Heating and shrinking instructions for heat shrinkable pipes and installation requirements for power cable accessories
1. All heat shrink tubing are made of macromolecule materials by special technology. When the temperature reaches 110 ~130 ~C, the materials begin to shrink, and the shrinkage rate is more than 50%. Material will not be affected in a short time at 140 C, but the material will be damaged or even burned by local long time high temperature overheating, which will affect the performance of the material.
2. Propane spray gun is recommended for heating tools. The flame has moderate yellow temperature, large heating area and high temperature of blue flame of gasoline. It is necessary to keep away from material properly, control temperature and avoid burning.
3. In order to ensure the tight bonding and bonding strength between the heat shrinkable tube and the coating material, the coating area and the bonding sealing section should be preheated before being inserted into each layer of pipe fittings, and then cleaned with cable cleaning paper. Removal of pyrotechnic deposits from flames and good contact between layers.
4. When starting to shrink the tube, the flame should approach slowly, move around it to ensure that the radial shrinkage is uniform, and then slow down the expansion of the heat shrinkage tube. The flame is in the direction of shrinkage to preheat the tube, which is conducive to uniform shrinkage. Following the initial contraction position and direction recommended in the installation procedure, contraction from bottom to top is conducive to excluding gas and enhancing sealing.
5. The contracted pipe should be smooth and wrinkle-free, and its original structure outline can be clearly seen. A small amount of sealant is extruded in the sealing part, which indicates that the sealing is perfect.
Heat shrinkable power cable accessories are divided into outdoor terminal, indoor terminal and intermediate connection, outdoor terminal refers to open-air cable connector, indoor terminal refers to cable and electrical equipment connection; intermediate connection is divided into two types: direct connection and transitional connection. Two cables with the same type of insulation structure are connected to each other in a direct way, and two cables with different types of insulation structure are connected to each other in a transitional way. The following are some installation conditions and requirements for thermal shrinkable power cable accessories:
1. Installation of heat shrinkage accessories should be at ambient temperature above 0 C and relative humidity below 70%. To avoid dew and damp on insulating surface, remedial measures should be taken when ambient temperature is low and humidity is too high.
2. When the heat shrinkable intermediate connector is not completely cooled, it is not allowed to move the cable.
3. Damage to cable sheaths and insulation is strictly prohibited during construction.
4. The parts (such as lead bag and terminal) where the heat shrinkable accessories are in contact with metal parts and sealed should be carefully groomed and cleaned with detergent.
5. In the position of the cable end, the core should be avoided to dislocate, so as not to affect the sealing effect.
6. Don't cut the heat shrinkable pipe at will.
7. It can't be constructed in rainy and foggy weather. Remedial measures should be taken if cable is found to be in water or damp.
At present, thermal shrinkable cable accessories have been rapidly promoted and widely used. The fabrication quality of thermal shrinkable cable terminal and cable intermediate terminal is particularly important. First of all, there are strict requirements for cleaning work. When making high temperature shrinkable pipes with good environment, we should use absolute alcohol to clean every process in the manufacturing process. Especially at the Trident after welding ground wire, we should carefully clean the remaining welding slag and the carbon deposited after using the blowtorch lamp. In addition, we should pay attention to the operation, and do not wear impurities of unclean gloves, such as hot sweating, to pay more attention to it. No sweat on hands and face is contaminated on cable accessories to ensure that every process of production is kept clean.
Attention is paid to the reasons for the above cleaning work: the cable head is often manufactured in the open air, harmful dust in the air is easily contaminated to the thermal shrinkable cable accessories and the semiconductor and insulation layer of the cable. Carbon deposits left when welding ground wire, stripping semiconductor layer or using blowtorch, etc. If we do not pay attention to cleaning during the production process, dust and Coke will be combined with shrinkable parts, which will cause creeping discharges at the interface of cable accessories and lead to longitudinal breakdown of cable insulation.