CN106644908B - Method and device for evaluating durability of cable and protective sleeve in damp and hot environment - Google Patents
Method and device for evaluating durability of cable and protective sleeve in damp and hot environment Download PDFInfo
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- CN106644908B CN106644908B CN201611075661.6A CN201611075661A CN106644908B CN 106644908 B CN106644908 B CN 106644908B CN 201611075661 A CN201611075661 A CN 201611075661A CN 106644908 B CN106644908 B CN 106644908B
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Abstract
The invention provides a method for evaluating the durability of a cable and a protective sleeve in a damp and hot environment, which comprises the following steps: (1) cutting a cable with the length of 20-30mm, and wrapping the cable with a protective sleeve to prepare a sample; (2) adding deionized water into a high-pressure container, placing a sample on a grid above the water surface, controlling the temperature in the container to be 95-125 ℃, and controlling the pressure in the container to be 0.10-0.20 MPa; (3) and maintaining the sample in a high-pressure container at high temperature and high pressure for 40-60 hours, and taking out for testing. The method can test the chemical reaction generated in the damp-heat environment of the cable and the protective sleeve, test the matching stability of the cable and the protective sleeve, is convenient and efficient, can be operated by an operator without professional knowledge or special training, and is cheap and easy to obtain instruments and equipment.
Description
Technical Field
The invention belongs to the technical field of cables, and particularly relates to a method and a device for evaluating the durability of a cable and a protective sleeve in a hot and humid environment.
Background
The damp-heat aging test is suitable for products which can be used in warm and humid environments, namely warm and humid environments in tropical regions with seasons of different lengths throughout the year and in mid-latitude regions. The purpose of the test was to examine the product's ability to adapt to warm and humid environments. In plastic materials, porous materials or finished products, various materials have different physical reactions to temperature and moisture, the effect of temperature is mostly plastic deformation or over-temperature or poor low-temperature start of products, etc., the porous materials can cause surface moisture adsorption, infiltration, condensation and other situations due to capillary effect in a humidity environment, and the products can cause failure due to static charge accumulation effect in a low-humidity environment. The common humidity effect is as follows: loss of physical strength, change in chemical properties, degradation of insulating material properties, electrical shorts, oxidative corrosion of metallic materials, loss of plasticity, accelerated chemical reactions, degradation of electronic components, and the like. The damp-heat test is mainly used for the adaptability of instrument and meter materials, electricians, electronic products, household appliances, automobile and motorcycle accessories, chemical coatings, aerospace products and other related product parts to warm and humid environments during storage, transportation and use in high-low temperature damp-heat environments.
The damp-heat aging test is a manual simulated environment test, and damp-heat atmosphere generated by damp-heat test equipment simulates damp-heat environment which a product may encounter in the processes of storage, transportation and use so as to check the weather resistance of the product. The artificial accelerated humid and heat aging generally adopts a constant temperature and humidity test method and an alternating temperature and humidity circulation test method. The damp-heat aging test has an acceleration effect besides the manual simulation of damp-heat environment, can greatly shorten the test time, and has a test result similar to that of a field exposure test.
According to the national damp-heat aging test method, the material is exposed to a damp and hot air environment, performance change can occur after the material is subjected to damp-heat action, and the damp-heat resistance of the material is evaluated by measuring some performance or appearance change before and after the material is exposed under a specified environment condition.
Cables are made of one or more mutually insulated conductors and an outer insulating sheath that carries power or information from one point to another. During the use process, the cable is often used together with a protective sleeve. During the use of the cable, particularly under the damp and hot conditions, accidents such as corrosion, spot generation on the surface, short circuit and the like often occur, and the corrosion is caused in part by the following reasons: the flame retardant additive in the mesh tube is separated out under certain temperature and humidity conditions, is adhered to the surface of the cable, and is dissolved in water and hydrolyzed to generate acid (radical). The cable is filled with a large amount of magnesium hydroxide or aluminum hydroxide, the magnesium hydroxide/aluminum hydroxide is difficult to dissolve in water but easy to dissolve in dilute acid, and under the catalysis of phosphate radicals and the like, the magnesium hydroxide/aluminum hydroxide can be dissolved out of the cable by the water adsorbed by the protective sleeve and reacts to generate white phosphate, so that the cable is corroded.
