Clearance control of a mechanical face seal

Seal clearance control is an advancement in noncontacting mechanical face s eal operation because seal clearance variation caused by process disturbanc es may cause either severe face contact or excessive leakage, each of which is regarded as seal failure. The objective of this research is to control the seal clearance at a desired value overcoming operation disturbances, in cluding variations in shaft speed and sealed fluid pressure. A flexibly mou nted rotor (FMR) noncontacting mechanical face seal test rig is used in thi s study. The clearance control concept is to adjust the closing force that acts upon the flexibly mounted rotor The seal clearance is measured by an e ddy current proximity probe. The seal axial dynamic model is experimentally determined for the design of a proportional-integra (PI) controller with a nti-windup. The controller is then applied to the test seal. Results show t hat the controlled seal maintains or follows see-point clearance changes wi th and without disturbances in sealed water pressure and shaft speed The co ntrolled seal is shown to respond quickly (having a small time constant) wi th a small control effort.