CN113884615A - Flame-retardant test method for cable heat-shrinkable tubing - Google Patents
Flame-retardant test method for cable heat-shrinkable tubing Download PDFInfo
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- 239000003063 flame retardant Substances 0.000 title claims abstract description 90
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 title claims abstract description 89
- 238000010998 test method Methods 0.000 title claims abstract description 28
- 238000002485 combustion reaction Methods 0.000 claims abstract description 173
- 238000012360 testing method Methods 0.000 claims abstract description 105
- 239000000463 material Substances 0.000 claims abstract description 33
- 239000004020 conductor Substances 0.000 claims abstract description 17
- 238000003878 thermal aging Methods 0.000 claims description 38
- 238000000034 method Methods 0.000 claims description 19
- 230000032683 aging Effects 0.000 claims description 12
- 239000007769 metal material Substances 0.000 claims description 12
- 229910052755 nonmetal Inorganic materials 0.000 claims description 10
- 230000014759 maintenance of location Effects 0.000 claims description 2
- 230000002265 prevention Effects 0.000 abstract description 5
- 238000011056 performance test Methods 0.000 abstract description 4
- 239000000523 sample Substances 0.000 description 61
- 230000007613 environmental effect Effects 0.000 description 3
- 238000007706 flame test Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000013461 design Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000002431 foraging effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
- G01N31/12—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using combustion
Abstract
The invention discloses a flame-retardant test method of a cable heat-shrinkable sleeve, which comprises a single-core combustion test method, wherein the single-core combustion test method comprises the following steps of: thermally shrinking a material which is the same as the cable thermal shrinkage bush on a cable conductor to prepare a single-core combustion sample; and carrying out a single-core combustion test on the single-core combustion sample, and judging the single-core combustion flame retardant property of the cable heat-shrinkable bush according to the result of the single-core combustion test. The invention can solve the problem of the flame retardant performance test of the cable heat-shrinkable sleeve, accurately detect the flame retardant performance of the cable heat-shrinkable sleeve and provide reliability guarantee for cable fire prevention.
Description
Technical Field
The invention relates to a flame-retardant test method of a cable heat-shrinkable sleeve.
Background
The nuclear power station uses a large number of cables for electric energy and signal transmission, when the cables are terminated, the cables are permanently connected with electrical equipment and then insulated by using the heat-shrinkable sleeve, the sealing, insulation and moisture prevention of the cable ends are ensured, the operation conditions under normal environmental conditions, design basis accident environmental conditions and serious accident environmental conditions are met, and the heat-shrinkable sleeve plays an important role in normal operation and safe shutdown of the nuclear power station.
The cable heat shrink should not be inferior to the cable's performance as a termination fitting for the cable. The nuclear power station cable has definite requirements on electrical performance, mechanical performance, flame retardant performance, service life, irradiation resistance, high temperature and high pressure resistance and the like, and in the series of requirements, except for the flame retardant performance, the cable heat-shrinkable sleeve can be detected according to the cable test standard.
At present, the flame retardance of a cable is detected according to a single-core burning test and a bundled burning test specified in GB/T18380, but the main structure of the cable heat-shrinkable sleeve comprises a branch glove and a core sleeve, the combined length of the branch glove and the core sleeve is only 20cm-30cm, the length requirement of a sample specified in the GB/T18380 standard cannot be met, the method is not suitable for the flame retardance test of the cable heat-shrinkable sleeve, whether aging influences the flame retardance performance or not is detected for the cable, the accelerated thermal aging service life completion time of the cable heat-shrinkable sleeve and the accelerated thermal aging service life of the cable are inconsistent under the same temperature condition, and the sample of the cable heat-shrinkable sleeve after aging is difficult to obtain according to the cable test standard.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art, and provides a flame-retardant test method of a cable heat-shrinkable tubing, which can solve the problem of flame-retardant performance test of the cable heat-shrinkable tubing, accurately detect the flame-retardant performance of the cable heat-shrinkable tubing and provide reliability guarantee for cable fire prevention.
