A telescopic joint for connecting two pipes in a separating vessel of a fluid catalytic cracking unit includes a first pipe and a second pipe; wherein the two pipes are connected together at their ends by a sliding ring comprising a first portion extending substantially parallel to the first and second pipes, and a second portion extending substantially perpendicular to the first and second pipes, to thereby form an L profile; the first pipe comprises a fitting seat fixed at its end, and a flanged ring, the flanged ring and the fitting seat being configured to surround at least partially the second portion of the sliding ring; and the telescopic joint comprises a first plurality of gaskets positioned in a first space between the second portion of the sliding ring and the fitting seat and distributed in a direction parallel to the second portion of the sliding ring.