Experience on replacement of vibration isolator of primary coolant pumps, Cirus

Full text: The Primary coolant pumps of Cirus reactor (40 MWt power) delivers 1200 igpm flow at 562 feet head. There are five pumps out of which four are operating in parallel. The pump base frame is fixed on concrete slab, which is mounted on cork pads for isolating its vibration to the surrounding area. The cork pads have been in service for the past 40 years. During the refurbishing outage of the reactor, an assessment of the vibration isolation efficiency of foundation was carried out. The results indicated that the isolation efficiency had reduced to nil and hence it was decided to replace the vibration isolators. Detailed theoretical study was carried out for selection, testing and installation of new cork pad for the pumps. The pump foundation frequencies were also theoretically evaluated and correlated with the measured values. The paper highlights the assessment of the isolating material, proper selection, and subsequent replacement to achieve required isolation efficiency. The job was carried successfully during the refurbishing outage of the CIRUS reactor