The existing testing standard for the cable damp and hot environment is EN60068-2-78, the testing conditions are that the temperature is 90 ℃, the humidity is 85%, and the testing time is 1000 hours, but the testing time of the standard is long, the main purpose is to compare the tensile strength change rate and the elongation at break change rate before and after the test, and the testing conditions are mild, so that the chemical reaction generated under the damp and hot environment of the cable and the protective sleeve cannot be simulated and tested, and the matching stability of the cable and the protective sleeve cannot be detected.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for evaluating the durability of a cable and a sheath in a damp-heat environment, the method can test the chemical reaction generated in the damp-heat environment of the cable and the sheath and test the matching stability of the cable and the sheath, and is convenient, fast and efficient, an operator can operate the cable and the sheath without professional knowledge or special training, and instruments and equipment are cheap and easy to obtain.
The invention also aims to provide a device for evaluating the durability of the cable and the sheath in the hot and humid environment.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a method for evaluating the durability of a cable and a sheath in a hot and humid environment comprises the following steps:
(1) cutting a 20-30mm long cable, wrapping the cable with a protective sleeve to prepare a sample, and enabling the two to be in close contact;
(2) adding deionized water into a high-pressure container, placing a sample on a grid above the water surface, controlling the temperature in the container to be 95-125 ℃, and controlling the pressure in the container to be 0.10-0.20 MPa;
(3) and maintaining the sample in a high-pressure container at high temperature and high pressure for 40-60 hours, and taking out for testing.
The temperature and pressure within the container refer to the ambient temperature and pressure to which the sample is subjected.
The temperature in the container in the step (2) is too low, so that the matching stability of the cable and the protective sleeve is not easy to detect; if the temperature is too high, small molecular substances in normal components such as an auxiliary agent in the cable can volatilize, so that the detection result is inaccurate. The temperature in the container in the step (2) is preferably 110-120 ℃, and the pressure is preferably 0.15 MPa.
Wherein the deionized water in the step (2) meets the following conditions: at 23 ℃, the resistivity is not less than 0.5M omega cm, and the PH value is between 6.0 and 7.2.
Before water is filled in, all parts in the test box are cleaned, and the cleaning guide is shown in GB/T2423.50-2012 appendix B.3.
Wherein, the high temperature and high pressure maintaining time in the step (3) is too short, the test effect is not good, the time is too long, the test period is prolonged, and the high temperature and high pressure maintaining time is preferably 48 hours.
The preferred technical scheme of the invention is as follows:
(1) cutting a 25mm long cable, wrapping the cable with a protective sleeve to prepare a sample, and enabling the two to be in close contact;
(2) adding deionized water into a high-pressure container, placing a sample on a grid above the water surface, controlling the temperature in the container to be 110-120 ℃, and controlling the pressure in the container to be 0.15 MPa;
(3) maintaining the sample in a high-pressure container at high temperature and high pressure for 48 hours, and taking out the sample;
(4) taking out the sample, and placing the sample in a drying oven at 60 ℃ for 2 hours;
(5) then recording the phenomena of spot formation, frost formation, color change and the like on the surface of the cable;
(6) and testing the outer surface of the cable in the sample by using an infrared spectrometer attenuated total reflection accessory (FT I R-ATR), and preferentially selecting the position with changed appearance to test the matching stability of the cable and the protective sleeve.
The method for evaluating the durability of the cable and the sheath in the damp-heat environment can test the chemical reaction generated in the damp-heat environment of the cable and the sheath, test the matching stability of the cable and the sheath, is convenient and efficient, can be operated by an operator without professional knowledge or special training, and has cheap and easily available instruments and equipment.
