Cold shrink tubes are very convenient to install on cables without heating, and are welcomed by power installation companies and communication base station installation related companies, such as cold shrink cable terminals, cold shrink intermediate joints, EPDM cold shrink tubes, silicone cold shrink tubes, cold shrink tubes with glue, etc.

For friends who are new to cold shrink tube products, they will encounter the problem of selecting heat shrink tube models. Today, I will talk about the key points of cold shrink tube caliber selection.

The finished cold shrink tube is composed of an external rubber cold shrink tube body and an internal support strip. The external rubber tube is pre-expanded. The expanded rubber tube is in an activated state of molecular structure at room temperature. When the expansion external force does not exist, the cold shrink tube will automatically shrink and approach the state before expansion. Therefore, the role of our support strip is to provide a continuous external force to keep the rubber tube in a state of force balance after expansion, so that the cold shrink tube is made. When we use the cold shrink tube, gently extract the remaining strip, and the cold shrink tube begins to shrink and wrap around the cable, playing a good role in insulation and sealing protection.

In terms of the diameter of the cold shrink tube, we can draw several key points from the above description:

First, the inner diameter of the cold shrink tube after shrinkage is close to the size before expansion, and it cannot be guaranteed to be completely retracted. In fact, if the diameter of the cold shrink tube before shrinkage is D, when the cold shrink tube is extracted, the cold shrink tube will quickly shrink to a diameter D', which is generally about 20%-30% larger than the diameter D1 before expansion. Then D' will slowly shrink to D1 over a long time. The main principle is 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', this shrinkage stress slows down the shrinkage speed and can be almost ignored. Therefore, we generally need to use D' as the minimum application inner diameter of the cold shrink tube. At the same time, D' is not the final inner diameter of the cold shrink tube after shrinkage. The final diameter changes dynamically and is related to the environment. Under natural shrinkage, this inner diameter is between D1 and D', and it is best to be larger than D', so that the cold shrink tube has sufficient holding force, so that the installation quality will be better. Therefore, before selecting a model, you can know which model to choose by asking the supplier about the D' value. In particular, it should be reminded that the cold shrink tube products of different materials and specifications are quite different and cannot be estimated at will. For example, the wall thickness of the high-voltage cold shrink intermediate joint is particularly thick, and the shrinkage ratio and deformation are very different from those of the cold shrink insulation tube.

Secondly: For the inner diameter D before shrinkage, this determines the maximum application inner diameter D'' of the cold shrink tube. The maximum inner diameter needs to consider more factors. The maximum outer diameter of the protected cable should be considered, and the construction margin should be considered. Generally, about 20% should be reserved. Of course, this margin can be adjusted according to the actual situation. For example, if the construction is not very convenient, high-altitude installation, etc. require a large margin, otherwise it is inconvenient to wear the set. In addition, if the margin itself is not too large, the thickness of the support strip should be considered, which varies from about 1 to 3 mm.