General Purpose (Single Wall)
A: Heat shrinkable tubing, or heat shrink, is typically available in a ratio between 2:1 and 4:1, meaning the tubing has been expanded to twice or four times its fully recoverable size, respectively. Once heat is applied, tubing will contract tightly around all interior components. When choosing an adequate heat shrink ratio for coverage, one must consider the size of the underlying materials being covered—the larger the bundle, the larger the shrink ratio required. Prior to heat application, tubing must encase all wiring to result in the highest degree of wire insulation.
- - At a ½ inch, a 2:1 heat shrink ratio will recover to ¼ inch, resulting in 50% shrinkage
A: The stated ratio of heat shrink, such as 3:1, means that the tube has been expanded to three times its fully recoverable size. Once heat is applied, tubing will contract tightly around all interior components and "recover" the interlaying space.
For example, a 3:1 heat shrink ratio will recover to ¼ inch of a ¾ inch bundle, resulting in 67% shrinkage. Further, most heat shrink tubing will shrink in length, "longitudinally," around 5-15%; it is therefore important to measure enough tubing to cover the full length of the exposed area after heating.
- Step 1. Measure the diameter of the wire being covered to determine the necessary shrink-ratio of tube to affix over the wire. The shrunken diameter should be slightly smaller than the diameter of the wire being covered to ensure a tight fit. The "shrink ratio" of heat shrink tube indicates how much the tubing will shrink after heating. For example, a length of 2:1 ratio tubing with a diameter of 2 mm will shrink to a diameter of 1 mm.
- Step 2. Measure and cut your heat shrink tubing to ensure that it is longer than the ends being covered. Remembering that heat shrink can shrink in length longitudinally up to 15%, it is always a good insurance policy to leave an extra margin on either end.
- Step 3. Affix the tubing so that it covers the exposed or damaged ends of the wire. Apply indirect heat evenly back and forth across heat shrink tubing until the tube is tightly secured to the wire.