JPS63308808A - Power cable - Google Patents

Abstract

PURPOSE:To obtain a cable which is excellent in mechanical strength and corrosion resistance by using pure Ti for metallic sheath. CONSTITUTION:A pure Ti tape 2 is sent out along a cable core 1 and formed into cylindrical shape so as to wrap a core. The tape joint is welded by MIG or TIG in inert gas. For Ti, pure Ti in the second class or third class of JIS standard is used. The tape thickness shall be about 0.5-1mm. Waving is performed by a corrugator after welding. For waving, the pitch is made at about 10mm and the height is about 5mm. Lastly, a corrosion resistant layer 3 of about 5mm in thickness is extruded to coat. According to this constitution, a cable excellent in mechanical strength and corrosion resistance can be obtained and since longitudinal elastic coefficient and line expansion coefficient are small, the bending characteristic of the cable is improved and it is hard to extend to the temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a power cable having a metal sheath outside the cable core.

(Prior Art and Problems to be Solved) FIG. 1 is a cross-sectional view of an example of a power cable having a metal sheath on the outside of the cable core, and FIG. 2 is a vertical cross-sectional view of the power cable of FIG. 1. As shown in the drawing, a corrugated metal sheath (2) is provided on the outer periphery of a cable core such as an oil-impregnated paper insulated cable core or a cross-linked polyethylene insulated cable core, and a corrugated metal sheath (2) is provided on the outer periphery of the cable core, such as an oil-impregnated paper insulated cable core or a cross-linked polyethylene insulated cable core. It is constructed by providing an anti-corrosion layer (3) such as polyethylene.

Conventionally, lead and aluminum have been mainly used as metal sheaths for power cables. Recently, stainless steel has also started to be used. However, each of these metal sheaths has the following problems.

In other words, the lead sheath is highly flexible and has excellent corrosion resistance, so there is no need to corrugate it as shown in the drawing, but its mechanical strength is weak, and if the pressure inside the cable is high, It is necessary to separately provide some kind of reinforcing layer, such as wrapping a reinforcing tape such as stainless steel tape.

Although aluminum sheaths have excellent mechanical strength, they have poor corrosion resistance when used under conditions such as being installed underground or under electric fields. Therefore, it is necessary to provide a corrosion protection layer such as polyvinyl chloride or polyethylene on the aluminum sheaths. .

Stainless steel sheaths have excellent mechanical strength and corrosion resistance. However, its elastic modulus is as large as that of iron, its elongation is poor, and its corrosion resistance is incomplete, as pitting occurs in an atmosphere where chlorine ions are present.

(Disclosure of the Invention) The present invention provides a power cable having a metal sheath that solves the problems of the conventional metal sheath described above, and is characterized in that the metal sheath is made of pure titanium.

In the present invention, pure titanium is used as the metal sheath for the following reasons.

■Excellent mechanical strength. In other words, the tensile strength is lower than stainless steel, but it is about 4 times higher than aluminum.
A general-purpose iron material is sufficient.

■Low modulus of longitudinal elasticity. The modulus of longitudinal elasticity is approximately 1 that of stainless steel.
72, which is extremely important. In other words, stainless steel is mechanically strong, but has a large elastic modulus, is hard, and difficult to stretch. On the other hand, pure titanium has a tensile strength equivalent to that of general-purpose iron, and at the same time, its softness is close to that of aluminum, combining the good aspects of stainless steel and aluminum. Easy to stretch due to its small longitudinal elastic modulus. Therefore, when used as a cable sheath, it becomes easily bendable.

■Excellent corrosion resistance. Aluminum and stainless steel have problems with corrosion resistance as mentioned above, but pure titanium has excellent corrosion resistance, as it is used in various piping at nuclear power plants and in aircraft.

■The weight of the cable can be reduced. That is, the specific gravity of pure titanium is about 4.5, which is about half that of stainless steel, which is 7.9.

■The coefficient of linear expansion is smaller than any of the conventional sheath materials. This means that the metal source of the cable has a favorable tendency to be difficult to stretch due to temperature changes.

For reference, Table 1 shows a comparison of the mechanical properties of aluminum, stainless steel, and pure titanium.

Table 1 Next, the method for forming the metal sheath in the power cable of the present invention will be explained.

■First, we send out a long piece of pure titanium tape along the cable core, form it into a cylindrical shape, and wrap it around the cable core. Then, the joints of the tapes are welded by MIG or TIG in an inert gas atmosphere. There are two types of titanium: pure titanium and alloyed titanium.
Pure titanium of standard type 2 or 3 is used. The thickness of the pure titanium tape must be selected depending on the type and size of the electrical cable, but a thickness of about 0.5 to 1.1 is usually sufficient.

■After welding, apply corrugations using a corrugator.

The purpose of this is to improve the bending performance of the cable. If the metal sheath is thick enough, the metal sheath will not locally flatten during bending, which is the so-called buckling phenomenon. However, in the case of thin-walled pipes such as those mentioned above, corrugation is recommended to avoid this. is desirable. The shape of the wave is usually pitch=IO so 1 and height about 51.

■On top of that, an anti-corrosion layer of about 51-mm is extruded and coated to prevent electrolytic corrosion in the soil and corrosion caused by chemicals.As mentioned above, according to the electric cable of the present invention, pure titanium is used as the metal sheath. , it has excellent mechanical strength and corrosion resistance, and can reduce the weight of the cable.

Furthermore, since the longitudinal elastic modulus and linear expansion coefficient are small, the bending characteristics of the cable are improved, and the cable has advantages such as being resistant to stretching due to temperature changes.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of an electric cable having a metal sheath on the outside of the cable core, and FIG. 2 is a longitudinal cross-sectional view of the electric cable shown in FIG. 1. 1... Cable core, 2... Corrugated metal sheath, 3...
...Anti-corrosion layer. dice j calculation 2 diagram

Claims (1)

[Claims] (1) A power cable having a metal sheath on the outside of a cable core, wherein the metal sheath is a pure titanium sheath.