A plunger pump is a reciprocating positive-displacement pump: a plunger changes a fixed chamber volume while inlet and discharge checks direct the liquid. This worksheet uses an explicitly single-acting ideal geometry and keeps theoretical displacement separate from declared efficiency-adjusted delivery.
Single-Acting Plunger-Pump Flow Explorer
Enter plunger diameter, stroke, crank speed, plunger count, and a declared volumetric-efficiency factor. The worksheet reports theoretical displacement per crank revolution, declared average delivery, US flow, and ideal mean plunger speed.
Equation Used
- Each plunger is single acting with one discharge stroke per crank revolution.
- All plungers have the same diameter and stroke and are evenly phase-staggered in the illustration.
- Liquid is treated as incompressible for the displacement ledger.
- Declared volumetric efficiency combines fill and leakage effects but is not derived from pressure, speed, fluid or valve data.
- No pressure, power, torque, NPSH, cavitation, pulsation, temperature, wear, material, rating or service-life prediction is made.
Separates theoretical single-acting displacement from declared delivery and replaces the disconnected legacy media with one connected plunger, packing, chamber and check-valve sequence.
A moving plunger changes a fixed chamber volume
The US Department of Energy groups plunger pumps with reciprocating positive-displacement pumps that move a discrete liquid volume between inlet and discharge valves. In the representative sequence, retraction increases chamber volume and the inlet check is shown open; advance decreases chamber volume and the discharge check is shown open. The packing remains stationary while the plunger slides through it.
The calculation is configuration-specific
The Hydraulic Institute distinguishes single- and double-acting plunger pumps and simplex or multiplex arrangements. This worksheet covers only identical single-acting plungers with one displacement stroke per crank revolution. Manufacturer data is still required for actual pressure, speed, fluid, valve, inlet, power and materials limits.
Separate theoretical displacement from declared delivery
The Hydraulic Institute states the general controlled-volume relationship as rate of flow equals displacement times cycles per unit time times volumetric efficiency. Here the geometric displacement is reported before the declared efficiency factor is applied. Mean plunger speed is the total out-and-back distance 2S times revolutions per second.
A transparent declared example
With 25 mm diameter, 30 mm stroke, three single-acting plungers, 600 rpm and declared volumetric efficiency 0.94, theoretical displacement is 44.2 mL per crank revolution. Declared average delivery is 24.9 L/min, or 6.58 US gpm, and ideal mean plunger speed is 0.60 m/s.
What this ideal displacement ledger omits
Actual delivery depends on pump design, valve dynamics, pressure, fluid properties, inlet conditions, leakage and speed. Reciprocating discharge is pulsating even when multiple phases reduce ripple. This page does not predict pressure, power, torque, NPSH, cavitation, acceleration head, pulsation, temperature, wear, packing life, maintenance intervals, failure causes or suitability.
The former universal pressure and efficiency ranges, brand and site examples, service-life claims, clearance and surface-finish limits, diagnostic rules and operating recommendations are removed.
Plunger-pump worksheet questions
Is the efficiency factor calculated?
No. It is a declared input.
Does plunger count change displacement?
Yes, linearly for identical single-acting plungers. Phase staggering primarily changes the instantaneous flow pattern.
Does this cover double-acting pumps?
No.
Can the result select a pump or driver?
No. Use tested manufacturer performance data and the complete system duty.
Reciprocating pump references
- Hydraulic Institute Pump FAQs: rate of flow equals displacement times cycles per time times volumetric efficiency.
- Hydraulic Institute Pump Types: plunger pumps within reciprocating positive-displacement classifications, including single/double acting and simplex/multiplex forms.
- US Department of Energy, Variable Speed Pumping: reciprocating pumps displace discrete liquid volume between inlet and discharge valves.
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