METHOD AND DEVICE FOR CUTTING A POWER CABLE

A method of cutting a power cable is provided. More particularly, it is a method for cutting a power cable by means of a cable cutter which includes an actuator-controlled cutting body. A device for practising the method is provided as well.

During some operations in which a power cable is used, it may be necessary to cut the cable to avoid major damage. At sea, where a power cable is connected between a vessel and a submerged tool or apparatus, it may happen, for example, that the tool becomes stuck and that the power cable must, therefore , be cut .

Power cables of this kind are often held under relatively great tension, maybe of up to several tens of tonnes. The voltage on the cable may be for example 3.5 kV. Thus, it is unfortunate and connected with danger if the cable portion which is located on the vessel after the cutting of the power cable may freely whip back on the deck of the vessel .

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art.

The object is achieved according to the invention through the features which are specified in the description below and in the claims that follow.

A method is provided for cutting a power cable by means of a

cable cutter which is characterized by the method including the actions of:

- placing the cable cutter, including an actuator-controlled cutting body and an actuator-controlled holder body, at the power cable;

- holding the cable fixed by means of the holder body; and

- cutting the power cable by means of the cutting body.

In another aspect of the method it also includes the action of: - insulating at least the cutting body or holder body from the cutter frame of the cable cutter.

There is also provided a cable cutter for a power cable, the cable cutter including a cutter frame and an actuator- controlled cutting body connected to the cutter frame, the cable cutter being characterized by including an actuator- controlled holder body.

The actuators may be constituted by, for example, hydraulic or pneumatic cylinders, electric actuators or other actuators suitable for the purpose .

The holder bodies may be formed with mutually parallel clamping surfaces. Alternatively, the clamping surfaces may be formed to guide the cable towards the centre of the cable cutter as the holder bodies are moved towards the cable. The holder bodies may be provided with recesses so that they are arranged to be moved into being partially intermeshed.

Another aspect of the cable cutter is that at least the cutting body or the holder body is electrically insulated from the cutter frame .

A further aspect of the cable cutter is that at least the cutting body or the holder body is electrically insulated

from its respective actuator.

Yet another aspect of the cable cutter is that at least the cutting body or the holder body is electrically earthed to the surroundings .

Yet another aspect of the cable cutter is that the cable cutter is provided with guide rollers.

Yet another aspect of the cable cutter is that at least one actuator is provided with a retainer.

By the use of the method and device provided, a power cable which is under a considerable tension and relatively high voltage can be cut without there being any risk of consequential injury or damage to personnel or material. The method and the device thereby solve a long-felt problem.

In what follows is described an example of a preferred em- bodiment which is visualized in the accompanying drawings, in which:

Figure 1 shows a plan view of a cable cutter;

Figure 2 shows an end view I -I of the cable cutter of figure 1;

Figure 3 shows a plan view of the cable cutter of figure 1 in the activated position; and

Figure 4 shows an end view III-III of figure 3.

In the drawings the reference numeral 1 indicates a cable cutter which may be connected to a suspension, not shown, of a pay-out sheave on a vessel.

The cable cutter 1 includes a cutter frame 2, two cooperating cutting bodies 4 and two cooperating holder bodies 6.

The cutter frame 2 is constructed from a mounting plate 10 and two cheeks 12. The cheeks 12 project mutually parallel from the mounting plate 10 and are connected at their respective free end portions to two roller holder plates 14. The roller holder plates 14 form, together with the cheeks 12, a through opening 16, see figure 2, for a power cable 18 which extends principally parallel to the cheeks 12. The power cable 18 extends in a recess 20 in the mounting plate 10.

There are arranged two pairs of first guide rollers 22, ex- tending between the cheeks 12, and a pair of second guide rollers 24, extending between the roller holder plates 14 and standing perpendicularly to the first guide rollers 22. A pair of first guide rollers 22 and a pair of second guide rollers 24 surround the power cable 18, see figure 2.

Each of the cutting bodies 4, here in the form of knives, is movably placed between two cutting guides 26, whereas each holder body 6 is movably placed between two holder guides 28.

The cutting guides 26 and holder guides 28 are manufactured from an electrically insulating material which is connected to the cheeks 12 by means of attachments 30.

Each cutting body 4 is connected to a first actuator 32, whereas each holder body 6 is connected to a second actuator 34. The cutting bodies 4 and holder bodies 6 are movable by means of their respective actuators 32, 34 in the directions to and from the power cable 18.

In this preferred embodiment the actuators 32, 34 are formed by hydraulic cylinders with gas return. The actuators 32, 34 are thus supplied with hydraulic fluid via insulated channels, not shown, when the holder bodies 6 and cutting bodies 4 are to be moved towards the power cable 18, whereas gas pressure in the minus chamber of the actuators 32, 34 seeks

to move the holder bodies 6 and cutting bodies 4 away from the power cable 18.

The piston rods 36 of the actuators 32, 34 are otherwise electrically insulated from the actuators 32, 34.

In their inactive positions the piston rods 36 may be provided with a retainer 38 in the form of a sleeve 40 which is moved in over the piston rod 36 and a retainer bolt 42, see figure 2. The retainer bolt 42 is placed in a retainer bore 44 in the piston rode 36.

In figure 2 the holder bodies 6 and cutting bodies 4 are shown, for illustrative reasons, to have been moved out somewhat relative to the second guide rollers 24 even though the cable cutter 1 is in its inactive position. In a practical embodiment the holder bodies 6 and cutting bodies 4 will be in a position retracted within the second guide rollers 24.

When the power cable 18 extending through the cable cutter 1 is to be cut, the retainers 38 are first removed from the piston rods 36. Next the holder bodies 6 are moved up to the power cable 18 by means of the second actuators 34 and grip the power cable 18. Then the cutting bodies 4 are moved by means of the first actuators 32 up to the power cable 18 and cut it .

The holder bodies 6 prevent the end portion of the power cable 18 which is in the holder bodies 6 from being movable out of the cable cutter 1 as long as the holder bodies 6 are clamping the power cable 18.