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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
OF NEW DRYERS
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.
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.
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.
is the best day to assess your drying processes and evaluate your dryers. If new equipment is needed, you’re certain
to get terrific pricing, quick delivery and excellent support. Do your homework and reap the benefits of efficient drying.