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Beware of dry air

Oct 1, 2005 12:00 AM


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Paper performance is not unlike that of a grand piano before a concert. The ideal environment for a piano will keep the tones crisp and prevent string shrinkage or sounding board warping. Good paper performance in the pressroom and bindery often will mean perfect ink placement without blurring or smudging, or paper consistency without curling or shrinking at the edges or unfortunate stretching. In high-speed presses, a new element of stress is added as machinery heat causes a serious drop in relative humidity (RH) —sometimes down to 25 to 35 percent RH—resulting in static electricity and web breaks.

Paper, like people, is most comfortable in temperatures ranging from 65°F to 80°F, roughly 40 to 55 percent RH, depending on function. Human beings, however, are more adaptable—paper is very sensitive to environmental changes and the HVAC needs careful control within the plant.

Baby, it’s cold outside
Large, one-ton rolls of newsprint, delivered by barge and truck to places like Chicago, often will leave Canadian mills preconditioned at 72°F to 104°F, with 10 to 35 percent RH and containing eight percent moisture. They arrive in the dead of winter, frozen. Stacked in a warehouse, they slowly thaw at around 70°F, and give up their moisture on the outside of the rolls as the temperature on the inside of the rolls rises. From the warehouse to the reel room, and up into the high-speed presses, the paper can experience some stressful fluctuations in temperature and humidity.

The Chicago Tribune found it important to introduce humidity into its Reel Room through atomizing nozzles after building Freedom Center 30 years ago. It chose atomizing nozzles because the building was an all-electric plant and there was not enough excess electric power to generate steam for humidification. These kinds of realities drive decisions for both the type and extent of humidification applied. Moisture atomizing or steam evaporative systems can be employed directly into plants or the HVAC distribution within a plant.

Printing plant humidification in the Northern United States can be a large and expensive undertaking, and investment needs a payback that makes sense to the company’s financial people. Some Northern printers have solved their environmental control problem by enclosing the space around the printers, isolating them from the huge plant, and controlling the environment within the housing. This makes the actual space to be controlled smaller and more economical. Not only is humidification possible in the winter, but air cleansing with carbon filters (to control VOCs) can be incorporated before air is exhausted to the neighborhood. Dehumidification rarely is a summer problem where there is a good air conditioning system.

The flip side
To understand the opposite situation requires a visit to a modern offset printing plant in North Carolina. There, problems arise in the hot and humid time from April to November. The plant specializes in school yearbooks, most of which are printed on glossy paper. At the exact time of the year when print volume peaks, the plant would be overwhelmed by humidity. The paper becomes sticky and the printing quality is a serious issue. Energy usage is extremely high and the plant uses rooftop compressor-based air conditioning units.

Units like these often are chosen for cost economy and rarely control the relative humidity below 50 percent. In the South, where the moisture level of outside air is always high—along with the percentage of outside air required in the printing process for make-up air, which counteracts the negative air pressure created by exhaust—the simple rooftop unit rarely is suitable. Retrofitting the units to provide preconditioning of the outside air with a desiccant dehumidification unit is possible but needs to be carefully engineered by a professional. Consider an air handler with a chilled water system, augmented with a desiccant unit to relieve the moisture before it’s cooled by the chilled water. Humidification in the winter rarely is a problem in the South.

Dehumidification is necessary in printing plants when the amount of natural moisture remains too high for the paper to accept ink properly. The use of benign desiccants to “adsorb” moisture in the air stream is something that every printing plant, regardless of location, should consider for moisture control.



Humidity—it’s all relative

Humidity is the amount of water vapor in the air. Relative humidity (RH) is a phrase many use but few truly understand. RH refers to the amount of water vapor actually in the air divided by the amount of water vapor the air can hold. In the winter months, air typically is drier (or less humid) and static charges tend to build. To avoid these shocking developments in the pressroom and bindery, consider some of the following humidification and anti-static options found here.


