Bio-oils, where are we now under the 2013 VGP?

Hydraulics for deck machinery and ballast systems must use EALs if the ship is likely to visit US waters
Hydraulics for deck machinery and ballast systems must use EALs if the ship is likely to visit US waters
Patrick Lämmle
Patrick Lämmle
Industry Database

Following the entry into force of the US EPA’s Vessel General Permit (VGP) on 19 December 2013, which mandated the use of so-called bio-oils, the industry has been forced to rethink its use of lubricants if operating in US waters; Patrick Lämmle, CEO of lubricant supplier Panolin International, explains the current situation.

The US Environmental Protection Agency’s National Pollutant Discharge Elimination System (NPDES) vessels program regulates incidental discharges from the normal operation of vessels. As part of these measures, the 2013 VGP, which came into force in December, requires the use of ‘Environmentally Acceptable Lubricants’ (EALs), or so-called ‘bio oils’.

Vessel discharges were previously regulated under the VGP 2008, which refers to Section 301(a) of the US Clean Water Act, which says: “the discharge of any pollutant by any person shall be unlawful”. The 2013 VGP, authorised in March of that year and runs from 19 December 2013 to the same date in 2018, aims to control specific discharges, e.g.. fuel bunkering, ballast water, bilge water, deck run-off, greywater, chemicals, lubricants, incidental to the normal operational discharge from operations of commercial vessels greater than 79 feet (24m) in length.

For lubricants, the Permit is written around two main criteria:

1) To protect US waters and reduce the impact of lubricants entering the environment. This requirement concerns all lubricants with “oil-to-sea interface”, so mainly hydraulic fluids, oils and greases in the machinery of the vessels - typically: CP propellers, stern tubes, stabilizers, rudder bearings, azimuth thrusters, and propulsion pods, wire rope and other mechanical equipment subject to immersion and deck runoff.

The previous (2008) VGP stated that environmentally preferable lubricants should be used, but the new 2013 VGP states that every ship operator navigating in or entering US waters must use EALs in all applications with “oil-to-sea interface”

2) Obviously, safety of operation of vessel equipment is paramount. The VGP goes on to state that EALs must be used “unless technically infeasible”. Technical infeasibility means that:

  • no environmentally acceptable products are approved for use in a given application that meet manufacturer specifications for that equipment;
  • pre-purchased lubricated products (e.g. wire ropes) have no available alternatives manufactured with environmentally acceptable lubricants;
  • products meeting a manufacturer’s specifications are not available within any Port in which the vessel calls; or
  • change over and use of an environmental product must wait until the vessel’s next dry docking.

If the vessel operator considers the use of EALs ‘technically infeasible’ in machinery, the reason(s) for this must be documented in the vessel’s record book and the use of non-EAL stated in the vessel’s annual report.

There are many environmentally acceptable lubricants available to replace mineral based lubricants (both in terms of performance and availability at ports) and many existing vessels can use environmental products that are compatible with existing equipment, therefore it is technically feasible for most existing vessels to use environmentally friendly lubricants.

There are however, critical systems for propulsion, steering and stability, with oil-to-sea interfaces, that manufacturers must ensure continue to perform satisfactorily. These OEMs are in the middle of the action, between the regulations and the vessel operators. With many differing EAL types now becoming available and the lack of long-term service experience, quite rightly, the OEMs are taking their time to evaluate what is on offer – particularly with respect to basic lubrication performance and, importantly, compatibility with sealing materials. Therefore, environmental acceptance and operational performance are conjoined by the type of base oil and the type(s) of performance additives that are in the lubricant.

An ‘Environmentally Acceptable Lubricant’ means lubricants that are:

  • ‘Biodegradable’ – measured by changes in dissolved organic carbon, carbon dioxide and oxygen, over a certain time span;
  • ‘Minimally-toxic’ (to algae, daphnia, fish etc.); and
  • not ‘Bioaccumulative’ (referring to the build-up of chemicals in organisms).

Additionally, there must be no visible ‘sheen’ on the surface of the water (an iridescent ‘rainbow’)

EALs differ from the mineral fluids, oils and greases currently used in several respects. Firstly there are different base oil types/categories. Previously, the most important feature for operators was the technical performance. With the new VGP requirements there is another aspect to a lubricant that requires careful consideration - the so-called ‘eco-tox’ profile. It is a fact that the classic mineral oils with their additives do not meet these requirements; therefore the EPA has named three product groups as possible environmentally acceptable alternatives to mineral oils: HETG, HEPG and HEES.

