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Home>MACHINE BUILDING & ENGINEERING>Enclosures>Specifying & customising non-metallic industrial enclosures

Specifying & customising non-metallic industrial enclosures

16 January 2018

Bill Schweber of Altech, an established United States supplier of industrial components, looks at some of the capabilities of non-metallic enclosures for industrial and agricultural applications

ndustrial installations and production facilities are often harsh settings, with oil, dirt, vibration, physical abuse and other numerous issues. A modern agricultural operation can be as bad as or even worse than an industrial environment. There are constant dirt, crop dust and discards, physical impact, extreme temperatures (both hot and cold), extreme weather (storms, flooding) and more. Further, unique to the farm environment is the presence of animal waste (primarily ammonia), which is corrosive to many materials.

Electrical and electronic cable, connectors and related subsystems need rugged enclosures, and non-metallic enclosures offer distinctive benefits compared to conventional units. The common solution is to select a suitable metallic enclosure, either steel or aluminium, to provide the needed ruggedness and protection. However, a non-metallic polycarbonate enclosure can be the better choice, as it resists moisture, corrosion, chemicals and even ammonia. Non-metallic enclosures are also easy to customise to help with branding, and provide a more professional appearance overall.

ABS enclosures are ideal for indoor use while polycarbonate enclosures, on the other hand, are suitable for indoor or outdoor use in remote or harsh applications.
Polycarbonate enclosures offer other advantages in addition to basic ruggedness. Obviously, they are rust-proof and have no surface finish that can wear or chip, thus allowing rust to take hold. They meet and exceed all relevant industry standards for corrosion, impact resistance, ingress protection and flammability and more. EMI/RFI shielding can be specified to protect sensitive electronic components and custom versions can be developed to meet particular application requirements.
UL-listed polycarbonate enclosures protect control and measuring equipment against dust, water, and corrosion in the harshest operating environments. They meet various relevant standards, among them:

- UL94 (Flammability of Plastic Materials);

- NEMA IP66/67 (particle and water ingress);

- VDE 0471 (fire hazard);

- IK07 (impact);

- Wide operating-temperature range of -35 to +80°C.

A special feature of polycarbonate enclosures is that they can tolerate high concentrations of ammonia, meeting the stiff certification requirements of the German Agricultural Society (Deutsche Landwirtschafts-Gesellschaft, or DLG). They can withstand an ammonia concentration of 750 ppm (parts per million) at 70°C and 70% humidity over 1,500 hours of continuous testing.

While the physical sizes of polycarbonate enclosures are standardised, this is not a serious constraint, as they are available in a wide range of height, width and depth dimension combinations. Once a basic enclosure is chosen, many attributes and features can easily be customized. Vendors can do value-added work to reduce end-user effort even for moderate volumes, typically beginning at just 25 units. Among these are:

- Choice of hinge type (internal, external);

- Choice of mounting style and orientation;

- Panel cutouts for displays, indicators, keypads and other functions;

- Pre-packaged connectors and pushbuttons;

- Imprinting and labelling;

- Choice of transparent or opaque cover.

Three types of printing are commonly available at: high-performance overlay, digital printing; and screen printing. High-performance overlays are attractive for enclosures due to the recessed cover design of this series. Digital printing is generally for high-quality printing for small production runs. The screen printing option is best for medium or large production runs that use only a few different colours on one print job.

Metric knockouts enable the installation of cables, cord grips, conduit adapters and entry spouts, while maintaining a sealed enclosure with protected components. The knockouts are factory moulded and are removed easily and quickly after scoring.

Depending on how often the enclosure is to be opened and closed, an option is to equip it quick-turn screws that provide quarter-turn operation. For control circuits, an enclosure that offers a cover recess can incorporate a detailed label inlay or membrane keypad. An integrated cover retainer or hinge kit can make using the enclosure easier. Most applications also require some type of mounting provisions inside the enclosure such as integral mounting studs. Another option might be an enclosure equipped with internal hinges.