Shipbuilding Heavy Industry

Marine lubricating oil mainly includes marine cylinder oil, marine system oil, marine medium speed engine oil, and other small product oils. Cylinder oil is mainly used for lubrication between the piston and cylinder liner of large cross head low speed diesel engines. Marine system oil is mainly used for lubrication of the crankcase of large cross head low speed diesel engines. Marine medium speed oil is used for lubrication of marine medium speed cylindrical piston diesel engines. These three major types of marine oil account for 9O% to 95% of the total amount of marine lubricating oil. Others are minor oils, including turbine oil, hydraulic oil, refrigeration oil, gear oil, compressor oil, guide rail oil, tailpipe oil, etc., accounting for 5%~10%

Main performance of cylinder oil

Low speed cross head engines for ships usually use high sulfur heavy fuel. This type of fuel produces a large amount of acidic substances during combustion, which can easily cause corrosion and wear on the surface of cylinder liners and pistons. Therefore, there are the following requirements for the performance of cylinder oil:

① Good cleansing and dispersibility. In order to keep the piston ring groove and cylinder liner air port clean for a long time, reduce carbon deposition, paint film and other deposits, and the ash formed after combustion should belong to non wearing substances.

② Good load-bearing characteristics and boundary lubrication.

③ Good acid neutralization ability. Having sufficient "effective base value" to neutralize the acidic substances produced during the combustion of sulfur-containing fuels.

④ Fast diffusion performance. Cylinder oil is required to have appropriate viscosity and good diffusion performance at high temperatures, forming a complete adsorption oil film on the entire working surface.

⑤ Good storage stability. It can be stored for a long time or mixed with other grades of cylinder oil without precipitation.

The relationship between fuel oil and marine lubricating oil

Before switching to fuel oil, ships generally used No. 20 heavy diesel fuel, and the quality difference between the two fuel oils was very significant. The carbon residue and sulfur content of thousand second fuel oil are high, and the acidic substances generated after combustion are easy to cause corrosion and wear of cylinder liner, piston and crankcase. Oil sludge, carbon deposit and ash can accelerate the abrasive wear of moving parts such as piston ring, and metal deposits also promote the high-temperature corrosion of the engine. Therefore, it is necessary to match lubricating oil to solve the problems of cleanliness and wear resistance, and to avoid increased spare parts consumption and unsafe navigation caused by blind switching of fuel oil. There is data indicating that the sulfur content of the fuel oil used is an important basis for selecting the total base number (TSN) of cylinder oil.

Classification of marine lubricating oils Classification of marine lubricating oils Classification of marine lubricating oils Classification of marine lubricating oils

There are many types of marine lubricants, mainly including the following categories:          

1. Cylinder oil          

Used for lubrication between the piston and cylinder gasket of a low-speed cross head engine. It belongs to two-stroke oil.         

2. System oil          

Used for low-speed crosshead crankcase lubrication.

Low speed cross head diesel engines are all two-stroke types. Due to the large size of the engine, with a piston diameter of 500-1000mm, it is equipped with a diaphragm and a piston rod packing box to effectively separate the cylinder from the crankcase. Therefore, crankcase oil (system oil) has no lubrication effect on the piston. The piston and cylinder rely entirely on a mechanical oil injector to supply cylinder oil to many injection points around the cylinder liner, which is lubricated through the diffusion of the cylinder oil itself. The crankcase is lubricated with crankcase oil (system oil).   

3. Medium speed engine oil      

Used for lubrication of medium speed cylindrical piston diesel engines. The medium speed cylindrical piston diesel engine has a piston diameter smaller than that of a cross head engine, ranging from 150-500mm. It is similar in structure to a typical diesel engine, but the engine is larger. Therefore, it relies more on the large end of the connecting rod to splash medium speed oil onto the cylinder wall to lubricate the piston cylinder and lubricate the components inside the crankcase. For high-power and large-diameter piston medium speed cylindrical piston diesel engines, There is also a mechanical oil injector as a supplement to splash lubrication. Medium speed engines often burn heavy fuel.        

