JPS63276830A - Method of removing decomposition product in continuous crosslinking of cable - Google Patents

Abstract

PURPOSE:To prevent the outflow of a charged gas through removing products of decomposition which are remaining and floating on the surface of a coolant by providing a dam device on the boundary part between the heating section and the cooling section of a crosslinking tube, and then causing the coolant at the level of coolant to pass over the dam in a slit and flow accepting chamber. CONSTITUTION:On the boundary part between the heating section 5 and the cooling section 6 of a crosslinking tube 1 is provided a dam device 20 which is comprised of a slit 21 and a flow accepting chamber 25 surrounding the outside thereof. When a crosslinked-polyethylene- covered cable is formed in such a manner that an uncrosslinked-polyethylene-covered cable, which is caused to pass through the crosslinking tube 1 continuously, is heated and crosslinked at the heating section 5 before it is cooled at the cooling section 6, the water level is controlled by a control valve 12 so that the coolant level 10H is positioned between the lower edge and the upper edge 23 of the slit 21, and a coolant 10 is supplied continuously by means of a pump 11, and consequently, the coolant 10 becomes a flow sufficient to pass over a 'dam' and flows in the flow accepting chamber 25. Thereby, products of decomposition which are remaining and floating on the coolant level is removed so that the outflow of a charged gas can be prevented from taking place.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for removing decomposition products generated during continuous crosslinking of cables.

[Prior art] Cross-linked polyethylene coated cables are heated by running a heating section formed by filling a pressurized inert gas in the upper part of a continuous cross-linked pipe with an uncross-linked polyethylene coat extruded onto a cable core using an extruder. The uncrosslinked polyethylene extruded and coated with this extruder is low density polyethylene (LDPE). etc. contains decmir peroxide (DCP) as a crosslinking agent and an anti-aging agent, so when it runs through the heating section of the crosslinked pipe and is heated and undergoes a crosslinking reaction, the decomposition products of the crosslinking agent are methane,
Cumyl alcohol, acetophenone, α-methylstyrene, etc. are produced and gasified to fill the heating section in the crosslinked pipe.

These decomposition product gases form drains and fall to the surface of the cooling liquid, but since they are difficult to dissolve in water and have a low specific gravity, they remain suspended on the surface of the cooling liquid and impede the cooling effect. The pressurized inert gas filled in the heating section of the tube was released outside the crosslinked tube for a certain period of time, and decomposition products were discharged together with the pressurized inert gas.

[Problems to be Solved by the Invention] As mentioned above, in order to remove the decomposition products generated during crosslinking, it is only necessary to release the pressurized inert gas filled in the heating section of the crosslinked pipe outside the pipe for a certain period of time. In this case, the decomposition products filling the heating section are not sufficiently discharged, and as time passes, the amount of decomposition products that remain and float on the surface of the cooling liquid increases. For this reason, if the pressurized inert gas is continued to be released for a long time, the amount of inert gas lost increases and is not only uneconomical, but it is also difficult to control the pressure of the pressurized inert gas in the heating section to a predetermined pressure. The problem was that it became difficult.

In addition, if a drain pipe is installed at the bottom of the bridge pipe, even if you try to drain the contaminated coolant, the amount of coolant that leaks from the end seal at the end of the bridge pipe is not always constant, so it is difficult to maintain a constant water level of the coolant surface. This is extremely difficult, and if the coolant level falls below the drain pipe, not only will it be impossible to discharge the decomposition products that remain and float on the coolant level, but the pressurized inert gas from the heating section will leak out. Moreover, when the coolant level is above the drain pipe, there is a problem that decomposition products at the coolant level cannot be discharged.

Therefore, in order to prevent the decomposition products from contaminating the coolant and staying and floating on the coolant surface, the present invention provides a method to immediately remove the decomposition products that have fallen onto the coolant surface of the cooling section out of the crosslinked pipe. The present invention provides a method for removing decomposition products that allows for the removal of decomposition products.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the method for removing decomposition products during continuous cable crosslinking of the present invention reduces the cooling liquid level at the boundary between the heating section and the cooling section of the crosslinked pipe. A "weir" device consisting of a slit and a flow receiving chamber surrounding the outside of the slit is provided at the location of the slit, so that the coolant on the coolant surface flows past the "weir" of the slit, and the flow over the "weir" is By flowing the coolant into the flow receiving chamber, the decomposition products on the surface of the coolant are discharged out of the cross-linked pipe along with the flow over the "weir".

