EP0112877B1 - Unterwassergrabenbagger - Google Patents

Unterwassergrabenbagger Download PDF

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Publication number
EP0112877B1
EP0112877B1 EP19830902110 EP83902110A EP0112877B1 EP 0112877 B1 EP0112877 B1 EP 0112877B1 EP 19830902110 EP19830902110 EP 19830902110 EP 83902110 A EP83902110 A EP 83902110A EP 0112877 B1 EP0112877 B1 EP 0112877B1
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EP
European Patent Office
Prior art keywords
sled
pipeline
trench
along
discharge
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.)
Expired
Application number
EP19830902110
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English (en)
French (fr)
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EP0112877A1 (de
Inventor
Daniel Kai Carstens
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CARSTENS, DANIEL KAI
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Individual
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Filing date
Publication date
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Publication of EP0112877A1 publication Critical patent/EP0112877A1/de
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Expired 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
    • E02F5/10—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
    • E02F5/104—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 for burying conduits or cables in trenches under water
    • E02F5/108—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 for burying conduits or cables in trenches under water using suction-effect 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
    • E02F5/104—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 for burying conduits or cables in trenches under water
    • E02F5/105—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 for burying conduits or cables in trenches under water self-propulsed units moving on the underwater bottom
    • 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
    • E02F5/104—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 for burying conduits or cables in trenches under water
    • E02F5/107—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 for burying conduits or cables in trenches under water using blowing-effect devices, e.g. jets
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/02—Travelling-gear, e.g. associated with slewing gears
    • E02F9/026—Travelling-gear, e.g. associated with slewing gears for moving on the underwater bottom