The technical scheme for solving the technical problems is as follows:
a flame-retardant test method of a cable heat-shrinkable sleeve comprises a single-core combustion test method, and the single-core combustion test method comprises the following steps:
thermally shrinking a material which is the same as the cable thermal shrinkage bush on a cable conductor to prepare a single-core combustion sample;
and carrying out a single-core combustion test on the single-core combustion sample, and judging the single-core combustion flame retardant property of the cable heat-shrinkable bush according to the result of the single-core combustion test.
Preferably, the length of the single core combustion sample is 600 ± 25 mm.
Preferably, the flame resistance test method further comprises a bundled flame test method comprising:
if the single-core combustion test result is qualified, thermally shrinking a material which is the same as the material of the cable heat-shrinkable sleeve on a cable conductor to prepare a bundled combustion sample, and performing a bundled combustion test on the bundled combustion sample;
and judging the bundled combustion flame retardant property of the cable heat-shrinkable sleeve according to the result of the bundled combustion test.
Preferably, the length of the bundled combustion sample is greater than or equal to 3.5 m;
the number of the bundled combustion samples is multiple, and the lengths of the multiple bundled combustion samples are equal.
Preferably, the number of bundled combustion samples is calculated according to the following formula:
wherein V is the total volume of the nonmetal material per meter, and the unit is L/m; s is the total area of the cross section of a bundled combustion sample in mm2；SmIs the total area of the metal material in the cross section of a bundle of burning test pieces in mm2。
Preferably, the flame retardant test further comprises:
carrying out accelerated thermal aging treatment on the bundled combustion sample to obtain an aged bundled combustion sample;
performing a bundled combustion test on the aged bundled combustion sample;
and comparing the bundling combustion test result of the aged bundling combustion sample with the bundling combustion test result of the unaged bundling combustion sample, and judging the flame retardant property of the cable heat-shrinkable sleeve according to the comparison result.
Preferably, the accelerated heat aging treatment of the bundled combustion specimens comprises:
determining accelerated thermal aging time and accelerated thermal aging temperature;
and finishing an accelerated thermal aging test according to the determined accelerated thermal aging time and accelerated thermal aging temperature to obtain the aged bundled combustion sample.
Preferably, the determining the accelerated thermal aging time and the accelerated thermal aging temperature includes:
respectively exposing the bundled combustion samples at more than three different test temperatures to obtain change curves of the elongation at break along with time under different test temperature conditions;
respectively taking the time corresponding to the point where the change curve intersects with the horizontal line with the elongation at break retention rate of 50% as the end point time at the test temperature;
carrying out linear fitting on the logarithm of each terminal time and the reciprocal of the absolute temperature corresponding to the test temperature according to an Arrenius empirical formula to obtain a time-temperature curve;
and determining the accelerated thermal aging time and the accelerated thermal aging temperature according to the time-temperature curve.
Preferably, before said preparing a single core combustion sample and said preparing a bundled combustion sample, further comprising:
respectively calculating the volume ratio of the non-metal material of the cable heat-shrinkable sleeves of various specifications after heat shrinkage for the same series of cable heat-shrinkable sleeves of various specifications;
selecting a cable heat-shrinkable sleeve with the specification that the volume ratio of the non-metal material after heat shrinkage is the largest as a representative sleeve of the series of cable heat-shrinkable sleeves;
and (2) thermally shrinking a material which is the same as the material of the cable heat-shrinkable sleeve on a cable conductor to prepare a single-core combustion sample/bundled combustion sample, which specifically comprises the following steps:
and (3) thermally shrinking a material which is the same as the representative sleeve on a cable conductor matched with the representative sleeve to prepare a single-core combustion sample/bundled combustion sample.
The flame-retardant test method of the cable heat-shrinkable sleeve can solve the problem that the flame-retardant performance cannot be detected due to the fact that the structure and the length of the cable heat-shrinkable sleeve cannot meet the sample requirements of the flame-retardant test standard of a corresponding cable in the prior art, and can avoid misjudgment of the flame-retardant performance of the cable heat-shrinkable sleeve caused by the cable flame-retardant problem, improve the accuracy of the flame-retardant performance test of the cable heat-shrinkable sleeve and provide reliability guarantee for cable fire prevention compared with the method that the core sleeve is directly heat-shrunk on the cable insulation core in the prior art. In addition, the flame-retardant test method can also detect the influence of aging on the flame-retardant performance of the cable heat-shrinkable tubing, and can avoid the problem that the accelerated thermal aging time of the cable is not matched with the accelerated thermal aging time of the cable heat-shrinkable tubing in the prior art.
