GB2359103A

GB2359103A - Balanced thrust underwater excavation apparatus

Info

Publication number: GB2359103A
Application number: GB0003122A
Authority: GB
Inventors: Nicholas Victor Sills
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-02-12
Filing date: 2000-02-12
Publication date: 2001-08-15
Anticipated expiration: 2020-02-12
Also published as: GB0003122D0; GB2359103B

Abstract

An underwater excavation apparatus comprising a hollow tube 11 with propellers 17 and 18 mounted for rotation in each end of the tube to draw in water through a central inlet 12 and deliver a stream of water through opposite ends of the tube at outlets 13 and 14. One stream of water is directed at the seabed to wash away the soil in a process called hydrodynamic excavation and the other stream of water is used to counter balance the thrust force from the first stream of water. The apparatus is particularly useful for undertaking medium to large scale soil excavation operations from free flying neutrally buoyant submarine vehicles such as the so called Remotely Operated Vehicles (ROV's) commonly used in the offshore oil and gas industry for working on underwater pipelines, wellheads and structures.

Description

1 BALANCED THRUST UNDERWATER EXCAVATION APPARATUS 2359103 This invention

relates to an underwater soil excavation apparatus that can be operated from a neutrally buoyant free flying submarine vehicle in various orientations to move seabed materials without altering the stability or trim of the vehicle.

Underwater excavation apparatus using the wash from a ship's propeller deflected vertically downwards through an angled tube towards the seabed, to dig holes if stationary or trenches if moving, are well known in the marine salvage and dredging industries and commonly called propwashes. Remotely deployed forms of the apparatus have also been developed, EPC 0289520, GB 2240568, GB 22-9912, GB 2297777 and GB 23 5154 and are lowered on wires or drill string for operation near the seabed. These apparatus rely on weight to counter balance the thrust force produced by the propeller.

None of these apparatus are suitable for operation from a neutrally buoyant free flying submarine vehicle as the thrust force produced by the apparatus during operation would alter the vehicle trim and cause the vehicle to move in an uncontrolled fashion.

This invention provides an underwater excavation apparatus comprising a hollow tube having an inlet to receive water in the mid section of the hollow tube and an outlet for discharge of water at each end of the hollow tube, a propeller mounted for rotation in each end of the hollow tube to draw water through the inlet and deliver a stream of water through each outlet and reversible motor means to cause the propellers to rotate and deliver a flow of water through the first outlet for displacing materials on the seabed and the second outlet to counteract the thrust force from the first outlet and does not alter the vehicle trim or cause the vehicle to move. When the direction of rotation of both motor means is reversed the direction of the thrust forces is reversed and the flow of water through the hollow tube is reversed and the apparatus can be used to suck up materials and place them on the seabed and does not alter the trim of the vehicle or cause the 2 vehicle to move. A pivot means is provided between the apparatus and the submarine vehicle to allow the apparatus to be rotated about its central a-,zis for different uses.

In an alternative form of the invention one reversible motor is used for rotation of two propellers mounted on a common shaft. One propeller is of the controllable pitch type and can be set to full ahead or full astern position.

In a further alternative form of the invention the reversible motors and propellers are replaced by sets of single or multiple venturi means to motivate the water flow.

In a second alternative configuration the apparatus can be used to perform conventional seabed excavation with much improved speed and exerts a thrust on the submarine vehicle which must be counteracted by weight or a resistance from the seabed.

The following is a description of some of the specific embodiments of the invention, reference being to the accompanying drawings in which: -

Figure 1 is a longitudinal section through a balanced thrust underwater excavation apparatus.

Figure 2 is a front elevation drawing of a free flying neutrally buoyant submarine vehicle under way above the seabed showing the apparatus being used mounted perpendicularly on the front of the vehicle with arrows indicating the direction of water flow through the hollow tube.

Figure 3 is a front elevation drawing of a free flying neutrally buoyant submarine vehicle under way above the seabed showing the apparatus being used mounted at 45 degrees to the perpendicular on the front of the vehicle with arrows indicating the direction of water flow through the hollow tube.

