WHAT ABOUT THE WHAT ABOUT THE DRYERS?DRYERS?

By Dave SmithBy Dave Smith

Company Q just purchased a new tunnel system. They went through all of the normal supplier ‘dog and pony shows’, checked references to confirm water usage, wash quality, data reporting abilities and vendor support. They reviewed the proposed layouts, studied workflow, learned about counter flow, bottom-vs-top transfer, etc, etc, etc.

Now in operation, Company Q’s upper management is not happy. The natural gas usage has increased, significantly, and the system is bottlenecking, occasionally, on the dry side. Maintenance seems to have no ideas. Production is stumped. A review is made of the purchase process and one question keeps coming up… “What about the dryers?”

Dryers are a fundamental part of a laundry, large or Dryers are a fundamental part of a laundry, large or small. They use significant utilities dollars and small. They use significant utilities dollars and demand proper care to maintain efficient performance demand proper care to maintain efficient performance and to prevent component damage and fires. They and to prevent component damage and fires. They should be evaluated as thoroughly as you would the should be evaluated as thoroughly as you would the washer. washer.

It’s something that I’ve dealt with as a new equipment It’s something that I’ve dealt with as a new equipment supplier and, more recently, as a supplier of used supplier and, more recently, as a supplier of used equipment. Many people are unaware of the ups and equipment. Many people are unaware of the ups and downs related to laundry drying. Buyers should downs related to laundry drying. Buyers should perfect their dryer knowledge, so they know what to perfect their dryer knowledge, so they know what to look for and so they’ll understand what information to look for and so they’ll understand what information to ask for when making a decision.ask for when making a decision.

Dryer basics can be broken down into four essential Dryer basics can be broken down into four essential categories; Heat, Tumble, Airflow and Control. A good categories; Heat, Tumble, Airflow and Control. A good heat source is crucial for short heat cycles and for heat source is crucial for short heat cycles and for efficient drying. Natural gas is most often used in the efficient drying. Natural gas is most often used in the U.S. to provide these important criteria. 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 chamberForced-air burners mix air and gas inside a chamberunder pressure. This provides a very efficient andunder pressure. This provides a very efficient andhigh-temperature burn, which brings the load tohigh-temperature burn, which brings the load totemperature set point more quickly.temperature set point more quickly.

Today’s most efficient dryers not only possess a Today’s most efficient dryers not only possess a forced-air gas burner, but they also have the ability forced-air gas burner, but they also have the ability to modulate the fuel input through use of a to modulate the fuel input through use of a modulating gas valve. As the temperature set point modulating gas valve. As the temperature set point is reached, these dryers can adjust the gas usage by is reached, these dryers can adjust the gas usage by slowing the fuel input.slowing the fuel input.

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 As the products dry, lighter goods may cling to the basket sides and rotate around and around. Some basket sides and rotate around and around. Some dryers permit a change in basket rotation speed to dryers permit a change in basket rotation speed to assist with proper material drop for varying load assist with proper material drop for varying load types.types.

A forceful airflow is now required in order to pull the A forceful airflow is now required in order to pull the moisture from the load. Dryer manufacturers use moisture from the load. Dryer manufacturers use varying ways to introduce air into the products… varying ways to introduce air into the products… from the top-out the bottom, from the bottom-out from the top-out the bottom, from the bottom-out the top, from the sides-out the bottom, from the the top, from the sides-out the bottom, from the rear-out the front, (you get the picture). Who’s to rear-out the front, (you get the picture). Who’s to say which way is best. It all comes down to overall say which way is best. It all comes down to overall performance.performance.

With a quality heat source, tumble action and airflow, With a quality heat source, tumble action and airflow, there must also be control over these functions. there must also be control over these functions. Microprocessors and PLC’s permit precise control Microprocessors and PLC’s permit precise control over the burner modulation, formula set-ups, airflow over the burner modulation, formula set-ups, airflow and basket rotation speeds, along with many other and basket rotation speeds, along with many other features. Even smaller dryer designs now offer built-features. Even smaller dryer designs now offer built-in controls to help determine the suitable time for in controls to help determine the suitable time for heat termination.heat termination.

