Humidification units

The humidification unit as proposed by the Getty Conservation Institute (see below) showed the drawback that it bubbling of gas through a water tank consumes a lot of pressure. In addition the high price of the components seemed a problem. Therefore we developed a low-tech version, which in the meantime has proven perfecly functional.

The functional principle is based on the principle of the separated air stream (cf. the device of the Getty Conservation Institute). The dry air stream from the air separator or from the nitrogen bottle is divided by a T-piece: The first gas flow passes through the humidification tank, the second gas flow remains dry. Both gas flows will be mixed by the spherical valve, till the desired relative humidity is achieved. To measure the relative humidity a hygrometer will be introduced into the upright tube.

Unlike the Getty device the air stream doesn't bubble through water but is led through the tank saturated with humid air. For this we fill the 30l tank with approx. 10l water (up to the maximum mark) and put a evaporator mat of a humidifier into the tank. The evaporator mat soaks up the water and consequently generates an enormous evaporation surface. Two tubes lead the dry gas flow into the tank slightly above the maximum mark. On its way throught the water tank the gas flow is loaded with humidity. A droplet collector is not neccessary.

We chose a relatively big water tank with 30l to make sure the water level hardly changes. Furthermore the evaporation will only slightly cool down the water, so temperature almost remains constant. Practical tests showed humidity to remain fairly stable during use, even at low water level.

The only major factor affecting RH is gas pressure. If you work with a tank of pressurized air which fluctuates beween e.g. 6 - 8 bar RH will fluctuate between two extreme values as well. In this case you should set the humidification unit in a way the extreme values will be at equal distances from the desired RH value.
If you use a nitrogen generator with constant supply of nitrogen at constant pressure (like the NitroFlowLab) humidity will remain constant as well.

Water can be re-filled through the valve in the center of the cap without air entering the tank. A 1 l-bottle with hose connector will be provided along with the unit.

The evaporation mat should be replaced every 3 - 6 months depending on water hardness. If you use demineralised water the evaporation mat can be used for a longer time.

Humidification unit as proposed by the Getty Conservation Institute. Including 2 Kobold flow meters, a 30 l water tank and a 10 l water droplet catch.
Inner diameter of the hose: 6 mm (to fit to tent coupling as you see on the photo), with adaptor for the pressure regulator of the nitrogen bottle and T-connector for RH measurement.