KNOW FOAM - PART 6
KNOW FOAM - PART 6
Testing the Bubble Machine
by Dom Ruggeri
Normally when I attend field trials it is with a product formulated by me. However, on rare occasions all of us are asked to baby-sit a product we did not formulate and know very little about. Back in the early nineties, while working for a major formulating house, I was called upon to supervise a field trial. By no means was this an unusual request however the product being tried was on I never worked with, hence I knew very little about its performance. Further, there was very little data available. Well I thought I have been here before, so I’ll survive. Then I was told I’d be working with a new salesman. Terrific. Bad enough I am working with a product I know very little about, now I am working with a person I do not even know; another variable.
We entered the plant at 11:00 PM on Sunday night. The system was charged and running well. I was optimistic. The new salesman seemed ok. We had been there for about an hour when I noticed a pipe positioned in the return flumes. The coolant was exiting the pipe into a narrow flume and splashing back on itself. This was not a real problem but there was the potential for foam. Also, I noticed that the foam created at this bottleneck was breaking down stream. How long that would last depended on how much entrained air was held in the fluid.
We decided to let this minor foam problem rest and check the fluid concentration. That way we could make any adjustments and still get a decent night’s sleep. Fortunately all was well with the coolant levels and the concentrations. The foam issue was a different story. The foam level had grown and was overflowing the return flume; to make matters worse the salesman did not order any antifoam. He did not think it was necessary. At this point, it was my opinion the antifoam was more important than the salesman.
I had to battle a foam problem without any antifoam. a neat trick. I gave the salesman a small stick and told him to pop as many bubbles as he could. This gave me time to study the system. I noticed that the foam was coming out of the pipe I described earlier. I decided to move the pipe, my reasoning was that if the coolant had more time before it hit the bottleneck, it may have enough time to release the entrained air. Was I wrong. As I removed the pipe I got one large snoot full of coolant. My glasses were blown from my face and I could not see, but my eyes were not stinging. The salesman quickly grabbed me and led me to the eyewash station. He thought the coolant was in my eyes. I was lucky it was not. I informed I could not see cause I did not have my glasses but I washed my eyes out just in case. We replaced the pipe. First thing the next morning ordered enough antifoam to solve the problem.
Well it seems my editor thought that the last article on foam was the last and, well, it wasn’t. Regardless of how much time we spend developing a product if we do not test it by simulating actual field conditions we do not have a clear picture of how that product will perform. This goes for antifoams as well; I remember many times saying "do you want the fluid to work or pass that test?" This holds true for antifoams as well.
Warring Blender Test:
For many years this test has been one of the ASTM Standards. Even today, many formulators and end users rely on this test. However, through out my career, many of my colleges questioned the validly of this test. Many believe the shear forces will break a Modified Silicone Polymer. Still others believe the forces subjected on the fluid are not representative of what the fluid sees in reality. My contention is that this is a static test. Once the foam is generated we are measuring break time. Although foam does break when the fluid is in use, the foam build causes the problem and must be prevented.
The Bottle Test:
Another ASTM standard, once again this is a static test. One shakes the bottle and measures the time for the foam to break. This test is not representative of the field. However, it can give you an indication if your formulation is balanced since a balanced formulation should not foam.
Although no recirculation test is perfect, this test will measure foam build and give the formulator a fair picture of how their fluid will perform in use. Further, if there are any emulsification issues, a recirculation test will show these. Certain emulsifier packages will destabilize when recirculated. This issue will not show up with a blender or the bottle test.
In conclusion, a recirculation test will yield a better picture of how your fluid will or will not foam in use. As always should you have any questions please feel free to e-mail me in care of the magazine. Till next month,