Definition

During heating/evaporation, dissolved minerals (mainly calcium carbonate and magnesium hydroxide) precipitate as a hard layer on hot surfaces; this directly reduces humidifier efficiency and equipment life.

Detailed Explanation

Scaling — the precipitation of minerals on a hot surface — is a natural consequence of steam humidifiers. As water evaporates, the dissolved-mineral concentration rises; when it exceeds saturation, calcium carbonate (CaCO₃) and magnesium hydroxide (Mg(OH)₂) precipitate as a hard layer. It builds on heating-element surfaces (resistive), electrode surfaces (electrode), cylinder/tank walls and drain piping.

Why It Matters

Scale produces three main problems: (1) HEAT-TRANSFER LOSS — a 1 mm layer on a heating element lowers heat transfer 15–20% and reduces capacity. (2) CURRENT INSTABILITY — when electrodes are scaled in an electrode system, conductivity becomes irregular and current control suffers. (3) MAINTENANCE BURDEN — cleaning is done with acid (5–10% citric), each clean takes 30–90 min of technician labour; on hard scale, mechanical scraping or part replacement is required. Preventive measure: hardness monitoring + suitable pretreatment (softening, RO).

Practical Example

A printing plant in Ankara fed an electrode humidifier with 28 Fr° hard mains water; 6 mm of scale + alkaline deposit built on cylinder surfaces in 4 months and capacity dropped 40%; annual cylinder-replacement cost reached €8,500. NKT analysis showed high hardness + high alkalinity (LSI +1.4 aggressive scaling). The solution: a softener (hardness lowered to 4 Fr°) plus a resistive Neptronic SKE4 (stainless chamber, tool-free cleaning). Afterwards, 1–2 chamber cleans per year and zero cylinder cost.

Engineering Note

Scaling rate ≈ (hardness × capacity × runtime) / drain ratio. Soft water (<5 Fr°) plus adequate drain (20% tank refresh every 50–100 hours) keeps annual cleaning to once. Medium hardness (5–15 Fr°) needs 2 cleans per year; very hard (>20 Fr°) requires 4+ cleans per year or softening. Acid cleaning procedure: stop unit → drain tank → 5% citric acid for 2 h → brush → rinse → recommission. The manufacturer's cleaning instructions for the steam tank and heating elements must be followed.

NKT Application Link

For this application NKT – Nem Kontrol Teknolojileri supplies the Neptronic SKE4 resistive steam humidifier and the Neptronic SKS4 steam-to-steam humidifier. Unit-selection support is based on space conditions, humidification load and the feed-water analysis; technical service and spare parts are provided. Design and installation of water treatment, as well as engineering design, installation and commissioning, remain within the scope of the facility's designer, contractor and water-treatment specialist.