Method of determining radial play in a bearing arrangement

A method for determining radial play of a bearing arrangement in a wind turbine gearbox in a wind turbine, the method comprising:

• providing the bearing arrangement in the wind turbine gearbox in the wind turbine, the bearing arrangement comprising at least a first component and a second component which are movable relative to one another in a radial direction to define the radial play of the bearing arrangement;
• capturing a first image of the bearing arrangement, wherein the first image includes the first component and the second component in a first relative position, said first relative position corresponding to an extreme radial position allowed by the radial play of the bearing arrangement;
• applying a radially-directed load to the bearing arrangement to move the first component radially with respect to the second component by a distance that defines the radial play of the bearing arrangement so that the first and second components are in a second relative position, said second relative position corresponding to an opposite extreme radial position allowed by the radial play of the bearing arrangement;
• capturing a second image of the bearing arrangement, wherein the second image includes the first component and the second component in the second relative position;
• and
• comparing the first and second images to quantify the difference between the first relative position of the first and second components and the second relative position of the first and second components, thereby to determine the radial play in the bearing arrangement.