A three-layer co-extrusion cross-linking air extrusion material arrangement method for long-length submarine cables

Abstract

The present invention discloses a three-layer co-extrusion cross-linked empty extrusion discharge method for a long-length submarine cable in the technical field of cross-linked polyethylene cables. The empty extrusion discharge method comprises: S1: performing screw discharge on an inner shielding extruder, an outer shielding extruder, and an insulating extruder respectively, during which the corresponding screw speeds and discharge times are controlled respectively; S2: performing die adapter discharge on an inner shielding extruder, an outer shielding extruder, and an insulating extruder respectively, during which the corresponding screw speeds and discharge times are controlled respectively, and the melting temperature is measured; S3: performing die discharge on an inner shielding extruder, an outer shielding extruder, and an insulating extruder respectively, during which the corresponding screw speeds and discharge times are controlled respectively, and the melting temperature is measured. This empty extrusion discharge method divides the discharge process into three times, and discharges are performed in sequence respectively, while limiting the control parameters of each discharge, thereby greatly improving the cleanliness of the extruder and the die, and greatly improving the operating stability.

Description

Technical Field

[0001] The invention relates to the technical field of cross-linked polyethylene cables, in particular to a three-layer co-extrusion cross-linking air extrusion material discharge method for long-length submarine cables. Background Art

[0002] In the three-layer co-extrusion cross-linking process of cross-linked polyethylene cables, a period of air extrusion discharge is usually required before the machine is officially started and the line is laid. It is divided into three stages according to the order: screw discharge, die adapter discharge, and die discharge. Air extrusion discharge has the following functions: 1. Secondary cleaning of the screw and die to prevent residual impurities and burnt materials from being brought into the cable and affecting the cable quality; 2. Verification of whether the extruder and die temperature control, extrusion status and other parameters are stable; 3. Through air extrusion discharge, the initial state of the extruded rubber and the entire cable under production can be observed, which is an important means to control cable quality.

[0003] Currently, most submarine cable manufacturers use the same air-extrusion discharge method used in the production of terrestrial cable insulation. However, terrestrial cables are typically produced in short sections of a few hundred meters or kilometers, with intermediate breaks permitted, resulting in minimal losses from unexpected downtime during production. Submarine cables, on the other hand, are typically tens or even hundreds of kilometers long and require long, continuous production. If improper process parameter control during air-extrusion discharge causes pre-crosslinking of the powder in the material, a thin film will form inside the extruder, hindering the proper shearing and propulsion of the material, preventing proper extrusion and controlling the output. Production will then be halted, forcing the machine to shut down. Furthermore, improper air-extrusion discharge control can cause the material to remain in the extruder or die for an extended period, forming charred material that can be carried through the filter screen into the cable. This can easily lead to breakdown during subsequent withstand voltage tests or under-load operation, resulting in significant economic losses.

[0004] Therefore, it is generally recognized in the industry that the production of long-length submarine cables is much more difficult than the production of land cables. The existing land cable cross-linking and air extrusion material arrangement method cannot meet the needs of long-length submarine cable production. Summary of the Invention

[0005] This application provides a three-layer co-extrusion cross-linking air extrusion discharge method for long-length submarine cables, which solves the problems of traditional air extrusion discharge method that easily lead to pre-cross-linking of materials and charring in submarine cable production. It greatly improves the cleanliness of the extruder and the head, and greatly improves the operating stability, laying a good foundation for the various challenges faced by the cross-linking production line in long-term continuous production.

[0006] The present application provides a method for discharging materials by three-layer co-extrusion cross-linking for a long-length submarine cable, which is used for a three-layer co-extrusion cross-linking device. The three-layer co-extrusion cross-linking device includes an inner shielding extruder, an outer shielding extruder, an insulation extruder, and a three-layer co-extrusion die head. The inner shielding extruder, the outer shielding extruder, and the insulation extruder are respectively connected to the three-layer co-extrusion die head through corresponding die adapters. The method comprises the following steps:

[0007] S1: Discharge the screws of the inner shield extruder, outer shield extruder, and insulation extruder respectively, as follows:

[0008] S1.1: Start the inner shield extruder, outer shield extruder, and insulation extruder respectively, and gradually adjust the screw speed from low to high. The screw speed should not exceed 2.0 rpm until the material is discharged.

