A steam hose is a rubber hose built to EN ISO 6134 for saturated steam service: type 1 is rated 6 bar / 164 °C, type 2 is rated 18 bar / 210 °C, and both must be assembled with bolted safety clamps (EN 14420-3 / DIN 2817), never crimped ferrules and never Camlock couplings. Because pressure and temperature are physically coupled in saturated steam, a steam hose is always specified by both values together, and a failure is a burn hazard, not just a leak.
This guide covers construction, the EN ISO 6134 rating system, fitting rules, installation, inspection, and lifetime cost, the reference knowledge behind a safe steam hose purchase. For the condensed parameter tables, see the sibling article Steam Hose: Specifications, Standards and Safe Selection.
What Is a Steam Hose and How Does It Work?
A steam hose conveys saturated steam, and the condensate formed on cooling, between fixed or mobile points: boiler headers, cleaning lances, autoclaves, tank heating coils. Unlike hydraulic hose, which manages pressure at moderate temperatures, a steam hose must resist internal pressure, sustained heat, and chemically aggressive condensate (pH typically 5.5–9.5 depending on boiler water treatment) at the same time.
The heat-resistant inner tube confines the steam; textile or steel-wire reinforcement carries the hoop stress; the cover protects against mechanical damage, ozone and heat radiated from adjacent plant. Thermal cycling is the defining design load: a hose used for purging or hose-down duty may see many heat-up/cool-down cycles per day, and every cycle works the rubber and the coupling interface.
Why are pressure and temperature coupled in steam service?
In saturated steam the two values are locked together by physics: at 6 bar gauge the steam is at roughly 165 °C, at 10 bar roughly 184 °C, at 18 bar roughly 210 °C. A hose rated "10 bar" for water at 20 °C tells you nothing about its suitability for 10 bar steam. This is why EN ISO 6134 rates steam hose as a pressure, temperature pair, and why superheated steam (temperature above saturation for the given pressure) must be declared to the manufacturer separately.
Construction and Materials
Inner Tube
- EPDM is the industry-standard steam tube compound. Correctly compounded EPDM covers both EN ISO 6134 types, up to 164 °C (type 1) and up to 210 °C (type 2). EPDM is never suitable for mineral oils or fuels.
- Butyl rubber (IIR) offers low permeability and is used where condensate purity matters; temperature capability is lower than steam-grade EPDM, check the datasheet.
- For food-plant steam used in direct product contact, the tube compound must additionally satisfy food-contact requirements (see Standards below).
Reinforcement
Steam hose reinforcement is high-tensile textile plies or steel-wire braid. Type 1 (6 bar) hoses are typically textile-reinforced; type 2 (18 bar) hoses use steel wire braid, which also gives the assembly the stiffness needed for safe clamp retention. A steel helix may be added for heavy wall crush resistance.
Cover
The cover is EPDM or CR (chloroprene), usually with a wrapped (cloth-impressed) finish that shows abrasion wear clearly before the reinforcement is exposed. Pin-pricked covers are standard on steam hose: steam permeating through the tube must vent through the cover instead of accumulating and blistering it.
EN ISO 6134 Types and Ratings
EN ISO 6134 is the international standard for rubber steam hoses and hose assemblies. It defines two types by pressure, temperature rating, each in class A (oil-resistant cover) or B (non-oil-resistant cover):
| EN ISO 6134 rating | Max working pressure | Max steam temperature | Typical construction |
|---|---|---|---|
| Type 1 (low pressure) | 6 bar | 164 °C | EPDM tube, textile plies |
| Type 2 (high pressure) | 18 bar | 210 °C | EPDM tube, steel wire braid |
Key takeaway: there is no "class 3 / 17 bar / 185 °C" steam hose in EN ISO 6134, specifications quoting such a class are fabricated. If your process sits between the types, specify type 2.
Steam hose carries a far higher design margin than general industrial hose: EN ISO 6134 requires burst testing at 10× the maximum working pressure (e.g. a 6 bar type 1 hose must withstand 60 bar). This reflects the consequence severity of steam release and progressive heat ageing of the rubber. Working pressure is quoted at the rated steam temperature, no additional temperature derating tables are needed within the type rating, but any superheat beyond it requires manufacturer confirmation.
Fittings: Bolted Safety Clamps Only
This is the single most safety-critical rule in steam hose specification:
- Steam hose assemblies must use bolted safety clamps to EN 14420-3 (DIN 2817) on serrated hose tails (EN 14420-5). The two-bolt clamp halves compress the hose wall onto the tail and can be re-torqued after the first heat cycles, when the rubber has taken its compression set.
- Crimped or swaged ferrules are prohibited on rubber steam hose. Thermal cycling relaxes the rubber under a fixed crimp; the joint loosens invisibly until the hose blows off under pressure.
- Camlock (cam-and-groove) couplings must never be used for steam. Camlock is a liquids-only coupling (EN 14420-7 / MIL-C-27487); its elastomer gasket and lever-arm retention are not designed for pressurised steam, and a cam arm knocked open on a live steam line is a potentially fatal release. The same applies to any push-on or claw-type air coupling.
