EP0452021A1 - Vorrichtung und Verfahren zum Ausheben von Gräben - Google Patents

Vorrichtung und Verfahren zum Ausheben von Gräben Download PDF

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Publication number
EP0452021A1
EP0452021A1 EP91302887A EP91302887A EP0452021A1 EP 0452021 A1 EP0452021 A1 EP 0452021A1 EP 91302887 A EP91302887 A EP 91302887A EP 91302887 A EP91302887 A EP 91302887A EP 0452021 A1 EP0452021 A1 EP 0452021A1
Authority
EP
European Patent Office
Prior art keywords
trench
plough
terrain
producing
depth
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP91302887A
Other languages
English (en)
French (fr)
Inventor
Malcolm Rutter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Northern Ocean Services Ltd
Original Assignee
Northern Ocean Services Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Northern Ocean Services Ltd filed Critical Northern Ocean Services Ltd
Publication of EP0452021A1 publication Critical patent/EP0452021A1/de
Withdrawn legal-status Critical Current

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F5/00—Dredgers or soil-shifting machines for special purposes
    • E02F5/02—Dredgers or soil-shifting machines for special purposes for digging trenches or ditches
    • E02F5/14—Component parts for trench excavators, e.g. indicating devices travelling gear chassis, supports, skids
    • E02F5/145—Component parts for trench excavators, e.g. indicating devices travelling gear chassis, supports, skids control and indicating devices
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F5/00—Dredgers or soil-shifting machines for special purposes
    • E02F5/02—Dredgers or soil-shifting machines for special purposes for digging trenches or ditches
    • E02F5/10—Dredgers or soil-shifting machines for special purposes for digging trenches or ditches with arrangements for reinforcing trenches or ditches; with arrangements for making or assembling conduits or for laying conduits or cables
    • E02F5/102—Dredgers or soil-shifting machines for special purposes for digging trenches or ditches with arrangements for reinforcing trenches or ditches; with arrangements for making or assembling conduits or for laying conduits or cables operatively associated with mole-ploughs, coulters

