Here is the recently released CIMAC Guideline on “The causes of scuffing and measures to prevent it in two-stroke engines” is the work of CIMAC Working Group 8, also known as “Marine Lubricants.” The document provides advice on scuffing causes and prevention in two-stroke engines.
2023-03-02_CIMAC_Guideline_Scuffing_FINAL.pdf (2.3 MB)
But first of all what is scuffing?
Scuffing is the severe adhesive wear between surfaces lubricated by a broken or failed lubricant film.
Examples of scuffed surfaces:
Possible causes of scuffing:
Do you have any experience with this issue?
Thank you for sharing the CIMAC Guideline on scuffing in two-stroke engines.
Based on my experience, when scuffing occurs in two-stroke engines, there are usually rapid and frequent temperature fluctuations on the liner walls, and overall temperature levels increase. Detecting these patterns with conventional temperature alerts can be challenging since the alarm values need to be continuously adjusted, and fluctuations not related to scuffing can cause false alarms.
It’s important to be aware of scuffing, which can be caused by the use of Very Low Sulphur Fuels (VLSFOs) in older engines. These fuels have higher combustion engine density properties, which can result in more stress on engine components and lead to the formation of red deposits. Improper fuel handling during the transition to VLSFOs and flushing waste material through engines can also contribute to scuffing. However, the industry has now adapted to the use of VLSFOs, and following a recommended engine maintenance program can help prevent liner wear and damage.
Here is a relevant paper by Chevron
Scuffing And Red Deposits After Fuel Transition.pdf (1.2 MB)
Scuffing is a rapidly accelerating wear mechanism caused by breakdown of the oil film. It can lead to catastrophic damage of cylinder liners and piston rings within just a few days of operation. The reasons behind oil film breakdown are numerous and complex, and analyses of scuffing incidents have shown that they usually involve a combination of factors. Therefore, it would be incorrect to attribute scuffing solely to the use Very Low Sulfur Fuel Oil (VLSFO).
The field of cylinder lubrication in two-stroke marine diesel engines is complex due to the cyclic change between boundary and hydrodynamic lubrication caused by the movement of the piston. For instance, at top dead center where the piston velocity is zero, boundary lubrication occurs, whereas hydrodynamic lubrication occurs when the piston is moving inside the liner.
The CIMAC paper approaches this matter in a cautious and well-documented manner.