How should dielectric-strength testing be specified for commercial heating elements?

Specify dielectric-strength testing from the actual duty, not the catalogue alone. Agree on test voltage (commonly 2U+1000 V or per contract), leakage-current limit, ramp rate, and duration of 1 minute or 1 second, stating whether the element is cold or hot. Pass/fail means no breakdown or flashover, with insulation resistance recorded alongside. Sheath diameter, material, sealing, and terminal geometry set creepage distance; higher watt density warrants a stricter threshold. Retain per-batch readings and inspect terminals, insulation, and seals for damage before release.