The vanes maintain continuous contact with the cam ring as they sweep, so torque is delivered with little variation across a revolution and pressure ripple is low. That produces noticeably less noise and vibration than gear motors, which is often the reason they are chosen.

One using an elliptical cam ring with two opposed pressure zones, so the radial hydraulic loads on the rotor cancel each other instead of being carried by the bearings. It removes the main life limitation of unbalanced designs and is standard on industrial units.

By springs and by fluid pressure fed behind them in the rotor slots, which together push them outward against the cam ring. That combination maintains sealing across the whole speed range, including at start-up and at very low speed, before centrifugal effect contributes anything at all - which is why a vane motor starts reliably rather than needing to come up to speed first.

Torque is lost immediately and wear accelerates on both the vane and the cam ring. Sticking is caused by contamination or by varnish from degraded oil, so fluid condition matters more here than on a gear motor - a vane must slide freely in its slot for the motor to work at all.

Moderate ones, below what axial piston motors reach. Vane motors are chosen for smoothness and quietness at reasonable pressure rather than for maximum pressure capability, so a system designed around high pressure generally points to a piston motor instead, and specifying a vane motor there means running it at the top of its range continuously.

Machine tools, injection moulding, industrial equipment installed indoors, and other duties where noise and vibration matter to the people working nearby and pressures are moderate. They also appear in constant-duty industrial applications where their smooth output and reasonable efficiency suit continuous running better than a noisier gear motor would.

Yes, and vane and cartridge replacement is a normal service operation on industrial designs - some are built as replaceable cartridges specifically so the wearing parts can be renewed without replacing the whole motor. Ring condition should be checked at the same time, since a worn ring will destroy new vanes.