Definitions

  • This invention relates to an underwater trenching machine which will cut a trench under a pipeline and also remove the spoil from the trench to allow the pipeline to fall into the trench under its own weight.
  • Some underwater trenching machines comprise a sled which is tethered by a cable to a barge which, as it moves forwards on the surface of the sea, pulls the sled along the seabed.
  • US-A-4114390 describes one such machine in which the sled is saddle-shaped frame and is supported on the pipeline by transverse rollers, the frame comprising tubes through which water is fed under pressure to fluidizing nozzles so that the non-cohesive bottom of the seabed is fluidized and the pipeline sinks into the fluidized bottom material as the sled is pulled along the pipeline by a cable connected to a winch on the barge.
  • tractor type machines having hydraulic or electric drive, which are propelled by wheels or endless tracks in engagement with the pipeline itself (e.g. US-A-4087981) or the seabed.
  • a problem is to get enough friction between the wheels and the pipe without damaging the latter or its anti-corrosive coating, or, where the tractor drives on the seabed, for the soil to be firm enough to prevent the track sinking into the mud.
  • Another known machine described in US-A-3576111, comprises a sled which uses high pressure water jets aimed in the direction opposite to that in which the sled is to move. These jets propel the sled forward.
  • Some jets are aimed forward to cut the trench and others generally upwards to help push the spoil out of the trench, which is assisted by discharging air at the bottom of the sled.
  • the main disadvantage of this system is that in order to get a net forward thrust on the sled more water must be discharged to the rear of the sled than to the front. Also a separate air lift system is required for spoil removal. The efficiency of this type of machine is very low, and decreases with depth of operation.
  • GB-A-1479459 describes an underwater trenching machine for dredging trenches on the seabed for receiving pipes or cables comprising a sled which is towed from a supply boat by means of a tow wire attached to the sled.
  • Two pairs of downwardly directed water jet nozzles are mounted one behind the other at the forward end of the sled to loosen the material of the seabed which is then sucked up by two ejector pumps each having a suction inlet pipe of which the bottom ends are disposed aft of the water jet nozzles and below metal strips along the underside of the sled and forming a skid or runner.
  • Each suction inlet pipe which is inclined upwardly and rearwardly from its inlet end, is attached at its aft end to an angled ejector portion the aft end of which is secured to an upwardly, rearwardly and outwardly directed straight diffuser having an internal diameter increasing uniformly to the discharge aperture of the pump.
  • Jet pipes aligned with the central longitudinal axis of the respective diffusers extend through the wall of the angled ejector portions and terminate in a nozzle which faces towards the discharge aperture of the respective diffuser. Water under pressure is supplied to the jet pipes to cause the ejector pumps to suck up the loosened seabed material and discharge it to the sides of the trench through the discharge apertures of the diffusers.
  • Buoyancy tanks are provided on the sled for adjustment of the buoyancy.
  • the pipe or cable to be laid in the trench is supported by pairs of front and rear guide rollers arranged in a V-shaped formation, and is laid into the trench on leaving the rear pair of rollers.
  • the machine is such that it must be erected on the seabed. It is suggested on page 2 lines 98-103 of the description that the action of the nozzles and ejector pumps provide a reactive forward force component which can be used to propel the machine along the seabed providing the buoyancy of the machine is appropriately adjusted.
  • a pipeline of 60 cms diameter filled with water during laying can weigh several tons) in addition to the weight of the machine, and such a lifting force would increase the friction between the pipeline or cable and the pairs of supporting rollers, with an abortive result and substantial risk of damage to the pipeline or cable.
  • the frictional resistance between the skids and the seabed can only be alleviated by the lifting force imparted by the tow line to drag the skids out of and along the soil of the seabed.
  • US-A-4087981 (upon the disclosure of which the preamble of claim 1 is based) describes a buoyant self-propelled underwater trenching machine for a pipeline or cable to be laid in the seabed, comprising a sled having means for supporting it on and guiding it for movement along the pipeline or the like and comprising two side members spaced apart on opposite sides of the pipeline or the like by interconnecting transverse members including freely rotatable transverse rollers adjacent the top of the sled whereby the sled forms a kind of saddle which straddles the pipeline or the like, supported thereon by said transverse rollers and maintained in a generally upright position on the pipeline or the like by buoyancy tanks on the sled.
  • each side member comprises an upright tube equipped with a plurality of vertically arranged nozzles disposed for directing water jets at the face of the trench for breaking up soil in the forward path of the sled.
  • Each side member carries an eductor tube having its inlet adjacent the bottom of the sled and its discharge section above the top of the trench and aimed in a sideways outwards and mainly rearward direction of the sled whereby to draw up portions of the spoil broken up by said nozzles and to discharge these portions symmetrically to opposite sides of the sled.
  • the upper end of the eductor tube is provided with a venturi composed of a venturi housing in which is positioned a high pressure water nozzle.
  • the nozzle is directed towards an opening in the opposing wall of the venturi housing which is of smaller diameter than the eductor inlet to the housing and which connects with a divergent discharge tube which directs the spoil to the side of the trench.
  • Propulsion of the machine is positively derived along the pipeline by drive rollers in frictional engagement with opposite sides of the pipeline, at least one drive roller being driven by means of an electric or hydraulic motor and suitable reduction gearing.
  • Forward guide rollers which engage the sides of the pipeline in advance of the water jet nozzles at the front of each side member sense the pipeline direction and produce a torque to guide the machine on to the centerline of the pipeline.
  • the jets from the forward nozzles must be sufficiently powerful to cut away at least the upper part of the face of the trench prior to the advance of the forward guide rollers.
  • the positive driving engagement of the drive rollers with the pipeline prevents any thrust from the eductor discharges from propelling the sled forwards.
  • the sole propulsion of the machine is derived from the drive rollers. No propulsion is provided by the eductors.
