This form of force pump uses a single-acting plunger with inlet and delivery check valves. Plunger withdrawal admits liquid; insertion displaces it toward the delivery line. The calculator combines displacement, entered cadence and volumetric efficiency to estimate flow, then uses entered pressure rise for hydraulic force and power.
Force Pump (Form 1) Interactive Calculator
Vary plunger size, stroke, speed, efficiency, and pressure to see single-acting pump flow, force, and power.
Equation Used
The pump displacement per stroke is the plunger area times stroke length. Multiplying by strokes per minute and volumetric efficiency gives delivered flow. Pressure acting over the plunger area gives the required hydraulic plunger force, and flow times pressure gives hydraulic horsepower.
- Single-acting pump delivers once per stroke cycle.
- Water is treated as incompressible. Pressure means the rise across the pump, not a pump pressure rating.
- Volumetric efficiency is entered, not predicted from cadence. Hydraulic horsepower is fluid power, not required motor input. Animation cadence is illustrative.
- The default 36.765 in stroke is an illustrative input, not a documented pump dimension. Enter the actual working stroke for a comparison.
A plunger displaces liquid through check valves
The plunger enters and leaves a working chamber through a seal. Withdrawal increases available chamber volume; insertion decreases it. Pressure differences open the appropriate inlet or delivery check valve and oppose reverse flow.
An air vessel can reduce discharge pulsation by temporarily storing energy in compressed gas. The drawing shows that concept, but it does not size the vessel, seals, valve passages or pipework.
Pressure capability and suction conditions are distinct. Pressurizing the delivery side does not remove the inlet’s filling constraints, and an external gland does not authorize adjustment while equipment is running or pressurized.
Single-acting liquid displacement
The arrangement illustrates a basic reciprocating positive-displacement pump. Plunger pumps can be incorporated in many liquid-handling systems, with materials, drive and valves selected for the actual fluid and duty.
Historical hand pumps and modern multi-cylinder pumps should not be assumed to share the same capacities or details. This page’s “form 1” is an illustration label, not a standardized commercial pump type or a manufacturer rating.
Displacement, estimated flow and hydraulic output
For plunger diameter D and stroke L in inches, area is A = πD²/4 and geometric displacement per delivery stroke is V = AL. Divide cubic inches by 231 to obtain US gallons.
Estimated flow is Q = VNη in US gallons per minute, where N is delivery strokes per minute and η is the entered volumetric efficiency as a fraction. Geometric displacement is shown before this efficiency adjustment.
For pressure rise P in psi, ideal hydraulic plunger force is F = PA in lbf. Fluid power is approximately QP/1714 mechanical horsepower. Seal friction, drive losses and acceleration forces are not included; required shaft or operator power is not the hydraulic-output figure.
Pressure and efficiency are independent inputs. The tool does not predict either from pump speed, inlet conditions or a connected pipe system.
Example: an entered single-acting duty
Use a 3 in plunger, 8 in stroke, 30 delivery strokes/min, 90% volumetric efficiency and 40 psi pressure rise. Geometric displacement is 0.245 US gal per delivery stroke, and estimated flow is 6.61 US GPM.
Ideal hydraulic plunger force is 282.74 lbf and fluid power is approximately 0.154 hp. These figures do not include friction or prove that a particular handle, drive or pump can sustain the duty.
Changing only cadence to 60 delivery strokes/min doubles estimated flow and hydraulic power. Plunger force stays the same. The assumed 90% efficiency remains fixed because the tool does not model valve timing or filling losses.
Actual duty requires the complete system
A single-acting pump delivers on one stroke direction. Other arrangements can use both sides of a piston or several phased cylinders, but their displacement, rod area and pulsation must be evaluated for the actual configuration.
Use equipment ratings, inlet requirements, pressure controls and manufacturer procedures for a real pump. The calculator does not determine allowable speed, an air-vessel charge, human endurance, fire-stream reach or service intervals. It supplies no running packing adjustment, valve retrofit or pressure-vessel venting instruction.
Frequently asked questions
Does Geometric displacement already include efficiency?
No. It is area times stroke, converted to US gallons. The efficiency input is applied only when calculating estimated delivered flow.
Are the gallon units US or imperial?
US gallons. The conversion is 231 cubic inches per US gallon.
Is Hydraulic Power the motor size?
No. It is estimated power delivered to the fluid. Drive and mechanical losses and duty requirements must be considered separately.
Why does pressure change force but not the flow readout?
Pressure, cadence and volumetric efficiency are independent inputs. The model does not calculate how pressure changes leakage or attainable speed.
Does higher cadence automatically reduce efficiency?
Not here. The entered efficiency remains constant until you change it. Actual filling and valve behavior require pump data.
Does the default long stroke come from a named pump?
No. It is an illustrative starting value. It should not be used as a construction dimension or claimed commercial specification.
Pump references
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