JPS6114616B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a crosslinked polyethylene cable, and is particularly aimed at increasing the manufacturing speed of the cable.

Conventionally, various methods have been proposed for shortening the crosslinking time for this purpose, but little consideration has been given to shortening the cooling time. The reason for this is that water is almost always used as a cooling medium for conventional steam and gas crosslinking, and it is not possible to lower the temperature to around 0°C or lower. Recently, a device has been proposed that uses silicone oil as the cooling medium and rapidly cools the cable using a forced circulation system equipped with a refrigerator, and this has achieved considerable effects in shortening the cooling time.

However, since this device rapidly cools the polyethylene insulator only from the outside of the cable, it is difficult to achieve uniform cooling to the inside of the insulator, which impairs the adhesion of the interface between the internal conductive layer and the semiconductive layer, resulting in the formation of voids. It may become easier. This also applies to polyethylene cables having a conductor structure having a metal pipe such as copper inside.

The present invention proposes a method that can overcome this disadvantage, by feeding a cooling medium from the winding side into the metal pipe in the cable conductor passing through the bridge tube,
This method of manufacturing a cross-linked polyethylene cable is characterized in that the feeding amount is adjusted according to the linear speed of the cable, and the medium is vaporized near the start of cooling of the cable, thereby cooling the cable from inside as well.

This will be explained in detail below with reference to the figures, which show an example of an apparatus for carrying out the method of the invention, in which a cable conductor 1 has a copper pipe 2 inside,
It starts from the delivery drum 3, passes through the capstan 4, passes through the bridging cylinder 6 directly connected to the extrusion part 5,
After crosslinking and cooling, it is sent out from the seal 7. Then, it passes through a tensioning capstan 8 and is wound onto a winding section drum 9. Sending section, winding section drums 3, 9
has a rotary joint 10, the delivery section is connected to a cooling medium tank 13 via a pump 11 and a condenser 12, and the winding section is connected to the tank 13 via a pump 14. The bridge tube 6 consists of a bridge section and a cooling section, which constitute a forced circulation system for heating and cooling media, respectively. Silicone oil is used as the heating medium, and either water or oil may be used as the cooling medium.

In the method of the present invention, the cooling medium is pumped from the tank 13 by the pump 14 into the copper tube 2 of the conductor 1 connected to the rotary joint, and in this case the cooling medium is completely vaporized at the bridging temperature. For example, freon etc. are suitable. The area near the boundary between the bridge section and the cooling section is where cooling of the cable begins. The cooling medium injected by a pump from the winding section is liquid until it reaches this point, but vaporization begins here, so the liquid turns into a humid vapor, and the heat of vaporization is transferred to the copper. The polyethylene insulation is quenched from the center through the pipe.

According to this method, the insulation is quenched simultaneously from the outside and the inside, thereby significantly shortening the cooling time and increasing the manufacturing speed of crosslinked polyethylene cables by at least 40% compared to conventional methods.

In the method of the present invention, it is necessary to keep the cooling medium in liquid form until around the time when the cable begins to be cooled. Therefore, an automatic control means is provided that can feed into the metal pipe an amount of cooling medium commensurate with the linear speed of the cable. The cooling medium vaporized in the bridge section is sent from the pump 11 to the condenser 12 via the extrusion section and the rotary joint of the delivery section, where it is condensed and stored in the tank 13.

In addition to the above, according to the method of the present invention, by simultaneously cooling the insulator from the inside and outside, the inside of the insulator is cooled evenly, so that no distortion remains and the adhesion of the interface with the semiconducting layer is improved. The effect is that the electrical characteristics of the cable can be expected to be improved due to the above reasons.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an apparatus used to carry out the method of the present invention. 1... Conductor, 2... Copper pipe, 3... Sending part drum,
4...capstan, 5...extrusion part, 6...crosslinking tube, 7
... Seal, 8... Capstan, 9... Winding section drum, 10... Rotary joint, 11, 14... Pump, 12... Capacitor, 13... Tank.

Claims (1)

[Claims] 1. A cooling medium is fed into the metal pipe inside the cable conductor passing through the bridge tube from the winding side, the amount of feeding is adjusted according to the linear speed of the cable, and the medium is vaporized near the start of cooling of the cable. A method for producing a cross-linked polyethylene cable, characterized by cooling the cable from the inside.