Engine Oil Analysis

Engine Oil Analysis Essintial to turbine engine longevity By Joe Escobar March 2001 Routine oil analysis has become quite the standard in our industry. Many of the engine manufacturers recommend regular sampling as part of a preventive...


Engine Oil Analysis

Essintial to turbine engine longevity

By Joe Escobar

March 2001

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.

Handle with care
ImageOne 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.

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 sampling
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.
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 their test, an Inductively Coupled Plasma (ICP) Spectrometer is used to measure amounts of elements present in the oil. The sampled oil they receive 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 9000 degrees Celsius, 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.

Oil filter analysis
Rory Hammond, owner of Aviation Laboratories in Kenner, LA, stresses the importance of oil filter analysis. "The oil filter analysis is able to detect and identify the larger contaminants that are present in the oil," says Hammond. "If an engine is experiencing wear that produces particles larger than 10 to 15 microns, a spectrometer analysis is not going to detect all of it, since most turbine oil filters remove debris down to 10 microns in size. Unless the customer includes an oil filter analysis, some types of problems may go undetected."
Performing an oil filter examination is a structured inspection. The lab technician removes the oil filter from the shipping container and plugs it to prevent any contamination from entering the interior of the filter. He then places it in a clean container, adds a solvent to it, then shakes it to dislodge any debris in the filter. The particle-laden solvent is then passed through a patch filter and the step is repeated. After these initial solvent washes, the filter and container are placed in an ultrasonic cleaner to remove any remaining contaminants. This solution is also passed through the patch filter. The oil filter is then carefully inspected for any debris that may still be present and it is removed as necessary. Now the particle analysis begins.

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