GCB · Insulcore semi-conductive
Semi-conductive breakouts for belted PILC
Four sizes, all of them three-core. The chart runs from 55 mm recovering to 20 mm, up to 140 mm recovering to 56 mm.
Two jobs in one moulding
You pick this family on the cable's construction, not on its voltage. Belted PILC carries no per-core screen inside the belt insulation, and that absence is the published reason the part exists.
So the moulding is given two jobs where a plain breakout has one. It seals the crutch area, and it provides individual screening to each core.
The second job belongs to the material. Body and legs are cross-linked semi-conductive polyolefin, so the recovered part carries a conducting surface onto each leg instead of an insulating one.
The lining changes with it: water-resistant red mastic here, hot melt adhesive on the low-voltage family. The red shows inside every leg mouth on the manufacturer's photograph.
Insulcore semi-conductive breakout, GCB series
A moulded heat-shrink breakout in cross-linked semi-conductive polyolefin, for the crutch of three-core belted PILC. It seals the crutch and screens each core individually. Four catalogued sizes, shrinking at 125 °C. Manufactured by Gala Thermo Shrink Pvt. Ltd.
- Seals the crutch area and screens each core individually, on cable with no per-core screen of its own
- Lined with water-resistant red mastic, not the hot melt adhesive used on the low-voltage family
- IP68 is stated against this part on the manufacturer's product page; the datasheet prints water absorption instead
- After 500 hours at 120 °C the sheet still requires 11 N/mm² tensile strength and 250% elongation
| Cores | 3, on all four codes |
|---|---|
| Codes | GCB-0820, GCB-1330, GCB-2145 N, GCB-2755 |
| Widest body, s → f | 140 mm → 56 mm, GCB-2755 |
| Tightest leg, s → f | 25 mm → 8 mm, GCB-0820 |
| Material | Cross-linked semi-conductive polyolefin |
| Lining | Water-resistant red mastic |
| Volume resistivity | 1 × 10⁷ ohm.cm |
| Shrink temperature | 125 °C |
| Continuous temperature limit | −40 to +100 °C |
| Tensile strength | 12 N/mm² minimum |
| Ultimate elongation | 300% minimum |
| Density | 1.10 ± 0.2 g/cm³ |
| Hardness | 45 ± 10 Shore D |
| Water absorption | 0.5% maximum |
| Voltage class | None printed on the sheet |
Selection chart, GCB-0820 to GCB-2755
| Code | Cores | Body D, s → f | Leg d, s → f | Body L, s → f | Leg l, s → f | Tb | Tc |
|---|---|---|---|---|---|---|---|
| GCB-0820 | 3 | 55 → 20 | 25 → 8 | 160 → 188 | 52 → 62 | 3.3 | 2.7 |
| GCB-1330 | 3 | 80 → 30 | 36 → 13 | 185 → 215 | 60 → 75 | 3.6 | 3.3 |
| GCB-2145 N | 3 | 113 → 45 | 57 → 21 | 247 → 215 | 70 → 85 | 2.1 | 3.1 |
| GCB-2755 | 3 | 140 → 56 | 68 → 29 | 200 → 250 | 75 → 90 | 3.5 | 3.9 |
All dimensions in mm. The band a code takes lies between its two diameter figures.
The letters on this chart, as the sheet prints them
- D
- Internal diameter of the body.
- d
- Internal diameter at each leg.
- s
- As supplied. A minimum, on both diameter columns.
- f
- After free recovery. A maximum, on both diameter columns.
- L and l
- Length of body and of leg. Printed as minimums.
- Tb and Tc
- Thickness of body and of core, to ±10%.
- Not the boot convention
- Boot charts here use a and b. Breakout charts use s and f. Same idea, different letters, and the two are set out at boot, breakout, shroud, sleeve.
Minimum or maximum? The one figure that decides this part
Both published sources give the volume resistivity as 1 × 10⁷ ohm.cm, and they disagree on which way the limit runs. The datasheet prints it as a maximum. The manufacturer's product page for the same part prints the same figure as a minimum. A ceiling is what makes a material semi-conductive, and the two insulating breakouts in the same catalogue carry 1 × 10¹⁴ as a floor, so this site follows the datasheet. On a purchase where the screening function is the reason for the order, that direction is worth having in writing.
Four cells where the chart and the web page differ
The chart above follows the datasheet. The manufacturer's product page prints the same four codes with four figures changed. GCB-1330 core thickness reads 3.7 rather than 3.3. GCB-2755 reads legs of 70 mm recovering to 28 mm rather than 68 mm to 29 mm, body thickness 4.6 rather than 3.5, and core thickness 3.4 rather than 3.9. The material table diverges too, at 350% elongation and +110 °C against 300% and +100 °C on the sheet. The four body diameters agree everywhere, so the size a cable selects is not in dispute.