[Function] The slits provided in the bridging pipe wall at the cooling liquid surface area form a "weir" that allows the cooling liquid at the cooling liquid surface in the pipe to flow out of the pipe, and the flow receiving chamber A head is added to the flow so that a flow overflowing is formed to receive the water flow and prevent the gas filling in the heating section from flowing away.
By creating a flow over the weir, the decomposition products that remain suspended on the surface of the cooling liquid are flushed out and removed.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross-section of a continuous cross-linking device designed to remove decomposition products generated when cross-linking an uncross-linked coated cable according to the method of the present invention, and FIGS. 2 to 5 show cross-sectional views of the main parts thereof. This is what is shown.

First, in Fig. 1, 1 is a vertically installed crosslinking pipe of a vertical continuous crosslinking device, 2 is an extruder, 3 is its extrusion head,
4 is a cable delivery device, and the cable conductor A enters the extrusion head 3 through the delivery device W4, and in this extrusion head 3, low density polyethylene (LDPE) is coated with crosslinking agent decmir peroxide (DCP) and aging. A mixture of uncrosslinked polyethylene mixed with an inhibitor and the like is extruded and coated on the cable conductor A, and this uncrosslinked polyethylene coated cable B enters the crosslinked pipe 1 and travels downward to reach the heating section in the upper part of the crosslinked pipe. It is thermally cross-linked while traveling through the cooling section 5, and then is cooled while traveling through the lower cooling section 6.

The heating section 5 is equipped with a heating heater 7, and uses a pressurized inert gas such as N2 gas as a pressurizing medium, and the gas container 8 is controlled to a constant pressure with a gas pressure control valve 9.
The uncrosslinked polyethylene coated cable B is passed through the heating section 5 and heated in a pressurized atmosphere to crosslink it. Note that a pressurized inert gas or pressurized steam heated to a high temperature may be used as the heat source of the heating section 5, and the gas may be fed and filled into the pipe for heating.

Reference numeral 10 denotes a coolant such as cooling water that is being fed into the tubes of the cooling section 6, and 1ON is the surface of the coolant, which is fed into the tubes of the cooling section by a pump 11. Coolant level 1GH of this coolant 10
The water level is controlled to be constant by a cooling liquid control valve 12, and the heat-crosslinked crosslinked polyethylene coated cable runs down and is cooled in this cooling liquid 10. The cable cooled in the cooling unit 6 in this manner passes through the end seal 13 at the lower end of the bridge pipe, passes through the guide rollers 14 and the take-up device 15, and is wound up by the take-up device 16. Note that silicone oil or the like may be used as this cooling liquid.

20 is a "weir" device provided on the pipe wall at the cooling liquid level 10H at the boundary between the heating section 5 and the cooling section 6 in order to flow the cooling liquid 10 at the cooling liquid level 10H of the cooling section 6 to the outside of the bridge pipe. This "weir" device 7120 has a "notch" slit 21 that forms a "weir" as shown in FIG. and a flow receiving chamber 25 surrounding the outside thereof.

The "notch" slit 21 forming this so-called "weir" is a narrow rectangular "notch" that opens vertically in the wall of the bridge pipe at the cooling liquid level 10H at the boundary between the heating section 5 and the cooling section 6.
The slit 21, which is a vertically elongated opening, is opened so that the cooling liquid level 1011 is located between the lower edge 22 and the upper edge 23.
2 is the so-called “mine” (frest) of “cough”,
The vertical opening is cut in such a way that the cooling liquid at the cooling liquid level 1G) 1 flows out of the cross-linked pipe over the ``mine'' of the lower edge 22, creating a water flow (toward the oak) that is a so-called ``flow over a weir.''"lack"
A "weir" is formed by the slit 21. The slits 21 are provided on both sides of the pipe wall so as to face each other along the diameter line of the cross-linked pipe 1, as shown in FIG. 2 and FIG.

