High-Density Vermiculite Thermal Sleeve (Dennis)
A heavy-build fiberglass braid sleeve under the "Dennis" series designation, finished with a vermiculite-type refractory coating and positioned for hot-zone work: sustained radiant heat, weld spatter and short splash events near hoses, cables and hydraulic lines. Slip-on braid, no heat step. Several strong figures circulate for this sleeve (550 °C continuous, UL94 V0, Φ6–Φ75 mm), and none of them currently has test documentation behind it, so this page holds them for verification rather than repeating them as facts.
Specification — what is confirmed and what is held
| Material | High-density fiberglass braid + vermiculite-type coating |
|---|---|
| Shrink behavior | Non-shrink slip-on braid |
| Color | Brown |
| Operating temperature | 550 °C figure under verification : not published |
| Standards | UL94 V0 scope unverified |
| Size range | ID Φ6–Φ75 mm stated, pending confirmation |
Construction: dense braid, refractory finish
The sleeve starts as a fiberglass braid with a noticeably heavier build than standard braided sleeving, then takes a coating of vermiculite-type refractory material. Each element has a job:
- High-density braid. More yarns per unit length means a thicker barrier, better resistance to cut-through, and more surface for the coating to key onto.
- Vermiculite-type coating. A mineral finish whose purpose in this product class is refractory service: resisting spatter and short splash contact and shielding the glass yarns underneath. The exact composition for this build is on the verification list.
- Inorganic system. Glass plus mineral coating contains no polymer to melt or drip. That is a property of the construction : it is not the same thing as a tested flame rating, which is a separate question.
Four heat modes — one sleeve is not rated for all of them
"High temperature" collapses four different duties, and this sleeve's claimable scope depends on test data that is still pending:
- Continuous ambient/service heat. Hours at temperature. The 550 °C claim sits here and is held until its test basis arrives.
- Radiant heat. A hot source nearby, line of sight. Reflection is not this product's mechanism; mass and refractory surface are. Duty-level suitability is confirmed per application.
- Weld spatter. Brief, repeated spatter contact. This is the classic duty for coated heavy braids; the test documentation for this exact build is pending.
- Molten splash. Droplets of metal at melt temperature. The most severe of the four : without a described splash test we will not claim it for this build.
Tell us which of the four dominates your application and for how long; the answer decides whether this sleeve, a different construction, or a combination is right.
Selection inputs
- Object OD with fittings. The braid slides over hoses and cable runs : the largest fitting, not the hose OD, sets the size. The Φ6–Φ75 mm range is stated but unconfirmed.
- Duty description. Which heat mode dominates, at what temperature, for how long. This is the input that the verification program above will be matched against.
- Fixing. Ties or clamps at both ends; heavy braid holds by fit and mass but still benefits from anchoring on moving equipment.
- Documentation needs. If your bid requires UL94 or splash evidence, say so at RFQ : we will supply what exists or state plainly what does not.
Common failure modes, and prevention
Coating abraded away at clamp lines
Cause: The refractory finish is sacrificial where a clamp edge works on it under vibration.
Prevention: Use lined clamps or broad-bearing ties, and position fixings away from the zones that see splash or direct heat.
Sleeve asked to do a splash job without test data behind it
Cause: The product class is associated with splash duty, so the build was trusted for molten metal by association.
Prevention: Match the four heat modes above against your actual exposure. For splash-dominated duty before this build's tests are confirmed, use a product with documented splash performance.
Cut end unravelled through the heavy braid
Cause: Dense glass braid still has no self-edge; a raw cut works loose under vibration.
Prevention: Bind before cutting or request finished ends; recheck after install. A loose end on a hot sleeve sheds glass fibers: handle with gloves.
Rated figure applied to the wrong duty
Cause: A peak number quoted for a job that is really continuous, or vice versa.
Prevention: Specify hours-at-temperature, not just a number. We will confirm against the documented value once verification closes; until then no figure from this page should enter a drawing.
Frequently asked questions
What does the high-density/vermiculite construction add over plain fiberglass braid?
Two things, one proven by construction and one pending test data. By construction: a dense braid carries far more coating loading than an open braid, so the refractory layer forms a heavier, more continuous barrier and the yarns themselves are better protected against abrasion. The intended function of a vermiculite-type coating is to resist weld spatter and brief molten-splash contact that would burn straight through an uncoated braid. How much of that this specific build achieves is exactly what the pending tests are meant to establish. We are not claiming a splash performance figure before those results exist.
Is 550°C continuous or a short-term exposure value?
We cannot answer that yet, and the difference decides whether the sleeve suits your duty. A continuous rating describes thousands of hours at temperature; a short-term or peak value describes minutes. The 550 °C figure circulated for this sleeve has no test basis attached to it, so it is on hold: we will not publish it as either continuous or peak until the supplier provides the test method and duration behind it. Send your actual duty (hours at what temperature, plus any peaks), and we will get a confirmed answer against this exact build.
What test supports weld-spatter or molten-splash use?
That is the question we are asking the supplier too. Splash resistance is not a standard property on a datasheet: it needs a described test (droplet size, temperature, height, number of drops, substrate behind the sleeve) before any claim is worth anything. Until that test documentation exists for this build, treat splash capability as unverified. If your application is splash-dominated, tell us and we will either supply the test when it is confirmed or propose a product whose splash performance is already documented.
What does the name Dennis refer to?
It is the series designation this sleeve is supplied under; we have not yet confirmed whether it is a brand, a model line or a factory series name, and we will state that plainly once the supplier confirms it. The name carries no technical meaning. The construction, high-density fiberglass braid with a refractory-type coating, is what defines the product.
Is the sleeve a flame barrier and an electrical insulation?
Separate the two. As an inorganic glass-and-mineral construction it is not a fuel source, but "does not burn" is not the same as a tested flame rating: any V-0 or similar classification for this sleeve needs the test report and its scope (which thickness, which colour) before we print it. Electrically, the sleeve is a barrier, not a dielectric: voltage isolation stays with the cable's own insulation. We do not publish a dielectric value for this product.
Request a quote for Dennis High-Density Thermal Insulation Sleeve
Send the object OD with its largest fitting, the duty description (heat mode, temperature, duration), documentation requirements and quantity. We return the sleeve size, the current verification status of the ratings you need, and lead time.