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Gas Bearings
Gas bearings are sliding bearings that use a gas as a lubricant to create a thin, load-bearing film between two surfaces, preventing them from making contact to reduce friction, wear and particulate generation. Gas bearings that use air are called air bearings. Other lubricant gases include nitrogen, argon, carbon dioxide, hydrogen and helium.
Gas bearings eliminate the need for traditional oil-based lubrication, enabling cleaner, more efficient, more reliable air compressors.
What Are the Different Types of Gas Bearings?
Discover the main types of gas bearings:
- Aerostatic bearings: These bearings rely on external pressurization. A compressor injects a continuous flow of gas into the clearance between the bearing surfaces, allowing them to support a load even when the parts are not moving.
- Aerodynamic bearings: In this design, the relative motion between the static and moving components generates the gas pressure. As the speed of the rotating part increases, it pulls gas into a wedge-shaped gap, generating the pressure needed to lift and support the load.
FAQs
Besides the lubricant medium, gas and oil bearings differ in various ways:
- Contamination risk: Gas bearings do not pose an oil carryover risk like their oil counterparts.
- Friction and wear: Gas bearings are virtually frictionless and experience zero wear during operation. In contrast, oil bearings experience greater friction, leading to wear over time.
- Load capacity: Oil bearings possess a higher load capacity than gas bearings.
- Maintenance: Gas bearings need minimal maintenance, while oil bearings require frequent oil changes and filter replacements.
- Failure modes: Oil bearings fail due to oil contamination and loss of lubrication, while gas bearings fail due to contamination and overloading.
- Operating speed: Gas bearings operate at high speeds, while oil properties and heat from friction limit the speed of oil bearings.
An air compressor supplies compressed gas to aerostatic bearings, allowing them to function in various machines such as precision spindles and coordinate measuring machines (CMMs). Air bearings can also be integrated into oil-free, high-speed air compressors, particularly centrifugal ones, to increase efficiency.
Critical industrial applications must regularly monitor gas bearings to ensure reliability. This process entails checking:
- Vibration: Periodic or continuous vibration inspection allows you to identify early bearing damage.
- Temperature: Regular temperature monitoring enables you to detect a rise, which signals contamination or an unstable gas film.
- Components: Periodic component inspection helps you identify and fix air leaks, corrosion, contamination buildup and supply line damage.
- Gas supply in aerostatic systems: Assessing the gas supply ensures consistent pressure and verifies gas purity for reliable performance.
The choice between these two gas bearing types depends on the application.
Choose an aerostatic bearing when:
- The bearing must support a load even at zero speed.
- High stiffness and positional accuracy matter.
- You possess an external source of clean, compressed gas.
- The application involves regular starts and stops.
Select an aerodynamic bearing when:
- The system operates at a consistent, high speed.
- An external gas supply is impractical or undesirable.
- The design prioritizes a simple, self-contained operation.
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