Heated tanks lose temperature faster as storage temperature increases. In one case involving a large tank farm, operators turned steam on until a pre-set temperature was reached then turned the steam off. This - sawtooth- temperature profile consumed almost double the steam compared with controlling the steam to maintain a constant tank temperature. When the new controls were implemented, the net saving was a staggering 50t€/h.
Stored heavy products tend to produce a colder layer at the tank walls with a hot core. It is therefore important for temperature control that thermowells penetrate at least 450 mm into the tank to get a representative reading.
Depending on the product, it is possible to stop heating altogether until shortly before the tank contents have to be moved.
Bayonet type steam heaters can be more effective to provide low pump suction viscosity than heating the whole tank.
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