The amount of water removed per unit of steam used increases with the number of evaporator stages and with design variations such as vapor recompression. The short-tube vertical evaporator is used in the sugar industry for cane sugar juice concentration. An agitated film evaporator, like the falling-film evaporator, is commonly used for heat-sensitive and highly viscous materials. Evaporators can balance and economize plant-wide steam management. If the evaporator feed storage capacity is sufficient, the level of evaporator operation can be adjusted to match the availability of waste steam. Evaporator levels are prone to oscillate due to interactions between level and product concentration control loops or between level and pressure loops. In most evaporator applications the control of product density is constantly affected by variations in feed rate and feed density to the evaporator. In the case of evaporators, the saying “One can control a process only if one fully understands it,” is particularly true.