VDI 2047

Hygienically safe evaporative cooling systems 

VDI 2047 is a technical guideline for the hygienically safe operation of evaporative cooling systems and cooling towers. It outlines measures to prevent the growth of Legionella, as well as requirements for the design, water treatment, monitoring and maintenance of cooling systems. In open cooling circuits in particular, microorganisms can multiply due to elevated water temperatures, nutrient inputs, deposits and biofilms. If contaminated aerosols are released, there is a health risk to people in the vicinity of the system. VDI 2047 assists operators in identifying hygiene risks at an early stage and ensuring safe and compliant system operation.

Water treatment in accordance with VDI 2047

Water treatment plays a key role. The aim is to provide long-term control over corrosion, scaling and microbial growth. Hygienically safe and cost-effective operation can only be guaranteed through consistent water quality.

Common measures include:

• Filtration of the circulating water
• Softening or partial desalination of the supplementary water
• Controlled desalination to limit concentration
• Dosing of biocides, corrosion inhibitors and hardness stabilisers
• Continuous monitoring of water parameters

Key operating parameters such as conductivity, pH, temperature, concentration factor and biocide concentration are continuously monitored and documented. Modern measurement, dosing and monitoring systems allow automated control of water chemistry and contribute to ensuring stable operating conditions over the long term.

Risk assessment and hygienic concept

A key component of VDI 2047 is the hygiene-related risk assessment. Operators must assess the facility for hygiene-related risks and define appropriate measures to minimise those risks.

Among other things, the following aspects are taken into account:

• System design and water flow
• Areas with potential for stagnation
• Aerosol formation and dispersion
• Temperature ranges with an increased risk of Legionella
• Maintenance and cleaning options
• Operating mode and downtime

Individual hygiene concepts, monitoring intervals and action plans are defined on the basis of the risk assessment. The aim is to identify hygiene risks at an early stage and manage them preventively.

Operator responsibilities and monitoring

VDI 2047 requires regular inspections, microbiological testing and comprehensive documentation of all relevant operational data. Operators must ensure that the facility is operated at all times under hygienically controlled conditions.

Key operator responsibilities include:

• Performing regular visual checks and inspections
• Microbiological testing of the circulating water
• Legionella analyses by accredited laboratories
• Documentation of all operational and maintenance data
• Training and instruction of operating staff
• Regular cleaning and maintenance of the system

The guideline also sets out requirements for sampling and the evaluation of microbiological findings. If elevated Legionella concentrations are detected, graduated immediate, causal and corrective measures must be implemented. Consistent monitoring helps to identify hygiene risks at an early stage, ensure compliance with limit values and avoid unplanned system downtime. At the same time, comprehensive documentation supports the provision of evidence to authorities and reduces liability risks for operators.

Cleaning and maintenance

Regular cleaning and preventive maintenance are essential components of hygienically safe system operation. In particular, biofilms, sediments and deposits promote the growth of microorganisms and can significantly impair the efficiency of the system. VDI 2047 therefore recommends defined cleaning and maintenance intervals, as well as regular inspection of all hygiene-relevant components. These include, in particular, cooling tower filler bodies, droplet separators, pipework, collection tanks and dosing systems.

Efficiency and operational reliability

Apart from hygiene safety, water treatment that complies with standards also improves the cost-effectiveness of evaporative cooling systems. Reduced scaling and corrosion ensure more efficient heat transfer, lower energy consumption and a longer service life for system components.

Consistent water chemistry also reduces maintenance requirements and increases the operational reliability of the entire system. Modern monitoring and dosing systems enable resource-efficient operation with optimised water and chemical consumption. VDI 2047 is now regarded as an important standard for operators, designers and plant manufacturers of cooling systems. In conjunction with the 42nd BImSchV, it makes a decisive contribution to the hygienically safe, efficient and long-term reliable design and operation of evaporative cooling systems.