Efficient heat transfer surfaces, effective sealing arrangements, uncomplicated design, and easy accessibility are among the many reasons why the Ljungström® air preheater is so often selected.  Metallic heat transfer surfaces are contained in the rotor that turns at 1 to 3 rpm, depending on the size of the unit. The rotor housing and rotor have sealing members to form separate gas and air passages through the heat exchanger. The rotor drive unit, cleaning device mechanism, rotor bearing assemblies, and sealing surface adjuster are all located externally and are readily accessible while the unit is in operation. Heat transfer surfaces are visible through lighted ports during operation. A view of the internal structure of the Ljungström® air preheater shows the rotor post with top and bottom trunnion headers. The sealing surfaces for the radial and axial seals are also shown. A completed rotor with radial and axial seals attached to each sector-shaped compartment. The pin rack at the bottom of the rotor accepts the drive mechanism and also serves as a circumferential bypass sealing surface. A Leakage Control System That Uses Thermal Growth to Maintain Sealing Efficiency The advanced sealing system of the Ljungström® air preheater is a result of an evolution of devices and methods to develop a sealing system that is capable of successfully controlling and minimizing air-to-gas leakage. The design takes advantage of normal thermal growths to achieve effective sealing with a minimum of maintenance requirements. Along the radial and axial length of each rotor diaphragm are attached light-gauge leaf-type seals. During operation these seals pass in close proximity to the sealing plates that are located within the air preheater housing. Two radial sealing plates (sector plates) are located at each end of the rotor. Two axial sealing plates are diametrically opposite each other in line with the sector plates. Collectively, these create a sealing "zone" between the air and gas streams. To prevent air and gas from bypassing the rotor through the small space between the rotor and housing, circumferential bypass seals are provided. Ask for complete descriptive literature covering Ljungström® air preheater sealing systems. Double Radial and Axial Seals Reduce Direct Leakage In most applications where air-to-gas pressure differentials are sufficiently high, radial and axial sealing effectiveness is further enhanced by a double sealing system that creates a moving plenum across the sealing surface. The formation of this intermediate-pressure plenum between the air and gas streams serves to reduce the air-to-gas pressure differential by a factor of nearly two. This decrease in pressure differential can reduce direct leakage by as much as 30 percent. The double sealing system can also be applied to existing air preheaters. Automatic Radial Sealing Control The actuated sealing system minimizes the direct air-to-gas leakage that is caused by changes in hot end radial seal clearance when the rotor approaches its operating temperature. It automatically adjusts the radial sealing plates as it responds to changes in seal clearance detected by a rotor position sensor. › Locate a Salesperson