Cold-shrinkable tubes can be easily installed on cables because they do not require heating, and are welcomed by the majority of power installation companies and communication base station installation related companies, such as cold-shrinkable cable terminals, cold-shrinkable intermediate joints, EPDM cold-shrinkable tubes, silicone cold-shrinkable tubes, With glue cold shrink tube, etc.
For those who are new to cold-shrinkable tube products, they will encounter the problem of choosing the type of heat-shrinkable tube. Today, I will tell you the key points of choosing the diameter of cold-shrinkable tube.
The finished cold-shrinkable tube is composed of an external rubber material cold-shrinkable tube body and an internal support strip. The external rubber tube is pre-expanded. The expanded rubber tube is in an activated state due to its molecular structure at room temperature. When there is no external force for expansion , the cold shrinkable tube will automatically shrink, close to the state before expansion. Therefore, the function of our support strip is to provide a continuous external force, so that the rubber tube is always in a state of force balance after expansion, so that the cold shrinkable tube is completed. When we use the cold-shrinkable tube, gently extract the remaining draw strip, the cold-shrinkable tube begins to shrink, wraps it on the cable, and plays a good role in insulating and sealing protection.
In terms of the diameter of the cold shrinkable tube, we can draw several key points from the above description:
First of all, the inner diameter of the cold shrinkable tube after shrinking is close to the size before expansion, which cannot ensure complete retraction in place. In fact, if the diameter of the cold shrinkable tube before shrinking is D, after the cold shrinkable tube is extracted, the cold shrinkable tube will quickly It shrinks to a diameter D', which is generally about 20%-30% larger than the diameter D1 before expansion. Then D' will slowly retract to D1 for a long time. This principle is mainly that the shrinkage internal stress in the rubber tube after expansion decreases rapidly as the diameter becomes smaller. When it reaches a certain critical value D', the shrinkage stress Let the contraction speed be slow, almost negligible. Therefore, we generally need to use D' as the minimum inner diameter of the cold-shrinkable tube. At the same time, D' is not the final inner diameter of the cold-shrinkable tube after shrinking. The final diameter changes dynamically and is related to the environment. In the case of natural shrinkage, this inner diameter It is between D1 and D', preferably larger than D', so that the cold shrinkable tube has enough clamping force, so that the installation quality will be better. Therefore, before selecting a model, ask the supplier of the D' value to know which one should be selected. In particular, it should be reminded that cold-shrinkable tube products of different materials and specifications are quite different and cannot be estimated at will. For example, the wall thickness of the high-pressure cold-shrinkage intermediate joint is particularly thick, and the retraction ratio and deformation are very different from cold-shrinkable insulating tubes. big difference.
Secondly: For the inner diameter D before shrinkage, this determines the maximum application inner diameter D'' of the cold shrinkable tube. The maximum inner diameter needs to be considered relatively more factors, the maximum outer diameter of the protected cable should be considered, and the construction allowance should be considered. Generally, it is necessary to leave About 20%, of course, this margin can be adjusted according to the actual situation. For example, the construction is not very convenient, and the high-altitude installation requires a large margin, otherwise it is inconvenient to wear the sleeve. In addition, if the margin is not too large, the thickness of the support bar should be considered, ranging from about 1-3mm.