Electrical insulating tape

Standard PVC electrical tape is rated around 80 to 105 degrees C for use up to 600 V. Exact values are on the TDS and reel label, often referencing UL 510 or IEC 60454. Hotter locations need glass cloth, polyimide or silicone tape.

Self-amalgamating tape has no adhesive; stretched and overlapped, its layers fuse into a watertight mass. It is used on medium-voltage cable joints and outdoor terminations, then overwrapped with PVC tape for UV protection. It must be stretched to the stated ratio to seal properly.

Colours mark phases, neutral and earth according to national or plant conventions. Under IEC 60445 earth is green and yellow and neutral is blue. Different colours of the same product line carry the same insulation rating.

Usually the service temperature exceeds the rating, or the tape was not tensioned while wrapping. Apply the final wrap without stretch so the end does not pull back. Low-grade tapes with poor plasticisers also ooze in hot, humid conditions.

Stretch the tape moderately and overlap each turn by about half the tape width. Start and finish on intact insulation, with at least two layers over the joint. Apply the final wrap without tension so the end does not lift.

Electrical tape is fast and convenient for repairs, but in the long run it tends to loosen with heat or oil. Heat-shrink gives a firmer, more mechanically durable covering on lugs and permanent joints. For outdoor joints, either is often combined with self-amalgamating tape for waterproofing.

Keep rolls cool and out of sunlight and high heat, which soften the adhesive and push it out at the roll edges. Do not leave rolls in vehicles or hot panels for long periods. Storing rolls flat in a box keeps the edges from deforming.

Standard PVC tape is for low voltage only, typically up to about 600 V. Medium voltage joints and terminations require dedicated kits with semi-conductive tape, rubber tape and protective layers fitted per the maker's instructions. This work needs suitably certified electricians.