The short verdict: 2SN is the default for pressure lines; 1SN is the economical, more flexible choice for return, drain and low-pressure pilot circuits. Both are EN 853 wire-braided hoses with the same NBR tube and the same 4:1 burst safety factor — the second braid roughly doubles the working pressure at any given bore (DN 12: 160 bar for 1SN vs 275 bar for 2SN) at the cost of weight, stiffness and a larger bend radius. Decide from the worst-case circuit pressure at the actual DN, never from a family headline figure.
Choose 1SN when:
- the circuit's worst-case pressure (including spikes) sits comfortably inside the 1SN rating for that DN — typical for tank return lines, drain and case-drain lines, low-pressure pilot circuits,
- routing is tight: 1SN is lighter and bends tighter, easing installation in crowded frames,
- weight matters on suspended or articulated runs.
Choose 2SN when:
- the line feeds actuators or comes off the pump — pressures of 200–350 bar at small and mid DN,
- impulse duty is significant (frequent cycling, proportional valves),
- you want reserve margin against surge on a circuit near the 1SN limit.
What Are 1SN and 2SN?
Both types are defined by EN 853 (internationally ISO 1436): an oil-resistant NBR inner tube, high-tensile steel wire braid reinforcement — one layer for 1SN, two layers separated by a friction layer for 2SN — and an abrasion- and ozone-resistant synthetic rubber cover. Their SAE counterparts are 100R1AT and 100R2AT under SAE J517; construction is similar but the standards are not 1:1 equivalents, so for contracts citing SAE by name use dual-marked hose (details in the companion article EN 853 vs SAE J517).
Standard temperature envelope for NBR-tube hose is −40 °C to +100 °C continuous with mineral-oil fluids; sustained operation above that degrades the tube regardless of braid count. Fluid compatibility is set by the tube compound, not by 1SN/2SN: check ester-based and fire-resistant fluids against the manufacturer's compatibility data (elastomer-fluid compatibility testing per ISO 6072).
Pressure Table: EN 853 1SN vs 2SN by DN
Working pressure falls steeply as bore rises — the single most important fact in this comparison. Minimum burst is 4 × WP for both types; ratings are quoted at +20 °C.
| DN (dash) | 1SN WP (bar) | 2SN WP (bar) |
|---|---|---|
| DN 6 (-4) | 250 | 415 |
| DN 10 (-6) | 180 | 330 |
| DN 12 (-8) | 160 | 275 |
| DN 16 (-10) | 130 | 250 |
| DN 19 (-12) | 105 | 215 |
| DN 25 (-16) | 88 | 165 |
| DN 31 (-20) | 63 | 125 |
| DN 38 (-24) | 50 | 90 |
| DN 51 (-32) | 40 | 80 |
Two practical consequences. First, "1SN vs 2SN" is really a per-size question: at DN 6 a 1SN already carries 250 bar, while at DN 25 even a 2SN gives only 165 bar. Second, if the duty exceeds the 2SN figure at your bore, the answer is not "more braid" but spiral hose — EN 856 4SP/4SH or the constant-pressure classes R12 (280 bar), R13 (345 bar) and R15 (420 bar) from the high-pressure hydraulics range.
Beyond Pressure: Flexibility, Weight, Impulse
| Feature | 1SN | 2SN |
|---|---|---|
| Reinforcement | 1 × steel wire braid | 2 × steel wire braid |
| Minimum bend radius (DN 12) | ~130 mm | ~180 mm |
| Relative weight (same DN) | Lower | ~30–40 % heavier |
| Flexibility | High | Moderate |
| Impulse endurance (ISO 6803 reference) | 150,000 cycles | 200,000 cycles |
| Typical roles | Return, drain, pilot, low-pressure supply | Pump outlet, actuator feed, press and mobile-plant power circuits |
The impulse figures are type-test minima, not service-life predictions: a 2SN generally outlasts a 1SN in cyclic duty because two braids share the stress, but routing below minimum bend radius or a bad crimp erases that advantage instantly. For circuits with high-frequency proportional-valve cycling, ask the supplier for impulse data beyond the standard minimum or move to compact (EN 857 2SC) or spiral constructions.
