Cylinder Liners in Marine Engines: In-depth Guide

Blogpost

June 21, 2024
11:11 pm

All marine machinery and parts wear out during their lifecycle. Like other engine parts, the cylinder liner is vulnerable to deterioration due to severe stress, pressure, heat, friction, etc. No matter the engine brand or quality of OEM parts, the cylinder liners are always at risk of failure. Operating the engine with a mutilated cylinder liner can be dangerous and damage the expensive components on the vessel.

In this blog post, we are offering a guide to marine cylinder liners, their functions, and failure. Learn why it is vital to replace cylinder liners for proper engine health management.

What is a Cylinder Liner in Marine Engines?

A marine cylinder liner is a vital component of the engine on a watercraft. It is a protective and replaceable part mounted in the marine engine cylinder. The affordable and easy-to-avail item acts as a shield to protect the cylinder body against friction, abrasion, and damage.

The composition of cylinder liners includes sturdy metal alloys such as cast ductile iron, cast steel, nickel-chrome, etc. These metal compounds feature supreme heat dissipation, lubricating smooth surface texture, and wear-resistant properties. Among others, cast iron offers vibration damping when the engine is operating.

The terms cylinder liners and cylinder sleeves are often used interchangeably. However, there are a few differences between these two items.

Causes of Stress and Failure in Cylinder Liners

The cylinder walls are susceptible to rapid wear and tear due to enormous pressure and piston movement in the chamber. During each combustion cycle, the piston rings and skirt produce reciprocating motion to transmit combustion forces.

Herein is an overview of factors causing cylinder liner wearing and damage:

Frictional Sliding Surfaces

During engine operation, the piston rings rub against the marine cylinder liner, causing friction. Eventually, the phenomenon leads to wearing in the piston and the cylinder liner. Without the protective casing, this can damage the expensive cylinder walls.

The possible causes of frictional wearing include:

High-speed piston ring sliding on the liner surface
Extreme temperature and pressure during combustion
Poor lubrication
Lack of maintenance

Abrasive Wearing

The extreme uppermost and lowermost parts of the cylinder are called the top dead centre (TDC) and bottom dead centre (BDC). Abrasion wearing rate is highest at the TDC and BDC. Abrasion wear and tear happens due to one or more factors. Repeated combustion cycles produce hard particles in the cylinder. Besides these particles, combustion ashes, dense catalytic fines in the fuel oil, and metal swarf can result in abrasive wearing in the marine cylinder liners. The high amount of wear particles in the cylinder chamber also contributes to further abrasion.

Lubricant Starving and Scuffing

Low lube oil level in the cylinder causes welding between the liner and the piston rings. The welding breaks due to high-speed piston movement. This causes the formation of abrasive material. Moreover, lubricant starving raises heat and local welding in the space. The cylinder liner loses its properties in such an environment and scuffs, allowing the cylinder oil to adhere to the surface.

Corrosive Wearing

Corrosion also contributes to cylinder liner wearing. However, corrosion occurs in the marine cylinder liners due to various reasons:

The high percentage of sulphur in heavy fuel oils reacts with moisture in the chamber to form sulphuric acid during combustion. It is essential to treat these acids with alkaline cylinder oil. If the acids are not neutralised, it can trigger corrosion in the lower part of the cylinder liner near the quills.
Low-temperature combustion is gaining popularity among vessel operators to prevent overheating. However, this can also create a mismatch between engine load and the cylinder oil quantity. Therefore, the low temperature in the cylinder can cause corrosion in the cylinder liner.