Retractable assembly

A retractable assembly for immersion, flow and attachment measuring systems in analytical process technology for measuring at least one measured variable of a medium in a containment, comprising:

• a hollow, cylindrically shaped housing having a longitudinal axis and having an interior with a service chamber formed therein, the housing including an encircling groove open to its interior, wherein the groove includes a designated seal expansion space expanding the groove, the designated seal expansion space disposed on a side of the groove facing away from the interior;
• an immersion tube having an end region, wherein the immersion tube is movable axially in the housing between a service position withdrawn from the medium and a process position in which the immersion tube extends into the medium, wherein in the service position the immersion tube is positioned in the service chamber;
• a seal positioned in the groove, wherein in the service position the seal externally closes and gap-freely seals off the service chamber from the environment at the seal and an external end region of the immersion tube in that the external end region lies against the seal;
• wherein a portion of the seal expands into the designated seal expansion space when exposed to a temperature change;
• wherein the housing includes a leakage path connecting the designated seal expansion space with the environment;
• and
• a device for detection a liquid or a medium in the leakage path.