GREENMARINE - Sterntube Oils

Prod. no.

Fully synthetic stern tube lubricant, biodegradable.
Applications: stern tubes as per EPA requirements for marine lubricants.
Biodegradability: OECD 301 B; > 60%. EN 16807, EPA Vessel General Permit 2013, EU Ecolabel. RINA Green Plus.

Performance grade


ABS Type Approval.
James Walker.
RM Propulsion
SKF Blohm + Voss Industries.
Versitec-Marine - Vanguard Seals.
Wärtsilä Bio-Seals.

more information ›

Stern Tube Lubricant

Without an engine, or a functional propulsion system, you don't have an operable ship. There are several types of vessel propulsion systems basic types are typically:

· Propeller shaft with Fixed Pitch Propeller (FPP)
· Propeller shaft with Controllable Pitch Propeller (CPP)
· Azimuth Thrusters – with FPP or CPP
· Propeller shaft or thruster with Ducted Propeller
· Podded Thrusters
· Water jets

Each of these types of vessel propulsion suit different vessel types, such as: container ships, bulk carriers, tankers, cruise ships, tugs, ferries, naval vessels... and some provide for better propeller efficiency and forward thrust, resulting in improved fuel consumption.

Whilst PANOLIN provides stern tube lubricant, gear oils, hydraulic fluids and greases for all lubrication requirements on all propulsion types, it is the conventional propeller shaft with a stern tube containing the propeller shaft bearings and propeller shaft seals that are most common in international merchant marine vessels.

Firstly, let's define what stern tube lubricant must do – it must lubricate the stern tube bearings, be they metallic or plastic composites and also lubricate the stern tube forward and aft propeller shaft seals. However, most importantly the lubricant must work. It must be up to the job of providing a robust oil film to support the propeller shaft in the bearings; to cushion the shaft during the relentless periods in heavy seas when the propeller and shaft are thumping around in the bearings and to not break-down allowing the shaft to make contact with the bearings. The stern tube lubricant must also be compatible with components within the stern tube system such as: sealing materials, paints, valves, various metals like white metal and yellow metals, adhesives and sealants.

Now, let's define what an 'Environmentally Considerate Lubricant (ECL; or nowadays more commonly known as an Environmentally Acceptable Lubricant – EAL) must do – it must have minimal effects on marine life; therefore it must biodegrade (not be persistent), it must have minimal toxic effect and must not accumulate in the organs of marine life, being transferred (and concentrated) up the food chain. The EAL must (undoubtedly!) also perform well in the machinery it is lubricating - as stated above.

Types of Stern tube lubricants

There has been petroleum (mineral) based oil available for over 100 years that everyone responsible for lubrication on a ship understands well. What is not so well understood is that there are generally accepted to be 5 types of lubricants that are 'biodegradable' – and there are many more 'blends' of some of these primary base oil types to combine minimum performance and give the minimum requirement for biodegradability, or to minimize cost.

You get what you pay for!

Currently, the EAL world is in turmoil, with many issues reported of poor performance of stern tube lubricants in equipment where previously mineral oils had proven to work - and particularly with instances of short life of stern tube lubricants (in some instances only 2- 2 ½ years), before acidity of the lubricant increases, viscosity dramatically increasing, or the stern tube is contaminated with stinking black sludge that blocks seal oil-feed pipes and bearing oil lubrication washways. Many vessel owners who adopted these EAL stern tube lubricants early in the current VGP2013 lifespan, either through existing vessel mineral lubricant contracts, or by salesmen's 'patter' that they have the 'best' EAL, or just by cheapest price, have fallen foul of these lower performing, short-life stern tube lubricants. Most are changing to the better performing EALs. The announcement in 2018 by DNV-GL of a joint development project with several marine insurers and the University of Sheffield in the U.K. to investigate the increase of stern tube bearing failures will shed light on whether EALs are to blame – and if so, which base oil lubricant types are prone to operational failure. Slower steaming with larger/heavier propellers requires the highest oil film performance from the stern tube lubricant.

So, how does a vessel Owner/Operator, choose the right stern tube lubricant for their equipment to provide optimum operational performance and reliability of the equipment and therefore the scheduled operational availability of the vessel?

Why is PANOLIN Stern Tube Lubricant different?

Basically, it is due to the selection and use of only one of the 5 biodegradable base oils - Fully Saturated Synthetic Ester base oil technology that PANOLIN has successfully used for over 35 years. Reliability and long-life of biodegradable oil come from the combined high performance of the saturated synthetic ester base oil and the individual additives selected.

However issues such as...

* Increasing oil viscosity – due to poor thermal stability – causing equipment overheating
* Decreasing oil viscosity – due to shear instability – causing equipment damage
* Varnish and gumming of the system – due to thermal degradation of the lubricant – causing loss of machinery efficiency
* Slime and bad smells - due to oxidation, water contamination and bacterial growth
* Retention of water in the lubricant with the 'emulsifying' EALs, again leading to slime and bad smells
* Corrosion of equipment internals – due to the hygroscopic nature of the lubricant used
* Overheating of propulsion systems – questioning oil film thickness and frictional characteristics
* Difficult filterability – separating of sea water, particularly from emulsifying lubricants
* Additive solubility issues in cold conditions, where valuable performance additives come out of solution, clump together and get filtered out of the base oil
* Difficult change-over from existing oils in equipment – due to immiscibility/incompatibility with existing mineral or other EAL oils

...have become evident with some types of EALs, particularly with some types of stern tube lubricants. PANOLIN stern tube lubricant does not suffer from these issues. All these problems cause more frequent: system/lubricant monitoring, maintenance, lubricant top-up, system draining and re-filling, transport/disposal of used oil and costs of replacement parts. These are the obvious direct costs of using inferior performing/life oils – not to mention the hidden costs of the paperwork to administer all these monitoring/inspection/testing/re-ordering/logistics operations, and lost revenue due to equipment downtime/failure – and the embarrassment of late deliveries of consignments.

Fully Saturated Synthetic Ester technology, is leading the way in reliable, high performance and long-life marine lubricants for Stern Tube /CPP and Thruster propulsion, Rudder and Bow thruster steering and vessel stability systems such as Fin Stabilizers and Ballast Control...... with the benefits of being environmentally considerate and reducing a vessel's Carbon Footprint. Documented monitoring of 'real-life' use of PANOLIN Saturated Synthetic Esters shows that in all areas of fluids/lubricants use: stern tube, hydraulics and gearboxes, the robust chemistry of saturated ester technology can enable up to 10 times the operational life of mineral oils, when combined with a Best Management Practice for lubricants (just looking after the oil and having regular sample checks!)

It is the lubricant manufacturer's job to tell you all about the key performance indicators of their lubricant(s) – consult them and ask them what specific EAL base oil technology they use! If they say "We use ester technology", ask if it is natural, unsaturated, or a blend of saturated and unsaturated ester, or if it is the 'real thing' - a fully 100% saturated synthetic ester. PANOLIN, Switzerland, makes fully Saturated Synthetic Ester (HEES) lubricants, all US EPA VGP regulations and Polar Code recommendations compliant, for all vessel application lubrication requirements - with availability around the world.

Select your lubricant wisely! – and look after it!