Drawings
FIG. 1 is a schematic diagram of a method for testing the flame retardancy of a heat shrinkable sleeve for cables according to an embodiment of the present invention;
FIG. 2 is a temperature index plot of a core-in-sleeve material in an embodiment of the present invention.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the indication of orientation or positional relationship, such as "on" or the like, is based on the orientation or positional relationship shown in the drawings, and is only for convenience and simplicity of description, and does not indicate or imply that the device or element referred to must be provided with a specific orientation, constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected," "disposed," "mounted," "fixed," and the like are to be construed broadly, e.g., as being fixedly or removably connected, or integrally connected; either directly or indirectly through intervening media, or through the interconnection of two elements. The specific meaning of the above terms in the present invention can be understood in specific cases for those skilled in the art.
Example 1
As shown in fig. 1, the embodiment discloses a flame retardant test method for a cable heat-shrinkable sleeve, which includes a single-core burning test method, and the single-core burning test method includes:
thermally shrinking a material which is the same as the material of the cable thermal shrinkage bush on a cable conductor to prepare a single-core combustion sample;
and (4) carrying out a single-core combustion test on the single-core combustion sample, and judging the single-core combustion flame retardant property of the cable heat-shrinkable bush according to the result of the single-core combustion test.
Specifically, in the flame-retardant test method, the cable heat-shrinkable sleeve is mainly used for the cable for the nuclear power station, the flame-retardant performance of the cable for the nuclear power station is detected by the method specified in GB/T18380, and in order to keep consistent with the detection of the flame-retardant performance of the cable, the GB/T18380 is preferably used as a flame-retardant test standard in the flame-retardant test method, and the length of the single-core combustion sample is preferably 600 +/-25 mm. Moreover, because the existing cable heat-shrinkable tubing generally comprises the branch gloves and the core sleeves, and the branch gloves and the core sleeves are made of the same material, the flame retardant performance of the whole cable heat-shrinkable tubing can be qualified only by detecting that the flame retardant performance of the core sleeves is qualified. In addition, the whole length of the existing cable heat-shrinkable sleeve is only 20-30cm, and the requirement of a single-core combustion test in GB/T18380.12 (namely GB/T18380 part 12) on a sample cannot be met, so the single-core combustion test in the flame retardant test method is to prepare a sufficiently long core sleeve from a material which is the same as the core sleeve of the cable heat-shrinkable sleeve according to the specification of the core sleeve, then thermally shrink the core sleeve on a cable conductor to obtain the single-core combustion sample capable of meeting the requirement of the single-core combustion test, and then perform the single-core combustion test on the single-core combustion sample, wherein the specific steps of the single-core combustion test are performed according to the steps of the single-core combustion test in GB/T18380.12, and are not repeated here.
After the single-core combustion test is finished, if the surface of a single-core combustion sample is not damaged, or only softening or deformation occurs, or the distance between the starting point of a carbonized part obtained after combustion and the lower edge of an upper support in the single-core combustion test is larger than 50mm, or the distance between the combustion downward extending distance and the lower edge of the upper support is smaller than or equal to 540mm, judging that the single-core flame retardant performance is qualified, meeting the single-core combustion flame retardant performance requirement of GB/T18380.12 of the cable heat-shrinkable sleeve, otherwise, judging that the single-core flame retardant performance is unqualified, and when the single-core flame retardant performance is judged to be unqualified, confirming that the flame retardant performance of the cable heat-shrinkable sleeve is unqualified, and finishing the flame retardant test.
In some embodiments, the present flame test method further comprises a bundled flame test method comprising:
if the single-core burning test result is qualified, thermally shrinking a material which is the same as the material of the cable heat-shrinkable sleeve on the cable conductor to prepare a bundled burning sample, and performing the bundled burning test on the bundled burning sample;
and judging the bundled combustion flame retardant property of the cable heat-shrinkable sleeve according to the result of the bundled combustion test.
