One of the most common problems that we see in water treatment when we survey a new customer’s facility is improper chemical feed location. Our water treatment professionals evaluate dozens of chemical feed stations in many different types of facilities every month, and we are always concerned when we see the same type of problem over and over again. Water treatment chemicals being fed in the incorrect location is one of those problems. This issue is even more peculiar because many times we will find that the actual water treatment chemical program and methodology is very appropriate for the system being treated, however, because of how that program is being fed into the system, the results are less than desirable.
One great example of where we normally witness this type of mistake is in applications where a dual biocide water treatment program is being fed into a large open condenser cooling system. Check out this video:
A typical dual biocide program usually consists of a corrosion inhibitor, an oxidizing biocide and a non-oxidizing biocide. Most of the time we will find that all that the chemicals being pumped into the open condenser system are correct, and in many cases, even ideal, to properly treat it. Based on the data that we collect, we also find that dosage amounts are within optimal ranges. However, when we look at the cooling tower it is obvious that there is a problem, and if you have any water treatment experience, you know this simple fact: if you are seeing problems in the tower, you are also going to have problems in the chillers.
Upon further investigation, we usually discover that there is some kind of mechanical issue that is causing insufficient chemical treatment, which leads to problems in the cooling tower and throughout the system. Incorrect chemical feed location is, by far, the mechanical issue that we encounter the most. The video in this post is shows a great example of where NOT to feed your cooling water chemicals. In the video you will see three different chemicals being used to properly treat the open condenser system, however, all three chemical metering pumps are pumping their chemicals into one common ¾” PVC pipe, which then carries the chemicals up to the common header. Very often we will find that this small feed pipe is either clogged or is not getting enough flow to begin with. Also, we often discover that the chemicals are being fed too closely together and that the counteraction between them is destroying the chemicals' efficacy.
In a perfect world, the chemical metering pumps should have their individual feed tubs directly injected through chemical stingers into the common header. The location of the stingers on the header should be at some point after the chillers and before entering the cooling tower. This ensures proper and full chemical dispersal into the entire cooling system and guarantees that all system components will be sufficiently protected.