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Reasons and solutions of affecting bricks quality

2026-03-16

1, Malformed adobe, appears large cracks. In more serious cases, the whole adobe will split.

Reasons: the plasticity index of pug is too low, almost no plasticity.

Solution: to increase the plasticity index of raw materials, such as clay, coal slime or clay agent, etc.

For raw materials of low plasticity index, it can also be improved after aging, watering, stirring, rolling, extruding and other methods.

2, The body of adobe is not smooth, the obvious particles, more sand pits, and horns or flutes are missing.

Reasons: The shatter of raw materials does not meet the requirements of making bricks because there is much large particles.

Solutions: Install fine grinding equipment, as required for crushing the raw materials to make particles 3 mm or less.

Some kiln owners are not willing to spend money in equipping the machinery of raw material pre-treatment, such as roller crusher,double shaftmixers. Some kilns are only equipped with a pair of rollers, some only with mixers, some even neither of them. How can we get good bricks if there are bricks, tile, stone and other debris in the mud raw materials? Even if it is hard to send someone to pick them out clean. The fundamental way to solve the problem is equipped with auxiliary equipment.

3, The quality of adobe is unstable, sometimes good and sometimes poor.

Reasons: uneven mixing of raw materials

Solutions: Increase the mixer and feeder

Some brick factories are not equipped with rollers and mixers, even without the feeders, all by artificially feeding into the brick machine with shovel, which inevitably occurs two major drawbacks.①, raw material soil cannot be stirred and mixed well. The plasticity of raw soil is not exactly the same, and sometimes the disparity is very great, the Yellow River sludge is like that.②, the inside fuels such as coal, coal gangue, slime and others cannot be stirred evenly. The two heterogeneous, will inevitably lead to the instability of adobes’ quality.

4, malformed adobe and mud column, will spread immediately after cutting.

Reasons: Failure of the vacuum chamber

Solutions: a, improve the maintenance, service, repair technology of brick machine to ensure the normal function of brick machines’ properties. b, make the necessary technical transformation

    b, Another reason for resulting in failure of the vacuum chamber, is the sand-based raw material, so the closed mud layer of the upper auger is too thin, easy to be drawn through, causing the vacuum failure, so the adobe could not be molded. The best way to solve this problem is to change the ratio of raw materials, to increase the plasticity index of raw materials. The other way is to cut the front end of the superiors auger to 2-10 centimeters according to the material properties of soil (must be conducted under the guidance of skilled technical personnel, don’t do it by yourself).

5, Many brick cracks on adobes or broke into two sections, more wastes after sintering.

Reasons: There are too many viscous ingredients in raw materials, so the plasticity index is too high.

Solutions: change the ratio of raw materials, reduce the plasticity index. The plasticity index of clay can be up to 25, can be properly incorporated into the coal ash, slag, fly ash or waste of brick powder to make it thin.

6, Soft adobe, easy to form, or crack after cutting.

Reason: the improper control of moisture in the mud.

Solution: soft adobe, easy to be deformed, showing that the water of sludge is too much, should reduce water. If the mud column quickly occurs crack or split of mud column after molding, which is caused by too little water in mud, it can be solved by increasing appropriate water.

7. Brick production capacity not stable

Reason: Not equip with box feeder

Solution : Some brick factory owners in order to save money, they refuse to use box feeder but some labors to feed soil manually .Therefore, soil feeding amount is not stable,sometimes more than what the extruder need, some times, less what extruder need, thus greatly influencing production capacity.

All in all, there are all kinds of raw materials to make bricks, in addition to the different climate, some abnormal situations inevitably occur in the production and it is really hard to avoid. If there are problems, knowing the following two points will be easy. One isto havea team with a strong sense of responsibility and a technical team ofprofessional mechanics. Two is to timely communicate high and difficult technical problems with industry colleagues.

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Related questions
1
Why Your Tunnel Kiln Brick Firing Fails: The Hidden Role of Proper Stacking Methods
If you’re dealing with inconsistent brick quality, uneven firing, or low production yields from your tunnel kiln, you might be overlooking one critical factor: how you stack your green bricks. Many brick manufacturers invest heavily in advanced kiln equipment but ignore the fundamentals of setting—leading to wasted fuel, higher breakage rates, and lost profits.
At our company, we specialize in optimizing tunnel kiln operations, and we’ve seen firsthand how poor stacking practices can derail even the most modern production lines. Once the setting pattern is fixed, the airflow resistance, fuel distribution, and heat transfer inside the kiln are largely determined. Operators can only adjust firing conditions within narrow limits, making proper stacking the foundation of stable, high-quality production.

