Designing products for harsh environments
Why is having the proper finish or material important?
A wide array of electrical products is available for a vast field of unique applications. While many of ABB Installation Products Division offerings, such as wall boxes, will perform in fairly moderate conditions, there are environments that call for a higher level of protection for specific products.
Weatherproof box covers, conduit bodies and similar products may be subjected to levels of environmental abuse not seen by some of our more common products. Outdoor areas, offshore facilities and ships docks, petrochemical facilities, food & beverage environments and other extreme locations often call for a heightened level of protection surrounding live electrical devices and electrical access points.
The two most common protection rating systems for these environments are IP (Ingress Protection per ANSI/IEC 60529) and NEMA (National Electrical Manufacturers Association). Both IP and NEMA have rating systems utilized for equipment that will be exposed to liquids, rain, stringent washing, ice and other contaminates such as particulates and dust. While the IP system only deals with physical liquid and solid ingress, NEMA also addresses corrosion protection as well as construction of enclosures. Adoption of an applicable standard varies by region, with IP being more prevalent in Europe while NEMA is more widely adopted in the United States. Although both systems classify various levels of protection, the most common and sought after for U.S. industries is NEMA 4X.
The IP and NEMA rating systems are described below.
(Chart reprinted by permission of the National Electrical Manufacturers Association)
NEMA 4X is considered “watertight”, which means it must resist 65 gpm of water from a 1” nozzle delivered from a distance of not less than 10 feet for 5 minutes. Per the NEMA 250 Standard, X denotes products with additional corrosion resistance. Both the watertight and corrosion resistant aspects can be achieved through innovative engineering design and careful materials selection.
NEMA 250 provides the definition of TYPE 4X protection and establishes the testing required for validation.
TYPE 4X – Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose-directed water); that provides an increased level of protection against corrosion; and that will be undamaged by the external formation of ice on the enclosure.
UL50E has criteria comparable to NEMA250 regarding 4X validation. Where the market demands listings for 4X rated products, UL will provide third party testing certification services. UL testing for 4X validation includes the following testing:
External Icing: Enclosure is cooled to 20oF and sprayed with water to form ice buildup. The box must maintain its function after the ice has melted.
Hose down: High pressure water, flowing at 65 gpm, is sprayed along the door seam and enclosure at a speed of ¼” per second. No water can enter the enclosure.
Corrosion Protection: 200-hour salt spray test, enclosure must show no signs of cracking or pitting
(300 series stainless will automatically meet requirements).
Note: Surface finish is important for food and beverage because it limits the inclusions/ nooks & cervices that can allow for bacteria growth.
Gasket Testing: Gaskets must undergo both tensile strength and compressions tests. Gaskets must show no signs of structural degradation, such as cracking or tearing.
Mounting Provisions: The mounting means shall not have the same mounting hardware pass through the equipment cavity and attach directly to the building wall. This will help protect what is inside the enclosure from external threats on opposing side of mounting surface.
In addition to meeting the UL performance requirements, UL requires special mounting provisions.
While the NEMA requirements govern much of the 4X enclosure’s design, other criteria must be considered when designing electrical enclosures for these extreme environments. In order to provide superior performance in a wide array of applications, common practice dictates the use of the following:
- Austenitic 300 series stainless construction, with 304 and 316 being the most common
- Closed cell silicone gasket (continuous/no gaps)
- Door/enclosure relationship for 40-50% compression of gasket when closed
- Sloped surfaces to divert liquids
An example of an ABB product designed specifically to deliver 4X protection for harsh environments is the Red•Dot® SSE – Stainless Steel While-In-Use Box and Cover System. which was tested and certified by UL for 4X protection in harsh environments.
While product applications will vary, it is important to keep in mind the ratings and requirements that will be needed to use in harsh environments.