Enclosures - Hygienic enclosures: a consistent approach to cleanliness and food safety

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In industries where a clean and sanitary working environment is essential such as the food, beverage and processing industries, a strict hygienic protocol needs to be adhered to in order to prevent product contamination. In the constant battle to prevent cross contamination, which could have a disastrous negative impact on an organisation such as product recalls, reduced profits, tarnished reputations and loss of consumer confidence, daily washdowns of all equipment is paramount to protect product purity and quality. Glen Ward of Rittal explains

A daily washdown includes the enclosure housing the electrical controls to remove any particles that may be cultivating on the enclosure surface, crevices or recesses. Protecting the electrical equipment from daily washdowns while maintaining hygienic standards can prove to be a ‘hygienic headache'. Common problems that occur during the daily washdowns include solution pooling, the possibility of trapped contaminants between walls and mounted enclosures as well as the unreachable areas created by floor standing enclosures. Hygiene checks have also revealed that the use of pressure washes harbours the risk of organic contaminants entering niches and tiny recesses in standard enclosure designs such as the two-bit lock, hinges, seals and glands. However, these problems can be easily overcome if during the design phase the enclosure is properly specified.

To prevent any pooling from collecting on the roof area, an enclosure that incorporates a 30° sloped overhang allows cleaning fluids to completely drain away as well as stopping objects being placed on the roof which could potentially cause a contamination hazard. Ideally the slope at the back of the roof should be raised at an 8-20° angle over the door by 10mm to prevent liquids from reaching the door and seal. An increased gap between the door and the roof will offer easier cleaning and an bezzled door return will ensure that fluids do not run back and take residence on the seal.

A special silicone door seal should also be fitted - designed to protect against acids, alkaline solutions, detergents as well as disinfectants, and ought to have chamfered edge folds to prevent any liquid accumulation. The seal should be of a coloured variety to improve the visibility of particles that are then detectable with metal detectors. As the seal is subjected to a constant barricade of water the seal will need replacing on a regular basis. A one-piece replaceable seal is ideal as it is quick and easy to install as well as being gap free eliminating the possibility of bacteria forming within the small joins.

When it comes to the two bit locking mechanism, it was always difficult to tell if the recessed hole had been cleaned out completely. The solution has been to design a new hygienic lock that protrudes from the door surface, which contains no recesses eliminating the places where micro-organisims could fester while offering more reliable cleaning. The hinges on enclosures have also continued to provide a bacterial haven with the pin through the middle making it virtually impossible to keep hygienically clean, hinges that are mounted inside the seal remove it from the external environment therefore eliminating the potential hazard.
An area, which has until recently caused problems, has been the use of the traditional cable gland that has a number of design features making it unsuitable for hygienic environments, such as open screw threads and tiny recesses. To rectify this Rittal has introduced a new hygienically designed cable gland, which minimises the risk of deposits found in ‘open' production processes. Conventional cable glands contain various cavities and crevices where dirt and bacteria can gather; the new cable gland presents only smooth surfaces and gentle transitions, so dirt and micro-organisms have nowhere to congregate. A special feature of the new cable gland is the cap nut that extends all the way to the mounting surface, thereby concealing the entire clamping and sealing mechanism.

The mounting of the enclosure to avoid entrapment areas also needs careful consideration. Difficult to clean areas with floor standing enclosures can be eliminated by using adjustable levelling feet, with tubular threads, which support the enclosure while accommodating the floors drainage slope. For wall-mounted enclosures, tubular mounting brackets with a smooth finish will minimise entrapment areas. Open frame plinths with a clearance of 300mm designed from tubular stainless steel will also allow easy cleaning.

Enclosure mounting, seals, gaskets, and gland plates can also affect the IP rating and can often make the difference between the success and failure of the enclosure to meet its desired task. Typically, the more hostile the environment the enclosure is to be situated in, the higher the IP rating will need to be. For internal use where there is no likelihood of the enclosure being washed down, the IP rating could be as low as IP43. However, in an extreme environment, where the enclosure is subjected to a daily washdown, the internal equipment will need protection any form of water ingress so an IP69K enclosure will be required.

Established in 1993, the IP69K protection rating which is currently the highest available, was designed to address the high pressure, high temperature washdowns of road vehicles. As the cleaning method for these vehicles was quickly adopted by other industries, the IP69K enclosure was formed. When strong, high velocity hoses are directed at machinery and their controls to remove any remaining substances, it is important to protect the electrical controls, and if the enclosure were only rated at IP66 it could quickly turn to disaster. For example: the temperature in a processing factory could be around 10°C ambient when in use, but when the cleaning process takes place the refrigeration is switched off allowing the temperature to rise to 20°C. The water temperature for high velocity cleaning is often higher than 50°C and can have a water pressure of 70 bar. As the water temperature is higher than that of the enclosure and the pressure is greater than the design standard of the gaskets, the enclosure would soon begin to fill with water.

IP69K enclosures are subjected to a rigorous test before they receive their certified rating. The test consists of: water pressure up to 100 bar, 14-16 litres per minute flow rate; temperature up to 80°C; distance minimum of 100mm to a maximum of 150mm. The duration of the test calls for four directions and test jet times of 30 seconds each at an angle of 0°, 30°, 60° and 90°.

So how is IP69K different from UL Type 4? IP69K and UL Type 4 standards both require the enclosure to protect against the entry of water, but Type 4 test is mainly concerned with hose down conditions involving lower pressure water at a greater distance (10-12ft) and with a greater volume of water (65gallons/minute).  IP69K certification requires close range, low volume with very high pressure, which is similar to the type of washdowns found in the pharmaceutical, petrochemical and food and processing industries. IP69K is therefore an important standard for enclosure systems used within any environment where the equipment is subjected to high pressure cleaning.

Every industry faces its own challenges and the food and processing industry is no exception. However, the latest hygienic thinking has now been applied to the electrical enclosure packaging field, which can significantly reduce the contamination risk, facilitating in this constant battle. These new developments allow greater system availability, more efficient cleaning and lower energy requirements due to the reduced use of chemicals. With careful consideration when choosing an enclosure, a lot of the common problems in hygienic environments can be easily overcome.