Johannesburg, 27 Oct 2017
Q: What are the benefits of having a modular enclosure?
A: Modular enclosures can be a single enclosure or bayed together (expanded) to as many enclosures as needed. This also allows for simple future expansion and redesign. Modular enclosures can offer removable surfaces so the modification of the outside skins can be easily performed away from the enclosure frame. Removing outside skins also provides easy access for installing, wiring and maintenance of installed components - saving time and allowing multiple people to work on the same enclosure simultaneously. Modular components are lighter weight than heavy-gauge welded enclosures, so they are easier to handle and have lower transportation costs.
Q: How important is material selection?
A: Material selection is very important based on the application and environment the enclosure will function within. Investing in a corrosion-resistant material, such as stainless steel for a corrosive environment, will cost more upfront than a painted carbon steel enclosure, but will provide a return on investment with a longer service life. In applications such as WiFi or SCADA, you want a material that allows the transmission of frequency waves through the material. Steel enclosures do not readily allow wireless communication. In applications where the weight of the enclosure is critical - such as pole-mounted or on a tower, in an airplane or a ship, both weight and corrosion resistance are important and aluminium may be a good material option.
Q: What industries use small wall mounted housings?
A: Many industries use small enclosures commonly referred to as junction boxes or terminal enclosures. Junction boxes are commonly used for emergency stop (e-stop) enclosures for safely shutting down equipment or production lines. Every industry and application requiring electrical connections and protection will use small electrical junction boxes or control enclosures.
Q: How are these enclosures used by different industries?
A: Electrical enclosures serve two main functions - to protect the user or personnel from accidental contact with energised wires and components, and to protect the electrical wires and components from environmental elements that may cause an electrical short, corrosion or electrical failure. Enclosures can range from simple junction-style applications up to complex control enclosures and human machine interface (HMI) applications.
Q: Are there standards associated with these types of boxes?
A: Yes, in North America, the common third party agencies that give approval to these products are United Laboratories (UL) and Canadian Standards Association (CSA), which certify to NEMA type ratings regarding enclosure design and performance, including environmental. Globally, there are similar industry standard organisations that adhere to International Electrotechnical Commission (IEC) design and performance standards. Most indoor applications can use a NEMA Type 12-rated, painted carbon steel enclosure that provides protection to personnel from accidental contact, and a degree of protection from foreign objects such as dust, dirt, and dripping or splashing water. Outdoor applications typically require standard protection that addresses the ingress of water (rain, sleet, snow) and offers corrosion resistance from paint or corrosion-resistant materials such as stainless steel, aluminium, plastics or fibre glass. Environments requiring wash-down (F&B) typically require stainless steel, corrosion-resistant material and a sloped top for liquids to run off. Hazardous location may require either painted carbon steel or stainless steel and third party certification for use. Seismic areas have further structural and performance requirements that must be fulfilled.
Q: What are some of the features, materials, or fittings that affect the cost of design?
A: Many times, the actual components that are being installed into the enclosures have the highest costs. This is why the enclosure that protects these investments is critical. Costs are generally affected by the material chosen - an example would be stainless steel or aluminum - which have much higher costs than carbon steel. Enclosures designed for special applications such as wash-down have additional features and specialised components that increase their cost. Upfront investment may increase original system cost, but will provide longer system life and better total ROI.
Q: In selecting a small wall-mounted housing, what are the concerns and variables a designer should focus on?
A: The enclosure and panel size required to house the internal components, wires, and controls as well as entry into the enclosure. When selecting the material, a designer needs to consider the environment. Will the enclosure be exposed to chemicals, rain, things running into it, or people trying to vandalise or tamper with the components inside (locking and security)? The amount of heat being generated by internal components should also be considered as heat reduces life of controls. Proper management with climate accessories such as fans or air conditioners protect these investments and extend their usable life. Installing fans and HVAC in some enclosures is not out of the ordinary as a climate control precaution.
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