Bearings are critical to the reliable operation of rotors for industrial heavy frame and aeroderivative gas turbines. Their main purpose is to minimize friction between the rotor and stationary components, ensuring smooth and efficient operation under extreme conditions including 1500 to over 22,000 rpm rotating speeds, daily startups and shutdowns, idling to peak power output loads, while remaining resistant to wear and corrosion.
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Hydrodynamic thrust and journal bearings
Large heavy frame gas turbines typically call for hydrodynamic thrust and journal bearings. Typically, gas turbine design engineers will specify thrust bearings to handle axial loads generated by gas flow and mechanical forces (ensuring stable operation) and journal bearings for radial loads associated with rotor weight (minimizing friction and wear).
The number required will vary, depending on gas turbine design and size. Usually, though, designs call for two journal (one at the drive end and another at the non-drive end) and one double-acting thrust bearing. Hydrodynamic bearings work by generating a thin film of fluid, typically oil, to separate the rotor and the bearing surface. The hydrodynamic film is created by the rotation of the turbine rotor, which draws oil into the converging gap between the rotor and the bearing surface. Pressure developed in the lubricating film by the rotation of the rotor creates a wedge of oil that lifts the rotor off of the bearing surface, creating a gap filled with oil that carries the bearing load that reduces friction and wear. The shape of the surface is designed to optimize the hydrodynamic film and to dissipate heat. Designed for high reliability, hydrodynamic tilting pad bearings are used to support large gas turbines rotors.
Tilting Pad Bearings
These fluid film bearings consist of individual pads mounted on tilting mechanisms, enabling them to adapt to changes in rotor position and reduce the risk of damage and vibration. They are renowned for their reliability, durability, and ability to handle high loads, speeds, and temperatures. Tilting pad bearings are widely used for gas turbine electric power generation and oil & gas mechanical power installations..
Miba Tilting Pad Bearings
Miba is one of the leading suppliers of gas turbine bearings. Due to the tilting capability of their individual pads, Miba thrust bearings allow high sliding speeds (e.g. 160 m/s and above). With an appropriate oil supply, loads of >4 MPa are achievable for continuous operation. Self-equalizing systems for handling misalignments between the thrust collar and the bearing are also available.
As a direct result of these operational features, Miba tilting pad bearings reduce overloads and significantly improve thrust force distribution. Another common feature is direct lubrication that reduces power loss and improves oil flow – both of which lead to lower pad temperatures. Direct lubrication can be combined with a pad oil distribution feature at the pad inlet.
Bearing maintenance and inspection guide: download here.
For an overview of MIBA bearings, please see following video! 
Related article: Preventing Tilting Pad Fluttering in gas turbine bearings
About Miba: Miba Industrial Bearings designs, repairs and manufactures hydrodynamic bearings and labyrinth seals for use in high-performing rotating equipment, such as turbines, compressors or generators. Miba started manufacturing bearings in 1949 and brings a rich history of engineering excellence as a leading partner for the gas and steam turbine industry.
