In today’s industries, digital control panels find a broad range of applications. As system controllers in industrial settings, they are responsible for controlling and regulating the operation of various equipment and devices.
Apart from enhancing efficiency, flexibility, and reliability of running devices, panels like temperature control panels allow engineers and technicians to easily monitor heat and other various parameters such as pressure, voltage, and so on.
Safe installation and equipment standards
In potentially hazardous settings, specially designed control panels are used to reduce the risk of explosion. There are various standards and guidelines that are used in the design and fabrication of explosion-proof control panels. To start with, the National Electrical Manufacturers Association (NEMA) provides a set of guidelines that must be complied with when designing enclosures for industrial applications.
NEMA provides a set of guidelines that must be complied with when designing enclosures for industrial applications
In North America, the National Electric Code (NEC) defines standards that ensure the safe installation of equipment and electrical wiring. The Atmosphères Explosives (ATEX) provides standards that describe the use of equipment in explosive atmospheres.
In addition, there are various agencies that test equipment to ensure that they comply with the applicable standards. Underwriters Laboratories (UL) and Factory Mutual (FM) test equipment and issue compliance certifications. Although the list of bodies and agencies that define standards is virtually endless, the rules and guidelines that they provide are similar in many ways.
Protection mechanisms
In explosion-prone industrial settings such as oil and gas hazardous environments, ignition sources can easily trigger the combustion of flammable substances such as vapors, gases, dust, and so on.
Such ignition sources include electric arcs, hot surfaces, thermite sparks, flames, electromagnetic radiation, smoldering deposits, and electrostatic sparks. Several different protection mechanisms serve to prevent an explosion from these ignition sources.
Protection concepts
Various protection concepts are used when designing control panels for hazardous industrial environments. The explosion-proof protection layer is a popular mechanism. This mechanism employs specially designed enclosures to encase digital control panels. For large panels, the purge and pressurization method isolate them from the hazardous environment.
The third protection layer, intrinsic safety, works by limiting energy to ensure that ignition does not occur. This protection mechanism ensures that the components of any panel are incapable of producing enough energy to trigger the combustion of flammable gases.
Design and fabrication of control panels
An explosion-proof enclosure should be capable of containing the initial overpressure resulting from internal ignition. Secondly, the enclosure should have carefully designed flame paths to allow expanded gas to escape.
Apart from meeting these conditions, an explosion-proof design produces a temperature that is below what is capable of igniting gas and dust in the surrounding environment. This means that the operating temperature of explosion-proof control panels should be lower than the minimum temperature necessary for the ignition of combustible gases in the surrounding environment to occur.
Cooling Process
How does an explosion-proof design prevent explosions from occurring? The presence of a carefully calculated series of gaps in an enclosure provides expanding gas with an escape route. As the expanded gas escapes from the enclosure to the external environment, it cools and loses most of its energy. The cooling process makes it incapable of causing an explosion thereby ensuring that a facility is safe.
Control Panel Materials
Most explosion-proof enclosure designs use cast metal, fabricated steel, stainless steel, cast aluminum, or fiberglass
Most explosion-proof enclosure designs use cast metal, fabricated steel, stainless steel, cast aluminum, or fiberglass. Each enclosure is expected to withstand a hydrostatic pressure that is at least two times the maximum explosion pressure.
This parameter, together with flame path requirements, varies from one division/zone of protection to another. Enclosure designs comply with NEMA 7, 8, 9, or 10 specifications depending on their environment of the application.
Explosion-proof control panels find applications in industries that have demanding safety requirements. They are widely used in the oil and gas industries, wastewater industries, manufacturing industries, and other processing industries. In all these cases, the enclosures may differ in design depending on the NEMA specifications that they are designed to comply with.
