Valve

These water valves work with handles.

Valve is a fluid regulation and control instrument. A more complete definition describes the valve as a mechanical device with which the circulation (passage) of liquids or gases can be started, stopped or regulated by means of a movable part that opens, closes or partially obstructs one or more holes or ducts. It is necessary to differentiate that there are valves that allow a fluid to pass in one direction and prevent it in the opposite (including the so-called electrical fluid), as usually happens in the use of industrial valves, a field in which it can be considered as a basic instrument.

Due to their design and materials, the valves can open and close, connect and disconnect, regulate, modulate or isolate a huge series of liquids and gases, from the simplest to the most corrosive or toxic. Their sizes range from a few millimeters to 90 m or more in diameter (although in large sizes they are often called gates). They can work with pressures ranging from vacuum to over 140 MPa (megapascals) and temperatures from cryogenic to 1100 K (kelvin). In some installations an absolute seal is required; in others, leaks or runoffs are not important.

The word flow expresses the movement of a fluid. For the total amount of fluid that passes through a given section of a conduit per unit of time, the word flow is used in Spanish.

Keys

A frequent confusion in the language consists of mixing the idea of valve with that of key. A stopcock usually refers to mechanisms that allow opening, closing or regulating the flow of a fluid, that is, liquids and gases with relatively low flow rates (usually in building installations). When it comes to fluids with large flow rates (water or air) these keys are called hydraulic gates.

Classification of valves according to their uses

• Industrial valves.
  • Seat valve.
  • Shirt valve.
  • Hydraulic valve, particular case of industrial valves.
  • Wash or pass valve, case of valves in residential buildings (both for water, and for fuel gases).
  • Multi-way valve, device that works in hydraulic circuits, dividing or mixing fluids from different sources, usually to modify its temperature.
  • Safety valve, for cases of excess pressure, breakdown or thermal expansion.
  • Antireturn valve or retention valveused to prevent a fluid from moving in an unwanted sense along a pipe.
  • Rotary valve, used in wind-metal instruments.
• Thermostatic radiator valve, used to control the flow in heating radiators.
• Heart valves.

By analogy, valves are also called devices that regulate the passage of electrons in certain circumstances:

• Thermoonic valves.