A heat shrink tubing sealing test piece and test method for nuclear power plants

Abstract

The present invention relates to a sealing test piece and a test method for a heat shrink sleeve for a nuclear power plant. The method is to strip the insulation layers of multiple cable cores of a section of cable to expose the core conductors; then, each cable core is respectively inserted into a corresponding perforated sleeve, so that the perforated sleeve completely covers the exposed core conductors of each cable core; the heat shrink sleeve is sleeved on the outside of the stripped cable and heat-shrunk to make the heat shrink sleeve tightly attached to the cable; the treated cable is placed in a device with a temperature, pressure and humidity equivalent to that used by the product for testing to verify the availability of the cable and the sealing performance of the heat shrink sleeve. The verification principle of the present invention is simple, and the heat shrink sleeve is fixed on a cable of a certain specification according to the requirements for relevant tests, and the safety and reliability of the use of the heat shrink sleeve are guaranteed through the test.

Description

Technical Field

[0001] The invention belongs to a sealing test technology, and in particular relates to a sealing test piece and a test method for a heat shrinkable sleeve used in a nuclear power plant. Background Art

[0002] At present, the life span of nuclear power plants at home and abroad is 40 or 60 years. The service life of cables used in nuclear power plants is required to be equivalent to the life span of nuclear power plants, and they can cope with various accident environments. The humidity environment in which the cable core is located directly affects the service life of the cable. The cable core is covered by an outer sheath, which can effectively isolate the influence of environmental humidity on the cable core. However, at both ends of the cable, in order to terminate the cable, the outer sheath of the cable needs to be stripped off. Environmental moisture often enters the cable core through the cable end, affecting the life of the cable. At present, the cable is monitored during long-term operation to determine the influence of environmental conditions on the cable, and there is no effective detection method to determine the sealing of the cable end. If the sealing of the cable end can be determined, the service life of the cable will be effectively improved.

[0003] For multi-core cables used after the accident, when the intermediate joint method is used for connection, previous projects have adopted the method of one finger sleeve corresponding to one core wire, but this connection method will take up a lot of installation space. The new nuclear power reactor type requires the use of one finger sleeve to wrap multiple cores. In this case, a method for verifying the sealing of this intermediate joint needs to be provided.

[0004] As a cable accessory, heat shrink tubing should ensure the safety of cable use. During the use of the cable, due to the poor sealing of the heat shrink tubing, moisture or corrosive substances may enter between the cable outer sheath and the core insulation layer, which will lead to the following consequences:

[0005] (1) The heat dissipation capacity of the cable is reduced, resulting in cable fires in poorly ventilated environments;

[0006] (2) The insulation layer of the cable core is corroded and damaged, causing a cable short circuit or cable fire;

[0007] (3) The service life of the cable is shortened, causing certain economic losses.

[0008] The use of heat shrink tubing with good sealing performance cannot be ignored in terms of safety and economy. At present, there is still no test or corresponding single standard for verifying the sealing performance of heat shrink tubing in the field of heat shrink tubing verification tests at home and abroad. It only relies on the cable-related immersion test to verify the electrical performance of the heat shrink tubing, thereby indirectly verifying the sealing performance of the heat shrink tubing. In the above-mentioned immersion test, the test is carried out after the cable has been protected by multi-stage heat shrinkage (including wire core heat shrinkage and outer insulation heat shrinkage), and there is no verification of the sealing performance of the heat shrink tubing under single-stage heat shrinkage (outer insulation heat shrinkage) protection. Therefore, it is necessary to develop a test to effectively verify the sealing performance of heat shrink tubing for the current and future safety and reliability of heat shrink tubing in use, and it is also beneficial to expand the scope of use of heat shrink tubing. Summary of the invention

[0009] The purpose of the present invention is to provide a sealing test piece and a test method for a heat shrink tubing for use in a nuclear power plant in view of the defects in the prior art, so as to verify whether the nuclear-grade heat shrink tubing can ensure its sealing effect in a harsh environment and ensure that the cable can adapt to more use environments, and finally further verify whether the sealing performance of the heat shrink tubing meets the use requirements of the nuclear power plant through tests in relevant regulations.

[0010] The technical solution of the present invention is as follows: a heat shrink tubing sealing test piece for a nuclear power plant, comprising a section of multi-core cable, wherein the insulation layers of multiple cable cores of the multi-core cable are stripped to expose the core conductors, a perforated sleeve is sleeved on each exposed core conductor, and the heat shrink tubing is sleeved on the outside of the stripped cable section through a heat shrinking process.

[0011] Furthermore, in the above-mentioned heat shrink sleeve sealing test piece for nuclear power plants, the length of the perforated sleeve is 1.5 to 2.5 times the length of the exposed core conductor. The size of the hole opening should ensure that when the heat shrink sleeve seal fails, a short circuit occurs between the cores. Specifically, the total area of ​​the holes is not less than 60% of the total area of ​​the perforated sleeve, the hole diameter is not less than 1 / 3 of the cross-sectional diameter of the perforated sleeve, and the thickness of the perforated sleeve is equal to the thickness of the core insulation layer.

