How do cooling towers work?
Cooling towers and evaporative condensers are used in a wide variety of commercial, industrial and process applications. They are designed to transfer heat away from a manufacturing or industrial process or an internal environment as efficiently as possible and then disperse that unwanted heat energy in to the atmosphere. Cooling towers do this either by allowing the water used as part of its cooling system to evaporate, thereby releasing energy, or by using air to cool the working liquids.
Where are cooling towers used?
Cooling towers and evaporative condensers are typically found in power stations, petrochemical plants, oil refineries, data centres, hotels, offices and other commercial buildings and manufacturing facilities. The size of the towers varies hugely, from small compact units which sit on the roof of an office or factory to huge, free-standing hyperboloid towers typical of power stations, which can be up to 200 metres high.
Large concrete hyperboloid cooling towers.
Maintaining thermal performance and reliability
As with any structure or item of plant or machinery in a factory or business, cooling towers should be inspected regularly to ensure that they continue to perform in the way intended. Deteriorating components and equipment can soon start to impact on how efficiently your factory processes or business is operating, and a cooling tower which has totally failed could shut down production entirely.
Legionella control and ACOP L8 compliance
Another significant consideration that must be fully addressed is the health and safety dangers posed by dirty and poorly managed cooling towers. Towers and evaporative cooling systems have been implicated in several significant outbreaks of Legionnaires’ disease, a serious, potentially fatal lung condition. They are considered high risk by the Health & Safety Executive and special precautions need to be taken.
Because of this there are strict tower registration and legionella control requirements in place designed to protect the safety of employees and others and these must be followed. Failure to do so could have serious consequences and may lead to prosecution and significant fines for owners and operators of cooling towers.
Expert cooling tower inspections
The experienced and skilled engineers at Water Treatment Services can be called on to inspect, maintain and service your cooling towers, whether on an on-going basis, to pick up on any issues which could develop into a major problem, or because a situation has occurred which has required the towers to be shut down.
During a cooling tower inspection, our engineers will look at the integrity of the tower structure as a whole, they will also examine the internal components and cooling water systems and how these are treated. Additionally they will review the overall performance and heat transfer efficiencies of the tower to ensure it is operating safely and effectively.
Our engineers typically take photographs as part of the initial inspection process, and feedback all results to the client in a comprehensive written report. The client can then use this information to target where they should be concentrating repairs, or highlight any areas in the cooling tower which are a cause for concern and require further action.
Why is cooling tower maintenance important?
Cooling towers are there to do one job only – provide cooling. Should your cooling tower fail because of poor maintenance, then the entire business operation could be compromised, especially if the cooling is critical to a manufacturing process or required to provide environmental temperature control.
Regular cooling tower maintenance will also improve operational efficiencies and prolong the lifespan of your towers, avoiding the need for a costly replacement until absolutely necessary.
Effective tower maintenance procedures will also minimise the risks of bacteria growing in the cooling water systems. Legionella, the bacteria responsible for the potentially deadly respiratory condition, Legionnaires’ disease is often linked with water cooling towers which are considered a high legionella risk. Legionnaires’ disease can be fatal, and companies which have or operate cooling towers on their premises have a legal obligation to register them with their local council, and to monitor and maintain their cooling towers to protect public health.
How to register cooling towers with your local council
Under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992, if your building or site uses a cooling tower or evaporative condenser you need to write to your local council to tell them about it. The only exceptions to this are when the tower contains no water that’s exposed to the air, or the water or electrical supplies have been disconnected. Additionally, if you make any changes to the tower you also need to write to your council straight away.
What are the legionella laws for cooling towers?
Cooling towers and evaporative cooling systems have been implicated in a number of serious outbreaks of Legionnaires’ disease and are considered by the Health & Safety Executive to be high risk. To control the risks from Legionella bacteria tower owners and operators must assess the risks posed and implement suitable precautions to protect employees and others from harm. The HSE’s Approved Code of Practice ACOP L8 and their supporting health and safety guidance document HSG274 Part 1 provides clear instruction and advice on what measures need to be taken. Both documents are essential reading for any duty holder, responsible person, owner or operator of a cooling tower.
Maintaining energy efficiency and optimising costs
In addition to the important public health aspects, studies have shown that a water cooling tower which is poorly maintained can become energy inefficient, costing you money. Energy costs rise by approximately 5% to 6% for every degree Celsius more in temperature. Therefore, keeping up with a maintenance programme on your cooling towers could save around 15% in your annual energy costs, partially offsetting the cost of doing the maintenance in the first place.
What does cooling tower maintenance and servicing involve?