[0009] S1.2: For inner shield extruder and outer shield extruder:

[0010] After discharging, gradually increase the screw speed of the inner shield extruder and the outer shield extruder to the process speed, and discharge the material at the process speed for no less than 25 minutes;

[0011] For insulation extruders:

[0012] After discharging, gradually increase the screw speed to 3-5rpm;

[0013] S1.3: The discharge time should be no less than 1 hour, and the operator should observe and inspect the softness and glossiness of the rubber material discharged from the corresponding extruder after at least 1 hour. If there are no hard knots and impurities, proceed to the next stage, otherwise continue to discharge.

[0014] S2: Discharge the die adapters of the inner shield extruder, outer shield extruder, and insulation extruder respectively, as follows:

[0015] S2.1: Start the inner shield extruder, outer shield extruder, and insulation extruder respectively, and adjust the screw speed until the discharge speed is no higher than 2 rpm;

[0016] S2.2: After the rubber materials pass through the respective filters, gradually increase the screw speed to the corresponding process speed;

[0017] S2.3: After discharging at the process speed for at least 15 minutes, measure the melt temperature using a contact temperature probe and use this to calibrate the body temperatures of the three extruders. Once the melt temperature meets the requirements, proceed to the next stage.

[0018] S2.4: Gradually reduce the screw speed of the three extruders until they stop. The speed reduction time is 3-5 minutes to avoid the sudden change in speed affecting the extruder body temperature and the state of the rubber compound.

[0019] S3: Discharging the inner shield extruder, outer shield extruder, and insulation extruder from the die head, specifically as follows:

[0020] S3.1: Start the inner shield extruder, outer shield extruder, and insulation extruder respectively, and adjust the screw speed from low to high to the process speed;

[0021] S3.2: In linkage mode, start timing from the material extrusion die sleeve at the process speed, and the discharge time shall be no less than 1 hour. During the discharge period, measure the melt temperature at the discharge point of the three-layer co-extrusion die sleeve. At this time, the melt temperature must not be higher than 130°C. At the same time, observe whether the load and extrusion pressure of the three extruders are normal. If they are normal, it is determined that the line can be turned on.

[0022] The beneficial effects of the above embodiment are: this empty extrusion discharge method divides the discharge process into three times, and discharges the materials in sequence respectively, while limiting the specific control parameters of each discharge, so that the cleanliness of the extruder and the die is greatly improved, and the operating stability is greatly improved, laying a good foundation for the various challenges faced by the cross-linking production line in long-term continuous production.

[0023] Based on the above embodiments, the present application can be further improved as follows:

[0024] In one embodiment of the present application, in step S1.2, during the speed-up process of the screws of the inner shielded extruder and the outer shielded extruder, a step-by-step climbing method is adopted, and the state speed during the speed-up period is not less than 5 rpm, and the duration of the state speed does not exceed 10 minutes.

[0025] In one embodiment of the present application, in the step S1.2, during the discharge process of the insulating extruder, the temperature of the feed zone of the insulating extruder is adjusted to 120°C.

[0026] In one embodiment of the present application, in step S2.2, during the speed-up process of the screws of the inner shielded extruder and the outer shielded extruder, a step-by-step climbing method is adopted, and the state speed during the speed-up period is not less than 5 rpm, and the duration of the state speed does not exceed 10 minutes.

[0027] In one embodiment of the present application, in step S2.2, during the speed-up process of the screw of the insulating extruder, a step-by-step climbing method is adopted, and the state speed during the speed-up period is not less than 70% of the process speed, and the duration of the state speed does not exceed 10 minutes.

