Notch Propagation
Mechanical FOR: Insulation $980The notch test examines the propagation of a nick in the top layer of a wire. Small notches are common during installation or maintenance of wires, and this test evaluates how well the insulation can withstand mechanical stresses after incurring a notch. A pass condition for this test is if, after notching and wrapping, the conductor is not visible. Any indication of exposed conductor is deemed as a failure.
Wire constructions with multiple insulation layers often perform very well in this test as the notch will typically not propagate to the other layers. Single insulation layer constructions, and in particular the extruded single layer constructions, tend to perform the worst in these tests.
Parameters that can be modified for this test:
- Notch tool depth
- Number of wrap cycles
- Use of dielectric voltage withstand test to determine pass/fail criteria
Procedure
- Perform a visual examination of the specimen. Record any observed defect.
- Verify that the depth of notching tool matches the specification.
- Draw notching tool across the specimen creating a notch.
- Wrap the specimen back and forth the specified number of times on a mandrel of specified diameter.
- Visually examine the specimen and determine if the conductor has been exposed.
- Report the notch tool depth and number of cycles until the conductor was exposed (or if not exposed).
Covered specifications
- AS4373 Method 706
- EN3475 Method 502
- BSS7324 Method 7.38
- EN50305 Method 5.3