Progressive cavity pumps, also known as eccentric screw pumps or helical rotor pumps, are often used for applications like chemical metering, dosing and transfer of viscous fluids. However, there are some disadvantages to consider when using progressive cavity pumps, especially for low flow applications involving progressive cavity metering pumps, progressive cavity dosing pumps and low flow progressive cavity pumps.

Maintenance and Repair Complexity

Progressive cavity pumps contain many parts like the rotor, stator, couplings and seals that need to fit together precisely. This complex design makes maintenance and repair more difficult compared to other pump types. Replacing worn parts often requires dismantling large sections of the pump.

High Costs

Not only are progressive cavity pumps initially more expensive than alternatives, but maintenance costs are also high due to expensive replacement parts and long downtimes for repair work. Stators typically have a high replacement frequency, adding to the total cost of ownership over time.

Poor Suitability for Abrasive Fluids

The close clearances between the rotor and stator wear quickly when handling abrasive mixtures. For applications involving solids, slurries or other abrasive media, a progressive cavity pump may not provide a long service life.

Issues at Low Viscosities

At low fluid viscosities, the rotor can experience slippage against the stator interior as the fluid is unable to generate sufficient pressure within the cavities. This reduces efficiency and precision for low viscosity metering and dosing needs.

Large Space Requirements

To generate pressures, progressive cavity pumps must be significantly larger than some alternative designs. The long casing and multiple components require more installation space as shown below:

Risk of Dry Running Damage

If run dry, even briefly, the clearance between the rotor and stator will be lost. This can quickly damage both parts through friction and overheating. A flooded suction line is critical to protect the pump internals.

Complex Pump Selection Process

With multiple factors to consider like flow rates, pressures, temperatures, and fluid properties, selecting the correctly specified progressive cavity pump can be more complex than simpler designs.

Limitations for Low Flow Applications

The long casing and space required for eccentric motion means that low flow progressive cavity pumps have limitations, such as only being able to handle flows down to approximately 0.5 L/min. This restricts their use for precise micro-dosing and analytical testing needs.

Fluid Temperature Sensitivity

The rubber stator is susceptible to swelling or degradation depending on fluid temperature. This can impact the clearances and change flow rates. Most progressive cavity pumps also have maximum operating temperatures below 100°C.

Potential Vibration Problems

At high speeds, the eccentric motion of the rotor can cause vibration issues. Shaft seals may fail prematurely due to excessive vibratory stresses.

Experience Requirements

Specialized engineering knowledge is required to properly select, install, operate and maintain progressive cavity pumping systems compared to simpler designs.

While progressive cavity pumps provide benefits for specific transfer and metering applications, their complex design introduces various disadvantages. Careful consideration is needed regarding the total cost of ownership, fluid properties, installation constraints, and engineering experience available before specifying a progressive cavity pump.