They occupy large spaces as may be seen from the aerial photograph of three large thickeners.
They are normally positioned far away from the center of the plant and owing to the large flows they are fed by gravity to save pumping. Therefore their position for a given hydraulic gradient may determine the elevation of the entire plant.
Rake driven thickeners for continuous operation can impose a substantial burden on capital investment.
Unlike many other types of equipment, thickeners have no stand-bys so if one goes out of commission it cannot be by-passed. Consequently, if this happens other thickeners have to take the extra load but if the plant incorporates just one thickener then the entire production line must stop.
To take a thickener out of commission for repairs inside the tank such as damaged blades, or rubber lining may take days since it requires to empty the tank, remove the underflow bed, refill it and find a suitable storage or disposal site for very large volumes of liquid.