3 Figure 4 is a front elevation drawing of a free flying neutrally buoyant submarine vehicle under way above the seabed showing the apparatus being used mounted at 90 degrees to the perpendicular on the front of the vehicle with arrows indicating the direction of water flow through the hollow tube.

Figure 5 is a front elevation drawing of a free flying neutrally buoyant submarine vehicle under way above the seabed showing the apparatus being used mounted at 90 degrees to the perpendicular on the front of the vehicle with arrows indicating the direction of water flow is reversed through the hollow tube.

Figure 6 is a longitudinal section through an alternative configuration of a balanced thrust underwater excavation apparatus in which a tubular sleeve is positioned over the water inlet to occlude the flow of water and the splined locking collar is withdrawn onto one shaft.

Figure 7 is a side elevation drawing of a negatively buoyant submarine vehicle crawling on the seabed showing the apparatus being used in an alternative configuration mounted perpendicularly on the back of the vehicle with arrows indicating the direction of water flow through the hollow tube.

Figure 8 is a side elevation drawing of a negatively buoyant submarine vehicle crawling on the seabed showing the apparatus being used in an alternative configuration mounted perpendicularly on the back of the vehicle with arrows indicating the direction of water flow through the hollow tube is reversed.

Drawing 1 illustrates a balanced thrust underwater excavation apparatus comprising a hollow cylindrical tube 11 having a water inlet 12 around the mid section of the tube through which water can be drawn into the tube and an outlet 13 through which water can be discharged from the tube and--- a further outlet 14 through which water can be discharged from the tube.

4 Motors 15 and 16 are mounted centrally at each end of the hollow tube for rotation of the propellers 17 and 18. The motors are mounted along the axis of the tube on sets of vanes 27 and 28 which extend radially between the motors and the inner periphery of the hollow tube. A further set of vanes 29 extend radially along the axis of the hollow tube and are attached to the inner periphery of the tube.

Shaft 19 extends from motor 15 and shaft 20 extends from motor 16 and are mounted for rotation of the propellers as indicated in figure 1.

Shaft 19 and shaft 20 are extended to align axially in the center of the apparatus as shown in figure 1 but are separated by a gap 25. The end of shaft 19 as indicated at 22 and the end of shaft 20 as indicated at 21 is splined to receive a splined locking collar 26. When in position the locking collar 26 ensures both shafts and propellers rotate at exactly the same speed and in the same direction when power is supplied to the motors.

Propeller 17 and propeller 18 are identical and symmetrical but of opposite hand, such that when both propellers rotate in the same direction they thrust away from each other with equal force or towards each other with equal force depending on the direction of rotation. Lock nuts 23 and 24 secure the propellers on the shafts.

With reference to figures 2 to 5 a sequence of events will now be described that will make the use of the apparatus apparent when mounted on a free flying neutrally buoyant submarine vehicle.

With the axis of the apparatus aligned perpendicular to the seabed as shown infigure 2, power is supplied to the motor means such that the propellers are rotated and cause a flow of water to be drawn in through the water inlet 12 around the mid section of the apparatus and expelled with equal thrust from the water outlet 14 and the water outlet 13. The wash from outlet 14 excavates the seabed below the vehicle and when the submarine vehicle is navigated across the seabed a trench 31 is formed.

With the axis of the apparatus aligned at 45 degrees to the perpendicular as shown in figure 3 the apparatus can be used to wash a mound of soil such as a trench berm 32 back into a trench in a process called backfilling.

With the axis of the apparatus aligned at 90 degrees to the perpendicular as shown in figure 4 the apparatus can be used to widen an existing trench at 33 and 34.

With reference to figure 5 a sequence of events will now be described that will make a further alternative use of the apparatus apparent.

The direction of rotation of the motors and 15 and 16 and propellers 17 and 18 is reversed to that of figures 2 to 4 so that outlet 13 and outlet 14 of figure 1 become inlet 13 and inlet 14 of figure 1 and inlet 12 of figure 1 becomes outlet 12 of figure 1. In this configuration water and seabed materials from the sides of a trench can be sucked in through inlet 13 and 14 and expelled through outlet 12 to settle out and infill a trench as shown in figure 5.

