JPH04321887A - Method for monitoring condition of long body laid on bottom of sea - Google Patents

Abstract

PURPOSE:To unite a long body and monitoring means with a guide means so that the long body can be laid even in the deep sea zone while the condition of the long body laid on the bottom of the sea is monitored, by laying the long body drawn out of a laying ship along the guide means provided on the drawing-out end with a monitoring means. CONSTITUTION:When a optical fiber cable 3 is laid on the bottom of the sea, the cable 3 is drawn out of the bow of a laying ship 1 to be inserted into respective guide rings 11a of a guide wire 11. The bottom in the neighborhood of the laid cable 3 is monitored by a marine television of a monitoring means 20 provided on the drawing-out end of the guide wire 11 so that the image signal is transmitted to an indicating means 21 on the laying ship 1. At the same time, respective sensors of the monitoring means 20 detect the height from the bottom surface and transparency in a laying site to send the detecting signals to a controlling means 22. Further, the controlling means 22 operates a hoist 10 to adjust the position of the marine television on the basis of the inputted detecting signal and take up or unwind a guide wire 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring the bottoming state of an elongated body laid on the seabed.

0002

[Prior Art] When laying long objects such as cables, water pipes, oil pipes, or gas pipes on the seabed, the long objects being laid must be properly fitted to the seabed surface without leaving the seabed. Various controls are used in the laying work, such as creating slack in the length of the cable so that it is longer than the route on the nautical chart.

[0003] In such management, for example, when the seabed area where the cable is laid is located on a relatively flat seabed topography, in addition to the slack of the elongated body, slack may be generated due to its own weight acting on the elongated body and tension due to the motion of the ship. In order to avoid certain breaks, it was sufficient to control the installation work by preventing the occurrence of kinks such as twisting during installation. Therefore, when laying such a long body on the seabed, for example, as shown in FIG.
Data such as the strength characteristics of the long body, the water depth H of the sea area where the cable will be laid, and the tidal current S are monitored on the cable laying vessel 1, and the speed at which the optical fiber cable 3 is drawn out from a cable tank (not shown) and fed out from the bow sheave 2 at the bow of the vessel is determined. By controlling the installation tension T acting on the elongated body 3 and the entry angle θ into the sea, the occurrence of kink in the optical fiber cable 3 at the bottom landing point is prevented.

0004

[Problem to be Solved by the Invention] By the way, when installing long bodies such as optical fiber cables, it is important to select a sea area with a flat seabed surface through a preliminary survey, but the seabed surface has many undulations. In some cases, it may be necessary to lay a long structure in the sea area. In such cases, it is necessary to monitor the state of the elongated body on the bottom in order to lay it so that it adapts to the undulations of the seabed and prevents excessive tension from acting on it. In this case, the diver monitors the state of the elongated body on the bottom and transmits this information to the laying vessel by wire or other means, and guides the laying vessel to an appropriate position, thereby creating a large tension on the elongated body. There is a diver-guided installation method that prevents this from occurring.

However, with the current technology, this method is limited to a water depth of about 50 m, and if it is deeper than that, for example, ROV (Remote Control
using mechanically operated devices such as
The state of the elongated body on the bottom is monitored, and any tension acting on the elongated body that exceeds the permissible limit is corrected. In this case, if the current is fast in the sea area where the long body is being laid, the ROV and the laying ship are likely to be swept away by the current. Therefore, it is difficult to keep the elongated body in an appropriate position and monitor the bottoming state of the elongated body. For this reason, when correcting the tension of a long body using a laying ship and an ROV that operate individually in such sea areas, there is a problem that the work is difficult and the correction work costs a huge amount of money. .

