Large Wind Turbine Low-Speed Shaft Bearing - Sliding Instead of Rolling

This report introduces the replacement of traditional rolling bearings (Spherical Roller Bearings SRB / Double-Row Tapered roller bearings TRB) in large wind turbine main shafts (speed 10–30 rpm) with sliding bearings. Rolling bearings rely on point/line contact, while sliding bearings use a hydrodynamic oil film between the journal and bearing pads for surface-contact load transmission.

“Sliding instead of rolling” is a deterministic trend driven by wind turbine upscaling, cost reduction, and reliability demands. This transition is already mature in gearboxes and entering volume production (ZF has delivered 3000+ units, NGC 12000+, Envision's self-developed sliding bearings have exceeded 1000 units with zero failure). The main shaft (low-speed shaft) is the next frontier – Goldwind installed the world's first sliding main shaft prototype in 2021, and the industry is moving from prototype validation to small-batch production. The theoretical replacement ratio for main shafts can reach 100%, with a global market potential exceeding RMB 20 billion.

1. Typical System Configuration

Split-type radial bearing bush (e.g., 9-pad design) around the journal, each replaceable independently.

Thrust pads (e.g., 6-pad design) to carry axial loads.

Forced lubrication system: oil circulation, cooling, filtration, and labyrinth seals.

Tilting-pad / segmented structure to accommodate shaft deflection and misalignment.

Typical parameters from Shanghai Jiao Tong University Chongqing Research Institute: low speed <0.1 m/s, heavy load >15 MPa, frequent start-stop, 20-year service life.

2. Three Bottlenecks of Rolling Bearings under Upscaling

Nowadays, wind turbines are becoming Large-scale and heavy-duty. The megawatt technology of offshore wind turbines is constantly improving, which in turn forces the replacement of technologies.

1. Size bottleneck: onshore >15 MW, offshore >20 MW – the raceway diameter of main shaft rolling bearings approaches manufacturing limits.

2. Failure bottleneck: white etching cracks (WEC) and electrical pitting have become common failure modes; NREL statistics show rolling bearing failures account for over 67% of gearbox faults.

3. Cost and localization bottleneck: localization rate of main shaft bearings is only about 35%, gearbox bearings are nearly all imported – a critical “choke point”.

From 1 MW to 10 MW, main shaft bending moment increases about 25 times, far exceeding thrust growth (~11 times) – bending-moment-dominated conditions are exactly where sliding bearing surface contact excels.

3. Advantages of Sliding Bearings over Rolling Bearings

• Procurement cost reduced by ~30%, O&M cost by ~60%, total turbine cost reduction ~6.5% (CICC); life-cycle cost reduction ~4.5% (Guosheng).

• No rolling elements, inherently avoiding pitting, WEC, and electrical pitting; oil film damping absorbs vibration.

• Segmented pads enable single-pad replacement at tower top – offshore replacement of main bearings requires a crane vessel with daily rent of ~$250,000; Goldwind claims O&M cost reduction >60%.

4.OEM and Supply Chain Progress

4.1 Domestic OEMs

4.2 Bearing suppliers:

SUND: No.1 in China (No.6 globally) for hydrodynamic sliding bearings; design and test rig DNV-GL certified; first fully automatic laser cladding production line; 16 MW planetary pin sliding bearings in small-batch trial; 2023 wind sliding bearing revenue +275%, expected to double in 2025; SKF holds 6.96% and cooperates on “sliding instead of rolling”; 2025 revenue RMB 619 million (+19.5%), Q1 2026 RMB 162 million (+34.6%).

Shenke: first listed company for thick-wall sliding bearings, supplies Goldwind and Mingyang; set up offshore wind subsidiary in 2025; state-owned group took controlling stake in early 2026.

ChangSheng Bearing: completed 6 MW semi-direct drive gearbox sliding bearing tests, delivered for field trial.

Shuangfei: mass production of ultra-large power gearbox sliding bearings; Jinlei completed sample delivery.

International: Miba (mass production since 2019, expanding capacity, claims 20 MW feasible), Winergy, RENK, Kingsbury, Waukesha, GGB, etc.

5. Adoption timeline

Doubly-fed and semi-direct drive / medium-speed permanent magnet units are the main targets for main shaft sliding bearings; direct-drive units have extremely low speed and large diameter, making oil film build-up most difficult, with least public progress.

Current core technical challenges: oil film build-up at very low speeds (<0.2 m/s), start-stop wear, and size/weight trade-offs for large pads. As turbines move toward larger MW and deeper waters, the main shaft bearing faces rising contact stress, fatigue life constraints, and high O&M costs. “Sliding instead of rolling” – using large sliding bearings to replace traditional rolling bearings – offers oil film load sharing, uniform stress distribution, impact resistance, compact structure, and better life-cycle cost, becoming a key exploration direction for next-generation main shaft technology.

Our company has years of experience in large sliding bearings, with full-chain capabilities from material selection, structural design, lubrication simulation, precision manufacturing, to testing and validation. We have applied our products in heavy equipment, marine, metallurgy, and other high-load conditions, accumulating rich engineering experience. For the emerging field of wind main shaft sliding bearings, we look forward to exploring cooperation with OEMs, bearing peers, and research institutions – jointly advancing technical feasibility, prototype trial, and field validation – to contribute innovative solutions for cost reduction, efficiency improvement, and higher reliability in the wind power industry.