In almost every hose failure we attend, the hose had been telling somebody for weeks. The signs are not subtle once you know what you are looking at, and a two minute walk-round catches most of them.
1. The cover has worn through
The single most common one. You will see a flat, shiny or frayed patch where the hose has been rubbing on a bracket, the chassis or another hose. If you can see wire through the rubber, that hose is finished and the machine should not be worked.
Equally important is what it has been rubbing on. If you fit a new hose into the same unprotected run, you will be doing this again.
2. Rust or staining at the ferrule
Brown staining creeping out from under the crimp means water has got into the wire reinforcement and it is corroding. The hose can look perfect along its length and still be about to go at the fitting.
This is one of the more urgent signs, because failures at the crimp tend to be sudden rather than gradual.
3. A weep that keeps coming back
Oil appearing at a fitting after it has been nipped up is not a tightness problem. It means the seal, the crimp or the sealing face has failed, and tightening it further usually makes it worse by damaging the face.
4. Blistering or bulging
A raised bubble in the cover means oil has got between the layers of the hose. The inner tube has failed and the reinforcement is holding the pressure on its own. This one is a stop-now sign.
5. Kinking, twisting or a tight bend
A hose bent tighter than its minimum bend radius, or twisted during fitting, is being stressed every time the system pressurises. Failures from this show up near the fitting rather than in the middle.
A useful check: the printed lay line down the side of the hose should run straight. If it spirals, the hose was twisted when it was fitted.
6. The hose has gone hard
Rubber ages, especially in heat. A hose that feels stiff and does not flex the way its neighbours do has lost its flexibility and will crack. Squeeze a few hoses on the same machine and the tired one is usually obvious by feel.
7. It is simply old
Age on its own is not a defect, but it does change the odds, and a hose that has been on a hard-working machine for many years deserves proper scrutiny rather than a glance.
What to do about it
Anything at stage 4 or worse should stop the machine. Everything else is a planning question, and planning is the cheap option: a hose changed in your yard costs a fraction of the same hose failing on site with a callout attached.
If you want the whole fleet gone through properly, that is what a hose inspection is for.