Silicone line covers: self-locking GSOC and interlocking GSIOC
A bare conductor of up to 400 sq.mm measures up to 32 mm across the strands, and GSOC-M 32 is the 2.0 mm silicone wall published for it, in a 15 m roll.
GSOC self-locking silicone overhead line cover
A non-tracking silicone cover that field-installs over an existing bare conductor with no special tool, published in four voltage classes that differ only in wall thickness. Manufactured by Gala Thermo Shrink Pvt. Ltd., Mumbai.
- No special installation tool required
- UV and ozone resistance
- Tracking resistance
- Flame retardant
- Highly flexible silicone tubing for easy field application
- Does not require further derating of conductors — a GSOC statement, see below
- Optional self-fusing silicone tape, 63.5 mm × 0.76 mm, over the cover for added insulation
| Goes over | A bare overhead conductor already in service, up to 800 sq.mm and up to 38 mm across the strands |
|---|---|
| Series | GSOC-M, GSOC-H, GSOC-H3, GSOC-EH |
| Voltage classes | 12 kV (M), 36 kV (H and H3), 765 kV (EH) |
| Wall thickness | 2.0 mm (M), 2.7 mm (H), 3.0 mm (H3), 5.0 mm (EH) |
| Packaging | 15 m per roll, every size in every class |
| Installation | No special installation tool required; installable without difficulty at 0 °C |
| Dielectric strength | >210 kV/cm (ASTM D149) |
| Tracking and erosion | No tracking, erosion or flame failure at 3.25 kV for 20 min (ASTM D2303) |
| Comes off again | Not published. No removal, re-entry or re-use procedure appears on the GSOC sheet — unlike the GPFIC connection covers, which the manufacturer does describe as field-trimmed and reusable |
GSOC and GSIOC are two constructions, not two names for one
GSOC is the self-locking series; GSIOC is the interlocking series. They share a material family and very little else on paper. GSOC runs in four voltage classes and is published at 7 N/mm² minimum tensile strength with 300% minimum elongation (ASTM D638). GSIOC is published as a single class to 33 kV, at 4 N/mm² and 200% (ASTM D638), with a hardness of 65 ±5 Shore A (ASTM D2240) and a density of 1.10–1.45 g/cm³ (ASTM D792) that the GSOC sheet does not state at all. A part number from one series does not cross to the other, and the two sheets do not share a selection chart — only GSOC has one.
Two lines on the GSOC sheet decide it for a line crew, and neither is a laboratory figure. The first is no special installation tool required: the cover goes on where it stands. The wrap-around polyolefin Insulcover is installed with the Split Insulation Tube Tool at one stationary location, so the polyolefin route asks a crew to bring a tool up to the conductor and the silicone route does not. The second is installable without difficulty at 0 °C, the only cold-installation statement anywhere on the sheet. A cover that has to be coaxed onto a jumper at a winter outage is a cover that ends up back in the van.
The derating answer, sourced exactly. The GSOC sheet states that it does not require further derating of conductors. That claim belongs to GSOC and is reproduced here as GSOC's, from GSOC's own sheet. It is not published for the polyolefin Insulcover, it is not published for GSIOC, and it is not a property of retrofit covers as a class — anything wrapped over a bare conductor is a thermal blanket until a datasheet says otherwise. If an ampacity calculation rests on it, name the GSOC sheet in the calculation and have the manufacturer confirm it against the exact series and wall you are ordering.
GSOC-M selection chart — conductors to 12 kV
| Gala code | Conductor size (sq.mm) | Conductor diameter (mm) | Wall thickness (mm) | Packaging (m/roll) |
|---|---|---|---|---|
| GSOC-M 15 | up to 185 | up to 15 | 2.0 | 15 |
| GSOC-M 20 | up to 300 | up to 20 | 2.0 | 15 |
| GSOC-M 24 | up to 350 | up to 24 | 2.0 | 15 |
| GSOC-M 32 | up to 400 | up to 32 | 2.0 | 15 |
| GSOC-M 38 | up to 800 | up to 38 | 2.0 | 15 |
Two published sheets disagree here, so both are printed. The GSOC product page gives five sizes and puts GSOC-M 24 at up to 350 sq.mm. The Insulation Enhancement Products sheet gives six — it adds a GSOC-M 28 for up to 300 sq.mm and up to 28 mm — and puts GSOC-M 24 at up to 300 sq.mm. The chart below is the GSOC product page. Order against the diameter column, which the two sheets agree on.
What changes between the four classes: the wall
| Series | Rated to | Wall thickness (mm) | Sizes published | Packaging (m/roll) |
|---|---|---|---|---|
| GSOC-M | 12 kV | 2.0 | 15, 20, 24, 32, 38 | 15 |
| GSOC-H | 36 kV | 2.7 | 15, 20, 24, 32, 38 | 15 |
| GSOC-H3 | 36 kV | 3.0 | 15, 20, 24, 32, 38 | 15 |
| GSOC-EH | 765 kV | 5.0 | 15, 20, 24, 32, 38 | 15 |
The number in the code is the conductor diameter the cover accepts, not the wall. GSOC-H and GSOC-H3 are both published to 36 kV and differ only in wall — 2.7 mm against 3.0 mm — so the H3 is the thicker option at the same class, not a higher class.
