Detailed Conversation About Water in Turbine Oil

Below is a recent conversation I had with a great qualified Turbomachinery engineer in my region.

Question:

When lab test results of Karl Fischer for Turbine oil come 200 ppm, I always calculate how much water is actually in that oil, like can you help me with 20000 liter oil tank, how much water is inside?

My Answer:

To calculate how much water is in a 20,000-liter oil tank with a Karl Fischer result of 200 ppm:

1. Understand ppm: 200 ppm (parts per million) means there are 200 parts of water per 1,000,000 parts of oil. This is equivalent to 200 milligrams (mg) of water per kilogram (kg) of oil.
2. Density of oil: Assume the turbine oil density is approximately 0.85 kg/L (common for turbine oils).
3. Mass of oil: The total mass of oil in the tank is: 20,000 liters × 0.85 kg/L = 17,000 kg.
4. Water content in the tank: Using the ppm value: Water content (kg) = (ppm value / 1,000,000) × total oil mass (kg). Substituting the values: Water content (kg) = (200 / 1,000,000) × 17,000 = 3.4 kg.
5. Convert to liters: The density of water is 1 kg/L, so: 3.4 kg × 1 L/kg = 3.4 liters.

Final Answer: There are approximately 3.4 liters of water in the 20,000-liter oil tank when the Karl Fischer result is 200 ppm.

Question:

As water is changing form from soluble, emulsified and free water, how this 3.4 liter of water is kept inside the oil ? The Karl Fischer test is showing the water in which form ?

My Answer:

The 3.4 liters of water detected in the 20,000 liters of turbine oil includes all the forms of water that are present in the oil (soluble, emulsified, and potentially free water), depending on the oil's condition and saturation limit. Here's how water is kept in the oil and how Karl Fischer testing relates to the different forms:

Forms of Water in Oil

1. Soluble Water:
2. Emulsified Water:
3. Free Water:

What Karl Fischer Measures

• Karl Fischer (KF) Titration: KF measures the total water content in the oil sample.
• This includes soluble water and emulsified water. Free water might not be accurately represented if it is not uniformly mixed into the sample or if it separates before testing.

How 3.4 Liters of Water Is Kept in the Oil

• In your case, the 3.4 liters of water is spread across: Soluble Water: Dissolved water up to the oil's saturation limit (e.g., 200-300 ppm for turbine oil). Emulsified Water: Additional water dispersed as tiny droplets if the saturation limit is exceeded.
• If there is free water, it likely settled to the bottom of the tank and may not have been captured in the sample analyzed by Karl Fischer.

Practical Implications

• If the Karl Fischer result is 200 ppm, it likely reflects the soluble and emulsified water in the oil sample.
• Free water may be underestimated if the sample wasn't agitated to homogenize the mixture before testing.
• To manage this: Conduct a visual inspection for free water (e.g., water layer or haze in oil). Use centrifuge testing or gravimetric methods to confirm free water content, if present.

In summary, the Karl Fischer test measures the total dissolved and emulsified water, but accurate detection of free water requires additional testing or careful sampling techniques. The 3.4 liters could be a mix of soluble and emulsified water, and potentially more if free water wasn't sampled properly.

Question:

Can the cold oil have free water formed even with 200 ppm test result ?

My Answer:

es, cold oil can have free water present even if the Karl Fischer test result is only 200 ppm. Here's why:

Temperature and Solubility Relationship

• The solubility of water in oil decreases significantly as the temperature drops.
• At higher temperatures, turbine oil can hold more dissolved water without exceeding its saturation limit. For example:
• At 40°C, turbine oil may dissolve up to 300 ppm of water.
• At 20°C, the saturation limit might drop to around 100 ppm (depending on the oil type).
• When the oil cools and its saturation limit is exceeded, the excess water transitions into emulsified or free water.

Karl Fischer Testing and Free Water

• The Karl Fischer test measures the total water content, including dissolved and emulsified water in the sample.
• If the oil temperature during sampling is low, and the water has separated as free water: The test may not accurately reflect the presence of free water if it is not properly mixed into the sample. Free water typically settles at the bottom of the tank or reservoir and may not be captured unless the sampling method ensures homogeneity.

Practical Scenario with 200 ppm

1. At Higher Temperatures:

200 ppm might be below the saturation point, meaning all water remains dissolved or emulsified. There will be no free water.

1. At Lower Temperatures:

• If the oil's saturation limit drops below 200 ppm due to cooling, the excess water (above the saturation limit) will precipitate out as free water. For example:If the saturation limit at the cold temperature is 100 ppm, the extra 100 ppm will become free water or form an emulsion.
• Karl Fischer will still show 200 ppm because it measures total water in the sample, but it won't reveal how much is free or emulsified.

Indicators of Free Water in Cold Oil

• Visual Inspection: Hazy or cloudy oil, or a distinct water layer at the bottom of the tank or container.
• Sampling Issues: Free water might settle quickly, so a poorly mixed sample can misrepresent the oil's true water content.
• Temperature Drop Test: Cooling the oil artificially can highlight free water formation if saturation is exceeded.

Key Takeaways

• Yes, cold oil can have free water even with a Karl Fischer result of 200 ppm because the test doesn't distinguish between water forms (dissolved, emulsified, or free).
• To confirm free water, use: Visual inspection or bottom sampling of the tank.
• Centrifuge testing to separate water from the oil physically.
• Regular monitoring of oil temperature and water solubility limits to predict when free water may form.

Below content on Turbine Oil Water Removal and Issues would help

https://cleanoil.com/eliminating-water-contamination-101/

https://cleanoil.com/oil-and-water-shouldnt-mix/

https://cleanoil.com/steam-turbine-demulsibility/

https://cleanoil.com/products/tmr-water-removal/

https://cleanoil.com/svr-hydro/