Definitions

  • the present invention relates to a method of and apparatus for trenching.
  • Trenching is a particularly viable option for protecting the small but hot flowlines which are being laid in current North Sea developments. Such flowlines are prone to upheaval buckling due to the large compressive forces which arise from high operationg temperatures.
  • the flowlines are usually restrained from upheaval buckling by a continuous rock cover at a specified height above the top of the flowline.
  • the plough After a short distance the plough will have responded to the change in sea bed depth, and will return to cutting the same constant depth of trench.
  • Existing ploughs are therefore beneficial towards preventing upheaval buckling, particularly if the plough is of a 'long beam' design, but can only do so to a limited degree.
  • a method of producing a trench in an irregular terrain including the steps of progressively moving trench producing apparatus over the terrain in order to produce a trench in that terrain, adjusting the trench depth of the trench producing apparatus ahead of or at an irregularity in order to reduce the effect of that irregularity on a flowline placed in the trench.
  • apparatus for producing a trench in an irregular terrain comprising trench producing means disposed for insertion into the surface of the terrain, means for supporting the apparatus above the trench to be produced, means for adjusting the relative position of the means for supporting and means for producing to enable trench depth to be varied and control means for adjusting the relative postion ahead of or at irregularities in the surface.
  • the apparatus comprises a plough
  • the means disposed for insertion comprise one or more plough shares
  • the means for supporting comprise skids
  • the means for adjusting enable the distance between share(s) and skids to be altered.
  • the skids and share(s) are attached to a plough beam.
  • the control means effectively gives the apparatus intelligence.
  • the ideal profile at the bottom of the trench is perfectly flat and level. This is quite feasible for a plough which can adjust its cutting depth as it moves along the pipeline.
  • it will not be possible to achieve a perfectly flat trench bottom if the variation in sea bed profile exceeds the available change in share setting. Under such circumstances it is desirable to know the variation in sea bed profile ahead of the plough, so that the 'severity' of any imperfections can be limited. If the plough can react to expected imperfections well in advance, then the maximum severity of the imperfection can be greatly reduced.
  • a simple plough which adjusts its cutting depth according to an instantaneous sea bed profile would not react to a large upwards imperfection until the required trench depth was less than the share setting depth. The plough would then follow the sea bed profile until the required trench depth was less than the maximum cutting depth. In contrast, if the plough could react to the imperfection in advance, then the trench depth could be controlled to give a smooth trench bottom profile over the imperfection.
  • Upheaval buckling is dependent on the height of upwards imperfections, or 'humps' in the profile on which the pipe rests. In comparison, downwards imperfections are of relatively little importance. A hot flowline will tend to sag down into such an imperfection, and will not affect upheaval buckling unless buckling is possible on either side of the sag. The required profile at the bottom of the trench will therefore have the minimum number of, and lowest, upwards imperfections. A limit on downwards imperfections will exist, such as on the basis of maximum bending criteria or local buckling in the sag. However, this limit may not be reached if the smoothing action of the plough beam prevents the cutting of such sharp imperfections.
  • the required trench bottom profile can be calculated on the basis of the criteria above.
  • the required plough share depth settings can then be determined in terms of the plough position along the flowline.
  • the plough can then be operated by controlling the share depth at any distance along the flowline according to this predetermined share depth.
  • the structure is in three parts hinged together high up above and beside the pipe. It comprises front and rear pipe supports 1 and 2, steering arms 3, steering linkages 4, skids 5, a tow bridle 6, share opening cylinder 7, control and hydraulics package 8, lift point 9 four cutter 10 and pipe grab assembly 11.
  • the plough is opened and closed by hydraulic rams above the hinges to permit lifting and lowering of the pipe. When the two lower parts of the plough are closed they lock together to form a single integrated structure.
  • the structure of the plough beams places them either side of the pipe rather than over or under it.
  • the main front structure bridges over the pipe with a large clearance above it to permit the plough to sink when encountering pipe spans. This bridge is placed near the centre of the plough so that it can pitch through a large angle.
  • the main towing forces are transmitted directly into the front of each of the beams and are carried down the sloping shields under the pipe and into the plough shares at ground level. This results in low beinding moments being applied to the beams.
  • the plough supports the pipe on widely separated support rollers at the front and rear of the plough. This dual support is necessaryy if smaller pipes are not to be overstressed.
  • the high clearance above the pipe and the central positioning of bridging structure permits the plough to pitch 9 degrees either way with a 12 inch pipe. This is increased for smaller pipes.
  • the support on the pipe is maintained by adjusting the elevation of one set of rollers. This is done automatically by the plough hydraulic system.
  • the high clearance and good pitch capability enables large pipes with piggy backed small pipes on their top sides to be safely trenched.
  • the pipe is lifted up into the plough by separate pipe lifters.
  • the vertical and sideways forces between pipe and plough are measured by load cells in the roller cradles.
  • the vertical pipe forces vary from 24 tones for a heavy concrete 36 inch pipe, to less than 1 tonne for a 6 inch epoxy-coated pipe.
  • a range of different pipe support links, rollers, hydraulic cylinders and load cells are provided.
  • the plough is fitted with a steering system. Steering arms on either side of the plough can be driven backwards and forwards by two hydraulic cylinders. A linkage between the arms keeps them in a proper relationship and minimises the power required from the hydraulic cylinders. The ends of these arms are connected to the ends of a triangular bridle, which is itself connected to the two rope.
  • Movement of the arms has the effect of moving the apex of the bridle sideways across the front of the plough.
  • the plough can be steered by using the towing vessel alongside the correct track.
  • the plough is fitted with thrusters foe and aft which enable it to be rotated and shifted sideways to locate on the pipe. This is facilitated by the wide gap between the shares and pipe lifter jaws in the open position.
  • the plough is lifted from the single lift point 9 high up above its centre of gravity.
  • the recovery system includes a plough mounted hydraulically operated winch which renders to release a buoy and messenger/haul down line.
  • the buoy is recovered on surface and the main lift line and latch pin returned to the plough by hauling down with the hydraulic winch under constrant tension.
  • Figure 4 shows the position of the trench T with a "small" sea bed irregularity. As the sum of the maximum height M of the irregularity over the normal plane P of the sea bed and the depth D of the trench is less than the maximum trench depth which the plough can accommodate, the trench may remain horizontal as shown.
  • Figure 5 shows the position of the trench T with a large sea bed irregularity.
  • the plough is aware of the approaching irregularity steps can be taken to minimize the abruptness with which the contour of the trench is changed.
  • the variation in the trench contour is spread over a greater distance by reducing the trench depth at the beginning B of the irregularity.
  • the ratio between the maximum contour height variation H and the distance L1 or L2 over which this occurs is less in Figure 5 than in Figure 6. i.e. H L1 ⁇ H L2
  • the trench depth is altered by changing the height of the shares relative to the front skids of the plough. This is controlled from a support vessel while the plough is in operation. By varying the trench depth as the plough moves along the pipeline, any imperfections can be significantly reduced. As an increase in sea bed level is reached, the share setting will be increased, the plough will cut a deeper trench through the 'hump' and a smooth level trench will result. If any 'hollows' are encountered in the sea bed, then the plough will cut a shallower trench through the hollow, and will cut a level trench again. With appropriate control, the 'smart' plough can achieve the specification for overbed imperfection sensitivity, and to a much greater extent than existing ploughs.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Mechanical Engineering (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Earth Drilling (AREA)
EP91302887A 1990-04-07 1991-04-02 Vorrichtung und Verfahren zum Ausheben von Gräben Withdrawn EP0452021A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB909007959A GB9007959D0 (en) 1990-04-07 1990-04-07 A method of and apparatus for trenching
GB9007959 1990-04-07

