To run lean, you must be clean: good machine hygiene is a key to efficient machine operations.
All paper machines have cleaning systems, but these systems must be well operated and maintained to minimize fabric wear, fabric filling, and machine contamination. "Effective machine hygiene can move a machine closet- to steady state operation, reduce energy use, and improve profile and finish, among other benefits," said John A. Neun, P.E., product manager, cleaning and conditioning, Kadant-AES, Queensbury, New York, USA. "If you pay a little attention and invest a little capital in machine hygiene, the payback includes lower costs in three critical areas: fiber, energy, and machine clothing."
WHAT IS MACHINE HYGIENE?
Paper machine hygiene typically focuses on three areas:
* Sheet contact moving parts, such as fabrics and rolls
* Stationary elements and structures, such as paper machine frames
* Screening and stock contaminant control
Good machine cleanliness help create good cross machines profiles, basis weight profiles, long fabric life, and lower energy usage," said Neun. "Poor cleanliness create many different problems. For example, poor machine hygiene can create sheet streaking, but that is not the only problem. Paper mills use a lot of energy trying to correct sheet streaking-energy that is essentially wasted."
Machine clothing must be cleaned regularly and usually continuously through showering and conditioning. Cleaning elements include full coverage tan showers, high-energy needle jets showers, and single jet showers.
Likewise, roll surfaces must be cleaned regularly using doctor systems. Finally, water (mist) and contaminants must be controlled and removed through effective Uhle box operation and ventilation/mist elimination.
"Misting may not seem like a major problem, but mist carries fiber and filler," said Neun. "When the mist condenses on paper machine frames, the fibers and fillers term deposits that can then drop onto the sheet and cause breaks. To control this, mills must use shower systems that don't spew excess water and vacuum containment units."
MAINTENANCE IS KEY
Most machines have good cleaning systems, but mills run into problems when they neglect system maintenance. "If a machine if having other problems, secondary systems like cleaning systems don't get a lot of attention," said Noun. "Some superintendents take an 'if it ain't broke, don't fix it' approach. That is a mistake. If mills are experiencing poor felt life problems with MD and CD sheet and fabric profiles, or poor press roll cover conditions, they need to look at machine hygiene. They should look for problems such as plugged shower nozzles, poor water flows, and improper water balances in Uhle boxes."
All of these conditions are telltale signs of poor machine hygiene. "The better run mills use preventive maintenance on cleaning systems. It's a lot cheaper to replace spray nozzles than to put an extra set of clothing on twice a year," concluded Neun.
Interact with John Neun on the Web on October 10 during live TAPPI Virtual Seminar
John Noun of Kadant-AES will lead a TAPPI Virtual Seminar on Paper Machine Hygiene on October t0 from 2:00 to 3:00 PM, Eastern Standard Time. Participants can register and then phone in to join the seminar, which will provide participants with improved understanding of paper machine cleaning systems and the ability to improve paper machine efficiency through more intelligent operation. Neun will discuss theory and application of showers, dewatering systems, mist removal systems and doctoring. He will use application specifics and examples to illustrate concepts. Register for the Machine Hygiene Virtual Seminar on www.tappi.org or by calling the TAPPI service line at 1 800 332-8686 in the United States: 1 800 446-9431 in Canada or at + 1 770 446-1400 from outside the U.S. and Canada.
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|Title Annotation:||Four Minute Focus|
|Publication:||Solutions - for People, Processes and Paper|
|Date:||Sep 1, 2002|
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