2 Characteristics of A New Marine Engine Main Bearings

 The rotational force of a ship's propeller is determined by the force generated by the ship's engine that rotates the crankshaft. The crankshaft of the main engine is supported on the connecting rod by the Main Bearings and connected with it. The main function of the Main Bearings is to transmit the load without metal-to-metal contact.

This is achieved by the selection of special materials that make up the Main Bearings, which floats when the lubricating oil is supplied to the pins of the rotating crankshaft.

Main Bearing Material Properties

  • Selecting a marine engine main bearing requires the following characteristics:
  • Corrosion resistance is required to prevent corrosion of bearing materials and related components such as steel balls and housings.
  • Frictional resistance is necessary in order to minimize energy losses between bearings.
  • Good support is required when dynamic loads come into play.
  • You need proficient driving and proficient driving skills
  • Bearings need to support the oil film so that the journal can rotate smoothly.
  • Bearing materials should avoid reacting with lubricating oils.
  • The bearing must be able to embed properly so that small particles can be embedded in the bearing surface without damaging the journal pins.
  • Bearing material should have good compressive strength and tensile strength
  • It needs to be heat resistant to prevent damage in high temperatures.

A Marine Engine Main Bearings

General Defects of Bearings

  • Corrosion: If the oil in which the bearing is configured is acidic, it may cause corrosion. The seat surface is discolored and rough due to corrosion
  • Abrasion: If the oil is not properly filtered and treated, and contains general particulates, this can cause fine scratches on the bearing surfaces for engines burning heavy fuel oil.
  • Erosion: If the oil supply pressure is not appropriate, or if the journal is moving abnormally fast, the bearing cap may come off. These phenomena are more prevalent in medium-speed engines.
  • Fatigue: Excessive engine load on the bearing may cause the bearing bushing to disintegrate. The cracked pavement on the seat.
  • Wiping: The process of removing the overlay due to high temperatures. If the bearing is new, it needs to be wiped to remove the first layer. This helps to realign the bearing into a journal. However, excessive metal wiping will increase clearance and may affect bearing performance.
  • Spark Erosion: When the propeller is stationary, the stern tube, driveshaft, and bearing are in contact with each other. Likewise, the bearings and journals of the mainframe are in contact with each other, maintaining the electrical continuity. When the boat is in motion, the shaft is partially electrically insulated due to the rotation of the propeller and lubricating oil film. In addition, tail shafts that use non-metallic bearings as insulators may also occur.
  • Crankshaft Misalignment: When the crankshaft of a marine engine is fully assembled to the engine, it is a large component. First, align the entire crankshaft in a straight line (connections from the center of the crankshaft form a straight line) before placing the entire crankshaft on the main bearing. However, over time, due to various factors, the straight line may deviate and the main bearing may be damaged.

A Marine Engine Main Bearings

Therefore, the increased clearance between the bearing and the pins may be caused by the above factors and the following factors.

  • If the bearing works longer than the operating temperature
  • When there are large and continuous changes in engine speed, such as engine Overspeed
  • The case where the film thickness of the lubricating oil is reduced due to the change in the flow of the oil
  • If the viscosity of the lubricant changes,
  • When the lubricating oil temperature is high
  • The load resistance of the oil used is different from the recommended value.
  • Changes in temperature around the engine.

Want to share your tips and advice? Got questions? Visit the Landtop to ask questions, get answers, meet people, and share your tips!

In our Landtopmall, there are many high-quality main bearings, and there are various models for you to choose from. Among them, they are suitable for Kubota V2607 engine and V2607-t are for sale. If you have a demand, welcome to our Landtopmall to have a look.

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