Physical properties
| Property | Value | Method |
|---|---|---|
| Tensile strength | 12 N/mm² (MPa) min. | ASTM D638 |
| Ultimate elongation | 300% min. | ASTM D638 |
| Density | 1.10 ± 0.2 g/cm³ | ASTM D792 |
| Hardness | 45 ± 10 Shore D | ASTM D2240 |
| Water absorption | 0.5% max. | ASTM D570 |
Water absorption on this family is 0.5% max. The low-voltage breakout in the same catalogue is specified tighter, at 0.2% max.
Thermal properties
| Property | Value | Method |
|---|---|---|
| Accelerated ageing | 120 °C for 500 hours | ASTM D2671 |
| Tensile strength after ageing | 11 N/mm² (MPa) min. | ASTM D638 |
| Ultimate elongation after ageing | 250% min. | ASTM D638 |
| Heat shock, 250 °C for 30 minutes | No cracking or flowing | ESI 09-11 |
| Shrink temperature | 125 °C | IEC 216 |
| Continuous temperature limit | −40 to +100 °C | IEC 216 |
The two ageing rows are what the material must still meet after 500 hours at 120 °C, not what it leaves the factory at.
Electrical properties
| Property | Value | Method |
|---|---|---|
| Volume resistivity | 1 × 10⁷ ohm.cm max. | ASTM D257 |
One row, and that is the whole electrical section of the sheet. The low-voltage and non-tracking sheets each add dielectric strength and dielectric constant here.
Fitting an insulating breakout here is a specification error, not a saving
The insulating families are specified at 1 × 10¹⁴ ohm.cm and this one at 1 × 10⁷. Seven orders of magnitude separate them, and that gap is the entire part.
A stripped crutch will not tell you which family is correct, because the three share diameters almost exactly. At the 20 mm recovered size the codes are GCB-0820 at 55 mm, GAB-0820 at 60 mm and LV3GBB-0820 at 60 mm.
So an insulating breakout goes on cleanly, recovers cleanly and looks finished, having deleted a function the cable relied on. The outside of the joint carries no trace of that.
Which construction you have is a cable question and it belongs before the order, settled against the cable type rather than against a diameter measured at the crutch.
Three heat-shrink breakouts, one crutch
The three families share the geometry and split on material. The last row is the one that matters: at the same recovered diameter, all three fit.
| Insulcore-LV | Insulcore-NT | Insulcore semi-conductive | |
|---|---|---|---|
| Codes | LV2GBB to LV7GBB | GAB-0820 to GAB-3060 | GCB-0820 to GCB-2755 |
| Cable | 2 to 7 core PVC, XLPE, rubber, PILC | 3-core PVC and PILC | 3-core belted PILC |
| Voltage printed | Up to 3.3 kV | Up to 36 kV | None |
| Volume resistivity | 1 × 10¹⁴ ohm.cm | 1 × 10¹⁴ ohm.cm | 1 × 10⁷ ohm.cm |
| Lining | Hot melt adhesive | Water-resistant mastic | Water-resistant red mastic |
| Density | 1.05 ± 0.2 g/cm³ | 1.15 ± 0.2 g/cm³ | 1.10 ± 0.2 g/cm³ |
| Three-core sizes | 15 | 9 | 4 |
| Code at 20 mm recovered | LV3GBB-0820, 60 → 20 mm | GAB-0820, 60 → 20 mm | GCB-0820, 55 → 20 mm |
What the semi-conductive sheet does not publish
No voltage class. The low-voltage sheet prints 3.3 kV and the non-tracking sheet prints 36 kV; this one prints neither, so the class has to come from the manufacturer. No core count other than three, on any of the four codes. No dielectric strength and no dielectric constant. And no explanation of the N suffix on GCB-2145 N, the only code in the family carrying one.
Asked about the semi-conductive family
Will a low-voltage breakout fit where a GCB is specified?
Is there a semi-conductive breakout for four-core or seven-core cable?
What voltage is this family rated for?
Why does GCB-2145 N show a body length falling from 247 mm to 215 mm?
Does it restore earth continuity across the crutch?
Confirm the construction before the size
An enquiry that names the cable as belted PILC lands on this chart. One that says only PILC lands on three of them. Add the sheath diameter at the crutch and one core diameter just past it, and a code comes back in one reply.