GARY DICKER, DIRECTOR AT DHD COOLING, PRESENTS A CHECKLIST FOR ELIMINATING DANGEROUS DRIFT FROM COOLING TOWERS.
Drift from a cooling tower can be a huge problem. Drift is the aerosol emission of process water from a cooling tower. These emissions are capable of travelling upwards of 1km, with a properly treated system the level of bacteria must be controlled within safe parameters but even in these systems the water droplets could be carrying Legionella Bacteria, so the potential for an outbreak is increased, if more drift is created. This is why it is critically important that as a plant operator you can spot the signs of excessive drift, and do something about it before it becomes a problem.
Can you feel water droplets when you are near your cooling tower?
It is often the first sign that you have a potential problem. If you feel water droplets hitting you as you are in the vicinity of the cooling towers, then it is imperative that you do some further investigation.
Do you have the correct flow rate going over the tower?
If the flow rate is too far above the design then the fill pack or distribution system can become flooded which in turn can cause increased drift rates. If the flow rate is too far below the design flow of the tower, then in certain types of system this can lead to poor distribution and higher air velocities, which can lead to increased drift.
Is there staining on the drift eliminators?
A sure sign that there is excessive drift is if there is localised scale build or staining on the rear face of the drift eliminator. The cause of this is usually related to process water exiting the tower, and if there is water visible on the rear of the drift eliminators, then you have a problem which needs immediate attention.
Do you have the right fill pack correctly installed?
There are a number of types of fill packs available for cooling towers, as this is one of the main thermo-hydraulic features of your equipment, which is usually selected to meet your specific needs, and as such needs to be correctly selected for both performance and safety reasons. The wrong type, or incorrectly installed fill pack can lead to large amounts of water being entrained within the airstream, resulting in the drift eliminator being overloaded and water droplets being ejected from the Cooling Tower.
Are your drift eliminators damaged?
Drift Eliminators work by having an available surface for water droplets in the air stream to impact, and thereby be caught and prevented from exiting the Cooling Tower. If these surfaces are damaged or the panels are not tightly fitting then the water will be able to pass straight through.
What can you do?