The first step in any good cooling tower maintenance and servicing programme is to take stock of what type of cooling towers you have, how large they are, how old they are, system volumes, cooling loads, general cleanliness and a whole host of other factors.
There is no one “correct” maintenance regime for a cooling tower, and each business will have to develop their own maintenance procedures based on their specific circumstances. There are however some standard elements which usually form part of any cooling tower maintenance schedule.
First, our cooling tower engineering specialists will take an overview of the cooling units as a whole, looking for any obvious issues which might have arisen since the last inspection. Before taking a closer look at the tower, safe access must be provided and everything must be switched off and disconnected to ensure the safety of the maintenance team.
The team can then clear away any debris which has accumulated in the filters and tower pack, check for cracks and splits and look for moss, slimes and the build-up of scale. Once these visual inspections are complete, the team can then move onto checking the water supply level, flow control valves and filters, gear box and the performance of moving parts such as shaft bearings and fans; look for problems with tension and check oil levels if appropriate.
The frequency of maintenance will often depend on the type of cooling tower and how often it is used, but in many operations it is typically carried out quarterly. Record keeping is also an essential part of the maintenance process and noting down exactly what was done and when can keep you on the right side of the law when it comes to health and safety legislation, and in particular the control of Legionella bacteria and compliance with the HSE’s ACOP L8.
Water testing of cooling towers
Even though maintenance and servicing might be a quarterly activity, your ACOP L8 legionella control procedures will require more regular testing of the water flowing through your cooling towers.
Microbial testing of cooling water
The UK’s Health and Safety Executive recommend that microbial testing for general levels of bacteria in cooling towers should be carried out weekly. These tests can be done using dip slides and an incubator which will help to give tower operators a good indication of the overall cleanliness of the cooling tower waters and if they are under microbial control.
However, you should remember that dip slide testing at monthly or longer intervals will not pick-up rapid increases in microbial growth that can occur during the late spring to early autumn. This is when temperature conditions are more favourable to the growth of Legionella bacteria.
Laboratory legionella testing for cooling towers
Routine laboratory legionella testing of cooling tower waters should be carried out at least quarterly, but more frequently under certain circumstances including:
- Identification of potential sources of bacteria during an outbreak of Legionnaires’ disease
- When commissioning a cooling tower or establishing a new or modified water treatment programme. Here testing should initially be carried out weekly and the frequency reviewed when it can be shown that the cooling tower system is under control.
- If a legionella-positive sample is found, more frequent testing may be required as part of the review of the system risk assessment, to help establish the source of the contamination and when the system is back under control.
- Where the legionella risk assessment recommends more frequent legionella testing is needed, for example if the tower is located close to a hospital or care home (susceptible populations).
Often, a complete shut down is not required for water sampling to take place. Best practice is that the legionella sampling is done at the same place, at the same time of day, at specified periods to allow for realistic comparisons.
Any changes detected during water sampling might be the first indication that the water systems are out of microbial control and that maintenance issues are developing with your cooling tower. Those people in your organisation responsible for carrying out the water testing and record keeping should be in close contact with the water treatment contractor or in-house maintenance team so that they can quickly alert them to any problems so that remedial actions can be taken as soon as possible.
Minimising disruption caused by cooling tower maintenance
Some degree of disruption is inevitable when carrying out proactive maintenance or cooling tower repairs, but this scheduled disruption should be weighed against the inconvenience of having to shut down your facility because the towers have become contaminated with Legionella bacteria, they have developed a fault or even failed.
Many businesses choose to schedule their cooling tower maintenance for weekends, when they are not being used or at periods of the year when the factory shuts down to permit maintenance throughout the whole plant, not just on the cooling towers.
Spares and replacement parts
It also makes sense to keep a stock of the spare parts which are most commonly replaced during maintenance on site, or ask Water Treatment Services to stock them for you so they are available within hours when needed.
Despite what the original manufacturers of your cooling towers might tell you, it’s rarely necessary to buy original parts from the manufacturer as compatible parts will work just as well, as long as they are made to the same or better quality standards. Having a skilled in-house maintenance team, or using a specialist cooling tower contractor like Water Treatment Services to carry out the tower maintenance and servicing each time will also cut servicing time as technicians become familiar with the set-up of your cooling systems and its quirks.
Specialist water cooling tower maintenance and repair solutions
With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South East England and Wales), Leeds (North and North East) and Glasgow (Scotland), supported by regional teams of trained technicians, engineers and water treatment specialists, we can offer professional cooling tower maintenance, repair and servicing solutions to businesses throughout the UK and Ireland.
Contact us today for more information or for your FREE, no obligation quote.
