Crude oil storage tanks are large above-ground tanks used to store crude oil and other petroleum products. These tanks can range in size from 10,000 to 42 million gallons, and are usually made of welded steel or stainless steel. The crude oil storage tanks are typically cylindrical in shape, with a floating roof to allow for expansion of the stored liquid. The tanks are often equipped with internal floating roofs, which are used to reduce evaporation and control emissions.