Effects Of Mechanical Cleaning Research Articles

A method for measuring the cleaning effect of flushing disinfectors.

A method is presented with which the mechanical cleaning effect of flushing disinfectors can be estimated independently of the thermal disinfecting effect of the hot flushing water. This makes it possible to specify the demands to be placed on the disinfecting effect of flushing with water of 85 degrees C or more. Bacillus stearothermophilus spores suspended in faeces were used as indicators because of their non-sensitivity to the hot-water temperature. Their elimination by flushing could thus be attributed to the mechanical effect of the water and not to the disinfecting effect of the temperature. A simple bacteriological technique was used, and the elimination factor (EF) was calculated as the ratio of the number of micro-organisms in the contamination before and after flushing. By using flushing water below 50 degrees C for 130 s the EF on a bedpan was about 10(4)-10(6). The effect of flushing with water of the same temperature for only half that time was somewhat weaker and when the temperature was raised to 85 degrees C after half the flushing time the effect was somewhat stronger. It can be presumed that the conventional disinfecting phase with hot (85 degrees C) water for about 45 s in the commonly used flushing units could be substantially shortened and the costs of their use thereby reduced.

MECHANICAL CLEANING EFFECT AND PRESSURE DROP OF AIR‐WATER‐FLOW IN HORIZONTAL GLASS TUBES (VACUUM DAIRY PIPELINES)

ABSTRACTMathematical models are presented which make it possible to calculate pressure drop and mechanical cleaning effect for plant design of vacuum dairy milking pipes. Experimentally, air‐water mixtures were sent through a test plant, consisting of glass pipes 0.034 m in diameter and 60 m in length (93 m in some experiments), where a soiled piece of pipe could be inserted without disturbing the flow. The soiling was milk‐based and dried on application. Light absorption of the soiled glass tube was measured before and after the cleaning operation, which was performed for 45 s with plain water at room temperature. To calculate the pressure drop, the so‐called Dukler constant‐slip‐method was used. A holdup correlation according to Hughmark was improved to fit the pipe system used.Through linear regression analysis an equation was obtained, describing the cleaning effect as influenced by the Reynold number and the liquid fraction of the air‐water mixture.