Friday, 5 May 2017

Don't Clog up Your Cooling Tower System


Legionnaires’ disease is a potentially fatal pneumonia caused by legionella bacteria. It is the most serious form of a group of diseases known as legionellosis. Other similar (but usually less serious) conditions include Pontiac fever and Lochgoilhead fever.
Legionella bacteria are common in natural water courses such as rivers and ponds.
Since legionella are widespread in the environment, they may contaminate and grow in other water systems such as cooling towers and hot and cold water services.

They survive low temperatures and thrive at temperatures between 20-45°C if the conditions are right, e.g. if a supply of nutrients is present such as rust, sludge, scale, algae and other bacteria. They are killed by higher temperatures.

Cooling towers, evaporative condensers and hot and cold water systems have been associated with outbreaks.

Keeping the water in a cooling tower system clean will not only control legionella, but also lead to other advantages. By reducing scale and fouling, you are also ensuring that the cooling process is operating efficiently. Scaling reduces the effectiveness of biocide treatment and fouling can lead to loss of plant performance.

Benefits of Clean Water

  • Reduced energy consumption - as little as a 1mm layer of dirt, scale, or biological deposits on heat transfer surfaces results in a loss of cooling tower efficiency, increasing energy costs.
  • Improved chemical performance - dirty water requires more chemicals to treat than clean water because a build-up of solid contaminants provides a buffer that reduces the effects of treatment chemicals. Additional chemicals are then necessary.
  • Lower maintenance cost - frequently draining a tower and cleaning sediment increases labour requirements, and results in added costs to replace lost water in the system and provide additional chemicals.
  • Improved productivity and less downtime - fouling a cooling system slows production because machines cannot run efficiently. A fouled cooling tower could take a system down for an extended period of time until repairs are complete, resulting in less production per day and lost profits.
  • Control of biological growth - legionella, bacteria that thrives in improperly maintained cooling tower environments, is particularly important to control because it poses significant health risks.

A 200-ton cooling tower will draw in over 300kgs debris during a typical cooling season.

The tower basin or remote sump provides a perfect environment for unwanted matter to settle and accumulate whilst the wet and warm conditions of the basin or remote sump encourage bacteria growth.

Chemical water treatment does control the effects of these microbial organisms, but on its own does not serve to eliminate the habitat that promotes the proliferation of organisms.

Using a filter system does not replace chemical treatment but chemicals cannot reduce particle build-up. Insects, seed, dust and other airborne particulate will ultimately provide the nutrients for bacteriological growth.

The tower basin or remote sump provides a perfect environment for unwanted matter to settle and accumulate whilst the wet and warm conditions of the basin or remote sump encourage bacteria growth.

Solution - a RABScreen 

  • Reduce the build-up of contamination, the breeding grounds for microbial organisms, by fitting an air intake protection screen
  • The RABScreen air intake protection screen will protect the air inlets and remove a large percentage of airborne debris being drawn into the tower.
  • And when they are dirty simply wash, vacuum or brush clean. A truly cost effective solution.

Would you like to know more? Just use our contact form or call 0800 999 5750 to speak to one of our advisers.

Technical information provided by BAC. To see the full article please go to 

Wednesday, 19 April 2017


A large data centre’s coolers have just been given valuable protection from contamination through the fitment of RABScreen air intake screens. 
The Hibernia Atlantic data centre is located on a one acre site on the north west coast at Southport in Lancashire.  It’s a remote location surrounded by fields and the chiller cabinets would normally be subject to local airborne debris in the form of seed, pollen, leaves and insects.  However, this quickly changed when adjacent land was sold off for housebuilding development.  The two-year development project has massively increased the amount of airborne debris, not only from increased traffic but also the dust from construction.
Paul Hanstock Air Conditioning Ltd which installed the chiller cabinets and which provides quarterly servicing recognised the potential contamination problem and has specified RABScreen air intake screens as the solution to the problem.
RAB Specialist Engineers Ltd surveyed the RABScreen filter media up to 15ft in length to cover all sides of the three Daikin EWAQ520F-XL010 chiller cabinets.  The screens were made with 32mm borders and easily fitted onto the cabinets using stainless steel grommets.
site and subsequently supplied and fitted large
Paul Hanstock, Managing Director of the air conditioning company has been delighted with the installation, commenting, “We are really happy with the way the installation went and the RABScreens will certainly protect the coils and keep them contamination-free.  From this experience, we are very likely to use RABScreen on another site later in the year”. The RABScreens are likely to reduce the maintenance requirements by the air conditioning company every quarter and there should also be energy savings through the more efficient running of the air conditioning system.  Just 1mm of dirt can reduce efficiency by 21%.

Manufactured in the USA by Permatron, the RABScreen BHA air intake screen is a black engineered mesh, which is heavy duty and high abrasion resistant.  Incoming debris held in place on the mesh is easily removed by vacuum, brush or washing during regular maintenance.
Protecting the data centre’s equipment from incoming debris with RABScreen external screens saves money by extending the life of disposable filters and saves as much as 30% of input energy on chiller coils.  This together with labour saved by reducing cleaning and chemical use, means that return on investment can be less than six months. 
RABScreen air intake screens are ideal for air moving equipment fitted in industry, in food processing factories, hospitals, hotels and retail, and in schools, colleges and universities. 
The RABScreen air intake screens are made of a black high abrasion (BHA) specification comprising a single layer of 9 x 9, 1000 denier multi polymer coated polyester mesh.  Highly durable, rot and weather resistant, and UV protected, the air intake screens are UL classified for flammability and come with a ten-year UK warranty covering the media, grommets, final border and stitching.  The media has ripstop corners that will not tear. There are numerous fixing methods to suit different situations and these include fittings with studs, bolts, self-tapping screws, magnetic strip, drop tab fittings, or by using a wrap-around technique with Permatron bungee cords.

