The vulcanized fiber and fiberglass composite tube, called tubo portafusible or tubo combinado en fibra vulcanizada in Spanish and tubo porta-fusível in Portuguese, is the arc-quenching liner used in expulsion fuse tubes that interrupt high-voltage AC circuits during faults. Buyers across Latin America and Brazil search for it under these names, so this article explains what the composite actually is, how it is built, and how to specify it when your drawing uses Spanish or Portuguese terminology.
Names for the Same Part
The terminology varies by market even though the construction does not. A quick reference, because mismatched names are the single most common reason a first inquiry goes nowhere.
| Language | Term | English equivalent |
|---|---|---|
| Spanish | tubo portafusible | fuse holder tube |
| Spanish | tubo combinado en fibra vulcanizada | vulcanized fiber composite tube |
| Spanish | tubos fusibles | fuse tubes |
| Spanish | fibra vulcanizada | vulcanized fiber, also called bone fiber |
| Portuguese | tubo porta-fusível | fuse holder tube |
| Portuguese | tubo de fibra vulcanizada | vulcanized fiber tube |
| English | expulsion fuse tube | cutout fuse tube |
Why Combine Vulcanized Fiber With Fiberglass
Compared with a synthetic polymer combination tube, a fiberglass and vulcanized fiber composite offers three advantages:
- No spark generation at the liner wall under arc.
- A controlled carbon layer that prevents excessive ablation of the liner.
- Optimal arc-quenching gas generation so the arc clears quickly.
The second point is the one buyers underestimate. A liner that ablates too aggressively enlarges its own bore on every operation, which shortens service life and eventually prevents the tube from clearing a fault at all.
How the Tube Is Made
An epoxy fiberglass composite tube is produced by wrapping a vulcanized fiber core with glass filaments saturated in epoxy resin. The winding angle is typically set at 55 degrees. The vulcanized fiber becomes an integral liner that provides the gas-generating, arc-quenching behavior, while the epoxy-saturated fiberglass delivers strength and water resistance. The finished tube is usually coated with a UV-resistant gray paint for outdoor service.
What Each Layer Does
| Layer | Material | Function |
|---|---|---|
| Inner liner | Vulcanized fiber | Generates deionizing gas, controls the arc, forms a stable carbon layer |
| Structural wrap | Glass filament in epoxy resin | Carries internal pressure and mechanical load, provides dielectric strength |
| Outer coating | UV-resistant gray polyurethane paint | Protects against sunlight, rain, and atmospheric contamination |
| Ferrules | Metal end fittings | Locate the tube in the holder and carry contact pressure |
Where It Is Used
The main application is the expulsion fuse tube of cutouts, where it interrupts high-voltage AC during a fault. Engineers also specify it in high-voltage current limiters and drop-out fuses. In Latin American distribution networks you will find these tubes in the same three places: the cutout on a branch line, the cutout ahead of a distribution transformer, and the limiter that protects downstream switchgear.
Specification Checklist
- System voltage: 10 kV, 15 kV, 24 kV, 27 kV, and 38 kV classes cover most distribution work
- Continuous and interrupting current: for example 100 A and 200 A tubes, which carry different bore limits at end of life
- Outside diameter and length with tolerances: the two dimensions that determine whether the tube seats in the holder
- Bore and wall thickness: controls both dielectric margin and pressure containment
- Liner material and density: vulcanized fiber or, for wet environments, a synthetic arc-quenching liner
- Finish: UV-resistant outdoor paint, or a moisture-proof grade for coastal and humid sites
- Reference drawing and annual volume: both help a manufacturer quote a stable price instead of a one-off number
Outdoor, Indoor, and Wet Locations
The standard composite tube with gray UV-resistant coating suits outdoor cutout service on inland networks. Two conditions argue for a different choice. In very damp or coastal locations, a moisture-proof synthetic liner performs better than vulcanized fiber, which can absorb moisture through exposed ends. And where the tube will be handled frequently and reused after many operations, confirm the expected number of interruptions with the manufacturer, because reuse life depends on how fast the liner ablates, not on the outer coating.
Common Problems in Latin American Procurement
- Quoting from an old sample with no drawing. Send measured dimensions with tolerances. A worn sample gives outside diameter and length but hides the original bore.
- Mixing terminology across documents. Use the term table above so the technical requirement and the purchase order describe the same part.
- Assuming all 15 kV tubes are interchangeable. Current rating, bore limit, and ferrule dimensions differ between holders, so confirm the cutout model.
- Overlooking end-of-life criteria in the tender. Ask for the maximum liner bore at replacement. It is the criterion your crews will apply in the field for the next ten years.
Why Source From a Direct Manufacturer
Tianze Electrical manufactures vulcanized fiber composite tubes and epoxy filament-wound housings for switchgear brands worldwide, rather than reselling them. Production is ISO 9001 certified, SGS material testing is available, and we build to a drawing so the liner density and bore tolerance stay consistent from lot to lot. More detail on the construction side is on our vulcanized fiber combination tube page, and the full range is listed under fuse tubes and fuse links.
Frequently Asked Questions
Q: What winding angle is used?
A: Around 55 degrees is standard; it can be adjusted to tune strength and insulation for your design.
Q: Is it suitable for outdoor use?
A: Yes, with the UV-resistant coating. For very damp conditions, a moisture-proof synthetic liner is the better option.
Q: What is the Spanish name I should put on a purchase order?
A: Either tubo portafusible or tubo combinado en fibra vulcanizada is understood in the trade. Add the drawing number so the description cannot be misread.
Q: Do you provide the end-of-life bore limit with the tubes?
A: Yes. Tell us the current rating and application, and we will state the maximum liner bore at which the tube should be replaced.
Contact sale@fusestube.com for a quotation, including tubo portafusible and tubo combinado en fibra vulcanizada enquiries, or browse the fuse tube range.