The testing device of the testing method is a high-pressure container, water is placed in the high-pressure container, the temperature and the pressure are controlled, a sample is placed on a grid higher than the water surface in the high-pressure container, a specific example of the high-pressure container is a high-pressure tank which comprises a heater, an inner barrel, a heater temperature control system, a safety valve, an air release valve, a pressure gauge, an outer barrel, an upper cover and a fastening bolt, the temperature range of the high-pressure tank can be controlled to be between room temperature and 150 ℃, the pressure range is 0.10 to 0.20MPa, the high-pressure tank is heated by the heater with automatic temperature control, the pressure of the safety valve and the air release valve is constant, and a metal grid is arranged in the high-pressure container and used for placing the sample.
The parameters of the high-pressure vessel according to the invention should satisfy the following requirements:
a) the temperature and relative humidity conditions given in step (2) of the evaluation method should be met and at least maintained
The time lasts for 168 hours without interruption;
b) during the test, the temperature and humidity conditions should be controlled and the temperature should be raised according to the specified conditions
And cooling;
c) the container wall construction material should not cause significant corrosion of the test sample and reduce the quality of the humidified water.
The autoclave may also be an autoclave.
Drawings
FIG. 1 is a schematic view of a high-pressure tank according to example 1.
Fig. 2 is a front view of an upper lid of the high-pressure tank according to embodiment 1.
FIG. 3 is a plan view of an upper lid of a high-pressure tank according to example 1.
Reference numerals: 1. the heater 2, the inner barrel 3, the heater temperature control system 4, the safety valve 5, the air release valve 6, the pressure gauge 7, the outer barrel 8, the upper cover 9 and the fastening bolt.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings, but is not to be construed as being limited thereto.
Example 1
The testing device of the testing method is a high-pressure tank, and comprises a heater 1, an inner tank 2, a heater temperature control system 3, a safety valve 4, an air release valve 5, a pressure gauge 6, an outer tank 7, an upper cover 8 and a fastening bolt 9, wherein the temperature range of the high-pressure tank can be controlled to be between room temperature and 150 ℃, the pressure range is 0.10 to 0.20MPa, the high-pressure tank is heated by adopting an automatic temperature control heater, the pressure of the safety valve and the air release valve is controlled to be constant, and a metal grid is arranged in the inner tank and used for placing a sample.
Example 2
The matching stability of the cable and the sheath tube used by a certain equipment limited company was tested by using the high-pressure tank of example 1 and the method of the present invention, and the sample numbers and the test results are shown in table 1.
TABLE 1 testing results of matching stability of cable and sheath
The test method of example 2 is as follows:
(1) sample preparation: cutting out a plurality of cables with the length of 25mm according to the number, wrapping the cables by using corresponding protective sleeves, winding the protective sleeves around the cables for 2 circles, and fastening the cables by using 2-3 nylon cable ties;
(2) adding deionized water into a high-pressure tank, putting all samples on a metal grid higher than the water surface, assembling and sealing the tank body, controlling the temperature in the tank to be 120 ℃, controlling the steam pressure to be 0.15MPa, and starting timing when the temperature is stable;
(3) closing the heating device after 48 hours, exhausting air, opening the sealing cover, taking out the sample, and placing the sample in a drying oven at 60 ℃ for 2 hours;
(4) taking out the sample from the drying box, cutting off the nylon ribbon, unfolding the protective sleeve, checking the surface condition of the cable sheath, and taking a picture;
(5) and recording the phenomena of spot formation, frost formation, color change, strangulation and the like on the surface of the cable.
The sample combination with the test results of visible blooming and spots was taken for infrared spectroscopy and elemental analysis, and the results are shown in table 2:
table 2 example 2 infrared spectroscopy and elemental analysis results after damp heat testing of samples
The analysis result shows that the main components of the blooming and the spots are phosphate such as magnesium hydrogen phosphate, and amide substances (processing aids) are detected in part of samples.
Under certain temperature and humidity conditions, the flame retardant and other additives in the protective sleeve are separated out and adhered to the surface of the cable, and are dissolved in water and hydrolyzed to generate acid (radicals). The cable is filled with a large amount of magnesium hydroxide or aluminum hydroxide, the magnesium hydroxide/aluminum hydroxide is difficult to dissolve in water but easy to dissolve in dilute acid, under the catalysis of phosphate radicals, the water adsorbed by the protective sleeve can dissolve the magnesium hydroxide/aluminum hydroxide out of the cable, and white phosphate is generated through reaction, so that the cable is corroded.
