A frying line puts hot oil, steam and starch in one room
A snack line extrudes or slices a starch base, fries it in hot oil, seasons it and packs it. The fryer is the centre of the building and it dominates everything around it.
The fryer releases heat and water at the same time
Frying drives off the water in the product into the oil and then into the air above it. A continuous fryer therefore releases a large volume of steam together with radiant and convective heat.
That combination is worse for a steel envelope than either one alone. Steam alone can be vented. Heat alone can be ventilated. Steam plus heat produces a warm, saturated atmosphere that condenses on any surface below the dew point, which in a steel building means the underside of the roof.
An extraction hood over the fryer, discharging above roof level, plus a liner over the fryer area, is the standard arrangement. Doing only the hood leaves the rest of the roof condensing onto the line.
Oil reaches surfaces the extractor does not
Fryer oil aerosolises, and the aerosol deposits on everything within the hall: walls, beams, the tops of machines, the underside of the roof. It is sticky, it holds dust, and it is difficult to remove once it has polymerised.
For the building, that means surfaces that can be cleaned and a coating that resists oil rather than one selected for general food service. Where a liner is used, the liner is what gets cleaned and the steel behind it stays protected.
Seasoning dust is the second problem
Seasoning drums and conveyors throw off fine starch and salt dust. Salt is corrosive in its own right, and starch is combustible. Both settle on horizontal surfaces, and in a hall where the air is already greasy they stick rather than blow away.
The roof over the seasoning area is therefore a bad place for a deep profile. It collects a mixture of salt, starch and oil that holds moisture against the steel permanently.
The floor is slippery for a reason
Oil on a concrete floor is a safety hazard, and it also means the floor cannot be cleaned by simple washing. Falls to a gully, a lip at every column base and a floor finish that resists oil are the three items that decide whether the hall can be kept in a condition worth inspecting.
What I want before drawings
- The line layout with the fryer, seasoning and packing positions.
- The fryer heat and moisture release, and the extraction concept.
- Whether a liner is intended over the fryer area.
- The cleaning method and the chemicals used.
- The oil storage and handling arrangement.
- The wind speed for the site in km/h from the applicable local code, not a round number.
Frying halls age faster than almost any other food building, and almost all of that ageing happens at the roof and at the floor. Both are cheap to design correctly and expensive to correct later.
Written by Johnny Joe, who advises owners and project managers in Africa and South America on steel buildings. If this decision is live on a project, send the layout and the constraint that worries you and I will tell you what it changes.
Related: another continuous wet production hall · dust and odour from a dry process · corrosion class as a selection input · zoning a wet and dry process
