Corrosion caused by the chemical reaction of salts and other chemicals on the steel in the tower. All who have lived up north in the winter, can remember the rusted out cars caused by salting the roads. This is one example of by the salts and other processes that are going on continually within the tower. The most common method of checking the rate of corrosion in a tower is by the use of coupons. Coupons are little metal tags of mild steel that are about the size of a dog tag and are held in the water stream of the tower and periodically removed to check the corrosion rate.
Current practice in Treating and Testing of Towers
There are many new technologies being used more and more frequently on cooling towers. In order to understand how these processes work, we must first understand a series of events taking place constantly within that tower. As water within the tower is cooled, it also evaporates a percentage of that water, usually about 1.8 gallons per ton per hour. This water leaves as pure water such as the water does from a tea kettle and just like your tea kettle, the minerals are left behind to from scale or scaling. If you look inside your tea kettle (after pouring out the water) you will find a white substance on the sides of the kettle. That is scale tan the same thing happens to a cooling tower. As this water evaporates, Make-Up Water is added to replace it. At the end of every day a condition arises which is called Blow Down, and is simply the practice of draining the tower and replacing its entire water supply. This includes all the chemicals currently being used, and the tower is then refilled and the process is started all over again.
Alternative treatments used instead of chemicals are as follows:
Copper silver ionization — This is a process using a sacrificial anode of copper and one of sliver, which when introduced into the water supply causes a reaction which kills algae. It is effective and does work, but has several drawbacks, one of which is a potential galvanic reaction.
Magnetics — This process works as follows:
- Molecules suspended in fluids tend to cluster
- A fluid traveling through a pipe or line carries these molecules and clusters.
- Larger clusters trap molecules.
- These larger clusters tend to slow in speed and gravitate toward the side of the pipe or line forming unwanted disposal of the fluid.
- Immediately, as the flow of the fluid brings clusters of molecules in contact with the powerful magnetic field circuitry, clusters are broken apart with a single, instantaneous jolt.
- Free of clusters of molecules, the fluid proceeds through the pipe or line with the chemical characteristics of the fluid intact.
- The impact of the magnetic field circuitry is retained or remembered by the suspended molecules, preventing additional clustering as well as scale from forming.
No System is Too Old
When preexisting scale with the corresponding correct magnetic property comes into contact with the flow of the treated fluid, it can become resuspended and gradually removed. However, precautions may be taken to determine the extent of scaling and corrosion in the system. In some cases replacement of an element may be the only solution.
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