[0028] In one embodiment of the present application, in step S2.2, during the discharge process of the insulating extruder, the temperature of the feed zone of the insulating extruder is adjusted to 125°C.

[0029] In one embodiment of the present application, in the step S3.1, during the speed-up process of the screws of the inner shielded extruder and the outer shielded extruder, a step-by-step climbing method is adopted, and the state speed during the speed-up period is not less than 5 rpm, and the duration of the state speed does not exceed 10 minutes.

[0030] In one embodiment of the present application, in step S3.1, during the speed-up process of the screw of the insulating extruder, a step-by-step climbing method is adopted, and the state speed during the speed-up period is not less than 70% of the process speed, and the duration of the state speed does not exceed 10 minutes.

[0031] In one embodiment of the present application, in step S3.2, the melting temperature measurement operation can be performed at least 30 minutes after discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0033] Figure 1 This is a schematic structural diagram of a three-layer co-extrusion cross-linking device in an embodiment of the present application;

[0034] Figure 2 This is a schematic flow chart of the steps of a three-layer co-extrusion cross-linking air extrusion material arrangement method for a long-length submarine cable in an embodiment of the present application;

[0035] Figure 3 A comparison chart of the failure rates of production using the hollow extrusion and discharge method in the embodiment of the present application and the conventional hollow extrusion and discharge method;

[0036] Among them, 1. Inner shield extruder, 2. Outer shield extruder, 3. Insulation extruder, 4. Inner screen die adapter, 5. Outer screen die adapter, 6. Insulation die adapter, 7. Three-layer co-extrusion die. DETAILED DESCRIPTION

[0037] The present invention will be further explained below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention made by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0039] In the description of the present invention, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine different embodiments or examples described in the present invention, as well as features of different embodiments or examples, without any contradiction.

[0040] The embodiment of the present application solves the problems of material pre-crosslinking and charring that are easily caused by the traditional air extrusion discharge method in submarine cable production by providing a three-layer co-extrusion cross-linked air extrusion discharge method for long-length submarine cables, thereby greatly improving the cleanliness of the extruder and the head and greatly improving the operating stability.

[0041] The technical solution in the embodiments of the present application is to solve the above problems, and the overall idea is as follows:

[0042] Example:

[0043] A three-layer co-extrusion cross-linking empty extrusion material discharge method for long-length submarine cables is suitable for three-layer co-extrusion cross-linking equipment, such as Figure 1 As shown, the three-layer co-extrusion cross-linking equipment includes an inner shield extruder 1, an outer shield extruder 2, an insulating extruder 3 and a three-layer co-extrusion die 7. The inner shield extruder 1, the outer shield extruder 2, and the insulating extruder 3 are connected to the three-layer co-extrusion die 7 through corresponding die adapters (inner screen die adapter 4, outer screen die adapter 5, insulating die adapter 6); Figure 2 As shown, the empty extrusion discharge method includes the following steps:

[0044] S1: Screw discharge: Screw discharge is the initial stage of empty extrusion discharge. In this stage, the inner shielded extruder, outer shielded extruder, and insulated extruder are not connected to the die adapter and the three-layer co-extrusion die. The details are as follows:

[0045] S1.1: Start the inner shield extruder, outer shield extruder, and insulation extruder respectively, and gradually adjust the screw speed from low to high. The screw speed should not exceed 2.0 rpm until the material is discharged.

