Water Lubricated Bearings (Rubber Bearings)
Type approval received for each ship classification
Water Lubricated Bearings (Rubber Bearings)
Bearings for propeller shaft systems for ships can be broadly classified into water lubrication and oil lubrication. In the past, lignum vitae, which is a natural wood containing resin, had been used for water lubricated bearings. However, the depletion of raw wood in the production areas (Central and South America) has made it difficult to obtain materials with good quality, resulting in the frequent occurrence of irregular wear and swelling. In recent years, rubber bearings with stable quality are most commonly used instead of lignum vitae. At our company, we began developing rubber bearings in the early 1970s. We provide excellent rubber bearings that are strong and stable in the long-term by using rubber that has great sliding properties and wear resistance, as well as a special method for adhesion with the metal shell. At present, we have numerous achievements.
Characteristics of Water Lubricated Bearings (Rubber Bearings)
01. Low Power Loss
In general, wet rubber and metals have properties of sliding very well. At our company, we pay attention to these characteristics and implement designs with rubber that have a low coefficient of friction.
| Friction Comparison | Coefficient of Friction |
|---|---|
| Rubber and Metal (Wet) | 0.04 |
| Rubber and Metal (Dry) | 0.5 |
| Cast Iron and Cast Iron (Some Oil) | 0.15 |
| Cast Iron and Bronze (Dry) | 0.22 |
| Cast Iron and Oak (Little Oil) | 0.19 |
| Wrought Iron and Oak (Little Oil) | 0.08 |
| Rolling Bearings | 0.014 |
| Ball Bearings | 0.001 |
02. Low Wear
Wear resistance is better compared to lignum vitae. There is an example of rubber bearings being used for over 4 years in a situation where lignum vitae had to be replaced every several months.
03. No Damage to the Shaft and Sleeve
Even if sand or pebbles fall between the shaft and the rubber bearings, the lubricating water expels the debris along the ridge as the shaft rotates. At out company, we implement designs with rubber that take advantage of these properties.
Structure
Full Mold Type
This is the type that is generally widely used. Rubber is vulcanized to adhere to the inside of the metal shell, and there are a certain number of ridges carved into the rubber so that lubricating water can be passed through for usage. Full mold types can be broken into the straight type (LB-type) and the type with a flange (LBF-type).
Segmental Type
This type is mainly used if the shaft has a large diameter and is formed of a strip in which a metal plate and rubber are vulcanized for adhesion and a metal shell (housing).
The key characteristic of this type is that maintenance is easy and inexpensive because only the worn strip needs to be replaced for repairs.
