Inductively coupled plasma atomic emission spectroscopy (ICP-AES) is an essential tool in oil condition monitoring used for detecting the presence of atomic elements of metals and metalloids contained within a sample. These elements correspond directly with component wear metals, contaminants and additives and serve as predictors of possible system wear and mechanical issues as well as reveal the additive technologies contained within the fluid.
An ICP-AES works in the following manner. Samples are delivered by a peristaltic pump to an analytical nebulizer where it is changed into a mist. This mist is then delivered directly into a plasma torch where the molecules are broken down into their constituent atoms and excited. These elements then release their excess energy in the form of photons that produce radiation at the wavelengths associated with those atoms. A photodetector will measure the intensities of all of the respective wavelengths simultaneously.
For oil condition monitoring, the ICP-AES is set to detect 19 atomic elements contained within the solution and all particulate under 8 microns in size. The results are reported in parts per million. A data analyst will then interpret the data to determine the source and severity of the wear and will be able to identify the additive package to ensure that the correct oil type is in use.
SOURCES OF ELEMENTS IN COMMON MACHINERY
||Cylinders, crank, camshaft, liners, valve train, oil pump||Gears, shaft, bearing, housing||Gears, discs, housing, shafts, brakes||Pump, cylinders, rods, pistons, bearings|
|Cr (Chromium)||Piston rings, alloys, exhaust valves, taper bearings||Roller bearings, shafts||Roller bearings, shafts||Rods, cylinders, pistons, shafts|
|Ni (Nickel)||Valves/valve train, alloy in crankshaft, cams||Steel alloy from bearings/shafts||Steel alloy from bearings/shafts||Valves, turbine blades, pump, spools|
|Pistons, turbocharger, bearings, dirt contaminant||Pumps, thrust washers, dirt contaminant||Torque converter, pumps, thrust washers, dirt contaminant||Bearings, pump motor housing, thrust plates, pistons, dirt contaminant|
|Pb (Lead)||Bearings, bearing overlay, bushings, main/connecting rod bearing allo||Roller bearings cage metal||Clutch plates, bearings, bushings||Bearings, bushings|
|Cu (copper)||Main/connecting rod bearings, oil cooler tubing, brass or bronze bushing alloy||Brass or bronze bushing alloy, roller bearing cage, thrust washers||Clutch plates, oil cooler copper tubing, brass or bronze bushing alloy||Bearings, bushings, thrust washers, oil cooler tubing|
|Sn (Tin)||Main/connecting rod bearing alloy, bearing overlay, bushings, flashing from pistons||Bearings, bushings, solder||Brass/bronze bushing alloy||Bearings, bushings, solder|
|Ag (silver)||Solder, wrist pin bushings in electromotive diesel engines||Solder||Trace element in needle bearings, oil cooler solder||Solder|
|Ti (Titanium)||Oil additive, valves, bearings, shafts, paint coatings||Gears, shafts, bearings, paint coatings||Gears, shafts, bearings, paint coatings||Valves, piston pins, turbine blades, gears, shafts, bearings, paint coatings, heat exchanger|
|Si (Silicon)||Dirt (silica), silicone-based sealant, silicates from anti-freeze, siloxanes (landfill gas), anti-foam additive||Dirt (silica), silicone-based sealant||Dirt (silica), silicone-based sealant, silicates from anti-freeze||Dirt (silica), silicone-based sealant, silicates from anti-freeze|
||Oil additive||Oil additive||Oil additive||Oil additive|
||Antifreeze inhibitor, salt water, spray wash||Salt water, spray wash||Antifreeze inhibitor, salt water, spray wash||Antifreeze inhibitor, salt water, spray wash|
||Antifreeze inhibitor, potash from charge air cooler||Oil additive, salt water contaminant||Antifreeze inhibitor, salt water, spray wash||Anti-freeze inhibitor, contaminant from potash mining|
||Friction modifier additives in oil and grease, molybdates from coolant, piston rings plating, crosshead exhaust vale seat, valve spindle||Friction modifier additives in oil and grease, molybdates from coolant||Friction modifier additives in oil and grease, molybdates from coolan||Friction modifier additives in oil and grease, molybdates from coolant, heat resistance alloy in turbine rotors, boiler tubes|