Antistatic wire
ionWire is a new tool for static elimination on presses, copiers, folders, laminators and in the bindery, available from StopStatic.com, a division of Alpha Innovation (Marblehead, MA). Printers can remove static from under sheets as the sheets pass over the ionWire in small gaps in a machine. Sheets emerging into space are neutralized instantly before they can cling or jog unevenly. It is available in 36-ft. spools.
See www.stopstatic.com.
Circle 184 or visit freeproductinfo.net/ap



Humidifiers for high ceilings
DRAABE’s (Chicago) high-pressure humidification system, TurboFog 32, is designed for areas with high ceilings such as the pressroom, bindery and storage facility. The atomizer’s high output per unit, per hour reportedly is cost-effective because the high-pressure technology uses minimal power without additional heating.
See www.draabe.com.
Circle 185 or visit freeproductinfo.net/ap


Warehouse mapping
Dickson Co. (Addison, IL) offers a free “Temperature and Temperature/Humidity Mapping Guide” at www.dicksonweb.com" target="_new">www.dicksonweb.com It’s a best practices guide to warehouse and production facility temperature and humidity mapping.
Circle 186 or visit freeproductinfo.net/ap



Total plant humidity coverage
Prisco (Newark, NJ) offers three PriscoTech Humidification Systems for paper storage, the pressroom and the bindery. All three reportedly reduce paper handling problems and improve register, lower dust levels up to 35 percent and decrease static electricity.

EasyMist is for small areas with low ceilings. It has no tank, to eliminate the possibility of mold build up, and is self-cleaning. Evenly spaced atomizers on poly tubing lines ensure total plant coverage.


CoolMist and ArcticMist are for the whole plant or large production area usage. These systems use no compressed air or steam, and all stainless steel pumps are submerged in water to protect against cavitation. All utilities are brought to one panel and pump/motor; zone valves and controller are prewired to the pump station.
See www.prisco.com.
Circle 187 or visit freeproductinfo.net/ap




Large space humidifiers
American Moistening Co. (AMCO) (Pinesville, NC) manufacturers large space humidifiers that will cover up to 6,000 sq. ft. and connect to a variety of electrical supply sources from 12V to 230V. Models outputting 24, 36 and 72 lbs. of water per hour are available.
See www.amco.com.
Circle 188 or visit freeproductinfo.net/ap



Eliminating static in feeders
The Ionix (Boca Raton, FL) Static Eliminator can be used on sheetfed presses, folders and collators. Users install the unit in the feeder air line; blower air passing through the Ionix Static Eliminator becomes electrically dissipative. When the treated air is blown between sheets of paper, the static-charged sheets discharge.
See www.ionixtechnologies.com.
Circle 189 or visit freeproductinfo.net/ap


Automated static control feedback system
The 986 DC Feedback System from Meech Static Eliminators (Norton, OH) automatically optimizes static charge removal by sensing the residual charge on the target material and reacting to it. The entire system consists of a sensor bar and feedback controller that automatically adjusts the ion output balance by communicating with the sensor and ionizing bar. An interpretation of the achieved static control level can be made at any time by reference to an illuminated bar graph display.
See www.meech.co.uk.
Circle 190 or visit freeproductinfo.net/ap


Making static work for you
Tantec’s (Schaumburg, IL) expandable Charging Matrix combines 10 unique charging bars and reportedly is excellent for UV-coated magazines. It transfers high voltage/high current directly to the magazines. The operator can add or remove (plug or unplug) charging bars to match workflow requirements. The components integrate easily into all incline stackers and other manufacturers’ generators.
See www.tantecusa.com.
Circle 191 or visit freeproductinfo.net/ap




Self-monitoring AC
Simco’s (Hatfield, PA) TrueAC reportedly is the only self-monitoring AC power supply available for static control equipment. The unit is designed to operate with the Blue Bar to provide consistent static neutralization of materials traveling at speeds up to 2,500 ft. per min., while also monitoring and controlling the equipment.
See www.simco-static.com.
Circle 192 or visit freeproductinfo.net/ap



Ionization bars
Takk Industries’ (Cincinnati) new ionization bars eliminate static from a distance of 36 inches. The low profile bar features a double wall barrier and is more compact. The system’s controller unit offers maximum ion stream adjustability of voltage, frequency and polarity. The bars are available in a variety of lengths.
See www.takk.com.
Circle 193 or visit freeproductinfo.net/ap



Eileen Duigan-Woods started E.D.W. Associates, Inc., in 1986 to solve complex HVAC design and construction problems. Contact her at coolit@mindsprng.com.