Is my washer-extractor’s loading capacity set in stone? I mean, can I fudge a little and load heavier to get more work through when we’re under the gun? What’ll happen to my wash quality if I overload (or underload) a machine? Is overloading worse than underloading, or vice versa?CHEMICALS SUPPLY: Tom Storm is vice president of technical development for WSI, a national company specializing in providing washroom and wastewater chemicals plus accompanying service to commercial laundries. A chemical engineer, Tom has 38 years of laundry industry experience.
There is another question I want to answer first: What’s the correct loading capacity of a washer-extractor? The answer is fairly complex and is not usually the published weight listed for a machine.
The machine manufacturers carefully define that as the weight to load clean, dry cotton at a specific loading ratio usually assumed to be 5.25 pounds per cubic foot. If all those conditions fit, then load to that amount. However, those conditions don’t apply most of the time.
The weight to load is dependent on the washing cylinder volume, the machine configuration, the type and weave of fabric, the amount of soil and the cleaning/finishing situation involved.
The washing cylinder volume in cubic feet is calculated by the following equation where d equals cylinder diameter and z equals cylinder depth in inches:
V = d2z/2200
The next step is to decide on the proper loading ratio, which is in the units of pounds per cubic foot. This value depends on the machine configuration, and is the most dependent on the cylinder diameter and rib configuration.
For example, the often-used value of 5.25 pounds per cubic foot is good for a long, open-pocket cylinder no longer than 48 feet in diameter. Split- and Y-pocket machines will have lower loading factors while the large open-pocket machines can have loading factors near 7 pounds per cubic foot.
Since a washer cylinder really should be loaded by volume instead of weight, a fabric factor must be used to take into account that different types of fabric will have a different weight per cubic foot. Synthetics weigh less than cotton, so a factor of 0.8 is not unusual for polyester cotton or spun poly. Mats are heavy, so a fabric factor of 1.25 is not unusual. Also, the fabric weave has an effect. A poly-cotton shirt would have a fabric factor around 0.8, but industrial pants of the same material will have a higher factor.
Next, the level of soil must be considered. Soil is defined for loading purposes as anything that isn’t part of the basic fabric and initial finish. Consequently, moisture is considered soil under this definition.
Soil factors can range from 1.0 for high-quality, frequently changed hotel sheets to 1.5 for heavily soiled shop towels. Don’t forget that pool towels can contain a lot of water.
Soil factors can be assumed based on experience; however, measuring actual values is always a good idea. This can be done easily by weighing a load before washing and again after washing and drying. The soil factor is simply the ratio of the former compared to the latter.
Finally, the washing/finishing situation must be taken into consideration. If the load is for stain treatment, reducing the load size by 10-30% will give more mechanical agitation and a higher chemical-to-fabric ratio. If you finish garments through a steam tunnel, a 20% reduction will allow the fabrics to flex more, making wrinkle removal easier and more complete.
To illustrate how to calculate the soil weight to load a machine, let’s assume we have a large, open-pocket washer-extractor (V equals 75 cubic feet) that is to process a load of shop towels. The loading ratio is 6.6 pounds per cubic foot, the fabric factor is 1.0, the soil factor is 1.46, and it’s a normal finishing operation by drying. The soil weight to load this machine is:
75 ft3 X 6.6 lbs/ft3 X 1.0 X 1.46 = 723 pounds
Your chemical representative can help to establish the proper soil weight loading for each machine and each classification.
To answer the initial question, you should load to the proper soil weight. You should neither underload nor overload. If you take the time to determine the proper soil weights, you’ll find that you have maximized production and there will be little need to overload to meet production needs. Always resist the temptation to overload.
Overloading will result in poor soil and stain removal, and rewashing will cost you the production you gained by overloading and more. Your costs in energy and chemicals will increase.
You can get away with under-loading on an infrequent basis. There’s always the small amount of items at the end of a lot, or the carryover of items from a load because you refuse to overload. Quality won’t suffer, but fabric life as well as chemical and energy costs will.
If you find yourself doing a lot of underloading, consider going to a ratiometric program in which the water level, chemistry and even rotation speed are changed for partial loads.COMMERCIAL LAUNDERING: Richard Warren is the general manager of Linen King of Central Arkansas, a commercial laundry that provides COG, rental and linen distribution services for healthcare clients. His experience also includes OPL and industrial laundering, linen supply, and leather/fur cleaning.
Washer manufacturers use a formula to determine the recommended capacity of a particular machine. This formula includes the size of basket, distance of the fall of the goods, number of baffles, rotation speed and, I’m sure, some other factors. The pound rating has relatively little connection to wear and tear on the bearings, or the drag on the motors, which is a common misconception.
If you’re going to adjust your load size, you must also adjust the water levels, chemistry, length of cycle and temperatures.
What will happen to wash quality? Simply stated, it will degrade. How much it degrades depends on the amount of deviation from the manufacturer’s recommended load size. As the load weight in a machine changes, so does the mechanical action. Have you ever had a sheet come to the ironer still folded and soiled? This is caused by insufficient mechanical action in the washing process. We unfold the sheets in the sorting area so they may be washed properly.
If your machines are overloaded, the goods just soak. If underloaded, there’s little for the goods to rub against. After you factor in the additional rewash that adjusted loading causes, you may be surprised to see that your clean, dry weight isn’t as high as you’d hoped.
And let’s not forget the drying process. If your dryers are automatic, they may need to be tweaked in order to vaporize the additional gallons of water left by the overloading.
This load adjustment is like using less detergent because your supply order hasn’t arrived. Making the loads larger because you have a lot of work to do just isn’t a good idea. Can you get away with it? Sure … for a short period of time.