Understanding the Importance of Enclosure Impact Ratings

Enclosures play a crucial role in protecting electrical and electronic equipment against physical damage and environmental hazards, such as dust, moisture, and extreme temperatures. Impact ratings have become an important consideration for enclosures, especially in industrial applications and outdoor spaces where external physical or mechanical damage is a major concern. Aside from eliminating speculation, these ratings also ensure that they can withstand external physical forces and resist contaminants, humidity, and water in factory environments. Thus, enclosures play a key role in preventing equipment failure and saving companies on maintenance, repair, and replacement costs.

Toward that goal, enclosures are tested per the IEC 62262 international standard managed by the International Electrotechnical Commission (IEC), which defines the degree of protection provided by the enclosure for electrical equipment against external mechanical impacts. This degree of protection is further classified using an IK code for rating the enclosure on a scale of IK00 to IK10, where IK00 provides no protection and IK10 offers the highest. As a result, these ratings enable a user to select an appropriate enclosure that provides the needed durability, reliability, and safety for its specific operating conditions, such as an outdoor setting or a harsh industrial site.

Die-cast aluminum versus polycarbonate for enclosures

There are a variety of materials for the construction of enclosures, and each material determines the level of protection against physical damage as well as the overall performance of the housing. Fundamentally, enclosure material can be divided into two main categories: metallic and non-metallic. In the metallic space, non-ferrous metals like aluminum are attractive materials for enclosures. Depending on the application, aluminum is a popular material for outdoor applications due to its excellent strength, resistance to corrosion, light weight, and ability to shield electro-magnetic interference (EMI).

Similarly, in the non-metallic arena, plastic is a popular candidate that is available in two types: acrylonitrile butadiene styrene (ABS) and polycarbonate. ABS is a low-cost thermoplastic that is easy to process and shape, and is a standard choice for many indoor applications.

In comparison, polycarbonate excels in the plastic world. It is a very strong material that offers more resistance to breaking under pressure or impact, and its IK ratings are comparable to those of die-cast aluminum enclosures. Polycarbonate also has many other desirable properties, such as UV protection, a wide thermal spectrum, the ability to withstand corrosive chemicals, and flexibility to bend or stretch under pressure. UV stability allows a polycarbonate casing to withstand long-term exposure to sunlight without degradation, preventing the material from getting brittle and cracking over time. These characteristics make polycarbonate a suitable enclosure material for harsh outdoor conditions.

IK ratings and more

Hammond Manufacturing offers enclosures made of both metallic and non-metallic materials for a wide range of applications. For protecting electrical and electronic equipment from high impacts, they have produced die-cast aluminum series enclosures like the 1550ZF, the 1550Z, and the 1590Z, which offer a high rating of IK08 (Figure 1). At this rating, the enclosure can withstand an impact of 5 joules, equivalent to a 1.7 kg mass dropped from a height of 300 mm, providing a high level of protection for internal components. In addition to being strong and robust, die-cast aluminum enclosures are lightweight, electrically conductive, and resistant to corrosion. They offer a high level of EMI shielding and can handle extreme temperatures, dust, and water.

Figure 1: Hammond’s die-cast aluminum enclosures offer a high impact rating of KI08. (Image source: Hammond Manufacturing)

For users who prefer low-cost plastic alternatives, Hammond has polycarbonate enclosures (Figure 2) such as the 1554/1555 and the 1555F series that are on par with the die-cast aluminum impact rating of IK08, per the IEC 62262:2021 standard. Polycarbonate plastic is also much lighter than die-cast aluminum, with about half the density at 1.20 g/cm³ to 1.22 g/cm³. Despite being lightweight, polycarbonate enclosures are strong, environmentally sealed, and UV stabilized for outdoor use.

Furthermore, they have been independently tested to meet NEMA Type 4, 4X, 6, 6P, 12, and 13 ratings, which exceed an IP68 rating, and can withstand a wide operating temperature range of -40°C to +110°C (-40°F to +230°F). Taking all these factors into consideration, polycarbonate enclosures offer a durable and reliable solution for protecting electronic hardware in a wide range of harsh industrial, marine, and outdoor applications.

Figure 2: Hammond’s polycarbonate enclosures offer an impact rating of IK08. (Image source: Hammond Manufacturing)

To serve such a broad range of applications, Hammond produces the 1554/1555 series in 32 sizes, ranging from 2.6 in. x 2.6 in. x 1.6 in. (65 mm x 65 mm x 40 mm) to 11.81 in. x 9.45 in. x 4.72 in. (240 mm x 160 mm x 90 mm). These sizes encompass nearly 200 box and lid combinations. The primary difference between the 1555 and 1554 series is the lid design. The 1555 series uses a recessed cover for label or keypad mounting, while the 1554 has a flat cover.

For wall mounted or DIN rail equipment, Hammond has added the watertight, flanged-lid 1555F series (Figure 3) of polycarbonate enclosures with a high IK rating and excellent ingress protection (IP67) for harsh outdoor applications. Available in an industry-standard light gray finish (RAL 7035), these flame-retardant polycarbonate units incorporate numerous innovative features to provide unique functionality. For example, they come with a thick plastic flange for mounting, and include a top cover, a replaceable silicone gasket, and four self-captivating stainless steel assembly screws. To avoid corrosion caused by water or contact between dissimilar metals, the stainless steel machine screws thread into stainless steel bushings.

Figure 3: Designed for wall mounting, the 1555F series of polycarbonate enclosures come with thick plastic flanges. (Image source: Hammond Manufacturing)

The environmental sealing is achieved through a two-piece tongue-and-groove construction with a molded silicone gasket to seal the enclosure. To eliminate water ingress, the assembly screws and inserts are placed outside the gasket perimeter. In short, polycarbonate enclosures deliver a host of benefits that makes them an attractive, practical choice for tough outdoor applications.

Conclusion

Enclosure material is a key factor to consider when selecting an enclosure for electrical equipment, especially for outdoor applications. Both metallic and non-metallic options are available with a high IK rating. Die-cast aluminum is lightweight, provides superior strength, electrical conductivity, corrosion resistance, EMI shielding, and durability. Plastic-based polycarbonate is a cost-effective, lightweight alternative to die-cast aluminum, with added benefits like UV stabilization and flame retardancy.