Can I Substitute One for the Other?
Upgrading 1SN → 2SN is technically safe (pressure margin only grows) but not free: check that the stiffer hose still routes within its larger bend radius, that clamps accept the bigger OD, and that added weight is acceptable on moving runs. Downgrading 2SN → 1SN to save cost is only legitimate when a worst-case pressure survey — relief setting, surge, water hammer — lands inside the 1SN rating at that DN with margin. Fitting logic follows the hose: thread ends may be identical, but the crimp ferrule and crimp dimensions are specific to each hose type's OD and wall; a 1SN ferrule crimped on 2SN (or vice versa) is an ejection risk. Use only the hose manufacturer's crimp specification for the exact hose-fitting pair, with fittings from the hydraulic fittings range.
What Makes Either Type Fail Early?
The failure statistics are dominated by application and workmanship, not by hose quality:
- Sub-minimum bend radius — kinks the tube, concentrates braid stress at the outside of the bend; visible later as a localised bulge or pinhole leak.
- Wrong or worn crimp tooling — fitting ejection under pressure; the most dangerous mode. Validated dies and documented crimp dimensions are non-negotiable.
- Torsion at installation — a few degrees of twist measurably shortens fatigue life; align by the lay line and tighten swivel nuts, not the hose.
- Over-temperature fluid — hardened, cracked tube; check coolers and reservoir sizing rather than blaming the hose.
- Cover abrasion — braid exposed to moisture corrodes silently; sleeve or re-route contact points. Replace any assembly with exposed or rusty braid immediately.
Inspect assemblies at machine service intervals; ISO 4413-based practice treats hydraulic hose as a component with finite service life, so build planned replacement into maintenance rather than running to failure — a burst pressure line on a press or excavator costs multiples of the assembly price per hour of downtime.
Installation Rules That Preserve the Rating
A correctly chosen hose still fails early if installed carelessly. Five rules protect the rating you paid for:
- Length with slack. Braided hose changes length under pressure (contraction of a few percent is normal); a taut hose loads the crimp axially with every cycle. Add slack and route with gentle curves.
- Zero twist. Use the printed lay line as a reference and hold the hose with a backup spanner while tightening swivel nuts — torsion introduced at installation is invisible afterwards and devastating to braid fatigue life.
- Bend away from the fitting. Keep a straight length behind each ferrule (a common workshop rule is at least 1.5 × the hose OD) before any bend begins; bending at the crimp edge concentrates stress exactly where the braid is already clamped.
- Clamp and protect. Support long runs, separate hoses that rub each other, and sleeve contact points — abrasion accounts for more field failures in mobile plant than any pressure-related cause.
- Respect heat sources. Exhausts, pumps and manifolds radiate; where the cover temperature runs high, re-route or fit thermal sleeving rather than accepting accelerated ageing.
On the workshop side, discipline around crimping is the difference between an assembly and a hazard: validated dies for the exact hose-and-fitting pair, crimp diameter measured and recorded, and a proof test at 1.5 × working pressure with the result on the assembly record. Tag each assembly with type, DN, date and batch — audits and warranty cases live on that tag.
Selection Checklist
- Map worst-case pressure per circuit — relief valve setting plus transients, not nominal system pressure.
- Read the rating at the actual DN from the table above; never assume a family figure.
- Check bend radius against the routing — 2SN needs meaningfully more room.
- Confirm fluid and temperature against the tube compound (NBR standard; special compounds for ester/fire-resistant fluids).
- Match fitting and crimp specification to the exact hose type and brand.
- Consider the next family up (EN 857 compact, EN 856 spiral) if pressure, impulse or space is marginal.
- Document the assembly — type, DN, batch, crimp data, test — for traceability and audits.
For the broader engineering context — construction layers, all EN/SAE families, service-life rules — see the complete hydraulic hose guide.
Browse hydraulic hoses by type and DN or search directly for EN 853 hose assemblies. Send your circuit pressures and routing to our engineering team — we select the hose type and DN, crimp to the validated specification and pressure-test every assembly before it ships.