Posted on May 12, 2016
The science and effectiveness of the washing process has four controlling factors:
► Mechanical action
► Chemical type and concentration
Mechanical action is one of the most important variables affecting wash results. Within the laundry process, mechanical action is controlled by the loading practices used for a given size and type of washer.
► Loading varies with fabric and machine type
► Loading affects soil removal, fabric strength and excessive wrinkling
► Loading influences the costs for labor, chemicals, water and energy
Washer loading is stated as pounds of fabric per cubic foot of cylinder volume. Water and soil amounts vary in soiled fabric from almost zero to a large percentage of the fabric weight. To provide consistent standards, washer-loading factors are calculated on the weight of clean, dry fabric processed.
The established conventional loading factor over recent years has been between 5 and 6 pounds (clean dry weight) of cotton fabric per cubic foot of cylinder volume.
In the past, calculations for pounds of fabric per cubic foot were based on 100% cotton textiles. However, many of today's textiles contain lighter synthetic fibers, resulting in lighter weight fabrics.
Because of this, the same amount of weight of polyester blended or 100% polyester textiles should not be loaded for 100% cotton textiles.
Many washer manufacturers, in an effort to market their laundry equipment, "stamp" washing machines with a poundage-capacity figure for laundering 100% cotton. This figure is often misinterpreted, causing many operators to overload machines.
Overloading is not beneficial to good laundry performance it decreases as mechanical action. This happens because there is no room in the cylinder for the load to tumble. Detergents and chemicals cannot be distributed properly and the tightly packed textiles hamper dilution and lower soil removal, resulting in poor mechanical action and poor-quality laundering with an increase in stain count.. If a washer is overloaded, the items in the center of the basket remain dry and soiled.
Extra water levels are required for each operation and longer consecutive rinses may be needed to remove loose soil chemical supplies remaining in the load. If these supplementary steps are not employed, loads may need to be rewashed.
Laundry operators are encouraged to compare and load washing machines on the basis of cubic foot capacity. The volume - in cubic feet - of a washing cylinder can be computed from the following equation:
Underloading can also yield poor performance. With underloading you have agitation, but the water level is intended for a greater volume of goods. This "softens" the drop in the cylinder by having the load falling into the wash liquor instead of against the cylinder ribs. Excessive costs are incurred with underloading due to the chemical concentration being intended for a larger load leading to an increase in costs per pound of laundry.
Underloading a washer can be expensive, not only in terms of water, utilities, chemicals and manpower, but also in replacement of linen. Underloaded washers tend to damage linen by breaking down fibers. Chemical concentrations, temperatures and mechanical action that are greater than what a load dictates contribute to this.
Some fabrics, however, MUST be underloaded due to their bulk as compared to their weight. Garments that contain polyester blends are usually loaded at 3.5 to 4.5 pounds per cubic foot. This minimizes wrinkling and subsequently provides easier finishing.
A washing machine's loading figures should be based on equivalent clean, dry textile weight. Laundry operators looking to load machines on the basis of soiled weight must utilize a reliable method to convert clean, dry weight to soiled weight for each individual plant classification. The data collected is used to provide the correct soil-to-clean weight ratio to establish proper load sizes.Approximate figures for these ratios are given in Table 1 below:
The weight of textiles needed on a clean dry weight basis is multiplied by the ratio for that item listed in the table. The resulting figure represents the weight of soiled textiles that would give the required weight of clean textiles.
For example - if a washing machine has a rated capacity of 200 pounds of textiles on a clean weight basis, and a load consists of bib aprons, then:
► 200 pounds x 1.15 = 230 pounds
Therefore 230 pounds of soiled bib aprons would be the correct load. It should be noted that the figures stated in the table are purely guidelines.
The ratios differ depending upon individual plant conditions. Therefore, it is necessary that ratios be determined for each individual plant by weighing soiled loads and comparing the soiled weight to the clean weight for the same load after processing. If proper soil sorting is practiced, the ratio (soil weight/clean weight) could be consistent and need only be periodically determined.
Washer-extractor loading guidelines:
► Load the machine to 90% of its rated capacity
► Ensure all water levels are set correctly
► Carry out a visual check of the wash wheel. After the load is saturated with water, and the wheel is rotating clockwise, the linen should "break" from the 11am position to the 4pm position. This provides the necessary mechanical action for soil removal
With the correct water levels set, this method should permit the necessary flushing and rinsing of linen, as well as maximizing chemical performance.
The following steps (with example data) in Table 2 below, allow an operator to determine proper load size.
Operators can determine proper soil load weights by counting the number of clean dry items that would constitute the proper load weight. The ratios of soiled weight to clean weight referenced in Table 1 are only guidelines. Soil factor may vary depending upon the market and the customer.
Source – Recognized Industry Documentation.