Wanner Hydra-Cell Pro^® Pump vs. Progressive Cavity Pumps

Both pumps are positive displacement and both move difficult liquids. Wanner Hydra-Cell Pro^® pumps are a sealless design. Progressing cavity pumps perform better for some applications. This article compares the two and gives field examples.

Overview

Wanner Hydra-Cell Pro^® pumps cover 0.06 GPH to 157 GPM at 30 to 5,000 PSIG. Chambers come simplex, triplex and quintuplex, synchronous and asynchronous. Notable points:

• Gentle, nearly pulse-free flow
• Self-priming
• Solids and slurries to about 0.8 mm
• Liquid temperature to about 230°F
• Runs dry without damage
• Viscosity to about 20,000 cP

Progressing cavity pumps can handle much larger flow (past 2,000 GPM), higher viscosity, bigger particles and thicker slurries. Pressure usually tops out around 700 PSIG, and the design is sealed. Notable points:

• Smooth flow
• Self-priming
• Solids and slurries
• Liquid temperature to about 350°F
• Some designs will run dry with faster stator wear
• Viscosity to about 1,000,000 cP

Designs

A Hydra-Cell Pro pump moves liquid through one, three or five chambers on a common inlet and outlet. A hydraulically balanced diaphragm changes chamber volume. That seal is not a rubbing stem seal; it rolls in and out of the chamber. A hydraulic column drives it and resets each stroke against discharge restriction. The hydraulic liquid is normally synthetic motor oil. Wear parts in that loop are few.

A progressing cavity pump turns a rotor inside a stator. The helix traps pockets of liquid and walks them to the discharge. The wear face is the squeeze between rotor and stator; you can tighten that a little as it wears. Packing or a mechanical seal isolates the gearbox from the process and will leak as it wears. Reverse the rotation and flow reverses. The pump can sit horizontal or vertical.

Comparing the Two Designs

Pick the pump that matches the duty. PC pumps take larger solids, higher viscosity, thicker slurry and hotter liquids.

Hydra-Cell Pro pumps wear the check valves first and will not pass the particle sizes a PC pump can. Some Hydra-Cell Pro pumps models can be installed  vertically; most are built to install horizontal.

Water-treatment slurries such as lime or milk of magnesia can use either. Hydra-Cell Pro pumps has the edge when you want sealless containment and short, inexpensive field repairs.

Large PC pumps cost more to keep running. Stators and rotors are long and awkward to change. A Hydra-Cell Pro check-valve kit comes out from the head with little pipe work.

Robustness

After more than 30 years working with Hydra-Cell Pro pumps, it is hard to name a more compact, rugged pump in this flow range. Inlet cavitation and dry running do not wreck the hydraulic end, so you need fewer low-level switches just to protect the pump. Run it dry before long storage, especially where it can freeze.

Shaft rotation either way is fine, which simplifies the installation. Pumps through 20 GPM bolt to a NEMA C-face motor with an adapter that lines the shafts up so the coupling doesn't wear.

Frequency of Maintenance

Life depends on materials and duty. Hydra-Cell Pro check valves come in stainless, ceramic, tungsten carbide and Hastelloy. On 25% lime slurry for flue-gas desulphurization, ceramic valves have lasted 4,000 to 6,000 hours in our experience. As they wear, efficiency falls and the flow gets less smooth. They do not suddenly quit or leak process liquid. The other scheduled maintenance is an oil change every 4,000–6,000 hours of use, by model and pressure.

Published stator/rotor hours are scarce because wear follows the liquid and how often the pump runs dry. PC pumps also have packing or a mechanical seal on the rotor shaft. That work needs tools and usually a bench. They are a poor fit when the user is unable to repair on site.

Precision Metering

A PC pump can be set-up to move a fraction of a GPH. That does not make it an API 675 compliant metering pump. Wanner Hydra-Cell Pro pumps meet those requirements with regards to linearity, repeatability and steady-state accuracy.

Deciding Factors

Start with flow, pressure and the liquid. Where both pumps can handle the flow and pressure, the Wanner Hydra-Cell Pro is usually the smaller, more efficient and more reliable choice.

A PC pump can cost less at high flow and low pressure. It is also the better pick for very high viscosity, concentrated slurry, particles larger than about 0.8 mm, as well as stringy solids.

Related Articles

• Pumping difficult liquids with Hydra-Cell Pro pumps
• Comparison to piston and plunger pumps
• Comparison to external gear pumps
• Comparison to AODD pumps
• Hydra-Cell Pro design overview
• Hydra-Cell Pro metering pumps