GB/T 2951.5-1997 General test methods for cable insulation and sheathing materials Part 2: Specific test methods for elastomeric mixtures Section 1: Ozone resistance test - Hot extension test - Mineral oil immersion test
Some standard content:
1 Scope
National Standard of the People's Republic of China
Comman test methads for insulatingand sheathling materials of electric cablesPart 2:Methods specific to elastomeric compoundsSection nne : Ozone resistance test-Hot set test-Mineral oil immersion test
GB/T 2951.5—1997
idt IEC 811-2-1.1986
No.1(1992>1st amendment
No.2(1993)2nd amendment
Replaces GB/T 2951. 1-94
1/T25115-
GB/T2951.18—94bzxZ.net
GB/T 2951. 35-- 94
GB/T2951 standard specifies the test methods for polymer insulation and sheath materials of power distribution relays and communication cables, including marine cables.
GB/T2951.5 specifies the ozone test method, hot elongation test method and mineral oil immersion test method. Applicable to elastomer mixtures of wires and relays.
2 Test principles
This standard does not specify all test conditions (such as temperature, duration, etc.) and all test requirements, which should be specified in the relevant cable product standards.
Any test requirements specified in this standard can be modified in the relevant cable product standards to meet the needs of special types of cables. 3 Scope of application
The test conditions and test parameters specified in this standard are applicable to the most commonly used types of insulation and sheath materials for cables, wires and cords. 4 Type tests and other tests
The test methods described in this standard are primarily used as type tests. Some test items, especially type tests The conditions for testing are essentially different from those for testing that is often performed (such as routine testing). This standard has specified these differences. 5 Pretreatment
All tests should be carried out after the insulation and sheath materials have been extruded or vulcanized (or cross-linked) for at least 16 hours. If the test is carried out at ambient temperature, the specimen should be stored at (23 ± 5) °C for at least 3 hours. 6 Test temperature
Unless otherwise specified, the test should be carried out at ambient temperature. Approved by the State Administration of Technical Supervision on October 28, 1997 1998-10-01 implementation
7 Intermediate value
CB/T2951.51997
Arrange the test data with the required number in ascending or descending order. If the number of valid data is an odd number, the intermediate value is the middle value. If it is an odd number, the intermediate value is the average of the middle two values. 8 Ozone resistance test
Warning: Be aware of the toxicity of ozone. Take preventive measures to reduce the contact of operators with ozone under any circumstances. The concentration of good oxygen in the working environment shall not exceed 0.1×10-\ (the number of ozone parts per million parts of air by volume) or the smaller value of the indicators specified in the existing industrial hygiene standards.
8.1 Test method
8.1.1 Test equipment
a) An ozone generator capable of controlling the amount of ozone; h) A circulation system in which ozone passes through a test box containing the test sample under controllable conditions of temperature and degree; ) A device for determining the percentage of oxygen concentration. 8.1.2 Sampling
Whether the cable is central or multi-core, only one insulated core needs to be selected for testing. A sufficient length of insulated core is taken at a distance of not less than 1.5 m from the end to prepare ? samples: If the core is wrapped with a semi-conductive layer, the insulated core sufficient for preparing 4 samples should be cut. 8.1.3 Sample preparation
Remove all outer sheaths from the insulated cores. However, the insulation shall not be damaged. Except for the sheaths that are directly wrapped on the insulation or adhered to the insulation before vulcanization.
If there is a semi-conductive layer wrapped around the outside of the insulated core, it should be removed. If there is an extruded semi-conductive shield outside the insulated core, the semi-conductive shields of two samples should be removed, while the semi-conductive shields of the other two samples should be retained.
8.1.4 Sample bending
If there is no extruded semi-conductive shield on the insulated core, one sample should be wound around the test piece without twisting in its original bending direction and plane and secured with a rope or tape at the intersection of the ends; the second sample should also be bent along its original bending plane, but in the opposite direction.
If there is an extruded semi-conductive shield on the insulating core, the sample with the semi-conductive layer removed and the sample with the semi-conductive shield retained shall be bent in two directions as described above.
