The Yankee dryer remains a cornerstone of modern tissue production, facilitating the manufacture of high-quality, soft tissue products. Since its inception over a century ago, the Yankee-dryer has undergone significant technical advancements, becoming safer, more reliable, and increasingly energy-efficient. This article looks at the Yankee-dryer’s role, working principles, and adaptability, emphasizing its relevance to engineers in the tissue industry.
Table of Contents
What Is a Yankee Dryer?
The Yankee dryer is a large, steam-heated cylinder integral to tissue manufacturing. In the drying section of a tissue machine, it acts as both a dryer and a texturing device: the primary function of the cylinder is to remove moisture from the paper sheet while conferring softness, smoothness, and bulk via a special creping operation.- Yankee-dryers are designed for specific needs in production. Their enormous size, often well over 7 meters in diameter and 6 meters wide, is evidence of their critical role in the industrial manufacture of tissues. This magnitude enables efficient drying and giving texture to a variety of papers, such as facial tissues, toilet papers, and kitchen towels. Additionally, they may be employed in machine-glazed paper grades, requiring a high-gloss finish for wrapping papers and manila envelopes.
How Does a Yankee Dryer Work
- The Yankee-dryer is designed on a straightforward yet effective principle: after the paper sheet has been formed and pressed, it passes through the drying section to come in direct contact with the hot Yankee cylinder. The steam within the cylinder maintains uniform heat, enabling evaporation of moisture from the paper sheet.
- It is creped as the sheet adheres to the Yankee cylinder’s polished surface. The dried sheet is scraped off the cylinder by a doctor blade, which delicately textures and enhances the bulk of the sheet. This process of creping is critical for producing softness and absorbency associated with high-quality tissue products.
- Yankee-dryers can be tailored to specific specifications. Materials, machining, and welding in their construction must meet a wide range of operating needs. These features mean high performance, long service life, low vibration, and uniformity in operation.
Technical Developments and Advantages
Over the years, much technological innovation has been applied to the Yankee dryer. Today’s Yankee cylinder provides unparalleled safety and operational reliability necessary for high-speed production. Another major focus is energy efficiency, allowing manufacturers to meet sustainability goals while reducing operating costs.
Key Benefits of Modern Yankee Dryers:
- Improved Performance: Innovative designs ensure high drying efficiency, allowing tissue machines to run faster at full width without quality loss.
- Safety and Durability: High-precision machining and quality materials improve the structural integrity of the Yankee cylinder, reducing risks and prolonging its service life.
- Compatibility: Designed to work with a wide range of tissue-making processes, from conventional to hybrid techniques, handling variable condensing rates and high doctor blade loads.
- Process Optimization: Surface treatments and coatings improve adhesion, reduce wear, and facilitate use of specialized process chemicals.
Meeting Diverse Production Needs
Tissue manufacturing is not a one-size-fits-all process. Different products demand specific properties like softness, strength, or glossiness. Yankee dryers accommodate these needs, making them indispensable for both conventional and specialized production methods.
In traditional processes, Yankee dryers ensure broad operating windows and high pressing loads while maintaining uniformity and minimizing vibration. New hybrid processes, like Valmet’s Advantage NTT and ThruAir (TAD), bring challenges such as variable condensing rates and specialty chemicals. Modern Yankee dryers thrive in these conditions, delivering flexibility and performance.
Maintenance and Longevity
Optimal performance and long life of Yankee dryers depend on regular maintenance. Key tasks include routine inspections, metallurgical evaluations, shell thickness measurements, and doctor blade adjustments. Maintaining schedules prolongs equipment life and avoids costly downtime.
Conclusion
The Yankee dryer remains essential to tissue manufacturing, combining efficiency, adaptability, and precision. Its ability to deliver high-quality products while meeting diverse operational needs underscores its industry value. For tissue production engineers, understanding the Yankee dryer is key to optimizing performance and staying competitive. As technology advances, the Yankee dryer’s role in shaping the future of tissue manufacturing remains pivotal.
