- Created on Wednesday, 02 April 2003 16:16
- Written by Jack J. Reiff president, Wet-Tech
Tunnel washers began production in the mid 1970's. Initially, they were designed as a tube where the linen was fed in a rope-like fashion. Linen passed through several treatment baths accomplishing the wash process. Water was fed in a counter flow arrangement to the linen and chemicals were added through a hollow tube with a cup on the dip end.
The feed water was interrupted at certain locations so that soil could be drained off or water could be introduced in other areas to optimize the wash, bleach, rinse and finishing of the linen. At the finishing end of the tunnel there was a large inner tube configuration, rotating, pressing and pulling the linen feed line through the Poensgen Tunnel, extracting water so linen could be collected for finishing.
The next phase of tunnels was the Voss Archemedia, bottom transfer tunnel. These units had chemical supply tanks with doser's to get the chemicals, under pressure in to the washer. The chemicals were injected in to a central hub of several supply tubes and ran the length of the tunnel to an opening at the proper location for that chemical use. The chemical volume could be adjusted at the doser as well as the strength of the chemical. The Voss Archemedia washer had a control card to regulate formula.
Equipment design matured with technology. The basic counter flow remained, but the wash transfer concepts changed. The Archemedia screw, bottom transfer led to the top transfer and other designs. What is lacking now is the proper application of ozone into the tunnel washer process to improve on the efficiency, performance and quality of output.
OZONE IN WASHING
Ozone can be utilized in a wash formula to reduce - not eliminate - chemical applications. An oxidizer, ozone consumes organic material along with petroleum hydrocarbons, converting this soil along with others into carbon dioxide, other non-organic oxides, O2 and water. In attacking this soil load it frees up the soil suspension characteristics of wash cycle detergents. Rinsing of the soil load and cleansing of the detergents is accomplished without fresh water, reducing wash cycle requirements. Ozone reduces wash temperatures in the pre-wash and the wash cycles, reducing operation times and it works as an anti-chlor in the rinse cycles reducing the rinse or transfer time.
Ozone also enhances the final bath by contributing to the sanitizing, disinfecting and anti-chlor requirements. Bacteria, viruses, mold, fungi and algae are dealt with more effectively than other biocides such as chlorine. The bacteria and viruses are destroyed, preventing reactivation or the development of a new resistant strain of the microorganism. This sanitizing ability of ozone is 3000 times faster and 150 percent stronger than chlorine.
It is important to remember that ozone is highly corrosive and is an aggressive oxidizer that attacks most materials. It is therefore important to know the levels of ozone being used, the concentration, the life cycle of the ozone and the make up of the air source to avoid worrisome chemical byproducts.
OZONE USAGE IN TUNNELS
When we develop a wash procedure for cleaning soiled fabrics in a tunnel washer we have to consider the operating conditions of the tunnel which operates on the main water flow coming through the rinse chambers. Most tunnel washers are broken into operation zones -- pre-wash area, wash area, bleach area, rinse area and a final treatment area. The uniqueness of the counter flow system in making full use of the water starts in the rinse zone where fresh water is introduced. This water is usually drained into a transfer area where the water is divided to the bleach zone and the pre-wash area. In the bleach zone it is similar to bleaching in the clear due to the counter flow characteristics of the wash.
The pre-wash area is usually where rinsing and chemistry starts to remove fabric soil. Steam is usually injected to get the temperature up for soil removal. Although dirty water drains from this section a good portion of the water is transferred with the linen into the next compartment where washing begins. Chemicals are again added and temperatures are increased for soil removal. The load is transferred through several wash pockets and several bleach pockets. After rinsing the load is transferred to the treatment zone where sour, bacteria treatment, starch or other desired finishing agents can be added.
APPLYING OZONE IN A TUNNEL WASHER
The application of ozone in tunnel washers raises many questions and challenges that laundry managers should be aware of and discuss with their ozone provider.
- What concentration of ozone is to be used?
- How long will that concentration be maintained in the wash cycle?
- What is the make up of the feed gas?
- At what location or locations will the ozone be infused in to the wash cycle?
- What can be accomplished at reduced washing temperatures?
- What can be accomplished at washing with reduced chemistry?
- What effect can the use of ozone have on reducing transfer time?
- Will a change in transfer time help to reduce water consumption?
- Will the ozone carry down to my bleach bath making it less effective in stain removal?
- What is the footprint of the ozone system?
- If the ozone system goes down can I easily switch back to the original wash operation?
- Can the ozone be introduced to sanitize the processed linen?
Some ozone companies that use a supply tank of water that is infused with a high concentration of water will inject ozone in to the wash machine at the rinse water inlets. To maintain a fairly decent level of ozone for this wash process the water must be cold and the ozone concentration should be high.
This is not a recommended process since ozone oxidizes brass, copper, steel, iron and plastic materials. Using it on inlet sources of the equipment can deteriorate valves, seals and fittings. Additionally, due to ozone’s short life, the ozone would then be solely consumed in the rinse cycle and not be of value in other areas of the wash.
However, if it is a high concentration of ozone, it can be carried forward for washing. As the water carries forward, the temperature is increased due to the bleach and wash process so the ozone is depleted here during the rinse cycle and very little gets to the soiled area. In most cases, this rinse water drains to a transfer tank where the water is redirected to other compartments of the tunnel. Some would go to the bleach bath and transfer down through the wash. In other cases some would go to the wash inlet and bleach inlet while also feeding the pre-wash compartments. The purpose is to maximize the use and reuse of the water supply and see how the ozone can enhance the wash operation.
Making full use of the synergy that ozone introduces in to the wash chemistry is an important step in maximizing your benefits from ozone chemistry.
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