Rotary regenerative heat exchangers

Claim 1

In a rotary regenerative air preheater having a substantially cylindrical matrix and duct means for directing separate flows of air and flue gases through said matrix, said matrix and duct means being relatively rotatable, and movable sealing elements (5) to reduce the leakage between relatively moving confronting parts of the matrix and the duct means, a device for adjusting the position of a sealing element (5) comprising: an adjusting linkage (7-11) coupled to said sealing element (5); an hydraulic servo motor (12) coupled to said adjusting linkage for varying the effective length of said adjusting linkage and adjusting the position of said sealing element (5), said servo motor (12) including a cylinder (30) with a piston (33) therein defining a working chamber having an inlet (31) connected to a pressure fluid source; a spring (15) coupled as a yielding element to said linkage (711) and operatively connected to said piston (33) to bias said piston (33) to normally Counteract the hydraulic pressure in said working chamber; a fluid leakage passage forming a restricted outlet from said chamber to provide a delayed emptying of the chamber when the spring force of spring (15) exceeds the force caused by the pressure in the chamber acting on said piston (33); first sensing means (17, 18) sensing changes of the effective length of said adjusting linkage; a valve (37) in said servo motor inlet (31) which is coupled to said first sensing means and opened and closed responsive to said first sensing means; and second sensing means (36) sensing the hydraulic pressure in the inlet (31) of said servo motor (12), said second sensing means (36) being coupled to said valve (37) for opening said valve (37) independently of said first sensing means (17, 18) when the pressure in said inlet (31) falls below a predetermined value.