Enclosures
All wrapped up – selecting enclosure materials
By Mandy Thompson, sales manager, BCL Enclosures P
rotecting electronic and electrical installations with a correctly-chosen, high-quality enclosure is essential to ensure the contents perform optimally throughout their lifespan. What
kind of environment and use conditions will the enclosure have to withstand in order to protect its contents? Both will determine the required specification and fundamentally affect the choice of enclosure material.
IK and IP ratings
IK ratings for impact resistance range from zero protection to IK10, which is equivalent to the impact of a 5kg mass dropped from 400mm above the enclosure, necessary for a lot of industrial and marine-type installations. IP ratings cover how well the enclosure prevents moisture and solid objects entering. The first digit describes the degree of protection from solid objects of a specified size, ranging from accidental contact by hand (IP1X) to full protection from particulates such as dust and material sprays (IP6X). The second digit is the degree of moisture protection, ranging from none to total immersion at a specified depth and time period. “Waterproof” for most general purposes is considered to be IP65, IP66 and IP67, with IP65 the minimum for exterior use. Reputable manufacturers will always be able to state exact IP ratings.
Having considered the environment and use conditions and determined the IP and IK rating required, it’s time to consider the advantages and disadvantages of the different materials available.
Plastic enclosures
Plastic enclosures are generally ABS, polycarbonate or polypropylene. ABS provides good all-round protection and is resistant to impact, water and dust, depending on specification. It can also be specified as standard or flame-retardant. ABS is generally more suited for enclosures for interior use, because it can become discoloured and brittle after long-term exposure to UV light, but can be useful in
28 February 2022 BEDSS stainless steel enclosure from Hylec
enclosures may be the only viable option. Metal enclosures are generally more expensive than plastic enclosures and it is important when comparing options from different manufacturers to consider what is included as well as the enclosure itself. Wall mounting brackets, mounting plate, spaces, locks and keys, and earthing straps have to be bought separately in some cases, adding significantly to the per unit cost, whereas some manufacturers include them as standard.
some exterior situations with no risk of high UV. It is an excellent cost-effective solution for many designs, being tough, lightweight, aesthetically pleasing and available in a variety of colours and finishes – some manufacturers offer two or three standard colours in most ranges and other RAL colours as options, plus matt or polished finishes. Polycarbonate is tough and offers thermal stability so can be used across a very wide temperature range. It also offers excellent impact protection, heat resistance and is inherently flame retardant. Polycarbonate does not resist alkalis well, which needs to be taken into account in some industrial settings. Like other types of thermoplastics, polycarbonate does not conduct electricity, which makes it an excellent choice where there are concerns about electrical shorting or arcing and also for enclosures near water or exposed to the elements, so it is often used for electrical enclosure boxes. A more costly material than ABS, one of polycarbonate’s advantages is transparency, so it is often used for enclosure lids and doors where devices need visual inspection, sometimes with the main enclosure body in a different material. Polypropylene provides excellent resistance to detergents and chemicals. It is therefore a good choice for enclosures in clinical or scientific environments, but
Components in Electronics
as it provides lower impact strength and has higher thermal expansion at sub- ambient temperatures than ABS, which is far more robust and temperature-tolerant, polypropylene enclosures are less widely used in general applications. For laboratory or clinical environments however, polypropylene can be useful, especially for applications such as instrument cases which may need to be wiped down frequently.
Metal enclosures
Materials used for metal enclosures include die-cast aluminium, stainless steel and galvanised steel. Metal enclosures generally offer greater impact resistance, are more vandal-proof and for certain industrial applications, e.g., those using chemical processes, stainless steel
Examples of custom enclosures from BCL Enclosures
Die-cast aluminium alloy enclosures provide excellent EMI/RFI shielding and are easy to machine to suit individual applications – suitable uses include housing electronic instruments in industrial, commercial and agricultural settings. Often with lids which can be secured with screws, high-quality enclosures should feature lap-joint construction. Some ranges are also watertight, for example the 1590WP range from BCL Enclosures, which is available unpainted or with a satin black polyester coating that helps it blend into its surroundings.
Galvanised steel enclosures can provide tough protection against the elements for exterior electronic and electrical installations where security and guarding against tampering are considerations. A good example is the BEDS range from BCL Enclosures, which is IP66-rated and meets IK10 for impact protection, as well as having a 3-year corrosion guarantee.
Ideal for more specialised and demanding situations, stainless steel is the material of choice for corrosive environments, such as the chemical and petrochemical industries, plus others where strict hygiene is needed. BCL’s new BEDSS range for example, protects delicate components in environments that demand very high standards of security and cleanliness, such as hospitals, dental and veterinary practices and food manufacturing and is also available in marine-grade 316 stainless steel for installations subject to salt water.
www.bclenclosures.com
www.cieonline.co.uk
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