Why do engineers allow valve overlap?

What differentiates chemical engineers with other engineers?

Chemical engineers focus on designing and operating chemical processes - whether that be creating chemicals in bulk through chemical reactions or using chemical properties to separate mixtures of chemicals (like in oil refineries). Mechanical engineers focus on transforming energy from one form to another - like machines. There is some overlap between mechanical and chemical engineering because both disciplines get involved in heat exchangers, pumping, mixing, and vessel design. Civil engineers tend to be more focused on designing and building structures, roads, etc. Ther is often overlap between civil engineers and chemical engineers in the field of environmental engineering and sewage treatment where chemical processes and separations are often involved. Electrical engineers focus more on electricity and electronics so they overlap less with chemical engineering except in the area of controls and instrumentation. Industrial engineers focus on process efficiency. While all engineers have to apply some of the principles of industrial engineering, industrial engineers specialize in it. Petroleum and atomic engineers tend to cover most of the same areas as chemical engineering but with additional trining in oil extraction and atomic physics respectively.