Sourcing and Troubleshooting Foaming Issues in Compressors
December 07, 2017
A Q&A with Dan Myrick, Summit's Chief Technology Officer
Transcribed from Tribology Talk Podcast: Foaming
What is foaming?
A surface phenomena where you have bubbles on top of the surface of the fluid. When you have bubbles in the body you rely on them to raise to the surface and you want them to break apart rather than build a foam when they reach the surface.
What effect does foaming have on your machine?
Foaming can have a lot of negative effects. It can promote oxidation of the oil. You can lose the lubrication ability of the oil as the bubbles break on the surface of the component you’re trying to lubricate. It can make it difficult to keep the oil in the machine. If the foam is bad enough, it can foam out of the breathers or out of the dipstick. Cavitation of the oil pump or even over heating as foam is a pretty good insulator.
How do you diagnose foaming?
It’s usually visually evident. There have been times that it foams bad enough that it comes out of the machine. Sometimes it can be misdiagnosed if there is pressure on an oil system and you take that pressure off too rapidly then the gas wants to escape the fluid and the bubbles can’t break fast enough so it foams up for a moment and then goes back down, similar to opening a can of soda. We don’t consider this foam, just if during the operation you can see it in the sight glass or there is evidence of foaming during the operation.
What is the cause of foaming?
On the tech service side, it’s very tricky to find out what the cause is. Typically it has to do with contaminants, such as water, solids or other chemicals or oils that are inadvertently mixed into the lubricating oil or machine causing an imbalance or some kind of change in surface tension. There can be mechanical issues that cause foam. If there’s some kind of air leak on an intake that actually draws so much air into the oil that it can get overloaded with air coming into the system and can’t break up the foam. If you overfill a piece of equipment, a splash lubricated type of equipment, then it can agitate the oil to where it’s producing so much foam that it can’t get rid of it quick enough.
What’s the first move when experiencing a foaming issue?
First thing we have to ask a customer to do when experiencing a foaming issue is to send us a sample of the oil. If they send us a sample, we can run ASM foaming testing in house. If we run the foam testing and reproduce the foam, then we know it’s not a mechanical issue, something has changed the surface tension of the lubrication itself. So we’ll begin looking for contaminants that weren’t in the initial product. If we run the foam testing and it doesn’t foam, then there is probably a mechanical issue.
If it is foaming here and it’s an issue with the oil, do you need to clean the machine with Varnasolv and all that to make sure the next oil you put in doesn’t have the same problem?
When we get it here and see that’s its foaming and then run analysis but can’t really determine there is a contaminant and the bulk of the fluid looks fine, then instead of requiring the customer to drain it, we can send them a cocktail or something to add to it. Some additional antifoam that can be treated on site and restore the antifoam properties to where it was when it left here and then maybe it goes away forever at that point. We look for ways that they don’t have to change the whole change of oil if there’s not a significant amount of contaminant.
Assuming someone sees foam, and it’s not the coke can effect it is time for action, right?
Typically it is time for action, it doesn’t just go away. Once you have a problem there it needs to be addressed. First thing you need to do is pull a sample and send it to the oil supplier to try and determine the cause. If it’s mechanical, you want to chase it down as quickly as possible. If it’s a chemistry issue, either the oil has to be changed or it’s a possibility to try and use some antifoam. You have to be very careful with antifoam too, it’s a low treat additive and it operates such as, if you over treat with antifoam it can cause air entrainment. When you get air bubbles in the body of the fluid and they don’t want to rise quick enough to get to the surface to break up as foam. So you have to be real careful with the antifoam additives that you don’t over treat.