Example 3
Selecting 12 cables and 3 protective sleeves to evaluate the matching stability test according to the method of the embodiment 2, wherein the test temperature is 115 +/-5 ℃, other conditions are unchanged, and the test sample results are shown in a table 3:
table 3 example 3 cable and sheath pipe matching stability test results
Through infrared detection, white spots or frosting components on the surface of the cable mainly comprise magnesium hydrogen phosphate and/or aluminum phosphate, and amide substances (processing aids) are detected from part of samples.
The test has the advantages that the cable K, the cable D and the cable G with serious white spots and the cable A, the cable B, the cable C, the cable G, the cable I, the cable J and the cable L with serious deformation (tightening marks) are better in performance. The protective sleeve O has high water absorption and poor thermal stability, the protective sleeve N is soft, the damage degree to the cable is minimum, and the protective sleeve is M times. The cable K having the best performance was judged to have a higher degree of crosslinking as a result of the composition analysis.
The cable composition analysis is shown in table 4,
TABLE 4 Cable composition analysis
| Sample name | Results of infrared spectroscopic analysis |
| Cable A | EVA, magnesium hydroxide, aluminum hydroxide |
| Cable B | EVA, magnesium hydroxide |
| Cable C | EVA, magnesium hydroxide, aluminum hydroxide |
| Cable D | EVA, magnesium hydroxide |
| Cable E | EVA, magnesium hydroxide, aluminum hydroxide |
| Cable F | EVA, magnesium hydroxide, aluminum hydroxide |
| Cable G | EVA, aluminium hydroxide |
| Cable H | Polyester terephthalate and magnesium hydroxide |
| Cable I | EVA, aluminium hydroxide |
| Cable J | EVA, aluminium hydroxide |
| Cable K | EVA、Aluminum hydroxide |
| Cable L | EVA, magnesium hydroxide, aluminum hydroxide |
It can be seen that after the wet heat treatment, the white spots or the blooming component on the cable surface mainly come from the reaction with the sheath tube.
In order to verify the accuracy of the testing method, a used cable D/protective sleeve M sample is extracted from a cable user manufacturer, the cable cannot be used continuously due to corrosion short circuit, a white spot is generated on a corrosion part, and the white spot is mainly composed of magnesium hydrogen phosphate through infrared detection. Therefore, the method can be used for rapidly testing the matching stability of the cable/protective sleeve.
Comparative example 1
The samples of the embodiment 2 and the embodiment 3 are tested by adopting EN60068-2-78 standard under the test conditions of 90 ℃ of temperature, 85% of humidity and 1000 hours of test time, the surface of the sample cannot be changed, and the component difference of the contact position of the cable and the sheath before and after the infrared detection test is small.
The samples of the embodiment 2 and the embodiment 3 are subjected to an alternating temperature and humidity cycle test by adopting a GB2423.34 standard, the surface of the sample cannot be changed, and the component difference of the contact positions of the cable and the sheath before and after the infrared detection test is small.
Example 4
6 cables and 7 protective sleeves are selected and subjected to matching stability test evaluation according to the method of the example 2, and the test sample results are shown in the table 5:
table 5 example 4 cable and jacket pipe matching stability test results
By utilizing the infrared spectrum software comparison function, the infrared spectrum of the initial outer surface of the sample and the infrared spectrum of the outer surface after the matching test can be compared, the matching degree can be automatically calculated by an instrument, the matching degree represents the change degree of the main chemical groups of the sample, the change conditions of the components and the microstructure of the outer surface of the cable insulating layer can be more sensitively and accurately reflected, the higher the matching degree is, the smaller the change of the cable insulating layer is, and the better the corrosion resistance, the thermal oxidative aging resistance and the moisture and heat resistance are.