The bending test shall be carried out at room temperature or 20°C, whichever is higher. The test piece shall be a yellow sawn, lead-embedded wooden test bar with appropriate treatment. The diameter H shall be as specified below:
Outer diameter of insulating core d,rmrm
Test support diameter
(multiple of outer diameter of insulating core)
If the sample is too hard to cross at both ends: the sample shall be bent at least 180° on the test bar of specified diameter and tied firmly. B.1.5 Sample treatment
Each test surface shall be wiped with a clean cloth to remove dust or moisture. Before the test, the bent sample on the test bar shall be placed in air at ambient temperature for 30~45 min. No trace treatment is required. 8.1.6 Exposure to ozone
GB/T 2951. 5 - 1997
The treated specimens shall be placed in a test chamber with a stopcock and maintained at a temperature of (25±2)°C. The specimens shall be exposed to dry circulating air, and the ozone concentration and duration shall comply with the provisions of the relevant cable product standards. The air flow rate shall be closely controlled between 280L/h and 560L/h, and the air pressure in the chamber shall be slightly higher than the atmospheric pressure. 8.1.7 Evaluation of test results
After the specified test time is over, remove the specimen from the test chamber. Check with normal vision or corrected vision without a magnifying glass, and the 180° bend on the specimen farthest from the ligature should not be cracked. 8.2 Determination of true oxygen concentration
8.2.1 Chemical analysis
8.2.1.1 Reagents
The reagents shall be of analytical grade.
The whole test process should be carried out with distilled water. ) Powder indicator solution: 1g of soluble starch is added to 40ml of cold water, stirring constantly, and heated to boiling until the starch is completely dissolved. Dilute with cold water to about 200ml. Then add 1/2 of crystalline zinc chloride, clarify the solution, and pour off the supernatant for use. The solution should be changed every two or three days for storage and regular use.
Alternatively, 1g of soluble starch can be dissolved in 100ml of boiling water to prepare a fresh solution. Regardless of which starch solution is used as an indicator, a few drops of 10% iodine should be added to the solution for titration. h) Standard iodine solution: Add 2g of potassium iodide (KI) and 10ml of water to the weighing tube and weigh it, then add iodine directly to the solution in the weighing tube placed on the balance pan until the total weight of iodine in the solution is about 0.1g. Accurately weigh the iodine-containing solution and determine the amount of iodine added. Pour the solution into a beaker, wash the weighing tube with distilled water on the beaker, and pour the solution in the beaker into a 1000ml volumetric flask, then add the distilled water used to rinse the beaker to the volumetric flask and dilute to 1000ml. Note: If stored in a dark and cold place and in a tightly sealed brown bottle, the solution is quite stable. c) Sodium thiosulfate solution: Place about 0.21g Va2S,O,·5H,0 in a 1000ml volumetric flask and dilute to 1000ml. Make a sodium thiosulfate (NaSO,) solution with a concentration basically the same as the standard iodine solution. The concentration of the sodium thiosulfate solution will gradually decrease. On the day of the ozone test, this solution should be used as a standard for the iodine solution. The concentration E of NaS.O. solution is calculated as iodine equivalent: and expressed as milligrams of iodine per liter of solution, the formula is E-
where: F---volume of iodine solution, ml;
C-iodine concentration + trg/L:
S-volume of NaS.O. solution used for titration, mL. d) Potassium iodide solution: dissolve 20g pure KI in 2000ml water. e) Acetic acid: prepare a 10% solution (by volume). 8.2. 1.2 Test Procedure
A measured volume of ozone-containing air shall be bubbled through the KI solution in the test chamber, or a measured volume of oxygen-containing air shall be collected and mixed with the KI solution by appropriate means.
Two optional methods:
a) A sampling bottle containing 100 mL of K1 solution is connected to the sampling stopper of the test chamber on one side and to the 500 mL gas burette on the other side. The glass tube connecting the sampling bottle to the test chamber stopper should be located well below the level of the KI solution in the sampling bottle. Open the two-way stopper on the test chamber stopper to open the atmosphere and raise the aspirator bottle connected to the bottom of the burette to fill the burette with water. Then close the burette stopper connected to the atmosphere and open the sampling bottle stopper at the same time. The sampling burette in the test chamber is now connected to the sampling bottle. Then lower the aspirator bottle until the water flows out of the burette. At this time, the 500 mL of gas in the test chamber will bubble through the KI solution. Then close the two stopcocks and remove the sampling bottle for titration. b) Fill a 400mL separatory funnel with KI solution and connect it to the test cock of the test chamber. Open the test cock and the bottom cock of the separatory funnel at the same time, until about 200mL of KI solution flows into the graduated volume below. Quickly close the test cock and the separatory funnel stopper, remove and plug the separatory funnel. At this time, the amount of gas in the separatory funnel should be the difference between 400mL and the amount of KI dissolved in the volume. Shake the separatory funnel to allow the gas to react completely with the KI solution. The KI solution in the volume should be tested with a starch indicator to see if it contains free KI. If so, the gas sample should be measured and resampled. Regardless of which method is used, the KI solution that reacts chemically with a known volume of gas from the test chamber should be titrated with a starch indicator and a calibrated Na,S,) solution.
