Operator interface enclosures are used to house industrial controls such as display screens, pushbuttons, keyboards, lights, and other operator control devices. They are designed to protect personnel from accidental injury and to prevent the ingress of environmental contaminants such as dust and water.
When selecting enclosures, correct size and adequate protection are the priorities. When considering quality of protection, material type and professional rating systems are the deciding factors. Additional features such as locks, keypads, impact resistance, or knockouts may be important depending on the application.
Sizes and Shapes
The size and shape of an enclosure depends on what is being encapsulated. Operator interface enclosures are rectangular or T-shaped. Enclosures may come in standardized dimensions or shapes which can be stacked for assembly, or they can be custom built to particular specifications. Most operator interface enclosures are mounted on suspension/pendant systems or pedestals.
The amount of protection and durability an enclosure offers depends largely on its material composition. Most enclosures are made from materials classified as either metals or polymers.
- Metals generally exhibit higher conductivity to both heat and electricity than other material types. Steel is widely used to form enclosures because of its strength and malleability. Stainless steel is used rather than standard steel in environments requiring corrosion resistance and lightweight materials. Aluminum is a less expensive, lightweight, and more conductive metal that exhibits good resistance to oxidation.
- Polymers are nonmetal materials with varying properties. ABS is a hard, rigid, inexpensive thermoplastic polymer that has good chemical and creep resistance, but is prone to cracking under stress. Fiberglass is a strong, durable, reinforced polymer that is resistant to many caustics and extreme temperatures. Polycarbonate exhibits excellent impact strength and can be molded to tight tolerances, but has only moderate resistance to chemical corrosion. Polystyrene is used for its rigidity, hardness, heat, and dimensional stability and because of its ease of fabrication.
End panels are often made of clear, infrared, solid, or transparent plastic and include cutouts for DB9 or DB25 connectors.
NEMA ratings indicate whether enclosures are suitable for hazardous or non-hazardous locations and designed for indoor or outdoor use. All NEMA enclosures protect personnel against incidental contact with the enclosed equipment.
The Ingress Protection (IP) ratings system from the International Electrotechnical Commission (IEC) describes the degree to which enclosures provide protection against the ingress of foreign objects and moisture. There are six IP ratings that describe protection against foreign objects and vary from >50mm particle protection to completely dust-tight protection. There are eight IP ratings for protection against moisture which vary from dripping water protection to protection when completely submersed.
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NEMA and IP Enclosures
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