Abstract: A double-seat valve with an upper valve stem and a lower valve stem which, on the end, each have valve sealing bodies, each of which valve sealing bodies has a seal which is located on the balance diameter. One of the valve sealing bodies also has a center seal which is used to seal a leakage space when the valve stems are in the open position. The center seal also lies on the balance diameter. The other valve sealing body has a sealing collar, against which sealing collar the center seal is in contact when the valve stems are in the open position, so that even in this case, a sealing of the leakage space is guaranteed.

Abstract: A leak resistant, switching, double valve system consists of two sliding valve bodies in a valve housing with connecting lines. The two sliding valve bodies, which can be actuated independently of one another, are in contact in the closed position with valve seats in the valve housing, and are located at some distance one behind the other, forming a leak cavity between them. During the opening process, the first sliding valve body, before it leaves its valve seat, while simultaneously reducing the size of the leak cavity, can be placed in contact with the second sliding valve body, which is provided with a tubular extension which exits the valve housing in a sealed manner and connects the leak cavity to the environment of the valve system.