contamination, chemical content and viscosity. A vast amount of money is spent annually replacing machinery components that have worn out due to the inability of the lubricants to perform their required task. Knowing how to interpret changing lubricant properties is the task of the diagnostic and maintenance engineer and can increase both the working time and the life of often highly critical capital equipment. The existence or amount of debris and particles from wearing parts, corrosion, erosion and contamination, provide clear information about the issues affecting performance and reliability. Lubricant and other key fluid analyses provide critical early warning information indicative of machine failure. Analysing and trending the data means maintenance can be


scheduled before a critical failure occurs. The result of such good practice is higher equipment availability and productivity, lower maintenance costs, lower total cost of ownership, less downtime, optimal equipment performance and a greener operation.


Common In Service Oil Analysis Techniques


The author’s experience has been confined to the marine field but this paper, although marine orientated, applies equally well to land-based machinery.


The table below shows typical oil analysis parameters and common analytical techniques to monitor machine wear, contamination and degradation.


Key oil analysis parameters and corresponding analytical techniques CATEGORY


KEY ANALYSIS


Fine wear metal elements


Machine wear


Large wear metal elements


Particle count and distribution


Wear particle shape analysis


Sand and Dirt Fuel Dilution Contamination


Water/Moisture Glycol/Coolant


Soot Alien Fluid 78 | The Report • March 2020 • Issue 91 ANALYTICAL TECHNIQUES


Rotating Disc Electrode (RDE) Spectroscopy, Inductive Coupling Plasma (ICP) Spectroscopy


Rotrode Filtration Spectroscopy (RFS), FPQ, XRF


Particle count, Laser Net Fines (LNF)


LNF, Ferrography, Wear Debris Analysis (WDA)


Particle count, Laser Net Fines (LNF)


Fuel Sniffer, Gas Chromatography (GC)


Infrared (IR), Karl Fischer Titration (KF)


Infrared Spectroscopy Sootmeter, Ir IR


It is always good practice to advise relevant personnel to require oil samples to get an idea of the status of wear on machinery.


If the person


accepts that advice, the diagnostic or maintenance engineer should further advise his client, he has a subject clause his next moves of “subject to a favourable oil analysis”. Should he not avail himself of such advice the engineer will have closed off any avenue of legal action against himself.


Any machine is kept running smoothly by the addition to the sump of lubricating oil. This is pumped around inside the engine by means of an oil pump which is usually mechanically driven and inside the sump and the oil passes through a filter, over every bearing and down each cylinder wall. The oil is kept at a reasonable working temperature by-passing through a heat exchanger which is often fitted in tandem with the cylinder jacket water heat exchanger. The actual arrangement varies from engine type to engine type and from manufacturer to manufacturer. By-passing through the engine in this manner the oil takes into a loose solution of tiny particles of wear metal from the bearings and combustion particles from the cylinders.


In


carrying out a full survey on any machine, the diagnostic engineer should, when he is looking at the engine, check and report on the condition of the lubricating oil. The nature of the contamination or any effects it may have had on the engine cannot be accurately determined by this method but carrying out this test will certainly give the engineer confidence in suggesting that a detailed chemical analysis of the oil be made, and any recommendations of the analysing laboratory be accepted.


There are two main reasons for removing oil from service, and they are respectively:


1. pollution from outside sources, and


2. oxidation causing deterioration of the oil itself.


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