Moisture in oil: Risks, prevention and monitoring
Moisture in oil is the water vapor content present in lubricating fluids. When oil contains excessive moisture, it becomes corrosive and loses its ability to lubricate machinery properly. These factors lead to catastrophic equipment failure.
Oil moisture threatens productivity and equipment longevity in industrial facilities. It accelerates wear and tear on critical components like bearings, shafts, and hydraulic systems.
These issues often develop gradually, making them difficult to diagnose until significant damage has occurred. These conditions result in expensive repairs and unplanned downtime.
The essential steps toward protecting equipment and preventing costly breakdowns are:
- Understanding how moisture affects oil
- Knowing how to monitor it effectively
In this article, we'll outline the risks that excess moisture, or humidity, in oil can cause. Then, we'll explore how to monitor humidity levels and what to do if they get too high.
ifm’s expertise in oil monitoring comes from years of developing moisture-monitoring solutions for heavy-duty mobile equipment. We successfully adapted this technology for manufacturing applications.
Our real-time monitoring capabilities are especially critical in heat exchangers, hydraulic systems, or where oil degradation can occur exponentially.
Acceptable moisture amounts in oil
In absolute measurements, acceptable oil moisture content ranges from 50 to 3300 parts per million. However, measuring it using relative humidity can be more practical.
Acceptable oil moisture reaches a warning level at 40% relative humidity. The alarm level for oil moisture is 60% relative humidity. This level requires immediate action to prevent equipment damage.
While various oils have different thresholds, these percentages are generally universal.
Higher temperature decreases relative humidity in oil. Lower temperature increases relative humidity in oil.
Mechanical industrial machines typically operate between 160F to 190F. Therefore, temperature is not a major factor when measuring oil humidity during operation because it remains consistent.
Effects of moisture in oil
High moisture levels in oil increase friction between machine components, leading to excess wear on parts such as bearings, hydraulic systems, and gearboxes.
High moisture accelerates component degradation in applications where water can mix directly with lubricating oils.
Lubricating oil contains additives. Moisture in oil degrades their effectiveness. An example of an additive is a layer of zinc molecules. Zinc is a soft metal that acts as a protective cushion between two metal parts that impact each other.
Corrosion in oil systems
Moisture in oil creates ideal conditions for corrosion, which severely damages equipment and impacts safety. When water combines with oil, it creates an environment where metal surfaces oxidize and deteriorate.
Corrosion accelerates when the relative humidity in oil exceeds 60%. At this level, free water molecules separate from the oil and directly contact metal surfaces. The resulting chemical reactions can quickly compromise critical components like bearings, shafts, and hydraulic systems.
Studies estimate that corrosion costs industries approximately $276 billion annually in the United States alone.
Proper oil moisture monitoring helps prevent corrosion-related failures. Real-time sensors can detect moisture levels before they reach the critical point where corrosion begins, allowing maintenance teams to take corrective action before damage occurs.
Measuring moisture in oil
Interval-based testing is most common for measuing and monitoring the amount of moisture or particulates in oil. But, new real-time monitoring with sensors offers more benefits.
- Traditional laboratory testing: Sending periodic oil samples for analysis reveals both particle content and moisture content. This method provides detailed oil condition information.
However, there are gaps between sampling and delays between sending samples and getting results. Critical changes causing catastrophic failures can occur between those times.
- Real-time sensor monitoring: Real-time monitoring enables faster problem detection, especially for systems where water contamination can cause exponential degradation. A proactive approach helps prevent the many issues that can develop when moisture problems remain undetected.
How moisture enters an oil system
Moisture ingress occurs through multiple pathways. As such, different industries and
applications face varying risk levels. Three common causes in industrial settings are:
- Atmospheric breathing: Industrial machines heat up when operating and cool down when they stop.The resulting pressure changes create an effect almost like breathing: When the machine cools, the pressure draws in air, and with it moisture, from the atmosphere.
This type of moisture ingress is common with equipment that frequently stops and starts, machinery located outdoors, and equipment with atmospheric vents of oil fill ports.
- Direct water contact: Processes that require quenching for rapid cooling, employ water spraying for sanitation, or use water-based cooling systems increase the risk of water ingress. Machines with open lubrication systems are more at risk.
Quenching is standard in steel mills, and food and beverage plants employ water spraying for cleaning. While cars use an air-based cooling system to regulate engine temperature, industrial HVAC systems often use water cooling.
- Environmental exposure: Outdoor equipment is virtually always prone to water ingress in their oil systems. They’re exposed to daily condensation and regular precipitation. This applies largely to construction equipment, agricultural machinery, port equipment, and other outdoor industrial installations.
Real-time monitoring is vital here. Excess wear and tear on an outdoor component that connects to a larger, more expensive machine can damage the entire system.
Methods to remove moisture and particles from oil
There are several ways to reduce humidity in oil and remove moisture and particles from it:
- Oil filtration: Oil filtering removes particles, similar to how a car’s oil filter operates. It also provides basic moisture removal during operation. Since oil moisture cannot be visually detected, continuous filtration is a first line of defense against both particle and moisture buildup.
- Heat-based drying: Higher temperatures decrease the relative humidity in oil. Heating the oil to 212°F boils off the water while leaving the oil.
- Centrifugal force: A centrifuge separates water from oil by spinning the oil to create high G-forces. The denser water particles move outward from the center of rotation while the lighter oil remains closer to the center. This process works best on low specific gravity and low viscosity oils.
Moisture in oil monitoring tools from ifm
Real-time monitoring enables faster problem detection, especially for systems where water contamination can cause exponential degradation.
ifm offers two oil condition sensors: the LDH for monitoring oil moisture and the LDP for providing counts of particulates in oil.
The LDH moisture sensor:
- Measures relative humidity in oil continuously
- Provides early-warning at 40% relative humidity
- Triggers alerts at critical 60% relative humidity levels
- Accounts for different oil types and operating conditions
The LDP particulate counter:
- Tracks contamination in multiple size ranges (4, 8, 16 , and 21 microns)
- Monitors particulate buildup that could indicate wear
- Provides comprehensive oil condition assessment
Our technology’s dual-monitoring capability makes it particularly valuable for industrial applications where moisture and particulate contamination pose risks to equipment.
A proactive approach helps prevent the many issues that can develop when moisture problems remain undetected.