Why equalizing holes are provided in turbine rotor disc?

Equalizing holes are provided in turbine rotor discs to ensure uniform pressure distribution across the rotor during operation. These holes help to alleviate any potential imbalance caused by thermal expansion or pressure differentials, which could lead to mechanical stress or failure. By equalizing the pressure, the holes enhance the structural integrity and operational reliability of the rotor, contributing to improved performance and longevity of the turbine.