The Direct Impact of Stacking on Firing

  • Airflow & Velocity: Stacking density directly controls airflow volume. Overly tight settings increase resistance, reducing ventilation and causing incomplete combustion. Loose settings waste heat and increase fuel consumption. Even within a single kiln car, uneven channel sizes create velocity differences, leading to temperature stratification.
  • Cross-Section Heat Distribution: Hot air naturally rises, causing faster flow at the top and edges. Without adjusted stacking density, upper and outer bricks underfire while center bricks overfire.
  • Fuel Distribution: Stacking patterns act as the blueprint for fuel placement. Misaligned settings lead to hot spots and cold zones, ruining batch consistency.

Our Proven Stacking Optimization Principles

We recommend starting with the “sparse stacking for fast firing” rule. By balancing setting density with your kiln’s exhaust capacity, you can boost airflow, enhance heat transfer, and speed up kiln car turnover. Our team also applies the local principles: top-dense, bottom-sparse; center-dense, outer-sparse; straight bricks preferred. These techniques have helped clients achieve a 99.8% finished brick rate and reduce energy use to 220–260 kcal/kg.
If you’re struggling with firing inconsistencies, let us analyze your current stacking setup. Our experts can design custom patterns tailored to your raw materials, kiln design, and production goals—helping you unlock higher yields and lower costs.
2
How to Speed Up Tunnel Kiln Firing？
If you want higher brick output, lower energy consumption, and stable quality, mastering tunnel kiln fast firing technology is essential. For modern automatic brick plants, “dry bricks in, sparse setting, strong ventilation, stable temperature & fast pushing” has become the standard for high-efficiency production.
1. Improve green brick quality: dry and hot input
  • Control moisture content below 3% before entering the kiln.
  • Preheat green bricks to raise temperature before loading.
  • Dry, hot bricks fire faster, reduce cracking risk, and save fuel.
2. Optimize brick setting: sparse setting for fast firing
  • Reduce setting density by 10–15% vs traditional mode.
  • Keep uniform gaps between brick columns for smooth hot air flow.
  • Avoid blocking airflow; ensure even heating in preheating zone, firing zone, cooling zone.
3. Strengthen ventilation: balance exhaust & air volume
  • Properly open exhaust dampers to speed up flue gas flow.
  • Increase fan frequency reasonably to enhance oxygen supply.
  • Avoid over-ventilation which causes under-fired bricks.
4. Adjust firing temperature & fuel
  • Raise firing temperature by 10–15°C (within raw material limits) to shorten cycle.
  • Shorten holding time while ensuring sintering quality.
  • Increase internal combustion ratio, adopt small & frequent external coal feeding, or switch to natural gas/oil firing for faster, uniform heating.
5. Accelerate kiln car pace
  • Shorten car interval and match zone lengths reasonably.
  • Fast, stable pushing ensures continuous mass production.
By focusing on dry brick preparation, sparse setting, balanced ventilation, precise temperature control, and optimized fuel, your tunnel kiln can achieve higher capacity, lower cost, and consistent brick quality in competitive global markets.
3
How to Eliminate Spiral & S-Cracks in Clay Bricks？
Spiral cracks and S-cracks are the most frequent structural defects in clay brick manufacturing. These undesirable imperfections lead to high scrap rates, raw material waste, and poor finished brick appearance. This practical guide summarizes mature industrial solutions covering raw material treatment, extrusion optimization, moisture adjustment, equipment maintenance, and kiln processing, helping global brick manufacturers reduce defect rates and maximize production profits.
1. Optimize Raw Material Gradation & Reduce Clay Plasticity
Reasonable particle gradation is the foundation of crack prevention. Manufacturers should mix 20% to 30% coarse aggregates such as grog, shale, and coal gangue into raw clay. Coarse particles enhance interlayer friction and restrain clay internal sliding. Meanwhile, reduce high-plastic clay proportion and add limestone powder or quartz sand to lower drying sensitivity.
2. Balance Extrusion Speed & Optimize Clay Flow
To solve uneven flow velocity, install adjustable resistance bars at the extruder head to slow down the central clay flow and balance overall extrusion speed. Replace ordinary blades with variable-pitch spiral blades to reduce shear difference. Keep the gap between spiral blades and machine cylinder within 2mm for stable extrusion molding.
3. Precise Moisture Control for Raw Clay & Green Bricks
Control the raw clay moisture steadily between 18% and 22% according to local clay properties. Adopt staged slow drying technology for green bricks; keep the initial heating rate below 20°C/h to avoid surface crusting. Uniform moisture removal effectively prevents shrinkage cracks and layered cracks.
4. Standardize Daily Extruder Maintenance & Parts Replacement
