The clamping system comprises a collar that comprises a belt suitable for being clamped around clamping surfaces projecting from tubes. The collar carries a series of angularly distributed foldable fingers, each finger presenting a free operating end projecting axially beyond the first edge of the belt over a distance that is sufficient to enable it to be manipulated by hand. Starting from an initial position in which the fingers define a rest minimum diameter, the fingers are suitable for being folded manually and plastically towards the axis of the belt in order to define a folded-in minimum diameter that is less than said rest minimum diameter.