[0012] Furthermore, the perforated sleeve is made of glass fiber.

[0013] A method for testing the sealing performance of heat shrinkable sleeves for nuclear power plants comprises the following steps: stripping the insulation layers of multiple cable cores of a section of cable to expose the core conductors; then inserting each cable core into a corresponding sleeve with holes, so that the sleeve with holes completely covers the exposed core conductors of each cable core; sleeve the heat shrinkable sleeve on the outside of the stripped cable section and perform heat shrinking operation, so that the heat shrinkable sleeve is tightly attached to the cable; and placing the treated cable in a device with a temperature, pressure and humidity equivalent to those used by the product for testing, so as to verify the availability of the cable and the sealing performance of the heat shrinkable sleeve.

[0014] Furthermore, in the above-mentioned sealing test method for heat shrink tubing for nuclear power plants, the central axis of the core conductor coincides with the central axis of the perforated tubing as much as possible.

[0015] Furthermore, in the sealing test method for heat shrink tubing for nuclear power plants as described above, the treated cable is left to stand for 24 hours and then placed in a device with a temperature, pressure and humidity equivalent to that used by the product, to simulate the environmental temperature, pressure, humidity and duration of the nuclear power plant.

[0016] Furthermore, in the above-mentioned test method for sealing of heat shrink tubing for nuclear power plants, the cable is taken out from a device with a temperature, pressure and humidity equivalent to that used by the product and placed in a normal temperature and pressure environment for a period of time, and then placed in water for 1 to 1.5 hours in accordance with the requirements of Section 5.2 of GB / T 3084.5-2007.

[0017] Furthermore, in the above-mentioned test method for sealing of heat shrink tubing for nuclear power plants, the electrical performance test of the cable is carried out and the data is recorded with reference to Section 6.2.1 of NB / T20284-2014 to verify the cable availability and the sealing performance of the heat shrink tubing.

[0018] Furthermore, in the above-mentioned method for testing the sealing performance of the heat shrink tubing for use in a nuclear power plant, the heat shrink tubing may be provided with a sealant.

[0019] Furthermore, in the above-mentioned method for testing the sealing performance of heat shrink tubing for use in nuclear power plants, the length of the cable used for the test is not less than 10 m.

[0020] The beneficial effects of the present invention are as follows: the sealing test method of the heat shrinkable tube for nuclear power plants provided by the present invention requires that water or steam cannot enter the cable through the sealing layer of the heat shrinkable tube in an extremely harsh operating environment. During the test, each cable core is charged. If the heat shrinkable tube is not well sealed, water or steam can enter the cable core through the sealing layer and the holes of the perforated glass fiber tube, causing a short circuit between the cores of the cable. The test method has a simple execution process and an easy-to-understand principle, and can fundamentally verify whether the cable availability and the sealing performance of the heat shrinkable tube meet the use requirements of the nuclear power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic diagram of the installation of the cable heat shrink sleeve in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] At present, the life span of nuclear power plants in China and even abroad is 40 or 60 years. The service life of cables used in nuclear power plants is required to be equivalent to the life span of nuclear power plants, and they can cope with various accident environments. For heat shrink tubing used in normal environments, the sealing performance can be verified by immersion tests; for heat shrink tubing used in normal and accident environments, the test is carried out in a high temperature, high pressure and high humidity environment.

[0024] The present invention is based on Figure 1 A heat shrink sleeve sealing test piece for a nuclear power plant is provided in the form of a test piece, comprising a section of multi-core cable 1, wherein the insulation layers 5 of the multiple cable cores of the multi-core cable are stripped to expose the core conductors 3, and a perforated glass fiber sleeve 4 is sleeved on each exposed core conductor 3, wherein the length of the perforated glass fiber sleeve 4 is 1.5 to 2.5 times the length of the exposed core conductor 3, and the perforated glass fiber sleeve 4 is resistant to high temperatures, has good fluidity of gaseous and liquid substances, and has good insulation properties. The perforated glass fiber sleeve 4 safely covers the core conductor 3 to ensure that the two exposed cores cannot contact. The size of the hole opening of the perforated glass fiber sleeve 4 should ensure that a short circuit occurs between the cores when the heat shrink sleeve seal fails. As a specific implementation, the total area of ​​the holes of the perforated glass fiber sleeve 4 is not less than 60% of the total area of ​​the perforated sleeve, the hole diameter is not less than 1 / 3 of the cross-sectional diameter of the perforated sleeve, and the thickness of the perforated sleeve is equal to the thickness of the core insulation layer. The heat shrinkable sleeve 2 is sleeved on the outside of the stripped cable section through a heat shrinking process.