Specifically, a wire core sleeve which is long enough is made of a material which is the same as the material of the wire core sleeve of the cable heat-shrinkable sleeve according to the specification of the wire core sleeve, and then the wire core sleeve is heat-shrunk on a cable conductor, so that a bundled combustion sample which can meet the requirements of a bundled combustion test is obtained. The bundled combustion specimens differ from the single core combustion specimens in length, with the bundled combustion specimens in this example having a length of 3.5m or greater to meet the length requirements for bundled combustion specimens for the bundled combustion test in GB/T18380.34 (i.e., GB/T18380 part 34). And then, carrying out a bundled combustion test on the bundled combustion sample, wherein the specific steps of the bundled combustion test are carried out according to the bundled combustion test steps in GB/T18380.34, and are not repeated herein.
It should be noted that, in the single-core combustion test and the bundled combustion test, the single-core combustion test only requires one unaged single-core combustion sample, and the bundled combustion test requires a plurality of bundled combustion samples, that is, the number of the bundled combustion samples is multiple, and the lengths of the plurality of bundled combustion samples are all equal.
In this example, the number of bundled combustion samples required to perform the bundled combustion test was calculated according to the following calculation:
wherein n is the number (root) of the sample, and when the calculated value of n is not an integer, the integer closest to the value is taken (0.5 and up to 1); v is the total volume of the nonmetal material per meter, and the unit is L/m; s is the total area of the cross section of a bundled combustion sample in mm2；SmIs the total area of the metal material in the cross section of a bundle of burning test pieces in mm2。
Taking a low-voltage cable heat-shrinkable sleeve matched with a low-voltage cable for a nuclear power station as an example, the heat shrinkage ratio is
The area of the cross section of the low-voltage cable heat-shrinkable sleeve is 4mm2To obtain a bundle-formed burning test piece having a length of 3.5m, the total cross-sectional area of the bundle-formed burning test piece after heat shrinkage being 19.519.5mm2The number of such bundled combustion specimens required for the bundled combustion test is then: n is 1000x3.5/(19.5-4) 226
In some embodiments, the present flame retardant test method further comprises:
carrying out accelerated thermal aging treatment on the bundled combustion sample to obtain an aged bundled combustion sample;
performing a bundled combustion test on the aged bundled combustion sample;
and comparing the bundling combustion test result of the aged bundling combustion sample with the bundling combustion test result of the unaged bundling combustion sample, and judging the flame retardant property of the cable heat-shrinkable sleeve according to the comparison result, namely accurately judging whether the flame retardant property of the cable heat-shrinkable sleeve is reduced or not after the cable heat-shrinkable sleeve is aged.
Further, the bundled combustion specimens were subjected to an accelerated thermal aging treatment comprising:
determining accelerated thermal aging time and accelerated thermal aging temperature;
and finishing an accelerated thermal aging test according to the determined accelerated thermal aging time and accelerated thermal aging temperature to obtain an aged bundled combustion sample.
In this embodiment, determining the accelerated thermal aging time and the accelerated thermal aging temperature includes the following steps:
respectively exposing a plurality of bundled combustion samples to more than three different test temperatures, specifically implementing the method according to GB/T11026.1-2003 standard, and obtaining change curves of elongation at break with time under different test temperature conditions so as to determine the thermal life of the bundled combustion samples;
respectively taking the time corresponding to the point of intersection of the change curve and a horizontal line with 50% of elongation at break as the end point time at the test temperature;
carrying out linear fitting on the logarithm of each terminal time and the reciprocal of the absolute temperature corresponding to the test temperature according to an Arrenius empirical formula to obtain a time-temperature curve of the thermal life of the bundled combustion sample material;
and determining the accelerated thermal aging time and the accelerated thermal aging temperature according to the time-temperature curve.
