Splicing of Glass Kiln Lip Bricks

Glass Kiln Lid Bricks used in rolled glass forming can be made from a single piece or from several bricks joined together. The choice between a single brick and several bricks depends on many subjective and objective factors, such as brick quality, brick cost, production cycle, glass specifications, and operator skill level. The basic principle is to ensure product quality, prevent defects during use, and guarantee durability.

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Solid Lid Brick

The length of the solid lip brick is determined by the length of the calendering roll. The advantages of using a solid lip brick are:

1. Not limited by glass specifications, meeting the cutting needs of various glass sizes;
2. Good stability during operation, with virtually no displacement or tilting;
3. Compact, stable, and robust assembly with the support structure.

The disadvantages are: It is prone to breakage, with severe cases showing 4-5 cracks. The brick is relatively long and heavy, and assembly and transportation are inconvenient due to space constraints.

Two Lip Bricks Joined Together

A set of lip bricks consists of two pieces joined together, each piece being half the length of the calendering roll.

The advantages of using two pieces are:

1. It distributes the various forces acting on the lip brick, reducing the probability of cracking;
2. Each brick is lighter, making assembly, transportation, and movement easier.

However, using two pieces together has many disadvantages, including:

1. It is difficult to guarantee the quality of the assembly, mainly due to larger joints between the bricks and the tendency for misalignment to occur on the upper surface of the lip brick, resulting in overall unevenness;
2. During operation, the brick joints often widen, tilt, shift, or even misalign;
3. The assembly process is time-consuming and labor-intensive.

There are three methods for splicing two lip bricks together:

• Method 1: Make semi-circular grooves downwards on both sides of the splicing surface of the lip bricks, 10mm from the top plane of the lip. After splicing the two bricks, the semi-circular grooves on both sides will form a circular hole. Fill the hole with mortar, ensuring it is completely filled. After fixing both sides, place it near the kiln and bake at high temperature for a period of time. At this point, the refractory mortar inside the hole will have dried and solidified. If the bricks expand when heated, the resulting cylindrical refractory material will not fall off, sealing the joint between the two bricks. Therefore, no air enters, reducing the release of air bubbles and minimizing the impact on the temperature of the surrounding molten glass.
• Method 2: Soak ceramic fiber paper (<1mm thick) in molten glass, then apply it to one side of the lip brick, and then align them together. After completion, bake it near the kiln.
• Method 3: Dry splicing. Join two well-fitting lip bricks together, ensuring the gap between them is less than 1mm, and then tighten them with screws on both sides before use.

Three-Piece Lip Brick Assembly

A set of lip bricks consists of three pieces joined together. The middle piece is 2-2.2m long, and each of the two ends has a lip brick joint of 250-350mm.

Advantages:

1. The two joints release more of the compressive force generated by the expansion of the lip bricks, reducing the probability of cracking.
2. The length of the middle brick can meet the production needs of various glass sizes.

Disadvantages:

1. The structure is unstable, making it difficult to guarantee the quality of the splicing. Misalignment on the upper surface of the lip bricks at the joints can make expansion and contraction of the glass difficult.
2. There is a possibility of tilting or displacement during operation.
3. More fastener installation work is required during online assembly, resulting in a longer cycle time.

Whether used as a single piece or in combination of multiple lip bricks, the lip bricks must be assembled, installed, and fixed to a support frame. Production lines using brick-making calenders initially employed online assembly. However, after a period of trial and error, it was found that online assembly was neither convenient nor guaranteed in terms of quality. Therefore, many companies now use offline assembly, where the assembled bricks are transported to the overflow port by a mobile trolley and installed at the outlet. Production lines using integrated brick-making calenders also use offline assembly, where the lip bricks are assembled and fixed to a support frame outside the production line, and then hoisted and installed as a whole onto the calender frame.

When assembling lip bricks, the upper flat working surface serves as the reference horizontal plane. By processing the brick material or adding leveling shims at the bottom, the lip brick is ensured to be horizontal, with its contact surface with the tail brick perpendicular to the horizontal surface. The joint between lip bricks must be straight and as small as possible, less than 1mm after assembly. There should be no misalignment of the lip brick tips; the tips should be kept in a straight line along the tangent direction. The curved surfaces of the assembled bricks must be on the same plane, without any misalignment or stepped formations. Mullite fiber paper must be used to separate the lip brick from the tail brick, the lip brick from the edge brick, and the lip brick from the support. The center longitudinal direction of the lip brick should be aligned with the production line, the tangent direction parallel to the edge, and the normal direction perpendicular to the top plane of the lip brick.

Online assembly of lip bricks involves high-temperature operation in a confined area. Besides the long operation time (approximately 1-2 hours), the assembly quality of the lip bricks and supports, and the supports and calenders, is inferior to offline assembly. It also negatively impacts the kiln temperature regime.

Offline assembly offers a better working environment, lower labor intensity for workers, and doesn’t interfere with brick-changing time. It allows ample time and space for assembly, enabling precise positioning of the lip brick’s front-to-back and left-to-right spacing with the rollers. If bricks or steel components are unsuitable, they can be processed offline, ensuring the assembly quality of the lip bricks and supports, and the supports and calenders, saving brick loading time. Brick changing can be completed quickly with minimal kiln temperature changes, facilitating rapid production recovery. However, once the integrated brick-making calender is positioned, the relative position of the tail brick cannot be moved, lacking a means to handle defects. In actual production, damage can occur on both sides during the lead-in operation, especially for those accustomed to using a pull-in lead-in system. Once the edge is damaged, the machine must be replaced, and the tail brick must be replaced along with the lead-in brick. Separating the lip brick and tail brick involves long working hours, a poor working environment, and high labor intensity. The heat-resistant steel lip brick support integrated with the brick machine has poor deformation resistance, is prone to bending at high temperatures, and is difficult to restore for reuse after deformation, resulting in waste.