The invention relates to on-off valve, particularly for insulation by-pass of
exhaust gas expansion turbines of catalytic cracking plants, of the type comprising
a hollow valve body, an opening for the inlet of the gas into the valve, an opening
for the outlet of the gas from the valve, at least a shutter and the relevant at
least one seat, the valve being characterized in that it comprises a conduit coupled
to the inlet opening and a conduit coupled to the outlet opening, the at least
one seat being coupled to the inlet conduit or to the outlet conduit and the at
least one shutter having a cover shape and sealing engaging with the seat by a
rotatory motion transmitted to the shutter by an actuator by a drive shaft and
a drive arm.
