GB2101378A

GB2101378A - Improvements in and relating to underground installation protection systems

Info

Publication number: GB2101378A
Application number: GB08121265A
Authority: GB
Inventors: Gordon James Pill
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-07-09
Filing date: 1981-07-09
Publication date: 1983-01-12

Abstract

An underground installation protection system which comprises at least one fibre optic conductor 2 located in the ground adjacent to the said installation 1, means for transmitting one or more optical signals along the or each conductor and means for receiving the or each signal, the receiving means being arranged to detect predetermined changes in the or each signal. A plurality of conductors 2 may be laid at different distances above and on either side of the installation 1. An indication of the location of an interference may be provided. <IMAGE>

Description

SPECIFICATION Improvements in and relating to underground installation protection systems The invention relates to underground installation protection systems.

The invention provides an underground installation protection system which comprises at least one fibre optic conductor located in the ground adjacent to the said installation, means for transmitting one or more optical signals along the or each conductor and means for receiving the or each signal, the receiving means being arranged to detect predetermined changes in the or each signal.

The protection system of the invention can be used with any pipeline or cable installed underground. Interference with the fibre optic conductor, or, if there is more than one conductor, with any of them, caused by incursion, either intentional, for example for the purpose of sabotage, or unintentional, for example, during deep ploughing, post-hole boring or due to anchor drag, will cause changes in the optical signal or signals transmitted along that conductor.

Detection of these changes enables a warning to be given of impending damage to the installation, which might cause pollution of the environment or loss of supply of services. It is also possible to obtain immediate detection of damage sustained due, for example, to fire or explosion. In any case, preventative or remedial action can be taken immediately, for example, immediate shut-down of the installation. One especially advantageous application of the invention is for the protection of underwater high pressure pipelines, for example, oil pipelines, and the term "ground" is used throughout this Specification to include the seabed.

Advantageously, a series of the fibre optic conductors is provided in which the conductors are arranged at the same level as each other but at different distances from the installation. Such an arrangement can increase the probability that an incursion into the region will cause a change in one of the optical signals, and, when changes in the signals transmitted by the conductors furthest from the installation are detected, to enable a possible incursion to be detected at an early stage and monitored. Preferably, two such series of fibre optic conductors are provided, one series extending away from the installation in one direction and the other series in the opposite direction.

Alternatively, or in addition, a series of fibre optic conductors may be provided in which the conductors are arranged at different depths in the ground. Preferably, two such series of conductors are provided, the series being arranged on opposite sides of the installation.

Advantageously, the or each fibre optic conductor is divided into a series of zones, each zone being associated with a different optical signal transmitted along the conductor, and the receiving means is capable of detecting the predetermined change in any one of those signals and giving an indication of the signal in which the change has occurred. With this arrangement it is possible to achieve a more precise indication of the location along the installation of the impending or sustained damage.

The optical signals may be of wavelengths in the infra-red, visible or ultra-violet portions of the spectrum.

Four forms of underground installation protection system in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows diagrammatically a first form of the protection system of the invention; Figure 2 shows diagrammatically a second form of the protection system of the invention; Figure 3 shows diagrammatically a third form of the protection system of the invention; Figure 4 shows diagrammatically a fourth form of the protection system of the invention; and Figure 5 shows diagrammatically a portion of the protection system of the first, second, third or fourth forms of the invention.

Referring to the accompanying drawings and initially to Figure 1, an installation 1 ,for example, a high pressure oil pipeline, is located underground in the sea-bed, the surface of which is located at level G. A fibre-optic conductor 2a is located adjacent to the installation 1. The conductor 2a extends along the whole length of the installation 1, directly above it.

Another arrangement is shown in Figure 2, in which, in addition to the conductor 2a, a series of fibre optic conductors 2b,, 2b2 and 2b3 is provided in which the conductors are all located at the same level above an installation 1 as the conductor 2a and extend approximately parallel to, but at different distances from, the installation, the series being arranged along a path extending away from the installation perpendicularly to its axis. A further series of fibre optic conductors 2b4, 2b5 and 2b6 is similarly located on the opposite side of the installation.

