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Cooling Towers

Recooling plant conceptual solution

Concept for water hardness monitoring in cooling towers and other industrial applications

1    Pre-filter
2    Softening system
  Control Softmaster MMP1
4    Hardness monitoring Testomat® 2000/ECO
5    Chlorine monitoring Testomat® 2000 CLT/F
6    Bromine monitoring Testomat® 2000 Br

  Phosphate monitoring Testomat® 2000 PO4
8    Polymer monitoring Testomat® 2000 Polymer
9    Control of biocide dosing MultiControl CT
10    Conductivity probe
11    Motor valve
12    Plate heat exchanger

13    Biocide
14    Polymer
15    Phosphate
16    Bromine
17    Chlorine

Control and monitoring of recooling plants


Today, cooling water controlling and monitoring are indispensable components of advanced energetic and

hygiene-compliant operation of cooling towers according to VDI 2047-2 and VDI 3803-3.4.

A wide variety of recooling plants exists worldwide:

  • Closed cooling systems

  • Semi-open cooling systems

  • Continuous flow cooling systems


More than 100,000 recooling plants of the above categories are installed in Germany.

What is the responsibility of the plant operator according to the new VDI 2047-2 directive?

Industrial cooling systems, including recooling plants and cooling towers, rapidly dissipate excess heat from production processes and buildings. Despite economic and hygienic enhancements in recent years, malfunctions due to deposits, corrosion, or legionella persist, often spreading swiftly due to their design.

Prompt action remains crucial for operators of evaporative cooling systems to prevent mineral-based, corrosive, and biological accumulations like legionella and pseudomonads. To address this, the legislature introduced VDI 2047 Sheet 2, known as the VDI cooling tower rule, which mandates specific hygiene-compliant operation duties, particularly in legionella prevention.

Plant operators are urged to acquaint themselves with VDI 2047-2, as disregarding these operator duties may result in legal consequences. Ensuring trouble-free, economical, and hygienic cooling tower operation in line with the new directive requires continuous water monitoring and system conditioning.

What are the main focuses of monitoring


In cooling systems – open, semi-open, or closed – evaporation is inevitable, elevating salt concentrations in circulating water. The heightened salt and mineral levels trigger limescale accumulation, corrosion, and mineral deposits within cooling towers and circulating water systems. This particularly affects drip collectors, trickling filters, distribution channels, and heat exchangers. The issue is exacerbated by biological challenges, including algae and biofilm formation from supply water and ambient air.

Addressing this, VDI 3803 mandates adapting circulating water condition to cooling circuit materials, crucial for averting corrosion, inorganic deposits (like calcium and magnesium carbonates), and organic deposits (algae and bacterial strains), known as biofilms. Biofilms aren't just potential fittings and pump obstructions; they also serve as breeding grounds for harmful legionella and pseudomonas bacteria, posing risks to human health.

Remarkably, biofilms and mineral deposits like calcium or silicate have comparable energy impacts. A mere 1 mm biofilm layer or mineral deposit leads to a 30% loss in efficiency, translating to up to 12% increased energy costs.

In conclusion, a monitored online cooling tower system operates hygienically (VDI 2047-2 compliant), efficiently, and malfunction-free (VDI 3803 compliant).

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