eSource 100 Iron a Focus on the Most Abundant Wear Metal

eSource 100 Iron a Focus on the Most Abundant Wear Metal

Posted 28 July 2017
Understanding where the source of iron is coming from can help in reducing the opportunity for equipment failure.
Iron is the most common element found in used oil analysis.  While iron is not an additive in an oil formula, it is commonly found as a wear debris and as a contaminant.  Dirt has up to 5% iron oxides and can be very abrasive. Iron can also be present in an oil analysis as iron oxide (rust). Iron is the foundation element in all forms of steel, which is by far the most prevalent material in lubricated components. The most common of the wear metals, it is present in some form in virtually all equipment. Its widespread presence means that there are many sources of the wear particles.  

Understanding the metallurgy of the component allows the analyst to distinguish the source of the wear debris, e.g. cast iron bolts vs. stainless steel lube oil piping. Because iron is the most common wear metal found in lubricated system, it has a high occurrence during normal wear in the form of steel.  There are a different grades of steel.  Carbon steels contain varying amounts of carbon, and small amounts of manganese and even smaller concentrations of copper. Alloy steels have a specified composition of vanadium, molybdenum, or other elements, as well as larger amounts of manganese, silicon, and copper compared to carbon steels. Alloy steel is common in many components.  Stainless steels contains Chromium providing rust resistance. Tool steels contain Tungsten, Molybdenum and other alloying elements that give them extra strength, hardness and resistance to wear.  Small concentrations of tool steel may show up in the initial oil analysis of a new component.

Iron is widely used in rolling element bearings. The rollers are sometimes alloyed with tungsten, as well as used in bearing raceways and cages.  Journal bearings use iron in the journal shaft and the bearing shoe backing. In engines, iron is the most common of the wear metals. Iron is used in the cylinder liners, piston rings, the valve train, crankshaft, oil pumps, rocker arms, spring gears, lock washers, nuts, pins, and connecting rods. Iron is also used in many engine blocks.  Gear boxes and transmissions have gears, pinions, case hardened teeth, and locking pins that all may contain high levels of iron. In transmissions, the gears, bearings, brake bands, clutches, shift spools, pumps, and power take off (PTO) units contain iron.  In hydraulic Systems, the pump assembly contains iron in the motor, vanes, pump housing.  Iron is used in the cylinder bores, rods, servo valves, and pistons.  Rotary screw compressors contain iron in the lobes, vanes, connecting rods, rocker arm, bearings, cylinders, housing, shafts, roller bearings, oil pump, and piston rings.  In turbines, iron is used in the reduction gear, shaft, bearings, piping, and the casing.  
 
There are instances when the Iron alloy material may come in contact with sacrificial metals such as Copper, Tin and Lead in bearing supported components or components with brass parts like gearboxes and pumps.  When this occurs, these metals will be present in the oil analysis result.  Increases in Iron levels as well as Calcium and Magnesium may mean contamination with Fuller’s Earth, Kitty Litter or Floor-Sweep or even hard water contamination has occurred.  Metal content in used oil is routinely analyzed using the ICP for parts per million concentrations.  The Particle Quantifier Index (PQI) instrument will detect iron content as well.  An increase in PQI over several samples may indicate a severe wear event.  Analytical Ferrography is also used to identify wear mechanisms and sources through examination of the iron wear particles.   

Understanding where the source of iron is coming from can help in reducing the opportunity for equipment failure.  ALS has several decades of experience understanding the source of Iron contamination and wear mechanisms.  Contact your local lab for more details on how oil analysis can improve your overall equipment reliability. 
 

Written By:

Michael D. Holloway MLT1, OMA1, MLA1, CLS
Manager – Strategic Accounts and External Training, Tribology

 

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