Filtration in the Dry Cleaning Industry

Written by Barry Victor, Founder of PROS Parts

Having filters that are in good condition will make a difference on your cleaning quality.

If you have ever looked at a dry cleaning machine closely, you can see that they are quite complicated pieces of equipment.  Dry cleaning machinery is basically the same as laundry equipment with one major difference.  The fluid in a dry cleaning machine is not water but rather one of many solvents.  Because the equipment uses a solvent, it is necessary for practical and environmental reasons to recycle it within the machine and that requires quite a bit of process machinery.

Another major difference between laundry and dry cleaning equipment is that the entire process including washing and drying takes place within the dry cleaning machine while in a laundry operation the textiles are transferred from the washer to the dryer which are two separate machines.

One of the systems that allow a dry cleaning machine to be a closed loop is the solvent filtration system.  Over the years, the filtration process has evolved quite a bit but the same basic requirement has remained the same.  As the machine operates, solid particulate is released from the garments being cleaned as well as some soluble substances such as oils and dyes.

In the very early years of dry cleaning, the filtration system utilized a braided metal tube covered in a filtering agent powder known as diatomaceous earth along with powdered activated carbon. The powder would capture the solid particulates and the carbon would adsorb the fugitive dyes.

As operators started looking for a simpler less messy method, the second generation systems came into widespread use.  These second generation systems incorporated cartridge filters which performed the same function as the earlier systems and saved time and required less complicated machinery.

The third generation filtration system widely used today called spin filters incorporate a filter made up of many discs with a very fine nylon fabric that is used as the filter media along with a small set of cartridge filters containing granular activated carbon to remove the fugitive dyes from the solvent.

Cartridge Filter Types

Some dry cleaners continue to use cartridge filtration systems with an additional bag type  pre-filter  to remove the larger particles and lint to extend the life of the paper in the cartridges.

Cartridge filters generally come in three different form factors and within these many types of filtration media.   One cartridge form factor is known in the industry as “Standard Format” or Standard Size.  These measure about 7-3/4” in diameter and are 14-1/4” long cylinders.

The second form factor is the Large Format Split.  These measure 13-1/4” in diameter and are 9” long cylinders.   Finally the Large Format Full is basically two of the splits in one measuring 13-1/4” in diameter and 18” long.  Cartridge filters also come in a variety of filter media types in each of the above form factors.

All Carbon Filters

The most common type of cartridge is the all carbon filter which as the name implies is a cartridge with only granular activated carbon.  The purpose of the carbon is to quickly remove any fugitive dyes that have bled from the garments before the dye can redeposit on other garments. The manufacturers of these cartridges pay special attention to the type of carbon used to make sure it allows ideal solvent flow and a large capacity to store the removed dyes.  They also pay attention to the integrity of the carbon granules to make sure no carbon is released into the filtration system.  Finally, the packaging of the carbon is done with a method to assure minimal settling during shipment and use so no solvent can bypass the carbon.

Carbon Core Filters

The carbon core type of cartridge filter is more commonly used in all cartridge systems that do not use the spin disc filter.  In this filter there is a small core of carbon to help remove dyes as described above that is surrounded by a pleated paper filter to remove the insoluble particles and lint.  Close attention is paid to the quality of the paper used to make sure it is capable of filtering very small particles.  Each end of the pleated paper cylinder is sealed in a special adhesive to prevent solvent from bypassing the paper.

All Clay Filters

Like All Carbon, the the all clay filter uses activated clay to absorb oily contaminants and excess moisture from the solvent stream.  These types of cartridges are often used in machines which either do not have a distillation system for removing soluble contaminants or where minimal distillation is taking place.

Combination Clay and Carbon Filters

These cartridges use a mixture of clay and carbon to provide for the removal of fugitive dyes as well as oily contaminants and excess moisture.

Refillable Cartridges

The refillable cartridge filters are designed to allow the operator to buy bulk activated carbon and fill the housing.  Once the carbon has come to the end of its useful life, it can be removed from the housing and it can be filled with a fresh charge of carbon. The ability to re-use the housing saves not only money but also reduces the amount of waste generated.

Pre-Filters

As mentioned earlier, many filtration systems utilize a pre-filter that contains a small nylon bag with a very fine mesh.  The purpose of this filter is to remove the larger particulate and lint that would otherwise quickly plug the paper filters downstream and reduce their life span.  The pre-filter is designed to be easy to clean by removing the top and emptying the nylon bag which is reusable.

Having the right filter and one that is in good working order will make a difference on how clean you get your laundry.  PROS Parts can help answer questions and help you with your filter needs.  Visit our website for more information or you can always contact us directly.

About Barry Victor

Barry founded PROS Parts in the spring of 1988. Before starting PROS, Barry worked in the sales and engineering departments of Vic Manufacturing, one of the largest manufacturers of dry cleaning equipment in the U.S. At Vic, Barry launched a parts sales division that supported dry cleaning equipment imported from Italy and Germany. In its early years, PROS manufactured dry cleaning machinery and then evolved into an industrial and commercial laundry equipment and dry cleaning operations parts supplier. Barry lives in Eden Prairie, MN with his wife. He has two sons, a step son, a step daughter and his dog, Sora. 

Barry can be reached at 763-231-7379 or barryv@prosparts.com.