Insulation Shrinkage
Thermal FOR: Insulation $1,570When wire/cable insulation shrinks, the insulation can pull back from a wire termination location. If the wire/cable termination is intended to be environmentally sealed, the insulation shrinkage can create the potential for exposed conductor which may lead to shorting or arcing. In operational environments, insulation shrinkage may also create splits in the wire/cable insulation caused by mechanical stress as the insulation material contracts.
The insulation shrinkage test objective is to evaluate the propensity of a wire or cable’s insulation to shrink with exposure to elevated temperature. The pass/fail criteria for this tests is wire specification specific, but will often only allow for a very small change.
Procedure
- Perform visual examination of the specimen. Record any observed defects.
- Remove a short length of wire insulation from both ends of the specimen.
- Measure the exposed conductor length.
- Place the specimen into an oven set to a temperature above the specimen rating (typically 20 - 50C above temperature rating).
- After the specified elevated temperature exposure time, remove the specimen.
- Measure the exposed conductor length.
- Report the insulation shrinkage, elevated temperature exposure duration and temperature, and any observed defects.
Covered specifications
- AS22759 Method 5.3.12
- AS4374 Method 104
- AS5382 Method 5.6.7
- AS81044 Method 4.7.5.13
- AS85485 Method 5.22
- EN3475 Method 402
- MIL-DTL-24643 Method 4.8.30
- MIL-DTL-49055 Method 4.7.18
- MIL-M-24041 Method 4.7.3.1
- ISO 6722 Method 5.16
- 40M39513 Method 4.5.9
- AS4373 Method 108
- IEC 60811-1-3 Method 11
- MIL-DTL-24643D Method 4.8.29
- MIL-M-24041 Method 4.7.3.01
- MIL-PRF-85045G Method 4.7.5.17
- NEMA HP-3 Method 6.1.5