Filtration Systems Can Reduce Maintenance and Downtime.

To strike an interesting analogy, your cooling tower and heat exchanger is what the lungs and heart are to the human body; when either aren’t working properly, it effects other parts of the body and your health suffers. Similarly, when your cooling tower and heat exchanger isn’t clean, the heat exchange process doesn’t work efficiently and the health of your production and process cooling system suffers.

Process cooling systems that rely on cooling towers to dissipate heat from process cooling water accomplish this by drawing massive volumes of air into the cooling tower as the water travels through the fill material on its way back to the basin. Through the natural evaporative process, heat is dissipated from the water before it reaches the water basin from which it is re-circulated through the chiller then through the heat exchanger and back again (kind of like when you sweat while working and letting the air evaporate the perspiration to cool you down). It is important to realize that cooling towers are gigantic air scrubbers that capture all airborne debris that happen to be floating nearby, and if your system doesn’t have effective filtration, the debris can clog the fill and get circulated and trapped in the heat exchanger where it can build-up, restrict water flow and cause your process equipment to malfunction due to overheating.

An example of this is illustrated by a major automotive assembly facility that had faced periodic downtime due to their robotic welding systems not holding tolerances and causing quality problems. After the robotic technicians spent several days trying to initially solve the problem, one of the maintenance workers opened the heat exchanger and discovered that it was impacted with cottonwood seed, insects and other debris – flow had been reduced and the robotic equipment was running hot. Now you might be asking yourself, whey didn’t they have some sort of filtration equipment? The answer is simple; at the time the facility was built, the ambient conditions in that area didn’t require a filtration system. However, as the years went by and the area became more developed and cottonwood tree populations grew, the need eventually surfaced.

The interesting thing to note about this situation is that even though cleaning the heat exchanger got the robotic welding system back on-line and running at peak performance, it didn’t solve the problem. In fact, cleaning heat exchangers is like taking a cold capsule to relieve the symptoms of a cold. Unless you treat the root cause of the problem, the cooling system will suffer time and again. The root cause in this case and in most heat exchanger fouling situations is the cooling tower – stop the debris from getting into the cooling tower and it will protect the entire process cooling system including fill, cooling water, chiller and heat exchanger. With the proper filtration technology, your process cooling system will stay clean and running efficiently all season long.

Selecting The Right Filtration System

It is important to realize that optimizing the ecology and operational efficiency of your evaporative cooling system is best accomplished by combining a chemical treatment regimen with some type of filtration. The reason is that chemical treatment specifically targets suspended solids and particulates of 40 microns and below, while filtration systems are designed to stop larger debris, especially the kind that causes system clogging and fouling.

For cooling tower filtration, there are two general technologies: Water Based Systems for which there are a few different variations and Air Intake Filtration Systems. With water-based systems, the choices include basic water strainers that remove debris by simply passing water through a mesh strainer; sand filtration systems that remove debris by passing the water through sand and centrifugal separators that spin the water and remove the debris through centrifugal action. In contrast, Air Intake Filter Systems remove the debris by filtering the air as it is being drawn into the cooling tower, keeping the debris out of the system in the first place. When considering your filtration options, the following questions should be asked.

• What is the cost associated with downtime due to heat exchanger or cooling tower fouling or clogging? (Knowing this will help you justify your filtration system cost)
• What type of debris is most problematic (can you see it or is it microscopic)?
• Specifically what part of the system does the filter protect?
• Which system provides the greatest filtration surface area (this can directly impact frequency of cleaning – the smaller the filter the more frequently it needs cleaning)
• Can the system be installed without shutting down the cooling tower? (If the cooling tower must be shut down for installation, you need to factor lost productivity into the cost of your filtration system if it’s not being installed during shutdown periods.)
• What is the cost associated with both the filter and installation?
• How easy is the system to install and maintain?

Answering the above questions will help you to fully understand your options and to make the best choice for your operation.In the case of the automotive manufacturer, the solution they selected was the Air Intake Filter system. The reason was that they needed a system that would protect their entire process cooling system including fill material, cooling water, chiller and heat exchanger. When they evaluated water-based systems, they discovered that the options provided varying degrees of protection for the chiller and heat exchanger but didn’t protect the cooling tower where the root of their problem was. If they had selected a water-based system, their cooling tower would have still drawn airborne debris into both the fill and water where the water filter would have captured the debris before it circulated throughout the system. From a maintenance standpoint, that would have solved the heat exchanger problem but it would have done little to reduce maintenance on the cooling tower. Further, when they compared the cost of water based filtration versus air intake filtration technologies, Air Intake Filtration was found to be the more cost effective approach for their operation.

