The Radioactive Isotope Beam Factory (RIBF) is a cyclotron-based accelerator facility capable of providing the world's most intense RI beams over the whole range of atomic masses. The world's first superconducting ring cyclotron (SRC) is the final booster in the RIBF accelerator complex, and is capable of accelerating all-element heavy ions to a velocity of about 70% of the speed of light. The ring cyclotron consists of six major superconducting sector magnets cooled by a helium refrigerator having a total equivalent cooling capacity of 1 kW@4.4 K. The helium cooling system was successfully operated from 2005 for fruitful experimental campaigns with a reliability of 97%, although we experienced two serious problems related to oil contamination and a helium leak that took more than 100 days to repair.