Three-layer co-extrusion cross-linking empty extrusion discharging method for large-length submarine cable

Abstract

The invention discloses a three-layer co-extrusion cross-linking empty extrusion discharging method of a large-length submarine cable in the technical field of cross-linked polyethylene cables, and the empty extrusion discharging method comprises the steps: S1, carrying out the screw discharging of an inner shielding extruder, an outer shielding extruder and an insulation extruder, and controlling the corresponding screw rotation speed and discharging time during the period; s2, machine head adapter discharging is carried out on the inner shielding extruder, the outer shielding extruder and the insulation extruder respectively, the corresponding screw rotating speed and discharging time are controlled respectively during discharging, and the melting temperature is measured; and S3, machine head discharging is conducted on the inner shielding extruder, the outer shielding extruder and the insulation extruder, the corresponding screw rotating speed and discharging time are controlled in the process, and the melting temperature is measured. According to the empty extrusion discharging method, the discharging process is divided into three times, discharging is conducted in sequence, meanwhile, the discharging control parameters of each time are limited, the cleanliness degree of the extruder and the machine head is greatly improved, and the operation stability is greatly improved.

Description

Technical Field

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

[0002] In the three-layer co-extrusion cross-linking process of cross-linked polyethylene cables, it is usually necessary to go through a period of empty extrusion discharge process before the official start of the machine and wiring. It is divided into three stages according to the sequence: screw discharge, die adapter discharge, and die discharge. The empty 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. Verify whether the extruder and die temperature control, extrusion status and other parameters are stable; 3. Through empty extrusion discharge, the initial state of the extruded rubber and the entire cable under the production state can be observed, which is an important means to control the cable quality.

[0003] At present, most submarine cable manufacturers use the air extrusion discharge method used in the production of land cable insulation when producing submarine cable insulation. However, land cables are usually produced in short sections of several hundred meters or kilometers, and segmentation is allowed in the middle, so the loss caused by accidental downtime during production is relatively small; while submarine cables are usually tens of kilometers or even hundreds of kilometers, requiring long-term continuous production. If the process parameters are not properly controlled during air extrusion discharge, resulting in pre-crosslinking of the powder in the material, a thin film will be formed in the extruder, hindering the normal shearing and advancement of the material, making it impossible for the extruder to extrude normally, the glue output cannot be controlled, and production cannot continue, so it can only be forced to stop; even if the air extrusion discharge is not properly controlled, the material stays in the extruder or die for too long to form charred material, which is brought into the cable through the filter screen, and is very likely to break down in subsequent pressure resistance tests or load operation, causing huge 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] The present application provides a three-layer co-extrusion cross-linking air extrusion discharge method for long-length submarine cables, thereby solving the problems of pre-cross-linking and charring of materials easily caused by traditional air extrusion discharge methods in submarine cable production. The cleanliness of the extruder and the die is greatly improved, and the operating stability is greatly improved, laying a solid foundation for the various challenges faced by the cross-linking production line in long-term continuous production.

[0006] The embodiment of the present application provides a three-layer co-extrusion cross-linking empty extrusion discharge method for a long-length submarine cable, which is used for a three-layer co-extrusion cross-linking device, wherein the three-layer co-extrusion cross-linking device comprises an inner shielding extruder, an outer shielding extruder, an insulation extruder and a three-layer co-extrusion die head, wherein 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 head adapters; the empty extrusion discharge method comprises the following steps: S1: Screw discharge of the inner shield extruder, outer shield extruder and insulation extruder is performed 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 2.0rpm until the material is discharged; S1.2: For internal shielding extruder and external shielding 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 no less than 25 minutes; For insulation extruders: After discharging, gradually increase the screw speed to 3-5rpm; S1.3: The discharge time is not less than 1 hour from the start of discharge. The operator shall observe and inspect the softness and glossiness of the rubber 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.

[0007] S2: Discharge 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 material is discharged at a speed not higher than 2rpm; S2.2: After the rubber materials pass through the respective filters, the screw speed is gradually increased to the corresponding process speed; S2.3: After discharging at the process speed for at least 15 minutes, use a contact temperature probe to measure the melt temperature and use it to calibrate the body temperature of the three extruders; when the melt temperature meets the requirements, proceed to the next stage; S2.4: Gradually reduce the screw speed of the three extruders until they stop. The speed reduction time is 3-5 minutes to avoid sudden changes in speed that affect the extruder body temperature and the state of the rubber compound.