||Anti-wear additive (ZDDP)||EP additive||Anti-wear additive (ZDDP), phosphate ester||Anti-wear additive (ZDDP), phosphate ester|
||Anti-wear additive (ZDDP), galvanized steel from filter canisters, alloy in brass||Anti-wear additive (ZDDP), galvanized steel from filter canisters, alloy in brass||Anti-wear additive (ZDDP), galvanized steel from filter canisters, alloy in brass||Anti-wear additive (ZDDP), galvanized steel from filter canisters, alloy in brass|
||Detergent/dispersant additive||Detergent/dispersant additive||Detergent/dispersant additive||Detergent/dispersant additive|
||Detergent additive||Demulsifying agent, synthetic oil additive, drilling application contaminant||Drilling application contaminant||Demulsifying agent, synthetic oil additive, drilling application contaminant|
||Detergent/dispersant additive, alloy metal, environmental contaminant||Detergent/dispersant additive, alloy metal, environmental contaminant, engine oil contaminant||Detergent/dispersant additive, alloy metal, environmental contaminant||Detergent/dispersant additive, alloy metal, environmental contaminant, engine oil contaminant|
The acceptable levels of wear metals vary greatly depending on the component, the application, the amount of time the oil has been in service, the presence of external contamination and many other factors. Some manufacturers have established limits for their components which can be directly acquired from that manufacturer, and crossing the thresholds of their limits may indicate excessive wear. However, any significant increase in a wear metal should be monitored closely regardless of manufacturer threshold limits. A well-trained data analyst will be able to compile all of the data and determine the condition of the component.
The level of oil additive metals will vary depending on the oil type, application, and proprietary manufacturer’s blends. To be certain of the actual additive concentrations it is necessary to send a sample of unused oil to the lab. Your oil supplier may be unwilling to provide such information, or unable to if they purchase their additive package from an additive manufacturer. However, we can commonly expect to see certain levels of additives based upon the oil’s application:
Zinc and phosphorous (ZDDP) - 700 to 1200 ppm
Calcium or magnesium (detergent) – 1000 to 4000 ppm
Silicon (antifoam) – 3-10 ppm
Phosphorous (EP additive) – 250 to 2500 ppm (high Sulphur)
Transmission fluid (ATF):
Phosphorous and calcium – 100 to 500 ppm
Hydraulic oil (AW):
Zinc and phosphorous (ZDDP) – 200 to 500 ppm
Calcium 50 to 300 ppm
Sodium and/or phosphorous at >50ppm may indicate the presence of coolant.
Not every manufacturer’s oils will fall within these exact ranges but we should expect to see this type of additive concentrations for these applications..
OTHER ELEMENT SOURCES
Silicon – may be present not only as an antifoam additive in small amounts but is commonly leached into the oil in the form of silicone from gasket sealant (25 to >100ppm). With heavy coolant contamination it may be present as silicate. Engines powered by landfill gas will see high quantities (100ppm or more) present in the form of siloxanes.
Copper – when present in high concentrations in the absence of other alloy metals this is typically sourced to oil cooler passivation in the form of oxides and sulfates (engines, transmissions, hydraulics). Copper combined with significant zinc indicates brass component wear/corrosion. Copper combined with significant tin indicates bronze component wear/corrosion. In engines, copper present with lead and tin indicates main/connecting rod bearing wear.
Sodium, calcium and magnesium – when increases in these elements are seen along with water contamination it may indicate the presence of salt water/sea spray or road salts.
The Bureau Veritas laboratory will be able to analyze all of the elemental data along with other physical tests to determine the overall condition of the component.
Bureau Veritas - Oil Condition Monitoring