Establish regular equipment inspection cycles. Timely replace worn spiral blades and damaged cylinder liners to guarantee stable pushing force. Check extruder head sealing and gaps weekly to avoid disordered clay flow caused by mechanical aging. Scientific maintenance reduces artificial brick defects greatly.
5. Upgrade Drying & Sintering Kiln Curves
Adopt gradient heating mode in drying chambers and tunnel kilns. Control the heating rate between 20°C/h and 30°C/h with sufficient constant-temperature holding time. During quartz crystal transformation (600℃-900℃), slow down heating speed below 40°C/h to relieve internal thermal stress.
Eliminating spiral and S-cracks requires systematic production management from raw materials to finished bricks. Scientific formula proportion, optimized extrusion equipment, precise moisture monitoring, standardized maintenance, and improved kiln technology can reduce brick scrap rates by 5%-10%. Stable product quality helps brick factories occupy more shares in the global construction material market.
4
How to Boost Brick Factory Output?
For modern brick factories pursuing stable production and high profits
low output and high defective rates have always been troublesome problems. Many brick plant owners blindly upgrade brick making machinery and increase production frequency, but ignore the core bottleneck restricting production efficiency—the drying process. In the actual brick production workflow, the drying section is the key link that determines the qualified rate of green bricks and the daily output of the entire brick factory. Relevant industry data shows that reducing the moisture content of bricks before entering the kiln can directly bring obvious output growth; every 1% reduction in kiln entry moisture can increase brick production by 3% to 5%.
Many brick factories have unreasonable drying settings, resulting in long drying cycles, damp green bricks, and mildewed blanks, which not only reduces the drying qualification rate but also causes adverse effects on the subsequent kiln firing process. To break the drying bottleneck of brick factories, enterprises need to optimize two core indicators: drying temperature and moisture exhaust efficiency.
  • First, reasonably increase the drying temperature according to the raw material characteristics, and ensure uniform temperature distribution in the drying chamber to avoid uneven drying of green bricks.
  • Second, strengthen the moisture exhaust system of the drying workshop, timely discharge water vapor generated in the drying process, and prevent water vapor from condensing on the surface of green bricks to cause secondary moisture regain.
In addition to temperature and moisture exhaust optimization, raw material management is also an auxiliary measure to improve drying efficiency. Brick factories need to maintain stable raw material ratio and uniform internal combustion blending. Frequent replacement and proportion adjustment of raw materials will lead to inconsistent moisture characteristics of raw mud, which increases the difficulty of drying control. Uniform internal combustion mixing can avoid local underfiring and reburning of bricks, reduce defective products caused by unreasonable combustion, and further cooperate with the drying process to improve the overall qualified rate of bricks.
For brick making equipment
the operating state of the molding end also indirectly affects the drying effect. The extruder needs to maintain a reasonable running speed while ensuring the compactness of the green bricks. The stable vacuum degree above 0.085 is an essential standard for high-quality brick blanks. Worn reamer blades should be replaced in a timely manner to prevent loose green bricks from being difficult to dry thoroughly. Only when the quality of molded bricks is up to standard can the drying link exert the maximum efficiency advantage.
In the production logic of brick factories, the optimization priority must be clear:
prioritize solving drying problems, then stabilize the firing process, and finally carry out equipment speed increase transformation.
It is necessary to clarify a core principle: the real output of a brick factory refers to the number of qualified bricks. Excessive defective products and reburning bricks will completely offset the production growth brought by equipment acceleration. Optimizing the drying system is the lowest-cost and highest-return way for most brick plants to increase production, which is suitable for small and medium-sized brick factories with limited transformation budgets.
5
How to Prevent Clay Bricks from Collapsing in Tunnel Kilns？

1. Pre-firing Material Constraints (The "Foundation" Stage)

Collapse often begins before the bricks even enter the kiln if the green body lacks physical integrity.

  • Moisture Threshold: The residual moisture content must be kept below 6%. High moisture levels drastically reduce the compressive strength of the bricks, causing the bottom layers to buckle under the weight of the stack.

  • Material Aging: Clay requires at least 3 days of aging to ensure uniform plasticity and water distribution. Insufficient aging leads to internal stresses and a fragile structure.

  • Mechanical Density: Ensure an extrusion pressure of ≥40kg/cm² to increase the density of the green body, making it more resistant to deformation at high temperatures.

