The Double Block and Bleed design features every technical advantage which the series TRI-CON has plus there is a true double block and bleed feature which delivers zero leakage. By using this design, the former two valve system with a spool piece becomes obsolete. With Zwick’s unique design of the linkage between the two shafts, the user is able to actuate both shafts with only one actuator and reach zero leakage with the two available sealing surfaces.