[0046] S1.2: For inner shield extruder and outer shield extruder:

[0047] After discharging, gradually increase the screw speed of the inner shield extruder and the outer shield extruder to the process speed (the process speed depends on the cable product specifications, production line speed and the screw model used, and is determined according to the actual production line), and discharge at the process speed for no less than 25 minutes;

[0048] Among them, in the process of screw speed increase, a step-by-step climbing method of speed increase - maintaining the state speed for a period of time - speed increase - process speed is adopted. The step-by-step speed increase reduces the fluctuation of the extrusion state in the speed increase stage (the change of screw speed will cause the shear heat to change. If the change is too fast, the temperature of the extruder will fluctuate greatly, thereby affecting the melt temperature and extrusion quality of the extrudate); during this period, the state speed is not less than 5rpm, and the state speed duration does not exceed 10min, so as to avoid the phenomenon that the material will be pre-crosslinked due to long-term and low-speed extrusion of the extruder, which will affect normal extrusion and produce old glue and scorch.

[0049] For insulation extruders:

[0050] After discharging, gradually increase the screw speed to 3-5rpm;

[0051] During the discharge process, the temperature of the feeding zone (Z1 and Z2 zones) of the insulation extruder is adjusted to 120°C to avoid pre-crosslinking of the rubber compound due to excessive temperature at low speed.

[0052] S1.3: The discharge time should be no less than 1 hour, and the operator should observe and inspect the softness and glossiness of the rubber material discharged from the corresponding extruder after at least 1 hour. If there are no hard knots and impurities, proceed to the next stage, otherwise continue to discharge.

[0053] Among them, it should also be noted that: without installing the die adapter, the extrusion pressure cannot be increased, the material filling in the barrel is not uniform, and the screw will have the problem of uneven force. The insulating extruder screw has a large diameter and a large weight. If the speed is too fast, it will cause the "sweeping" phenomenon and the screw will shake and be damaged. Therefore, the screw speed of the insulating extruder in this step is controlled to 3-5rpm instead of the process speed in order to protect the safety of the equipment. When the insulating die adapter is subsequently installed, the extrusion pressure increases, the barrel is well filled with material, and the screw is evenly stressed, then the speed can be increased to the process speed.

[0054] S2: Die adapter discharge: Die adapter discharge is the second stage of empty extrusion discharge. In this stage, the inner shield extruder, outer shield extruder, and insulation extruder are respectively installed with corresponding die adapters (in shutdown state), but none of them are connected to the three-layer co-extrusion die. The details are as follows:

[0055] S2.1: Start the inner shield extruder, outer shield extruder, and insulation extruder respectively, and adjust the screw speed until the material is discharged at a speed not higher than 2 rpm; make the rubber material gently contact and pass through the filter placed in the head adapter to prevent the filter from being misplaced;

[0056] S2.2: After the rubber materials pass through the respective filters, gradually increase the screw speed to the corresponding process speed;

[0057] Among them, during the screw speed-up process, the above-mentioned step-by-step climbing method is also adopted. The speed of the inner shielded extruder and the outer shielded extruder in the climbing state is not less than 5 rpm, and the time does not exceed 10 minutes. The speed of the insulating extruder in the climbing state is not less than 70% of its process speed, and the time does not exceed 10 minutes.

[0058] For the insulation extruder, the temperature of the feeding zone (Z1 and Z2 zones) of the insulation extruder is adjusted to 125°C to melt and extrude the dust attached to the material as quickly as possible, preventing it from accumulating near the feed port and forming a film that can easily cause the screw to slip.

[0059] S2.3: After discharging at the process speed for at least 15 minutes, use a contact temperature probe to measure the melt temperature (the temperature of the discharged rubber material, the probe needs to be inserted into the center of the rubber material for measurement). Use this to calibrate the body temperature of the three extruders to meet the melt temperature requirements. Once the melt temperature meets the requirements, proceed to the next stage.

[0060] It should be noted that the temperature setting is based on the material melting temperature range and extruder temperature setting reference provided by the raw material manufacturer. In production, fine-tuning is required based on melt temperature measurement, extrudate stretching state, plasticization, extruder load, and other factors. The most important reference is the melt temperature. A reasonable melt temperature indicates that the extruder temperature is within a reasonable range. The extruder body is controlled by electric heating and water cooling. The temperature setting value can be changed on the operating panel or computer interface.

