Progressive cavity pumps are unreliable and can often run dry and fill with excessive grit.

• A. True
• B. Not necessarily
• C. False
• D. Cannot be determined

Answer: (C)

Progressive cavity pumps are designed to move slurry with solids by trapping fluid in alternating cavities formed between a helical rotor and a flexible stator, producing a steady, low-pulsation flow. This makes them reliable for wastewater applications where solids are present, provided they are operated within their limits and properly maintained. The idea that they are unreliable and often run dry or fill with excessive grit isn’t accurate. Running dry is harmful to any positive-displacement pump because the elastomer stator needs the pumped liquid for lubrication and cooling, so proper priming and avoiding dry running are essential. Grit can wear the stator and rotor over time and shorten life, which means maintenance and wear-resistant materials may be needed for abrasive slurries, but with correct screening, material selection, and routine upkeep, PCPs handle solids well. In short, when used correctly, progressive cavity pumps are not inherently unreliable and are not prone to routinely running dry or becoming clogged with grit.