Bearings shall have a rated L10h lifetime of at least of 40,000 hours under the worst case operating conditions as specified in the requisition and in this specification. The lifetime shall be calculated in accordance with ISO 281.Sealed-for-life bearings shall be suitable, at an ambient temperature of 40℃, for at least 10,000 operation hours for 2-pole and 20,000 operation hours for 4-pole and higher machines.