Abstract: A valve unit comprises an operating piston for closing and opening a connection between a process pressure input line and a process pressure output line, at least one control line and at least one control chamber for controlling the operating piston. The operating piston has a closing ring which in the closed state of the connection sealingly abuts a valve seat of the valve housing (or the valve housing has a closing ring which in the closed state of the connection sealingly abuts against a valve seat of the operating piston). The valve seat consists of a softer and more elastic material than a circumferential sealing edge abutting said valve seat. An annular sealing element is present which comprises the valve seat. The sealing element has the shape of a truncated cone with an outwardly widening base.

Abstract: A valve unit includes a valve housing having an input line and an output line or the process pressure as well as a process guide shaft, an operating piston for closing and opening a connection between the two lines, two control lines and two control chambers for controlling the operating piston. The operating piston has a closing ring which in the closed state of the connection sealingly abuts a valve seat of the valve housing and it has a diameter which corresponds to a guide diameter of a dynamic process seal. The valve seat includes a softer and more elastic material than the sealing edge. The valve unit has low axial forces, due to low sealing forces, thus makes a long service life with a high number of cycles of operation possible.

Abstract: A valve unit includes a valve housing having an input line and an output line or the process pressure as well as a process guide shaft, an operating piston for closing and opening a connection between the two lines, two control lines and two control chambers for controlling the operating piston. The operating piston has a closing ring which in the closed state of the connection sealingly abuts a valve seat of the valve housing and it has a diameter which corresponds to a guide diameter of a dynamic process seal. The valve seat includes a softer and more elastic material than the sealing edge. The valve unit has low axial forces, due to low sealing forces, thus makes a long service life with a high number of cycles of operation possible.

Abstract: A valve has a valve housing in which a closure element having at least one sleeve section is movable along its sleeve longitudinal axis by an actuator to open and close a fluid connection between a fluid inlet and outlet. The actuator has stationary and movable parts relative to the valve housing. At least the movable parts and the closure element are arranged entirely within an enclosed fluid space between the fluid inlet and outlet. To close the fluid connection spaced first and second seal devices of a double-sealed seat are in sealing contact with equally-spaced first and second counter-seal devices on the valve housing along first and second closed seating lines, respectively. With regard to the at least one double-seal seat, the ratio between first and second areas enclosed by first and second sealing lines in projection along the sleeve longitudinal axis, respectively, is between 6/10 and 10/6.

Abstract: A valve has a valve housing in which a closure element having at least one sleeve section is movable along its sleeve longitudinal axis by an actuator to open and close a fluid connection between a fluid inlet and outlet. The actuator has stationary and movable parts relative to the valve housing. At least the movable parts and the closure element are arranged entirely within an enclosed fluid space between the fluid inlet and outlet. To close the fluid connection spaced first and second seal devices of a double-sealed seat are in sealing contact with equally-spaced first and second counter-seal devices on the valve housing along first and second closed seating lines, respectively. With regard to the at least one double-seal seat, the ratio between first and second areas enclosed by first and second sealing lines in projection along the sleeve longitudinal axis, respectively, is between 6/10 and 10/6.