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How to deal with potentially damaging condensation

How to deal with potentially damaging condensation The use of panel mounting dessicators will not only extend the operating life of equipment, but can also help in extending the safe working environmental limits in which the equipment can work.

Water and humidity are the constant enemies of equipment cabinets - or rather their contents - whether they be electronic racking cabinets, electrical wall-boxes, outdoor plant housings or any other variation on the theme. That means moisture control is critical.

Concern over two trends means that moisture control 'tools' for cabinet and housing designers are becoming even more important. Firstly today's advanced electrical and electronic components can be more sensitive to moisture levels than their predecessors. And the second factor is that moisture control is too often regarded as an inexact science.

There are two prime methods of moisture reduction, for two types of moisture control needs. Molecular Sieve desiccators are extremely efficient at extracting water vapour from the atmosphere. They are designed for applications where virtually dry atmospheres are essential for component protection, preventing the likes of electrical short-circuiting, insulation breakdown, visibility loss and construction materials instability.

Atmospheric moisture levels may be critical so units incorporate an indicator showing when the desiccant is reaching, and has reached, its adsorption capacity. The one disadvantage with molecular sieve desiccators is that the desiccant itself cannot be reactivated.

Silica gel based desiccators are more general purpose. Their moisture adsorption rate is not as powerful as that of molecular sieve types. The desiccant can be reactivated by oven-drying and cooling in a container sealed to prevent the crystals adsorbing moisture during cooling. An indicator shows that the silica gel is adsorbing moisture and when reactivation is due.

Brownell silica gel desiccators are designed for protection against corrosion and mould growth hazards in electrical and electronic equipment, or indeed, any storage container the contents of which would deteriorate with dampness. Brownell's plastic units use powerful adsorbing agents, either silica gel or molecular sieves. The built-in saturation indicators are blue when the humidity adsorber is dry and turn pink when the maximum amount of moisture has been adsorbed.

The silica gel adsorbers can be reactivated for re-use, by heating them at 100ºC for 4 hours in a ventilated oven. Molecular sieve adsorbers maintain an ultra-low relative humidity for extremely sensitive applications and cannot be reactivated. These are particularly useful for equipment operating under extreme temperature conditions, as molecular sieves can eliminate any moisture dropout.
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