Abstract: A modular device for a fixed arrangement and interconnection of individual separation units and/or first functional units for performing one or more unit operations in a biotechnological process. The modular device includes a plurality of distributor caps provided for attachment to the separation units and/or first functional units. The distributor caps each have: a fluid distribution mechanism having a working connection and at least two supply or discharge connections, wherein the fluid distribution mechanism can assume at least two defined switching positions; connection mechanisms for establishing a flow communication between a fluid inlet or outlet of the separation unit or the first functional unit and the working connection of the fluid distribution mechanism; coupling mechanisms for establishing a rigid mechanical coupling and a flow communication with an adjacent distributor cap; and an interface for changing the switching positions of the fluid distribution mechanism.