Specifically, taking a low-voltage cable for a nuclear power station as an example, the service life of the low-voltage cable for the nuclear power station at the temperature of 90 ℃ should reach 40-60 years, and correspondingly, the service life of a low-voltage cable heat-shrinkable sleeve corresponding to the low-voltage cable for the nuclear power station at the temperature of 90 ℃ should also reach 40-60 years. The accelerated heat aging process may reduce the time required for aging in order to detect the effect of aging on the flame retardant properties of the cable heat shrink, with lower temperatures requiring longer accelerated heat aging times. After the low-voltage cable heat-shrinkable sleeve material is exposed at four temperatures of 135 ℃, 150 ℃, 165 ℃ and 180 ℃, a time-temperature curve of the thermal life of the low-voltage cable heat-shrinkable sleeve material is obtained (as shown in fig. 2, wherein the ordinate is time, and the abscissa is the reciprocal of the K's temperature). As can be seen from fig. 2, the service life of the low-voltage cable heat-shrinkable sleeve is 66.6 years at 90 ℃ and 1200 hours at 155 ℃, that is, the time required for aging can be greatly reduced at 155 ℃, therefore, 155 ℃ can be used as the accelerated heat treatment temperature, and the accelerated heat treatment time at the accelerated heat treatment temperature is 1200 hours, that is: the bundle combustion sample made of this material was left at 155 ℃ for 1200 hours to obtain an aged bundle combustion sample.
Because the cable heat-shrinkable tubing of same series generally divide into a plurality of specifications, the non-metallic material of the adoption of the cable heat-shrinkable tubing of each specification is the same, but, its core sleeve's aperture is respectively different, and the non-metallic material volume after the pyrocondensation accounts for than also there is the difference, and at this moment, if carry out fire-retardant test respectively to the cable heat-shrinkable tubing of every specification, work load is big, and is inefficient, therefore, in this embodiment, before making single core burning sample and making the bundling burning sample, still include:
for the same series of cable heat-shrinkable sleeves with a plurality of specifications, respectively calculating the volume ratio of the non-metal material of the cable heat-shrinkable sleeve with each specification after heat shrinkage:
selecting a cable heat-shrinkable sleeve with the specification that the volume ratio of the non-metal material after heat shrinkage is the largest as a representative sleeve of the series of cable heat-shrinkable sleeves;
the method comprises the following steps of thermally shrinking a material which is the same as the material of the cable heat-shrinkable sleeve on a cable conductor to prepare a single-core combustion sample/bundled combustion sample, and specifically comprises the following steps: and (3) thermally shrinking a material which is the same as the representative sleeve on a cable conductor matched with the representative sleeve to prepare a single-core combustion sample and a bundled combustion sample.
Specifically, in the same series of cable heat-shrinkable sleeve products, the cable heat-shrinkable sleeve with the largest proportion of combustible substances has the worst flame-retardant performance, and when the cable heat-shrinkable sleeve with the largest proportion of combustible substances has qualified flame-retardant performance, the cable heat-shrinkable sleeves with other specifications in the same series can also meet the flame-retardant requirement.
Taking a low-voltage power cable as an example, in a cable heat-shrinkable sleeve corresponding to the low-voltage power cable, the heat shrinkage ratio is
The thermal shrinkage insulating tube is smallest, the corresponding cable core is thinnest, the volume-to-total volume ratio of the non-metal material after thermal shrinkage is largest, namely the combustible matter accounts for the largest ratio, so that the thermal shrinkage ratio of the specification can be selected as
The heat-shrinkable insulating tube as a representative bushing was subjected to a single-core burning test and a bundle burning test at a heat shrinkage ratio of
When the flame retardant property of the heat-shrinkable insulating tube is qualified, the ratio of the flame retardant property to the heat-shrinkable insulating tube is
All the cable heat-shrinkable sleeves of the same series of the heat-shrinkable insulating tubes have qualified flame retardant performance.
