Why Hydraulic Hoses Fail — Causes and Prevention

A weep is a tube or pinhole leak that releases pressure slowly; a burst is a structural failure of the reinforcement. On this range the body is rated 41.5 MPa (415 bar) with 1,660 bar minimum burst, so a burst at working pressure means the wire was already degraded or the pressure was far above the rating.

No. A pinhole usually starts at the tube, from an incompatible medium or a manufacturing fault, and shows as a fine jet with the cover intact. Fatigue failure starts in the wire, near the ferrule, and ends in a ragged split. The 4.6 to 5.4 mm bore of the 3/16 code makes a pinhole show up as a fast pressure drop.

90 mm at the 3/16 code, 100 mm at 1/4 inch, 115 mm at 5/16 and 130 mm at 3/8. These are minimums for a static route; on a flexing arm the working arc should be larger, because a hose held at exactly its minimum will ovalise on the first pressure cycle.

For the 3/16 code, 1,660 bar (24,076 psi) minimum, against 415 bar working. At 1/4 inch it is 160.0 MPa against 40.0 MPa, and at 3/8 inch 132.0 MPa against 33.0 MPa. Every row keeps a 4:1 ratio, so the burst figure scales with the rating rather than sitting at a fixed value.

Because the crimp is where the reinforcement stops being continuous and where flexing concentrates. The braid measures 10.6 to 17.3 mm on this range, and if the ferrule does not grip the full layer the wire draws back under pressure, so the assembly separates well below the 1,660 bar the body can hold.

Because rubber ages faster than steel under heat and ozone. The cover on the -04 code sits at 17.7 mm outside diameter and is often routed against a hot surface, so it hardens and cracks, water enters, and the wire begins to corrode while the hose still holds pressure in test.

A kink at less than the 90 mm minimum permanently deforms the wire and ovalises the bore, so every subsequent pressure cycle loads the same few strands. The hose passes a static test and fails under cycling, which is why a kinked hose is scrapped rather than straightened.

Abrasion wears the cover from outside in, so the damage is visible and localised, with the braid exposed at 16 to 21.7 mm outside diameter where the cover has gone. Fatigue shows no external wear at all: the cover is intact and the failure is a split along the axis near the coupling.

Yes, and we ask for the failed section plus the route, because the arc is usually the cause rather than the hose. Assemblies are crimped to a recorded diameter and proof-tested, in sizes from 4.6 mm to 10.1 mm inside diameter, with metric, BSP, JIC or ORFS ends.

Price follows the size: 0.33 kg/m at the 3/16 code to 0.6 kg/m at 3/8. Samples are cut free from the production run so a route can be checked against the 90 to 130 mm arc before the order is placed, and a firm figure follows bore, length, ends and destination.