  • the reduced size of the outlet from the venturi housing to the discharge section is liable to become clogged by larger pieces of spoil entering the housing through the eductor inlet, and since the discharge from the eductors takes place at a height above the top of the trench (on which the pipeline initially rests) which is approximately equal to the depth of the trench being dug, any imbalance between the sideways thrusts produced by the eductors tends to tilt the machine about the axis of the pipeline.
  • an object of this invention is to provide an underwater trenching machine and method which overcomes the above disadvantages, in which the machine is propelled solely by the means used for soil removal from the trench.
  • the invention consists in a self-propelled underwater trenching machine for a pipeline or the like to be laid, comprising a sled having means for supporting it on and guiding it for movement along the pipeline or the like and comprising two side members spaced apart on opposite sides of the pipeline or the like by interconnecting transverse members including freely rotatable transverse rollers adjacent the top of the sled whereby the sled forms a kind of saddle which straddles the pipeline or the like, supported thereon by said transverse rollers and maintained in a generally upright position on the pipeline or the like by buoyancy tanks on the sled, the front of each side member comprising a plurality of front water jets directed at the face of the trench for breaking up soil in the forward path of the sled, and each said side member carrying an educator tube comprising an upwardly extending section having an in
  • the high pressure pump jets produce suction in the eductors that lifts the mud out of the trench being cut and discharges it to the sides and rear of the trench, the water jet and spoil discharge producing a reaction on the sled in the forward direction which is used to propel the sled forwards.
  • the invention also consists in the method of underwater trenching which consists in propelling a sled along a pipeline or the like to be laid in the trench, breaking up soil in the forward path of the sled, and removing spoil from the trench as the sled advances by a pair of eductor tubes and associated water jets which produce suction at the inlets of the eductor tubes adjacent the bottom of the trench and discharge the spoil rearwardly at opposite sides of the trench respectively, characterised by using said water jets to provide a common source of power both for spoil removal and propulsion of the sled along the pipeline or the like, the forward thrust produced by the discharge of the water-spoil mixture providing the sole means for propelling the sled forwards on freely rotatable rollers mounted on the sled and resting on the pipeline.
  • the sled 1 comprises a frame formed of two loops of pipe 2,2' spaced apart in parallel upright planes by interconnecting pipes 3 to form a kind of saddle which straddles a pipeline 4 to be laid in a trench 5 cut by the sled.
  • the sled rests on the pipeline 4 by transverse rollers 6, 7, faced with rubber or other resilient material, mounted between the pairs of front and rear vertical runs of the two pipe loops respectively.
  • the sled is further transversely guided on the pipeline 4 by pairs of rollers 8, 8', 9, 9', also resiliently faced, mounted for rotation about vertical axes at the front and rear of the sled respectively on the pipe loops at opposite sides of the pipeline 4.
  • the sled also comprises two eductor tubes 10, 10' carried from the respective pipe loops 2 and 2'.
  • Each inlet connects with a vertical section 12 which leads to an elbow 13 connecting with a horizontal discharge section 14, 14' which is directed outwardly sideways and mainly rearwardly of the sled, the discharge sections 14, 14' extending symmetrically to opposite sides of the sled.
  • a nozzle 15 aimed along the respective discharge section. Water is fed to the nozzles 15 by feed pipes 16, 16' which may be interconnected so that only a single hose connection 17 is required.
  • a venturi pipe reducer 24 for example from 30 cms diameter to 25 cms diameter, corresponding to the diameters of the tube sections 12 and 14 respectively.
  • Each front vertical run of a pipe loop 2, 2' is provided with nozzles 18 to provide small jets of water aimed at the front of the trench 5. These break up the soil in front of the trenching machine. Further nozzles 19 may be provided along the bottom run of each pipe loop. High pressure water from a pump unit on a barge is supplied to the pipe loops through a hose connection 20 at the top rear end or front end of one of the pipe loops.
  • the soil loosened by the nozzles 18, 19 is removed from the trench through the eductor tubes.
  • the high pressure water streams of the water jet pumps aimed rearwardly along the discharge sections 14, 14', create suction in the eductors which lifts the spoil out of the trench 5 via their inlet ends 11 and discharges it to the side and rear of the sled through the discharge sections 14,14'.
  • the reaction of the water jet pump and the spoil propels the sled forwards and keeps it in contact with the trench face, being guided along the pipeline 4.
  • buoyancy tanks 21 At the top of the pipe loops. They also provide an uprighting force to keep the sled upright as it rides along the pipeline 4. Transverse rubber faced rollers 22, 23 may also be fitted to the machine, after it has been positioned on the pipeline, to prevent it from lifting.
  • Each tank 21 is provided with a valve in its upper part to allow air to escape, and an open pipe 21' to allow a diver to fill the tank with air after the sled is positioned on the pipeline 4 and the rollers 22, 23 locked under the pipeline.
  • the pipes 21' being open prevent the buoyancy tanks from becoming pressurised vessels.
  • the machine according to the invention has the advantage that the same power that is used for soil removal is also used for propulsion, only one power source being necessary.
  • the spoil removal pressure source does not have to be as high as that needed to cut the trench. This lowers the cost of the pumps required on the barge. Further, the water jet pump efficiency does not decrease noticeably, if at all, with increasing depth of operation. The spoil is also discharged well to the side of the trench being cut.
  • the machine may be equipped with more than one pair of eductors. If desired the spoil removal, propulsion and jetting water can be supplied through a common hose from a single pump source.
  • the hose or hoses may be connected to the front end of one or both of the pipe loops.
  • the soil at the face of the trench may be broken up by a mechanical cutter, or, by a combination of mechanical cutting means and water jets, the loosened soil being removed by the eductors and discharged outwardly and rearwardly to propel the machine forwardly and against the face of the trench being cut.
  • the rollers may be moved into or out of their operative positions by hydraulic or other power means.
  • the machine may also be used for laying cables.

