Metering size press panel - Unpigmented applications

Puddle-type size presses have long limited operating speed on fine paper machines. High forces on the web in the puddle cause sheet breaks when defects or weak areas in the web reach the size press. A high percentage of sheet breaks occur at the size press on well run machines. Size press roll diameters as high as 60" reduced starch nip rejection and raised practical operating speeds to 3,000 fpm. Gate roll coaters, LAS units, Billblade coaters, and other concepts used for starch application provided some advantages but were note widely accepted for fine paper manufacture due to other limitations. Metered film size presses are now being used on board and specialty grades. Use of coating concepts where starch was metered onto rolls with blades or rods ahead of a nip provided a break-through that permitted significantly higher machine speeds. Commercial fine paper machines with metering-type size presses are now running over 4,000 fpm and speeds up to 5,000 fpm are being discussed. The transition to metering-type size presses has been troublesome and much "field development" has been required. Issues around metering-type size presses include: a. Roll, blade, and rod life b. Starch quality, pH, temperature, and solids content c. Sheet runs d. Entering moisture content and profile uniformity e. Base sheet requirements f. Effects on paper quality g. After-size drying requirements h. Ventilation requirements i. Starch make-up system design. Superintendents operating a mix of old and new paper machines will discuss their experiences with metering-type size presses.