[0025] As a specific embodiment, multi-core cables of different specifications can be selected. The length of the selected cable sample should be no less than 10m. The covering outside the cable core insulation layer 5 at both ends of each cable should be carefully stripped, and care should be taken not to damage the surface of the cable core insulation layer 5. Figure 1 As shown, the cable core insulation layer 5 is stripped 100mm away from the cable outer sheath stripping position, the stripping length is 20mm, and the core conductor 3 is completely exposed. Each cable core is inserted into a 40mm long perforated glass fiber sleeve 4, and the stripping length of the cable core insulation layer 5 is completely covered, and the central axis of the core conductor 3 is ensured to coincide with the central axis of the perforated glass fiber sleeve 4 as much as possible. Then, a heat shrink sleeve (with sealant) is inserted, and heat shrinking work is performed from the middle to both sides using special tools to ensure that the heat shrink sleeve shrinks tightly without leaving gaps.

[0026] After the above test pieces are processed, let the samples stand for 24 hours, and then put the samples into the equipment with the same temperature and pressure conditions as the product, such as the normal operating environment, temperature: 60℃, pressure: 0.1MPa(a), humidity: 100%, then soak the test pieces in 60℃ water for 24 hours. Simulate the temperature, pressure, humidity and duration of the nuclear power plant environment. After this stage is completed, place the samples in a normal temperature and pressure environment for 4 hours, and then enter the water for 1 to 1.5 hours according to the requirements of Section 5.2 of GB / T 3084.5-2007.

[0027] Finally, the electrical performance test of the samples was carried out and the data was recorded by referring to Section 6.2.1 of NB / T 20284-2014 to verify the cable availability and the sealing performance of the heat shrink tubing. Under the test environment, moisture cannot enter the cable cores through the heat shrink tubing and cause a short circuit in the cable.

[0028] After all the above tests are completed, if the test data meets the technical requirements of the standard, it means that the sealing performance of the heat shrink tubing is good and meets the requirements for use in nuclear power plants.

[0029] It will be apparent to those skilled in the art that the structure of the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0030] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A heat shrink tubing sealing test piece for a nuclear power plant, characterized in that: The invention comprises a section of multi-core cable, wherein the insulation layers of the multiple cable cores of the multi-core cable are stripped to expose the core conductors, a sleeve with holes is placed on each exposed core conductor, and the heat shrink sleeve is placed on the outside of the stripped cable section through a heat shrink process; the sleeve with holes has good insulation properties, and safely covers the core conductors to ensure that the exposed core conductors cannot be touched; the size of the hole opening of the sleeve with holes should ensure that when the seal of the heat shrink sleeve fails, a short circuit occurs between the core conductors.

2. The heat shrink tubing sealing test piece for nuclear power plant according to claim 1, characterized in that: The length of the perforated sleeve is 1.5 to 2.5 times the length of the exposed core conductor.

3. The heat shrink tubing sealing test piece for nuclear power plant according to claim 1 or 2, characterized in that: The perforated sleeve is made of glass fiber.

4. A method for testing the sealing performance of a heat shrink tubing for a nuclear power plant, characterized in that: The method is to strip the insulation layers of multiple cable cores of a section of cable to expose the core conductors; then, each cable core is respectively inserted into a corresponding perforated sleeve, so that the perforated sleeve completely covers the exposed core conductor of each cable core; a heat shrink sleeve is sleeved on the outside of the stripped cable section and a heat shrink operation is performed to make the heat shrink sleeve tightly attached to the cable; the perforated sleeve has good insulation properties, safely covers the core conductors, and ensures that the exposed core conductors cannot be contacted; the hole opening size of the perforated sleeve should ensure that when the heat shrink sleeve seal fails, a short circuit occurs between the core conductors; the treated cable is placed in a device with a temperature, pressure and humidity equivalent to those used by the product for testing, to verify the availability of the cable and the sealing performance of the heat shrink sleeve.

5. The method for testing the sealing performance of a heat shrink tubing for a nuclear power plant according to claim 4, wherein: The central axis of the core conductor coincides with the central axis of the perforated sleeve as much as possible.

6. The method for testing the sealing performance of a heat shrink tubing for a nuclear power plant according to claim 4, wherein: After the treated cable was left to stand for 24 hours, it was placed in a device with the same temperature, pressure and humidity as those used by the product to simulate the environmental temperature, pressure, humidity and duration of a nuclear power plant.

7. The method for testing the sealing performance of a heat shrink tubing for a nuclear power plant according to claim 6, characterized in that: The cable is taken out from a device with a temperature, pressure and humidity equivalent to that used by the product and placed in a normal temperature and pressure environment for a period of time, and then placed in water for 1 to 1.5 hours in accordance with the requirements of Section 5.2 of GB / T 3084.5-2007.

8. The method for testing the sealing performance of a heat shrink tubing for a nuclear power plant according to claim 7, wherein: Refer to Section 6.2.1 of NB / T20284-2014 to conduct electrical performance tests on the cables and record the data to verify the cable availability and the sealing performance of the heat shrink tubing.

9. The method for testing the sealing performance of a heat shrink tubing for a nuclear power plant according to claim 4, wherein: The heat shrinkable tube is provided with sealant.

10. The method for testing the sealing performance of a heat shrink tubing for a nuclear power plant according to claim 4, characterized in that: The length of the cable used for the test is not less than 10m.

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