Pump Selector
Enter your flow rate and differential pressure to match a progressive cavity pump, selected against real digitised performance curves. See the operating speed, volumetric efficiency, motor sizing, and the full pressure-line family for your duty.
Enter a duty point to begin
Provide your flow rate and differential pressure. We'll match RDJ progressive cavity pumps using their real datasheet flow curves, and show the operating speed and efficiency.
How it works
From duty point to pump in three steps
Enter your duty
Flow rate and differential pressure, with your fluid type and viscosity. Any common units — we convert automatically.
Compare matches
We rank progressive cavity models by fit, showing stage build, operating speed, power draw, and price.
Review the curve
Inspect flow-vs-speed and power curves at your duty point, then request a formal quote from RDJ.
This tool provides indicative sizing and budget pricing for early-stage selection. Final pump selection, materials, and pricing are confirmed by RDJ Engineering against your full process conditions.
Selection guide
Understanding your pump selection
A quick guide to how progressive cavity pumps work and how to choose seals, rotor coatings, and stator elastomers for your fluid.
How does a progressive cavity pump work?
A helical steel rotor turns inside a resilient rubber stator, forming a chain of sealed cavities that carry fluid smoothly from suction to discharge. Because each turn moves a fixed volume, it is a positive-displacement pump: flow is set by speed and is almost independent of pressure.
That makes them ideal for viscous, shear-sensitive, or solids-laden fluids — sludge, slurry, polymer, molasses — that centrifugal pumps struggle with. Flow is gentle, near-pulsation-free, and accurately proportional to speed, so they also make excellent metering and dosing pumps.
How do I read the performance curves?
The Flow vs Speed curve is close to a straight line — double the speed, roughly double the flow. Your duty point is marked in orange; where it sits on the line tells you the rpm the pump must run at. The Power vs Speed curve shows the absorbed shaft power at your pressure, which drives motor sizing.
A shaded band appears on the curves when the fluid is abrasive — it marks the speed you should not exceed to protect the rotor and stator. A good selection keeps the duty point in the middle of the usable band, leaving headroom for wear and turndown.
Pressure, stages and turndown
Each stageadds pressure capability — about 6 bar per stage here. A higher-pressure duty simply needs more stages — which adds length and cost. We pick the smallest stage build that meets your pressure so you don't pay for capability you won't use.
Because flow follows speed, a variable frequency drive (VFD) gives excellent turndown — trim the flow to duty, dose accurately, and start softly to reduce wear and inrush. Running slower than maximum is almost always good for pump life.
Handling abrasive media
Grit and mineral solids wear the surface where the rotor meets the stator. The proven defence is to run the pump slower— lower rubbing velocity dramatically extends element life. That's why our selector derates the usable speed as abrasiveness rises, and will steer you to a larger, slower pump for gritty duties.
Material choices then buy back some speed and life: a hardened or tungsten-carbide-coated rotor paired with a natural-rubber or HNBR stator resists abrasion far better than the standard build.
Viscosity, suction and cavitation
Progressive cavity pumps handle very high viscosities, but thick fluids struggle to flow into the pump. For viscous or high-solids service, keep suction pipes short and large-bore, minimise lift, and consider a hopper with a feed screw, or a flooded or force-fed inlet.
The critical rule is simple: run viscous media slower. Thick fluid cannot fill the cavities fast enough at speed, so the pump starves and cavitates. A frame good for ~700 rpm on a thin fluid may be limited to a few hundred rpm by the time you reach ~1,000 cP, and far less beyond that — so viscous duties need a bigger pump turning slowly, not a small one spinning fast. The selector applies this derate automatically and shows the resulting speed limit.
Working the other way, a thicker fluid reduces internal slip, so volumetric efficiency improves with viscosity. Watch NPSH on hot or volatile fluids to avoid cavitation.
Installation & protecting your pump
- Never dead-head it. As a positive-displacement pump it will build pressure until something fails — always fit a pressure-relief / safety valve on the discharge.
- Never run it dry. The stator is destroyed within minutes without lubrication — fit dry-run / low-level protection.
- Mount on a rigid baseplate with correct shaft alignment and a guarded coupling.
- Allow space to withdraw the rotor and change the stator during maintenance.
Choosing seals, rotors & elastomers
The three choices that most affect pump life and price. The Pump build options panel lets you set all three, and Apply recommended for this duty will suggest a matched set.
Shaft sealing
Water, thin effluent, and low-cost duty where a small controlled leak to atmosphere is acceptable. Cheapest to buy and re-pack, but needs periodic adjustment and wets the drive end.
Clean to lightly loaded fluids where leakage is not acceptable — food, clean water, light chemicals. Zero-drip and low maintenance, but the faces need clean product and will wear quickly in grit.
Abrasive, hazardous, or dry-running-risk duties. A barrier flush (clean liquid or quench) keeps grit off the faces — the standard choice for sludge, slurry, and anything you can't afford to leak.
Severe or high-availability service where downtime is expensive. Pre-set cartridge swaps out in minutes with no field setting — best total cost where the pump runs hard and continuously.
Rotor material & coating
Non-abrasive to lightly loaded fluids. Good corrosion resistance in the standard 316-family; the most economical rotor where wear isn't the life-limiter.
Mild to moderate abrasion. A hard chrome layer (~1000 HV) roughly doubles rotor life over bare steel at modest cost — the usual first upgrade for sludge and dosing.
Highly to severely abrasive slurries and tailings. A sprayed tungsten-carbide coating (~1200+ HV) gives the longest element life and lets the pump run faster than bare steel at the same abrasion level.
Stator elastomer
The default all-rounder — wastewater, sludge, oils and general transfer up to ~80 °C. Water, sewage, mineral oils, fats, dilute acids/alkalis. Avoid ketones, strong oxidisers, and aromatic solvents.
Hot water/CIP, mild chemicals and polymer where oils aren't present. Hot water, steam, ketones, dilute acids/alkalis, polar solvents. Avoid mineral oils, fats and fuels (they swell it).
Aggressive chemistry, solvents/fuels, and high-temperature fluids to ~150 °C. Aggressive chemicals, fuels, aromatics, oils, high temperature. Avoid hot water/steam, ketones and amines.
The abrasion specialist — grit, sand and mineral slurry in cool aqueous service. Abrasive slurries, mine water, mild aqueous media. Avoid oils, fats, fuels and temperatures above ~70 °C.
Abrasive duty that is also warm or contains some oil, where natural rubber won't survive. Abrasive and oily media, dilute acids/alkalis, warm service. Broader chemistry than natural rubber.
Chemical compatibility notes are a guide only — always confirm the elastomer against your exact fluid, concentration and temperature. RDJ Engineering will verify the final material selection.
Not sure which pump is right?
Send us your duty point and fluid details — our engineers will confirm the selection, materials, and pricing for your application.