HUMIDITY Dehumidification explained
Humidity control via dehumidification is vital in so many sectors of industry. From the creation of charcuterie products, the storage and protection of classic cars or artefacts, through to packaging tablets and powders in the pharmaceutical sector – the applications are wide and varied as John Barker of Humidity Solutions explains.
S
pecialist application knowledge is key to selecting the correct dehumidifier – with either refrigerant or desiccant technologies –
for each project.
Refrigerant dehumidifiers operate by the air being passed over a cooling coil to drop the temperature below its dew point.
Extraction rates from 25 litres- 3000 litres/24hrs
can be achieved, depending on unit size, and this can either be via a fitted condensate pump or simply drained out via duct work. Some units may be placed on castors for portability, but more often are fixed wall mount models, or fixed bracket ceiling mounted versions, and even a through-the- wall solution.
Other attractive features include sound-proofed
compressors resulting in low operating noise, easy access panels and coated internal components to withstand aggressive environments. This opens up a huge variety of different, end-user applications to consider, from warehouse storage, protection and storage of documents or artefacts, a variety of manufacturing processes, through to swimming pool plant rooms. However, refrigerant dehumidifiers cannot operate at very low temperatures (below 1°C) – for this desiccant technology is required.
Desiccant dehumidifiers will operate at much lower temperatures than a refrigerant machine and will continue to extract moisture from the air even in very cold (sub-zero) conditions, although the air doesn’t hold much moisture under these conditions. Desiccant dehumidifiers use a silica gel desiccant rotor to remove moisture from the air, and are ideally suited to cold unheated environments such as storage facilities and cold rooms - where the temperatures could be as low as -10°C - to stop the humidity from dropping moisture on the cooling coils causing them to ice up, or to achieve very low humidity in applications such as in the pharmaceutical sector. Lithium-ion battery technology is a large, and growing, market and here very low humidity - and we are talking as low as -40°C dew point (0%rh) – may be required.
46 March 2020
Again, a large range of unit sizes are available, from small portable units through to large capacity semi-permanent installations placed in situ by crane, to provide a solution across all scenarios.
Investment vs Reward
Whilst investment in humidity control systems in any application will come at a cost, the benefits - and indeed in many cases savings – mean that this investment should pay for itself in the long term. The protection of rare books or priceless artwork and documents is clearly essential to preserve value for individual investors or national or even global organisations. Indoor trampoline parks, swimming pools and ice rinks in the leisure sector all require humidity control – and primarily dehumidifiers – to prevent mould, odours or unwanted dripping of condensation from the ceilings. Apart from potentially being unpleasant, water on the floor is a health and safety issue with all the potential costs associated with this. In food processing or storage areas, dripping condensation may carry bacteria from the food product again leading to serious health and safety issues.
Storage of documents, which could be paper or film, must be kept in the best possible condition. One application we have provided a solution for is the storage of geological data from the oil industry which is kept on film. Film that can turn brittle and be unreadable if the environment it is kept in is not closely maintained within tight parameters. To lose this data would equate to massive costs to re-survey.
Without appropriate humidity control cooling coils in cold rooms may frost up, using extra energy (therefore cost) and in turn affect the operation of machinery which has a knock-on effect on productivity and quality of a product.
Once installed the dehumidifiers do require some maintenance to ensure that the airflow through the unit is maintained at optimum rate, preventing pressure drops. A planned maintenance programme is generally recommended to secure the best continuity of quality of service from the equipment. Whilst sometimes seen by the end user as expensive, the benefits would override the
potential loss of not having the equipment regularly maintained. This loss could occur in many ways. Over time the air filters become dirty and the fans have to work harder to push the air through the dehumidifier. This takes more energy and creates more wear on the fan and fan motor, shortening its operating life. Unchecked, the system also becomes less efficient, resulting in a deterioration in production or the climate trying to be created. If left still further, the airflow could eventually cause the fan to stop or overheat which creates an equipment failure making the situation critical with loss of production or control of the humidity. Typically, an emergency call-out will cost more than a planned maintenance visit. We understand that in many sectors the humidity control system is often not used evenly throughout the year, being influenced by seasonal climates. All good maintenance providers would use their experience to adjust the timing of visits under a planned maintenance contract to reflect peak usage. An alternative is to use remote monitoring, where the maintenance company monitors the unit from their offices and provides the maintenance only when required. For instance, triggers for an alert may be where the pressure drop across the filters starts to increase or when a fault code is activated. At this point, it may only be a telephone call between maintenance company and site manager is required to re-set the equipment. If a service visit is required the engineer will have a much clearer idea of the issue and hence be carrying the correct spares on the van. Thirdly, and most importantly, the alert is raised before the equipment fails, and therefore the dehumidifier is kept running efficiently, saving costs on energy and ensuring the ideal conditions for the space being controlled thereby ensuring maximum profit is generated by maintaining quality, health and safety and production efficiencies whilst all but eliminating expensive breakdowns or failures. So, by selecting the most appropriate technology for your application, installing correctly and facilitating a good planned maintenance program, a system should provide you with excellent service at reasonable cost. Whatever your business, maintaining the environment at the required levels will help optimise productivity, quality and profit.
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