Selecting the best lubricants for offshore equipment

18 August, 2016

Reliability and long-life comes from the combined optimum high performance of the ‘chassis’ and the ‘engine/gearbox’ and is the sum of:

• The stability of the base oil viscosity and shear – with no need for viscosity improvers that can be broken-down

• Its resistance to ageing - oxidation and thermal stress – not depositing varnish, or gumming

• The stability of the dispersion of the additives and not separating, or being filtered-out

• The compatibility with seals, metals and protective coatings, to not cause component degradation, failure or corrosion

• The stability with contaminants – other oils and water – to not cause emulsions that cannot readily separate the water, that can lead to bacterial growth, bad smells and corrosion

The third and easiest decision is the cost of acquiring your lubricants. If your selection is based on lowest price, then there is the choice of the lower cost (lower performance) base oil ‘blends’. However, if you are looking at the ‘long-term game plan’, then this is where the through-life reliability of your oil gives you beneficial pay-back.

Marine and Offshore systems’ OEMs, operators and construction companies have been gathering information over the past few years about the performance issues surrounding the use of EALs. Issues such as the following have become evident with some types of EALs:

• Increasing oil viscosity – due to poor thermal stability.

• Decreasing oil viscosity – due to shear instability.

• Slime and bad smells – due to water contamination and oxidation.

• Varnish and gumming of the system – due to thermal degradation.

• Corrosion of equipment internals – due to the hygroscopic nature of the lubricant.

• Overheating of propulsion systems – questioning oil film thickness and frictional characteristics.

• Difficult filterability.

• Difficult change-over from mineral oils.

Currently, fully saturated synthetic esters are in ‘pole position’, leading the way in high performance and long-life marine lubricants; with the added benefit of being environmentally considerate and reducing your carbon footprint coming ‘free of charge’ (almost – OK, the minimally toxic performance additives come at a higher price than those used in toxic mineral oils).

It is the lubricant manufacturer’s job to tell you all about the key performance indicators of their lubricant(s) – consult them.