CLEANROOM WASHERS
Sizing the Washer
Most cleanroom garments are 100% polyester or Gore-Tex™. These materials are very light compared to cotton and most other fabrics. For this reason it is important to use the “Loading Ratio” and volume (cubic feet or liters) of the washer to determine the machines production capability. The washer’s rating in pounds or kilograms is very misleading for cleanroom fabrics. An example using the Loading Ratio for a washer follows:
For a typical laundry the loading ratio is usually 10. For cleanrooms the typical loading ratio is 12 for ISO 5, 14 for ISO 4, and 16 for ISO 3. The loading of a 600 liter washer would be as follows:
It takes 40 to 60 minutes to wash a load depending on the number of wash and rinse cycles. This includes the load and unload time. A 600 liter (21 cu. ft.) washer will process 3,500 to 4,000 ISO 5 gowns per week based on a gown weighting 1 lb. each and 40 hours of production time.
Water Consumption:
Water Consumption is determined by multiplying the Load Size in kg (based on the above calculation) times the Water/Workware Ratio. Typical Water/Workware Ratios for a cleanroom washer process are as follows:
Water/Workware Ratio (liters/kg)
Pre-wash Cycle: 5
Wash Cycle: 4 or 5
Rinse Cycle: 5 or 6
For a model FA600BW using a Pre-wash, Wash and 2 Rinse cycles the water consumption would be:
Pre-wash cycle (Using a ratio of 5): 5 l/kg x 37 kg = 185 l. (50 gal)
Wash cycle (Using a ratio of 4): 4 l/kg x 37 kg = 150 l. (40 gal)
Rinse #1 (Using a ratio of 6): 6 l/kg x 37 kg = 220 l. (60 gal)
Rinse #2 (Using a ratio of 5): 5 l/kg x 37 kg = 185 l. (50 gal)
Total Water Consumption = 740 liters (200 gal)
A minimum of two cleanroom washer-extractors are recommended whenever possible. If one is down for service you still have an another machine for your critical production requirements.
As DI (Deionized) water is used for most ISO 3-5 laundries, cleanroom washers are made using 304L, 316L or 316Ti Stainless Steel for all wetted surfaces. DI water has a strong affinity for ions and these stainless steels will be trouble free.
For ISO 3 & 4 cleanroom laundries, electropolishing is recommended. Electropolishing enhances the surface by leveling the metal and making it very smooth and shinny. This also minimizes areas where particles, chemicals, and bacteria can be held. Electropolish also removes any free iron on the surface and passivates the stainless steel. All though electropolishing is expensive, it removes all the surface contaminates, passivates the surface to eliminate oxidation, and leaves a smooth surface (typically 16 RMS) that is easy to keep clean.
Pass Thru vs Front Loader Washer
A pass-thru washer allows the soiled gowns to be loaded on one side and unloaded on the clean side. They are also referred to as “side loaders.” No soiled gowns would be in the cleanroom. A front loader is loaded and unloaded from the front of the washer only. If a front loader is used it is necessary to bring soiled gowns into the cleanroom to be washed. This is common in ISO 6 and higher laundries. The laundry cart is covered while being transported into the cleanroon and to the washer.
Soft Mount Washer
A soft mount machine is easier to install as it does not require a thick, reinforced, and isolated concrete pad. Most soft mount washers can be bolted to a 6 inch concrete floor. Small washers can be installed on reinforced wooden floors. A soft mount washer is required for installations where the washer is not installed on the lowest (ground) level.
On large split pocket washer- extractors it is recommended they be sized so one pocket would go to one dryer and the other pocket would go to the other dryer. For example, one 22 cu ft pocket of a 44 cu ft split pocket washer would go to one 50 cu ft clean room dryer and gowns from the other pocket would go to the other dryer.
The first Cleanroom Laundries used a Pass-Thru washer designed and built for hospitals. Now washers are available that truly meet the needs of a Cleanroom Laundry. Special stainless steels and electropolishing are covered above. Other features to consider are:
Dimpled Cylinder Perforations: The cylinder perforations are dimpled (embossed) to the outside so the gowns never contact the sharp edges of the cylinder perforations. This reduces chafing and wear of the fabric and increases the life of the garment.
Variable Speed Drive: Most modern cleanroom washers allow the wash and extract speed to be programmed for maximum g’s without damaging the fibers of the fabric. It is important to adjust the extract speed for the item being washed and the type of material the gown is made from.
Bearing Lubrication Relief: The main bearings require lubrication on a regular basis. The biggest problem occurs when too much lubrication is added. If excess pressure is built up in the bearing housing, grease can be forced out of the seals in the bearing and past the shaft seal into the wash. This contaminates the stainless steel inside the washer. The result is expensive and causes down time. Bearing housings for a cleanroom washer should be designed so any excess lubrication will be released to the outside of the bearing housing.
Auto Weighting: It would be nice if each load was the same weight, but small loads and some large loads are common. An Automatic Weighting System weighs as the washer is being loaded. This make it simple to get each compartment loaded equally. The control will then add more or less water depending on the active weight of the load. It will also increase or decrease the amount of chemical based on the amount of water used. Now you have the correct amount of water and chemical for every load being washed.
