Tray and Rackwash

Washing machines come in many shapes and sizes and are generally built for the cleaning of a specific size and type of item. Washing machines should only be used for the original purpose they were intended.

Ideally pre-washing should be carried out using warm water from a separate tank to avoid ‘bake on’ of protein at the higher temperature washing stages.
The water temperature must be suitable for the type of soil to be removed but in general 30-60(C. (Can be heated by overflow from detergent wash or rinse tanks).

Detergent Wash
A detergent wash should be carried out from a separate tank using a low foaming detergent appropriate to the equipment being cleaned and nature of soiling. Caustic based detergents are usually the most efficient and cost effective types of detergents used although chlorinated and neutral products are sometime used. A chlorinated detergent must not be used above 55(C as it will cause pitting corrosion on stainless steel. A neutral or inhibited detergent may be employed for the cleaning of sensitive items, such as aluminium trays.

The short contact time with detergent and the relatively low impact energies of the wash nozzles means that to clean effectively high chemical energies are required. In most situations a high alkaline low foam detergent at 0.25% to 1% v/v is used at 55 to 75ºC.

Detergents need to be capable of coping with the water hardness otherwise scale drop out will occur. A routine water hardness test should be carried out. This will ensure that the risk of scale drop out is reduced. It may also prove beneficial in hard water areas to soften the water supply by having an on-site water softening system.

Rinse
Rinsing should be carried out with water fed either directly from a heat exchanger or a separate enclosed non-recirculating tank. Where rinsing is not followed by a final disinfection stage, the rinse water should be maintained at a minimum of 82(C. Attention must be paid in hard water areas, as there could be a significant problem of scale drop out requiring regular de-scaling.

Where the rinse water temperature is below 82(C, this should ideally be followed by a disinfection stage; particularly in a high care environment. The disinfectant used is generally a low foam non-oxidising disinfectant.