Schnepple, H.H.SchneppleSemler, G.G.Semler2022-03-082022-03-081991https://publica.fraunhofer.de/handle/publica/302525A diaphragm pump, which is intended primarily as a metering pump for use in biological process engineering and which has at least one automatically closing inlet valve and one outlet valve each, was fitted with additional conduit passages for the purpose of complete in-situ sterilization of the pump parts coming into contact with the product. These additional conduit passages avoid the valves by means of a bypass. They can be closed by means of valve stems and they are each connected to a annular space surrounding the inlet and outler valves.de608610620660patent1989-3937847