When considering which enclosure is suitable for an application, the basic enclosure is only the starting point. Manufacturers in industry are now choosing their suppliers on the basis of quality, operational life and added features such as service packages says Sando Selchow of Rittal.
Suppliers today need to offer quality enclosures that are ‘fit for purpose’ for a wide and varied array of applications from the banking world, food processing, ship building or rail and air travel through to the information kiosk, the car assembly line or the workstation in the R&D department. Within these applications, enclosures surround us and in many instances we are not even aware of their existence, but enclosures today need to be more than just an empty box.
Electrical enclosures, which are used in hostile environments such as the manufacturing process or refuse collection vehicles, are usually hosed down at the end of the day. Often high pressure cleaning equipment is used and the mechanical equipment or controls are included in this washdown. The enclosure to house these controls will need to withstand the effects of water being used in the cleaning process. Stainless steel enclosures are the ideal solution as they are corrosion proof but is enough consideration given to the protection rating of the enclosure?
More stringent cleaning methods are required within food processing plants where strong high velocity hoses are directed at machinery and their controls to prevent harmful bacteria from harbouring. The temperature in a process plant within a poultry factory could be around 10ºC ambient when in use, but when the cleaning process takes place, refrigeration is turned off, which allows the temperature to rise to 20ºC. The water temperature for cleaning is often higher than 50ºC and can have a water pressure of 100 bar. If the enclosure to house the controls was only rated at IP56 or 66 the control enclosure could fill with water, as the water temperature is far higher than the enclosure and the water pressure is greater than the design standard of the gaskets.
In these types of environments where enclosures need to be protected against any form of water ingress it is recommended that a sealed enclosure be used which meets the demanding standards of IP69K.
The German DIN 44050 standard originated from requirements found in the automotive industry where spray water and high pressure cleaning resistance was required. The IP69K protection category certifies the enclosure to be water ingress proof when tested on a turntable.
The IP69K to DIN EN 40 050 part 9/5.93 lists the IP (international protection) rating for road vehicles. The IP rating is described in a combination of the two numbers and an additional letter behind the last characteristic numeral. In this case this creates for example the IP69K, where the letter “K” provides further information. The letter “K” refers to a special case for road vehicles which describes the protection of electrical devices in road vehicles with regards to foreign bodies, dust and, in particular, with regard to the penetration of water. The use of the additional letter “K” is, however, no longer used exclusively in vehicular applications, but also in the food and beverage processing industries. As this test procedure differs considerably from the other IP-tests, enclosures with IP69K test certificates are currently the highest protection standard available against water ingress.
The IP69K to DIN40 050-9/5.93 lists the protection category test consisting of the following parameters: Water pressure up to 100 bar; 14-16 litres per minute flow rate; temperature up to 80°C; distance min 100 to max 150mm. Duration of the test calls for four directions and test jet time of 30 sec each at the angles of 0°, 30°, 60° and finally 90°. To achieve the 4 directional test, the test object is placed on a rotating turntable.
Protection class IP69K is therefore an important standard for enclosure systems used in the food industries. In addition to the water ingress properties, the food industry also requires hygienic standards on the surface properties. Standard 304-grade stainless steel achieves the required levels, but what about the gasket material? Special properties are required, such as a non-bacteria harbouring surface and a smooth transgression between the stainless steel parts and the gasket materials. The German Institute, “Frauenhofer-Institute IPA”, certified the highest standards in the food and hygiene sector for the IP69K enclosure range.
Standard sheet steel enclosures are easy to work with but will not always suit the environment where they are situated. Finishes used are aluminium-zinc primer coating and powder painted topcoat. Other material choices are GRP, aluminium or stainless steel. Stainless steel 1.4301 (grade 304), for example, would be suitable for a rural site such as a food and dairy processing plant or an industrial site such as a chemical or a pharmaceutical plant. The more aggressive environments situated near the coast or marine sites should consider 1.4401 (Grade 316) for better corrosion protection.
Outdoor enclosures should also have a high corrosion protection as well as a system in place to prevent condensation. A typical example would have a roof plate that is screw-fastened at the correct distance to allow for permanent air circulation.
The new Atex directives address the use of equipment in potentially explosive atmospheres to ensure the equipment supplied is appropriate for the zones in which it is to be used. Atex 100a is the product directive, which facilitates the movement of goods across the EU by harmonising this product standard.
Enclosures that meet the new Atex100a certification are imperative where explosions are possible, due to gas which can be ignited at low temperatures, along with the EN50014 labelling of explosion protected electrical equipment that are to be used in Zones 1 and 2.
These enclosure systems are necessary in zones of the world where seismic occurrences take place naturally and equipment needs to be housed in enclosures that protect against such an effect. The specification Zone 4 (Bellcore) Telcordia GR 63-CORE details the requirements to withstand a certain force of shock and vibration and the duration of time.
Electromagnetic Compatibility (EMC)
EMC means equipment used in an enclosure is protected from electromagnetic waves entering the enclosure and damaging the equipment. It also works in reverse: electromagnetic waves produced by equipment inside an enclosure are kept inside. An enclosure with doors or panels on all openings already provides a good start for EMC as it forms a basic Faraday cage. Effectiveness can be improved by using an EMC shielding enclosure range with special seal arrangements and contact clamps which guarantee continuity between the enclosure and mating parts.
When products are used in factories and applications around the world, common safety standards are set to make sure all the health and safety criteria are met. Enclosures are no exception; meeting the requirements of the EN60529 ingress protection and EN60439 low voltage control gear assembly standards.
In eight out of 10 applications standard-cooling systems (mild or stainless steel) that meet a protection rating of IP54 and provide closed circulation will suffice, however in all other instances the situation will call for more robust equipment incorporating features such as NEMA 4X protection or even an anti-corrosion internal finish.
In hostile environments such as hose down areas, coastal or offshore installations the requirement for protection against water in excess of IP56 is a usual prerequisite. NEMA4X offers users of enclosures in such environments the ideal solution as it offers high levels of protection against heavy water jets. The UL approved stainless steel NEMA 4X cooling systems provide this rugged, long-term solution due to a unique design that prevents heavy water jets (from any angle) from entering the condenser housing. The units also utilise refrigerant R134a allowing operation all over the world in temperatures as high as 55°C.
NANO & Corrosion Coating
In dusty environments the NANO coating protects the condenser fins of a cooling system from unwanted airborne deposits. The coating is offered by the leading suppliers and has been tried and tested in the automotive industry with excellent results. In environments where contaminants in the air can overtime destroy the cooling system’s internal parts, a treated cooling unit is the recommended solution. This treatment simply coats all ambient air-side components with an anti-corrosion coating which makes these units ideal for cooling enclosures in industries such as petro-chemical, pharmaceutical, oil & gas, food, and marine specific industries.
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