GAT series · QR 1021
Anti-tracking tube: a surface problem, not a wall problem
Seven normal-wall sizes from GAT 25/8 to GAT 100/38 at 2.5 to 3.0 mm recovered wall, then eight heavy-wall sizes to GAT(HW) 140/50 at a flat 5 mm. Wall is not the figure that resists tracking.
Adding wall does not stop tracking
Leakage current dries a damp surface in patches and the dry bands arc. Each arc leaves carbon, the marks join, and a face that was insulating an hour ago now conducts.
That is as much mechanism as a specification needs; the compound side sits on polyolefin, PVC, EPDM and silicone. The damage grows on the outer face, and the bulk of the wall takes no part in it.
Read the two charts as one compound in two thicknesses. Going from 3.0 mm to the heavy wall's 5 mm buys mechanical margin on a larger joint, not tracking margin. Pick the compound first and the diameter second.
Anti-tracking tube — GAT and GAT (HW)
Non-tracking cross-linked polyolefin for insulating medium-voltage cable joints and terminations to 36 kV. Two charts: GAT normal wall on 15 and 30 m spools, GAT (HW) heavy wall in cut lengths to 1.5 m.
- Anti-tracking performance and erosion resistance
- Halogen free, flame retardant
- Weather and UV resistance
- Resists chemicals, solvents, corrosion and fungus
- Custom dimension, thickness, length and colour on request
| Supplied ID | 25 to 100 mm (GAT), 25 to 140 mm (HW) |
|---|---|
| Recovered ID | 8 to 38 mm (GAT), 8 to 50 mm (HW) |
| Recovered wall | 2.5 to 3.0 mm (GAT), 5 mm (HW), both ±10% |
| Voltage envelope | MV joints and terminations to 36 kV |
| Continuous limit | -40 to +100 °C |
| Qualification report | QR 1021 |
Selection chart — GAT, normal wall
| Code | D min. (mm) | d max. (mm) | T ±10% (mm) | Spool length (m) |
|---|---|---|---|---|
| GAT 25/8 | 25 | 8 | 2.5 | 30 |
| GAT 35/12* | 35 | 12 | 2.7 | 30 |
| GAT 45/16* | 45 | 16 | 3.0 | 30 |
| GAT 55/20* | 55 | 20 | 3.0 | 30 |
| GAT 65/25 | 65 | 25 | 3.0 | 15 |
| GAT 75/28 | 75 | 28 | 3.0 | 15 |
| GAT 100/38 | 100 | 38 | 3.0 | 15 |
D is the inside diameter as supplied, d the inside diameter after free recovery, T the recovered wall. Three codes carry an asterisk with no legend beside it; the manufacturer's GMW/GHW chart uses that mark for new sizes.
Selection chart — GAT (HW), heavy wall
| Code | D min. (mm) | d max. (mm) | T ±10% (mm) | Length max. (m) |
|---|---|---|---|---|
| GAT(HW) 25/8 | 25 | 8 | 5 | 1.5 |
| GAT(HW) 35/12 | 35 | 12 | 5 | 1.5 |
| GAT(HW) 55/18 | 55 | 18 | 5 | 1.5 |
| GAT(HW) 65/25 | 65 | 25 | 5 | 1.5 |
| GAT(HW) 85/30 | 85 | 30 | 5 | 1.5 |
| GAT(HW) 100/38 | 100 | 38 | 5 | 1.5 |
| GAT(HW) 120/45 | 120 | 45 | 5 | 1.5 |
| GAT(HW) 140/50 | 140 | 50 | 5 | 1.5 |
Cut lengths to 1.5 m, not spools, and one wall for every size. Two gaps against the normal-wall chart matter when you substitute: there is no HW 45/16 or 75/28, and HW 55/18 recovers 2 mm tighter than GAT 55/20.
Thermal and electrical properties
| Property | Value | Method |
|---|---|---|
| Track, erosion or flame failure | None up to 3.25 kV for 20 min | ASTM D2303 |
| Dielectric strength | 15 kV/mm (min.) | ASTM D149 |
| Volume resistivity | 1 x 10¹⁴ Ohm.cm (min.) | ASTM D257 |
| Dielectric constant | 5 (max.) | ASTM D150 |
| Shrink temperature | 125 °C | IEC 216 |
| Continuous temperature limit | -40 to +100 °C | IEC 216 |
| Heat shock, 250 °C for 30 min | No cracking or flowing | ESI 09-11 |
From the sheet's own technical specification. The physical rows — tensile, elongation, hardness, water absorption — are on the datasheet and are not repeated here.
Specify the non-tracking compound when
Each of these is about the surface, not the voltage.
- The insulated face meets open air, so it wets, dries and collects deposits between energisations.
- This layer is the outermost one. Nothing covers it, and neither the sheet nor either product page prints a layer order — confirm yours against the kit instructions.
- The specification wants halogen free and flame retardant on the same part that insulates to 36 kV.
- Salt, chemicals, solvents, corrosion or fungus are in the air at that site; the sheet claims resistance to all of them, and to weather and UV.
- Service stays inside -40 to +100 °C. That is 10 °C tighter than GMW/GHW, so a hot enclosure can rule GAT out before tracking is argued at all.
Against the heavy-wall tube it gets confused with
Both are cross-linked polyolefin, both are stated to 36 kV, and both sell a heavy wall. Indoors in a dry enclosure the non-tracking compound buys nothing, and a standard tube at the right recovered wall is the correct part.
| GHW heavy wall | GAT anti-tracking | |
|---|---|---|
| Stated duty | Mechanical protection and outer sealing of underground straight-through joints | Insulation of MV cable joints and terminations |
| Voltage stated | Up to 36 kV | Up to 36 kV |
| Recovered wall published | 2.4 to 4.5 mm | 2.5 to 3.0 mm; 5 mm heavy wall |
| Track and erosion row | Absent from the sheet | 3.25 kV for 20 min, no failure |
| Continuous limit | -40 to +110 °C | -40 to +100 °C |
| Qualification report | QR 1013 | QR 1021 |
Two names, one product — and the dimensions are only in the PDF
The manufacturer keeps anti-tracking tube and non-tracking tube as separate pages: same compound, same 36 kV envelope, same QR 1021. Neither carries a single dimension. Both charts above come off the datasheet, a scan with no text layer, which is why a size that exists can look as though it does not. If a drawing names one of the two, search the other.
Where this layer sits
- Semi-conductive and screening tubeGCT 30/10 to GCT 180/55, GDLT and GVOT — the field-management layers
- Medium and heavy wall tubingGMW to 3.3 kV, GHW to 36 kV, QR 1013
- Why a recovered tube failsThe five faults that are not tracking
- Heat shrink size chartEvery series normalised to supplied ID, recovered ID and wall
Send the site conditions, not only the diameter
Carry the cable size and voltage class, indoors or outdoors, what is in the air at that site, and whether this layer is outermost. Name the chart, GAT or GAT (HW): the wall differs by 2 mm and the supply form by an order of magnitude.