8.2.1.3 Calculation
At room temperature and atmospheric pressure, 1 mg of iodine is equivalent to 0.1 mL of ozone (within the accuracy range of this analytical method at average room temperature and atmospheric pressure). The ozone concentration can be calculated by the following formula: Ozone concentration % (volume ratio) = 10SE
Wherein, S—the amount of Na2SO4 solution used for titration, mL+E—the iodine equivalent of Na2SO4 solution, i.e., the number of grams of iodine per mL of Na2SO4; V—the amount of gas sample collected, mL.
8.2.2 Direct measurement with an oxygen meter
As an alternative to chemical analysis, the ozone concentration can be measured using The ozone meter is used for direct measurement, and the odor meter is used for comparison and calibration with the results obtained by chemical analysis.
9 Hot extension test
9.1 Sampling, sample preparation and determination of cross-sectional area Cut two insulation sample sections and sheath sample sections from each sample to be tested, prepare the sample and measure the cross-sectional area according to the test method specified in Chapter 9 of GB/T2951.1-1997, and then conduct the test. The dumbbell test piece shall be prepared from the inner layer of the insulation and sheath after removing all ridges and/or flat conductive layers. The thickness of the test piece shall not be less than 0.8mm1 and not more than 2.0mm. If a 0.8mm thick test piece cannot be prepared, the minimum thickness allowed is 0.6mm.
9.2 Test equipment
a) The test shall be carried out in an oven as specified in Article 8.1 of GB/T2951.2-1997. The test temperature shall be in accordance with the provisions for relevant materials in the relevant cable product standards.
b) Each test piece is suspended from the upper chuck in the oven, and the lower chuck is used to cool it, and a weight is added to the lower chuck. When the tubular test piece is fixed with the chuck, the two ends of the test piece should not be tightly closed. It can be achieved by any appropriate method, such as inserting a small section of metal needle tube at the end of the test piece, the size of which is slightly smaller than the inner diameter of the test piece
9.3 Test steps
a) The test piece should be suspended in the oven, and a weight is added to the lower chuck. The force generated shall comply with the provisions of the relevant cable product standards for related materials. b) After 15 minutes in the oven, measure the distance between the marked lines and calculate the length ratio. If the oven has no observation window and the door must be opened for splashing, the measurement should be completed within 30 seconds after opening the door. The oven temperature shall comply with the provisions of the relevant cable product standards for related materials. If there is any dispute, the test shall be carried out in an oven with an observation window, and the door shall not be opened for measurement. c) Then release the tension from the test piece (cut the sample at the lower clamp), and allow the test piece to recover for 5min at the specified temperature. Then remove the test piece from the oven. Slowly cool it to room temperature and measure the distance between the marking lines again. 9.4 Evaluation of test results
a) After 15min of load at the specified temperature, the median value of the elongation shall not be greater than the provisions of the relevant cable product standard. b) The median value of the increase in the distance between the marking lines after the test piece is taken out of the oven and cooled shall not be greater than the percentage of the distance before the test piece is placed in the oven. 10 Mineral oil immersion test
10.1 Sampling and sample preparation
GB/T2951.5-1997
Prepare 5 test pieces according to the steps described in Articles 9.2.2 and 9.2.3 of GB/T2951.1-1997. 10.2 Determination of the cross-sectional area of the test piece
See the test method in Article 9.2.4 of GB/T2951.1--1997. 10.3 Test oil
Unless otherwise specified, the mineral oil used shall be ASTM No. 2 oil. It shall have the following properties: Benzene saddle point
Viscosity at -100°C
(93±3)
(20±1)cm
(245±6)
Note: No. 20 engine oil in accordance with GB488 is allowed for non-arbitration tests. 10.4 Test steps
The test piece shall be immersed in an oil bath preheated to the specified test temperature and maintained at this temperature for the specified time. The test temperature and time shall be in accordance with the relevant cable product standards.