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  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Sewage (AREA)
  • Electric Cable Installation (AREA)
  • Confectionery (AREA)

Claims (9)

1. Selbstfahrende Unterwasser-Grabenaushubmaschine für eine zu verlegende Rohrleitung (Pipeline) oder dergleichen, bestehend aus einem Schlitten zu deren Stützung und Führung zwecks Bewegung entlang der Rohrleitung und ferner bestehend aus zwei auf entgegengesetzten Seiten der Rohrleitung voneinander abgesetzten Seitenorgangen (2, 2') durch Verbindung von Quergliedern (3) mit frei rotierenden Querrollen (6, 7, 8, 8', 9, 9') an der Oberseite des Schlittens, wodurch der Schlitten eine Art Sattel bildet, welcher die Rohrleitung wie beim Reitsitz überspannt und darauf mittels der genannten Querrollen darauf gelagert und in einer allgemeinen aufrechten Stellung auf der Rohrleitung durch Schwimmtanks (21) auf dem Schlitten gehalten wird, wobei die Vorderseite jedes Seitenorgans eine Vielzahl von vorderen, auf die Fläche des Grabens gerichteten Wasserdüsen (18) zum Aufbrechen des Bodens in der vorwärtgsgerichteten Bahn des Schlittens aufweist und jedes Seitenorgan ein Auslaßrohr (10, 10') mit einem nach oben ragenden Teilstück (12) trägt, das einen Einlaß (11) am Boden des Schlittens aufweist und an seinem oberen Ende mit einem Ausgußteilstück (14, 14') mit Einstellung in Seiten, Auswärts- und vorwiegend Rückwärtsrichtung des Schlittens oberhalb der Oberseite des Grabens (5) verbunden ist, und längs der Achse desselben ein Wasserstrahl aus einer Düse (15) gerichtet ist, um Teile des Aushubes aufzunehmen, der von den genannten vorderseitigen Wasserstrahlen aufgebrochen wurde, und diese Aushubmassen an einder gegenüberliegenden Seiten des Schlittens auszugießen, dadurch gekennzeichnet, daß das nach oben ragende Teilstück (12) jedes Auslaßrohres (10, 10') zu einem Rohrknie (13) führt, das einen knickfreien Transport zum jeweiligen Auslaßteilstück (14, 14') gewährleistet, das sich unmittelbar oberhalb der Oberseite des Grabens befindet und im wesentlichen horizontal liegt und einen im wesentlichen gleichmässigen Durchmesser über seine gesamte Länge aufweist, wobei die zugehörigen Wasserstrahldüsen (15) in den jeweiligen Rohrknien angeordnet und entlang den zugehörigen Auslaßteilstücken ausgerichtet sind, aus denen die Wasser-Aushub-Gemische abfließen, um so das einzige Vortriebsmittel des Schlittens längs der Rohrleitung zu bilden.
2. Maschine nach Anspruch 1, gekennzeichnet durch Führungsrollen (8, 8', 9, 9'), die frei rotierend um lotrechte Achsen an der Vorder- bzw. Rückseite des Schlittens auf einander gegenüberliegenden Seiten der Rohrleitung oder dgl. angebracht sind, wobei die vorderen Führungsrollen rückwärts von den vorderen Wasserdüsen angebracht sind.
3. Maschine nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß jeder Seitenrahmen (2, 2') auch eine weitere Vielzahl von Wasserdüsen (19) entlang dem Boden jedes Seitengliedes aufweist, die nach der Sohle des Grabens hin gerichtet sind.
4. Maschine nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Seitenglieder (2, 2') zwei Rohrschleien aufweisen, die in parallelen, aufrecht stehenden Ebenen voneinander abgesetzt sind, indem die Rohre (3) so untereinander verbunden sind, daß sie die Rohrleitung reitsitzartig überspannen und sie mit frei drehbaren Querrollen (6, 7) versehen sind, um den Schlitten auf der Rohrleitung und während der Bewegung entlang derselben zu stützen, wobei die Rohrschleifen mindestens einer Einlaß (20) zum Anschluß an eine Druckwasserquelle aufweisen, während die vorderen Schleifenlängen mit Düsen (18) versehen sind, um Wasserstrahlen auf die Oberseite des Grabens zu richten, und weitere Wasserstrahldüsen (19) entlang den Bodenstrecken der Rohrschleifen vorgesehen sind.
5. Maschine nach Anspruch 4, dadurch gekennzeichnet, daß der Schlitten mit Schwimmertanks (21) oben auf den Rohrschleifen (2, 2') versehen ist, wobei jeder Tank mit einem Ventil in seinem Oberteil versehen ist, um Luft entweichen zu lassen, ferner mit einem offenen Rohr (21) in seinem unteren Teil, durch welches der Tank mit Luft gefüllt werden kann, während der Schlitten auch mit Rollen (22, 23) versehen ist, die unter der Rohrleitung untergebracht werden können, nachdem der Schlitten darauf gesetzt worden ist.
6. Maschine nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß jedes Seitenglied (2, 2') je eines aus einer Vielzahl von Paaren der genannten Auslaßrohre (10, 10') trägt, wobei die Auslaßrohre jedes Paares ihre Auslaßteilstücke (14) aufweisen, die seitwärts, auswärts und hauptsächlich rückwärts nach einander gegenüberliegenden Seiten des Schlittens gerichtet sind.
7. Verfahren zum Unterwasser-Grabenziehen, bestehend aus dem Vortreiben eines Schlittens (1) entlang einer im Graben (5) zu verlegenden Rohrleitung, Aufbrechen des Bodens in der vorwärts gerichten Bahn des Schlittens und Entfernen von Aushub aus dem Graben entsprechend dem Vorrücken des Schlittens durch ein Paar von Auslaßrohren (10, 10') und diesen zugeordneten Wasserstrahldüsen (15), die einen Saugvorgang an den Einlässen (11) der Auslaßrohre am Boden des Grabens bewirken und danach den Aushub nach rückwarts an einander gegenüberliegenden Seiten des Grabens ausschütten, dadurch gekennzeichnet, daß die Wasserstrahlen dazu benutzt werden, um eine gemeinsame Kraftquelle sowohl für die Aushubentfernung als auch für den Vortrieb des Schlittens entlang der Rohrleitung oder dergl. zu bilden, wobei der durch das Auswerfen des Wasser-Aushub-Gemisches bewirkte Vorwärtsschub das einzige Mittel zum Vorwärtstreiben des Schlittens auf frei drehbaren Rollen (6, 7; 8, 8', 9, 9') bildet, die auf dem Schlitten angebracht sind und auf der Rohrleitung ruhen.
8. Verfahren nach Anspruch 7, gekennzeichnet durch das Aufbrechen des Bodens in der vorwärts gerichteten Bahn des Schlittens, indem Wasserstrahlen auf die Oberfläche des Grabens gerichtet werden.
9. Verfahren nach Anspruch 7 oder 8, gekennzeichnet durch das Aufbrechen des Bodens unterhalb des Schlittens durch Wasserstrahlen entlang dem Boden des Schlittens.
EP19830902110 1982-06-29 1983-06-28 Unterwassergrabenbagger Expired EP0112877B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8218816 1982-06-29
GB8218816 1982-06-29

