Liquidfilm thrust bearing is a type of bearing that utilizes a lubricating fluid to form load-bearing film to support axial loads. It is commonly used in steam turbines, compressor, pump, motor, gearbox, high-speed rotating machinery and so on. Unlike rolling element thrust bearings, rolling element thrust bearings are mainly operated by lubricating film or other fluid film to reduce friction and wear.
Fluid-film thrust bearings can be divided into various types according to the film formation method, bearing structure and operating principle. Understanding the structural characteristics and application scenarios of these different types of products can help equipment manufacturers, engineers and procurement personnel to select the right products based on specific operating conditions.
1.Fixed-Pad Fluid-Film thrust bearings
Fixed-gasket liquidfilm thrust bearing is a common structural configuration consisting of multiple thrust pads. Each gasket is usually mounted in a thrust bearing housing, creating a lubrication gap between the gasket and the rotating member.
During the operation of the equipment, the lubricant enters the working area of the bearing and rotates to produce a liquid film supporting the axial load.
This kind of design is characterized by maturity, stable bearing capacity and is suitable for all kinds of industrial rotary machinery. Specific performance depends on pad dimensions, material, lubrication conditions and speed.
2.Tilting-Pad Fluid-Film thrust bearing
The tilting-pad thrust bearing is a kind of liquidfilm thrust bearing commonly used in industrial equipment. Unlike fixed gaskets, tilted gaskets are designed to allow each thrust pads to rotate slightly within a certain range, automatically adjusting the angle of work between the gasket and the thrust collar.
During operation, a dynamic oil film is formed between the gasket and the thrust sleeve. The tilting-pad structure allows the shape of the oil film to be adjusted according to operating conditions so that the load distribution on the pad is more balanced.
Therefore, this kind of liquidfilm thrust bearing is often used in steam turbines, compressor, large water pump and other high speed heavy load rotating equipment with high operating stability.
3.Plane Flow Film Push Bearing
Planar liquidfilm thrust bearings usually have relatively flat working surfaces and a fluid film is formed between moving surfaces through lubricating media.
The design is simple and effective under certain low or mediumload conditions. In the actual design process, it is necessary to determine whether a stable fluid film can be established according to bearing dimensions, speed, load and lubricating oil parameters.
For high-speed machinery, additional factors such as temperature rise, oil film stability and dynamic performance must also be considered.
4. Static thrust bearings
The main difference between hydrostatic thrust bearings and conventional hydrodynamic fluid-film thrust bearings bearing lies the formation of oil film.
Hydrostatic bearings utilizes an external pumping system to provide pressurized lubricant to the bearing's working surface, thus forming a stable load-bearing oil film. Therefore, even when the equipment is operating at low speed or in the startup phase, a certain bearing capacity can be established through external pressure.
Hydrostatic thrust bearings generally require auxiliary components such as oil supply systems, flow restrictors and pressure control devices. Although the structure of the system is complex, the application of these bearings in the areas of low speed and heavy load, precision motion and the requirement for positioning accuracy is valuable.
5. Hydrodynamic thrust bearings
Hydrodynamic thrust bearings mainly depends on the relative motion between moving components and lubricating oil to produce supercharged oil film.
When the equipment reaches a certain speed, lubricant enters the bearing clearance, and under the influence of certain geometric features, a load-bearing fluid film is formed.
This kind of design does not necessarily require complex external high pressure oil supply system, so it is widely used in high speed rotary machinery. However, its bearing capacity and lubrication state are influenced by speed, load, lubricant viscosity, bearing clearance and temperature.
6. Fluid-film hybrid thrust bearings
Some industrial bearings are designed using a combination of hydrodynamic and hydrostatic principles, with different oil film formation mechanisms depending on the stage of operation.
When starting or operating at low speed, an oil film can be built through an external oil supply system; once the equipment has transitioned to normal high speed operation, the load is primarily supported by the hydrodynamic oil film generated through movement. This design improves lubrication conditions the bearing's startup phase and reduces the possibility of direct contact with working surface at low speed. This configuration is particularly valuable for equipment with significant variations in operating conditions.
7. Gas film thrust bearings
In addition to lubricating oil, some liquidfilm thrust bearings also use air or other gases as lubricating agents, commonly known as gas film thrust bearings.
Because the viscosity of gas is far lower than that of lubricating oil, gas film bearing has the advantages of lower frictional resistance, operating speeds and no need for traditional oil lubrication.
Membrane thrust bearings are commonly found in high-speed motors, precision machinery, turbochargers and equipment that requires a clean work environment. However, their bearing capacity is influenced by bearing dimensions, pressure, clearance and speed; therefore, design specifications must be suitable for specific operating conditions.
How to choose suitable liquidfilm thrust bearing?
Different types of liquidfilm thrust bearings have distinct operating characteristics and cannot be selected solely on the basis of bearing dimensions.
First, determine the equipment's axial load of the equipment, including normal operating load and any potential peak loads. Secondly, determine the rotational speed as this directly affects the formation and stability of the fluid membrane.
In addition, the lubrication method, operating temperature, lubricant viscosity, bearing material, installation space, frequency of equipment start andstop cycle, etc..
If the equipment requires to be started and stopped frequently, priority should be given to lubrication conditions during the low speed phase; for equipment involving high speed continuous operation, priority should be given to oil film stability, temperature rise and reliability of the lubrication system.
Frequently Asked Questions
What is the main lubricating medium of liquidfilm thrust bearing?
Common lubricating media include gaseous media such as lubricating oil, grease and air. The specific choice depends on the bearing structure and the conditions of use of the equipment.
Is tiltpad thrust bearing suitable for high speed equipment?
The tilting-pad structure improves the condition of oil film by making minor adjustments to the gasket to make it suitable for certain high-speed rotating equipment; however, its specific applicability depends on bearing design and operating conditions.
What is the difference between static and dynamic thrust bearings?
Hydrostatic thrust bearings mainly depends on external pressure to form a bearing film, while hydrodynamic thrust bearings mainly depends on rotating motion to form a a pressurized oil film. The two types are different in terms of fuel supply systems, startup characteristics and application scenarios.
What types of equipment are liquidfilm thrust bearings suitable for?
Common applications include high-speed rotary machinery such as steam turbines, compressors, pumps, electric motors, gearboxes and turbochargers.
Abstracts
According to the forming mechanism and structural characteristics of lubricating film, liquidfilm thrust bearing can be divided into fixed type, inclined type, hydrodynamic type, static type, mixed type and gas film thrust bearing.
Different types of liquidfilm thrust bearing have different bearing capacity, speed range, startup performance, lubrication method and operating environment. When selecting bearings, the axial load, speed, temperature, lubrication conditions, operating mode and equipment structure should be taken into account, rather than relying on bearing dimensions solely.
Industrial equipment such as steam turbines, compressors, pumps and high-speed motors must be professionally selected according to specific operating parameters to ensure that bearings can establish a stable lubrication film to meet the requirements of long-term operation.