The present invention has been made in view of the above points, and it is possible to carry out laying work while continuously monitoring the state of the long body landing on the bottom even in deep waters, and it is possible to carry out laying work by guiding a diver in shallow waters. The purpose of this invention is to provide a method for monitoring the state of bottoming of a long body laid on the seabed, which can be expected to be as effective as the method described above.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for monitoring the bottoming state of a long submarine laying body delivered from a laying ship, which includes: The elongated body paid out from the laying ship is laid while being guided along a guide means that is paid out from the hoisting means so as to be able to be rolled up and lowered, and the laying is carried out by a monitoring means provided at the payout end of the guide means. The position of the monitoring means is determined by detecting the bottoming state of the long body laid on the seabed and the environmental conditions at the unwinding end of the guiding means, and hoisting or lowering the guiding means according to the environmental conditions detected by the monitoring means. The configuration is such that the adjustment is possible.

[0008]

[Operation] The elongated body paid out from the laying ship is laid while being guided along the guide means. At this time, the state of the elongated body being placed on the bottom is monitored by the monitoring means provided at the end of the guide means. At the same time, environmental conditions at the unwinding end are detected. Based on this information, the guide means is hoisted up or lowered, the position of the monitoring means is adjusted, and the bottoming state of the elongated body to be laid is monitored.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIG. In the following description, the same components and the like as used in the conventional method described above are given the same reference numerals. FIG. 1 shows a bottoming state monitoring device for a long body laid on the seabed that implements the method of the present invention. The monitoring device includes a hoisting winch 10 installed on a laying ship 1,
Guide wire 11 and guide wire 1 that are fed out from
1 is equipped with a monitoring means 20 provided at the feeding end.

[0010] The hoisting winch 10 is installed on the deck of the laying ship 1, and allows the guide wire 11 to be freely hoisted and lowered, and has a large hoisting load (tf). The guide wire 11 is pulled out from a cable tank (not shown) of the installation ship 1 and guides the optical fiber cable 3 that is let out from the bow of the ship, and also suspends the monitoring means 20. Guide rings 11a are provided, and the optical fiber cable 3 is laid on the seabed through these guide rings 11a.

The monitoring means 20 is an underwater television provided at the feeding end of the guide wire 11 and is equipped with illumination means, and the height from the seabed surface at the position of the monitoring means 20 provided at the feeding end of the guide wire 11 ( A height sensor and a turbidity sensor (none of which are shown) are attached to detect environmental conditions such as H) and transparency. The monitoring means 20 includes a guidewire 1
The hoisting winch 10, display means 21, and control of an electronic control unit (ECU (not shown), etc. It is electrically connected via means 22 by an umbilical cable 23 .

[0012] The underwater television uses a vidicon, which is small and easy to handle among image pickup tubes, and uses a cathode ray tube (CRT) as a display means. In addition, as a height sensor, an acoustic depth sounder using ultrasonic waves is used, but it is capable of distinguishing soft mud, sludge, etc. deposited on the seabed, for example.
Height is detected using a high frequency of about 200kHz. Further, as the turbidity sensor, a turbidity meter, a luminometer, or the like is used, which receives light emitted from a light source with a light receiver such as a photocell and measures the dissipation of the light therebetween.

In FIG. 1, reference numeral 5 denotes an anchoring wire for mooring the laying ship 1 to the laying site. The apparatus for monitoring the bottoming state of a long body laid on the seabed is configured as described above, and when the optical fiber cable 3 is laid on the seabed, the bottoming state of the optical fiber cable 3 in the vicinity of the bottoming point is monitored by the following method. At the same time, the environmental conditions at the installation site are detected and the position of the monitoring means 20 is adjusted.

First, the guide wire 1 is inserted from the bow of the laying ship 1.
The optical fiber cable 3 is inserted through each guide ring 11a of the fiber optic cable 1, and is fed out while taking a predetermined slack. Then, the optical fiber cable 3 is connected to each guide ring 11a.
The cable is fed out along the guide wire 11 while being guided by the seabed, and is continuously laid while being adapted to the seabed surface. At this time, the monitoring means 20 provided at the feeding end of the guide wire 11
Now, the underwater television monitors the vicinity of the bottom landing point of the optical fiber cable 3, transmits the video signal to the display means 21 on the ship, and displays the video.