HETG (Hydraulic Environmental TriGlyceride) oils use vegetable base oil, a choice that may seem obvious. Vegetable oils can certainly be used instead of mineral oils in the very wide application field of open lubrication systems. For closed lubrication systems such as gearboxes, hydraulics and engines however, vegetable oils are unsuitable because of their sensitivity to ageing and high temperatures. They have to be changed much more often than mineral oils because of ageing - vegetable oils used for too long cause deposits and lacquering that can cause premature failure of machine components.

Also, under high temperature operating conditions, vegetable oils can polymerise so rapidly that a viscosity class ISO VG 32 fluid turns into a sticky mass like chewing gum.

The reason for this very limited resistance to ageing and high temperatures lies in the chemical structure of vegetable oils. They are unsaturated and their service life can only be extended to a limited extent with additives, nowhere near as long as that of mineral oils. Even in closed lubrication systems with sump temperatures below 60°C, local temperatures can be high enough for vegetable oil based lubricants to become thermally overloaded and cause lacquering. Furthermore, this phenomenon is not necessarily detectable by regular oil changes and analysis, particularly in systems with a large oil capacity. If HETG oils are used in closed systems, it is imperative to regularly check critical components by endoscopic inspection or by opening pumps, valve blocks or gearboxes.

Vegetable oil based lubricants meet environmental requirements such as Blue Angel (RAL-UZ 79) or the Euromargerite, both with regard to biodegradability and toxicity to water organisms, fish and algae. And, by definition, vegetable oils are renewable resources.

If accidentally released into natural waterways, vegetable oils float on top but do not form the feared rainbow coloured film characteristic ofmineral oils. They rapidly decompose on the water surface, but can still be located.

HEPG (Hydraulic Environmental PolyGlycol) oils, or Polyglycols (PAG), have been used successfully for several decades as synthetic lubricants in, for example, worm drives. Mixed with water, very high viscosity polyglycols can be used as fire-resistant HFC hydraulic fluids.

When biodegradable hydraulic fluids were first introduced, they included some polyglycol based products. However, despite reasonable tribological properties and good rheological (flow) characteristics, they are seldom used now. This may be due to general problems such as adverse or limited compatibility with seal and hose materials, paints and varnishes. Particular account must be taken of the water-soluble nature of these fluids. They accumulate dissolved condensate, which can cause filter blockage, corrosion and even cavitation damage to pumps.

Experience over the years has shown that polyglycols are difficult to keep under control under normal use. Their disappearance from the market is most likely due to the sum of all operational risks, and above all when changing over from mineral oils. For cost reasons and to reduce risks (e.g. incorrect filling), any lubricant needs to be integrated into the overall maintenance and lubricants concept.

No polyglycol based hydraulic fluids have been certified to Blue Angel (RAL-UZ 79), Swedish Standard SS 15 54 34 or European Ecolabel. PAGs are produced from crude oil and do not therefore meet the requirement for renewable resources.

HEES (Hydraulic Environmental Ester Synthetic) oils, synthetic esters (esters are derived from carboxylic acids), are available in both saturated and chemically unsaturated forms  – ‘saturated’ meaning that the acid that the ester was derived from has no carbon-carbon double bonds in its chain. If the acid has just one carbon-carbon double bond somewhere in the chain, the ester is called ‘unsaturated’.

The technological performance of unsaturated synthetic esters lies between that of vegetable oils and saturated synthetic esters. For demanding requirements, they can be used instead of vegetable oil based lubricants. Oil change intervals and maximum operating temperatures must however be precisely monitored. Unsaturated esters are subject to the same drawbacks as HETG lubricants: rapid ageing leading to deposits and lacquering, with costly downtimes for system cleaning and replacement of components.

