Tissue360 - Spring/Summer 2014 - (Page 20)

feature | STEAM SHOWERS Improve the Effectiveness of Your Steam Showers Experts say that as much as 60 percent of steam showers used on paper or tissue machines to improve consistency or moisture profiles, are ineffective GARY WAMSLEY Process reviews at numerous mills over several years have indicated that many machines have ongoing operational challenges with steam shower performance, including: structural corrosion around the machine frame and hoods, Yankee coating release problems, unresolved wet and dry streaks in the sheet, a vapor cloud around the shower unit, frequent sheet breaks and short life of carrier felt or pressure roll cover. This article is based on those experiences and will serve as a guide to better understand steam showers, improve operations and reduce waste and energy costs. Steam shower at OptiLoad TwinLine multi-nip calender at StoraEnso Kvarnsveden Ab, Borlänge, Sweden 20 Tissue360º SPRING/SUMMER 2014 HISTORY Installation of steam showers on tissue machines dates back to the mid 1980s. Initially they were installed on conventional Light Dry Crepe (LDC) machines to enhance performance where drying limitations existed. In addition, reducing moisture peaks helped improve creping performance and also confirmed the difficulty of maintaining a good Yankee dryer surface coating in zones that have heavy wet/dry streaks. Steam showers have also been installed on newer technology Through-Air Drying (TAD) machines to improve sheet moisture variability and increase sheet consistency before the dryer. Due to rising energy costs in the 2000s, technical reviews at several mills identified steam showers as a way to optimize machine performance. There are a wide range of system designs, operating conditions, control strategies and opinions about the benefit of steam showers. Some older mills with smaller machines have had some degree of success utilizing a fabricated 3-in. steam header and 3/4-in. pipe nozzles on 6-in. centers, as a manual steam shower (drawing available upon request). Due to this wide range of equipment, processes and experiences, process engineers need to better understand the design and operational requirements of this equipment as well as how the steam system affects overall performance in order to maximize production and optimize efficiency. CHECKING THE LITERATURE TAPPI offers several reports that, in general, confirm that steam showers can improve operations. However, trials designed to optimize the system and document the most idealized performance (under different equipment conditions, base sheet conditions and steam conditions) have not been very well reported. One study on LDC machines conducted in the mid-1980s discusses machine production improvements, moisture profiling impacts, energy usage, felt temperatures and changes observed at various operating conditions. That facility continues to use its units, but upto-date performance data is sketchy; operational degradation over time was confirmed as a common occurrence. A dewatering study was conducted on TAD machines in 2002 and 2003. Machine conditions, with and without the unit in service, were changed to study the effects; however, steam conditions were not changed. It was concluded that the minor improvement that occurred was not cost effective and production demands and personnel constraints prevented an extended assessment. KEY POINTS TO CONSIDER System design. Steam shower designers have a unique challenge: to develop and provide a robust system and controls that will cause condensation heat transfer to occur on the sheet for a wide range of changing operating conditions. Steam cost, depending on fuel and steam plant design, can significantly affect the economic benefit of a steam shower system. www.tappi.org http://www.tappi.org

Table of Contents for the Digital Edition of Tissue360 - Spring/Summer 2014

Automatic Handling International, Inc.
Goldenrod Corp.
Cascade Corporation
Tissue Industry News
Spraying Systems Co
Success in New Hampshire: Gorham P&T Optimizes New Tissue Machine Production to Premium Quality
OpTest Equipment. Inc.
Are We Running Out of Recycled Fiber?
Heuchling Group
Improve the Effectiveness of Your Steam Showers
M Torres
Mechadyne Machine, Inc
Myron L Company

Tissue360 - Spring/Summer 2014