- Written by Dave Smith
Dryer basics can be broken down into four essential categories; neat, tumble, airflow and control. A good heat source is crucial for short heat cycles and efficient drying. Natural gas is most often used in the U.S. to provide these important criteria.
Natural gas burners are available in two main types, atmospheric and forced-air styles. Atmospheric designs provide a flame at atmospheric pressure for the air to pass through to become hot. Forced-air burners mix air and gas inside a chamber under pressure. This provides a very efficient and high-temperature burn, which brings the load to temperature set point more quickly.
Today’s most efficient dryers not only possess a forced-air gas burner, but they also have the ability to modulate the fuel input through use of a modulating gas valve. As the temperature set point is reached, these dryers can adjust the gas usage by slowing the fuel input.
GOODS TAKING A TUMBLE
Tumbling action is required to separate the load, allowing the hot air to penetrate the goods. Correct material drop moves the load from the basket top and dumps it through the basket center. To avoid tangling of large items, the basket rotation may be reversed, every minute or two.
As the products dry, lighter goods may cling to the basket sides and rotate around. Some dryers permit a change in basket rotation speed to assist with proper material drop for varying load types.
A forceful airflow is required in order to pull the moisture from the load. Dryer manufacturers use varying ways to introduce air into the goods… from the top-out the bottom, from the bottom-out the top, from the sides-out the bottom, or from the rearout the front. Which way is best? It comes down to performance.
With a quality heat source, tumble action and airflow, there must also be control over these functions. Microprocessors and PLC’s permit precise control over the burner modulation, formula set-ups, airflow and basket rotation speeds, along with many other features. Even smaller dryer designs now offer built-in controls to help determine the suitable time for heat termination.
QUESTION YOUR SUPPLIER
Question your potential supplier. What dryer processes are programmable and what are not? How many programmable formulas are available? How does the dryer determine heat cycle termination? Is the burner system a simple Hi/Low fire system, or does the dryer modulate the gas input? Is the burner a forced-air type or an atmospheric design? Does the formula have control over basket rotation speeds or basket reversing? How is good airflow achieved?Overall dryer performance is the bottom line, but getting answers is not easy. The problem is that there are so many variables for drying. Material types, extraction levels and load sizes all affect the end results.
An industry standard is needed, here. Dryer performance can best be shown through production and efficiency results.
- Production = Pounds of H2ORemoved per Minute
- Efficiency = BTU’s Used per Pound of H2O Removed
Ask your equipment provider to supply production and efficiency numbers for certain products when washed in your type of washer. Use this information for comparison purposes in your overall wash isle evaluation. Do the numbers equate when reviewing the number of dryers suggested by this supplier for your operation?
UNDERSTAND YOUR MACHINE
Further scrutiny should be made in the areas of lint removal and other maintenance issues. Understand how lint removal is performed and what is required to keep the dryer, collector and ductwork clean.
Most industrial dryers have a built-in water spray system that is activated when an overheat condition in sensed. What happens if the electricity goes out? Will the system continue to operate? Should the dryer’s emergency stop button be pushed to stop the basket rotation and gas flow? These items should be discussed prior to a dryer purchase.
What maintenance expertise is the supplier requiring from your company? A higher level of knowledge may be required to deal with the new controls and other high-end components. Temperature probes, humidity sensors and infrared sensors must be tested and calibrated, as needed.
Metering of dryers is a good idea. Can you perform periodic checks that should be made to compare performance results with a standard? This method is a good way to detect problems before they cost you time and energy dollars.
Are your people required to move about in areas where automation is occurring? Are the manuals adequate in explaining how to maintain the equipment safely, especially in hazardous areas where your people may be exposed to natural gas, electricity and moving components?
If you’re not in an automated environment, think about load handling issues. Soiled 250-lb. washer loads turn into wet clean 375-lb. dryer loads, even after high-extraction. Find beneficial solutions for your employees who must handle these weights.
With a good understanding of dryer basics, you will be better prepared to make a proper equipment evaluation for your company.
For more information concerning dryer basics and helpful ideas, please visit Web site www.TheDryerGuy.com
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Textile Services Industry Gets National Spotlight
WILIMGTON, Mass. — Textile service executive Ronald Croatti recently appeared on the CBS-TV show “Undercover Boss.” Croatti is CEO of UniFirst Corp., in Wilmington, Mass. For most Americans watching “Undercover Boss” it was their first view inside a commercial laundry, which typically process between 10 million and 25 million pounds of uniforms, table linens, bed sheets, towels and more every year “The reusable textile services business is the original green industry,” said Ricci. “Commercial laundries reuse linen instead of filing landfills with disposable alternatives and continually discover new, innovative means to reduce energy consumption and recycle water. Our huge economies of scale allow laundries to use about two-thirds less water, energy and detergent than alternatives, such as washing at home, while hygienically cleaning textile products, improving disease control and reducing contamination.”