Brief analysis of the construction methods and key points of the float glass melting furnace ceiling

As the first of the three major thermal equipment for glass production, the melting furnace is the key equipment for float glass production, and the melting furnace ceiling is the heart of the entire melting furnace. Its particularity lies in its large span, long overall length, and large amount of refractory materials. It is affected by high-temperature airflow during the production process and undergoes uncertain thermal expansion.

Its construction quality will directly affect the life of the kiln, the degree of melting of the mixture, the yield rate of float glass, and the rate of superior products. This article summarizes the construction methods and experience of our company in the construction of more than 20 float lines.

01 Process principles

Adopt accurate and reliable testing instruments and scientific and reasonable construction processes, strictly control the installation quality of the ceiling wooden formwork and the quality of the ceiling masonry, set various control lines, ensure the quality of each circle of ceiling brick masonry, and thus ensure the installation quality of the float glass melting furnace ceiling.

02 Construction technology and key points

(1) Timber formwork production and installation process

Purchase materials - lay materials - lay materials and cut materials - check and assemble - wooden formwork acceptance - on-site installation of wooden formwork - wooden formwork installation acceptance - arch masonry - dismantle wooden formwork

(2) The material used for wooden formwork is generally red pine, which should be unpacked and dried in advance according to the design requirements and stored in a rainproof and moisture-proof place. Wood with knots and cracks is not suitable for making wooden formwork.

(3) Before making, the arch radius and center angle should be calculated according to the arch span and arch height parameters given in the design drawing, and then the arch radius and center angle should be laid on the platform for cutting and making.

(4) Note: After the arch wooden formwork is made in sections, it should be assembled on the platform and the center of the wooden formwork arch should be checked. The deviation should not exceed 3mm. The curvature of the wooden formwork arch should be checked with a curvature board; the installed wooden formwork should be placed neatly when used and should be protected from sun and rain to prevent deformation.

(5) Installation of wooden formwork

① After the bricklaying of the pool bottom, pool wall, breast wall and side arch is completed, install the wooden formwork. When installing the wooden formwork, the longitudinal center line of the furnace body should be found first, and then the columns should be installed.

② After all the columns are installed, use pressure strips to fix the columns vertically and horizontally, and then install the wooden arches. The spacing between the wooden arches should be controlled between 480mm and 500mm. Use pressure strips to connect and fix the wooden arches. After all the installation is completed, lay a layer of plywood, and reserve a 30mm expansion joint between the plywood.

③ The arch pops out of the longitudinal center line of the kiln body, and adjusts the center, height and curvature. The deviation between the longitudinal center of the wooden formwork and the longitudinal center line of the furnace body shall not exceed 3mm, and the height deviation shall be controlled within the range of 0 to +5mm.

④ After the wooden formwork is installed according to the masonry requirements, use wooden wedges to push it towards the breast wall, pad wooden wedges on both sides, and check that there is no hanging material on the column.

⑤ Notes on installation of wooden formwork: Both ends of the arch board should be cut into straight edges, and the distance from the arch corner brick should be no less than 50mm; expansion joints should be left when laying plywood to avoid arching when the arch is at the top, and the expansion joints should be as far away from the elastic line area as possible; the expansion joints between each two arch sections should be supported by keels, and the height should be based on the arch curvature and refer to the arch height, generally slightly higher than the arch by 20mm~30mm, so as to tie the control line.

(6) Laying of large arch bricks

① After the pre-arrangement of wooden formwork is completed, the arch bricks are pre-arranged, and one circle is pre-arranged at both ends of each arch section. The size of the mortar joint is determined according to the actual size of the on-site pre-arrangement, but the maximum mortar joint should be controlled within 1.5mm. Install the prefabricated large arc keel frame at the arch end and expansion joint. This frame should be 20mm~30mm higher than the arch brick to facilitate the pulling line.

② Laying out the line

In order to ensure the overall beauty of the large arch surface and no misalignment, a control line is laid out according to the thickness of the arch bricks in 2~3 circles. Based on the center line of the l# small furnace, the control line of each expansion joint and the position of the temperature measuring hole brick are released. The control points are also popped up on the keels at both ends of each section. This point is the reference for the line drawing on the surface of each ring of the arch brick. After the line laying work is completed, 1/5 of the bricks for the entire arch are stacked on the wooden mold, and the load-bearing condition of the wooden mold is observed. If there is no abnormality such as sinking of the wooden mold, the masonry of the arch can be started.

③ Masonry

The masonry of the arch should be completed in a relatively short time to ensure that the bricks are locked before the mortar is dry. It is not suitable to have too many people to lay the arch, and one master worker is arranged for every two meters of length. Formal masonry should be laid from both sides to the middle at the same time, and the speed should be kept consistent. If bricks need to be processed, put the processed bricks in the middle, and the upper and lower rings should be staggered. The processed bricks cannot be less than 130mm.

During masonry, the big and small heads of the arch bricks are strictly prohibited from being placed upside down. Each brick should be mortared and laid, and the mortar fullness of the flat joints and top joints should reach more than 95%. Use a rubber hammer or a wooden hammer for correction. Use a card to check the angle of the arch brick after each ring is laid, and use a 4m long aluminum ruler to check the flatness.

When 20 rings are laid on each side, pre-arrangement is carried out. If there is no change, continue construction. There are 15 rings in the middle that are pre-arranged again. If there is a change, make adjustments. Finally, three rings are staggered and laid at the same time, leaving a ring of lock bricks. The lock bricks should be left in a ring that is off-center, so that it is convenient for the laying of temperature measurement hole bricks. The protruding part of the lock brick should be left at 80mm~100mm. After the same section is laid, the lock bricks should be driven in uniformly. When driving the lock brick, a wooden board must be placed on the arch brick, and the large wooden hammer cannot directly contact the arch brick. After the entire arch is locked, clean the arch top and fill the seams with diluted mud.

④ After the arch is built, the tie rods should be tightened immediately. Before tightening the tie rods, the temporary support on the steel structure and the wooden wedges on the breast walls on both sides should be removed. The purpose of tightening the tie rods is to make the brick body of the entire arch and the supporting steel structure become a whole. The amount of tightening data is determined by the size of the arch collapse, and is roughly controlled at about 1‰ of the arch span. Generally, the force on the arch top is reflected by observing how much the arch top bulges upward after being subjected to the horizontal tension of the tie rod, that is, the method of directly observing the change of the arch top. The upper part of the arch is hung with a coordinate plate with iron wire, and its position is near the tie rods at the head, middle and tail of the arch.

When tightening the tie rods, it should be done one by one from the head of the arch to the tail of the arch. Operators are arranged at both ends of each tie rod to slowly tighten the nuts with the same force at the same time, but they cannot be tightened at one time, but should be repeated back and forth until the arch is tightened and bulges upward. After reaching the design reading, it should be observed for 8 hours until the reading does not change again before the mold can be removed.

⑤ Removing the wooden mold

Remove the wooden wedges under the column, let the entire wooden mold fall about 100m, check the overall condition of the large crown in rough lines, and then use wooden strips to push up, so that the plywood and strips on the wooden crown tire pieces are separated from the wooden crown tires, take out three pieces of wooden crown tires from the tail end, and put the other wooden crown tires down from back to front in turn. Check whether there are any crown bricks with missing corners and other situations that should not appear on the lower arc surface of the large crown. If there are any, replace them in time, and then grout and clean them.