Figure 6 is a longitudinal section through an alternative configuration of a balanced thrust underwater excavation apparatus in which a tubular sleeve 30 is positioned to occlude the water inlet and the splined locking collar 26 is withdrawn onto shaft 19 so that shafts 19 and 20 are free to rotate independently.

With reference to figure 7 a sequence of events will now be described that will make the use of the apparatus arranged in the alternative configuration of figure 6 apparent when mounted on the back of a negatively buoyant submarine vehicle crawling on the seabed.

With the axis of the apparatus aligned perpendicular to the seabed power is supplied to motor and propeller means such that they are rotated in opposite directions and cause a flow of water to be drawn in through water outlet 13 and expelled through outlet 14 of figure 7. The wash from outlet 14 excavates the seabed and when the submarine vehicle is crawling across the seabed a trench is formed. The thrust force exerted on the 6 submarine vehicle is not zero and the negative buoyancy of the vehicle is used to counteract the thrust force from the apparatus.

With reference to figure 8 a sequence of events will now be described that will make a further use of the apparatus arranged in the alternative configuration of figure 6 apparent when mounted on the back of a negatively buoyant submarine vehicle crawling on the seabed.

With the axis of the apparatus aligned perpendicular to the seabed power is supplied to the motor and propeller means such that they are rotated in the reverse direction to that of figure 7 and cause a flow of water to be drawn in through water outlet 14 and expelled through outlet 13 of figure 8. The thrust force exerted on the submarine vehicle is not zero and the seabed on which the vehicle is crawling is used to counteract the thrust force from the apparatus. The suction force created around water outlet 14 draws in water and seabed materials and expels them at outlet 13 in the manner of a dredging apparatus.

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Claims

1. An underwater excavation apparatus comprising a hollow tube having an inlet to receive water, two outlets for discharge of water, a propeller mounted for rotation in each end of the hollow tube to draw water through the inlet and deliver a stream of water through each outlet and motor means to cause the propellers to rotate and deliver a flow of water through the first outlet for displacing materials on the seabed and the second outlet to counteract the thrust force from the first outlet or for displacing further materials.

An underwater excavation apparatus as claimed in claim 1, wherein the propellers mounted for rotation in each end of the hollow tube are driven by independent and reversible motor means.

2.

An underwater excavation apparatus as claimed in claims 1 and 2 wherein the propellers mounted for rotation in each end of the hollow tube are of zero camber or controllable pitch and of identical dimensions to each other but of the opposite hand.

3.

4. An underwater excavation apparatus as claimed in claims 1 to 3 wherein the shaft protruding from each motor means is extended to align and meet closely but without contact with the other shaft along the central axis of the hollow tube.

5. An underwater excavation apparatus as claimed in claims 1 to 4 wherein the end of the shaft protruding from each motor is provided with spline means.

6. An underwater excavation apparatus as claimed in claims 1 to 5 wherein a locking collar is provided with spline means and mounted on one shaft.

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7. An underwater excavation apparatus as claimed in claims 1 to 6 wherein the locking collar mounted on one shaft can be moved axially by a slide means to a central position between the two shafts and lock the rotation of the shafts together.

8. An underwater excavation apparatus as claimed in claims 1 to 7 wherein if the apparatus is operated in a vertical or inclined attitude on a free flying neutrally buoyant submarine vehicle the apparatus can be used to wash away seabed materials from below the vehicle without altering the stability or trim of the vehicle.

9. An underwater excavation apparatus as claimed in claims 1 to 8 wherein if the apparatus is operated in a horizontal attitude on a free flying neutrally buoyant submarine vehicle the apparatus can be used to wash away seabed materials from one or both sides of the vehicle without altering the stability or trim of the vehicle.

10. An underwater excavation apparatus as claimed in claim 9 wherein if the direction of the rotation of the motor and propeller means is reversed the apparatus can be used to suck seabed materials from one or both sides of the vehicle without altering the stability or trim of the vehicle.

11. An underwater excavation apparatus as claimed in claims 1 to 10 wherein a tubular sleeve is fitted over the water inlet.

12. An underwater excavation apparatus as claimed in any preceding claim wherein the direction of rotation of one motor and propeller means relative to the other is reversed so that a flow of water is produced in one direction through the hollow tube at increased the speed.

