This type of equipment is used to remove solids from a liquid, or to separate liquids of different densities or viscosities. Many models of sifting and separating equipment allow the use of aids to make the sifting process more effective. Some variations of equipment use added liquid or air bursts to move the products through the sifter and provide a more thorough sifting stage. This equipment is commonly used in the pharmaceutical, biotechnology, and dairy industries.