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Formation improves when a dandy roll is used with a fourdrinier, but a more striking improvement is made when a fourdrinier is converted to a hybrid former. Then, the stock enters a wire nip partly drained at about 2% average consistency, having been subject to MD shear at the entrance. As stock is pulled in against the higher pressure between the curved fabrics, a shearing and rolling action occurs which is effective in dispersing floes. The subsequent more rapid drainage reduces the extent of re-flocculation and helps to freeze the dispersed structure. |
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