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DRYING EFFICIENCY
If you’re like me, the evening news is no longer a welcome form of relaxation. While we are hearing good news on Wall Street, the unemployement rate is a big part of what's keep our business slow. With this situation, many of us are taking a “wait and see” approach into 2012. To the contrary, can we afford to sit back and watch as the economic world rights itself? During this slow period, I encourage you to spend some extra time to fine-tune your processes, so your operation will be as efficient as possible, now and in the future. I suggest that you begin with your drying procedures; an area of acute importance to your bottom line.
LOAD SIZE
Drying efficiency does not begin at the dryer, but at the washer/extractor. It’s typical for a laundry operator to load washers “by eye”, with no regard to the actual load weight. This loading method may yield very light loads for some products and extremely heavy loads for others. It may also produce inconsistent weights for the same product. When these clean loads of vacillating mass move to the dryer, prepare to pay for inefficiency.
While load weight is important in the wash process to determine proper chemical and water needs, it’s even more consequential at the dryer. Your dryer operator must determine the amount of heat time or the correct drying formula to use to produce the desired finish. Passing-off varying load weights to the dryer operator limits his or her ability to make good cycle time decisions.
THE largest inefficiency in the drying process is the restart required after it’s revealed that a completed load is too damp. Once you cool down the load and open the door to hand-test for dampness, it now takes considerable energy (and time) to reheat the load to the temperature set point and complete the process. Large loads take longer to dry, not solely because there’s more water in the load, but also thanks to the fact that most dryers don’t perform well when overloaded, which may stifle airflow and limit air-to-goods access.
A shift in load weight to the low side also creates inefficiency at the dryer. Small loads will be dry long before the heat cycle ends. Therefore, more utilities are used than what is required. Even if you do reduce the heat time, a small load in a large dryer will use significantly more energy than necessary due to bypass of air around the products.
If you can’t weigh every load, conduct an evaluation. Be sure that your operators, who are loading washers “by eye”, can discern a “full load” of sheets, blankets, gowns, etc. Perform weight testing on the dry side of your dryer to see if load weights are accurate and if they match the rated capacity of your equipment. The more proficient your laundry is at providing similar load weights, by product, the more efficient your drying process will become.
TEMPERATURE SETTINGS
With load sizes more defined, it’s now time to determine the temperatures to employ for each of the materials processed. This may seem unnecessary, since your laundry has been drying products for years and your operators are very experienced. However, outside influences may have persuaded your operators to modify the dryer setups in opposition to the original approach.
Dryer manufacturers, who wish to demonstrate drying productivity and efficiency, will most likely encourage setting the highest possible temperatures without damage or discoloration. High heat air holds more moisture and helps to reduce cycle times.
Garment or linen suppliers may push for lower temperatures to extend the product life. Their focus is to lengthen the number of uses before product replacement, respecting the need to reduce material wear, shrinkage and wrinkling.
An analysis should be conducted to ascertain the best inlet and outlet temperature set points for each material being processed. Each laundry must determine the appropriate temperature settings that will yield acceptable dryer performance, along with agreeable product quality and longevity.
The following graph shows the production of a 250-lb. capacity dryer when the temperatures are modified and when the load size is adjusted. It demonstrates the benefits of high heat and full loads. 
HEAT CYCLE TERMINATION
During your quest for proper load sizing and correct temperatures, you must also establish the length of each heat cycle. The dryer control can’t help, not without a lot of input from you. It all goes back to trial and error.
Even if using high-end controls with humidity sensors, you need to enter the moisture level number to be achieved. You must perform tests with each product. Once you know the humidity number that gives you the suitable dryness for that product, that’s the number you enter into your formula.
For most of us using time and temperature, time tests must be performed. The goal is to limit the heat cycle time as much as possible without ever under drying the load.
Here’s where a good microprocessor control will give great advantage. While monitoring the outlet temperature, the microprocessor’s focus is on the inlet side, making heat adjustments based on the inlet temperature. Once the outlet set point is reached (outlet temperature being a close equal to the temperature of the goods inside), the inlet temperature is allowed to drop off in order to prevent an over-heat condition and to reduce fuel usage. The focus remains on the outlet temperature until the end of the heat cycle.
In many cases, the formula may be named, by product, to eliminate guesswork by the dryer operator. Some of these controls utilize an algorithm to evaluate the formula history and more precisely define the correct time for heat cycle termination.
NOTE: If you’re using both high-extract and lower extract washer/extractors in your laundry, a complete new set of formulas or heat times should be created to handle the high or low extraction levels for each item.
The combination of accurate load sizing, temperature setup and cycle termination will give you the best from your dryers. After you’ve done all this work, become an advocate for repeatability. Perform quarterly tests to confirm that load sizes haven’t changed and that formulas or cycle times remain accurate. Proper and timely maintenance is also important to sustain good dryer performance.
FUEL USAGE
Shortening dry times also reduces fuel usage. The amount of fuel used per cycle is key, yet this factor is almost always a mystery to the launderer.
An unknown author once wrote: “What gets measured becomes important.” I’d love to be able to suggest that you use your high-end dryer control to measure the fuel usage. Yet, dryer manufacturers don’t offer gas metering as a selectable feature.
It’s up to you to install a meter or alternate device to calculate the amount of fuel used per cycle or per pound of water removed. This is the only good way to substantiate efficiency over time or to help head-off maintenance issues before they begin costing you money. It may also help to demonstrate the need for newer more efficient equipment.
Earlier in this article, I suggested a balance between dryer performance and product longevity. Metering your fuel usage is a very good tool to aid in making this judgment.
The following graph shows the efficiency of a 250-lb. capacity dryer when the temperatures are modified and when the load size is adjusted. Similar to the production graph, this demonstrates the benefits of high heat and full loads. 
ADVANTAGES OF NEW DRYERS
Typical commercial and industrial dryers use a gas-fired burner for heat, a large air blower to move air through the load and a tumbling basket for suitable air-to-goods access. Many newer designs include a gas system that fluctuates the inlet gas to limit the amount of fuel used per cycle. This system is controlled by a microprocessor or PLC, which precisely modulates the incoming fuel through modern programming techniques.
A forced-air burner is the most efficient style; where by, the burner has it’s own combustion air blower. This air is forced into a combustion chamber under pressure, yielding a more efficient burn and higher air temperatures. With high inlet temperatures, the dryer will spend less time to attain the temperature set point, where drying is most efficient.
If you are working with dryers that use timers and an atmospheric burner (air passing over a flame), you may want to consider an update to a more sophisticated design. The fuel savings, alone, can pay for the cost of new equipment within 2-4 years, and the production time savings can be reduced as much as 50%, further shrinking your overall payback time.
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