Process for installing a section of packing in a casing

A casing comprising:

• an input opening having a circumference,
• a tubular wall extending in a longitudinal direction (L) between two longitudinal ends,
• and an inner face of the tubular wall that participates in delimiting a receptacle for a section of packing,
• a base wall positioned at a longitudinal end of the tubular wall opposite the input opening, and
• a device to assist installation of the section of packing, the device comprising:
• a cradle which extends from the tubular wall from the input opening, in the longitudinal direction, opposite the base wall, the cradle being configured to position the section of packing facing the input opening, and
• a removable cone which is configured to guide the fitting of the section of packing by centring the section of packing on the input opening, the removable cone being disposed at the input opening of the casing, the removable cone having a cross-section which is at least partly circular seen on a plane perpendicular to the longitudinal direction (L) and becoming enlarged going away from the input opening,
• wherein a longitudinal dimension of the cradle is larger than a longitudinal dimension of the removable cone, wherein the cradle and the removable cone extend one after the other around all of the circumference of the input opening of the casing such that the cradle and removable cone do not overlap in the circumferential direction.