Angle seat valves are externally controlled valves. These valves are actuated by a direct supply of compressed air. In this process, the seat of the process valve is raised by a pneumatic actuator. In the normal position, the valve is closed by a spring. When the actuator is supplied with operating pressure, it raises the control piston as well as the valve disc – the valve opens. The valve seat is slanted at an angle of approx. 50° in relation to the media flow. The flow direction is determined by the design of the valve. Angle seat valves are used in applications in which absolute purity of the medium cannot be ensured, in which high-viscosity media are to be controlled or in vapour applications.