After having completed a CPT test, the CPT sounding tubes are to be retrieved from the ground. A very straightforward way of pulling is using a pulling kit. Such a kit consists of a pulling bowl and pulling piece.
The pulling bowl is placed in the hole of the push-and-pull yoke of the penetrometer pusher and the pulling piece fits into the pulling bowl. It is supported by the large knob at the top.
The pulling piece is screwed on to the upper CPT tube in the yoke’s lowest position. When screwed firmly, the CPT string is lifted by the penetrometer pusher. The pulling piece is unscrewed when the penetrometer pusher has reached its highest position and the CPT sounding tube is unscrewed as well. This procedure is to be repeated until the last tube and cone have been retrieved.
The pulling piece is available with 4 different threads, fitting all CPT sounding tubes available and is provided with a longitudinal slot for the cable of electrical CPT. It is possible to mount an adapter on to the pulling piece for the pulling of casing tubes.
This method of pulling is quite laborious and is only to be applied when the time factor is less important.