Oil Analysis: An essential part of engine monitoring programs

An essential part of engine monitoring programs By Joe Escobar Routine oil analysis has become quite the standard in our industry. Many of the engine manufacturers recommend regular sampling as part of a preventive maintenance program. The...


Oil Analysis

An essential part of engine monitoring programs

By Joe Escobar

Routine oil analysis has become quite the standard in our industry. Many of the engine manufacturers recommend regular sampling as part of a preventive maintenance program. The oil manufacturers have also embraced oil analysis as a way to detect abnormal properties in the oil. An effective oil analysis program is usually able to detect breakdown in internal components before an actual incident occurs. It can also detect contaminants present in the oil that may lead to premature wear of components.

Keep it clean
One of the most important steps in an oil analysis program is the actual sampling technique. Whether it is taking an oil sample or removing an oil filter for analysis, everything must be done to ensure that no external contaminants are introduced into the sample. Contamination can cause false readings at the lab, therefore a clean container must be used for every oil sample.

Not only can contaminants be introduced into the oil during sampling, they can be introduced into the engine oil itself during servicing. Care should be taken to ensure no contaminated equipment is used to service oil.

In addition, certain practices can lead to contamination. One reader shared the problem that his maintenance organization encountered. The oil analysis from the engines they serviced were coming back with small traces of iron shavings. The materials were analyzed and determined not to be coming from the engine. Further investigation revealed that the particles were being introduced into the system during servicing. A metal "church key" can opener was being used to open the oil cans, and small shavings were being sheared from the can's surface and the edge of the church key and introduced into the engine through the oil. An oil servicing unit with a filter was purchased, all aircraft had their oil changed, and the problem went away.

Types of oil analysis
Once the owner or operator chooses to perform oil analysis, they need to decide what type of analysis will best suit their needs. There are several ways that oil systems can be analyzed. The most common types of analysis are oil samples, oil filter analysis, and chip detector analysis.

Oil samples
A very common practice of oil system analysis is performing routine oil samples. Usually, the samples are taken within 30 minutes of shutdown. This ensures that any particulate contamination present doesn't get the chance to settle to the bottom of the oil reservoir prior to sampling. The oil is then sent off to a laboratory for analysis.

Spectrum analysis
Most oil samples are tested using spectrum analysis. Jet-Care International of Cedar Knolls, NJ, is one lab that performs this type of oil analysis. In its test, an Inductively Coupled Plasma (ICP) Spectrometer is used to measure amounts of elements present in the oil. The sampled oil it receives is diluted. It is then mixed with an inert gas, which turns it into an aerosol. This gas is then induced to form a plasma at 9,000 C, which causes metal ions to take on energy and release new energy in the form of photons. A spectrum with varying wavelengths is then created by each element present. A machine quantifies the amount of energy emitted, and determines the concentration, in parts per million, of metals present.

While the oil spectrum analysis is a valuable part of any oil analysis program, it does have its limits. It is only effective in detecting particles smaller than 8 microns. Most oil filters are able to filter out particles above 10 microns. Therefore, to get a complete analysis, it is a good idea to perform an oil filter analysis in conjunction with the spectrum analysis.

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