[0061] S2.4: Gradually reduce the screw speed of the three extruders until they stop. The speed reduction time is 3-5 minutes to avoid the sudden change in speed affecting the extruder body temperature and the state of the rubber compound.

[0062] S3: Die discharge: Die discharge is the final stage of air extrusion discharge. In this stage, the inner shield extruder, outer shield extruder, and insulation extruder (in shutdown state) are connected to the three-layer co-extrusion die respectively, as follows:

[0063] S3.1: Start the inner shield extruder, outer shield extruder, and insulation extruder respectively, and adjust the screw speed from low to high to the process speed;

[0064] Among them, during the screw speed-up process, the above-mentioned step-by-step climbing method is also adopted. The speed of the inner shielded extruder and the outer shielded extruder in the climbing state is not less than 5 rpm, and the time does not exceed 10 minutes. The speed of the insulating extruder in the climbing state is not less than 70% of its process speed, and the time does not exceed 10 minutes.

[0065] S3.2: In linkage mode, start timing from the material extrusion die sleeve at the process speed, and the discharge time shall be no less than 1 hour. During the discharge period, measure the melt temperature at the discharge point of the three-layer co-extrusion die sleeve. At this time, the melt temperature must not be higher than 130°C. At the same time, observe whether the load and extrusion pressure of the three extruders are normal. If they are normal, it is determined that the line can be turned on.

[0066] In this step, after at least 30 minutes of discharge, the discharge is considered to be in a stable state and the melting temperature can be measured. If an abnormal situation occurs, time can be saved and adjustments can be made as soon as possible.

[0067] Among them, the linkage mode means that the discharge process is automatically controlled by a computer, and the three extruders automatically match the rotation speed according to the given production line speed to match the glue output required for production.

[0068] Among them, whether the load and extrusion pressure of the three extruders are normal is judged based on the equipment parameters of the corresponding extruders.

[0069] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0070] like Figure 3 As shown in the figure, the failure rate of a submarine cable with a length of about 50 km produced by the air squeezing arrangement method of the present invention and the conventional air squeezing arrangement method is shown. It can be clearly seen that:

[0071] This empty extrusion discharge method improves the discharge process of the extruder, head adapter and three-layer co-extrusion head, divides it into multiple discharges and strictly sets the operation sequence, parameters and control methods, so that the cleanliness of the extruder and the head is greatly improved, and the operation stability is greatly improved, which provides a guarantee for the long-term continuous and uninterrupted production of long-length submarine cables, and avoids problems in the production line operation caused by improper control of discharge methods and discharge time, resulting in significant economic losses.

[0072] An embodiment of the present application also provides a three-layer co-extrusion cross-linking production method for a long-length submarine cable. The production method first requires emptying the three-layer co-extrusion cross-linking equipment according to the above-mentioned empty extrusion discharge method, and then producing according to the conventional method.

[0073] An embodiment of the present application also provides a long-length submarine cable, which is produced by the above-mentioned production method and has a length of 10km-100km.

