A special purpose steam turbine has started to experience intermittent radial vibration spikes. The turbine is used to drive a Hydrogen Recycle Gas Compressor in Aromatics unit. No abnormality observed on the compressor end. ADRE 408 external data acquisition and diagnostic system was used to collect vibration data during steady state operation. Detailed vibration diagnosis was performed to evaluate overall rotor dynamic behavior of the machine train, assess vibration levels against the OEM set-points and ISO 7919-3 standards, troubleshoot potential mechanical malfunctions that leads to intermittent vibration spike and provide recommendations for safe operation of the unit. From the analysis, the cause of high vibration was determined to be intermittent light rubbing of the steam turbine rotor with the bearing housing oil baffle (seal).