Geometry test
Tube or moulded shape: where an extruded tube stops working
A tube recovers about one axis, at 2:1 to 5:1. Count the ends before you count millimetres — three ends meeting at one point is a shape, not a tube.
The test, in ten seconds
Lay the assembly flat and count the ends. One entry, one exit, one straight axis, and a diameter change the ratio can bridge: that is tube work. Anything else is a moulded shape.
Three things break the one-axis rule. A branch — a Y, or one sheath opening into two to seven cores at a point. A bend past gentle, where the outer radius stretches while the inner radius sheds circumference. And a step past the ratio: a 3:1 tube recovers to a third of its supplied diameter, so the size that clears 30 mm closes no further than 10 mm. Ratio is a ceiling, not a target.
The reason sits in the material data. Longitudinal change is capped at −10% max to ASTM D2671 on the GMW and GHW sheet, and again on GMW 5x, so the tube barely shortens as it closes. Recovery is circumferential, about one line. A crutch asks for it about every leg at once.
That geometry is moulded, not extruded. Gala's published capacity splits 30 million moulded parts a year against 9 million metres of tubing, with moulded shapes made there since 2001. American catalogues spell the family molded shapes; same part.
The manufacturer draws the line from its own side, and not where you would expect: the GDW dual wall sheet lists “alternative to moulded parts and cable breakouts” among its applications. Read that as scope. GDW seals a step in one axis with hot-melt under the wall — it does not add an outlet.
What is in front of you
Left column is what you have. The middle column is what the tube charts settle. The right column is a routing call, not a specification.
| Geometry | Extruded tube | Moulded shape |
|---|---|---|
| One axis, one diameter. | Yes. Size on recovered ID and recovered wall. | No reason to leave the tube chart. |
| One axis, a step in diameter. | Yes, out to 5:1. GMW 5x 160/32 passes a 160 mm obstruction and closes to 32 mm. | The breakout chart is indexed by core count; a plain step has one. |
| A branch: 2 to 7 cores leaving one sheath. | No. One axis against two to seven legs. | LV2GBB to LV7GBB, hot-melt coated internally, IP 68 installed, to 3.3 kV. |
| A right-angle entry at a gland or lug. | GLC-SV takes a bend without wrinkling, but its published applications are bolts, not cable. | Right-angle and straight boots, indexed at cablebreakoutboots.com. |
| One closed end. | No. A tube is open at both ends. | That part is an end cap, indexed at anodecap.com. |
| Two cable constructions spliced together. | No. Insulation, screen and oil barrier are separate layers. | Neither: a kit. GTJ-11 to GTJ-17, PILC to XLPE, to 12 kV. |
Four times you do not need a moulded shape
Three have one axis hiding under an awkward outline. The fourth branches, and still is not a heat-shrink shape.
GMW 5x
Eleven sizes at 5:1, GMW 5x 30/6 to 160/32, wall 4.3 to 5.0 mm ±10%. One piece spans a connector, its back shell and the cable behind it. Hot-melt lining is optional on this series and takes it to IP 68.
GDWH
GDWH-1 to GDWH-5 at 4:1, adhesive-lined, −55 °C to +125 °C to IEC 216. Two diameters per size: the wire it closes onto, d (AL) 1.25 to 4.35 mm, and the joint it passes over, d (J) up to 7.40 mm. A crimp mid-run is a bulge on one axis.
GCEB
Cold-shrink crutch sleeves GCEB2-1 to GCEB4-2, EPDM expanded on a removable core. Body bands Ø17–Ø30 up to Ø32–Ø50, finger bands Ø10–Ø14 or Ø12–Ø17, dielectric strength 14.3 kV/mm to ASTM D149. It branches, but it arrives shaped and nothing is heated on site.
GLC-SV
Vented thin wall at 2:1, GLC-SV 20/10 to 70/35, recovered wall 0.78 to 1.10 mm, −40 to +125 °C to IEC 216. An internal air-vent groove lets it shrink wrinkle-free over a bend, without grease or lubricant. Its published applications are wind-power anchor bolts, automotive parts and U-bolts; no cable geometry appears on that sheet.
The wrong choice, worked through
Four cores leaving one sheath at 3.3 kV, and heavy wall at 3:1 is what is in the van. It recovers onto the sheath, then reaches the point where the cores separate. Two published figures bound what follows. Longitudinal change is capped at −10% max to ASTM D2671, so the tube cannot shorten to absorb a circumference that keeps changing along the branch. Hot-melt lining is optional on that series, so surplus material folding on itself seals to itself, not to the sheath. That second step is this reference's reading of the first; no failure analysis is published for it. What is published is a different part for this geometry — LV2GBB to LV7GBB, 2 to 7 core, internally hot-melt coated, IP 68 installed, on PVC, XLPE, rubber and PILC cable to 3.3 kV.
The part by name, and where its numbers are published
By part, not by preference. One is the manufacturer's own chart; the other five are sister references from the same publisher.
- Moulded breakout, 2 to 7 coresDs, Df, ds, df and both leg lengths, LV2GBB-0308 to LV7GBB-1845. Issue 2, Dec 2024.
- Boots and breakouts as a subjectIndexed by outlet count first, then by what each outlet takes down to.
- Shrouds and busbar coversBUSBOOT, PVC or cross-linked polyolefin, where a bolted bar joint needs covering rather than sleeving.
- PILC-to-XLPE transition jointGTJ-11 to GTJ-17, 3×16–35 up to 3×630 sq mm, with the barrier connector and oil-barrier sleeve.
- Cable terminationsGXO/E, GPO/E and GLT-1100 by voltage class. At a screen cutback the sleeve stack decides the part, not the outline.
- Cable end capsFour cap size charts, and how to read a code before you quote it.
Send the geometry, not the part number
How many ends, the diameter at each, the angle if there is one, and the voltage class. Four lines settle tube or shape.