Butterfly valve for bypass ducting of turbines for recovering mechanical energy from the exhaust gases for a catalytic cracking plant

摘要

This butterfly valve (₁), particularly for use in bypass ducting of turbines for recovering mechanical energy from the exhaust gases of a catalytic cracking plant, comprises a substantially cylindrical, hollow valve body (2) formed with two diametrically opposed bores (8, 9) which accomodate an actuating shaft (10) carried rotatably in the valve body (2). Keyed diametrically across the shaft (10) is a disk-like shutter (15) having opposite peripheral flat sealing surfaces (19, 20) for tight engagement by contact with abutment seats (21, 22) formed of a pair of semi-circular ribs formed on the body (2). The shutter (₁5) includes two wings (₁6, 17) attached to a diametrical hollow hub (18) for mounting on the shaft (10); the hub (18) has a shorter length than the shutter diameter, to enable machining of the shutter sealing surfaces (19, 20) on a turning lathe. The valve (1) also comprises a pair of bushes (25, 26) fitting slidingly within the bores (8, 9) in the valve body (2) between the shaft (10) and the body (2) itself and being urged elastically toward the shutter (15).;At each end of the shutter hub (18), the valve (1) has a respective sleeve insert (23, 24) welded to the shutter (15) as an axial extension of the hub (18). Each bush (25, 26) bears, therefore, on a respective sleeve insert (22, 24); advantageously, bush and insert have the same diameter.;With this butterfly valve (1), the sealing characteristic with the valve closed is greatly improved.