SUMMARY—Factors such as inclination angle of the test surface, flow rate and temperature and composition of cleaning solutions were examined for their influence on cleaning an 18‐in.‐wide sheet of No. 4 finish stainless steel by gravity flow of falling films of water and detergent solutions. A suspension of B. subtilis spores was used to contaminate the test surface. After a cleaning treatment, the percentage of spores remaining as measured by a direct surface agar plate method IDSAPI was used to calculate cleaning efficiency. Flows of water and cleaning solutions ranged from 50 to 250 lb/min. After detergent solutions, a post‐rinse with water at 100°F for 5 min was used. Another setup with a smaller plate and a constant flow rate of 45 lb/min was used to study the effect on cleaning of varying plate angle between the limits of 60 degrees either side of vertical. Washing time was standardized at 10 min for the large plate and 15 min for the smaller one. Results indicated that cleaning improved with temperature, flow rate and with the presence of acid or alkaline cleaning agents. Cleaning was most effective when the plates were in the vertical
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