Spectrographic Analysis

The emission spectrograph is an instrument used to analyze types and quantities of metals found in oil. Included in these metals are particles of system wear, oil additive metals and contaminant metals. Normally, 20 metals are measured by spectroscopy and reported by the laboratory in parts per million. These 20 elements are categorized below.

Wear Metals: Aluminum Cadmium Chrome Copper Iron Lead Molybdenum Nickel  Silver Titanium Tin

Additive Metals: Barium Boron Calcium Copper Magnesium Molybdenum Phosphorous Sodium

Contaminant Metals: Boron Potassium Silicon Sodium

Note that some metals fall into more than one of the headings listed.

Wear Metals
Normal and abnormal wear can be effectively traced by monitoring wear metal levels at each drain. It must be stressed that the effectiveness of diagnosing a critical situation is largely dependent on sampling frequency. This is to say that oil samples should be taken and analyzed at each drain. Routine sampling establishes base line values for each wear metal, and increases or decreases from these values give the analyst a clear picture as to which component is wearing out. For example, critical main and rod bearing wear is indicated by an increase in Lead content followed by a decrease in Lead and an increase in Copper and Tin content. This indicates that the soft Lead overlay of the bearing is worn off and the Copper babbitt material is exposed. If a sample history was not available to the analyst and only high Copper was noted, it would be impossible to tell whether the Copper was coming from a bearing, brushing, thrust washer, or oil cooler, all of which contain Copper.

Wear metal limits are established for specific lube systems by statistical analysis of similar systems. These limits are used in conjunction with trend analysis to provide the user with maintenance recommendations. Trend analysis is crucial when making accurate recommendations.  Each system establishes it's own base line wear levels depending on type of service, oil drain interval, operator technique, and many other variables. For this reason, the interpretation of wear metal analysis is best when based on a trend or history of that particular system.

Additive Metals
All quality lube oils are formulated with metal based additives that improve lubricant performance. They are blended into the oil at specific levels and change little during the usage period. Quantitative analysis of these metals serves as a quality control tool for maintenance personnel by assuring them that the oil formulation has not changed or the wrong oil has been added to the system.

Contaminant Metals
Contaminant metals are any metals that do not originate from oil chemistry or lube system wear. They include environmental debris (such as Silicon or Dirt), and additive metals from coolant (such as Sodium, Potassium and Boron). Obviously, these are not desirable elements to the lube system. Their presence in the oil indicates leaks in filtration or coolant systems.

Typical Metal Origins

Metal	Engine	Gear Box	Hydraulic
Aluminum	Pistons, Bearings,  Turbo, Blowers	NA	NA
Barium	Detergent oil additive, diesel fuel additive (anti-smoke)	NA	NA
Boron	Coolant additive, oil dispersant additive	Coolant additive, oil dispersant additive	NA
Calcium	Detergent oil additive	NA	Detergent oil additive
Chrome	Piston Rings	Gear	NA
Copper	Bearings, Bushings, Thrust Washers, Oil Cooler, Oil Additive (some oils)	Bushings, Gear	Axial Piston assembly
Iron	Cylinder, Valve Train, Crankshaft, Piston Pins	Gear, Roller Bearing	Cylinder, Vane, Gear
Lead	Bearings	NA	NA
Magnesium	Detergent oil additive	NA	NA
Molybdenum	Coating on  Rings	NA	NA
Nickel	Valves, crankshaft, ring lands, heavy fuel contaminant	NA	NA
Phosphorous	Anti-wear oil additive	Anti-wear oil additive	Anti-wear oil additive
Potassium	Coolant additive	Coolant additive	NA
Silicon	Abrasive dirt, Coolant additive, Oil antifoam additive, Seal	Abrasive dirt, Coolant additive, Oil antifoam additive, Seal	Abrasive dirt, Oil antifoam additive, Seal
Silver	Wristpin bushing (EMD engines), lube oil cooler (Silver solder)	Lube oil cooler (Silver solder)	NA
Sodium	Coolant additive, oil dispersant additive	Coolant additive	NA
Tin	Bearings Piston Plating	Bearings	NA
Titanium	Turbine blades (generally aircraft)	NA	NA
Zinc	Anti-wear oil additive	NA	Anti-wear oil additive

NA = Not Applicable

Please note that most metals originate from more than one source. This means that the analyst must look at combinations of metals to pinpoint areas and degrees of wear and contamination.