The use of softening systems with HygroMatik heater type steam humidifiers

Background:

Drinking water contains minerals in more or less high concentrations, which usually precipitate when heated. In order to keep the cleaning effort of the steam humidifier as low as possible, there are two possibilities for water treatment:

• • Operation with deionised water from a reverse osmosis system with approx. 3..20 μS/cm residual conductivity (full desalination)

Result: almost no minerals are deposited here, as about 99% of them are removed from the water, the humidifiers are operated with extremely low maintenance

• • Operation on soft water from a softening plant with a residual hardness of 0 °e (full softening)

Result: Minerals can be deposited here, but these are usually not hardness formers, so that although salt deposits occur more frequently, they can be rinsed out via an increased blowdown rate before they are deposited as incrustations of the heating elements or on the cylinder base and walls.

Explanation:

In a health centre HygroMatik test units StandardLine Heater have been running since 2015: here, we were essentially concerned with experiences with new heaters, which have since been incorporated into series production. At the same time, a test operation was set up here on a single softening system to determine experiences with the effect on the service life of heater type humidifiers and the extension of the maintenance cycles during operation on soft water with positive results.

The two pictures of the opened cylinder of the StandardLine Heater field tester and the 3 heating elements after about 2 tons of steam produced at about 2/3 Ø load look almost unused:

• • The Incoloy heater elements show no deposits
  • The lower part of the cylinder is very clean and shows only minimal deposits

These experiences from 2016 have since been confirmed during the regular inspections.

The water quality in the health centre is in the "hard water" range, with a total hardness of 18,8 °e, a carbonate hardness of about 26,3 °e and a conductivity of about 850 μS/cm. The minerals present in the water precipitate during evaporation and usually collect on the hot surfaces or sink to the bottom. On average, about 400 to 800 mg/l dry residues can be expected in "hard" water, which would correspond to about 0.4 to 0.8 kg of deposits in the cylinder per ton of unpressurised steam produced, depending on the set blowdown.

Conclusion:

In our estimation, softening can often significantly reduce maintenance costs compared to operation with drinking water, and at the same time the investments are usually significantly lower than those for a reverse osmosis system including softening. If required, we would be pleased to support you in the selection of a technical-economical solution for optimised operation of steam humidifiers.