Yankee Dryer Dry Creping Basics
The Yankee dryer is a large, steam-heated, pressure vessel that is used in the production of tissue grades. After the tissue sheet is dried by the Yankee dryer and Yankee hoods to its final moisture target, it is creped and removed from the Yankee by the creping doctor. The “dry creping” process is responsible for the bulk, stretch, and softness that are desirable in tissue grades. This course describes what happens to the sheet during dry creping, factors that influence dry creping results, the design and operation of the creping blade, and blade angles and sheet angles associated with the creping blade.
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Learning Objectives
• The dry creping process
• The differences between wet crepe and dry crepe
• Creping blade setup and geometry
Specs
| Course Level | Intermediate |
| Languages | English |
| Compatibility | Audio, Video |
| Based on: | Industry Standards and Best Practices |
Key Questions
What is dry creping?
Dry creping is creping a fully-dried sheet off the Yankee dryer.
What sheet properties are affected by the creping process?
Creping impacts caliper/bulk, stretch, softness, and tensile strength.
What factors affect crepe quality?
The crepe is affected by the speed difference between the reel and the Yankee dryer, creping blade angles and loading pressure, creping blade length or “”stick out””, sheet adhesion to the dryer surface, and creping blade design and geometry.
What is the blade wear angle?
It is the angle of wear on the creping blade. It is equal to the angle between Yankee tangent line and the back of the creping blade under operating loads.
What is the creping pocket angle?
The creping pocket angle is the angle between the Yankee tangent line and the top edge of the creping blade.
Sample Video Transcript
The last important angle is the creping angle or pocket angle, which is defined as the angle between the Yankee tangent line and the creping blade surface. The crepe pocket angle is very important in determining the resulting crepe structure in the sheet. Crepe pocket angles typically range from 65 to 95 degrees. It is interesting to note that during production, the creping angle is actually determined by the blade wear angle and the blade grind angle. The relationship between them is described by this equation, creping angle equals 90 degrees minus blade wear angle plus blade grind angle. This means that the creping angle can be increased by either increasing the blade grind angle or decreasing the blade wear angle.
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