Water treatment and Humidity Control

Reverse Osmosis (RO) is a water purification process that uses a partially permeable membrane to separate ions, unwanted minerals and larger particles from mains water. The sequence to produce fully treated water is to pass the mains water through a water softener to remove the hard calcium and to replace it with sodium – this helps to prevent hard scale from blocking the reverse osmosis membranes. Carbon filters would then remove the chlorine from the water – chlorine ‘eats’ the membrane which reduces the membrane lift significantly. RO differs from filtration in that the mechanism of fluid flow is by osmosis across a membrane as opposed to straining through a membrane filter. It is possible to use the RO plants without the softener or carbon filter, depending on the application.

Using Reverse Osmosis to remove the minerals from a humidifier’s supply water, virtually eliminates all limescale that would otherwise build up, and results in much lower levels of maintenance required and energy consumption.

Resistive

The Resistive steam humidifier on the other hand, uses technology much like in your kettle at home. It has a heating element which physically boils the water within a stainless-steel internal chamber. Because of this, these units are able to run on mains or RO water as there is no electrical current required to pass through the water. If RO is used then this can drastically reduce the maintenance requirements as very limited scaling will occur, and greatly improve the unit’s working lifespan. By using resistive steam humidifiers fed by RO water, ±1%RH control can be achieved. This is because the humidifier does not have to drain and refill with cold water – a process used to manually reduce the mineral build up in the cylinder. This helps the unit maintain the boiling temperature which, in turn, maintains steam output and control.

Due to the nature of this technology, it has a higher capital cost but then very few consumable item costs going forwards. This unit is ideal for close control test chambers and laboratories, or on critical sites where production demands consistent output and close control.

Adiabatic/Ultrasonic

To complement our isothermal (steam) humidifiers, we also have a wide range of cold water systems using both High Pressure Adiabatic (cold water) and Ultrasonic technologies. Rather than producing steam, these technologies produce a fine spray or misting effect to reach their required humidity levels which drastically reduces their electrical requirements consumption and costs, making them very attractive for many projects.

In the case of the spray adiabatic humidifiers, the water is raised to a high pressure and distributed through hoses to nozzle outlets that then disperse the fine atomised spray. The nozzles are robust but mineral dusting can occur as the minerals precipitate out of the atomised water. In most applications this is not an issue, however in digital printing and electronic production reverse osmosis water may be required to prevent this effect which could affect production if not considered.

Ultrasonic humidifiers, on the other hand, have internal oscillators that ‘vibrate’ the water into a fine mist that can be dispersed into the space. If these units are run on a mains water supply, once the water molecules have been dispersed then the mineral particles are left behind and create scale which will reduce oscillation and reduce production of mist/moisture. RO water is therefore required with these units.