JPH0436768B

In order to prevent a probe (2) used for expanding tubes (1) in portions from having an uneven effect due to its eccentric position in a tube which is not completely straight, the probe given a slightly flexible design is provided with centering rings (11, 13) which flexibly rest on both the inner face of the tube and on the probe member. The flexible parts (7) of seals limiting the operational regions (8), along their circumference, then evenly and simultaneously contact the inner wall of the tube. Several designs for the centering rings are possible. To facilitate their introduction into the tube, the process of introduction is accompanied by a process of lubricating the inner tube parts, a process which improves sliding and for which the hydraulic fluid required in any case may be used.