Rubber hose specifications are a small set of numbers that must be read together: working pressure (quoted at +20 °C and falling as bore rises), burst pressure (a construction-specific multiple, not one universal factor), the temperature window of the tube elastomer, and the minimum bend radius of the reinforcement. Confusing any two of them — working with burst pressure, ambient with derated ratings — is the root cause of most premature failures. This deep-dive explains each parameter, the test standard behind it, and the derating rules that catalogues rarely print on page one.
Quick answer: Working pressure is the continuous limit at +20 °C and decreases with DN — EN 853 1SN runs 250 bar at small bores down to 40 bar at DN51, 2SN from 415 to 80 bar; only the spiral families SAE R12/R13/R15 hold constant 280/345/420 bar. Burst margins are construction-specific: ~4:1 for braided hose, ~5:1 unreinforced, 3:1 PTFE, ~2.5:1 UHP water-jetting (EN 1829-2). Temperature limits follow the tube elastomer (NBR ≈ +100 °C, EPDM higher in water duty, FKM ≈ +200 °C), and ratings derate as temperature rises. MBR is measured to the hose centreline and grows with reinforcement stiffness.
This is the parameter deep-dive of the rubber cluster. For the step-by-step buying sequence, use the 12-point selection checklist; for specification pitfalls before ordering, see what every buyer needs to know.
What Exactly Does a Rubber Hose Specification Define?
A complete specification fixes: internal diameter (ID/DN, dimensions per ISO 4671), outside diameter and its tolerance (which governs ferrule selection), working pressure, burst pressure, proof pressure, temperature range, minimum bend radius, tube and cover compounds, and the governing standard. The parameters map to layers: the tube elastomer sets chemistry and temperature, the reinforcement sets pressure and bend behaviour, the cover sets environmental resistance. Two hoses of identical OD can differ several-fold in rating because of what lies between tube and cover.
How Do Working, Proof, and Burst Pressure Relate?
Working pressure (WP) is the continuous operating limit at +20 °C. Proof pressure is a non-destructive assembly test — 1.5–2 × WP depending on the standard (hydraulic EN/SAE families test at 2 ×). Burst pressure is the destructive type-test value, and the margin between burst and WP is construction-specific:
| Construction | Design burst margin |
|---|---|
| Braided (textile or wire) | ≈4:1 |
| Unreinforced rubber | ≈5:1 |
| PTFE-lined | 3:1 |
| UHP water-jetting | ≥2.5:1 (EN 1829-2) |
Two corrections keep catalogue figures honest. First, WP falls as DN rises within a construction: EN 853 1SN spans 250 bar at small bores to 40 bar at DN51; 2SN spans 415 to 80 bar. The engineered exceptions are the spiral families SAE R12 (280 bar), R13 (345 bar), and R15 (420 bar), designed for constant pressure across sizes. Second, surges count against WP: hydraulic circuits spike well above nominal pressure at valve closure, and the spike — not the average — is the selection value. Also remember that a fitting's PN class is a designation, not a working-pressure guarantee for the assembly.
| Type (EN ≈ SAE) | Reinforcement | WP across DN range |
|---|---|---|
| EN 854 (≈ 100R3/R6) | textile braid | low pressure, falls quickly with DN |
| EN 853 1SN (≈ 100R1AT) | 1 × wire braid | 250 → 40 bar |
| EN 853 2SN (≈ 100R2AT) | 2 × wire braid | 415 → 80 bar |
| EN 857 1SC/2SC | compact wire braid | as 1SN/2SN class, smaller OD/MBR |
| EN 856 4SP/4SH | 4 × spiral wire | high pressure; 4SH up to 420 bar at small DN |
| SAE 100R12/R13/R15 | 4–6 × spiral wire | constant 280 / 345 / 420 bar |
EN and SAE types are close counterparts, not 1:1 equivalents — dimensions, impulse counts, and fitting validations differ. ISO 18752 takes a third route: performance-based grades defined by impulse capability rather than construction, useful when procuring globally across manufacturers.
Which Temperature Limits Apply — and How Do Ratings Derate?
The tube elastomer sets the window: NBR roughly −40 °C to +100 °C (fuels and mineral oils; not hot aromatics); EPDM for water and many chemicals with higher wet-duty ceilings — but never oils or fuels; FKM to about +200 °C for aggressive chemistry and aromatics (not ketones); PTFE-lined hoses −70 °C to +260 °C with near-universal chemistry. Pressure ratings are quoted at +20 °C; elastomer and plastic hoses derate as temperature rises — typically by tens of percent toward the ceiling — so the contractual value is WP at operating temperature from the manufacturer's curve.
Steam is a separate product class, not a temperature footnote. Steam duty requires a hose per EN ISO 6134 — type 1: 6 bar / 164 °C; type 2: 18 bar / 210 °C — always assembled with bolted safety clamps to EN 14420-3 / DIN 2817, never crimped ferrules and never Camlock. On saturated steam, pressure and temperature are physically coupled; you cannot trade one against the other.
How Is Minimum Bend Radius Measured and Applied?
MBR is quoted to the hose centreline (bend behaviour tested per ISO 1746) and grows with reinforcement stiffness: spiral-wound hose bends less willingly than wire braid, which bends less than textile. Compact EN 857 constructions exist precisely to cut OD and MBR for tight routing.
Violating MBR stretches the outer-radius reinforcement past its elastic limit and buckles the inner radius: the bore necks down, and the kink becomes a stress concentrator that fails in a few hundred impulse cycles instead of hundreds of thousands. The highest-risk zone is directly behind the ferrule — keep the first section straight, and never clamp a hose at the apex of a bend. Where routing cannot respect the MBR, change geometry (elbow fittings, swivels) rather than forcing the hose.
Two related datasheet lines deserve attention: length change under pressure (rubber hose shortens or elongates ±2–4 %; route with slack, not taut) and vacuum rating (tested per ISO 7233; suction lines need a stated collapse resistance — braided pressure hose without a helix will flatten below atmospheric).
Which Test Standards Sit Behind the Numbers?
- ISO 1402 — hydrostatic proof and burst testing; ISO 1746 — bending; ISO 7233 — vacuum; ISO 4671 — dimensions and tolerances; ISO 6945 — cover abrasion resistance (note: abrasion, not electrical properties — electrical resistance of hoses is measured per ISO 8031).
- EN 853 / 854 / 856 / 857 — construction-prescriptive hydraulic and industrial types described above; SAE J517 — the SAE counterpart system; impulse testing per the type's own clauses and SAE J343 methods — request the actual cycle data for dynamic duty rather than assuming a figure.
- ISO 18752 — performance-graded hydraulic hose by impulse class.
- FDA 21 CFR 177.2600 + Regulation (EC) 1935/2004 / GMP (EC) 2023/2006 — food contact for rubber compounds (Regulation 10/2011/EU covers plastics only); potable water adds national schemes (WRAS, KTW); pharma adds USP Class VI.
When a datasheet lists several standards, confirm your specific bore and wall actually certify to each — mixed-compliance families are common.
What Do Failure Signatures Tell You About the Spec Sheet?
Each failure mode indicts a specific line of the specification. Tube blistering/softening → medium incompatibility (elastomer table). Hardening and cover cracking → temperature ceiling or ozone/UV exposure (temperature line, cover compound). Wire rust bleeding at the ferrule → moisture ingress at a poor crimp (crimp specification). Fitting pull-off — the most dangerous — → non-validated ferrule/crimp diameter or insufficient insertion (assembly validation). Kink or flattened bore → MBR violation (routing). Bore collapse on suction → missing vacuum rating (ISO 7233 line).
Inspection policy follows from ageing physics: guidance such as ISO 17165-2 and DIN 20066 recommends documented intervals and commonly cites a ~six-year service-life ceiling for hydraulic assemblies including storage. Exposed reinforcement, blistering, ferrule movement, or crimp seepage force immediate replacement regardless of age.
Cost: Specify to the Duty, Not the Maximum
Purchase price is typically 15–25 % of total cost of ownership in production service; downtime and labour dominate the rest. Upgrading a high-impulse circuit from 2SN to a spiral or higher ISO 18752 grade adds tens of percent to unit cost and typically multiplies the service interval — payback within the first avoided stop on any line where downtime costs hundreds of EUR per hour. The inverse discipline also applies: textile braid on a return line beats a spiral hose on price with zero duty penalty. Batch traceability from a qualified supplier is what makes the certificates audit-proof in food, pharma, and offshore service.
Read the Datasheet, Then Test the Assembly
Compare constructions in power hydraulics and industrial hoses, search stock for rubber hose, or pull manufacturer datasheets from the catalogue library. If a pressure–temperature curve, impulse rating, or compliance package needs validating against your duty, contact our engineering team — we select hose and fittings, crimp to the validated specification, and pressure-test every assembly before it ships.