Paper Mills Control Steam Flow on
Supercalendars with the Rosemount Model 8800 Vortex Flowmeter
Calendaring and Supercalendaring
Calendaring is a mechanical treatment in paper
manufacturing that creates and controls the smoothness and gloss of paper. For high-gloss
paper manufacturing, the process is called supercalendaring and the device is called a
supercalendar.
Supercalendars have multiple nips with
alternating hard and soft rolls and use steam polishing to create the high gloss on the
paper.
Gloss Pipes and Profilers
Mills that produce supercalendared groundwood
printing paper use two gloss pipes and two profilers to deliver steam to the sheet. The
amount of steam applied determines the amount of gloss on the paper.
The gloss pipe has openings evenly spaced along
its length. The two pipes act as an iron: steam is forced through the holes onto the paper
to press in the gloss. A scanning sensor measures the gloss of the finished sheet.
The steam flow into each pipe is measured with a
Vortex flowmeter. The set point of the steam flow is determined by a scanning sensor that
measures the gloss on the sheet.
Profilers, like gloss pipes, also apply steam to
the sheet to create a gloss, and are also positioned in pairs to finish both sides of the
paper. The profiler, however, more precisely controls steam flow for the highest gloss.
The profiler has separate compartments 6" apart with an actuator for each compartment
to control steam across the sheet. A vortex flowmeter measures the total steam flow into
the steam header on the profiler.
The Challenge of Wide Flow
Ranges
The steam demand for the profiler and gloss pipe
depends on the quality of the paper being produced. Although mills welcome demand for the
higher quality sheet because it increases revenue, this demand also creates considerable
control problems.
The wider flowrate range makes low flow
measurements difficult and low gloss paper production almost impossible to control. To
address the control problem, engineers instruct operators to shut off flow to the gloss
pipe altogether, leaving the profiler in control of the total steam demand and avoiding
the low-flow problems in the gloss pipe. Accurate steam flow measurement then becomes
critical to handle the wide range of products in this configuration.
Conventional flow measurement methods cannot
attain the accuracy required over the wide ranges demanded by a supercalendaring process
that produces papers of both high and low quality.
The Rosemount Vortex Solution
The Rosemount Model 8800 Vortex operates effectively
over the entire range demanded. A single flowmeter installation enables the production of
high quality grades within specification while improving the control of lower grades.
Accuracy and turn-down are the critical factors that point to vortex flow technology as
the solution to supercalendaring problems. Steam must be measured accurately at the high
end range to ensure the desired high gloss, high revenue product. The vortex flowmeter
also improves paper quality at the lower range with similar accuracy in measuring low end
steam flow.
The Rosemount 8800 Vortex Flowmeters are
the most reliable products in their class. They feature all welded design, superior
accuracy, HART™ communication capability, full rangeability, and world class service.
For more information, link to the 8800C product
page or Call Customer Central at 1-800-999-9307 or 612-906-8888 to discuss how the
Rosemount Model 8800C can be used in your applications.
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Emerson Process Management,
Rosemount Division, 8200 Market Blvd.
Chanhassen, MN USA 55317
North America: 1-800-999-9307 International:
952-906-8888 Fax: 952-949-7001
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