A pitch bearing connects a wind-turbine blade to its hub and allows the blade angle to change. However, a familiar outside diameter or the name blade bearing cannot identify its internal design or mounting interfaces. Buyers should first establish which ring attaches to the blade and which attaches to the hub. The approved drawing must then define both interfaces and the bearing construction.
A replacement review also needs the specified loads, seals, lubrication points, and inspection criteria. Where the pitch system uses gearing, the gear and mating drive details matter as well. This guide explains how to compare those features and prepare a drawing-based inquiry without assuming that a similar-looking ring will fit.
The pitch bearing is a large slewing ring between the blade root and hub. One ring fastens to the blade side, and the other to the hub side. A pitch drive rotates the movable ring through a limited angular range. The bearing transmits axial and radial reactions and overturning moment through its raceways and bolted interfaces. Its slow oscillating motion differs from a continuously spinning shaft bearing.
Wind pitch rings can use four-point-contact ball, multiple-row ball or roller arrangements, depending on the design. Ball count, contact geometry, row spacing, clearance or preload and ring stiffness affect load sharing. A bearing that appears similar externally may behave differently under blade moment. The approved section drawing, not a generic series description, must define the internal construction.
Seals and grease passages also form part of the product. They protect raceways and feed lubricant into the specified zones. A custom ring with the correct bolt circles but misplaced grease ports may conflict with the hub layout. For this reason, the buyer should treat seals, fittings and plugged holes as controlled drawing features.
Measure the bore, outside diameter and total height, then identify both mounting faces. The blade-side and hub-side bolt circles can differ. Each side needs hole count, pitch-circle diameter, hole diameter, thread or through-hole detail, counterbore if present, and angular orientation relative to the ring features. Confirm which ring rotates in the installed assembly.
The section drawing should locate shoulders, centering features, seal grooves and any reinforcement or adapter plate. A change in ring height or flange position can shift the blade interface even if bore and outside diameter remain unchanged. The tolerance scheme matters at this scale: a nominal dimension does not show allowable flatness, runout or bolt-pattern position.
| Drawing area | Detail to supply | Purchase consequence |
| Blade interface | Bolt circle, face, centering and orientation | Determines blade-root fit |
| Hub interface | Separate bolt circle and support geometry | Determines hub-side mounting |
| Ring section | Height, locating features and seal grooves | Defines section fit and mounting details |
Liebherr lists KUD01706-030WJ15-900-000 as a double-row four-point slewing bearing for applications such as rotor-blade adjustment. Its published data give outer and inner bolt-circle diameters of 1,773 mm and 1,636 mm, with 52 mounting holes on each ring. The listed total height is 123 mm. These dimensions illustrate why both interfaces need separate checks.
Record the datum and inspection method for each bolt circle; nominal diameter alone cannot confirm a large ring fits both interfaces. Where the removed bearing is available, photographs and measurements help reconstruct a missing drawing. They do not, by themselves, reveal internal contact geometry or design load rating.
If the pitch drive engages gear teeth on the bearing, identify whether the teeth are on the inner or outer ring. Record the tooth count, module or diametral pitch, pressure angle, face width and specified profile details. Include the mating pinion and backlash requirements. For a different drive arrangement, provide its actuator and bearing-interface drawings instead. Do not infer tooth form from the ring’s outside diameter.
Blade loads change with wind and pitch angle. A product review therefore needs the approved axial and radial loads, overturning moment, operating angle and oscillation duty. Contact patterns may concentrate in a limited raceway sector. Material and heat treatment, raceway hardness and ring stiffness should be specified against the approved design, rather than assumed from a broad “heavy-duty” label.
Supporting structure can change how these loads enter the bearing. An insufficiently stiff or uneven mounting face may distort the rings after bolting. A stronger-looking ring cannot compensate automatically for a different flange or bolt arrangement. If a redesign is proposed, the turbine designer must validate the entire interface.
Agree on checks that reflect the drawing. These may include bore, outside diameter, height, mounting-face flatness, runout, bolt-hole position, gear geometry, seal fit and grease-port location. Raceway condition, material and hardness requirements can be included where the order specification calls for them. Record the measurement method and acceptance limits before production or sourcing.
Before accepting a replacement ring, compare its marking, orientation and part revision with the approved specification. Review the required inspection records against those limits. Matching outside dimensions alone cannot establish that the delivered ring meets the approved design.
A complete RFQ should identify the turbine and define exactly which bearing and supporting parts the plant needs. Group the technical information as follows:
Photograph the removed ring’s marking, orientation, gear teeth if present, seals and visible raceways. Localized wear may relate to load, lubrication or flange distortion; it does not alone establish a need for new internal geometry. HSN can review a complete model, approved drawing or measured sample for sourcing or custom manufacturing. Agree on dimensional, material and hardness evidence before ordering.
For a U.S. purchase linked to a blade replacement window, provide the drawing-approval deadline and required receiving date. Those dates are more useful than an unqualified request for “immediate stock.” The responsible engineer should review any proposed design change before procurement approves the order.
Is a blade bearing the same as any pitch ring?
Blade bearing names the position; construction and interfaces remain turbine-specific.
Can matching diameters confirm a replacement?
No. Compare both bolt circles, section, gear, seals, internal design and load requirements.
What should a U.S. pitch-bearing RFQ include?
Send the approved drawing, quantity, inspection scope, approval deadline and receiving date.
Why source a pitch bearing through HSN?
HSN can review both interface drawings, agree on inspection records and report custom or stock options with lead time.
For detailed wind turbine pitch bearing models not listed above, please contact HSN for model confirmation and supply discussion. When checking other bearing references, you can also send the complete model, photos, dimensions, quantity, application, and working conditions.
This article is based on independent analysis of publicly available technical information and industry understanding for knowledge sharing. All brand names and trademarks mentioned belong to their respective owners. HSN Bearing Group is an independent bearing supplier and technical service provider.
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