Heat shrinkable tube connection cable technology and its high pressure detection
作者:admin 新闻来源:深圳市普瑞曼材料科技有限公司 添加时间:2017-07-10
Abstract: Heat shrinkable tubes have been widely used to monitor the connection of observation cables, but the connection technology and the connection effect, especially the high pressure resistance test. Through the high-pressure test of the cable heat-shrinkable pipe joint, the technology and effect of the heat-shrinkable cable connection are summarized.
Key words: heat shrinkable tube; cable connection; high pressure test
1 questions raised
The quality of the cable connection is one of the important links to ensure the long-term operation of the instrument monitoring equipment. Although the monitoring equipment can not ensure any quality problems before it is embedded, the instrument still Can not work long term, so the cable connection quality difference often become an important reason for instrument failure.
Heat shrinkable tube is a kind of special plastic which is made of polyethylene as the main raw material and processed by multi-channel process (including radiation modification process). Because it has a fun "memory effect" phenomenon (when heated to a certain temperature will shrink to the initial shape), it is widely used in electric power, communications and other engineering fields in the wire, connector insulation protection. It is not only suitable for hydraulic cable, but also for shielded cable, and simple operation, can greatly improve the efficiency of the site connection is more subject to the constraints of less construction conditions. However, the anti-seepage and insulation performance of the cable heat-shrinkable fittings is very important, especially in high water pressure environments. The quality supervision of the on-site cable is based on the high pressure test of the cable joint.
2 high pressure test
2.1 Test principle
Cable cable connection shown in Figure 1, cable connection shown in Figure 2. The resistance of the same cable core is called the breaking resistor, and the resistance between the core and the core is called the insulation resistance. In the high-pressure container, if the heat-shrinkable tube does not have impermeability, the water will soak the cotton floc, the broken-off resistance of the core will decrease; if the heat-shrinkable tube does not have insulation performance, the insulation resistance between the core If the breaking resistance and insulation resistance values are> 50MΩ, then the cable heat pipe fittings to high pressure environment with anti-seepage and insulation performance.
2.2 Test equipment and tools
Pressure gauge tank, manual test pump, 0.4 standard pressure gauge, 100V DC Megohmmeter, rasp, wire stripper, 100 W electric iron, 700 W plastic welding gun, 20m cable, different diameter heat pipe.
2.3 cable connection
2.3.1 core connection
Special tools to strip a certain length of the cable core and core copper wire, and to ensure that the core and copper wire from damage. Core copper wire exposed about 1cm, the core is not solder, with heat shrink tubing connection, between the two core lines at the opening of the cotton filling, and make it close, see Figure 1.
Heat shrinkable tube connection cable technology and its high pressure detection
2.3.2 Cable connection
(D is the cable diameter), the heat shrink tube heat shrink and then put the same or slightly larger diameter heat shrink tubing , Forming a double heat shrinkable joint, see Figure 2. Measure and record the breaking resistance of each core, cable connection parameters in Table 1.
Heat shrinkable tube connection cable technology and its high pressure detection
Heat shrinkable tube connection cable technology and its high pressure detection
2.3.3 Connection process
(1) according to the length of the cable connector to cut a good heat shrink tube, and has been set in the cable.
(2) in the core line put on the middle of the tampon group filled with heat shrink tube, so that the core wire contact with cotton, heat shrink tube heat shrink.
(3) the core and together, with the insulating tape bandage, bandage lap in turn followed by, and forced to stretch the tape, while pulling edge wrapped, so that the thickness of the same size and cable, air.
(4) will connect the location of the satin surface of the hair, and wipe with a silk cloth wipe dry.
(5) the connection section of the cable heated to slightly fused state, immediately adhere to the hot melt film.
(6) with 700W plastic welding torch from the middle of the heat shrink tube to the two uniform heating, to avoid the concentration of heat, and pay attention to control the heating time, and gradually out of the air, when the film has a melting spill phenomenon to stop heating, closed ends.
(7) the cable connection is completed after the natural cooling, and detection of insulation resistance, if not meet the requirements, re-connected.
2.4 Test process
The YBG-2 pressure calibration tank was used for the test equipment. Test with a range of 500MΩ megger measuring each core breaking resistance and insulation resistance between the core. During the test, observe the water seepage of the cable. Test the maximum pressure of 7MPa.
Select three connected cable glands (two 4-core hydraulic cables, one four-core shielded cable) and one complete four-core shielded cable into the pressure tank and install the pressure tank. Then press the pressure tank, the maximum pressure of 7MPa. Before and after the pressure measurement of the core of the broken resistance and insulation resistance, pressure every 2h after reading the core of the broken resistance and insulation resistance and record, 24h after the day measured 1 ~ 2 insulation resistance and off Open resistance. The test lasted for 15 days. During the pressure tank pressure changes with the temperature slightly up and down, when the pressure <6.9MPa, immediately fill the pressure to ensure that the pressure at 7MPa. Test the process of measuring several times a day, and observe the status of the cable exposed port, check whether the phenomenon of seepage.
2.5 Test results
Test results from the test point of view, 15d within the four-core shielded cable core breaking resistance and insulation resistance between the core before and after the pressure are> 500MΩ, four-core hydraulic cable insulation resistance before and after > 500MΩ, see Table 2.
Heat shrinkable tube connection cable technology and its high pressure detection
The breaking resistance of the core wire of the four-core hydraulic cable is obviously reduced after pressurization, but both are> 180MΩ, which are basically stable during the continuous pressurization process and only change with the change of the pressure. After the end of the pressure release, the breaking resistance of each core wire is returned to the initial value (500MΩ or more). The breaking resistance is significantly reduced after pressurization, and the analysis is considered to be caused by a pressure that causes the distance between the wires of the broken core to be shortened. Figure 4 and Figure 4b, in order to distinguish clearly, in Figure 4a and Figure 4b where the resistance test> 500MΩ to 700MΩ said. The resistance of the four-core hydraulic cable breaking resistor before and after the resistance curve shown in Figure 4a and Figure 4b.
Heat shrinkable tube connection cable technology and its high pressure detection
Heat shrinkable tube connection cable technology and its high pressure detection
3 Conclusion
The test results show that the thermal connector connection cable connector in the connection quality assurance under the premise of 7MPa in the water pressure working conditions, whether it is hydraulic cable or shielded cable insulation resistance can reach more than 500MΩ, insulation performance to meet the specifications > 50MΩ; can also ensure that the water pressure in the 7MPa for a long time without seepage, anti-seepage effect can meet the design and specification requirements.
Heat shrinkable tube heat shrinkable cable connector on the connection cable process requirements are very high, in the cable connection construction should strengthen the quality control, in particular, should pay attention to: ① contact with the heat shrink tube part of the cable must be dimmed and alcohol and other clean, and should First heated to the micro-melting state, the film stick to the cable to enhance the film and cable adhesion; ② film width as much as possible, at least ≥ 20mm.