Publications (2)

Publication Number Publication Date
EP0112877A1 EP0112877A1 (de) 1984-07-11
EP0112877B1 true EP0112877B1 (de) 1986-10-01

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EP19830902110 Expired EP0112877B1 (de) 1982-06-29 1983-06-28 Unterwassergrabenbagger

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Country Link
EP (1) EP0112877B1 (de)
DE (1) DE3366582D1 (de)
DK (1) DK152549C (de)
NO (1) NO840667L (de)
WO (1) WO1984000183A1 (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5047083A (en) * 1989-06-15 1991-09-10 Nalco Chemical Company Process for de-oiling mill scale
US5125966A (en) * 1990-12-20 1992-06-30 Nalco Chemical Company Process for de-oiling mill sludge
NL9400605A (nl) * 1994-04-15 1995-11-01 Oord Acz B V Van Werkwijze en inrichting voor het onder water ingraven van een langwerpig voorwerp.
US9745716B1 (en) * 2015-12-21 2017-08-29 Michael W. N. Wilson Jet trenching system

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3576111A (en) * 1968-07-03 1971-04-27 Urban A Henry Jr Underwater pipeline-burying apparatus
US4087981A (en) * 1971-08-27 1978-05-09 Norman Offshore Services Inc. Buoyant self-propelled underwater trenching apparatus
GB1479459A (en) * 1974-11-05 1977-07-13 Mobell Ltd Underwater trenching machines and methods of excavating trenches on the sea bed
US4114390A (en) * 1976-06-28 1978-09-19 Shell Oil Company Burying a conduit in the bottom of a body of water

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Publication number Publication date
DK152549C (da) 1988-08-15
WO1984000183A1 (en) 1984-01-19
DK113084D0 (da) 1984-02-28
NO840667L (no) 1984-02-22
DK113084A (da) 1984-02-28
EP0112877A1 (de) 1984-07-11
DE3366582D1 (en) 1986-11-06
DK152549B (da) 1988-03-14

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