Marine lubricants are oil formations that are used in various types of machinery located on large ships. Due to the sheer size of the ships and the high amount of fuel burned, there are many difficulties presented with developing a truly marine-grade lubricant.
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Applications of Marine Lubricants
Typically, there are three main ways marine lubricants are used: with propulsion engines, auxiliary engines and power generation, all of which require the use of one of two types of engines: crosshead and trunk piston. Crosshead engines are large reciprocating diesel engines that can be either internal combustion or steam but are modernly more likely to be internal combustion. Crosshead engines are typically two-cycle and operate at slower speeds than trunk piston engines. Trunk piston engines are internal combustion diesel engines that operate on distillate fuels and are typically four-cycle and offer medium speeds. Unlike crosshead engines, which have a separate cylinder and crankcase sump, trunk piston engines have a common sump for both parts. Marine lubricants can be used in variable pitch propellers, geared transmissions, turbochargers, deck machinery, and oil-lubricated stern tubes. A fairly new technology increasing momentum is biodegradable marine lubricants, which a few companies have developed in response to increasing demand because of the environmental benefits these lubricants can offer.
Marine Lubricant Creation
Marine lubricants most often utilize paraffinic oil base stock. Paraffinic oils contain paraffin wax, which is a type of alkane hydrocarbon. Paraffinic oils' advantages over other oils, such as naphthenic oils, include high oxidation resistance, low volatility and excellent stability, and high pour points and flashpoints. Marine lubricants are often monograde oils that are typically SAE 30/40/50 viscosity grades. Monograde oils can be used in marine applications due to the stable operating conditions of the ship’s engine room. As a result of the many difficulties of maintaining good lubrication of marine equipment, most lubricants utilize additives that provide additional features such as increased lubricity and corrosion-resistance that allow them to be used in these applications. The most common additive types that are used for marine lubricants include corrosion inhibitors, pour-point depressants, antioxidants, anti-foam compounds, detergents/dispersants, and anti-wear/friction. These additional characteristics that make certain marine lubricants more desirable are synthetically developed.