GB2529640A

GB2529640A - Bucket anchor

Info

Publication number: GB2529640A
Application number: GB1415112.0A
Authority: GB
Inventors: Angus Jamieson; Geoffrey Lock
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-08-26
Filing date: 2014-08-26
Publication date: 2016-03-02
Also published as: GB201415112D0

Abstract

A bucket anchor design comprising a plurality of joined bucket type containers that when dragged across the sea bed fills with sand, silt or clay. The bucket anchor will preferably have slots located on its sides to enable the ingress of sand and silt when the anchor system is dragged forward and digs into the sea bed. The plurality of buckets will preferably be connected via a plurality of cables which are attached from the bottom of the upper bucket to the top of the next lower bucket, with the upper bucket being attached from its upper corners via chain or cable to the main anchor chain. The anchor system will also have means for recovery via a recovery line attached to the bottom of the lowest bucket, which in turn is connected to a surface buoy.

Description

Patent Application for Bucket Anchor

DESCRIPTION

There are several types of marine anchor. They are all designed to dig into the seabed on which they are resting but, under severe conditions, they can be dragged from their position. This application proposes using several anchors of a bucket shape, attached to each other, with slots in the sides that would allow the bucket to fill with sand, silt or clay when dragged along the seabed. The buckets could fit into each other to reduce space when being transported and would be attached to each other.

Chains or suitable, flexible cables would be attached to each corner at the base of an upper bucket and be attached to the top corners of the next, lower bucket. The bucket at the top of the anchor would have its chains or cables attached to the main, anchor chain or cable, leading to the rig or other, floating vessel. At the base of the bottom bucket, there would be a single chain or flexible cable, with a buoy at its end, which would act as a marker for the position of the anchor. The chain or cable would be the recovery line. When the anchor was recovered, this line would invert the buckets, allowing their contents to fall back to the seabed.

The chains or cables between the buckets would be of sufficient length to allow space between the buckets when under pressure, as shown on the drawing. Each bucket would be designed so that, when it was initially positioned on the seabed and put under tension by the chain or cable connecting it to the oil rig it would fill with the sand, silt or clay of the seabed. If the pressure became such that it dragged, it would pull the next bucket anchor so that it filled and this process would continue until the resistance was equal to the tension. The tension will vary, depending on the height of the tide, currents, wind, etc. but the tension will not increase sufficiently to cause the bucket anchor to drag after it is positioned.

An alternative to this would be to drag all the buckets to the limit of their attachments by putting tension on the recovery line away from the rig, when they were originally placed in position. This would mean that all the buckets filled at the same time, Excessive Increases in tension would be countered by the buckets being pulled forward and filling more.

In either case, when the anchor was originally positioned, excess tension would be applied to the anchor from the rig or other floating vessel to ensure the buckets were embedded into the seabed sufficiently to prevent dragging under extreme conditions. The tension would then be reduced to the normal level.

As stated above, the force that causes an anchor to drag is around one to two hundred tonnes per anchor. Two hundred tonnes of sand has a volume of approximately sixty cubic metres, i.e. approximately 4m X 4m X4m. The drag coefficient will be about fifty percent so five buckets of three metre dimensions, all full of sand and just resting on the seabed, would have a resistance of approximately 3 X 3 X 3 X 3t/cubic metre X 5 X 50% = 202.5 tonnes. Embedding will easily double this figure.

In the event that extreme conditions occurred, such as a cyclone, the top bucket might drag if the tension became too great but, the next bucket would be dragged behind the first and automatically fill. This process would continue until the anchor buckets provided sufficient stability to equal the forces being created by the exceptional conditions and they would then maintain their position.

Claims

Patent Application for Bucket AnchorCLAIMS1. An anchor design comprising a number of connected, bucket shaped containers which fill with sand, silt or clay from the seabed when dragged along the seabed into position by tension being applied via the anchor chain or cable.
2. An anchor design comprising a number of connected, bucket shaped containers with slots in their sides that dig into the seabed to allow the container to fill with sand, silt oi clay from the seabed when dragged forward.
3. An anchor design, comprising a number of bucket shaped containers that are connected by suitable chains or cables attached from the bottom of an upper bucket to the top of the next, lower bucket, with the uppermost bucket being attached from its upper corners to chains or cables attached to the main anchor chain or cable.
4. An anchor design comprising a number of connected buckets that is recovered via a recovery line attached to the bottom of the lowest bucket that inverts the buckets, allowing their contents to fall back to the seabed.
5. An anchor system that is lighter than existing systems.