Causes and Cures for Cloudy Oil

Learn what your hydraulic equipment’s cloudy oil is trying to tell you.

Man at work in a construction siteClean oil is really important for the proper operation of any kind of hydraulic equipment. Unfortunately, there are a whole bunch of ways that oil can become contaminated. In some cases the oil will turn dark and nasty or even acquire a terrible smell. However, don’t be fooled by less dramatic changes such as the oil turning cloudy. This might not seem like such a big deal at first, but in fact cloudy oil is a sign of a serious problem.

Why Does Oil Get Cloudy?

Kids learn in science class that oil and water don’t mix. However, this ignores the fact that oil can—and does—hold a certain amount of water dissolved in solution, similar to how air holds water in the form of humidity. As “humidity” levels in oil increase beyond its saturation level, water will come of the oil causing it to take on a cloudy appearance. This hotter your hydraulic equipment runs compared to ambient temperatures, the more you have to worry about this. Hot oil can hold more moisture in solution that cool oil, so your oil may pick up more moisture as the system runs only to release it as free water when the system shuts off and cools down.

Why is Cloudy Oil So Bad?

Cloudy oil signals water contamination, and water contamination is bad because it:

  • Depletes some additives
  • Reacts with some additives to form corrosive chemicals
  • Reduces the lubrication ability of the oil
  • Increases air entrainment and cavitation damage

In short, cloudy oil leaves your hydraulic components vulnerable to damage and premature failure.

What Can I Do About It?

There are several ways to deal with a cloudy oil problem. The first step is to check and see if you have any additional sources of water contamination besides what is naturally entering the system through ambient humidity in the operating environment.

Assuming all is well with the system, you can then either replace the cloudy oil with new, clean oil, or attempt to remove the water using a method such as vacuum distillation or headspace dehumidification. In most cases an oil change is the simpler and less costly option.

Now that you have nice clear oil in your hydraulic equipment again, you need to take steps to keep it that way. The easiest approach is to improve your filtration. By installing a polymeric filter that is impregnated with a super-absorbent polymer, you can remove a little bit of moisture from the oil on every pass through the filter to help manage moisture saturation levels. The goal would be to keep moisture levels down around 50 percent of the oil’s saturation capacity.

Posted on May 28, 2015
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