Seal assembly for rotating shaft

摘要

A seal assembly for use in precluding leakage of hot combustion products along the shaft of a rotating heat exchanger wheel utilized in a power plant. The seal assembly includes a housing positioned in surrounding relation to the shaft and defining an annular chamber around the shaft having an inboard end and an outboard end; a positive annular fluid seal with the shaft proximate the outboard end of the chamber; and a leakage annular fluid seal with the shaft proximate the inboard end of the chamber. The positive annular fluid seal comprises a packing ring surrounding the shaft and an annular bladder positioned in surrounding relation to the packing ring and constrained against radial enlargement so that the bladder expands radially inwardly in response to receipt of pressurized fluid to urge the packing ring into sealing engagement with the shaft. Pressurized air is delivered to the chamber for leakage past the inboard leakage seal by delivering primary incoming pressurized air for the boiler to the chamber so that the pressurized air may flow out of the chamber past the leakage seal to preclude the entry of hot dirty combustion products into the chamber along the shaft and thereby preclude the entry of the combustion products into the general environment of the plant.