Other lubricants and greases used on a ship
A ship has many different machinery systems besides the main engines and generator sets and all of these will require lubrication either using oils or greases. Many machines will have unique requirements and in such cases there are normally special formulations provided by the leading lubricant manufacturers. Gearboxes, turbochargers and compressors are good examples of this.
The list of manufacturers producing specialist lubricants is the longest of all because it includes all of the major players as well as some specialists such as Kluber Lubrication who tend to leave the mainstream lubes alone and concentrate on more niche products.
Closely allied to lubricants are the hydraulic fluids that can be found in cranes, winches, pumps and many other items of machinery and equipment such as watertight doors, cargo hatches and ro-ro ramps and lifts; even chains and wire ropes require lubrication. Most lubricants and fluids are used in closed applications but in deck machinery and in equipment such as controllable pitch propellers, stern tube seals thrusters and steering gear there is a high risk that they can leak into the waters the ship is operating in.
For regulatory purposes such as MARPOL or under local law, any escape into the environment of these products will be considered as acts of pollution and the operator is therefore at risk of prosecution. Leaks from deck machinery should be dealt with as soon as is practically possible and especially before arrival into port where rain could cause the spill to be washed overboard.
If the leak is of hydraulic fluid and did not result from an accidental spill there is a high possibility that the system is compromised. The risk of pollution is therefore not the only problem as the system itself may fail resulting in an inoperable winch or a hatch cover that cannot be opened or closed. The pollution risk from deck machinery and stern tube seals can be reduced by making use of biodegradable lubricants. Such products are generally made from vegetable or animal sourced material.
Biodegradable products are still in their infancy as far as marine lubricants go as it was only in 2002 that Vickers Oils became the first company to make biodegradable lubricants commercially available to the global marine market. In addition to improving environmental credentials, the opportunity to reduce operating costs is just as important to the marine industry as any other business. The use of biodegradable lubricants is one way that vessel operators can achieve cost saving benefits if their makers’ claims as to performance are true.
It may be thought that the most demanding application for lubricants is in the engine where high temperatures will be experienced but exterior uses are probably even more so. Winches and cranes as well as underwater equipment will experience very wide operational temperature ranges. For some ships, there will be times when such equipment is exposed to sub-zero temperatures and others when it could be exposed to hot tropical sun. Wind, rain frost and snow will also affect performance. It is however important for the ship that the equipment operates at all these extremes so the choice of appropriate products is something thought must be given to.
In many areas use of synthetic or biodegradable lubricants is a voluntary choice for operators but in the US the requirements of the Vessel General Permit make lubricant choice more restricted. Under the new VGP introduced in 2013 the list of permitted substances and the quantity each ship above 300gt will be allowed to discharge was reduced – quite dramatically in some cases.
Since December 2013 lubricants in any equipment or system that has an oil-to-sea interface (essentially all propulsion systems and also deck machinery where run-off over the ship’s side could occur) must be environmentally acceptable lubricants (EALs) unless doing so would be ‘technically unfeasible’. EALs are defined as biodegradable, which rules out all mineral-based lubricants and even some synthetic alternatives.
The exact definition of an EAL is contained in the US Environment Protection Agency’s document, EPA 800-R-11-002 November 2011. Operators have to apply for a VGP before a vessel enters US waters and to do so they need to identify all oil-to-sea interfaces and lubricants involved.
Among the most obvious systems are the stern tube, rudder bearings, CP propellers, thrusters, and fin stabilisers. In addition, winches, cranes, hatch covers, and even crane wires and the like must be considered. The ship will be required to document all lubricants and any reason why the use of an EAL would be technically unfeasible.
Most major oil companies and some specialist suppliers have formulated compliant products but these products are not necessarily compatible with some makes of seals, especially conventional rubber seals. This is a known problem and most combinations of lubricants and seals have been tested for compatibility over normal dry docking cycles of two to three years.
In selecting an EAL, operators must therefore seek advice from the seal manufacturer and great care must be exercised if the vessel makes use of enhanced or extended dry docking strategies. Inspections with regard to EALs would involve visual sheen tests and inspections of deck runoff. The ‘unless technically infeasible’ proviso can allow some temporary relief if the ship has seals that are incompatible with any EALs, in which case it can continue to use mineral oil until the next planned docking, when the seals are to be replaced, or if the equipment manufacturer has no recommended seal-EAL combination for its product. Some pre- lubricated wire ropes are also included in the exemption.
If the use of an EAL in an oil-to-sea interface is claimed to be technically infeasible, the ship must carry documentation to that effect. Supporting documentation written by the manufacturer or owner must not be more than one year old and must confirm the factual situation.
Quality and quantity
Choosing the right grease for each application is important and although there are multi-purpose greases, these are unsuitable for very high-pressure use and other specialist applications. Reference should always be made to the equipment manuals and to the grease specification and technical data sheets.
Even when the correct grease is chosen, under or over lubrication can create problems. Both can cause component failure or heat build-up but for different reasons. Under-greasing obviously increases friction but too much grease in a bearing cavity for example, will cause the rotating bearing elements to begin churning the grease, pushing it out of the way, resulting in energy loss and rising temperatures. This leads to rapid oxidation of the grease as well as an accelerated rate of oil bleed. The heat that has been generated over time along with the oil bleed eventually will cook the grease thickener into a hard, crusty build-up that can impair proper lubrication and even block new grease from reaching the core of the bearing. This can result in accelerated wear of the rolling elements and then component failure. Over greasing is also wasteful of expensive products.
Using calibrated grease guns will help in preventing under or over greasing and there are other tools available as well. One of these is SDT International’s LUBExpert, a hand-held device that combines SDT ultrasound sensing, a database of greasing locations and types and a grease gun attachment.
The database details the type of grease to use in specified locations and with only a few machine parameters, LUBExpert monitors each stroke of grease and its effect on bearing friction and temperature both before and after, with bearing conditions reported with a “GOOD”, “BAD”, or “SUSPECT” status report.