Most cable problems are selection problems that waited a few years to show themselves. Four questions catch nearly all of them before the order goes in.
Start with the duty, not the diameter
What current, what signal, what voltage drop can the circuit afford over the real route length? Sizing from the load schedule and route length beats sizing from what fit the gland last time. When in doubt, the conductor goes up a size far more cheaply before the pull than after it.
Let the route pick the construction
Buried runs want armour or duct protection. Tray runs share space with noisy neighbours, which is where shielded pairs earn their cost. Anything that moves — doors, festoons, carriers — needs a construction designed for flexing, not a fixed-installation cable asked to improvise. The route survey is half the specification.
Respect the environment line by line
Temperature extremes, oils, UV exposure, moisture and rodents each veto certain jacket compounds. A cable that is perfect electrically and wrong chemically fails just as surely — only slower, and usually after the warranty conversation would have been easy.
Ask what arrives with the drum
A batch test record, a length tag and a construction datasheet turn commissioning surprises into checked boxes. If documentation is an afterthought at quotation time, it will be unavailable at troubleshooting time. Buy the paper trail with the copper.
