Common product characteristics including being sticky and cohesive have a tendency to ‘build-up’ on the swept surfaces.
Most foodstuffs are biodegradable. However, some do not post a hygiene risk as they represent or contain a sterilising or preserving agent; such products include sugar, salt and chocolate and a standard rotary valve construction only is required. Other products that have a long storage life, providing they remain dry, also do not require special features especially if they will be further processed by cooking. Flour and rice are typical examples. In all these cases unless there is corrosion risk, cast iron/carbon steel would suffice, however most users now require stainless steel, as a matter of course.
Food products that are subject to bio-degradation require careful consideration depending on the degree of sensitivity. Stainless steel construction is essential, as is the need for the construction to be free from cracks and crevices where residual product can collect, decompose and contaminate fresh product.
Welds and internal surfaces are usually polished and also useful is to have an easy access to the valve internals for cleaning.
For low sensitivity materials requiring only infrequent cleaning simple access, quick release fitting only can be considered. This is a low cost option but suffers from disadvantage that components are easily damage and it is not particularly operator friendly, requiring risk assessment under the safe handling regulations especially for the larger rotary valve sizes. Weight and sharp edges are particular hazards.
High sensitivity materials such as baby food products and high fat milk powder require a higher degree of contact surface finish and integrity, often polished to a mirror finish.
Most food ingredients are potentially explosive in dust form and will be subject to the ATEX Directive. Whenever a valve is required to act as a flame containment device, regardless of pressure condition or external environment, then it automatically becomes categorized as an Autonomous Safety System requiring certification of a Notified Body who must approve the technical file and manufacturing procedures.Click here for more information about Gericke RotaVal
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