Marine Lubricants Properties
All lubricants help to reduce friction and heat, prevent damage, and prolong component life. However, not all oils are capable of operating in potentially caustic environments, such as those found in coastal areas or on the sea. Marine lubricants have very important properties that make them ideally suited for use in boat motors, aboard ship, and in other marine-related areas. In this post, we will explore some of the most important of those properties.
Why is Marine Engine Lubrication different?
Before we touch on the particular properties of marine lubricants, we need to address the question of why marine engine lubrication differs from lubricating engines used in non-marine applications. There are actually several different reasons, including the following:
- Size – Often, marine engines are much larger than their land-bound relatives, particularly on larger ships.
- High Efficiencies – Marine engines must be very efficient in order to produce ample motive power, which requires high firing pressures.
- Fuel – Most marine engines use diesel fuel, but not high-quality diesel. High sulfur content and carbon residue create major problems.
Now that we’ve looked at some of the differences between marine and land-based engines, we can turn our attention to marine lubricant properties.
One of the most important considerations with marine lubricants is the alkalinity. This is particularly the case with four-stroke and trunk piston engines, where the oil lubricates the pistons and the liner, coming in contact with combustible fuel. Alkalinity helps to control acidic corrosion in these situations. Two-stroke engines require a different grade of marine lubricant.
Resistance to Oxidation
Because marine lubricant is always exposed to oxygen when in the engine, it must be able to resist oxidation well. Add to this the fact that most engines do not have the oil changed regularly, but rather, it is topped up as necessary until it is sufficiently contaminated to warrant the cost and time investment of a full change. High temperature operation increases the oxidation rate of marine lubricants. A quality lube oil will have additives to help prevent oxidation and oxidative damage.
Detergent oils help to scour the internal components of the engine, removing buildup and reducing wear and tear.
Combined with detergent capabilities, marine lubricants must also be able to disperse contaminants properly. In an ideal situation, lube oil should be able to keep impurities and contaminants suspended at the surface, rather than allowing them to mix with the oil itself.
All oil is combustible, but high volatility lubricants are very dangerous, particularly aboard a ship. Marine lubricants must have low volatility to increase the oil’s flash point to a sufficiently high temperature that it does not pose a threat of crankcase explosion.
These are some of the more important properties of marine lubricants. However, there are many others. For instance, marine lube oil should have a good ability to adhere to surfaces (oiliness or “stickability”). Viscosity, thermal conductivity, demulsification, and load carrying capacity are also all important.