By John Hardy, Komatsu Australia's general manager, Condition Monitoring Services (CMS)
With trends towards extended oil life and a 500-hour oil drains as standard on some engines, increased attention to oil analysis results is essential.
Oil analysis services, such as KOWA provide critical information on the oil condition and oil characteristics.
Oil condition indicators in a KOWA report are:
-- Soot (product of unburnt fuel that is measured by light absorbance units. Soot can be sub-micron, with no adverse effects, or agglomerated, causing advanced abrasive wear)
-- Oxidation (the deterioration of the fluid by oxygen products forming acids and changing vital lubrication properties of the oil)
-- Sulphates (by product of sulpur and moisture forming sulphuric acids that attack metal and interfere with lubricant stability).
Oil characteristics include:
-- Viscosity (generally increases as oil oxidises, causing pumpability constraints, slows circulation and adversely affects load carrying properties)
-- Oil Consumption (oil will vapourise as it ages. The tell tale signs are bluish smoke emissions from the exhaust and breathers. Oxidation will increases. Oil consumed reduces the oil capacity causing the lesser volume to deteriorate more rapidly)
The following outlines some recommended maintenance practices to ensure you get the best from your extended-oil change components.
Oil/wear behaviour
As oil deteriorates, the wear metals increase proportionally.
However, wear metal increase is not clearly evident if the oil consumption is not known or reported.
Lubricant stress
Oil is vulnerable to rapid deterioration in extended periods, particularly towards the end of its service life.
Increased temperatures and pressures within the engine, usually determined by fuel burn rate, will cause extreme stress on the lubricant which in turn, increases the deterioration rate.
Component failure when the oil has reached a stage of advanced deterioration is usually catastrophic, with serious surface damage from impact fatigue, seizure and heat-related phase changes to metal components, preventing their reusability.
Oil sampling intervals
To monitor these vital changes to lubricants subjected to extreme operating conditions, oil samples MUST be taken at the normal 250-hour intervals, or as determined by CMS.
The KOWA result may indicate problems before the scheduled oil change period.
If this is the case, then the scheduled oil may have to be reduced if the engine is to achieve the desired component life.
Oil changes
It is strongly recommended that the first oil change on a new component is carried out at 250 hours, regardless of the oil change schedule.
New components `run in`. This is when running surfaces find their own contours with their mating surface.
Running in results in particle debris in the lubricant that passes through the entire system.
In addition to this, external contaminants (predominantly dirt) are introduced when a component is built and fitted.
Dirt is a form of silica which is harder than steel and will act as an abrasive between mating surfaces.
Surface damage will affect lubrication behaviour and overall machine performance.
This contamination should be flushed through the system with an oil change, and not left in the component for extended periods.
Filtration
The correct filtration system is essential for contaminant control with regard to particle containment (not removal), fluid volume and flow rate.
Unfortunately, filters do not capture all particles, as particles do no conform to definite shapes and sizes.
Particles are generated from many wear regimes and mechanisms and filters are only rated with an average efficiency.
Filters cannot prevent oil from deteriorating as deterioration is a chemical and not a physical aspect of the fluid.