In parallel with this, each sensor of the monitoring means 20 detects the height and transparency from the seabed surface at the installation site, and transmits these detection signals to the control means 22. Then, the control means 22 operates the hoisting winch 10 to unwind or wind up the guide wire 11 in order to adjust the position of the underwater television of the monitoring means 20 based on the signals regarding height and transparency.

[0016] In this way, in parallel with the laying of the optical fiber cable 3 unwound from the laying ship, the monitoring means 20 is adjusted to a position where it can monitor the bottoming state of the optical fiber cable 3. Furthermore, since the optical fiber cable 3 is laid while being guided by the guide wire 11, even if the installation ship 1 or the optical fiber cable 3 is washed away by a tidal current or the like, the monitoring means 20 will be able to keep track of the optical fiber cable 3 being laid. Since they move together, the optical fiber cable 3 is monitored by the monitoring means 20.
There will be no hindrance to monitoring.

In the above embodiment, an underwater television was used as the monitoring means 20 for monitoring the bottom-reaching part of the optical fiber cable 3, but if the underwater transparency is low, the optical fiber near the bottom-reaching point may be It becomes difficult to monitor cable 3. Therefore, in such a case, instead of using optical means, for example, an ultrasonic beam is irradiated near the bottoming point of the optical fiber cable 3, and the reflected ultrasonic waves are received by an acoustic lens to detect the bottoming of the cable 3. An ultrasound imaging device is used that converts the acoustic image of a point into an optical image, allowing the image to be visualized underwater.

Furthermore, in the monitoring means 20, among the environmental conditions at the feeding end of the guide cable 11, the height of the monitoring means 20 from the seabed surface is detected by a height sensor.
The depth from the sea surface may be detected by a depth sensor, or the distance from the laying ship may be detected by a distance sensor, and the position of the monitoring means 20 may be adjusted based on these.

[0019]

As is clear from the above description, according to the present invention, the long submarine laying body unwound from the laying ship is laid along the guide means provided with the monitoring means at the unwinding end. During the installation, the long submarine laying body and the monitoring means are integrated by the guide means, so there is no need to control their positions individually. For this reason, even if the tidal current in the sea area where the long seabed cable is installed is fast and the long seabed cable or the laying ship is washed away, there is no particular problem in the use of the equipment. It is possible to carry out the laying work while continuously monitoring the bottom landing status of the cable, and the same effect can be obtained as when laying the cable by guiding a diver in shallow waters.Moreover, the monitoring method is simple, so the bottom landing status monitoring device is used. It has excellent effects such as being able to provide it at a low cost.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram illustrating a method for monitoring the state of bottoming of an elongated body laid on the seabed according to the present invention.

FIG. 2 is a schematic configuration diagram illustrating a conventional method for monitoring the state of bottoming of a long body laid on the seabed.

[Explanation of symbols]

1 Laying vessel 3 Optical fiber cable (long submarine laying body) 10
Hoisting winch (hoisting means) 11 Guide cable (guiding means) 20 Monitoring means 21 Display means

Claims (1)

[Claims] 1. A method for monitoring the state of bottoming of a long body for seabed laying, which monitors the state of bottoming of a long body for seabed laying, which monitors the bottoming condition of a long body for seabed laying, which is paid out from the laying ship.
The laying is carried out while being guided along a guiding means that is freely unwound and unrolled from the hoisting means, and monitoring means provided at the unwinding end of the guiding means determines the bottoming state of the laid long body and the A seabed installation length characterized by detecting environmental conditions at the unwinding end of the guiding means, and adjusting the position of the monitoring means by hoisting or lowering the guiding means according to the environmental conditions detected by the monitoring means. A method for monitoring the bottoming state of the ulnar body.