Weighing up the risk of EALs

Malcolm Latarche

Malcolm Latarche · 28 November 2019

ShipInsight


Owning and operating ships is never the easiest of businesses to succeed in. Even if the owner has been in the same sector for many years, there are always changes in trading patterns to cope with and delicate balancing acts to perform. Ships are long-term assets purchased with hard earned money and in most cases, the owner is dependent on satisfying customers for economic survival.

Over the last 20 years or so, environmental concerns have become a driving factor in new regulations and also, to some extent, in influencing the operating philosophies of shipowners. The public image of shipping has been tarnished due to often unfair allegations of an uncaring attitude by shipowners.

In fact, shipowners have invested many billions of dollars in clean technologies and will be spending many billions more over coming years. In some cases, the money spent in attempting to meet an environmental objective – whether voluntarily or in response to regulations – has proven to be a bad decision, with the result not coming up to expectations. This may not always be the fault of the owner, or indeed of the equipment maker, but is sometimes due to poorly drafted regulations.

Ballast water management is a good example of this, with many of the early systems developed to meet the requirements of the 2004 Convention proving to be problematic in operation. Partially this was because the type-approval process was not sufficiently robust to detect problems, that became apparent only after systems were used under normal operational conditions. Differences between the approval process in the US and the IMO process did not help in this regard.

Rather than incurring the expense of installing a system that would not meet the requirements of the convention or which would prove unreliable, many shipowners took advantage of the slow ratification of the convention and delayed installing a system. That is not to say that they ignored environmental concerns, as there was the ballast exchange process which also reduced the risk of species transfer. Hopefully with a revised approval process and a new installation timetable in place, the problems of the past will not be repeated.

The impending sulphur in fuel reduction at the start of 2020 is another area where balancing environmental concerns with operational efficiency is paramount. Some owners of new ships are installing engines that run on LNG or another alternative, others are fitting scrubbers and continuing to run on HFO while most will be obliged to use compliant fuels. All of these involve additional outlays. How exactly the operational efficiency and environmental consideration argument will play out remains to be seen, but each owner must decide based on their own philosophies and resources.

Some of the bigger decisions are yet to be made as the IMO’s ambitions to decarbonise shipping are realised. Can the shipping world afford to upset customers demanding just-in-time deliveries by slowing down to reduce emissions? And if they did, could they afford the cost of building additional new ships to ensure capacity is still there, especially as that could easily hit a figure of $100 Bn?

All of the examples cited above involve very large sums in both capital outlay and operational costs, but there are smaller – but not less important decisions – to be made, as well in balancing environmental and operational considerations.

Almost all modern industries have some environmental impact and regulators must balance the ability to reduce the impact with the necessity of the industry being regulated. Shipping is no different in this regard. That was recognised by the US authorities with the introduction of the Vessel General Permit (VGP) in 2008.

The VGP is an anti-pollution regulatory regime, but the permit element is a recognition of the fact that some ‘Discharges Incidental to the Normal Operation of Vessels’ are inevitable. While the permit issued to any ship is therefore technically a licence to pollute, the extent of allowed pollution is very strictly defined and enforced.

One area where the VGP introduced new requirements on vessels is in the use of environmentally acceptable lube oils (EALS). These rules became effective in December 2013 and apply to all lubricants that could be released into the marine environment. This includes lubricants used in the stern tubes of ships and in thruster applications.

On the whole, shipowners complied with the regulations once issues of compatibility with stern tube seals had been resolved. They did this either by way of retrofitting water lubricated stern tube bearings or by adopting EALs. There may have been some mistrust of the efficacy of EALs, but having been given assurances that they were compliant and safe, owners had little reason to doubt that was the case.

Dualguard1
Wärtsilä Airguard seal section view

After several years of EAL use, reports began to surface that there were problems associated with their use. Studies have been initiated into investigating and understanding the problem, the most notable of which is that involving DNV GL in a joint development project (JDP) that began in January 2018 and which involves four P&I clubs, the UK’s University of Sheffield and the Institut National des Sciences Appliquées of France. Phase one (of three) was completed in December 2018.

DNV GL has not released the full report, but used some of its findings in a webinar on 29 October called ‘Environmentally acceptable stern tube lubricants – How to avoid costly failures’. In the presentation, DNV GL said in the first couple of years after EALs became mandatory, its own data shows that the percentage of vessels using EALs in stern tube bearings rose from 6% in 2013 to 47% in 2015, but has since fallen each year and stood at 22% in 2018. However, these figures relate only to ships that have adopted the class society’s tailshaft monitoring notation TMON, so may not be representative of the world fleet.

One possible reason for the drop in EAL use was operators experiencing problems with this lubricant, prompting them to explore alternatives such as void space seals such as Wärtsilä’s established Airguard seal. The pressurised air in the central void space is dynamically controlled and monitored, based on the variations of the seawater pressure, which keeps the Wärtsilä Airguard system continuously pressure balanced. More importantly in light of the continuing issues surrounding EALs, the Wärtsilä Airguard has been designed to operate using mineral oils and is permitted for use because of the void space and drainage system.

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Typical piping diagram of aft seal of the Wärtsilä Airguard system

The problems experienced with EALs do not involve a single reason. Some ships that were affected were recent deliveries, and it is thought that sea trials had been conducted using mineral oils which was then replaced with the EAL, without thorough cleaning and removal of all traces of mineral oil. It is known that some EALs will react with mineral oil to form sludgelike deposits. Another likely cause was that failures occurred during manoeuvring, when large downwards-acting bending moments on the propeller affect how the load is distributed within the aft stern tube bearing.

With conventional oils, when the pressure is increased in an oil film, its viscosity will increase. As a result, resistance towards a breakdown of the oil film will increase as the bearing is loaded. The JDP found that EALs do not have the same relationship between pressure and viscosity, as mineral oils and an EAL will have a lower viscosity for a given pressure than a mineral oil would in the same situation.

Temperature also has a different effect on viscosity for the two types of oil, the research found. EALs have a higher viscosity index than mineral oils, which means their viscosity is less affected by temperature than mineral oils. In temperatures below 20°C, for example, EALs have a lower viscosity than the equivalent mineral oil, giving them a lower safety margin.

As a result of the work, DNV GL revised its oil film lubrication criteria that are used to determine the minimum shaft speed required to establish and retain an oil film of acceptable thickness. The formula now includes a viscosity parameter that takes one of two values, depending on whether mineral oils or EALs are used, which has the effect of setting a higher minimum RPM when EALs are being used. This has been applied to all DNV GL newbuilding assessments since July this year.

A ship which experiences a stern tube failure or damage to the shaft will suffer inevitable operational problems with delays occurring. Speed may have to be reduced to prevent further damage, and there will be a need for the seal to be replaced and any damage repaired. In the worst-case scenario, this may even involve dry docking the ship.

Although there now appears to be an acknowledged issue with EALs, the USCG and the EPA have no plans to change the regulations. The delay in bringing out the newest VGP is to do with other matters and not a desire to draw back from pollution prevention measures.

Ships that are not fitted with seals such as the Wärtsilä Airguard, will be obliged to continue operating using EALs. However, operators who are reassessing the risks of compliance with the VGP by relying on EALs and weighing up the potential for lost revenue, might contemplate the benefits to be gained from a retrofit and the ability to use mineral oils for the inboard side lubrication.

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