Saturated Synthetic Ester (SSEs), in combination with selected additives, have been available from Panolin, a Swiss manufacturer of environmentally considerate lubricants, for over 25 years and are frequently used for high-performance systems such as modern hydraulics, bearings and gearboxes. Their compatibility with the standard components in modern machinery is good. The ageing stability and high-temperature resistance of saturated ester based high performance lubricants are superior to those of classical mineral oil and unsaturated ester based lubricants. They are resistant to ageing, and cause no deposits or lacquering even at high temperatures, thus enabling longer oil change intervals, even extending to one, lifetime filling. Also, with a different viscosity index profile from mineral oil, SSEs do not ‘thin’ at elevated temperatures like mineral oils. These advantages have led to saturated ester based lubricants, and in particular hydraulic fluids, taking a significant ,market share over the last two decades. SSEs have been in use in stationary hydraulic systems for over 20 years without an oil drain and have exhibited exemplary performance, even under the harshest of climatic conditions.

In mobile equipment, such as dredging equipment and ship hydraulics, 10,000 to 20,000 working hours have been clocked-up without oil drain, under extremes of temperatures and high humidity, in and near water

SSEs, with reduced (or potentially zero) need oil changes contributes to reduced CO2 emissions, particularly when the reduced need for disposal of used lubricant is taken into account.  

SSE lubricants meet environmental requirements such as Blue Angel (RAL-UZ 79) or Euromargerite [Ecolabel], both for biodegradability and for toxicity to water organisms, fish and algae. Synthetic esters are produced from a combination of crude oil and plant material, meeting renewable resource requirements. If accidentally released into natural waterways, Panolin’s selected ‘base’ synthetic esters (specific gravity 0.91-0.95) float on the surface, where they decompose rather than forming any prolonged rainbow coloured film and spreading ‘slick’ as with mineral oils. Neither do they sink to the sea bed, so life on the ocean floor is protected.

From technical and environmental points of view, Synthetic Esters (HEES), of the saturated type, with the right combination of appropriate additives, are considered to offer the best replacement to mineral oils. Although technical performance of lubricants is well documented, the eco-tox profile is a new area and themes such as biodegradability and eco-toxicity to different species are still being investigated. EPA mentions in its draft some eco-labels such as Blue Angel, European Ecolabel and Swedish Standard. Compliance with one of these standards represents the easiest way to choose an EAL which meets the  VGP requirements. Responsibility for eco-tox details lies with the lubricant manufacturer rather than the end-user – simplifying life for the vessel operator, the enforcer (the US Coast Guard) and the environment.

Only an EAL (without mineral oil residue in the tank) will have the full beneficial eco-tox properties – and not leave the characteristic mineral oil ‘slick’. It is therefore recommended to completely drain the old mineral oil - ISO 15380 recommends a maximum residual mineral oil content of 2% - and to flush the with a reduced volume of the ‘bio-oil’, before filling with bio-oil.

As previously mentioned, synthetic ester based lubricants have been available and in service for over 25 years, and have been proven to be compatible with a variety of hydraulic seal materials. Most existing marine seals materials such as stern tube seals use high quality, man-made polymers which will not suffer from the use ofenvironmentally considerate synthetic esters in combination with appropriate additives. Compatibility charts with NBR, Viton and other standard elastomer materials are available.

Appropriate monitoring of oil condition and preventive maintenance is recommended, with regular laboratory checks to indicate excessive water or dirt content. Proper maintenance should minimise risk of discharges of lubricants. It is important to remember that even using an EAL does not authorise the discharge of any lubricant, as defined in EPA 40 CFR Part 110.

The good news is that EALs may cost less than conventional lubricants. When cost is understood as purchasing price over the life of the lubricant, a top-tier environmentally acceptable saturated synthetic ester will reduce lubrication cost compared to the classic mineral oils, because its oxidation stability combined with oil monitoring, allows extended periods between oil changes – sometimes up to a lifetime fill.

This is particularly applicable for comparatively under-stressed conditions such as stern tubes, which can benefit from extended tailshaft survey intervals.  High pressure hydraulic and gearbox applications will need more frequent oil changes, though no more than with conventional oils.

With enhanced operating efficiency, down-time is reduced. A change to water lubrication is an option for shaft seals, but costs of conversion can prove higher than replacing mineral oils with a tonne or two of SSE.

Panolin can supply, in its ‘Green Marine’ product line, hydraulic fluids for CP propellers, ballast systems and deck machinery, stern tube lubricants, heavy-duty gear oil for thrusters and stabilisers, lubricants for reciprocating, screw and centrifugal compressors, grease for cables, ropes and sliding parts, and multi-purpose greases, all of which meet EAL standards.

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