Reading an industrial hose layline: pressure, vacuum, safety factor and standard

The print running along an industrial hose is the only specification that travels with it. It survives the hose being cut, coiled and moved between sites, and it answers the questions a buyer, an inspector or a fitter will ask — what is it, what pressure, can it pull suction. Industrial laylines carry a slightly different vocabulary from hydraulic ones, and a few minutes with real examples is enough to read them.

/01Real laylines from our range.

/02The vocabulary.

S&D — suction and delivery — means the hose has a helix and holds vacuum as well as pressure; a hose printed only for delivery should never be used on a pump inlet. BAR is the maximum working pressure. VAC or a figure in mmHg is the vacuum the hose holds without collapsing: 760 mmHg is a perfect vacuum, so 700 mmHg is close to full suction. SF or S:F is the safety factor — burst pressure divided by working pressure. The part code ties the hose to its datasheet, which is where the temperature range, bend radius and compound live.

/03Standards on the cover.

Where a hose is built to a published standard, the layline says so, and that is a claim you can check against the standard's requirements. In our range, the 20 bar air and water hoses print BS 5118/2 and ISO 2398, the mandrel-built air hose prints EN 2398, the anti-static air hose prints BS 2878, and the vapour recovery composite prints EN 13765:2015 Type 3. A hose with no standard printed is not necessarily a poor hose — many good industrial hoses are built to the maker's own specification — but its rating rests on the maker's datasheet alone.

/04When the print has gone.

Laylines wear off on hoses that are dragged and left in the sun. A hose whose print has gone cannot be identified with confidence, and an assembly that cannot be identified cannot be rated. On a site that works to permits or audits, an unmarked hose should be treated as unrated and replaced. Where the hose is otherwise sound and the record exists, tag the assembly with its part code and test date so the identity survives the print.