After the specified time, remove the test piece from the oil bath, gently wipe off the excess oil, and hang the test piece in the air at ambient temperature for at least 16 hours, but not more than 24 hours, unless otherwise specified in the relevant cable product standards. After this process, gently wipe off any excess oil from the test piece.
10.5 Determination of mechanical properties
See GB/T2951.1--1997 test methods 9.1.6 and 9.1.7. 10.6 Method of expressing test results
Calculate the tensile strength based on the cross-sectional area of the test piece measured before oil immersion (see Article 10.2). The difference between the median values of the mechanical properties of the five test pieces before and after oil immersion (see GB/T2951.1-1997 Article 9.1.2) and the percentage of the median value of the mechanical properties before oil immersion should not be greater than the provisions of the relevant cable product standards. 1) or (100±5)s (Saybolt universal viscometer).1 Sampling, specimen preparation and determination of cross-sectional area Cut two insulation and sheath sections from each test sample, prepare the specimens and measure the cross-sectional area according to the test method specified in Chapter 9 of GB/T2951.1-1997, and then conduct the test. The dumbbell specimen shall be prepared from the inner layer of the insulation and sheath after removing all ridges and/or flat conductive layers. The thickness of the test piece shall not be less than 0.8mm1 and not more than 2.0mm. If a 0.8mm thick test piece cannot be prepared, the minimum thickness allowed is 0.6mm.
9.2 Test equipment
a) The test shall be carried out in an oven as specified in Article 8.1 of GB/T2951.2-1997. The test temperature shall be in accordance with the provisions for relevant materials in the relevant cable product standards.
b) Each test piece is suspended from the upper chuck in the oven, and the lower chuck is used to cool it, and a weight is added to the lower chuck. When the tubular test piece is fixed with the chuck, the two ends of the test piece should not be tightly closed. It can be achieved by any appropriate method, such as inserting a small section of metal needle tube at the end of the test piece, the size of which is slightly smaller than the inner diameter of the test piece
9.3 Test steps
a) The test piece should be suspended in the oven, and a weight is added to the lower chuck. The force generated shall comply with the provisions of the relevant cable product standards for related materials. b) After 15 minutes in the oven, measure the distance between the marked lines and calculate the length ratio. If the oven has no observation window and the door must be opened for splashing, the measurement should be completed within 30 seconds after opening the door. The oven temperature shall comply with the provisions of the relevant cable product standards for related materials. If there is any dispute, the test shall be carried out in an oven with an observation window, and the door shall not be opened for measurement. c) Then release the tension from the test piece (cut the sample at the lower clamp), and allow the test piece to recover for 5min at the specified temperature. Then remove the test piece from the oven. Slowly cool it to room temperature and measure the distance between the marking lines again. 9.4 Evaluation of test results
a) After 15min of load at the specified temperature, the median value of the elongation shall not be greater than the provisions of the relevant cable product standard. b) The median value of the increase in the distance between the marking lines after the test piece is taken out of the oven and cooled shall not be greater than the percentage of the distance before the test piece is placed in the oven. 10 Mineral oil immersion test
10.1 Sampling and sample preparation
GB/T2951.5-1997
Prepare 5 test pieces according to the steps described in Articles 9.2.2 and 9.2.3 of GB/T2951.1-1997. 10.2 Determination of the cross-sectional area of the test piece
See the test method in Article 9.2.4 of GB/T2951.1--1997. 10.3 Test oil
Unless otherwise specified, the mineral oil used shall be ASTM No. 2 oil. It shall have the following properties: Benzene saddle point
Viscosity at -100°C
(93±3)
(20±1)cm
(245±6)
Note: No. 20 engine oil in accordance with GB488 is allowed for non-arbitration tests. 10.4 Test steps
The test piece shall be immersed in an oil bath preheated to the specified test temperature and maintained at this temperature for the specified time. The test temperature and time shall be in accordance with the relevant cable product standards.
After the specified time, remove the test piece from the oil bath, gently wipe off the excess oil, and hang the test piece in the air at ambient temperature for at least 16 hours, but not more than 24 hours, unless otherwise specified in the relevant cable product standards. After this process, gently wipe off any excess oil from the test piece.
