Insulcap heat-shrink cable end caps, sealed for burial
IN AIR, SPLASH ZONE, BURIED or SUBMERGED: this is the cap you specify when nobody can promise which of the four bands the cut end will finish in.
Insulcap cable end cap, GEC series
A cross-linked polyolefin cap, moulded closed at one end and lined inside with hot-melt adhesive. Recovered over a cut cable end it bonds to XLPE, PVC, PILC and rubber-sheathed jackets, and the manufacturer publishes the sealed construction as meeting IP68.
- Hot-melt lining bonds to an irregular sheath rather than gripping it
- Sealed construction meeting IP68
- Conductive mastic offered as a lining option
- Custom logo or print applied after shrinking
- Valved (V) and relief-valved (RV) variants ordered against the same GEC codes
| Exposure band | IN AIR through to SUBMERGED |
|---|---|
| Material | Cross-linked polyolefin, hot-melt adhesive lined |
| Size range | GEC 001S to GEC 1101 |
| Cable diameter covered | 2-4 mm (0.08-0.16 in) up to 230-460 mm (9.1-18.1 in) |
| Jackets bonded to | XLPE, PVC, PILC, rubber-sheathed |
| Ingress protection | IP68, sealed construction |
| Shrink temperature | 125°C (257°F) |
| Continuous temperature limit | -40°C to +110°C (-40°F to 230°F) |
| Dielectric strength | 12 kV/mm minimum |
Depth decides the cap before the code does
Put the end on the scale first. A drum in a covered store sits IN AIR and will tolerate almost anything pushed over the end. A drum standing in an open yard is in the SPLASH ZONE. A cable pulled into a duct on Friday and jointed on Monday is BURIED, and a duct that takes water is SUBMERGED. Insulcap is what you specify when the end can travel between those bands without anyone telling you, because the adhesive lining is what carries the IP68 claim past the top of the scale.
Two things happen at once under the torch. The polyolefin is cross-linked, so it holds a memory and recovers onto whatever sits beneath it once the wall passes 125°C (257°F). The lining melts at the same moment and runs into what recovery on its own cannot close: the ridge over an armour bedding, the oval pulled into an over-drummed jacket, the score left by the cutting saw. As the part cools that adhesive sets as one unbroken bead round the full circumference.
The bead is the entire difference. A part described as protecting against moisture may be doing it as a cover, shedding water by shape alone, or as a seal, bonded to the sheath the whole way round; only the second is still working when the end is under water. An unlined push-on cap cannot bridge an irregular jacket at any wall thickness, and the IP68 figure here is a statement about that adhesive bond rather than about the polymer.
Size follows recovered internal diameter, not the conductor area printed on the drum ticket. The supplied bore has to clear the jacket going on and the recovered bore has to sit below it after shrinking, so a code taken at the top of its span never pulls down hard enough for the lining to bridge anything. Measure over the jacket and work from that figure.
Physical properties
| Property | Value | Test method |
|---|---|---|
| Tensile strength | 12 N/mm² (MPa) min. | ASTM D638 |
| Ultimate elongation | 350% min. | ASTM D638 |
| Density | 1.05 ± 0.2 g/cm³ | ASTM D792 |
| Hardness | 45 ± 10 Shore D | ASTM D2240 |
| Water absorption | 0.2% max. | ASTM D570 |
The manufacturer's published values for the cross-linked polyolefin used across the GEC range. What each method in the third column actually demonstrates is set out on what an end-cap datasheet proves.
Thermal properties
| Property | Value | Test method |
|---|---|---|
| Accelerated ageing | 120°C for 500 hrs | ASTM D2671 |
| Tensile strength, aged | 11 N/mm² (MPa) min. | ASTM D638 |
| Ultimate elongation, aged | 300% min. | ASTM D638 |
| Low temperature flexibility, -40°C for 4 hrs | No cracking | ASTM D2671 |
| Heat shock, 250°C for 30 min | No cracking or flowing | ESI 09-11 |
| Shrink temperature | 125°C | IEC 216 |
| Continuous temperature limit | -40°C to +110°C | IEC 216 |
The two retained rows sit directly under the ageing condition they are measured after.
Electrical properties
| Property | Value | Test method |
|---|---|---|
| Dielectric strength | 12 kV/mm min. | ASTM D149 |
| Volume resistivity | 1 × 10¹⁴ ohm.cm min. | ASTM D257 |
| Dielectric constant | 5 max. | ASTM D150 |
What the GEC range covers
One continuous range rather than a family of part families, which is why the ordering conversation is short.
- GEC 001S at the small end to GEC 1101 at the large, covering cable outside diameters from 2-4 mm (0.08-0.16 in) to 230-460 mm (9.1-18.1 in). The manufacturer publishes this as a span and not as a per-size chart, so a code is confirmed against a measured diameter rather than read off a table.
- XLPE, PVC, PILC and rubber-sheathed jackets. The lining bonds to all four, which is why one cap serves a mixed drum yard.
- Conductive mastic is available in place of the standard lining. The manufacturer's own page for the range carries the ordering variants, including the valved (V) build used on pressurised telecom cable, where the cap has to hold pressure in rather than let anything out.
- Custom logo or print, applied so it stays legible once the wall has recovered. That is a despatch and warranty decision rather than a sealing one, and it belongs to tamper-proof end seals.
Four ends that need a different part
An energised end needs the two-stage live cap, where every core is sealed separately before a thick-wall outer cap goes over the assembly. A 33 kV drum sitting in a hot yard needs a vent, because gas evolves inside the cable continuously and a plain sealed cap gives it nowhere to go: that is the relief-valved build. A site working under a no-hot-work restriction needs something that closes without a flame. And an end you intend to reopen shortly still cannot have this cap, because once the adhesive has flowed and set the only way off is to cut it off.
Questions that come up at specification
How hot does the cap actually have to get?
Can a cap be taken off and refitted?
How cold can a capped end go?
Will it seal a jacket that is already damaged?
The drum is going by sea. Is sealing the whole job?
The variants that branch off this cap
Each is the same polyolefin and the same property set, changed in one respect only, so none of them is re-specified here.
- Relief-valved (RV), for a sealed HV end that builds gasGEC 102 RV to GEC 801 RV, cable 12-200 mm. The valve lets gas out above 3 psi and is non-returnable, so nothing travels back in.
- Live, for an end that stays energisedFour GLEC sizes covering 1.5 to 300 sq mm conductor, supplied as a four-piece plus one-piece kit with a flash symbol on the outer cap.
- Tamper-evident, for a length that may be disputedThe same cap, printed in ink that will not come off, used where works, transit and site each claim a different drum length.
- Back up to the cable end cap hubThe five cap types this site covers, compared on torch access, ingress rating, permanence and re-entry.
- The failure this cap is specified againstWater ingress at an irregular sheath, in the SUBMERGED band, where a cap sized at the edge of its recovery range never pulled down.
Getting a GEC code confirmed
Open End does not manufacture, hold stock or quote. Five facts turn an enquiry into one reply instead of six: the measured outside diameter over the jacket, the jacket material, the core count, whether the end will be energised, and the exposure band you expect it to finish in.