EALs: Learning from history

It sounds like a fairy tale rather than a technical article, but once upon a time – in 1989 to be exact – at German construction machinery exhibition Bauma, we were promoting our saturated ester based biodegradable hydraulic fluid.

After years of experience with chainsaw oils based on canola oil, a leading construction machinery manufacturer had started to promote canola-based bio-hydraulic fluids. A number of construction companies took up the opportunity to become ‘greener’ and started to convert their excavators. And of course, agricultural organisations and their members were euphoric about becoming suppliers to the lubricants industry.

The idea was ingenious and at first sight the formulated hydraulic fluids based on canola oil showed impressive technical data. However, what looked like a ‘win-win-win’ situation from technological, environmental and raw material production standpoints became a nightmare for many users and their machinery suppliers.

After a time, several problems – pump failures, hose failures, seal failures, sticking valves, blocked hydraulic systems, clogged filters and components covered with a lacquer coating of hardened lubricant residue – started occurring more and more. The replacement of the failed components was not enough to remedy the problems. Even extensive flushing did not remove all deposits and lacquer coatings, so that virtually the entire hydraulic system had to be dismantled, cleaned and re-assembled with new spare parts. The estimated cost across the entire industry easily amounted to several hundred million euro.

All the stakeholders had to learn that the classic test methods that had been well established over decades, for mineral oil-based lubricants, were not sufficient for testing completely new types of lubricants. What looked like good performance in some of those tests, turned into dramatic failure in the real world.

SYNTHETIC ESTERS

Panolin always refused to use canola-based oils, insisting that the unsaturated oil would not support the high temperatures experienced in machines for the operational periods demanded. The much more expensive but technically superior saturated synthetic esters we selected had exhibited no such problems.

With greater use of biodegradable lubricants following the coming into force of the (second) US Environmental Protection Agency’s Vessel General Permit at the end of 2013, stories started to be told about problems with overheating stern tube bearings on new-build vessels undergoing sea trials in Asia. These problems were occurring when EALs were used, across several vessel types, lubricant brands and shipbuilders.

The problems were apparently not occurring in vessels filled with mineral-based stern tube lubricants. Over the past year or so, there have been instances of leakage of some EALs from the stern tube – this time on vessels that had previously been in service without a history of stern tube problems – following conversions to EALs from mineral oils.

On drydock investigations, problems of wear and blistering of the stern tube seal lips became apparent. In some instances, stinking black oily sludge greeted the service engineers. This thick butter-like sludge had to be scraped out of seal cavities and the seal oil feed pipes had to be blown through with compressed air to remove it. These occurrences are happening around the world.

When we learned about the VGP, we knew that we already had the right lubricant type for stern tubes. We knew our lubricants for hydropower turbines must fulfil similar requirements. Even the ‘compatibility’ with water plays an important role in both applications. While natural esters can suffer from hydrolytic instability, our non-emulsifying saturated synthetic ester technology shows a good compatibility with water ingress, similar to the behaviour of mineral oils.

STERN TUBE FAILURES

The DNV GL joint development project with several marine insurers and the University of Sheffield at the Leonardo Testing Services facility will shed light on whether EALs are to blame – and if so, which base oil lubricant types are prone to operational failure.
We are certain that this investigation will confirm our 30 years experience.

Choosing which EALs to use in different applications in a vessel is difficult. There are five base oil types that are generally considered to be biodegradable and several blends of these lubricants available from many oil companies. Identifying those lubricants that work is a big job.

The problem lies with vessel owners with EALs in their stern tubes and other ‘oil-to-sea’ interfaces – those who need to carry cargo within US waters and Polar Regions and those who elect to use EALs as part of their social responsibility efforts. Have they chosen the ones that work? If not, it could be déjà vu, all over again.