If you are not currently using a filtration system as part of your process cooling system, then any filtration technology will give you more protection than you have now, however, selecting a solution best suited to your operation requires that you know what kind of debris is the problem and where it is getting into the system. As a rule of thumb, ” don’t select a small debris solution to solve a large debris problem”. Conversely, “don’t select a large debris solution to solve a small debris problem”. There is clearly a place for both water based filtration and air intake filtration – be sure you’re selecting the right filtration for your specific need.

If you are looking to protect only your chiller and heat exchanger from airborne debris, then one of the water-based filtration technologies in combination with a good water treatment program can help you manage the debris that gets into the cooling water. If on the other hand, you’re looking for full process cooling system protection, then you should look at Air Intake Filtration – It will stop the debris from getting into your system in the first place.

When you have chosen to use the cooling tower water treatment system, it is most important to remember to not ignore the maintenance required. The water carries bacterial growth in it whether it flows through the faucet or if it is flowing through a cooling tower. If this water is not treated as soon as possible, it can rust and corrode and deposits will form inside the water treatment equipment. This reason makes the cooling tower water treatment system so very important.

Problems From Not Maintaining The Cool Tower

When you do not keep up the proper maintenance on you cooling tower water system, you will find that many different problems will come up. These problems can include scale formation, corrosion, and biological fouling.

Problems With Scale Formation

Scale is what is formed when wet solids get clogged in the pipes. This scale is made from heat and cold water that contains a very high mineral content. These deposits will continue to build up over time. If these scale deposits start to form on a heat exchange surface, they will eventually clog the passages and slow the system down. The cooling tower can also be affected by the scale deposits. If the deposits block the flow of the basin or fill in the cooling tower, problems arise.

Choosing to use a cooling tower water treatment system will help to stop the problems of scale deposits. It is a very budget friendly way for you to treat the problems you are having but also to lower the maintenance and the cost of maintenance on the cooling tower system itself. The majority of money that is spent each year is on the removal of the scale deposits from the inside.

Inside Corrosion

When metal starts to dissolve, you have what is known as corrosion. Oxidation effects break the metal down significantly. The breakdown will cause the system to degrade at a faster rate than normal. The major point being that when the metal starts to break down, the strength of the metal and the thickness off the metal are reduced. The structure of the metal can no longer stand up to the pressure that it was designed for and pits and craters can form in the metal.

A cooling tower system will help to stop the corrosion from happening. The better of the treatments for corrosion is the ozone treatment. There are also other methods that work just as good.

Problems With Biological Fouling

Problems with biological fouling occur when the water has not been used and left for long periods of time. When the water is left unattended, it has the potential to form bacteria, fungus, algae, and protozoa. The microorganisms will eventually get to large proportions in the water and will cause a biological film to form on the surface of the water. This film is very hard to get rid of. This is what is known as biological fouling.

The biological fouling problems are commonly known to be the worst problem that you can encounter with the cooling tower system. The problems that can occur with biological fouling are low heat transfer, the fill can stop working properly, the water flow can be restricted or blocked, or corrosion can occur from the microorganisms present. It can also result in health problems for the humans that are using it.

The use of a cooling tower water system helps to get rid of this particular problem. When you purchase a good system, it will remove the bacteria, viruses, fungus, and any other organisms that should not be in the water. The cooling system will help the fouling that is a problem with the biological affects in the water to not occur. When these nasty things are removed from the water, it will definitely improve the quality of the water and also the flow of the water through the tower.

What is Legionnaire’s Disease

It is a bacterial infection that is characterized by pneumonia. According to the Center for Disease Control (CDC), legionnaire’s disease is caused by bacteria known as Legionella pneumophila. There are at least 43 species of legionella however, it is the Legionella pneumophila strain that causes over 90% of legionnaire disease deaths.

In the United States, it is estimated that as many as 18,000 cases occur each year. Death results in 5 – 15% of the cases.

Legionella are commonly found in low concentrations in both natural and unnatural (man-made) aquatic environments. Within unnatural environments, where water is used in an evaporative heat exchange process, warm temperatures combined with poorly treated cooling water can create an environment ideal for proliferation of this deadly bacteria.

Because cooling towers, evaporative condensers and chillers are highly efficient at drawing large volumes of air to support the evaporative cooling process, airborne organic material such as leaves, insects, pollen, birds, cotton wood and other debris is usually drawn into the water system and if not maintained can accumulate, decompose and contribute to system fouling and microbial growth including legionella pneumophila.

