A Novel Controlled-Motion Test Rig to Evaluate Effect of Synchronous and Subsynchronous Lateral Vibration on Reliability and Performance of Mechanical Seals in Pumps

Mechanical seals are commonly used in rotating machinery to contain liquid leakage past a rotating shaft. Pumps vibration often exhibit both synchronous and sub-synchronous whirling, whichA test rig was developed to simulate a running pump environment for the mechanical seal. The controlled-motion test rig comprises a flexibly-mounted-rotor connected to a pair of electrohydraulic shakers. This configuration allows imposing whirl orbits to a flexibly-mounted-rotor (FMR) mechanical seal at any prescribed frequency independent of rotor speed. A 6-axis load cell provides direct measurements of the reaction forces at the mechanical seal stationary component. Five Eddy current sensors and the capacity probes track the 5 DOFs of the mechanical seal dynamic face. The flow loop is a modified plan 54 with an external pump capable of 200 PSI at 8 GPM using VG 2 mineral oil, and an external heat exchanger to regulate oil temperature. Tests were performed on a 3-inch FMR seal. Input rotor whirl vibration was increased to 10 mils pk-pk, while cooling flow (VG2 mineral oil) was set to 2.25 GPM and pressure was varied from 50-150psi. The measurements include steady state values of temperature, power loss, clearance and leakage; and dynamic measurements of seal face wobble, wobble-imposed torque, relative lateral movement and fluid film shear.