History of can washing The beverage can washing process was created from the areo industry, used to prepare aircraft flying surfaces The washing process was developed with the aluminum two piece can manufacturing developments in the 1950/60’s, but it has not significantly changed for many years. There have been developments over the last few years to improve efficiency and reduce water usages.
How is good cleaning achieved? To achieve cleaning with the utmost excellence, a simple way is to consider the following important variable factors. Chemical Action – It is very important to understand the chemistry which is summarized as follows:- The acid cleaning processes (Stages 1 & 2) are usually based on sulphuric (H2SO4) or phosphoric (H3PO4) acid solutions and surfactants. However, hydrofluoric acid (HF) is added as an activator. Surfactants are also added to prevent re-attachment of contaminants. A number of washer systems include a treatment stage (Stage 4) which is designed to apply a Zirconium coating to the cans to prevent corrosion during the sterilization process prior to filling the cans. There is a final stage (Stage 7) which has been included in the last few years. This process applies a Mobility Enhancer (M.E.) coating to the outside surface of the cans to reduce surface friction to improve the mechanical can handling at the higher throughput speeds now being demanded. Mechanical action – The cans are transported through the washer tunnel on an open mesh conveyor belt. The cans are transported through a number of separate stages which contain a duplicity of spray nozzles. The different spray systems are designed to create spray pattern that provides a mechanical cleaning action to create liquid forces to remove residues, to create an even distribution of chemicals in and around the can. There are spray systems which create an even water distribution pattern to rinse the cans after each chemical treatment stage with clean water.
The spray systems comprise plurality of spray bars which are populated with proprietary nozzles. The sprayed liquid is contained in a tank and pumped to the nozzles via a complex series of pipes and valves. The pressures and flows are accurately controlled to ensure efficient operation and good can coverage. Temperature – Temperature of the chemical stages is very important to ensure the chemical reaction with the aluminum takes place effectively. The correct temperatures also prevent unwanted effects such as foaming. The typical acid cleaning Stages are designed to operate in a temperatureof 50 – 70 °C. The Chemical Treatment, Stage 4, operates at a temperature of 45 °C. The Rinse Stages and the M.E. stages are not heated but generally acquire a temperature of about 20—40 °C depending upon ambient conditions. Time / Impacts – The time and frequency of the cans being exposed to the sprays within the chemical stages has a direct effect on the efficacy of the cleaning and treatment processes. If the cans are exposed to the chemical spray for a short time the chemical will be reactive when it is being sprayed onto the cans. The chemical quickly becomes non-reactive when no spray is being applied. It is proven that if the cans are continuously exposed to sprayed liquid the cleaning becomes more effective. Stolle have developed modern spraying systems that maximise the number of spray impacts that can be applied to the cans and this has been proven to provide good clean cans at the higher speeds and the design has reduced chemical usage and therefore costs. Typical residence times used have been between 5 and 60 seconds, but these are under review.
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Andy Raynor is Product Director for Stolle’s Can Washer & Thermal Process Product Lines based out of Altham Offices in the UK. He has over the 19 years’ experience in the can making industry specialising originally in thermodynamics and was responsible for the design and manufacture of 2 Pc Can Making Ovens, before moving into fluid dynamics and applying his experience in Can Washing and Drying. Andy is now involved in implementing sustainability strategies across both the Washer & Ovens Products. He has held numerous roles throughout his career prior to joining Stolle in 2017, from Design Engineer, through to Service Engineer/Manager onto Operations and then Technical Director. Andy is a time served Mechanical Engineer serving his apprenticeship originally in the car industry before moving into can making back in 2003.
FUNDAMETALS Newsletter
Q1 2023 [ 11 ]
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