The masonry construction of glass melting furnaces must be executed strictly in accordance with the design specifications. The materials used for masonry work must be selected in compliance with the design requirements and the provisions of current material standards. Masonry construction for a glass melting furnace may only commence after the furnace foundation, the structural steel framework, and associated equipment installations have undergone inspection, been deemed compliant, and a formal "Process Handover Certificate" has been signed.
The Process Handover Certificate shall include the following details: measurement records for the furnace centerline and control elevations; acceptance records for concealed works; verification records for the primary dimensions and positioning of the installed steel structure; and inspection records regarding the quality of anchors, welded components, and similar items.
Within the glass melting furnace, the following sections shall be constructed using "dry masonry" (without mortar): the furnace bottom, furnace walls, lower gap bricks, the superstructure constructed from fused-cast refractories, the checker bricks within the regenerators, and any other sections specifically designated for dry masonry in the design. All other sections shall be constructed using "wet masonry" (with mortar).
Unless the design specifically mandates the inclusion of expansion joints or filler materials, bricks within dry-masonry sections must be placed in tight mutual contact, without the use of any intervening filler materials. Depending on the specific requirements of the construction phase, refractory bricks intended for dry-masonry sections shall undergo selection, trimming/processing, and pre-assembly (dry-fitting) procedures.
(1) Masonry Construction for the Melting and Cooling Zones
① The masonry construction of the furnace bottom in both the melting and cooling zones shall proceed outward from the respective zone's centerline toward the sides. During the construction of the furnace bottom in these zones, the positioning of the flat steel reinforcement bars must be adjusted simultaneously. Regarding the brick joints in the furnace bottom masonry-with the exception of specific areas explicitly marked in the design-the joints must be aligned in both the longitudinal and transverse directions; expansion joints shall be provided at these joint locations, and adhesive tape or similar measures must be applied to prevent the ingress of debris or foreign matter. The upper surface of the furnace bottom masonry, specifically in the areas where the furnace walls are to be erected, must be measured and leveled. When constructing the furnace walls, the outer edge of the furnace bottom bricks must not be recessed inward relative to the outer edge of the furnace wall bricks. For furnace bottoms incorporating an insulation layer, the ramming layer (monolithic refractory layer) must be thoroughly and carefully compacted prior to the installation of the paving bricks. In instances where no ramming layer or paving brick layer is specified above the bottom bricks, appropriate measures must be implemented to prevent the bottom bricks from floating (lifting) during operation. For the furnace bottom bricks and paving bricks within both the melting and cooling zones, expansion joints must be provided in strict accordance with design requirements, and measures must be taken to prevent the ingress of debris or foreign matter into these joints.
② For the masonry of the tank walls, high-density bricks and high-quality fused-cast bricks shall be utilized in high-temperature, erosion-prone zones within the melting section, as well as at the charging port, drain hole, and the inlet of the feeder channel. At the corners of the tank walls, the bricks shall not be laid in an interlocking pattern; unless otherwise specified in the design, a straight joint shall be formed along the longer tank wall face at these locations.
③ During the masonry of the breastwalls and the furnace crown, temporary bracing measures shall be applied to the buckstays. Concurrently with the laying of the crown skewbacks, the steel skewback supports shall be adjusted; under no circumstances shall brick chips or refractory mortar be inserted to shim irregularities between the skewbacks and the steel supports, or between the steel supports and the buckstays. Expansion joints shall be provided at the sectional interfaces between the furnace crowns of the melting section and the cooling section. In instances where the furnace crown incorporates a supporting arch, the section extending from the skewback of the supporting arch up to the leveling brick at the crown apex-specifically at the sectional interface-shall be laid with a straight joint, omitting any expansion joints. For every five courses of crown bricks laid, a template check shall be performed. At the terminal ends of each crown section in both the melting and cooling sections, the laying of crown bricks with a width of less than 150 mm is prohibited. The bottom faces of the hanger bricks shall be laid using the wet method, while their top faces shall be laid flush. A clearance of 5 mm shall be maintained between the inner curved face of the hanger bricks and the supporting plate. The expansion joints between adjacent hanger bricks shall be sealed with adhesive tape to prevent the ingress of debris. The gap between the upper filler bricks and the furnace crown shall be filled with a thick refractory mortar compatible with the surrounding masonry. During the masonry of the hanger bricks and breastwalls, measures shall be implemented to prevent them from tilting inward toward the furnace interior. The horizontal distance from the crown skewbacks to the furnace centerline, as well as the vertical elevation of the skewbacks, must strictly conform to the design specifications. During the masonry of the melting section crown, the keystone bricks for all supporting arches on a given side-specifically those within the same horizontal course-shall be driven into place simultaneously. From the moment the key bricks are driven in until the arch centering is removed, temporary jacking measures must be implemented at the skewbacks of the first and last arch bricks within each supporting arch on the same side of the furnace. Once the arch masonry for the melting and cooling zones is complete, the nuts on the tie rods connecting opposing columns must be tightened gradually and uniformly to allow the furnace crown to rise incrementally. Markers used to monitor the rise and fall of the crown-specifically at the center and the flanks-must be installed in advance. The arch centering may only be removed after the furnace crown has fully disengaged from the centering structure and has been inspected to ensure there is no subsidence, deformation, or localized sagging. Upon the completion of all masonry work for the tank walls, tank bottom, and their superstructure, the inner surfaces of the masonry must be cleaned of debris using a steel brush, and it is recommended that a vacuum cleaner be used to remove the loosened debris.
