion joints should be thoroughly cleaned.

4.2 Before the construction of pool bottom bricks, relevant equipment and tools should be prepared. The joints of the pool bottom bricks should be positioned at the center of the dog bricks. On the dog bricks, mark the positioning dimensions, using the vertical centerline of the melting furnace and the centerline of furnace 1# as a reference. Outline the positioning control lines for each row or several rows of bricks. Build according to the control lines, leaving sufficient expansion joints. Use suction cups as much as possible during construction. Clean the dust promptly at the expansion joints, seal them with adhesive tape to prevent debris from entering, and handle the installation with care to avoid manual damage to the edges and corners of the bricks. After construction, promptly lay colored strips and plywood. The top elevation of the pool bottom bricks in the middle of the kiln is not controlled. Only the elevation of the pool wall brick positions is controlled, generally within the range of the design elevation and ±1mm. High spots above the design elevation should be ground flat.

4.3 Before pool wall bricks enter the site, they should be pre-numbered by the manufacturer, and a numbering diagram should be provided. During construction, follow the numbering for orderly and straight masonry, ensuring even joints, and adjusting triangular joints as needed. Positioning dimensions should be controlled within 2mm.

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