The term "process piping" generally refers to piping systems that convey chemicals under pressure or vacuum. It also is used to describe utility piping systems that are used in, or in support of, a chemical process, such as plant water. Also, certain drainage piping--where corrosive or toxic fluids are being transported and severe conditions may be present, or where it is simply outside the scope of plumbing codes--is also sometimes classified as process piping. Some places where process piping is used are obvious, such as chemical and petrochemical plants, petroleum refineries, pharmaceutical manufacturing facilities and pulp & paper plants. However, there are many other not so obvious places where process piping is commonplace, such as semiconductor facilities, automotive and aircraft plants, water treatment operations, waste treatment facilities and many others.