Patent ID: 8627878

Claim:
A rotary air preheater, comprising: a stationary housing having a rotatable rotor disposed therein, said rotor having opposing ends, the opposing ends being in communication with at least one air duct for flowing combustion air therethrough and at least one flue gas duct for flowing flue gas therethrough, wherein said rotor is divided into a plurality of sections by radially extending diaphragms; a plurality of sector plates, wherein one sector plate is in sealing relation with respect to one of said opposing ends of said rotor; a flange fixedly attached to said rotor and extending circumferentially around at least one of said opposing ends of said rotor; and a sensing device coupled to at least one of said sector plates, said sensing device for sensing a distance between said at least one sector plate and said flange, wherein said sensing device comprises: a compressed air conduit for directing a jet of compressed air onto said flange, said compressed air conduit having a first pressure tap positioned in proximity to a point at which said jet is output onto the flange, the first pressure tap being configured to determine backpressure at a point inside in the compressed air conduit; a first sensor in communication with said first pressure tap, the first sensor being configured for sensing the backpressure, the first sensor being an electrical sensor; a second pressure tap in communication with at least one of said at least one air duct and said at least one flue gas duct, said second pressure tap being in communication with said first sensor; and wherein said first sensor generates outputs for determining said distance between said at least one sector plate and said flange based upon a difference in pressure measurements taken at said first pressure tap and said second pressure tap.