Piston Pump
A piston pump pumps fluid with pistons reciprocating on a swash plate or an eccentric, and it is the standard solution for high pressure systems. Typical continuous operating pressure is 250–350 bar and volumetric efficiency is above 95%. Its flow rate can be adjusted steplessly by changing the swash plate angle.
The piston count is usually an odd number (7 or 9); this reduces flow ripple and therefore pressure pulsation. In the axial piston type the pistons are arranged parallel to the shaft and their strokes are set by the swash plate angle. As the angle approaches zero the pump delivers no flow; this is called destroking.
- Why it is preferred: high pressure, high efficiency, and variable flow rate in the same body.
- Cost: high price and marked sensitivity to fluid cleanliness; fine filtration is essential in these systems.
- Where you see it: excavators, large mobile cranes, and load sensing circuits.
Machines with this pump type generally come with closed center and load sensing valves. Here an intermediate lever position determines not just the flow area but also the flow rate the pump will deliver; therefore correctly calibrating the relationship between joystick and lever travel is even more important for precise motion.
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