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What Causes Oil Foaming: Definition, Solutions, & Causes
It may be challenging to think of oil as a substance that can foam, but even this viscous liquid can experience its fair share of air bubbles. However, oil foaming can lead to serious issues in key industrial systems.
The guide below examines the primary causes of oil foaming and offers guidance on how to address and prevent it from occurring again.
What Is Oil Foaming?
Oil foaming occurs when a significant amount of air bubbles gather on the oil’s surface and remain there.
While a small amount of foaming is normal in most industrial systems, and even in the motor oils used in high-performance automotive engines, excess oil foam typically indicates a significant internal issue. If not addressed promptly, the foam can also exacerbate problems that lead to equipment failure.
Air entering the oil in a particular machine (also known as oil aeration) comes in four different forms. In some cases, these types designate a progression of air entering the lubrication system, culminating in the form of oil foaming.
What Types of Oil Aeration Exist?
There are a few main types of oil aeration:
- Free air: Air becomes trapped in the system, forming air pockets. Since the air has not yet mixed with the oil, it can be removed through degassing to resolve any issues proactively.
- Dissolved air: If the air remains within the system long enough, it begins to integrate into the oil. As the oil’s temperature increases, the air forms small bubbles not visible to the naked eye.
- Entrained air: The air bubbles remain trapped within the oil, altering the chemical makeup as they gather.
- Foam: As the air bubbles become more closely packed, they rise to the oil’s surface and float upon it.
Oil aeration can wreak havoc on the system it’s meant to lubricate and protect. First and foremost, air entering the lubrication system can lead to oxidation, which alters the oil’s viscosity and can cause the formation of sludge, sediment, and varnish.
These contaminants can also clog filters and restrict oil flow, causing poor performance. When the lubricant fails to perform as expected, the potential for metal-to-metal contact increases.
What Other Symptoms Are Associated With Oil Foaming?
Heavy-duty equipment often experiences performance issues and decreased efficiency in conjunction with oil foaming, which is itself a symptom of a larger concern. What’s worse, oil foaming can make oil levels appear higher than they really are by clinging to the dipstick during readings.
Here are some other common symptoms associated with oil foaming:
- Decreased efficiency and performance
- Reduced lubricity
- Weak oil pressure
- Increased component wear
- Oil oxidation
- Overheating
As the oil pump circulates lubricant, any trapped air bubbles burst inside the pump, damaging the internals and causing cavitation. This phenomenon also increases heat and turbulence inside the pump, further perpetuating any existing foam.
While the oil pump may exhibit signs of cavitation, it’s essential to identify the exact source and resolve the issue to prevent the need for repeated oil pump replacements.
What Causes Oil Foaming?
Oil foaming can be caused by one or more mechanical or chemical factors. Mechanical causes stem from the interaction between physical components, while chemical alterations affect the lubricant’s composition, reducing its ability to perform as expected.
Below are common mechanical causes that can lead to oil foaming:
- Rapid flow rates
- Faulty pump operation
- Gear mesh interactions
- Vacuum leaks
- Airline placement
- Bearings agitation
- Poor oil reservoir design
Even if no mechanical cause is present, oil foaming can still occur if the lubricant experiences chemical changes. Catalysts responsible for these changes include the following:
- Moisture, sludge, grease, and other contaminants
- Poor oil quality
- Oil cross-contamination
- Oxidation byproducts
- Improper fill levels
- Incompatible or depleted defoamer
Understanding the causes of oil foaming and pairing that knowledge with the exact symptoms present in your equipment can help you track down the source and resolve the issue.
How To Solve Oil Foaming
While your first thought might be to simply change the machine’s oil and chalk up the oil foaming to a bad formula, chances are you’re missing the bigger picture.
Yes, you will need to put new lubricant in your equipment, but it’s best to diagnose the issue before getting your hands dirty. Evaluate your equipment’s functionality by checking for clogged filters, vacuum leaks, loose fittings, and any other conditions that may lead to oil foaming.
Once you’ve documented and addressed these potential causes, put new oil in the system and monitor its performance to determine if the underlying issue(s) have, in fact, been resolved.
If you don’t feel comfortable moving forward with new oil just yet, you can always order an oil analysis to determine the condition of your current oil. This step can also be critical if you plan on introducing an antifoam additive.
Depending on their formulation, silicone-based and polyacrylate additives can act as both anti-foaming agents and defoamers. The distinction between the two derives from when they’re most effective: as a preventative or reactive method of reducing oil foaming.
Anti-foam agents prevent foaming by destabilizing the air bubbles, while defoamers work quickly to reduce surface tension.
How To Prevent Oil Foaming
Proper care and maintenance can help prevent oil foaming, especially by following the manufacturer’s recommended service intervals and replacing worn or failed components.
Operators should make sure they’re using the correct oil for the machine’s specifications and maintaining adequate oil levels to keep the equipment lubricated. Installing an oil-air separator can also help remove air from the system.
Trust Cadence for Industry Expertise and Insight
If you suspect your equipment has a problem with oil foaming or have confirmed its presence after reading this article and need help finding the appropriate solution, call us at 336-629-2061 to speak with a friendly and knowledgeable representative.
Our oil analysis services can help you diagnose the root cause of oil foaming and provide the insight you need to address the issue and keep your operations running smoothly. For above-and-beyond service, trust the experts at Cadence to deliver value at every turn.
Sources:
Cavitation Flows | University of Minnesota Fluid Mechanics Lab
Air Entrainment - an overview | ScienceDirect Topics