A third arrangement is shown in Figure 3, in which a series of fibre optic conductors 2c1, 2c2 and 2c3 is provided, the conductors extending approximately parallel to the installation but being located at different depths in the ground directly below one another. A similar series of conductors 2c4, 2c5 and 2c6 is provided on the opposite side of the installation.

A fourth arrangement of fibre optic conductors, which is a combination of those shown in Figures 2 and 3, is shown in Figure 4. In this arrangement, one of the fibre optic conductors 2a is located directly above the installation 1. At the same level as the conductor 2a on each opposite side of the installation 1 extends a series of fibre optic conductors 2d, 2d2 and 2d3, and 2d4, 2d5 and 2d6, respectively. The outermost fibre optic conductors 2d3 and 2d6 form the uppermost conductors of two further series of conductors 2d3, 2d7 and 2d8, and 2d6, 2dg and 2d,0, respectively, located directly below one another at different depths in the ground on opposite sides of the installation 1.

Each of the fibre optic conductors 2, as shown in Figure 5, is connected at one end to a transmitter 3, such as a laser, arranged to transmit many different optical signals, and at the other end to a receiver 4. Each conductor 2 is divided along its length into a series of zones, zones 1 to 1 3 being indicated in Figure 5, and each zone is associated with a different one of the optical signals travelling along the conductor. The receiver 4 is arranged to detect a change in any one or more of the optical signals due to interference at some point along the conductor and indicate which signal or signals have changed so that an indication of the location of that interference can be obtained.Accordingly, the interference caused by any incursion into the region immediately surrounding the installation 1 causing changes in any of the optical signals travelling along the conductors 2 can be detected, and appropriate action taken. For example, in the arrangement shown in Figure 2, anchor drag causing a change in the optical signals first in the conductor 2b6 and then in the conductor 2b5 can be detected, the location of the impending damage to the installation 1 obtained, and, in the case of a high pressure pipeline, immediate shut down of the appropriate section of pipeline effected. Accordingly, it is possible to safe-guard against serious pollution of the environment.

United Kingdom Patent Specification No.

80.09485 claims an underground installation protection system which comprises a plurality of fibre optic conductors, at least one located in the ground adjacent to, and at a level above, the said installation and at least one located in the ground adjacent to, and at a level below, the said installation, means for transmitting optical signals along the conductors and means for receiving the signals, the receiving means being arranged to detect predetermined changes in the said signals. No claim is made herein to such a system.

Claims

1. An underground installation protection system which comprises at least one fibre optic conductor located in the ground adjacent to the said installation, means for transmitting one or more optical signals along the or each conductor and means for receiving the or each signal, the receiving means being arranged to detect predetermined changes in the or each signal.

2. A protection system as claimed in claim 1, wherein a series of the fibre optic conductors is provided in which the conductors are arranged at the same level as each other but at different distances from the installation.

3. A protection system as claimed in claim 2, wherein two such series of fibre optic conductors are provided, one series extending away from the installation in one direction and the other series in the opposite direction.

4. A protection system as claimed in any one of claims 1 to 3, wherein a series of the fibre optic conductors is provided in which the conductors are arranged at different depths in the ground.

5. A protection system as claimed in claim 4, wherein series of conductors at different depths are provided, the series being arranged on opposite sides of the installation.

6. A protection system as claimed in any one of claims 1 to 5, wherein the or each fibre optic conductor is divided into a series of zones, each zone being associated with a different optical signal transmitted along the conductor, and the receiving means is capable of detecting the predetermined change in any one of those signals and giving an indication of the signal in which the change has occurred.

7. A protection system substantially as hereinbefore described with reference to, and as shown in, any one of Figures 1 , 2, 3 or 4, in combination with Figure 5 of the accompanying drawings.

8. A method of protecting an underground installation which comprises transmitting one or more optical signals along at least one fibre optic conductor located in the ground adjacent to the said installation, receiving the or each signal from the or each conductor, and sensing predetermined changes in the or any of the signals.