Tissue360 - Spring/Summer 2014 - (Page 20)
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
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
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
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
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
Table of Contents for the Digital Edition of Tissue360 - Spring/Summer 2014
Automatic Handling International, Inc.
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?
Improve the Effectiveness of Your Steam Showers
Mechadyne Machine, Inc
Myron L Company
Tissue360 - Spring/Summer 2014