Compressed air hose selection: oil mist, temperature and the 40 bar exception

Air hose is the most common hose on any site and the least specified. Almost all of it is rated 20 bar, and almost all of it looks alike — which is why the differences get missed. The ones that matter are the tube against compressor oil, the temperature of the air where the hose actually starts, and how the hose was built.

/01Oil mist and the tube.

Compressed air carries fine oil from the compressor, and over time that oil attacks tube compounds that are fine with water. Our air and water hoses are built with oil-mist-resistant tubes — NR/SBR or SBR on the 20 bar hoses, EPDM on the anti-static hose — and covers resistant to abrasion, ozone and weather. Where the line carries more oil than mist, or is a lubricator feed, the mineral oil and air hose (A125, 20 bar, NBR tube) is the better choice.

/02Hot air off the compressor.

Air leaves a compressor hot, and the first few metres of hose see temperatures the rest of the system never does. A standard 20 bar air hose rated to +70 or +80 °C will age fast there. Our high-temperature air hose (A116EU100) is built for that position: 40 bar working, 120 bar minimum burst, −30 to +100 °C, with high-tensile steel wire plies and a pin-pricked EPDM cover, from 2" to 4". It is the hose for compressor discharge lines and large-bore site air mains, not for the tool end.

/03Mandrel-built or extruded.

Small air hose is usually extruded: the tube and cover are pushed through a die over the reinforcement, giving a smooth, light hose — our A101HP and A102HP. Larger hose is better built on a mandrel, where the layers are wrapped over a steel core and cured on it, which holds the bore round and true and resists kinking in the bigger sizes — our A190 and A190Y, from 1/2" to 3". The pressure rating is the same 20 bar; the difference is how the hose behaves when it is dragged, coiled and run over.

/04Couplings and restraint.

Site air runs on universal (claw) couplings, which connect any hose to any tool of the same type. That convenience is also the hazard: compressed air is stored energy, and a hose end that lets go is driven by the air behind it. Pin every claw joint with a safety clip, fit a whip check cable across joints and from hose to tool, and turn the air off before disconnecting. Our whip checks run from a 1/8" cable at 12" to a 3/8" cable at 44".