[0074] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A three-layer co-extrusion cross-linking empty extrusion discharge method for a long-length submarine cable, used for a three-layer co-extrusion cross-linking device, the three-layer co-extrusion cross-linking device comprising an inner shielding extruder, an outer shielding extruder, an insulation extruder and a three-layer co-extrusion die head, the inner shielding extruder, the outer shielding extruder and the insulation extruder are respectively connected to the three-layer co-extrusion die head through corresponding die adapters; characterized in that The empty extrusion discharge method comprises the following steps: S1: Screw discharge is performed on the inner shield extruder, outer shield extruder, and insulation extruder respectively, as follows: S1.1: Start the inner shield extruder, outer shield extruder, and insulation extruder respectively, and gradually adjust the screw speed from low to high, and the screw speed is not higher than 2.0 rpm until the material is discharged; S1.2: For the inner shield extruder and outer shield extruder: After discharging, gradually increase the screw speed of the inner shield extruder and the outer shield extruder to the process speed, and discharge the material at the process speed for not less than 25 minutes; For the insulation extruder: After discharging, gradually increase the screw speed to 3-5rpm; S1.3: The discharge time should be no less than 1 hour from the start of discharge. The operator should observe and inspect the softness and glossiness of the rubber material discharged from the extruder after at least 1 hour. S2: Discharging the die adapters of the inner shield extruder, outer shield extruder, and insulation extruder respectively, as follows: S2.1: Start the inner shield extruder, outer shield extruder, and insulation extruder respectively, and adjust the screw speed until the discharge speed is no higher than 2 rpm; S2.2: After the rubber materials pass through the respective filters, gradually increase the screw speed to the corresponding process speed; S2.3: Measure the melt temperature at least 15 minutes after discharge at the process speed and use this temperature to calibrate the body temperatures of the three extruders. S2.4: Gradually reduce the screw speed of the three extruders until they stop. The speed reduction time is 3-5 minutes. S3: Discharging the inner shield extruder, outer shield extruder, and insulation extruder from the die head, specifically as follows: S3.1: Start the inner shield extruder, outer shield extruder, and insulation extruder respectively, and adjust the screw speed from low to high to the process speed; S3.2: In linkage mode, start timing from the material extrusion die sleeve at the process speed, and the discharge time shall be no less than 1 hour. During the discharge period, measure the melt temperature at the discharge point of the three-layer co-extrusion die sleeve. At the same time, observe whether the load and extrusion pressure of the three extruders are normal. If they are normal, it is determined that the line can be turned on.

2. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 1, characterized in that: In the step S1.2, during the speed-up process of the screws of the inner shielded extruder and the outer shielded extruder, a step-by-step climbing method is adopted, the state speed during the speed-up period is not less than 5 rpm, and the duration of the state speed does not exceed 10 minutes.

3. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 1, characterized in that: In the step S1.2, during the discharge process of the insulating extruder, the temperature of the feeding zone of the insulating extruder is adjusted to 120°C.

4. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 1, characterized in that: In the step S2.2, during the speed-up process of the screws of the inner shielded extruder and the outer shielded extruder, a step-by-step climbing method is adopted, the state speed during the speed-up period is not less than 5 rpm, and the duration of the state speed does not exceed 10 minutes.

5. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 4, characterized in that: In the step S2.2, during the speed-up process of the screw of the insulating extruder, a step-by-step climbing method is adopted, and the state speed during the speed-up period is not less than 70% of the process speed, and the duration of the state speed does not exceed 10 minutes.

6. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 3, characterized in that: In the step S2.2, during the discharge process of the insulating extruder, the temperature of the feeding zone of the insulating extruder is adjusted to 125°C.

7. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 1, characterized in that: In the step S3.1, during the speed-up process of the screws of the inner shielded extruder and the outer shielded extruder, a step-by-step climbing method is adopted, the state speed during the speed-up period is not less than 5 rpm, and the duration of the state speed does not exceed 10 minutes.

8. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 7, characterized in that: In the step S3.1, during the speed-up process of the screw of the insulating extruder, a step-by-step climbing method is adopted, and the state speed during the speed-up period is not less than 70% of the process speed, and the duration of the state speed does not exceed 10 minutes.

9. A three-layer co-extrusion and cross-linking production method for a long-length submarine cable, characterized by: The three-layer co-extrusion cross-linking production method first empties the three-layer co-extrusion cross-linking equipment according to the three-layer co-extrusion cross-linking empty extrusion discharge method according to any one of claims 1 to 8, and then performs production.

10. A long-length submarine cable, characterized by: The long-length submarine cable is produced by the three-layer co-extrusion cross-linking production method according to claim 9, and the long-length submarine cable has a length of 10 km to 100 km.

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