The following takes a low-voltage cable heat-shrinkable sleeve matched with a low-voltage power cable for a nuclear power station as an example, and details the process of the test method of the cable heat-shrinkable sleeve in the embodiment are as follows:
selecting a flame-retardant test standard which is consistent with the flame-retardant performance detection of the low-voltage cable for the nuclear power station as the flame-retardant test standard of the low-voltage cable heat-shrinkable sleeve according to the flame-retardant performance requirement of the low-voltage power cable for the nuclear power station, namely selecting GB/T18380.12 as the flame-retardant test standard of a single-core combustion test of the low-voltage cable heat-shrinkable sleeve and selecting GB/T18380.34 as the flame-retardant test standard of a bundled combustion test of the low-voltage cable heat-shrinkable sleeve;
making the core sleeve of 0.6m length from the same material as the core sleeve of the low-voltage cable heat-shrinkable sleeve, wherein the core sleeve has a heat-shrinkable ratio of
Then directly thermally shrinking the prepared core sleeve on a conductor of a low-voltage power cable for a nuclear power station to prepare a 0.6m single-core combustion sample, then carrying out a single-core combustion test on the prepared single-core combustion sample according to GB/T18380.12, wiping the single-core combustion sample after the single-core combustion test is finished, if the surface of the single-core combustion sample is not damaged, or only softened or deformed, or the distance between the starting point of a carbonized part obtained after combustion and the lower edge of an upper bracket in the single-core combustion test is more than 50mm, or the distance from the combustion downward extension to the lower edge of the upper bracket is less than or equal to 540mm, the single-core flame retardant performance is qualified, the cable heat-shrinkable sleeve meets the requirement of the single-core combustion flame retardant performance of GB/T18380.12, the bundled combustion test can be continuously carried out, otherwise, the single-core flame retardant performance is unqualified, and when the single-core flame retardant performance is unqualified, the flame-retardant performance of the cable heat-shrinkable sleeve is unqualified, and the flame-retardant test is finished;
making the core sleeve of 3.5m length from the same material as the core sleeve of the low-voltage cable heat-shrinkable sleeve, wherein the core sleeve has a heat-shrinkable ratio of
And then directly thermally shrinking the prepared core sleeve on a conductor of a low-voltage power cable of a nuclear power station to prepare a bundled combustion sample of 3.5m according to appendix C in GB/T18380.34-2008The calculation formula of (1) calculates the number of bundled combustion samples required by the bundled combustion test of the low-voltage power cable heat-shrinkable sleeve to be 226, then, the bundled combustion test is carried out on the 226 bundled combustion samples according to GB/T18380.34, after the bundled combustion test is finished, the bundled combustion samples are wiped, if the maximum carbonization range above the bottom edge of a blowtorch in the bundled flame-retardant test is less than or equal to 2.5m, the bundled flame-retardant performance is qualified, the cable heat-shrinkable sleeve meets the bundled combustion flame-retardant performance requirement of GB/T18380.34, the flame-retardant performance of the cable heat-shrinkable sleeve is qualified, the bundled combustion test of the aged bundled combustion samples can be continuously carried out, otherwise, the bundled combustion flame-retardant performance is unqualified, the flame-retardant performance of the cable heat-shrinkable sleeve is unqualified, and the flame-retardant test is finished;
266 samples identical to the bundled combustion sample are prepared and placed at 155 ℃ for 1200 hours to accelerate thermal aging to obtain an aged bundled combustion sample, and then a bundled combustion test is carried out on the 226 aged bundled combustion samples according to GB/T18380.34, after the bundled combustion test is finished, if the damage range (i.e. the distance between the starting point of the carbonized part obtained after combustion and the bottom edge of the torch in the bundled combustion device) is larger than that of the unaged bundled combustion sample, the aging reduces the flame retardant performance of the cable heat-shrinkable sleeve, and if the length of the carbonized part of the aged bundled combustion sample is smaller than 2.5m, the flame retardant performance of the cable heat-shrinkable sleeve is judged to be qualified, and the cable heat-shrinkable sleeve has strong flame retardant performance even at the end of a nuclear power station.
The flame-retardant test method of the cable heat-shrinkable tubing of the embodiment is characterized in that the flame-retardant test standard is selected, the test structure design is adopted, the length requirement is met, the number of samples is calculated, the representativeness is achieved, the aging temperature, the aging time and the like are improved, the problem that in the prior art, the flame-retardant performance cannot be detected due to the fact that the structure and the length of the cable heat-shrinkable tubing cannot meet the sample requirements of the flame-retardant test standard of a corresponding cable can be solved, and compared with a method for directly thermally shrinking the cable core tubing on a cable insulation core in the prior art, misjudgment of the flame-retardant performance of the cable heat-shrinkable tubing by the cable flame-retardant problem can be avoided, the accuracy of the flame-retardant performance test of the cable heat-shrinkable tubing is improved, and reliability guarantee is provided for cable fire prevention. In addition, the flame-retardant test method can also detect the influence of aging on the flame-retardant performance of the cable heat-shrinkable tubing, and can avoid the problem that the accelerated thermal aging time of the cable is not matched with the accelerated thermal aging time of the cable heat-shrinkable tubing in the prior art.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (9)
1. The flame-retardant test method of the cable heat-shrinkable sleeve is characterized by comprising a single-core combustion test method, wherein the single-core combustion test method comprises the following steps:
thermally shrinking a material which is the same as the cable thermal shrinkage bush on a cable conductor to prepare a single-core combustion sample;
and carrying out a single-core combustion test on the single-core combustion sample, and judging the single-core combustion flame retardant property of the cable heat-shrinkable bush according to the result of the single-core combustion test.