Ideal conditions for legionella proliferation include water temperatures between 77 – 108 degrees Fahrenheit (25 – 42 degrees Centigrade), presence of organic debris, sediment, scale, stagnant conditions and presence of amoebae. Legionella naturally preys on amoebae and incidentally prey on phagocytic cells (part of human immune system) when inhaled thus leading to Legionnaire’s Disease. The legionella bacteria is transmitted by aerosol (mist) from devices such as cooling towers showers and faucets and aspiration of contaminated water. Person-to-Person transmission does not occur.

Controlling Legionella in Cooling Towers & Evaporative Cooling Systems.

Based upon a six-year committee effort, ASHRAE board of directors approved guidelines (known as guideline 12) that provides environmental and operational guidelines for maintaining safe evaporative water cooling systems. The guidelines are intended for use by: commercial cooling system designers, maintenance engineers, equipment manufactures, owners, operators and users.

Key Maintenance Recommendations (Guideline 12)

* Keep system clean using a microbial treatment program.
* Use a qualified water treatment consultant to establish and oversee a water treatment program.
* Keep system free of debris that can contribute to the food source for legionella. (Air Intake Filters can help to control debris and organic material build-up).
* Inspect and clean cooling equipment if it is found to have a build-up of dirt, organic matter or other debris.
* Inspect drift eliminators and clean or replace as needed.
* Keep maintenance and operational records that include equipment manufacturers maintenance manuals, description and dates of the water treatment program, inspection dates, MSDS documentation on all treatment chemicals, equipment repair records including dates, system water volume records, and the names and phone numbers of individuals responsible for system start-up, maintenance and shut-down.

Cooling Tower Locations Recommendations (Guideline 12)

* Locate cooling towers far from fresh air intakes and windows that can be opened.
* Consider prevailing wind direction and don’t locate upwind or upstream of outdoor public areas.
* Don’t locate in areas that can contribute debris and organic material.
* Consider the direction of prevailing winds and don’t locate upstreamof any outdoor public areas.
* Consider future construction, including that on nearby sites.

References: Center for Disease Control – December, 2000 Article, MMWR – July 1994, National Institute of Environmental Health, American Society of Heating, Refrigerating and Air Conditioning (ASHRAE)

Air Solution Company developed and patented the first Air Intake Filter specifically engineered to mount to the outside of cooling towers and other HVAC equipment for purposes of stopping the debris before it entered into the system. Since that time, Air Solution Company has been manufacturing and has introduced a variety of other innovative filter systems including its new Fine Mesh Filter which is engineered for use on small and medium size refrigeration coils and machine fan intake housing units. Air Solution Company Randy Simmons is with Air Solution Company, author of articles can be reached at http://www.airsolutioncompany.com

Here in the Phoenix metropolitan area, adverse water conditions require intelligent water treatment strategies to adequately maintain water cooled equipment. Proper management of the characteristics of the cooling tower sump water along with maintaining good tower hygiene in general accomplishes at least four positive things.

1) It avoids wasting excess water.

2) It inhibits scale formation.

3) It controls biological growth.

4) It reduces the corrosion rate of metal parts in the tower.

Let’s discuss how a cooling tower operates to understand why proper water treatment is important.

Most residents in the valley are familiar with an evaporative cooler. Water from the evaporative cooler sump is circulated by a pump over pads in the evaporative cooler and outside air is drawn through the pads. As the air is drawn through the wet pads some of the water evaporates and cools the air. The cooler air is then circulated into the space where cooling is desired. In the process of cooling the air, the water being recirculated across the pads is also cooled.

That is exactly the same principle being employed in the cooling tower, but on a much grander scale. Rejecting large quantities of heat from a building’s mechanical system requires a lot of water to be evaporated. For example, a one hundred ton water cooled chiller operating at full capacity for 24 hours would require the evaporation of more than four thousand gallons of water. That brings us to the subject of the characteristics of the make up water. Make up water is the water supply that replaces the water being evaporated in the cooling tower.

Here in the metro area, water conditions vary widely because our water comes from several different wells as well as surface sources. The water quality may change rapidly over a short period of time because different sources are utilized for the water supply. Each well has different water characteristics and they often vary widely from one side of town to the other. Water that comes from surface sources, like the Central Arizona Project will usually have significantly different characteristics than well water. Surface water quality may also be influenced by weather conditions such as drought or increased runoff.

As water evaporates in the cooling tower all of the non-volatile components stay behind in the sump of the cooling tower. There is actually a lot more in water than what we would call hardness (carbonates). There are also chlorides, suspended dust particles and biological microorganisms. As more and more water is added to replenish the water that is being evaporated, these dissolved and suspended components in the sump water continue to accumulate. If no measures are taken to control the concentration of these components in the water, the solution eventually increases in concentration to a point where “stuff” starts coming out of solution. This “stuff” ends up getting deposited on the surfaces that the water comes in contact with.

