What Is a Stator for Progressive Cavity Pumps?

A stator for progressive cavity pumps is the fixed, helical-lined rubber sleeve that works in tandem with a rotating metal rotor to create sealed cavities that move fluid continuously from inlet to outlet. It is, without question, the most performance-critical component among all progressive cavity pump parts — its geometry, rubber compound, and dimensional accuracy directly determine flow consistency, pressure capability, and service life across every application from sewage screw pumps to food-grade systems.

As a dedicated screw pumps manufacturer, Jingjiang Meijia Pump Industry Co., Ltd. supplies precision-engineered rubber stators, rotors, and complete spare parts for progressive cavity pumps to industries worldwide — delivering consistent quality backed by deep manufacturing expertise.

How a Progressive Cavity Pump Stator Works

The operating principle of a PC pump stator is elegantly simple: the inner bore of the stator is machined (or moulded) as a double-helix with a pitch twice that of the single-helix single screw rotor. When the rotor turns eccentrically inside the stator, a series of sealed cavities forms between the two surfaces and travels axially from suction to discharge — with no valves, no turbulence, and minimal shear. This makes the progressive cavity stator ideal for viscous, abrasive, and shear-sensitive media that would be damaged by centrifugal or piston pumps.

Key dimensional relationships that define cavity pump stator performance:

• Interference fit — the slight size difference between rotor OD and stator bore that creates the sealing force; typically 0.2–1.5 mm depending on application.
• Stator pitch length — determines the volume of each sealed cavity and therefore the pump's flow rate per revolution.
• Eccentricity — the offset between rotor and stator centrelines that sets the cavity cross-section area.

Rubber Compound Selection: The Core of Stator Performance

The rubber stator lining is moulded from an elastomer bonded to a steel tube. Selecting the wrong compound is the leading cause of premature replacement pump stator requirements. The table below summarises the most widely used elastomer types for industrial pump stators:

Stator Applications Across Industries

The versatility of the screw pump stator design makes it applicable across a wide range of demanding sectors. Each industry places distinct demands on stator geometry, compound hardness (typically Shore A 60–80), and dimensional tolerance:

Environmental Water Treatment — Sewage and Sludge

Sewage screw pumps and sludge screw pumps operate with media containing fibres, solids up to 40 mm, and abrasive particles. EPDM or natural rubber progressive cavity stators with a relatively low interference fit (0.3–0.6 mm) are favoured here to reduce torque while maintaining adequate sealing across varying solid concentrations of 1–8% DS (dry solids). Municipal wastewater treatment plants running continuously consume replacement pump stators at a typical interval of 8,000–15,000 operating hours depending on grit content.

Food and Beverage — Food Screw Pump

A food screw pump requires FDA-compliant elastomers — typically silicone or EPDM — that withstand CIP (clean-in-place) procedures with caustic and acid solutions at up to 85 °C. Stator for pump designs in this sector prioritise smooth bore surfaces (Ra ≤ 1.6 µm) to prevent bacterial harbourage and ensure hygienic operation when handling tomato paste, honey, yoghurt, and similar high-viscosity products.

Petrochemical and Oil & Gas

Crude oil transfer demands NBR or FKM rubber stators with high oil-swell resistance. At wellhead applications, the PC pump stator may be exposed to H₂S, CO₂, and temperatures exceeding 120 °C, making compound selection and bond strength between rubber and steel tube critical for reliable uptime. A well-engineered progressive cavity stator in these conditions can achieve pressure differentials of up to 24 bar per stage.

Industrial and Chemical Processing

Paper and pulp mills use single screw pumps to transfer stock suspensions at consistencies of 3–6%; chemical plants depend on FKM-lined industrial pump stators for aggressive solvents and acids. Both sectors benefit from the inherently gentle, pulsation-free flow that screw pump accessories and precision stators enable.

Single Screw Rotor and Stator: How They Work Together

The single screw rotor is the dynamic partner of the stator. Made from hardened stainless steel, chrome steel, or tungsten carbide-coated steel, it rotates eccentrically within the cavity pump stator bore. The quality of this rotor-stator pairing determines the pump's volumetric efficiency — ideally above 90% at rated speed and pressure. Key matching parameters include:

• Interference tolerance — tight control (±0.05 mm) ensures consistent sealing without excessive start-up torque.
• Surface finish — rotor surface roughness Ra ≤ 0.4 µm reduces stator wear and extends pump spare parts service intervals.
• Chrome layer thickness — typically 0.08–0.15 mm of hard chrome (HRC 68–72) on the rotor protects against abrasive wear from suspended solids.
• Pitch matching — the stator pitch must be exactly double the rotor pitch; a mismatch of even 0.5% introduces uneven cavity volumes and pulsation.

Signs of Stator Wear and When to Replace

Monitoring stator condition is essential for avoiding unplanned shutdowns. The following indicators signal that a replacement pump stator is due:

• Flow rate decline of 10–15% at constant speed and inlet conditions — the first measurable symptom of reduced interference fit due to rubber wear.
• Rising motor current with no change in process conditions may indicate stator swelling (chemical attack) increasing torque demand.
• Increased pulsation at discharge points to uneven cavity sealing caused by localised bore wear.
• Visible rubber flaking in the pumped fluid confirms advanced stator deterioration.
• Dry running — even briefly — can cause thermal degradation of the rubber lining in under 30 seconds, requiring immediate stator for pump replacement.

Spare Parts for Progressive Cavity Pumps: What to Stock

A well-managed screw pump accessories inventory minimises downtime. Beyond the progressive cavity pump stator, the following pump spare parts should be held as recommended stock:

Vertical Screw Pump Stator Considerations

A vertical screw pump configuration introduces specific stator design requirements compared to horizontal installations. Because the pump hangs vertically — often submerged or semi-submerged — the stator must accommodate:

• Continuous fluid immersion of the rubber lining, requiring compounds with minimal water absorption (NBR-H or EPDM with ≤ 2% volume swell).
• Self-priming from flooded conditions — the interference fit must be sufficient to maintain sealing even as the pump starts with fluid surrounding the stator externally.
• Installation tooling — vertical extraction of a worn cavity pump stator from a deep sump requires dedicated lifting equipment, making pre-planned pump spare parts management even more important.

About Jingjiang Meijia Pump Industry Co., Ltd.

Jingjiang Meijia Pump Industry Co., Ltd. is located at No. 36 Xintai Road, Jingjiang Economic and Technological Development Zone, Jiangsu Province. As a professional screw pumps manufacturer, the company is dedicated to the production, sales, and after-sales service of single screw pumps and high-quality spare parts for progressive cavity pumps — including precision rubber stators, single screw rotors, and a comprehensive range of screw pump accessories.

Meijia Pump Industry has numerous experienced engineers with technically mature expertise in the design, manufacturing, inspection, and complete sets of screw pumps. Meijia single screw pump products feature advanced technology, complete structure, diverse forms, complete specifications, and durability. They serve industries including environmental water treatment, chemical industry, paper and pulp, food and pharmaceutical, petrochemical, and energy. Meijia also provides universal accessories for global single screw pump brands — including stator for progressive cavity pumps compatible with major market configurations.

The company's after-sales service centre has a team of experienced engineers delivering thoughtful support. Through long-term operation across diverse environments, Meijia single screw pump products demonstrate year-on-year reliability in different working conditions. Meijia Pump Industry is your trusted partner — leaders from all industries are welcome to visit and engage.

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