Don't confuse cavitation with aeration. The sounds are similar. This is like trying to breathe through a wet handkerchief. This causes major damage. Piston slippers will fail, metal eroded etc. Check for oil viscosity, blocked pickup screen or intake hose, excessive revs. Get it fixed NOW.
Aeration is when air is pulled into the system, usually on the intake side of the hydraulic pump. This will sound growly and functions will be spongy. The oil will look frothy milky or white. Repair the air leak, pump seal, clamp tension, hose etc.
The barrel is the block or rotor. It contains the pistons (plungers). Excessive pressure or spikes will cause a fracture. Add-on hydraulics can cause internal loading (spikes). Listen for engine lugging at idle as a good indicator.
The set plate retainer is the piston retaining plate. PQ curve is set too high causing stress. Adjust to specifications. Check for excessive case pressure. Restricted case leakage line. High internal leakage.
Over pressure. Adjust pressure to correct specification. Spike pressure rises. Check hammer / accumulator.
I AM AFTER SPECIFIC PARTS FOR MY HYDRAULIC PUMP, SWING MOTOR OR TRAVEL MOTOR. WHAT INFORMATION DO YOU REQUIRE?
The more information you can give us the easier it makes our job. Machine model, the model of your pump, swing or travel motor. All these details assist us in confirming that we have stock on the shelf or whether we have to procure from our overseas sources.