Publications (1)

Publication Number Publication Date
EP0452021A1 true EP0452021A1 (de) 1991-10-16

Family

ID=10674114

Family Applications (1)

Application Number Title Priority Date Filing Date
EP91302887A Withdrawn EP0452021A1 (de) 1990-04-07 1991-04-02 Vorrichtung und Verfahren zum Ausheben von Gräben

Country Status (3)

Country Link
EP (1) EP0452021A1 (de)
GB (1) GB9007959D0 (de)
NO (1) NO911296L (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2285821A (en) * 1994-01-25 1995-07-26 Soil Machine Dynamics Ltd Trenching plough
WO1999023314A1 (en) * 1997-11-04 1999-05-14 Coflexip, S.A. Steerable underwater plow
GB2353305A (en) * 1999-07-22 2001-02-21 Engineering Business Ltd Plough with vibrating member positioned forward of the share
WO2001021900A1 (en) * 1999-09-21 2001-03-29 The Engineering Business Ltd Ploughs
WO2007149145A1 (en) * 2006-06-23 2007-12-27 Caterpillar Inc. System for automated excavation entry point selection
WO2017017599A1 (en) * 2015-07-28 2017-02-02 Saipem S.P.A. Trenching assembly for laying in a trench a continuous pipeline and trenching method

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB748086A (en) * 1953-03-26 1956-04-18 Turner Cooper Improvements in or relating to apparatus for the formation of mole drains
GB1015160A (en) * 1963-02-04 1965-12-31 Weimar Werk Veb Machine for mole drainage and mole pipe drainage
GB1107303A (en) * 1965-04-30 1968-03-27 Rank Organisation Ltd Guidance system for machinery
GB1244400A (en) * 1969-10-31 1971-09-02 Crispin Leslie Myers Improvements in or relating to trenchless pipe laying apparatus
FR2506114A1 (fr) * 1981-05-21 1982-11-26 Pelsy Gilles Dispositif correcteur de devers sur un outil de travail du sol telle qu'une draineuse

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB748086A (en) * 1953-03-26 1956-04-18 Turner Cooper Improvements in or relating to apparatus for the formation of mole drains
GB1015160A (en) * 1963-02-04 1965-12-31 Weimar Werk Veb Machine for mole drainage and mole pipe drainage
GB1107303A (en) * 1965-04-30 1968-03-27 Rank Organisation Ltd Guidance system for machinery
GB1244400A (en) * 1969-10-31 1971-09-02 Crispin Leslie Myers Improvements in or relating to trenchless pipe laying apparatus
FR2506114A1 (fr) * 1981-05-21 1982-11-26 Pelsy Gilles Dispositif correcteur de devers sur un outil de travail du sol telle qu'une draineuse

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2285821A (en) * 1994-01-25 1995-07-26 Soil Machine Dynamics Ltd Trenching plough
WO1999023314A1 (en) * 1997-11-04 1999-05-14 Coflexip, S.A. Steerable underwater plow
US6050009A (en) * 1997-11-04 2000-04-18 Coflexip, S.A. Steerable underwater plow
GB2353305A (en) * 1999-07-22 2001-02-21 Engineering Business Ltd Plough with vibrating member positioned forward of the share
GB2353305B (en) * 1999-07-22 2003-09-17 Engineering Business Ltd Improvements to ploughs
WO2001021900A1 (en) * 1999-09-21 2001-03-29 The Engineering Business Ltd Ploughs
US6837653B1 (en) 1999-09-21 2005-01-04 The Engineering Business Ltd. Ploughs
WO2007149145A1 (en) * 2006-06-23 2007-12-27 Caterpillar Inc. System for automated excavation entry point selection
US7509198B2 (en) 2006-06-23 2009-03-24 Caterpillar Inc. System for automated excavation entry point selection
WO2017017599A1 (en) * 2015-07-28 2017-02-02 Saipem S.P.A. Trenching assembly for laying in a trench a continuous pipeline and trenching method
US10435865B2 (en) 2015-07-28 2019-10-08 Saipem S.P.A. Trenching assembly for laying in a trench a continuous pipeline and trenching method

Also Published As

Publication number Publication date
NO911296D0 (no) 1991-04-03
GB9007959D0 (en) 1990-06-06
NO911296L (no) 1991-10-08

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