2. Strategic Stacking Techniques (Mechanical Stability)

Stacking is not just about volume; it is about managing gravity and thermodynamics.

  • The "Four-Point" Standard: Stacks must be level, stable, vertical, and straight. Any minor deviation in the center of gravity will be amplified as the bricks soften in the heat.

  • Airflow Optimization: Follow the principle of "Dense Edges, Sparse Centers" and "Dense Tops, Sparse Bottoms." This balances the temperature across the kiln cross-section, preventing the edges from over-firing while the center remains under-fired.

  • Load Management: Due to the high sensitivity of clay, limit the stacking height to 12 layers or fewer. This minimizes the static pressure on the base bricks.

3. Dehumidification in the Preheating Zone (The "Critical" Stage)

This is the most common zone for collapses. If moisture is not evacuated efficiently, the bricks effectively "steam" and lose their rigidity.

  • Inlet Temperature Control: Keep the initial drying air below 116°C. Temperatures above this threshold cause the surface to harden too quickly, trapping steam inside and creating internal pressure.

  • Heating Rate: Maintain a steady rise of 6–8°C/h. Sudden temperature spikes, especially in winter, can cause thermal shock and structural failure.

  • Ventilation and Pressure: Ensure the exhaust fan provides sufficient negative pressure. Poor ventilation causes moisture to linger and re-condense on the bricks, leading to "soggy" bricks that collapse instantly.

4. Firing Zone Temperature Management (Thermodynamic Control)

Once the bricks reach high temperatures, preventing them from entering a pyroplastic state (melting) is vital.

  • Anti-Overfiring Measures: Strictly monitor the sintering peak. Exceeding the clay's softening point leads to viscous flow, where the bricks begin to behave like liquid and slump.

  • Internal Fuel Ratio: Control the amount of internal additives (coal powder or gangue). Excessive internal fuel generates uncontrollable heat within the stack, causing the bricks to "melt from the inside out."

  • Visual Monitoring: Use inspection holes to watch for "white-out" conditions or "shimmering/swaying" stacks, which are immediate warning signs of imminent collapse.

5. Infrastructure and Mechanical Integrity (Environmental Factors)

The physical environment of the kiln must remain consistent to prevent mechanical triggers.

  • Track Leveling: Regularly inspect kiln car tracks. Uneven rails cause vibration and jolting, which can topple a stack that is already weakened by heat.

  • Kiln Structure Maintenance: Check for sagging roof bricks or protruding exhaust ports. Mechanical obstructions are a frequent cause of "domino-effect" collapses during car movement.

6
How to Crusher Output in Sintered Brick Plants Efficiently？
In sintered brick production lines, the output and quality are often restricted by four key pieces of equipment: crushing equipment, belt conveyor equipment, vacuum extruders, and kiln thermal equipment. Among them, jaw crushers and hammer crushers, as common primary and secondary crushing equipment, directly determine the overall production efficiency of the entire line. Many brick plant operators are eager to maximize crusher output while ensuring the particle size of crushed materials—here are practical and actionable tips to achieve this goal.
First, ensure proper feeding. To make the jaw plates wear evenly and reduce operating costs, gangue or hard shale should be evenly distributed along the feeder inlet and fill the crushing chamber completely. Uneven feeding will not only accelerate jaw plate wear but also reduce crushing efficiency, leading to unnecessary energy waste.
Second, adjust the feeder amplitude reasonably. During normal use of the feeder, you can adjust the amplitude through the knob on the control box within the rated amplitude range according to the required productivity, so as to achieve stepless adjustment of the feeder. Sufficient amplitude ensures that materials enter the crushing chamber continuously and stably, avoiding gaps that affect output.
Third, pay attention to feeding precautions. It is crucial to prevent iron blocks from entering the crushing chamber, as iron blocks can damage jaw plates and other key components. The height of the materials to be crushed should not exceed the fixed jaw plate, and the maximum feed particle size should be smaller than the feed inlet—large blocks are likely to block the crushing chamber and reduce crushing efficiency.
Fourth, set a reasonable discharge port size. The discharge port is the distance between the two jaw plates at the lower end of the crushing chamber. Too small a discharge port will cause blockages and excessive energy consumption, leading to serious damage to the crusher; too large a discharge port will increase the load of the second crushing. Finding the optimal size according to the production needs is the key to improving output.
In addition, regular inspection and replacement of jaw plates, proper lubrication of bearings, and scientific adjustment of the discharge port opening are also essential links to ensure stable and high output of the crusher. By following these tips, sintered brick plants can effectively improve crusher production capacity while ensuring product quality.
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