Buying a progressive cavity pump is not like buying a centrifugal pump, where you pick a size, bolt it on, and forget about it. With a PCP, every major decision, the stator rubber, the rotor alloy, the number of stages, comes back to one question: what exactly are you pumping? Get that right and the pump runs for years. Get it wrong and you will be ordering a new stator within months, plus paying for the downtime while it is being replaced.
Here is the selection process we walk customers through, in the order that matters.
1. Start with the fluid, not the flow
Before you look at any catalogue, write down what the fluid actually is. Is it abrasive, like slurry or grit-laden wastewater? Is it chemically aggressive, like acid or solvent? Does it contain fibres or stringy solids? Does it have to stay intact, like flocculant or fruit pulp? Temperature matters too, because the stator elastomer has a working range and will fail if you push it past the limit.
This one paragraph of information decides more about the pump than anything else. Abrasive media want a harder stator material and a coated rotor. Aggressive chemicals want a compatible elastomer and stainless alloy. Shear-sensitive media want low speed. The fluid dictates the materials, and the materials dictate the price and the life.
2. Flow rate and the linear speed rule
Work out the flow you need in m³/h. A PCP delivers flow in direct proportion to rotor speed, so you are really choosing a cavity size and a speed range. A bigger cavity (the number after the series code, like the “025” in SGP025) moves more fluid per revolution. The SGP series, for example, spans 0.5 to 300 m³/h across its cavity sizes.
One practical tip from the shop floor: do not size the pump at its absolute maximum speed. Run it a bit slower than the catalogue maximum and the stator lasts noticeably longer, because every compression cycle costs a little rubber.
3. Pressure and the stage count
Add up the total pressure your line needs: static head, friction losses through pipes and fittings, and any backpressure at the discharge. Then match it with stator stages, because stages are what create pressure in a PCP.
- 1L single stage, up to 6 bar
- 2S two stages, up to 12 bar
- 3S three stages, up to 18 bar
- 4S four stages, up to 24 bar, and custom builds beyond that
A common mistake is ordering one stage too few “to save money.” The pump then runs at the edge of its pressure rating, the stator slips and wears fast, and you replace it twice as often. One extra stage is cheap insurance.
4. Viscosity and solids
Progressive cavity pumps are famous for handling thick fluid, but “thick” is not a number. Check the viscosity in centipoise if you can. Most SINOR PCP series handle up to 700,000 to 800,000 cP, which covers sludge, molasses, paint, and adhesive. If the fluid also carries solids, note the particle size and whether the solids are soft (fibres, clumps) or hard (sand, grit). Hard abrasive solids point you toward a hardened or coated rotor and a wear-resistant stator compound.
5. Material compatibility, and why it decides the price
The stator elastomer and the rotor alloy are the two most expensive decisions in the whole order. There are no universal materials, only correct ones for a given fluid.
For the stator: NBR for oils and fuels, EPDM for water, steam, and most chemicals, FKM for high-temperature and aggressive fluids, HNBR for extreme wear and oil-and-gas duty. For the rotor: SS304 for general and food service, SS316L for pharma and chlorides, duplex for aggressive chemicals, chrome-plated alloy or tungsten-carbide coating for abrasion. Full comparison tables live in our material guide if you want the details.
6. Delivery, mounting, and the small stuff
Once the fluid, flow, pressure, and materials are settled, the rest is configurable: direct-coupled or bearing-frame design, vertical or horizontal mounting, hopper feed with a bridge-breaker for sticky sludge, sanitary clamp connections for food duty, and the motor brand you prefer (SEW, NORD, and others). These choices do not change the pump’s performance, but they do change how easy it is to install and maintain on your site.
The honest shortcut
If this feels like a lot, it is, and that is exactly why we answer selection questions for free. Send us the fluid description, flow, pressure, and temperature, and we will come back with a model, a stage count, and a material recommendation within 24 hours. It saves you from learning the hard way what an under-specified stator costs.