Have you ever seen an evaporative cooler where the pads haven’t been changed for a long while? I’ve seen them so encrusted with mineral deposits that the blower could no longer pull air through them. I’ve also seen them produce a bounty of biological growth in the sump water. That is exactly what will happen in a cooling tower without adequate attention to hygiene and an appropriate water treatment strategy.

When solids that are dissolved in water come out of solution they are deposited first on heat exchange surfaces and surfaces where the water is being evaporated. Heat exchangers, water cooled condensers, drift eliminators, the tube bundle in closed circuit cooling towers and the fill in open cooling towers are a few examples of surfaces where this occurs.

Deposition of mineral scale, dirt and biological fouling on any heat exchange surfaces can result in reduced heat transfer, reduced tower efficiency and increased energy costs. While reducing deposition of these is important with regard to the cooling tower, it is absolutely critical to avoid scaling or fouling in the water cooled condenser. Scaling and fouling in the condenser significantly reduces heat transfer capability and will seriously impact energy costs, performance and reliability.

A two part strategy is usually employed to manage the mineral content of the sump water. Part one is to maintain the sump water pH within allowable limits and to feed the correct type and amount of chemicals to help the water keep more of the dissolved solids in solution. Part two is intentionally sending some of the sump water down the drain (blow down). Blow down reduces the highly concentrated mineral content of the sump water by diluting it with the fresh make up water being added to replace the intentionally wasted water.

Biological growth can also become a significant health risk depending on the particular organism involved. Allowing mud and biological growth to accumulate in the sump of a cooling tower can accelerate corrosion of the sump and shorten the life cycle of the cooling tower. It can also provide a haven for microbes to escape the effects of a biocide.

Proper water treatment strategy and good cooling tower hygiene is not a one size fits all solution. The quality of the make up water will require an adjustment of the type of the chemicals and biocide utilized. It may also require changing feed and blow down rates for proper control. In addition, these requirements may be altered by the characteristics of each individual cooling tower installation.

According to Alan Bateman of DB Water Technologies, there are several things a good cooling tower water treatment program should address in order to be effective. They are total dissolved solids (TDS), hardness, pH, chlorides, suspended solids, an appropriate method for biological control and a proper blow down strategy. Each cooling tower manufacturer publishes recommendations for maintaining proper water conditions of the sump water. The advice of a qualified water treatment professional is advised to ensure that each item above is included in your overall strategy for cooling tower water treatment.

No water is ever pure. It is a little bit of a fairy tale when you think that water can be. Water is a universal solvent. When water is given to the environment, it becomes immediately contaminated with many different organic and inorganic substances.

Not every one of the contaminants is bad for you. Some of them can be toxic for humans to consume. The water treatment systems are designed and necessary for removing these substances from your water and giving you clean and safe water to drink.

There are many different water treatment systems to choose from. It will depend on the water that you are trying to get treated. One of the water treatment methods that you may want to try is known as the ozone water treatment method.

What is meant by ozone?

Ozone or O3 is a gas that has no color or smell to it. The ozone gas will have a reaction with anything that it comes in contact with. Because of this reaction, the ozone is used largely for cleaning and disinfecting things. The ozone gas is so highly reactive that it will cause corrosion on the things that it meets. Ozone is a great way to disinfect and clean but, for living tissue contact, it can be damaging in great ways.

Why Use Ozone Gas To Treat Water?

It is a very easy answer; ozone is the greatest biocide that is available. It reacts in a big way with the water and this makes it a great thing for water treatment. Ozone gas will kill viruses, bacteria, microorganisms, and fungus in the water. It can also stop scale deposits from forming and causing hard water to occur.

In certain research studies, legionella has also been destroyed by ozone gas. Legionella is a bacterium that is found to thrive in cooling towers. Every test that has been done shows that by sending ozone gas into the cooling tower will lower the bacteria counts and will provide standards for drinking water that is of a better quality. Ozone gas has also been shown to impact corrosion in the heat surfaces in a positive way.

Good Things For Ozone Water Treatment Use

The main good quality of using an ozone water treatment system is that it is able to get rid of the microorganisms that are found in water. Biological films ore one of the worst problems facing today’s supply of fresh water. By getting the biological agents under some sort of control, the ozone water treatment system can make sure that the water is free form viruses, bacteria, and other substances.

The ozone water treatment system will also help to eliminate the problem of scale deposits in the pipes. Because it inhibits the gathering of scale deposits, it will help to improve the work quality of the heat transfer surfaces. This ozone gas will make the system very good for industrial use and especially good for those systems that use water to heat or cool.