Note that the slit 21 of the vertically elongated opening "notch" forming this "weir" is a vertically elongated rectangular 4 as shown in the fourth figure.
Instead of forming a "corner weir", a vertically elongated inverted triangular notch 24 may be formed to form a so-called "triangular weir" as shown in FIG.
4 has its vertex 24a facing downward, below the coolant level 10H, and the upper bottom edge 24b above the coolant level 10M.

A flow receiving chamber 25 is provided outside the slit 21 forming the "weir" so as to surround the slit 21.

This flow receiving chamber 25 is formed into a sealed chamber by attaching a chamber wall 26 to the outer surface of the pipe wall of the bridge pipe 1 by welding or the like. The cooling liquid 10 flows into the flow receiving chamber 25 over the "weir" formed by the slit 21, fills the bottom, and flows out of the flow receiving chamber 25 through a pipe 28.

27 is a gas trap device connected to a pipe 28 communicating with the flow receiving chamber 25, and as shown in the second figure, a float 31 is placed on the center hole 30 of the partition plate 29, and a drainage pipe is connected to the lower end. 32 is connected, and when the coolant flows in from the flow receiving chamber 25 through the pipe 28, the float 31 floats up and flows out from the center hole 30. When the coolant does not flow in, the float 31 flows through the center hole 30. Configure to block.

As described above, in a crosslinking device in which a weir f2G is provided on the crosslinked pipe wall at the cooling liquid level 10H at the boundary between the heating part and the cold cheek part, an uncrosslinked polyethylene coated cable is continuously run inside the crosslinked pipe 1. During a continuous crosslinking operation in which a crosslinked coated cable is produced by heating crosslinking in the heating section 5 and cooling in the cooling section 6, the cooling liquid surface 10H reaches the slit 21.
The water level is controlled by the control valve 12 so that the pump 1 is located between the lower edge 22 and the upper edge 23.
At step 1, a cooling liquid 10 such as cooling water is fed into the pipe of the cooling unit 6,
By continuing to feed the coolant 10, the coolant at the coolant level 1GH flows over the "weir" of the slit 21.

When the cooling liquid is continued to be fed as described above, in FIG. 2, the cooling liquid 10 with a water head H from the "mine" of the lower edge 22 of the slit 21 to the liquid level 10H flows over the "weir" (nape) 10a. and flows down into the flow receiving chamber 25. When the flow (nape) 10a that crosses the "weir" occurs in this way, at the coolant level 1GH, the slit 21 as shown in the third figure
A flow is generated in the direction of the arrow in the direction of the arrow, and all of the coolant 10 at the liquid level 10H flows into the flow receiving chamber 25. Therefore, if there is floating matter remaining at the liquid level 10H, it will flow into the flow receiving chamber 25 together. .

When the cooling liquid that has flowed into the flow receiving chamber 25 fills the bottom thereof in this way, the pressurized inert gas filled in the heating section 5 flows through the upper half of the slit 21 and passes through the flow receiving chamber N25. Even if an attempt is made to exit the flow receiving chamber 25 through the pipe 28 connected to the lower part, the connection opening of the pipe 28 is blocked by the cooling liquid that fills the bottom, so the flow out of the flow receiving chamber 25 is prevented. be done. This lick heating section 5
Since the pressurized inert gas inside does not flow away, a predetermined pressure is maintained.

As described above, the cooling liquid flowing into the flow receiving chamber 25 and filling the bottom of the chamber enters the pipe 28 and is transferred to the gas trap device 21.
flows into. When this cooling liquid flows in, the float 31 floats up and flows out from the central hole 30. At this time, the central hole 30 is overflowing with the liquid, so the heating part 5 is transferred from the pipe 28 into the trap device 27. Even if the pressurized inert gas flows in, this flowing inert gas is prevented from flowing out through the central hole 30.