13. An underwater excavation apparatus as claimed in any preceding claim wherein if the apparatus is operated in a vertical or inclined attitude on a negatively buoyant submarine vehicle resting or crawling on the seabed it can be used to wash away 9 seabed materials if the water flow through the tube is downwards or suck up seabed materials if the water flow through the tube is upwards all with greater force.

14. An underwater excavation apparatus as claimed in any preceding claim wherein one motor is used for rotation of the two propellers mounted on a common shaft and one propeller is of the controllable pitch type and can be set to thrust ahead or astern.

15. An underwater excavation apparatus as claimed in any preceding claim wherein the underwater excavation apparatus is mounted on a pivot means to alter the attitude at which it can be operated on a submarine vehicle.

15. An underwater excavation apparatus as claimed in any preceding claim wherein the motor and propeller means are replaced by sets of single or multiple venturi means to motivate the water flow.

16. An underwater excavation apparatus as claimed in any preceding claim wherein the underwater excavation apparatus is mounted on a pivot means to alter the attitude at which it can be operated on a submarine vehicle.

k 0 Amendments to the claims have been filed as follows CLAA4S 1. An underwater excavation apparatus comprising a hollow tube having an inlet to receive water in the mid section of the hollow tube, an outlet for discharge of water at each end of the hollow tube, a propeller mounted for rotation in each end of the hollow tube to draw water through the inlet and deliver a stream of water through each outlet and reversible motor means to cause the propellers to rotate and deliver a flow of water through the first outlet for displacing materials on the seabed and the second outlet to counteract the thrust force from the first outlet and a lockable shaft means between the propellers to synchronize the speed and direction of the propellers so that when the apparatus is energized attached to a free flying neutrally buoyant underwater vehicle it does not alter the stability or trim of the vehicle.

2. An underwater excavation apparatus as claimed in claim 1, wherein the propellers mounted for rotation in each end of the hollow tube are driven by independent and reversible motor means.

3. An underwater excavation apparatus as claimed in claims 1 and 2 wherein a shaft extends from each propeller to align axially along the central axis of the hollow tube but do not touch.

4. An underwater excavation apparatus as claimed in claims 1 to 3 wherein the end of each shaft extending from each propeller is provided with spline means.

5. An underwater excavation apparatus as claimed in claims 1 to 4 wherein a locking collar is provided with spline means and mounted on one shaft.

6. An underwater excavation apparatus as claimed in claims 1 to 5 wherein the locking collar mounted on one shaft can be moved axially by a slide me= to a central position between the two shafts and lock the rotation of the shafts together.

( k 7. An underwater excavation apparatus as claimed in claims 1 to 6 wherein the propellers mounted for rotation in each end of the hollow tube are of opposite hand to each other.

9. An underwater excavation apparatus as claimed in claims 1 to 7 wherein if the apparatus is operated in a horizontal attitude on a free flying neutrally buoyant submarine vehicle the apparatus can be used to wash away seabed materials from one or both sides of the vehicle without altering the stability or trim of the vehicle.

10. An underwater excavation apparatus as claimed in claim 9 wherein if the direction of the rotation of the motor and propeller means is reversed the apparatus can be used to suck seabed materials from one or both sides of the vehicle without alterine the stability or trim of the vehicle.

An underwater excavation apparatus as claimed in claims 1 to 7 wherein a tabulai sleeve is fitted over the water inlet.

12. An underwater excavation apparatus as claimed in claims 1 to 7 wherein the direction of rotation of one motor and propeller means relative to the other is reversed so that a flow of water is produced in one direction through the hollow tube at increased speed.

13. An underwater excavation apparatus as claimed in claims 1 to 7 wherein if the apparatus is operated in a vertical or inclined attitude on a negatively buoyant submarine vehicle resting or crawling. on the seabed it can be used to wash away seabed i JL- materials if the water flow through the tube is downwards or suck up seabed materials if the water flow through- the tube is upwards all with greater force-.

14. An underwater excavation apparatus as claimed in claims 1 to 7 wherein one motor is used for rotation of the two propellers mounted on a common shaft and one propeller is of the controllable pitch type and can be set to thrust ahead or astern.