Further information on RABScreen air intake screens is available on 01635 248633 by emailing or by visiting the company’s website at

Friday, 31 March 2017

Supermarket Central Refrigeration

Retail food outlets in the UK are responsible for around 3% of total electrical energy consumption and 1% of total GHG emissions. They are characterised by their average sales area and are normally classified as:

  • Hypermarkets - 5000m2 to over 10,000m2 sales area
  • Superstores - 1400m2 to 5000 m2
  • Supermarkets (mid-range stores) - 280m2  - 1400 m2
  • Convenience stores including forecourts less than 280 m2
Source - Applied Thermal Engineering 31 (2011) 147 – 156

In this same article the author states that the average annual electrical consumption is 1480kWh per m2 with integral or display refrigeration adding a further 300kWh per m2 when compared with centrally located refrigeration plant.

"No food supermarket should ever be bigger than 45,000 square feet," says Bruno Monteyne, senior analyst of food retail at investment firm Bernstein.

This is about the half the size of a Premier League football pitch and if we use that as a benchmark, the average supermarket will spend £689,000 per year on energy, with 70% being spent on electricity.

Most this electricity, 52%, is spent on refrigeration with an additional 9% on HVAC services.
In our average supermarket, the refrigeration cost per annum will be £250,000 with an additional £43,000 on HVAC.

When energy efficiency of fin-tube coils is mentioned, engineers immediately think of heat transfer co-efficient, newer fin designs, smaller diameter tubes, non-circular tubes, thinner tubes and other factors for better heat transfer.

Reducing the coil face velocity and increasing the number of fins per cm will provide the additional heat transfer needed to reach the required design temperature. Airside pressure drop is less, but the lower face velocity alleviates concerns about moisture carryover. 

Unfortunately, a reduction in fin spacing increases the likelihood of coil clogging which adversely effects the heat transfer and increases the fan speed to maintain face velocity.

During a recent survey, the out of town location of a major supermarket was surrounded by fields, woodland and a water treatment plant. Depending upon the season this will give rise to high levels of pollen, insects and seeds which will be drawn into the gaps between the fins. This increases the resistance, pressure drop and electrical energy use.

Cooling coil dirt on unprotected chiller requiring air intake screenUnprotected chiller requiring air intake screen

The average temperature for this town is 14oC (58oF). For 7 months of the year the ambient air temperature exceeds 13oC (55oF) peaking at over 22oC (72oF) for 8 weeks. In the absence of sub-metering, we have calculated that the cooling plant, with its associated compressors, will cost the store £110,000 per annum to run + quarterly maintenance rising to monthly in peak debris months.

Upon consultation, manufacturers advised that the optimum efficiency of the fans would be compromised should the coil fins, which provide up to 70% of the cooling capacity, become clogged. They also warned against a screen being attached to the coil face. 

Our installation comprises a base screen at decking level, two side screens and two end screens to maximize airborne particulate capture.

This installation is part of a trial. 

Unit 1 will be fitted with the RABScreen air intake screens.
Unit 2 will be left unprotected. 

During this 6-month trial, various data readings will be taken to demonstrate why the RABScreen has a typical ROI of less than 6 months.

Easy to clean, easy to fit and long lasting, this supermarket will improve its operational efficiency and reduce the maintenance cost of the plant in what is a highly competitive market place. .

For further information or to talk to an adviser just call 0800 999 5750 or email

Monday, 27 March 2017

The cost of disposable filtration

It is a little-known fact that air handling plant contains not just one, but multiple layers of filtration each providing a cleansing effect to the “fresh air” drawn into the workplace.

In a typical air handling environment, the first line of defence will be a low grade, low efficiency media which is designed to capture the larger particulate.

Depending upon the demands of the environment additional filter layers of a finer grade will be installed. All need regular replacement.

Each filter requires manufacture, transport, storage, installation, removal, transport and disposal. The administrative cost alone is massive and the effect of so many boxes of air moving around the country is an environmental nightmare.

RABScreen air intake protection is a simple solution to prevent airborne debris contaminating HVAC equipment. A specification by one of the RABScreen specialists or distributors will consider the following:

Size and consistency of the airborne debris.
·         Dust type (cement, sand, soil, paper fines etc.)
·         Local flora and fauna (trees, grass, weeds, reeds etc.)
·         Other debris (feathers, recycling plant, plastic fines etc.)

Type and design of the equipment to be protected.
·         Chillers (“V” or “W” coil, horizontal, vertical etc.)
·         Air handling units (terminal, make up, packaged or rooftop)
·         Air intake louvres (weather, sand trap, adjustable, acoustic etc.)
·         Cooling towers (natural draught, induced, forced, fan assisted natural etc.)
·         AC condensers (split, packaged, central etc.)
·         Integral display refrigeration units
·         Compressors

Power consumption of the equipment to be protected.
·         The higher the power, the greater monetary value of the saving and a quicker return on investment as we improve efficiency by the reduction of clogging. 

RABScreen air intake protection is part of an “Equipment Protection System” and utilises many versatile fixing and manufacturing designs to produce made to order product for YOUR application.

From a large industrial process cooling tower to a single refrigeration display unit in your corner shop the RABScreen is the most competitive air intake protection system in the UK.

Every single air intake filter screen is manufactured by hand. The machine shop is full of skilled staff working with a great quality ethic and yet it is flexible enough to cope with orders for 1 or 10,000 with no increase in cost or time delay.

A competitive price linked to high quality and superb design make the RABScreen Air Intake Protection System the best offering to the UK external air filtration market.

And, because we protect your disposables, you can now afford to buy more efficient, higher quality filtration from your supplier. In fact, you can buy both products from one company using the RABScreen distributor network.