Food Processing Equipment Design
Practical Action
is the preferred material for these foods but it is expensive and often unobtainable, plastic is a
suitable alternative if these foods are not heated but there is no alternative to stainless steel for
heating acidic foods. Low acid or dry foods do not have the same problem and aluminium,
galvanised iron, enamelled iron and even brass or copper vessels can be used. However, the last
two should never be used in contact with oils or fats and aluminium should not be used with
meat. In each case the metal surface should be polished smooth for easy cleaning.
Metal joints should ideally be welded with a continuous weld which is ground to a smooth finish
with a grinding tool. Crevices, cracks, weld debris and burrs should be removed by grinding and
inside corners of equipment should have a radius greater than 1/4 inch. These precautions
prevent the accumulation of food and allow easy cleaning. If welding is not possible, metal joins
can be pop-riveted and sealed with a strong adhesive such as 'Araldite'. Solder can also be used,
subject to the above precautions and provided that the solder contains at least 50% tin and is
free of poisonous metals such as cadmium and antimony.
All bearings leak oil or grease to some extent and they should therefore be positioned outside of
the equipment so that they cannot come into contact with the food.
Figure 1: Support leg design to prevent soil accumulating
Electrical wires should be grouped together where possible and placed inside a smooth conduit
for easy cleaning and protection from water splashes. Electric motors should be enclosed for
similar reasons. Pipes for steam and hot water should be insulated for safety and the insulation
should be covered with a smooth material for easy cleaning. All pipes should be at least 6" from
a floor or wall to allow cleaning behind them.
Machines should be supported off the floor for proper cleaning underneath. The place where the
support legs meet the floor should be carefully designed to prevent soils accumulating see Figure
1. A minimum number of supports should be used.
The insides of pipes and equipment should be easily accessible for cleaning with brushes.
Dead-ends to pipes should be avoided and all bends should be smooth and never right-angled. A
useful rule is that the radius of the bend should not be less than the outside diameter of the
pipe. Pipe joints are needed to gain access for cleaning and these are a particular source of
contamination. Ideally, a sanitary metal pipe fitting, which has no internal thread, should be
2