Choosing the right enclosure for harsh environments

An electrical enclosure’s ability to protect the controls contained within is impacted by environmental conditions.

Particularly in harsh environments such as mining and transportation, there is the risk of production downtime, injury and increased maintenance costs where an enclosure fails to do its job.

In the majority of cases, there will be a specific material that is better suited for long-term reliability and overall cost reduction. Enclosure material selection should be carefully selected, taking into consideration factors such as environmental characteristics and heating and cooling mechanisms. Environments can be either indoors or outdoors and, depending on location, there can be environmental factors such as moisture, ultraviolet or solar radiation, dust, temperature, and other chemical and physical conditions at the site of permanent installation.

An overspecified enclosure will work effectively in a natural environment — but in an underspecified enclosure, the internal equipment could be damaged, causing long-term consequences. Therefore, environmental factors override other considerations in materials selection. The most common corrosive element is water, which is usually present in enclosure applications. Additionally, adjacent processing operations or other intermittent activities such as industrial cleaning, salty atmospheres and the general plant environment may expose an enclosure to a variety of corrosive agents and temperatures.

The level of corrosion typically increases with moisture content, including rain, dew and condensation. While rain can have a beneficial effect as it washes away contaminants from exposed surfaces, if left to collect in pockets or crevices it will supply a source of continued moisture. When relative humidity exceeds 70%, a thin moisture film forms on a metal surface, providing an electrolyte. This dew or condensation can become very corrosive if it is saturated with a contaminant like sea salt or acid compounds from industrial sources.

Therefore, when choosing an enclosure material, start by identifying the environmental requirements of the application, and then narrow down the options to material types that fit the necessary requirements, size and ratings. Typical materials available include powder-coated steel, stainless, thermoplastic and aluminium. Evaluate the thermal considerations the material will need to withstand, and the reactions of each material to such conditions.