is my cooling tower clean?
If you are involved in the legionella risk control programme for your organisation, especially if you are the duty holder or responsible person, you need to know that you comply with HSE guidance and Health & Safety Legislation.
If you operate a cooling tower or evaporative condenser, this is particularly important due to the high-risk nature of these systems. You need to be aware of the guidance document from the HSE:
The Legionnaires’ disease Technical guidance
Part 1: The control of legionella bacteria in evaporative cooling systems
You can download a copy here
https://www.hse.gov.uk/pubns/books/hsg274.htm
It is a legal duty to control the risk of exposure to legionella bacteria. As legionella are more likely to grow in a cooling system fouled with deposits, maintaining system cleanliness and the water in it is an essential part of the control regime.
Legionella are more likely to proliferate in water systems that are fouled with deposits and biofilm; these can protect the organisms from water treatments and provide nutrients for them to multiply. Maintenance of system cleanliness is therefore crucial.
HOW OFTEN SHOULD I INSPECT MY SYSTEM?
It is necessary to inspect parts of the cooling tower system regularly to determine the cleanliness, the need for cleaning and the type of cleaning process required.
Task | Frequency |
Check system is operating as described in the operations manual | Daily |
Visual check of the cleanliness of the water in the system | Daily |
Physical condition of the system | Weekly |
Undertake dip slide analysis or equivalent testing | Weekly |
Ensure effectiveness of water treatment regime | Refer to Table 1.9 |
Central control function, conductivity sensor calibration, blow-down function | 1–3 monthly, according to risk |
If accessible, uniformity of water distribution, condition of sprays, troughs, drift eliminators, pack, base tank and fans | 1–3 monthly, according to risk |
Cleaning and disinfection procedures | As determined by risk assessment |
HOW OFTEN DO I NEED TO CLEAN MY COOLING TOWER?
The following timescales, though not prescriptive, can be considered typical for different situations:
- at least every three months for a cooling system in a dirty environment
- at least twice a year for an air conditioning comfort cooling system
- at least every 12 months for a ‘clean’ industrial application (and any others)
HOW CLEAN IS ‘CLEAN’?
There is a lot of helpful information in the guidance document such as:
