Silicone hose specifications reduce to four numbers you must read together: working pressure at +20 °C (which falls as bore size rises), the temperature window (typically −60 °C to +180 °C continuous, specialist grades to about +230 °C), the derating that links the two, and the minimum bend radius. Read any one in isolation, especially the headline pressure, and the hose can fail on commissioning. This deep-dive explains what each datasheet parameter means, how it is tested, and where the traps are.
Quick answer: A silicone hose datasheet is valid only as a set: working pressure is quoted at +20 °C and derates 15–25 % or more above +100 °C; burst pressure runs about 4 × WP for braided constructions (≈5 × for unreinforced tubing); vacuum capability exists only in wire-helix builds and is tested per ISO 7233; minimum bend radius is quoted per bore and grows with wall thickness. Confirm every value for your exact DN, ratings are never family-wide.
This article is the parameter deep-dive of the silicone cluster. If you want the step-by-step buying sequence instead, use the 12-point selection checklist; for compound chemistry and application background, see the complete technical guide.
What Do the Core Specifications Mean?
A silicone hose (VMQ elastomer, usually with polyester or aramid fabric reinforcement) is specified by bore (DN), wall thickness, reinforcement architecture, working pressure, burst pressure, temperature range, minimum bend radius, hardness, and, where relevant, vacuum rating and compliance certificates. The silicon, oxygen polymer backbone is what buys the wide temperature window and ozone/UV stability; the reinforcement is what carries the pressure. Two hoses with identical outside diameters can differ several-fold in rating because of what is laminated between the silicone layers.
How Is Working Pressure Rated, and How Does It Derate?
Working pressure (WP) is the maximum continuous operating pressure at +20 °C. Burst pressure is a destructive test value (hydrostatic method per ISO 1402); the design margin between them is not one universal number, braided hose is built to roughly 4:1 burst-to-working, unreinforced tubing to about 5:1. Assemblies are proof-tested without damage at approximately 1.5 × WP.
Two systematic corrections apply to every catalogue figure:
- WP falls as DN rises. Hoop stress scales with diameter, so a construction rated ≈16 bar at DN13 may carry only a fraction of that at DN76. Never extend one figure across a size range.
- WP falls with temperature. Silicone softens measurably above ~+100 °C; typical derating is 15–25 % by +150 °C and steeper beyond. The rating that matters is WP at your operating temperature, read from the manufacturer's pressure, temperature curve.
| Construction | Indicative WP @ 20 °C (small/mid DN) | Burst margin | Vacuum capable |
|---|---|---|---|
| Unreinforced extruded tubing | ≈0.5–3 bar | ≈5:1 | no |
| 1-ply polyester braid | ≈4–8 bar | ≈4:1 | no |
| 2–4-ply polyester/aramid braid | ≈8–16 bar | ≈4:1 | no |
| Wire helix + fabric braid | ≈6–12 bar | ≈4:1 | yes (confirm rating) |
Values are indicative; treat the datasheet for your exact bore as the only contractual number.
What Temperature Range Can Silicone Actually Sustain?
Standard compounds are rated −60 °C to +180 °C continuous; high-temperature grades extend to about +230 °C, with short manufacturer-approved peaks somewhat higher. Silicone retains flexibility at low temperatures where NBR and EPDM stiffen, which is why it serves cold-climate charge-air and coolant duty.
The exclusions define the envelope as much as the numbers: silicone is not for petroleum oils and fuels, aromatic solvents, or concentrated acids and alkalis, and not for high-pressure steam. Continuous steam duty belongs to a steam hose per EN ISO 6134 (type 1: 6 bar / 164 °C; type 2: 18 bar / 210 °C) with bolted safety clamps to EN 14420-3 / DIN 2817. On saturated steam, pressure and temperature are physically coupled, you cannot specify them independently. Short SIP sanitisation cycles on hygienic platinum-cured silicone are a separate case the hose manufacturer must approve explicitly.
Sustained operation above the rated ceiling drives oxidative cross-linking: the wall hardens (Shore A climbing beyond ~80 is a field indicator), elongation collapses, and the hose crazes and cracks. That is a specification error, not a product defect.
How Do I Read Minimum Bend Radius?
Minimum bend radius (MBR) is the tightest centreline radius the hose sustains without kinking or collapsing the bore; bend behaviour is tested per ISO 1746. MBR is published per bore and increases with wall thickness and ply count, as a rough orientation, fabric-braided silicone runs on the order of 1–3 × bore diameter, but the datasheet value is the only one to design against.
Three practical rules:
- Route so that every installed bend exceeds the MBR at operating temperature, a hot, softened wall kinks earlier than a cold one.
- Keep the first section behind each fitting straight; bending directly at the ferrule or clamp concentrates stress at the weakest interface.
- Where the geometry cannot respect the MBR, specify a moulded elbow (45°/90°/135°), it keeps a constant bore through the bend instead of collapsing at the intrados.
Which Secondary Parameters Matter on the Datasheet?
| Parameter | Typical range | Test method | Why it matters |
|---|---|---|---|
| Shore A hardness | 50–70 | ISO 48-4 / ASTM D2240 | seal behaviour under clamps; pressure capability |
| Tensile strength | ≥8 MPa | ISO 37 / ASTM D412 | low values flag undercure or degradation |
| Elongation at break | ≥200 % | ISO 37 | flexibility reserve at low temperature |
| Compression set (22 h / 175 °C) | ≤25–30 % | ISO 815 / ASTM D395 | the best single predictor of clamp-seal life |
| Vacuum rating | wire-helix builds only | ISO 7233 | fabric braids collapse below atmospheric |
Compression set deserves the highlight: a compound that takes a permanent set under clamp load at temperature will seep at the connection within months, regardless of how good the pressure rating looks. For hot clamp-sealed joints, prefer ≤25 % at 175 °C and plan a re-torque after the first thermal cycles.
Which Standards and Certificates Belong in the File?
- SAE J20, automotive coolant hose requirements (dimensions, pressure/temperature classes, impulse testing). Request the actual impulse test report for cycling duties rather than assuming a figure.
- ISO 1402 / ISO 7233 / ISO 1746, hydrostatic, vacuum, and bend test methods behind the datasheet numbers.
- FDA 21 CFR 177.2600: US food-contact requirement applicable to silicone; in the EU the framework is Regulation (EC) 1935/2004 with GMP (EC) 2023/2006. Regulation 10/2011/EU covers plastics only, it does not apply to silicone; BfR Recommendation XV is the silicone-specific reference.
- USP Class VI, pharmaceutical biocompatibility; combine with a platinum-cured compound, which is the correct cure system for pharma because it leaves no peroxide residues.
Certificates are medium- and version-specific. A hose family "compliant with FDA" means nothing until the declaration names your compound, your hose version, and a batch.
Where Do Specification Mismatches Show Up in Service?
Failure signatures map back to single datasheet lines. Hardening and surface crazing → temperature ceiling exceeded (line: continuous rating). Blistering or delamination of the cover → medium incompatibility or overpressure at temperature (lines: media table, P, T curve). Bore collapse on suction → vacuum duty on a non-helix build (line: vacuum rating). Leakage at fittings under thermal cycling → compression set too high or wrong crimp/clamp specification (lines: compression set, assembly spec). A pinhole leak at the fitting rather than mid-hose rupture almost always indicts the crimp specification, not the compound.
For inspection planning: hot or cycling duties justify a 12-month walk-down; ambient low-duty circuits can extend to 24–36 months. Any bore discolouration in food or pharma service is an immediate removal trigger.
Cost: Read the Premium Against the Duty
Silicone typically costs two to four times an equivalent EPDM hose. The premium pays back wherever the duty is above ~120 °C, hygienically audited, or hard to access, one avoided unplanned change-out on a production line usually covers the difference across the installation. Custom moulded parts add tooling cost and multi-week lead times, so hold strategic spares for moulded geometries on continuous processes.
Validate the Numbers Before You Order
Compare constructions and sizes in industrial hoses, search the stock directly for silicone hose, or pull manufacturer datasheets from the catalogue library. If the pressure, temperature curve, vacuum rating, or compliance package for your duty is unclear, ask our engineering team, we select hose and fittings, assemble, and pressure-test the complete assembly with the certificates your file requires.