A tomato paste plant is built around one tall vessel
A tomato paste line receives fresh fruit, crushes it, evaporates water out of it, sterilises the concentrate and fills it aseptically. The evaporator is the tallest item and the most demanding, and everything else arranges itself around it.
Three things make these plants distinctive: the height of the evaporator, the heat it rejects, and the fact that the whole plant runs for a few months a year at full rate.
Height comes from the vessel, not from the plan
A multi-effect evaporator is a vertical stack of effects with interconnecting pipework, and it needs headroom above it for the vapour lines and access. A building designed from a floor plan will be too low every time.
The right sequence is to take the evaporator elevation first, add the pipework and the lifting height, and then set the eave. The same logic applies to the aseptic filler and to any steriliser in the line.
If the plant expects to replace the evaporator, the envelope also needs a removal route. A vessel that came in through an open roof cannot leave through a finished one.
Heat rejection is continuous during the season
Evaporation means boiling off water, and that heat ends up in the room. During the season the hall rejects heat continuously, day and night, and the climate in most tomato-growing regions is already warm.
High-level openings sized for that heat load, rather than for general ventilation, are the difference between a workable hall and one that is uninhabitable by mid-morning. Where the roof is insulated, the liner also stops the underside condensing.
Washdown is intense and it is seasonal
Tomato processing is wet: fruit washing, juice spills, and a full washdown at the end of each shift. The floor is wet for the whole season and then dry for months.
That pattern matters for maintenance. Corrosion that starts during the season is discovered during the off-season, when the plant is empty and nobody is looking. A plinth at the column base and a coating selected for the actual cleaning chemicals is what keeps that inspection from finding a problem.
A seasonal plant has a different structural rhythm
Running flat out for three months and standing idle for nine changes the design priorities. Thermal cycling is severe at the start and end of the season. Equipment sits unused and damp. Maintenance access has to work when the plant is empty, not only when it is running.
The building itself can be simpler than a year-round plant in some respects and must be more robust in others. Knowing which is which comes from asking how the plant is operated, not from a standard specification.
What I want before drawings
- The evaporator elevation, mass and support arrangement.
- The aseptic filler and steriliser heights and the removal route.
- The heat rejection from the process and how it is expected to leave the building.
- The length of the season and the washdown regime.
- Whether the plant runs continuously or in shifts during the season.
- The wind speed for the site in km/h from the applicable local code, not a round number.
Paste plants are among the clearest examples of a building that should be designed from the equipment outwards. The vessel elevations are available early; using them early is free.
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: height set by what has to be lifted · zoning a hygiene process · a seasonal process with concentrated loads · corrosion class as a selection input