10.5 Determination of mechanical properties
See GB/T2951.1--1997 test methods 9.1.6 and 9.1.7. 10.6 Method of expressing test results
Calculate the tensile strength based on the cross-sectional area of the test piece measured before oil immersion (see Article 10.2). The difference between the median values of the mechanical properties of the five test pieces before and after oil immersion (see GB/T2951.1-1997 Article 9.1.2) and the percentage of the median value of the mechanical properties before oil immersion should not be greater than the provisions of the relevant cable product standards. 1) or (100±5)s (Saybolt universal viscometer).1 Sampling, specimen preparation and determination of cross-sectional area Cut two insulation and sheath sections from each test sample, prepare the specimens and measure the cross-sectional area according to the test method specified in Chapter 9 of GB/T2951.1-1997, and then conduct the test. The dumbbell specimen shall be prepared from the inner layer of the insulation and sheath after removing all ridges and/or flat conductive layers. The thickness of the test piece shall not be less than 0.8mm1 and not more than 2.0mm. If a 0.8mm thick test piece cannot be prepared, the minimum thickness allowed is 0.6mm.
9.2 Test equipment
a) The test shall be carried out in an oven as specified in Article 8.1 of GB/T2951.2-1997. The test temperature shall be in accordance with the provisions for relevant materials in the relevant cable product standards.
b) Each test piece is suspended from the upper chuck in the oven, and the lower chuck is used to cool it, and a weight is added to the lower chuck. When the tubular test piece is fixed with the chuck, the two ends of the test piece should not be tightly closed. It can be achieved by any appropriate method, such as inserting a small section of metal needle tube at the end of the test piece, the size of which is slightly smaller than the inner diameter of the test piece
9.3 Test steps
a) The test piece should be suspended in the oven, and a weight is added to the lower chuck. The force generated shall comply with the provisions of the relevant cable product standards for related materials. b) After 15 minutes in the oven, measure the distance between the marked lines and calculate the length ratio. If the oven has no observation window and the door must be opened for splashing, the measurement should be completed within 30 seconds after opening the door. The oven temperature shall comply with the provisions of the relevant cable product standards for related materials. If there is any dispute, the test shall be carried out in an oven with an observation window, and the door shall not be opened for measurement. c) Then release the tension from the test piece (cut the sample at the lower clamp), and allow the test piece to recover for 5min at the specified temperature. Then remove the test piece from the oven. Slowly cool it to room temperature and measure the distance between the marking lines again. 9.4 Evaluation of test results
a) After 15min of load at the specified temperature, the median value of the elongation shall not be greater than the provisions of the relevant cable product standard. b) The median value of the increase in the distance between the marking lines after the test piece is taken out of the oven and cooled shall not be greater than the percentage of the distance before the test piece is placed in the oven. 10 Mineral oil immersion test
10.1 Sampling and sample preparation
GB/T2951.5-1997
Prepare 5 test pieces according to the steps described in Articles 9.2.2 and 9.2.3 of GB/T2951.1-1997. 10.2 Determination of the cross-sectional area of the test piece
See the test method in Article 9.2.4 of GB/T2951.1--1997. 10.3 Test oil
Unless otherwise specified, the mineral oil used shall be ASTM No. 2 oil. It shall have the following properties: Benzene saddle point
Viscosity at -100°C
(93±3)
(20±1)cm
(245±6)
Note: No. 20 engine oil in accordance with GB488 is allowed for non-arbitration tests. 10.4 Test steps
The test piece shall be immersed in an oil bath preheated to the specified test temperature and maintained at this temperature for the specified time. The test temperature and time shall be in accordance with the relevant cable product standards.
After the specified time, remove the test piece from the oil bath, gently wipe off the excess oil, and hang the test piece in the air at ambient temperature for at least 16 hours, but not more than 24 hours, unless otherwise specified in the relevant cable product standards. After this process, gently wipe off any excess oil from the test piece.
10.5 Determination of mechanical properties
See GB/T2951.1--1997 test methods 9.1.6 and 9.1.7. 10.6 Method of expressing test results
Calculate the tensile strength based on the cross-sectional area of the test piece measured before oil immersion (see Article 10.2). The difference between the median values of the mechanical properties of the five test pieces before and after oil immersion (see GB/T2951.1-1997 Article 9.1.2) and the percentage of the median value of the mechanical properties before oil immersion should not be greater than the provisions of the relevant cable product standards. 1) or (100±5)s (Saybolt universal viscometer).
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