2. The method for flame-retardant testing of cable heat-shrinkable tubing of claim 1, wherein the length of the single core burning sample is 600 ± 25 mm.
3. The method of claim 1, further comprising a bundle burn test method, the bundle burn test method comprising:
if the single-core combustion test result is qualified, thermally shrinking a material which is the same as the material of the cable heat-shrinkable sleeve on a cable conductor to prepare a bundled combustion sample, and performing a bundled combustion test on the bundled combustion sample;
and judging the bundled combustion flame retardant property of the cable heat-shrinkable sleeve according to the result of the bundled combustion test.
4. The method of claim 3, wherein the bundle of burned test pieces has a length of 3.5m or more;
the number of the bundled combustion samples is multiple, and the lengths of the multiple bundled combustion samples are equal.
5. The method of claim 4, wherein the number of the bundled burned test pieces is calculated according to the following formula:
wherein V is the total volume of the nonmetal material per meter, and the unit is L/m; s is the total area of the cross section of a bundled combustion sample in mm2；SmIs the total area of the metal material in the cross section of a bundle of burning test pieces in mm2。
6. The method for flame-retardant testing of a cable heat-shrink according to any one of claims 3-5, further comprising:
carrying out accelerated thermal aging treatment on the bundled combustion sample to obtain an aged bundled combustion sample;
performing a bundled combustion test on the aged bundled combustion sample;
and comparing the bundling combustion test result of the aged bundling combustion sample with the bundling combustion test result of the unaged bundling combustion sample, and judging the flame retardant property of the cable heat-shrinkable sleeve according to the comparison result.
7. The method of claim 6, wherein the subjecting the bundle of burned test pieces to an accelerated heat aging process comprises:
determining accelerated thermal aging time and accelerated thermal aging temperature;
and finishing an accelerated thermal aging test according to the determined accelerated thermal aging time and accelerated thermal aging temperature to obtain the aged bundled combustion sample.
8. The method of claim 7, wherein the determining the accelerated thermal aging time and the accelerated thermal aging temperature comprises:
respectively exposing the bundled combustion samples at more than three different test temperatures to obtain change curves of the elongation at break along with time under different test temperature conditions;
respectively taking the time corresponding to the point where the change curve intersects with the horizontal line with the elongation at break retention rate of 50% as the end point time at the test temperature;
carrying out linear fitting on the logarithm of each terminal time and the reciprocal of the absolute temperature corresponding to the test temperature according to an Arrenius empirical formula to obtain a time-temperature curve;
and determining the accelerated thermal aging time and the accelerated thermal aging temperature according to the time-temperature curve.
9. The method of claim 6, further comprising, prior to said preparing a single core combustion sample and said preparing a bundle combustion sample:
respectively calculating the volume ratio of the non-metal material of the cable heat-shrinkable sleeves of various specifications after heat shrinkage for the same series of cable heat-shrinkable sleeves of various specifications;
selecting a cable heat-shrinkable sleeve with the specification that the volume ratio of the non-metal material after heat shrinkage is the largest as a representative sleeve of the series of cable heat-shrinkable sleeves;
and (2) thermally shrinking a material which is the same as the material of the cable heat-shrinkable sleeve on a cable conductor to prepare a single-core combustion sample/bundled combustion sample, which specifically comprises the following steps:
and (3) thermally shrinking a material which is the same as the representative sleeve on a cable conductor matched with the representative sleeve to prepare a single-core combustion sample/bundled combustion sample.
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