Tuesday, April 5, 2011
Saturday, March 5, 2011
Crossland Mechanical is a New York City based mechanical contractor providing HVAC, mechanical and maintenance services.
Sunday, February 7, 2010
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.
Mark Strahan is a 35 year veteran of the HVAC industry and is currently an account manager with Burt-Burnett, Inc., an HVAC mechanical service and EMS controls contractor. Mark can be reached with comments or questions at (480) 557-8593 or firstname.lastname@example.org
When you think of chiller and cooling tower maintenance the first thought is usually about how much of a hassle it is to perform this important but unpleasant task; power washers, cleaning solvents hoses, buckets and other cleaning accessories need to be assembled and moved from unit to unit, up and down off of rooftops, behind buildings and other out of the way locations; chillers and cooling towers need to be opened, housings need to be removed and internal components power washed (all the while getting the debris from the cleaning process all over you) then the equipment needs to be reassembled before moving to the next one - WOW, what a hassle!
As unpleasant this job is, ensuring that the cooling equipment which supports your production process stays clean and running efficiently is one of the most mission critical jobs there is because if your process cooling equipment fails due to system fouling, then production will fail - costing the business thousands of dollars in maintenance, repairs, downtime and lost productivity.
In most regions of North America, cottonwood seed is a major contributor of cooling equipment fouling. This naturally occurring airborne contaminant (generated by the Poplar Tree) usually effects operations from May thru early August, hence, companies that rely upon process cooling must clean their equipment frequently during this period or risk failure. Then comes the dog days of summer when insects, paper, construction debris, birds and just about everything that blows in the wind seems to find its way into your cooling equipment, then comes the final seasonal assault during the fall season when the trees drop their leaves, scattering them to the wind where they always seem to find their way to your condenser coils and cooling towers.
Keeping up with HVAC maintenance during the spring, summer and fall is nearly a full time job for most production operations and as the economic realities of business cause maintenance budgets and staffing to be reduced, it is increasingly important that companies find effective maintenance solutions that will streamline their day to day HVAC maintenance activities and enable them to more effectively handle work loads with fewer people and with fewer budget dollars.
Think about it, if you are in a lean maintenance staffing situation and you had five things to do on any given day and one of the tasks was cleaning condenser coils and cooling towers, how high on the "To Do List" would it rank? Given that it's time consuming and hard, dirty work, most people would rank it pretty low; Unfortunately, if the equipment is in need of cleaning and maintenance continues to be delayed, no reason for delaying it will change that fact and the equipment will continue to operate at an increasing level of inefficiency until the equipment can no longer support the cooling requirements.
Now consider the same list of five things to do except this time cleaning cooling towers and chiller coils only took a few minutes per unit using a broom, now where would this task would fall on the "To Do List"? Well, there's no real way of knowing, but the likelihood of it ranking high on the list is pretty good. Furthermore, if cleaning the equipment was as easy as using a broom or rinsing with a garden hose and it didn't require opening or disassembly of the equipment, then nearly anyone could perform the maintenance and that would change the dynamics of the HVAC / Cooling tower maintenance process.
How to Change the Dynamics of the Maintenance Process.
Air Intake Filtration specifically engineered for use on condenser coils, cooling towers and other HVAC equipment is one of the best ways to prevent fouling of your equipment. Unlike window screen, bug screen, shade screen and conventional filters including roll media, pleated filters and electrostatic filters which are largely designed for internal use on air handling units and forced air heating systems, Air intake filters are specifically designed to mount to the outside of the equipment where it stops airborne debris before it enters your system and where it can be easily seen and quickly removed using a broom, brush, shop vacuum or by simply rinsing with a garden hose - Even the rain has a cleansing effect on air intake filters and they never need to be removed for cleaning. Furthermore, because of the critical airflow requirements on cooling towers, and air cooled chillers, air intake filters are specifically engineered to be nearly invisible to the airflow on high volume / high velocity air flow systems (static pressure drop is less than 1/10" w.g. at 600 fpm air velocity).
So What's The Big Deal About Air Intake Filtration? Air Intake Filters help eliminate the "hassle factor" by dramatically reducing HVAC maintenance time and effort - but the benefits don't end there; here's what else they will do to save budget dollars and change the dynamics of your maintenance process:
Condenser Coil Filter Screens -Benefits
* Prevents debris from getting into coils.
* Reduces / eliminates annual pressure washing
* Reduces / eliminates need for cleaning chemicals
* Helps reduce energy cost because coils stay clean all season long.
* Dramatically reduces maintenance, repairs, downtime and lost productivity.
Cooling Tower Filter Screens - Benefits
* Reduces / eliminates sludge build-up in the basin by significantly reducing bio-loading.
* Prevents fouling of fill.
* Prevents plugging of strainers, blow-down valves and heat exchangers.
* Helps reduce algae growth by diffusing sunlight, which supports photosynthesis.
* Reduces water treatment chemical consumption due to reduced bio-loading.
* Dramatically reduces maintenance and repair cost, downtime and lost productivity.
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
The following video shows how cooling tower fill is being removed. This will provide you some idea if you have not done this before. This video is provided by 1500 series Cooling Tower. coolingtowerproducts.com Ph: 800-733-1584
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.
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.