Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Repair – replacement – or improvement
Patent
1997-09-24
1999-12-07
Taylor, Dennis L.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Repair, replacement, or improvement
175 53, 175 62, 405154, F16L 100
Patent
active
059972157
DESCRIPTION:
BRIEF SUMMARY
There is known from DE 37 33 463 C1 a method of changing pipes laid in the earth, in which an old pipe is removed and a new pipe is inserted in its place in the region between an insertion ditch and a target ditch. In this case a common drawing device pulls the old pipe to the target ditch and there breaks it up, and, following the old pipe, draws the new pipe from the insertion ditch to the target ditch. The drawing device engages on the rear end of the new pipe in the direction of drawing, the old and the new pipes being connected together positively by an adapter transmitting the forces occurring between them. A traction member, like a traction rod, comprising a plurality of short individual rods connected together by screw couplings, is pushed through the two pipes and brought into engagement with the rear end of the new pipe on the one hand and with the drawing device on the other hand. The traction rod is then drawn in stages towards the target ditch together with the two pipes, the drawing device executing upon each step a forward stroke in which the entire traction force acts on the traction rod, and a reverse stroke in which the traction rod is relaxed. If however long pipes or pipelines combined from a plurality of pipes are changed, considerable traction forces may be necessary. In this case the elastic expansion of the traction member during the forward stroke can be so great that this corresponds to a large proportion, sometimes considerably more than half of the stroke length. As the traction member is stressed and relaxed upon each step, i.e. is elastically stretched and then draws together again by the same distance, the actual feed of the pipes during one step corresponds to the stroke length of the drawing device minus the respective elastic stretch. In this way the feed of the pipes in one step can be considerably less than the stroke length of the drawing device, so that the efficiency of the drawing device is correspondingly reduced.
Accordingly, it is the object of the present invention to provide a method for drawing a pipe laid in the earth and/or to be laid in the earth to a ditch lying beneath the surface of the earth, and accessible therefrom, in which there is disposed a drawing device in engagement with a traction member, the traction member being passed through the pipe and engaging thereon behind its rear end in the direction of drawing, or the traction member engages on the pipe at the front end in the direction of drawing and is drawn towards the ditch with the pipe in steps by the drawing device, in such a way that the drawing device upon each step executes a forward and a reverse stroke, in which the feed of the pipe during one step corresponds to the entire stroke length of the drawing device, so that a reduction in efficiency does not occur even at high tensile forces.
This object is achieved according to the invention by the feature indicated in the characterising part of claim 1. Advantageous further developments of the method according to the invention and preferred devices for carrying it out are apparent from the sub-claims.
By virtue of the fact that the traction member during the reverse stroke is kept under a degree of tension corresponding to its elastic stretch during the forward stroke, the traction member is kept permanently in an elastically stretched state, so that the alternation of stretching and relaxation is eliminated in each step. As the drawing device is supported on the wall of the ditch facing the stretching path and forming an abutment, and this wall can be destabilised during a continuing alternation of stress and relaxation by loosening the earth, the method according to the invention also has the advantage that the abutment is better stabilized by the permanent stress.
A device for carrying out this method with an elastically stretchable traction member, which is passed through the pipe and is engagement acting in the direction of drawing therewith at its rear end in the direction of drawing, or which is in engagement acting in the direction o
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patent: 4626134 (1986-12-01), Coumont
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patent: 5205671 (1993-04-01), Handford
patent: 5282696 (1994-02-01), Solomon et al.
patent: 5439320 (1995-08-01), Abrams
patent: 5484232 (1996-01-01), Hayashi et al.
patent: 5782311 (1998-07-01), Wentworth
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