Cylinder oil, system oil, and medium speed engine oil account for 90% -95% of the total amount of marine lubricants, while the rest are small grade oils, accounting for about 5% -10%.         

4. Marine small variety oil      

Including: gas turbine oil, hydraulic oil, refrigeration oil, gear oil, compressor oil, guide rail oil, tail shaft tube oil, etc

Classification of Marine Fuels              

1. Marine gas oil (crude diesel), with a sulfur content of around 0.5%.                

2. Marine diesel fuel, mixed with crude diesel and a small amount of residual oil (10% -15%), with a sulfur content of 0.5% -1.5%.              

3. Marine fuel oil, viscosity reducing tower bottom oil or vacuum tower bottom oil, with a sulfur content of more than 3%.            

4. Blended marine fuel oil, crude diesel and marine fuel oil are blended to synthesize various viscosity specifications of marine fuel oil, with a sulfur content of 1.5% -3%.

Eight Functions of Lubricating Oil

Lubrication: It refers to the addition of lubricant between two contact surfaces in relative motion, forming a lubricating film between the friction surfaces, separating the directly contacting surfaces, and turning dry friction into internal friction between lubricant molecules, achieving the goal of reducing friction, reducing wear, and extending the service life of mechanical equipment, which is called lubrication.     

The function of lubricating oil is to:     

1. Reducing friction: Adding lubricant to the friction surface can reduce the friction coefficient, thereby reducing frictional resistance and saving energy consumption.  

2. Reducing wear: Lubricants can reduce wear caused by abrasive wear, surface fatigue, adhesive wear, etc. between friction surfaces.      

3. Cooling effect: Lubricants can absorb heat, transfer heat, and dissipate heat, thereby reducing the temperature rise caused by friction. 

4. Rust prevention effect: The presence of lubricants on the friction surface can prevent rust caused by air, water droplets, water vapor, corrosive gases, liquids, dust, and oxides.     

5. Transmission function: In many cases, lubricants have the function of transmitting power, such as hydraulic transmission.     

6. Sealing effect: Lubricant forms a seal on certain exposed components, preventing water and impurities from soaking in.      

7. Shock absorption effect: When subjected to impact loads, it can absorb impact energy, such as car shock absorption.

8. Cleaning effect: impurities can be removed through the circulation of lubricating oil and filtered out through a filter.

What are the types of marine engine oils?

Answer: There are three main categories of marine engine oils (commonly referred to as marine oils): marine system oils (used for lubrication of the crankcase of+head diesel engines) marine cylinder oils (used for lubrication of+head diesel engine cylinders) marine medium speed oils (used for lubrication of cylindrical piston diesel engines)

Can different marine oils be mixed? Can different marine oils be mixed? Why?

Answer: No. Due to the different formulation systems of marine oils in the current market, the mixing of two types of oils may result in adverse consequences such as additive reactions and precipitation or mutual weakening, and even serious mechanical damage accidents. Therefore, it must be noted that without scientific testing (mixing test), two different types of marine oils (whether domestic or foreign, or foreign and foreign), even if of the same quality level, are not allowed to be mixed and used arbitrarily.

What are the principles for selecting marine oil?

Answer: There are mainly two aspects: first, viscosity level. The viscosity level of marine oil is relatively single, and the system oil and medium speed oil are divided into two levels: SAE30 and SAE40. The cylinder oil is mostly SAE50, and the navigation environment temperature is relatively high. If the engine condition is slightly poor, it is advisable to choose a slightly higher viscosity level. Conversely, lower viscosity oil can be used. Secondly, the quality level. The quality level of marine oil is distinguished by the total base number (TBN) of the oil. The selection of the alkali value of oil products is very important. The selection is mainly based on the sulfur content of the fuel used by the ship. Generally speaking, if the TBN is too small, the acid neutralization ability of the oil is insufficient, which can cause corrosion and wear; If the TBN is too large and the metal ash content is high, it can also cause wear and tear. At the same time, due to the large amount of additives added, the cost of the oil will increase