[0008] S3: Discharging the inner shielding extruder, the outer shielding extruder and the insulating extruder from the die head, 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 1h. During the discharge, measure the melt temperature at the discharge 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 normal, it is determined that the line can be turned on.

[0009] The beneficial effects of the above embodiments are as follows: the present empty extrusion discharge method divides the discharge process into three times, and discharges the materials respectively and in turn, while limiting the specific control parameters of each discharge, thereby greatly improving the cleanliness of the extruder and the die, and greatly improving the operating stability, laying a solid foundation for the various challenges faced by the cross-linking production line in long-term continuous production.

[0010] Based on the above embodiments, the present application can be further improved as follows: In one of the embodiments of the present application, 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, 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.

[0011] In one of the embodiments 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.

[0012] In one of the embodiments of the present application, 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, 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.

[0013] In one of the embodiments of the present application, 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.

[0014] In one of the embodiments of the present application, in the 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.

[0015] In one of the embodiments 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.

[0016] In one of the embodiments of the present application, 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.

[0017] 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

[0018] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0019] Figure 1 This is a schematic diagram of the structure of a three-layer co-extrusion cross-linking device in an embodiment of the present application; Figure 2 This is a schematic diagram of the steps of a three-layer co-extrusion cross-linking air extrusion material discharge method for a long-length submarine cable in an embodiment of the present application; Figure 3 A comparison chart of the failure rates of production after using the hollow extrusion discharge method in the embodiment of the present application and using the conventional hollow extrusion discharge method; Among them, 1. Internal shield extruder, 2. External shield extruder, 3. Insulation extruder, 4. Internal screen head adapter, 5. External screen head adapter, 6. Insulation head adapter, 7. Three-layer co-extrusion head. DETAILED DESCRIPTION

[0020] The present invention is further explained below in conjunction with specific implementation methods. It should be understood that these implementation methods 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, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0021] 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, further definition and explanation thereof is not required in subsequent drawings.

[0022] 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 one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in the present invention and the features of different embodiments or examples without contradiction.

[0023] The embodiment of the present application provides a three-layer co-extrusion cross-linked air extrusion discharge method for long-length submarine cables, which solves the problems of material pre-cross-linking and charring caused by the traditional air extrusion discharge method in submarine cable production, thereby greatly improving the cleanliness of the extruder and the head and the operating stability.

[0024] The technical solution in the embodiment of the present application is to solve the above problems, and the overall idea is as follows: Example: A three-layer co-extrusion cross-linking empty extrusion material discharge method for a long-length submarine cable 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 shielding extruder 1, an outer shielding extruder 2, an insulating extruder 3 and a three-layer co-extrusion die 7. The inner shielding extruder 1, the outer shielding 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 comprises the following steps: S1: Screw discharge: Screw discharge is the initial stage of empty extrusion discharge. In this stage, the inner shield extruder, outer shield extruder, and insulation extruder are not connected to the die adapter and the three-layer co-extrusion die. The details are 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 2.0rpm until the material is discharged; S1.2: For internal shielding extruder and external shielding extruder: 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; 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, and 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 melting 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-cross-linked due to long-term and low-speed extrusion of the extruder, which will affect normal extrusion and produce old glue and scorch. For insulation extruders: After discharging, gradually increase the screw speed to 3-5rpm; During the discharge process, the temperature of the feeding zone (Z1 and Z2 zones) of the insulation extruder is adjusted to 120°C to prevent the rubber from being pre-crosslinked due to excessive temperature at low speed.

[0025] S1.3: The discharge time is not less than 1 hour from the start of discharge. The operator shall observe and inspect the softness and glossiness of the rubber 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.

[0026] Among them, it should 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 barrel" phenomenon and the screw will be damaged due to shaking. 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 materials, and the screw is evenly stressed, then the speed can be increased to the process speed.

[0027] 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: S2.1: Start the inner shield extruder, outer shield extruder and insulating extruder respectively, and adjust the screw speed until the material is discharged at a speed not higher than 2rpm; make the rubber material gently contact and pass through the filter placed in the head adapter to prevent the filter from being misplaced; S2.2: After the rubber materials pass through the respective filters, the screw speed is gradually increased to the corresponding process speed; Among them, during the screw speed-up process, the above-mentioned step-by-step climbing method is also adopted. The climbing speed of the inner shielded extruder and the outer shielded extruder is not less than 5rpm, and the time does not exceed 10min. The climbing speed of the insulating extruder is not less than 70% of its process speed, and the time does not exceed 10min.

