Madison Paper remains competitive with program of technology renewal

Pulp & Paper, May 1994 by Yeager, Bob

AutoCad DCS programming. Traditionally, the programming of new DCS functions has been a constant burden to any E&I department. Madison's new DCS eliminates the programming. It includes an AutoCad software package that allows engineers to create all types of logic and control diagrams in a straightforward engineering configuration.

When the diagram is completed, an internal software package checks for completeness and accuracy and compiles the diagram into DCS machine language. "All our engineers have to do is construct the diagram, which they would have to do anyway," says Pineo. "The DCS computer does the rest for them. We use this feature constantly to create new configurations and to modify old ones." It also has great value in keeping all configuration drawings up. to-date, a difficult job in most mills.

Zone-controlled press section. Based on the scanned moisture profile after the dryer, the operator decides on the profile adjustments in the eight sections of the Sym-ZS roll across the sheet. The DCS display then shows the profile that can be expected based on those adjustments. Once satisfied, the operator keys in a "go" command, and the DCS moves the Sym-ZS roll to its new profile settings. Interlocks limit the actual profile to the roll's physical constraints.

Dye makedown system. Madison's product calls for an accurately metered combination of violet and red dye for proper shade control. The highly concentrated dye is "made down" to low concentrations before going to the headbox of the paper machine. Mill-developed "dye makedown" controls ensure that the dye content is exactly correct for each grade of SC-A.

The dye head-tanks hold precise amounts of dye to be mixed in a shared mix-tank. After mixing, the dye is released to the storage tanks and then to the paper machine headbox. Either storage tank will automatically initiate a makedown cycle when its tank level falls below a preset limit.

"Without an accurate and well-controlled makedown system, we can make off-shade reels of paper and chase our tail trying to get the right shade, due to the time delays in the system," says Pineo. The process graphic changes both tank levels and colors for the operator. Pineo designed the dye makedown system, using AutoCad and the DCS system.

Steam let-down system. Paper breaks can cause large boiler swings in a one-machine mill. In addition, dryer can pressures must be promptly reduced to expedite machine threading. After a break, the Madison steam let-down system automatically ramps down the steam pressures (and differentials) to the second, third, and fourth dryer sections. The let-down percentages are entered by the conuol room operator.

The first let-down stage takes about 40 sec. If the break goes beyond 10 min, the system automatically ramp pressures down to a lower preset level "Couple this with a feed forward control from the boiler house, and we have a very controlled steam let-down following a break," says Pineo. After threading, the ramp up also occurs in two stages and is done completely automatically. Pineo also designed this system using AutoCad and the DCS.