KNOW FOAM - PART 4
KNOW FOAM - PART 4
Switching Off the Bubble Machine
by Dom Ruggeri
Back in early nineties, I was working on a project for a large aircraft manufacturing company. The system was charged with a high tech coolant. Like most high tech coolants, this one required a good maintenance program. This coolant was running well, however as is the case in many companies, coolant maintenance is an afterthought. Often they will use a program developed for a soluble oil they used about twenty years ago.
About a month after the charge-up, we got a call that there was foam all over the place. As always we caught the next flight out and they were right, there was foam coming out of the return flumes, spilling on the floor and making one giant mess, and one heck of a safety hazard. My first priority was to get those systems under control. We began by adding a particle defoamer to bring the system into control. We followed this with a modified-silicone antifoam to keep this system under control.
This particular modified-silicone antifoam was designed to keep a central system under control for at least eight hours. This time it was only lasting two hours then we had to dose it again. Although a system survey was done prior to the charge-up, I decided another one would not hurt. We needed insight into the inner workings of this unruly system. As I suspected, we found nothing amiss. So why did this system need a dose of antifoam every two hours?
I don’t mind saying I was a bit confused. We decided to check the concentration of the coolant. The emulsion refractive index showed a concentration of two percent. Concentration by total alkalinity showed a concentration seven percent. The acid split would be the determining test; it showed a concentration of one and a half percent. Further, the third shift superintendent said they were having tool life problems. Well at one and a half percent, I can imagine they were.
We investigated this problem and found that as the coolant was circulating in the system the emulsion was becoming unstable hence more drag out. The antifoam was being removed with the cream layer leaving the water-soluble moieties to create massive amounts of foam. We traced the problem down to the circulating pumps, for some reason these types of pumps sheared the emulsion so badly that the emulsion destabilized. We were able to control the foam until product modification could be formulated, tested, and approved.
Last month, I talked about how to battle a system that was foaming out of control. Like anything else, it is one thing to kill and maintain foam control. It is quite another to find the root cause of a foaming problem. We have all heard this one: a central system serves 50 machines and one is foaming so the customer has a foam problem. What about the other 49? If there were a foam problem with the coolant, all 50 machines would be foaming out of control. This is a machine problem and it should be addressed as such. However, what if there is a foam problem?
First and foremost, bring the system back into control using the steps I outlined last month. Next, check the coolant for contamination (someone could be dumping floor cleaner into the system inadvertently). The concentration is the first indicator that something is wrong with your product. I would run these three tests:
1. Concentration by Refractometer:
This is not the most reliable test and many things like tramp oil will interfere with it. Nevertheless, it is an indicator that something is wrong with the coolant.
2. Concentration by Alkalinity:
This test will tell you if there is contamination of either an acidic nature or alkaline nature, like floor cleaner. If this test is way off in either direction, you have a contamination problem.
3. 3. Concentration by Acid Split:
This test measures the lubricant package in the coolant system. If this test is way off to the low side, you may have an emulsion instability problem. Should it be off to the high end, you have a tramp oil problem. Yes, the additives in tramp oil can cause foam.
There are many other tests one can run but many of these require a laboratory and your lab may be quite far away. However, the above tests will give you an understanding of what is going on in the system, and yield a direction toward the root cause. Once you know what the root cause of the foam problem you can either solve it if possible or make recommendations to your customer on how to control the problem. Either way you get a satisfied customer.
As always, should you have any questions please feel free to e-mail me in care of the magazine. Till next month,