- Fitting materials: carbon steel is standard; stainless steel 316 for food-grade, coastal or corrosive environments. Threaded ends are typically BSP; note that G/BSPP (ISO 228) parallel threads seal on a washer, while R/BSPT (ISO 7) and NPT tapered threads seal on the thread, and NPT and BSPT are not interchangeable.
Re-torque the clamp bolts to the coupling manufacturer's specification after the first day of steam service and check them at every inspection. Browse compatible tails and clamps in industrial fittings.
Applications in Industry
Process and manufacturing: cleaning, sterilisation, heating and purging duties across chemical, rubber and plastics plants. Autoclave and vulcanisation service is continuous high-temperature duty, specify type 2 and shorten inspection intervals.
Oil, gas and petrochemical: winterisation, heating and decoking support. In ATEX-classified zones, specify electrically bonded assemblies; electrical resistance of hose assemblies is measured per ISO 8031, and documentation per ATEX 2014/34/EU must accompany the product.
Marine: boiler blowdown and heating-coil connections; classification societies (Lloyd's Register, DNV, Bureau Veritas) mandate periodic proof testing of assemblies.
Food and beverage: steam used for direct-contact culinary duty or equipment sterilisation requires a tube compound compliant with FDA 21 CFR 177.2600 (rubber) and the EC 1935/2004 framework with GMP 2023/2006. Note that Regulation 10/2011/EU applies to plastics only, it does not certify a rubber steam hose. The certificate is always issued for a specific medium and hose version; ask for it explicitly.
Selection Checklist
- Pressure and temperature together: establish the relief-valve setting and the corresponding saturation temperature; select type 1 (≤6 bar / 164 °C) or type 2 (≤18 bar / 210 °C). Declare any superheat.
- Condensate chemistry: confirm tube resistance to boiler additives and descaling agents.
- Bore and velocity: size the bore to keep steam velocity below roughly 25–30 m/s to limit erosive condensate impingement and pressure drop.
- Cover class: class A (oil-resistant) where the hose lies in oily environments.
- Fittings: EN 14420-5 tails with EN 14420-3 / DIN 2817 bolted safety clamps, no exceptions.
- Length and thermal growth: a 3 m steam hose elongates measurably on heat-up; never install taut.
- Compliance: EN ISO 6134 marking with embossed manufacture date; PED 2014/68/EU for assemblies above 0.5 bar (steam is a Group 2 fluid but the P×DN thresholds are low, most industrial steam assemblies fall under sound engineering practice or category I); ATEX where zoned; food-contact certificates where relevant. UK operators additionally maintain a Written Scheme of Examination under PSSR 2000.
Find suitable products under industrial hoses or search directly for steam hose.
Installation and Operation
Warm-up discipline prevents most steam hose incidents. Open steam valves slowly; drain condensate through a properly sized trap before admitting full pressure. Rapid admission into a cold, condensate-filled hose produces condensate hammer, momentary impact pressures many times the working pressure.
Routing: minimum of bends, never below the minimum bend radius, no low points that trap condensate. Support long runs so sagging pockets cannot form. Drain and hang the hose after use, standing condensate is the main tube-ageing accelerator.
Never leave a steam hose pressurised and unattended if the site procedure does not require it; isolate and drain.
Inspection, Failure Modes and Service Life
Inspect visually before each use; formally document an inspection at least every six months (more often for continuous or autoclave duty):
- Hardened, cracked or swollen tube, thermal ageing or over-temperature; withdraw the hose.
- Cover blistering, steam permeation through a damaged tube (or blocked pin-pricks); withdraw.
- Loose or corroded clamp bolts, re-torque or replace; rust tracks from under the clamp indicate leakage.
- Kinks or crush marks, the reinforcement is compromised at that point regardless of external appearance.
- Any hose that has experienced water hammer or been run over must be tested or replaced before re-use.
Elastomer steam hose has a finite life irrespective of appearance. Follow the manufacturer's replacement guidance, commonly a maximum of five years from the embossed manufacture date for standard duty, and two to three years for high-cycle or continuous service near the temperature rating.
Cost and Total Cost of Ownership
The purchase price of a steam hose assembly is minor against the cost of a failure: emergency downtime in process industries routinely costs thousands of euros per hour, before any injury investigation. The economic levers are simple, specify the correct type with margin, use only bolted-clamp assemblies from one supplier so the tail, clamp and hose are validated together, and budget replacement on a fixed interval instead of running to failure. Standardising bore sizes and fitting ends across the plant cuts stock and eliminates improvised (and dangerous) adapter chains.
Get the Right Steam Hose Assembly
Tubes International supplies EN ISO 6134 type 1 and type 2 steam hoses with EN 14420-3 safety-clamp assemblies, pressure-tested and documented. Browse industrial hoses and the PDF catalogues, or send an enquiry, our engineering team selects the hose and fittings for your pressure, temperature duty and pressure-tests the complete assembly before dispatch.