[0028] Among them, for the insulation extruder, the temperature of the feeding zone (Z1, Z2 zone) of the insulation extruder is adjusted to 125°C to melt and extrude the dust attached to the material as soon as possible to prevent accumulation near the feed port to form a film that easily causes the screw to slip; S2.3: After discharging at the process speed for at least 15 minutes, use a contact temperature probe to measure the melt temperature (referring to the temperature of the discharged rubber material, the probe needs to be inserted into the center of the rubber material for measurement), and use this to calibrate the body temperature of the three extruders to meet the melt temperature requirements; after the melt temperature meets the requirements, proceed to the next stage.

[0029] It should be noted here 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, it is necessary to combine the melt temperature measurement, extrudate stretching state, plasticization condition, extruder load and other aspects for fine-tuning. The most important reference is the melt temperature. If the melt temperature is at a reasonable value, it means that the extruder temperature is within a reasonable range. The temperature control method of the extruder body is electric heating and water cooling. The temperature setting value can be changed on the operating panel or computer interface.

[0030] S2.4: Gradually reduce the screw speed of the three extruders until they stop. The speed reduction time is 3-5 minutes to avoid sudden changes in speed that affect the extruder body temperature and the state of the rubber compound.

[0031] S3: Die discharge: Die discharge is the final stage of empty 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: 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; Among them, during the screw speed-up process, the above-mentioned step-by-step climbing method is also adopted. The climbing speed of the inner shielded extruder and the outer shielded extruder is not less than 5rpm, and the time does not exceed 10min. The climbing speed of the insulating extruder is not less than 70% of its process speed, and the time does not exceed 10min.

[0032] 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 1h. During the discharge, measure the melt temperature at the discharge 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 normal, it is determined that the line can be turned on.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages: like Figure 3As shown in the figure, the failure rate of a submarine cable with a length of about 50 km produced by the air squeezing and discharging method of the present invention and the conventional air squeezing and discharging method is shown, from which it can be clearly seen that: This empty extrusion discharge method improves the discharge process of the extruder, the die adapter and the three-layer co-extrusion die, divides it into multiple discharges and strictly sets the operation sequence, parameters and control methods, so that the cleanliness of the extruder and the die 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 operation of the production line caused by improper control of the discharge method and discharge time, resulting in significant economic losses.

[0037] The 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.

[0038] 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.

[0039] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary 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, which is used for a three-layer co-extrusion cross-linking device, wherein the three-layer co-extrusion cross-linking device comprises an inner shielding extruder, an outer shielding extruder, an insulation extruder and a three-layer co-extrusion die head, wherein 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 head adapters; characterized in that The empty extrusion discharge method comprises the following steps: S1: Screw discharge is performed on the inner shielding extruder, the outer shielding extruder, and the insulating extruder respectively, as follows: S1.1: respectively start the inner shield extruder, the outer shield extruder, and the insulating extruder, 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 shielding extruder and the outer shielding 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 discharged from the corresponding extruder after at least 1 hour. S2: Discharging the die adapters of the inner shielding extruder, the outer shielding extruder, and the insulating extruder respectively, as follows: S2.1: start the inner shield extruder, the outer shield extruder, and the insulating extruder respectively, and adjust the screw speed until the material is discharged at a speed not higher than 2 rpm; S2.2: After the rubber materials pass through the respective filters, the screw speed is gradually increased to the corresponding process speed; S2.3: Measure the melt temperature at least 15 min after discharge at the process speed and use it to calibrate the body temperature of the three extruders; S2.4: Gradually reduce the screw speed of the three extruders until they stop, and the speed reduction time is 3-5 minutes; S3: Discharging the inner shielding extruder, the outer shielding extruder and the insulating extruder from the die head, 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 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 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 is 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, 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.

3. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 1 is 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 is 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, 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.

5. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 4 is 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 is characterized in that: In the 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.

7. The three-layer co-extrusion cross-linking air extrusion discharge method according to claim 1 is 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, 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.

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

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

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