When a hydraulic pump reaches the "overhaul point", it is normal for
its internal components to present all sorts of wear and damage. In a
swashplate type pump, for example, piston shoes almost always show
signs of abrasive wear - high speed sliding contact with the
swashplate makes any particle trapped under the shoe count. In rare
cases the amount of wear reaches "extravagant" proportions -
something you can witness on these pictures, which exhibit piston heads
worn out flat! The balancing cavity is gone and the shoe is probably
twice as thin (compared to a "normal" one). Apparently, there was no
one around the equipment to shut it down and send the pump to a
workshop at first (second, third..) sign of efficiency loss.
