In the materials rather than the principle. Both have an inner tube, reinforcement and a cover, but thermoplastic hose extrudes the tube and cover from plastic and usually reinforces with braided synthetic fibre instead of steel wire.

The differences that follow are weight, bend radius, surface and electrical behaviour. Thermoplastic is considerably lighter for the same bore and pressure, bends tighter, has a smooth cover that resists abrasion and shrugs off oil and dirt, and can be non-conductive. It also comes in long continuous lengths and in colours, which rubber hose does not do easily.

Rubber holds an advantage in high-temperature tolerance and in flexibility at low temperature, and is generally more forgiving of rough handling.

They are not straight substitutes. Check temperature range, fluid compatibility and minimum bend radius before swapping one for the other in an existing installation.

Wherever hydraulic equipment is used near live electrical conductors, and it is normally a mandatory requirement rather than a precaution.

The clearest cases are insulated aerial work platforms used by utility crews, hydraulic tools used on or near overhead lines, and rescue equipment that may be used around damaged electrical infrastructure.

The hazard is that a conventional hose with steel wire reinforcement is a conductor running the length of the boom directly to the operator. Non-conductive thermoplastic hose uses synthetic fibre reinforcement and dielectric materials throughout, and is tested and certified to a stated voltage.

Two cautions. The rating applies to the complete assembly including fittings, so a non-conductive hose with standard fittings is not a non-conductive assembly. And the rating depends on the hose being clean and undamaged - contamination on the cover can provide a conductive path, so these assemblies are inspected and tested on a schedule.

Yes, within its range - thermoplastic constructions cover pressures comparable with braided rubber hose, and specialist very-high-pressure thermoplastic hose is made for hydraulic tooling.

Hydraulic torque wrenches, bolt tensioners, rescue tools and jacks routinely operate at pressures well above general hydraulic circuits and use thermoplastic hose precisely because it combines that pressure with light weight and flexibility - a rubber hose of equivalent rating would be too heavy and stiff to handle.

The constraint is usually temperature rather than pressure. Thermoplastic loses strength as it warms more noticeably than rubber, and published pressure ratings assume a stated temperature. A hose adequate at ambient may not be at the temperature found near an engine or in a hot process area.

Read the pressure rating together with the temperature curve rather than as a single number.

Because it can be made in long continuous lengths, it takes repeated coiling without damage, and its smooth cover slides rather than catching as it winds.

Rubber hose is produced in limited lengths and its textile-finish cover grips against itself and against the reel. Thermoplastic hose is extruded continuously, so a single uninterrupted length of many metres is straightforward, and the slick cover feeds and retracts cleanly.

The tighter bend radius also lets the reel drum be smaller for a given hose size, which makes the whole assembly more compact.

One caution specific to reels: thermoplastic takes a set if left tightly coiled for long periods, particularly in the cold, so a hose can come off the reel with a memory curl. It relaxes in use and in warmth, but it is worth knowing before assuming the hose is faulty.

It uses fittings and crimp specifications made for thermoplastic hose, which are not the same as those for rubber hose of the same nominal size.

The reason is that the materials behave differently under a crimp. Plastic does not compress and recover the way rubber does, so the crimp diameter, the insert profile and the shell design are all specified differently. A rubber-hose fitting crimped onto thermoplastic can appear perfect and either leak or release under pressure.

As with all hydraulic hose, the assembly is rated as a system: use the hose manufacturer's fittings and their published crimp figures, with the correct dies.

On non-conductive assemblies this is doubly important, because the fittings form part of the dielectric rating. Fitting a standard conductive end onto certified non-conductive hose produces an assembly that fails its purpose entirely while looking correct.