Section II: OIL ANALYSIS THEORY AND BENEFITS

NAVAIR 17-15-50.1

TM 38-301-1

T.O. 33-1-37-1

CGTO 33-1-37-1

SECTION II

OIL ANALYSIS THEORY AND BENEFITS

2-1. Spectrometric Oil Analysis. Spectrometric oil analysis is a diagnostic maintenance tool used to determine

the type and amount of wearmetals in lubricating fluid samples. Engines, transmissions, gearboxes, and hydraulic

systems are the types of equipment most frequently monitored. The presence of unusual concentrations of an

element in the fluid sample can indicate abnormal wear of the equipment. Once abnormal wear is verified, the

equipment may be repaired or removed from service before a major failure of a fluid wetted component occurs.

Spectrometric oil analysis enhances personnel safety and material readiness at a minimum cost, and serves as a

decisive, preventive maintenance tool.

2-2. Physical Property Testing. Lubricant physical property testing provides data on conditions that are

standards of measurement for judgment of the quality of the oil. Physical property tests aid in determining

degradation or contamination of the lubricant which occur from combustion blow-by, oxidation from overheating,

moisture from coolant leaks, additive depletion, etc. Physical properties testing of used lubricants is primarily

utilized in ground and ship equipment applications but may also have some beneficial application to aeronautical

equipment as an adjunct to spectrometer testing.

2-3. Benefits of Oil Analysis. Data from spectrometric and/or physical property testing may be used as

guidelines to assist in identifying incipient mechanical failures or in determining the quality and useful life of the

oil. Thus, potential equipment component wear or failure and premature lubricant failure may be detected prior to

a major equipment failure or an expensive repair/rebuild. Oil analysis may also be used to identify inadequate or

improper maintenance procedures and unsatisfactory equipment parts/components/assemblies.

2-4. Wearmetals. Wearmetals are generated by friction between moving metallic surfaces in mechanical

systems. Despite lubrication, wear-metal generation occurs in all oil wetted systems to some degree and the

lubricant serves as a repository for the wearmetals. Wearmetals may also be generated from corrosive action

resulting from moisture and electrolytic action within lubricated systems. Thus, information related directly to the

condition of the assembly exists in the circulating lubricating fluid. This conclusion is developed as follows: first,

the metal particles rubbed or gouged off the metal alloy surfaces will always have the same chemical

compositions as the alloys from which they came; second, the normal level and rate of production of each kind of

metal particle can be established for each type equipment through oil analysis over a period of time. Thus, when

an abnormal level and/or rate of production of wearmetals is detected, the chemical identity of the abnormally

produced particles will provide clues concerning the identity of the parts being worn. Some metallic elements will

specifically identify an impending problem while others provide only general information that abnormal wear is

occurring, For example, increased quantities of iron are quite common since iron is present in many component

parts and the skill and knowledge of the evaluator is important in diagnosing equipment condition and the source

of wearmetal. On the other hand, increased quantities of an uncommon element such as silver may pinpoint the

trouble area directly to a single part. For a normally operating piece of equipment, wearmetals are produced at a

constant rate. In some cases, the rate may be negligible, but this rate is similar for all normally operating

equipment of the same model. The wear-metal concentration will also increase at a constant rate for a normally

operating, completely enclosed system with no fluid consumption. A theoretical plot of wear-metal concentration

in parts per million (PPM) vs operating hours is represented in figure 2-1. Any condition which alters the normal

relationship or increases the normal friction between moving parts will generally accelerate the rate of wear and

increase the quantity of wear-metal particles produced. An abnormal condition of this type will sharply increase

the concentration and rate of buildup of wearmetals in stable fluid systems. If the condition is not discovered and

corrected, the deterioration will continue to accelerate, usually with major secondary damage to other parts of the

assembly, resulting in the eventual failure of the entire assembly. (Newly overhauled assemblies may tend to

produce wearmetals in higher concentrations during the initial break-in period.)

2-1