TECHNOLOGY IN ACTION THE ART OF CHOOSING THE RIGHT ENCLOSURE BOXING CLEVER E very contractor correct specification
and installer understands of
electrical enclosure or the importance of electronic equipment,
according to Hellermann Tyton, the same attention to detail is not always paid to choosing the right enclosure. As Chris Edwards, product manager for
solutions, explains, there are a
number of factors that need to be taken into account to get enclosure specification right for the job.
When dealing with sophisticated electronic and electrical systems, the importance of accurate specification goes without saying, but one area of an installation that sometimes gets overlooked is enclosures. However, enclosures should be considered as an integral part of the installation and chosen with equal care as their failure could compromise the performance of the system. If an enclosure is regarded as simply an off-the-shelf commodity,
temptation is to buy simply on price rather than performance, but low price can mean low quality - leading to poor performance.
There are three key areas to be considered when specifying an enclosure: materials, IP ratings and thermal management. Choice of material clearly has a bearing on the degree of protection afforded by the enclosure and different materials
have both advantages understand what these are.
Mild steel is the most widely used material for general-purpose enclosures and is generally regarded as the most cost effective. Mild steel is an ideal material for fabrications, hole punching and forming and is easily welded to form permanent bonds. The downside of mild steel is that it offers little in the way of corrosion resistance, making it largely unsuitable for outdoor applications or installations in a corrosive environment without some form of surface coating.
As an alternative, stainless steel is capable of withstanding more aggressive environments and can provide a suitable solution for outdoor applications. In some applications, such as food manufacturing, processing and pharmaceutical production it offers additional hygiene benefits and is commonly used where hyiene, cleanliness and corrosion resistance are important. Stainless steel offers a number of other advantages: it does not deteriorate when exposed to ultra violet light, it is a low-maintenance material and it may be less expensive than surface-treated mild steel. In choosing stainless steel, however, it is important to get the correct grade of stainless. Standard stock enclosures, covering the majority of industrial beverage and dairy industries, are made from grade 304. If the operating conditions are more demanding, such as a highly corrosive salt- laden environment, grade 316 would be specified.
Cost is one consideration when choosing a steel enclosure but it is far from the only one. Steel enclosures, such as the Hellermann Tyton XS 1000 range, offer a choice of specifications according to the many variables that can apply to an installation, such as location, type of environment, method of mounting, weight of internal equipment, risk of physical damage, security and safety requirements.
An alternative to steel is GRP – glass-reinforced plastic – as featured in the Hellerman Tyton XP range. The mechanical properties of GRP include good insulation, strength, hardness and stability over a temperature range between -50°C to +150°C. It is a self-finished material and, although once deemed expensive, has
now become a cost-effective solution in a number of
applications. GRP is resistant to mineral acids, oxidants and reducing agents, neutral and acid solutions, greases, oils and some alcohols. It also offers an electrical advantage in that, as an excellent insulator, it can offer protection from electric shock. Where busbars are fitted, use of GRP enclosures may allow a reduction of the clearance between bars and the enclosure, minimising space required. GRP is also self-extinguishing and significantly reduces the risk of fire. Some GRP enclosures are halogen-free and so are ideal for ue in areas where public safety is paramount.
As well as material choice, a key consideration for the specification of an enclosure is its IP rating. IP ratings are defined in the IEC 60529 standard for degrees of protection provided by enclosures, published in the UK as BS EN 60529. Degrees of protection are specified by the letters IP followed by two or more digits. The first digit, a number 1 to 6, reflects the degree of protection for intenal components from the ingress of objects, plus the protection of
persons against contact with live parts of the equipment within the enclosure. The second digit, a number from 1 to 8, relates to the protection of equipment within the enclosure against harmful ingress of moisture, caused by spray, drips or immersion.
It is important to avoid opting automatically for a higher IP rating in the belief that this reflects a higher performance, because this may mean that the enclosure will not do the job required in that particular application. For example, an enclosure may pass the test for a high level of protection against ingress of water but when installed may be subject to environmental conditions that could cause rusting or damage. To ensure that the choice of enclosure is both cost-effective and provides the performance required, it is important to understand the conditions and environment in which the enclosure is situated. You should also remember that IP ratings refer to the ability of an enclosure to pass the tests under controlled conditions, not its ability to withstand additional influences such as weather conditions, corrosive environments or extreme temperatures.
Another issue contractors and installers should consider is thermal management. All electrical or electronic equipment works best at the manufacturer’s recommended ambient temperature. A failure to maintain this could cause malfunction of the equipment and could make any warranty on it invalid. The simple addition of a thermostat in conjuction with a fan or filter – even a heater in cold conditions – is also worth considering.
In every installation, enclosures have a specific function to perform and failure could have costly implications for the system they are supposed to protect. Choosing the right enclosure for the right application is, therefore, essential. It should not be a decision that is driven by price, but one that takes into account all of the factors that could affect the ongoing performance of the enclosure.
and limitations, so it is important to the
HellermannTyton Tel: 01922 458151 Web: www.hellermanntyton.co.uk
enter 700 WINTER/SPRING 2014 Enclosure & Panel Building Solutions
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