In addition, when the above-mentioned cooling liquid does not flow in, the float 31 is placed on the center hole 30 of the partition plate 29 and the center hole 30
Since the pressurized inert gas does not flow out to the outside in this case as well, the filling height of the coolant flowing into the flow receiving chamber 25 decreases and the connection opening of the pipe 28 is not blocked. Even if the pressurized inert gas from the heating section 5 enters the pipe 28, the gas trap device 27 prevents it from flowing outside, and a predetermined gas pressure is maintained. In addition, if the amount of coolant flowing into the flow receiving chamber 25 is always sufficient to fill the bottom part so that there is no risk of the pressurized inert gas flowing out from the connection opening of the pipe 28, the gas trap device 2 described above can be used.
7 can be omitted. As mentioned above, the weir device 20 is connected to the cooling liquid level 1 at the upper end of the cooling section.
When an uncrosslinked polyethylene coated cable is continuously run through the crosslinked pipe 1 and heated and crosslinked in the heating section 5 in the crosslinking device provided on the wall of the crosslinked pipe at the 0H site, decomposition products are produced during the crosslinking reaction and are turned into drains. The coolant falls onto the coolant surface 10H of the cooling unit 6, but the coolant surface 10 that receives it
The cooling liquid in 11 is formed by the slit 21.
Since the flow passes over the weir and flows into the flow receiving chamber 25, the decomposition products that remain and float on the cooling liquid surface 10H also flow into the flow receiving chamber 25 together with the flow 10a that crosses this "weir" (to the oak). The coolant and decomposition products that have flowed into the receiving chamber 25 are discharged from the pipe 28 through the gas trap device 27, so the decomposition products do not stay and float on the coolant surface 10H, and the coolant is always clean. It is maintained.

As mentioned above, in order to flow the decomposition products stagnant and floating on the cooling liquid surface 10H into the flow receiving chamber 25 together with the flow exceeding 1", the liquid level filling the bottom of this flow receiving chamber 25 and the inside of the crosslinked pipe must be It is necessary to create a head difference between the coolant level 10H and the coolant level without making it the same level, and for this reason, the "weir"
Flow receiving chamber 2 from the lower edge 22 of the slit 21
The control valve 12 is used to maintain a sufficient height D to the bottom wall 26a of the slit 21, and to maintain the coolant level 10H between the lower lI22 and the upper edge 23 of the slit 21.

As described above, in the present invention, the cooling liquid level 1GH of the cooling unit 6
A "weir" device 20 is installed on the walls of the crosslinked pipes at the position of , and a cooling liquid is supplied to create a flow that exceeds the "weir" to discharge decomposition products produced by the crosslinking reaction, The outflow amount of the flow over the "weir" can be determined as the flow rate in a so-called four-sided weir or a triangular weir.

According to the experimental results, when continuously crosslinking a 66KV to 275KV crosslinked polyethylene coated cable by the method of the present invention, a crosslinked pipe with a pipe diameter of 200 to 250φ was used and 5111ml of wI was placed at the level of the cooling liquid in the cooling section. A slit with a length of 15 m + is provided to form a "weir" and the flow rate over this "weir" is set at 10 to 30':Z1 minute to cool the surface of the cooling liquid from the "weir" of the slit while feeding the coolant. When the liquid was drained, no decomposition products remained on the surface of the coolant.

[Effects of the Invention] As described above, the present invention provides a weir device at the boundary between the heating section and the cooling section of the cross-linked pipe, so that the coolant on the coolant surface flows into the flow receiving chamber over the weir of the slit. So,
Decomposition products that remain and float on the surface of the cooling liquid can be flushed out and removed together, and the flow receiving chamber can prevent the gas filling the heating section from flowing out.

[Brief explanation of the drawing]

Fig. 1 is a drawing showing a continuous cable bridging device according to the present invention, Fig. 2 is a longitudinal cross-sectional view of the weir device, Fig. 3 is a cross-sectional view thereof, and Fig. 4 is a longitudinal cross-section taken along the line IV-IV in Fig. 2. The top view and FIG. 5 are cross-sectional views showing another embodiment of the slit.

Claims (1)

[Claims] A weir device consisting of a slit and a flow receiving chamber surrounding the outside of the slit is provided at the boundary between the heating section and the cooling section of the cross-linked pipe, and the cooling liquid on the cooling liquid surface is caused to flow over the weir of the slit and into the flow receiving chamber. A method for removing decomposition products during continuous cable cross-linking, characterized by discharging decomposition products on the surface of the cooling liquid to the outside of the cross-linked pipe together with the flow over a weir.