Contents and facts
The VDI 2047 Sheet 2 standard has been in force for evaporative cooling plants since January 2015. The standard’s objective is to ensure hygiene-compliant operation, where the materials used and the evaporative cooling plants’ mode of operation, along with the water circuit, are authoritative. The standard applies to new as well as existing recooling systems where water is mistified, sprayed or may come into contact with the atmosphere by other means. These systems include:
- Open wet cooling towers
- Wet cooling towers with a closed primary circuit
- Natural draught cooling towers with an output of 200MW
- Hybrid cooling towers
- Evaporative condensers
Plant operators are responsible for the hygiene safety of their systems and must observe building, technical and organisational measures to minimise risks. VDI 2047 specifies the requirements for a hygienically sound operation of evaporative cooling plants. Plant operators should observe the following obligations and measures, among others.
Based on legal framework conditions, evaporative cooling plant operators must compile a risk analysis and risk assessment or have one compiled, including hygienically critical places of the cooling system, which must be documented. The documentation must provide the following information:
- Plant diagram
- Materials used
- Treatment programmes
- Mode of operation
- Cleaning and upkeep intervals
- Water quality
- Assessment of the installation site
The extent and occurrence probability of the identified risks is to be assessed. In case the analysis results deviate from the standard, action plans should be compiled. The hazard assessment must be performed with an expert involved. The extensive specialist knowledge is evidenced by, among others, a certificate about a training compliant with VDI 6022 Type A or VDI 2047 Sheet 2.
Analysing the general colony count should be done monthly; analysing for legionella should be done at least every quarter. Analysing for pseudomonas aeruginosa will provide other important information and should also be included. Sampling is to be conducted by personnel qualified as per VDI 2047 Sheet 2; analyses should be performed by an accredited laboratory. Continuous monitoring and documentation of the water’s physical / chemical quality The following circuit water parameters should be determined at least every fortnight:
- pH value
- Electrical conductivity
- Total hardness (total of alkaline earths)
- Concentration of conditioning medium
- Total colony count
- Others, as required
With sufficient experience and consistent measuring results, you can stretch the testing cycle to up to two months. Analysing the general parameters is used to prevent deposits on surfaces of water-containing systems as they can impact the heat transfer, cause corrosion damage and contribute to biofilm build-up.
Periodic system inspections
Periodic inspections of the system by trained personnel can help to detect technical or hygienic flaws at an early stage to remedy them. They can include functional tests or visual inspections for mineral or organic deposits. The standard recommends compiling system-specific checklists with appropriate inspection intervals.