Wrap a Cable Joint with Self-Amalgamating Tape
The quality of a self-amalgamating wrap is settled before the last turn goes on. Cleaning, stretch, overlap and anchoring decide whether the tape becomes one mass or a loose stack of ribbons.
Before you start
You need a clean dry substrate, the right roll for the duty, scissors, and somewhere you can work without grit blowing into the wrap. Silicone self-amalgamating tape fuses on contact pressure, so anything loose at the interface stays in the finished joint.
The wrap, step by step
- Clean the substrate and let the solvent flash off completely.
- Position the start of the wrap so the first turn will be covered by the turns that follow.
- Peel back only the length of release film you are about to use.
- Anchor the first turn by tucking it back over itself so it cannot unwind.
- Wrap with the tape elongated, laying each turn at roughly 50 percent overlap on the one before.
- Keep the tension even. A turn that goes on slack is the turn that separates.
- Wrap one full turn past the area being protected at each end.
- Press the finished wrap along its length, then tuck and press the final turn onto the layer below.
- Leave the wrap to settle before the joint is energised or the assembly is flexed.
Checks on the finished wrap
| Check | Pass | Fail |
|---|---|---|
| Layer count over the substrate | At least two layers at every point | Single thickness visible anywhere |
| Surface | Smooth and even | Banding or open gaps |
| Ends | Tucked and pressed onto the layer below | Loose end turns |
| Grip | Wrap cannot be rotated by hand | Wrap turns on the substrate |
| Fusion | Cut and check shows one mass | Separated layers on the cut |
What changes the layer count
Thickness is a property of the wrap, not of the roll. Each half lap pass adds a layer, so the wall builds with the number of passes. Decide the wall the joint needs, then count the passes required to reach it. Silicone grades cover -60°C to +280°C, so the temperature at the hottest point sets the material before the layer count is settled.
Where a sleeve does the job better
If the joint can be opened up, a slip on sleeve is faster and more consistent than a wrap. The wrap earns its place where a sleeve cannot pass, on busbar overlaps, motor end turns and joints assembled in place.
What to send
Send the joint dimensions, the voltage class, the hottest surface temperature and whether the joint is opened on a maintenance cycle. We return the roll and the layer count for it.
Frequently asked questions
Which direction should I wrap?
Work in one direction along the joint and keep going the same way. Changing direction mid wrap leaves turns crossing each other, and the crossings are where the wall ends up uneven.
How many layers do I need?
That follows the wall the joint requires. Each half lap pass adds a layer, so the count comes from the insulation requirement rather than from the roll.
Can I wrap over the existing insulation?
You can wrap a joint that has already been made off, provided the surface is clean, dry and free of oil. A contaminated interface is the most common reason a wrap separates later.
How long before the joint goes into service?
Leave the wrap to settle first. The wrap specification we issue with the roll states the settling time for that grade and joint.
Why did my first turn come loose?
It was probably not anchored. Tuck the first turn back over itself so it cannot unwind, and do the same with the final turn.