Distillery - Decanter Centrifuge Bearing Reservoir
Incorrect Oil Make-up causing Bearing Corrosion
Lubrication management can be key in some facilities to mitigate the effects of incorrect oil top-ups and the subsequent effects on the units themselves. In this case study there is ample evidence of repeated top-ups with an incorrect oil type and grade. In fact, the unit resides within close proximity to the Decanter Gearbox, and it is somewhat safe to assume from this oil analysis data that at regular intervals the EP gear oil is being added to the bearing reservoir as well.
Figure - Viscosity increase in plant machinery is usually a result of incorrect oil top-up as was the case with this bearing reservoir that was topped-up with ISO 220 EP Gear oil.
After a significant top-up with gear oil, evidenced by the sudden increase in viscosity and additive levels (additive levels were not shown in this example), it can be noted that the Acid Number (AN) level rises in subsequent samples. Delayed, but also evident, is the increase in copper level in the months following top-up with gear oil. The reason in this instance is that the Extreme Pressure (EP) additive in the gear oil is not only corrosive, but exceptionally corrosive to copper components.
Figure - Frequent top-ups with EP gear oil caused long term corrosion problems in this bearing reservoir evidenced by the dramatic increase in copper levels after the first viscosity increase.
Training is a key issue in this instance. Although the reliability group would not suspect that an oiler would intentionally add gear oil to a bearing reservoir, it is often the case that the oiler may not know of the consequences of those actions. The oiler may feel that oil is oil, and if a system is low and gear oil is on hand, then that is sufficient. It`s worth noting that since 04-03-2002 two more dramatic contaminations with gear oil have occurred in this system.
Diesel Engine - Fuel Dilution
Injector Issue causing Scuffing Wear in Engine
Testing an engine oils viscosity at 100°C can quickly identify abnormal contamination and oil condition. Decreases in viscosity indicate fuel dilution or top-up with a lighter grade oil, while increases in viscosity indicate excessive soot generation or top-up with a heavy grade oil. When the viscosity is out of specification additional testing will be done to determine the cause of the viscosity change (i.e. Gas Chromatography for fuel dilution, FT-IR for soot concentration, etc.).
Figure - Increases in fuel dilution will lower the oil`s viscosity and lead to scuffing wear in an engine.
During routine oil analysis an increase in fuel dilution from 0.0% to 12.0% was detected by the precipitous drop in the viscosity at 100°C from 14.0 cSt (the typical value for this oil) to 7.9 cSt. The sample is from a Caterpillar 3176 diesel engine. The engine was showing a substantial increase in the iron level by the time the oil showed 12.0% fuel dilution.
Figure - Modern common rail fuel hardware for diesel engines are sophisticated systems. Problems can develop, including leaking injectors, that cause fuel dilution of the oil, and if severe enough, scuffing of engine components.
When oil analysis detects severe fuel dilution an inspection of the fuel rail system and fuel injectors is necessary to correct the cause of the fuel dilution. Severe fuel dilution, left undiagnosed and/or untreated will lead to catastrophic engine failure.