The role of compressed air in cold box core making

Welcome to the latest edition of Dzanetech’s series focussing on quality core making. In this edition, Dzanetech focuses on compressed air and its role in quality core making. Despite environmental factors like dust, temperature, moisture, water, and pH levels that can impact core quality, you can still achieve superior core performance.

Compressed air is a vital component used to transport and shape the sand mixture into the desired core shape. The cold box process involves mixing sand with a binder, and then using compressed air to shoot this mixture into a core box (a mould) where it is shaped. The term “cold box” refers to the fact that the curing of the binder happens at room temperature, unlike other methods that require heating.

Compressed air for blowing and curing of PUCB bonded sand requires dry air. Condensation will occur depending on ambient and compressed air temperature. A refrigerant drier will achieve around 3°C dew point only and at this level it will not prevent deterioration of the core particularly if the core shop is also humid. Desiccant driers can be set to range of -20 to -40°C dew point and are recommended. In warmer climates the dew point temperature can be higher, up to -10°C.

Compressed air quality
Moisture Control: High humidity in the compressed air can lead to increased moisture in the raw sand, which is problematic both during delivery and in-plant conveying.
Binder Reaction: Moisture in the compressed air can react with binder components during the core shooting and gassing process. This can lead to incomplete or uneven curing of the cores, resulting in defects like weak spots or surface imperfections.
Consistency: Variations in air quality, especially moisture levels, can result in inconsistencies in core strength and density.

Key Parameters to monitor
Relative Humidity: The relative humidity of the compressed air needs to be carefully monitored and controlled.
Dew Point: The dew point of the compressed air is another critical factor. A lower dew point indicates drier air, which is preferable in core making. Adjusting the dew point helps in preventing moisture-related problems.
Pressure Levels: Fluctuations in pressure can lead to variations in the core shooting process, affecting the density and quality of the final product.

Common Issues from poor air quality
Increased Defects: Poor quality compressed air, especially with high moisture content, can lead to a range of defects in the cores, such as cracks, reduced strength, and poor surface finish.
Inefficiency: Using compressed air that is not properly filtered and dried can reduce the efficiency of the core making process. This can lead to higher rejection rates and increased production costs.
Equipment Wear: Moisture and contaminants in the compressed air can also lead to increased wear and tear on the equipment, leading to more frequent maintenance and potential downtime.

Best practices for managing compressed air
Filtration and Drying: Invest in high-quality air filtration and drying systems to ensure that the compressed air is free of moisture and contaminants before it reaches the core making equipment.
Regular Monitoring: Continuously monitor the relative humidity, dew point, and pressure levels of the compressed air. Automated systems can help in maintaining these parameters within the desired range.
Maintenance: Regular maintenance of the compressed air system, including checking filters and dryers, is essential to ensure consistent air quality.

Conclusion
Compressed air is a vital component in the cold box core making process. Ensuring that the air is dry, clean, and at the correct pressure is crucial for producing high-quality cores with consistent physical properties. Closely managing and monitoring the quality of compressed air, defects can be avoided to improve overall efficiency in core production.

For further information, contact your local Dzanetech key account manager as follows: Johannesburg and Kwa-Zulu Natal – Zaid Syed: zaid@dzanetech.co.za, Paul Malone: paul@dzanetech.co.za. Johannesburg – Koketso Mamogale: koketso@dzanetech.co.za. Cape Town – Johan Jooste: johan@dzanetech.co.za. MycroKleen Agent – Gean Jooste: gean@dzanetech.co.za