In the process industries, such as refining, pulp and paper and water purification, valves are named for one of three things: The type of valve, such as a butterfly valve; The operator of the valve, such as motor operated valve; The function of the valve such as isolation valve. Needless to say, a combined description such as a motor operated butterfly isolation valve is more complete yet to fully and unambigiously describe a valve, you really need a specification sheet like ISA 20.50.

The common feature amongst valves is that they open an orifice to allow some kind of media to flow through it. The orifice can be revealed in either a rotary motion such as in a ball valve or a linear motion as in a globe or spool valve. The interaction between the orifice and what blocks it gives the valve certain qualities which make it more or less suitable for particular applications. For example, when a quarter turn ball valve is opened (these are commonly used as gas line isolation valves in homes), the hole increases in size at an increased rate when turned at an even rate throughout the whole of the opening stroke. This property is know as the "equal percentage" characteristic and can be summarized as: When you turn the valve through say 5 degrees, the ratio of the opening size between the start and end positions is the same for any starting position.

Other valve characteristics are possible such as linear or quick opening. These are best shown on graphs. If you plot percentage open across the bottom and area of opening (or Cv, valve co-efficient) upwards, all the curves start at the origin and end in the upper right corner. The linear curve is a straight line from one to the other, equal percentage is like a parabola, hugging the bottom until all of a sudden rocketing up to the upper right corner. The quick open is a mirror image of the equal percentage, hugging the vertical axis until it makes a dash across the common end point. The use of these valve characteristic is applied in the area of control valves which modulate in a middle position nudging and bobbing in response to some varying signal from the control system.

For non-control valves, the principal criteria is tightness. Many moons ago, the only sealing technology was a metal on metal seal. With the development of elastomers such as PTFE (poly tetra flouro ethylene), sold under the trade name Teflon, valves have been expected to not let a bubble of leakage through (hence bubble-tight).

Piping systems and applications demand a wide variety of valve solutions from exotic alloys and plastics for handling corrosive acids and bases to expanded outlet segment control valves for optimizing the control of the flow of wood pulp in solution. Special end connections, materials of construction, operators, painting treatments and non-destructive testing: these are all possible special requirements that the valve manufacturer must be able to supply.

A list of different kinds of valves: