Subsea system for processing fluid

A subsea system for processing a fluid emanating from one or more subsea wells, comprising a fluid processing circuit and a base module provided with at least one receiver for receiving an insert module comprising an appliance that forms part of the fluid processing circuit, the receiver comprising a cavity for accommodating the insert module, the insert module being adapted to be mounted to the base module by being lowered down substantially vertically into the cavity of the receiver through an opening at the upper part of the cavity and demounted from the base module by being lifted substantially vertically out of the cavity the receiver being provided with at least one fluid outlet and at least one fluid inlet adapted to be in fluid communication with a corresponding fluid inlet and fluid outlet, respectively, of the insert module when the insert module is mounted in the cavity of the receiver, wherein the insert module is provided with a flange, which is adapted to bear on a corresponding flange of the receiver when the insert module is mounted therein, a watertight seal being arranged between said flanges so as to seal the space between the receiver and the part of the insert module received therein from the surrounding sea water.