Because the infrared spectrum testing range is small (mm level), during testing, the place with changed appearance is selected for detection, and the result is the lowest matching degree value.
TABLE 6 EXAMPLE 4 determination of infrared spectrum matching degree for Damp and Heat resistance test of Cable and protective sheath
If the appearance and infrared spectral match were rated according to the 5 point rating, with the rating rules listed in table 7, the score for each cable is shown in table 8.
TABLE 7 Damp and heat resistance testing of Cable and protective sheath appearance evaluation and infrared spectrum matching degree scoring rule
TABLE 8 Damp and heat resistance test for Cable and protective sheath, appearance evaluation, and average score of matching degree of infrared spectrum
As can be seen from example 4, the method for evaluating the durability of the cable and the protective sleeve in the humid and hot environment can quickly evaluate the humidity and heat aging resistance of the cable or the protective sleeve; the evaluation of microstructure change by using appearance inspection, infrared spectrum and the like after the test is used for grading the cable, and the method is an effective method for controlling the long-term service performance of the cable.
Although the present invention and its advantages have been described in detail with reference to specific embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the apparatus, methods, and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, devices, methods, and steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such devices, methods, and steps.
Claims (5)
1. A method for evaluating the durability of a cable and a protective sleeve in a damp and hot environment is characterized by comprising the following steps:
(1) cutting a 20-30mm long cable, wrapping the cable with a protective sleeve to prepare a sample, and enabling the two to be in close contact;
(2) adding deionized water into a high-pressure container, wherein the resistivity of the deionized water at 23 ℃ is not less than 0.5 MOmega.cm, and the PH value is 6.0-7.2; placing the sample on a grid higher than the water surface, controlling the temperature in the container to be 95-125 ℃ and the pressure in the container to be 0.10-0.20 MPa;
(3) maintaining the sample in a high-pressure container at high temperature and high pressure for 40-60 hours, and taking out for testing;
(4) taking out the sample, and placing the sample in a drying oven at 60 ℃ for 2 hours;
(5) then recording the cable surface phenomenon;
(6) testing the cable outer skin in the sample by using an infrared spectrometer attenuated total reflection accessory, comparing the infrared spectrum of the initial outer surface of the sample with the infrared spectrum of the outer surface after the matching test by using the comparison function of the infrared spectrometer, and calculating the matching degree, wherein the matching degree represents the change degree of the main chemical groups of the sample; an evaluation rule for evaluating the matching degree of the appearance and the infrared spectrum is formulated according to 5 minutes, and according to the evaluation rule, the humidity and heat resistance test appearance evaluation and the infrared spectrum matching degree average score of the cable and the protective sleeve are obtained, so that the matching stability of the test cable and the protective sleeve is obtained;
the high-pressure container is a high-pressure tank and comprises a heater, an inner barrel, a heater temperature control system, a safety valve, an air release valve, a pressure gauge, an outer barrel, an upper cover and a fastening bolt.
2. The method for evaluating the durability of a cable and a protective sleeve under a hot and humid environment according to claim 1, wherein the temperature in the container in the step (2) is set to 110 ℃ to 120 ℃.
3. The method for evaluating the durability of a cable and a protective sleeve in a hot and humid environment according to claim 1, wherein the pressure in the container in the step (2) is set to 0.15 MPa.
4. The method for evaluating the durability of a cable and a protective sleeve in a hot and humid environment according to claim 1, wherein the high temperature and high pressure in the step (3) are maintained for 48 hours.
5. The method for evaluating the durability of a cable and a protective sleeve in a hot and humid environment according to claim 1, wherein the step (1) is set to intercept a cable 25mm long.
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| CN107290272A (en) * | 2017-08-03 | 2017-10-24 | 合肥祥国电子商务有限公司 | A kind of ceramic process gift durability testing system |
| CN114184488B (en) * | 2021-12-01 | 2024-01-30 | 中海石油(中国)有限公司 | Quick testing method for service life of optical cable of oil well |
| CN114324840B (en) * | 2021-12-13 | 2024-01-23 | 天津六0九电缆有限公司 | Test method for rapidly judging cable material frosting |
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