Ask questions of your potential supplier. What dryer Ask questions of your potential supplier. What dryer processes are programmable and what are not? processes are programmable and what are not? How many programmable formulas are available? How many programmable formulas are available? How does the dryer determine heat cycle How does the dryer determine heat cycle termination? Is the burner system a simple Hi / Low termination? Is the burner system a simple Hi / Low fire system, or does the dryer modulate the gas fire system, or does the dryer modulate the gas input? Is the burner a forced-air type or an input? Is the burner a forced-air type or an atmospheric design? Does the formula have control atmospheric design? Does the formula have control over basket rotation speeds or basket reversing? over basket rotation speeds or basket reversing? How is good airflow achieved? How is good airflow achieved?

Overall dryer performance is the bottom line, Overall dryer performance is the bottom line, but getting answers is not easy. The problem but getting answers is not easy. The problem is that there are so many variables for drying. is that there are so many variables for drying. Material types, extraction levels and load sizes Material types, extraction levels and load sizes all affect the end results. An industry standard all affect the end results. An industry standard is needed, here.is needed, here.

Dryer performance can best be shown through Dryer performance can best be shown through production and efficiency results.production and efficiency results.

ProductionProduction = Pounds of H2O Removed per Minute = Pounds of H2O Removed per Minute

EfficiencyEfficiency = BTU’s Used per Pound of H2O Removed = BTU’s Used per Pound of H2O Removed

Ask your equipment provider to supply Ask your equipment provider to supply production and efficiency numbers for certain production and efficiency numbers for certain products when washed in your type of washer products when washed in your type of washer (low-speed washer/extractor, high-speed (low-speed washer/extractor, high-speed washer/extractor or tunnel & press). Use this washer/extractor or tunnel & press). Use this information for comparison purposes in your information for comparison purposes in your overall wash isle evaluation. Do the numbers overall wash isle evaluation. Do the numbers equate when reviewing the number of dryers equate when reviewing the number of dryers suggested by this supplier for your operation?suggested by this supplier for your operation?

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.

What if there’s a fire? Most industrial dryers have a What if there’s a fire? Most industrial dryers have a built-in water spray system that is turned on when an built-in water spray system that is turned on when an over heat condition in found. Ask about this system. over heat condition in found. Ask about this system. What happens if the electricity goes out… will their What happens if the electricity goes out… will their system continue to operate? Should the dryer’s system continue to operate? Should the dryer’s emergency stop button be pushed to stop the basket emergency stop button be pushed to stop the basket rotation and gas flow? rotation and gas flow?

What maintenance expertise is the supplier requiring What maintenance expertise is the supplier requiring from your company? A higher level of knowledge may from your company? A higher level of knowledge may be required to deal with the new controls and other be required to deal with the new controls and other high-end components. Temperature probes, humidity high-end components. Temperature probes, humidity sensors and infrared sensors must be tested and sensors and infrared sensors must be tested and calibrated, as needed. calibrated, as needed.

Metering of dryers is a good idea. Are your Metering of dryers is a good idea. Are your people capable of performing periodic checks people capable of performing periodic checks that should be made to compare performance that should be made to compare performance results with a standard? This method is a results with a standard? This method is a good way to detect problems before they cost good way to detect problems before they cost you time and energy dollars.you time and energy dollars.

What about safety? Are your people required What about safety? Are your people required to move about in areas where automation is to move about in areas where automation is happening? Are the manuals adequate in happening? Are the manuals adequate in explaining how to maintain the equipment explaining how to maintain the equipment safely, especially in hazardous areas where safely, especially in hazardous areas where your people may be exposed to natural gas, your people may be exposed to natural gas, electricity and moving components? electricity and moving components?

If you’re not in an automated environment, thinkAbout load handling issues. Soiled 250-lb. washerloads turn into wet clean 375-lb. dryer loads, evenafter high extraction. Find beneficial solutions foryour employees who must handle these weights.

Each of these issues should be reviewedEach of these issues should be reviewedprior to a dryer purchase.prior to a dryer purchase.

With a good understanding of dryer basicsWith a good understanding of dryer basicsyou will be better prepared to make a properyou will be better prepared to make a properequipment evaluation for your company. equipment evaluation for your company. When asked “What about the dryers?”, youWhen asked “What about the dryers?”, youwill have the answers.will have the answers.

For more information concerning dryerFor more information concerning dryerbasics and helpful ideas, please visit basics and helpful ideas, please visit

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