GSOC — physical properties
| Property | Test method | Typical value |
|---|---|---|
| Tensile strength | ASTM D638 | 7 N/mm² (min.) |
| Elongation | ASTM D638 | 300% (min.) |
| Water absorption | ASTM D570 | 0.5 (max.) |
| Low-temperature installation at 0 °C | — | Installable without difficulty |
GSOC — what survives air ageing
| Property | Test method | Typical value |
|---|---|---|
| Air ageing | ASTM D2671 | 150 °C for 168 hrs |
| Tensile strength, aged | ASTM D638 | 3.5 N/mm² (min.) |
| Elongation, aged | ASTM D638 | 150% (min.) |
The aged row is the one worth reading. After 168 hours at 150 °C the cover keeps 3.5 N/mm² of its published 7 N/mm², and 150% of its published 300%: the sheet is telling you it halves and stops there.
GSOC — electrical properties
| Property | Test method | Typical value |
|---|---|---|
| Dielectric strength | ASTM D149 | >210 kV/cm |
| Volume resistance | ASTM D257 | 1×10¹³ ohm·cm (min.) |
| Tracking and erosion resistance | ASTM D2303 | No tracking or erosion of the top surface and no flame failure: 1 hr at 2.5 kV, 1 hr at 2.75 kV, 1 hr at 3.0 kV, 20 min at 3.25 kV |
What the silicone cover is published for
Straight from the manufacturer's application list for the range, with the one commercial line the sheet adds:
- Phase-to-phase and phase-to-earth insulation on bare overhead conductors, and on the leads and jumpers where the gap is set by the hardware rather than by the span.
- Bird and animal contact — the failure the whole insulation-enhancement range was published to stop, at substations as well as on the line.
- Retrofit on a conductor already strung: the cover goes over what is there, with no conductor replacement.
- Runs that need more than the moulded wall: an optional self-fusing silicone tape, 63.5 mm × 0.76 mm, applies over the cover, and the quantity depends on conductor size.
- Insulation enhancement on conductors up to 765 kV, using the GSOC-EH class at 5.0 mm wall.
GSOC against GSIOC, sheet to sheet
Every figure below is from the two manufacturer datasheets. Where one sheet is silent, the cell says so rather than borrowing the other's number.
| Published property | GSOC (self-locking) | GSIOC (interlocking) |
|---|---|---|
| Voltage classes | M to 12 kV; H and H3 to 36 kV; EH to 765 kV | One class, to 33 kV |
| Tensile strength (ASTM D638) | 7 N/mm² (min.) | 4 N/mm² (min.) |
| Elongation (ASTM D638) | 300% (min.) | 200% (min.) |
| Hardness (ASTM D2240) | Not stated on the sheet | 65 ±5 Shore A |
| Density (ASTM D792) | Not stated on the sheet | 1.10–1.45 g/cm³ |
| Dielectric strength (ASTM D149) | >210 kV/cm, which is above 21 kV/mm | 10 kV/mm (min.) |
| Volume resistance (ASTM D257) | 1×10¹³ ohm·cm (min.) | 1×10¹⁰ ohm·cm (min.) |
| After 150 °C for 168 hr (ASTM D2671) | 3.5 N/mm² and 150% remaining | 3.0 N/mm² and 100% remaining |
| Cold behaviour | Installable without difficulty at 0 °C | No cracking at −20 °C for 4 hr (ASTM D2671) |
| Water absorption (ASTM D570) | 0.5 (max.), printed with no unit | 0.5% (max.) after 24 hr at 23 °C |
| Tracking and erosion (ASTM D2303) | No tracking, erosion or flame failure to 3.25 kV for 20 min | The same ladder, ending 20 min at 3.25 kV |
| Selection chart | Published, by sq.mm and diameter, in all four classes | None on the sheet — ask for sizing |
What this does not do
GSOC-EH is published to 765 kV and is still not something anyone may touch.
- It does not make an energised line safe to handle. A retrofit cover is insulation enhancement against momentary contact; the 765 kV figure describes what the cover adds to the line, not a rating for a hand on it.
- It is not the hard-wearing choice. GSIOC is published at 65 ±5 Shore A (ASTM D2240) while the wrap-around polyolefin covers are published on the Shore D scale — a harder scale entirely. Silicone is the soft option in this range.
- It carries no abrasion or cut-through figure. Neither silicone sheet publishes one, so do not assume a cover will survive being dragged over a crossarm edge because it survived ASTM D2303.
- GSIOC is not a larger GSOC. It stops at 33 kV, publishes lower tensile, elongation, dielectric and volume-resistance figures, and has no size chart of its own.
- It is not published as removable. Nothing on the GSOC sheet describes taking the cover off and refitting it, so plan a re-entry as a cut-and-replace rather than as a trim-and-clip.
- It is not a bus, bushing or terminal product. The connection covers, shrouds and caps in the indoor range are separate parts with separate datasheets.
Where to go from here
- Wrap-around polyolefin line cover (GOC series)The other material for the same conductor, and the tool it needs.
- Polyolefin or silicone line cover? An honest comparisonIf the two sheets above did not settle it.
- Line cover size chart: conductor size to cover codeEvery published size across both materials, in one place.
- Fitting covers, shrouds and capsThe four fitting procedures, and the one removal.
- Overhead line covers for bare distribution and transmission conductorsPart of: the outdoor half of the index.
Give the diameter across the strands, not the catalogue number
Both silicone series are sized on the conductor, and GSIOC has no published chart at all. The manufacturer's own pages for the two products are GSOC self-locking and GSIOC interlocking.