Types and Types of Thrust Bearings

Thrust bearings allow axial loads to be applied in one direction. They are used in many applications and have a wide range of load capacity. The most common causes of failure are contamination, misalignment and overloading.

The study of rotor-bearing systems uses a small perturbation method to solve Reynolds equation and estimate the damping and stiffness coefficients of a thrust bearing. The results show that changing the misalignment angle and film thickness have a clear impact on the dynamic coefficients.

Material

Bearings are essential components of a variety of machines. They support axial loads and reduce friction. Depending on your specific application, you may need to consider different types of thrust bearings.

Cylindrical roller thrust bearings feature cylindrical rollers that are arranged around the shaft in a perpendicular fashion. These self-aligning bearings can support heavy axial loads and tolerate moderate radial loads. They're also ABEC-rated, which offers a guarantee of precision and accuracy.

Tapered roller thrust bearings have a spherical raceway surface on the housing washer and are self-aligning. They can withstand heavy axial loads and offer high rigidity and axial load capacity. These bearings can also tolerate some radial loads, which is useful in applications with directional misalignments.

A composite thrust bearing features a carbon steel shell, an intermediate layer of sintered bronze, and a PTFE-based sliding lining. This bearing is capable of handling axial loads and speeds up to the maximum ratings. However, it's best to use these bearings at significantly less than the maximum load and speed ratings to ensure reasonable life calculations.

Design

Thrust bearings are rotary components that support axial loads and reduce friction. They are available in a variety of sizes and types to fit your needs. There are two main types of thrust bearings: ball and needle roller. Both offer excellent load capacity and high speed performance, but there are some differences between them.

The ball thrust series supports a single-directional axial load, and the needle roller type can accommodate a double-directional axial load. Both types require a cage to maintain equal roller spacing and loading.

Hydrodynamic thrust bearings float on a hydraulic oil or air cushion and use quality seals to prevent leakage. They have an internal recess that routs the lubricant to the runner/pads, which remains afloat in the fluid layer. A pump is used to continually generate the air or lubricant pressure that supports the pads. This eliminates the inertia and torque of a rotating shaft but requires a continuous power source.

Load Capacity

A bearing can only support so much load before it starts to break down. SMB’s experts can help you determine the maximum static axial load (thrust load) that your bearings can sustain without excessive, permanent deformation.

The type of thrust bearing you choose will also affect the load capacity. Cylindrical roller thrust bearings are a good choice for large load capacities because they can tolerate differing radial speeds and have the lowest sectional height.

Flat race thrust bearings are more economical but cannot tolerate misalignment or rotational eccentricity. Grooved race thrust bearings are a better option for pure thrust loading. They have a ball retainer held between grooved washers that can handle directional misalignment.

Installation

When mounting thrust bearings, it's important that the shaft OD and housing allocation match to ensure an internal fit. An oversized shaft can cause damage to the rolling elements, lubrication film and metal expansion due to temperature changes. On the other hand, a shaft that's too small can result in excessive friction, loss of load capacity and premature failure of the bearing.

Some types of thrust bearings support axial loads while also reducing the amount of friction, which is ideal for applications like generators and water turbines. They're often manufactured using corrosion-resistant materials that make them suitable for demanding mining and construction environments as well.

Thrust ball bearings consist of a complement of needle rollers held in place by a cage that sits between flat or grooved washers. They can withstand axial loads in one direction but cannot accommodate radial loading, so they're susceptible to misalignment. The balls and cage also generate heat during operation, so they must be cooled to prevent overheating.