The thermal insulation layer for the furnace crown should be applied only after the furnace drying process has been completed. Prior to applying the crown insulation, the crown surface must be cleaned, sealed, and any defects repaired. For insulated glass melting furnace crowns, no insulation material should be applied at the expansion joints or around the thermocouple blocks.
For the arch bricks in the melting and cooling zones-excluding their top and bottom faces-any surfaces that fail to meet the required dimensional precision must undergo machining. Similarly, the upper and lower gap bricks must be machined if they fail to meet the required precision. For breast wall bricks-excluding their inner and outer faces-any remaining faces that fail to meet the required precision must be machined, and the cast face must be oriented toward the furnace interior. For hanger bricks-excluding their inner and outer faces-any remaining faces that fail to meet the required precision must be machined. Regarding machining precision requirements: dimensional errors must not exceed ±0.5 mm, and flatness errors must not exceed 0.5 mm. For large-format clay bricks used in the melting zone, cooling zone, and throat, all faces-with the exception of the face in direct contact with the molten glass-must undergo machining. The machined faces of the bricks must be inspected using a straightedge and a square; the gap between the measuring tool and the brick surface must not exceed 1 mm, and dimensional errors must not exceed ±0.5 mm.
(2) Construction of Flues, Regenerators, and Ports
When the walls of flues and regenerators are constructed using bricks of two or more different materials, the inner and outer layers of bricks should be interlocked with one another approximately every 500 mm along the vertical direction. For the walls of glass melting furnaces, the verticality error per meter of height shall not exceed 2 mm, and the total verticality error over the entire height shall not exceed 5 mm. The checkerwork riders (support beams) in the regenerator must not be skewed; their spacing must conform to the design dimensions, with an allowable error not exceeding ±1 mm. The elevation error of the top surfaces of the riders shall not exceed ±1 mm. The top surfaces of all leveling bricks supporting the riders must lie on the same horizontal plane. The deviation between the actual centerline and the design centerline for the masonry of each port and regenerator unit shall not exceed 3 mm.
Regenerator arch bricks and port arch bricks-with the exception of their top and bottom faces-must be dressed (machined) if they fail to meet the required dimensional precision. For fused-cast bricks used in port side walls, the bricks-with the exception of their inner and outer faces-must be dressed if they fail to meet the required precision. For fused-cast bricks used in port bottoms, the bricks-with the exception of their top surfaces-must be dressed if they fail to meet the required precision. Regarding the aforementioned precision requirements for dressing, the dimensional error shall not exceed ±0.5 mm, and the flatness error shall not exceed 0.5 mm.
The verticality error of the regenerator checkerwork (grid structure) shall not exceed 5 mm, and the flatness error of the top surface of the checkerwork shall not exceed 5 mm. The checker openings in adjacent upper and lower layers must be vertically aligned. Horizontal observation ports and horizontal checker openings must be aligned with one another.
The allowable clearance between the regenerator walls and the edge bricks of the checkerwork shall be within the range of 0 to 5 mm.
The sectional expansion joints within the port arches must be constructed with beveled edges, while the expansion joints in the port walls shall be constructed as concealed joints. When constructing the skew arches of the ports, measures must be implemented to prevent slippage before the supporting steel framework is fully tightened.
(3) Forehearths
The dimensions of the forehearth, as well as its relative position with respect to the glass forming equipment, must strictly conform to the design specifications. During the masonry construction of the forehearth channel, the "casting face" (mold-side face) of the bricks must not be allowed to come into contact with the molten glass; the joints between adjacent bricks must be tight and compact, with the maximum allowable gap not exceeding 0.5 mm. The deviation between the actual elevation of the top surface of the forehearth channel and the design elevation shall not exceed ±2 mm. Construction of Glass Melting Furnaces
The quality of masonry in float glass melting furnaces directly impacts both the service life of the furnace and its operational performance. In recent years, the lifespan of float glass melting furnaces has steadily increased-with some reaching over eight years-necessitating robust safeguards regarding the selection of refractory materials, furnace construction, furnace firing, and routine production operations. During furnace construction, and depending on the specific refractory materials used, all sections-with the exception of those designated for dry-laying-must be laid using appropriate refractory mortars; furthermore, expansion joints within the masonry must be calculated and provided based on the specific thermal expansion coefficients of the refractory bricks.
