Pressure Switches Design Requirements in Process Industry

This article establishes requirements for Pressure Switches used in process plants. Main keywords for this article are Pressure Switches Design Requirements in Process Industry. References Pressure Switches. Definitions Pressure Switches. pressure sensing element.

References Pressure Switches

Reference is made in this article to the following documents.
National Electrical Manufacturers Association (NEMA)
NEMA Standard for Electrical Equipment Enclosures
National Fire Protection Association (NFPA)
NFPA 70 National Electrical Code

Definitions Pressure Switches

For the purpose of understanding this standard, the following definitions apply.

Bellows.
A pressure sensing element of generally cylindrical shape whose walls contain deep convolutions, and for which the length changes when a pressure differential is applied.
Bourdon Tube.
A pressure sensing element consisting of a twisted or curved tube of noncircular cross section which tends to be straightened by the application of internal pressure.
Diaphragm.
A sensing element consisting of a thin, usually circular, plate which is deformed by pressure differential applied across the plate.
Explosion Proof Enclosure.
An enclosure that is capable of withstanding an explosion of gas or vapor within it and prevents the ignition of an explosive gas or vapor that may surround it.
Intrinsic Safety.
Design methodology for a circuit or an assembly of circuits in which any spark or thermal effect produced under normal operating and specified fault conditions does not ignite explosive atmosphere.
Pressure Element.
A device that converts a pressure value into motion or movement.
Pressure Switch.
A device that activates or deactivates an electrical circuit when a preselected pressure is exceeded in a process vessel or piping system.