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Frequently Asked Questions
How does a piston pump differ from a plunger pump?
The seal moves with the piston inside the cylinder bore, rather than being stationary packing the plunger passes through. That makes the bore's condition part of the sealing system, and it makes the arrangement compact and efficient - but less tolerant of abrasives than a plunger design.
What is variable displacement and why does it matter?
Altering the stroke - in an axial pump by changing the swashplate angle - so flow can be varied continuously at constant drive speed. The system then delivers only the flow it needs rather than producing full flow and dumping the excess over a relief valve, which saves substantial energy in any duty cycle with idle time.
What is the difference between axial and radial piston pumps?
Axial pumps arrange pistons parallel to the drive shaft acting against a swashplate, giving a compact package and easy variable displacement. Radial pumps arrange them perpendicular to the shaft around a cam, which suits very high pressures and gives a robust, if bulkier, construction.
Why is fluid cleanliness so critical?
Because the close-fitting pistons, bores and control mechanisms have very small clearances that contamination scores and jams. Most premature hydraulic piston pump failures trace to filtration or fluid condition rather than to the pump, which is why cleanliness targets are specified and should be met rather than approximated.
Where are high-pressure piston pumps used?
Hydraulic power transmission above all - presses, machine tools, injection moulding, mobile plant and aircraft systems - plus high-pressure process duty. Wherever controllable flow at high pressure is needed from a compact unit, this is generally the pump family used.
Can they handle water or thin fluids?
With difficulty in standard form, since most are designed for hydraulic oil that lubricates the pistons and bores. Water-glycol and water-based fluids need specific designs and materials, and running a standard hydraulic piston pump on a thin non-lubricating fluid causes rapid wear.
What are the signs of wear?
Falling flow at a given speed, rising case drain flow, increasing noise, and slower actuator movement in the system. Case drain flow is the most useful diagnostic on a hydraulic piston pump, since it rises measurably as internal clearances open up and can be checked without removing anything.