Pulsed Spray Cleaning

The focus of this research project is on spray or water jet cleaning of food equipment. Spray cleaning systems are used for tank cleaning with a few cleaning nozzles or for cleaning of machinery with complex CIP-systems with up to hundred cleaning nozzles e.g. in aseptic filling machines.

Low pressure static cleaning nozzles apply only the cleaning solution to the surfaces without sufficient mechanical cleaning energy. The cleaning of the surface is realized by the falling film. A continuous falling film of cleaning fluid develops a base film on the surface so that the impingement energy of the spray is reduced. The removal is then basically driven by diffusion i.e. by the reaction between soil and cleaning fluid. The positive effect of pulsed spray is mentioned in a few publications. By pulsing of the spray or operation in impulse-pause mode a higher amount of mechanical energy is transferred to the soil. Working with interrupts will break up the continuous film and a second phase boundary (soil – air) will increase the mechanical part of soil removal. Preliminary tests came to the conclusion that a reduction of cleaning fluid in relation to continuous spray is possible by using pulsed spray.

Certainly the basic active principles are not known at present. The most efficient frequency and pulse factor have to be determined. The influences of the soil characteristics have also to be examined.

The analysis will be done at the test rigs of the Fraunhofer AVV. Using a well-defined soiling method the effects of pulsed spray in relation to continuous spray can be investigated by measuring the required time for cleaning.