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Repair method for main shaft bearing seats

IP.com Disclosure Number: IPCOM000246866D
Publication Date: 2016-Jul-08
Document File: 2 page(s) / 241K

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The IP.com Prior Art Database

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This is the abbreviated version, containing approximately 52% of the total text.

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Repair method for main shaft bearing seats

Introduction


Thermal spray repair of journal bearings has been used in a wide field of applications for years. However, it is now suggested to be used in wind turbines as well; primarily for wind turbine shafts.

Summary


The wind turbine main shaft transmits the torque from the blade hub to the gearbox and the rotor forces through the main bearing(s) to the machine frame and tower. The thermal spray repair restores the fit between the main shaft and the main bearing inner ring(s).

Bearing seats tend to get worn by fretting by normal operation of a Wind Turbine Generator. Wear marks covers up to 30% of the seat area and can be approximately 0.5 mm deep. By removing the damaged material underneath the bearing by turning or grinding and re-building by thermal spraying the shaft can by refurbished at relatively low cost compared to new shafts.

This repair method is useful for repairing main shafts of both quenched and tempered steel and casted ductile iron where damaged main bearing seats (typically due to fretting) are repaired by 420 Stainless Steel thermal spray process.

This repair is at least applicable for steel types 34CrNiMo6 (AISI 4340) and 42CrMo4 (AISI 4140) and for ductile iron EN-GJS-400-18-LT.

The use hereof may lead to huge cost savings as compared to shaft replacements. Repair costs about one fourth of a new shaft, and it may in some situations be much faster than manufacturing a new shaft.

Procedure


Surface preparation procedure
The damaged bearing fit on the main shaft will be machined and undercut depending on depth of damage.

A minimum wide band will remain un-cut on both ends of the fit. It is important that the spray repair is limited to the compression zone under the bearing. Hence is the fit defined as the contact zone between bearing inner ring and shaft - bearing width excluding the end radii.


The undercut shall end in a radius minimum, as seen in figure 1.

Figure 1: Schematic of repair...