Pumping Difficult to Handle Liquids with Wanner Hydra-Cell Pro^® Pumps

A lot of the applications we assist with do not require high pressure. It is dirty, viscous, non-lubricating or hazardous liquids, and the sealless Wanner Hydra-Cell Pro^® pump is required due to its sealless design. The Hydra-Cell Pro product line can output pressures from 50 to 5,000 PSI. Most of our applications require lower pressures. This article covers those duties, where the design beats packing and close-clearance pumps, and what to consider when you size and pipe the system.

A Hydra-Cell Pro^® is a positive-displacement pump with no mechanical seal, packing, or other dynamic barrier between the liquid and the room. Each shaft turn moves a fixed volume. Discharge pressure is whatever is required to move that volume downstream. Flow follows RPM. The hydraulically balanced diaphragm is what separates this pump from progressing-cavity, gear, vane, lobe, air-operated diaphragm and peristaltic designs. Most of those other designs are damaged by solids due to tight clearances, need the process liquid to cool and lubricate the mechanism, or will not hold high pressure on continuous duty.

Simplicity of Design

A lot of pumps were built for one liquid. Hydra-Cell Pro pumps were built to be reliable. That is why Hydra-Cell Pro pumps are used for so many “hard to pump” liquids.

Liquids Containing Particles

Maximum particle size is set by how far the check valves open. Those valves keep flow going inlet to outlet. Piston, plunger and AODD pumps use the same type of check valves. Progressing-cavity, gear, vane, lobe and peristaltic pumps control the flow with the pumping mechanism itself. Tight clearances on PC, gear, vane and lobe pumps result in wear, or you adjust them by sacrificing  efficiency. Peristaltic and AODD pumps stay in the low-pressure range. They do give more suction lift, have a larger free passage and can pump higher viscosity liquids than a Hydra-Cell Pro pump.

Pumping Slurries

Liquids with a high solids load is a slurry. Hydra-Cell Pro pumps handle non-precipitating slurries to concentrations of about 25%. That is past where a PC, gear, vane or lobe pump still pumps efficiently. Peristaltic pumps are great for slurries because they will pass large diameter and long solids without grinding them.

Almost any reclaimed or recycled stream carries solids. The Hydra-Cell Pro pumps check-valves requires less filtration. Piston and plunger pumps have similar valves, but they also have a packing or seal with a very tight gap. Their manuals often call for 25-micron filtration to protect that seal. A Hydra-Cell Pro has no such seal, so particles larger than 25 microns are not a wear issue for Hydra-Cell Pro pumps. Coarser media costs less and you change it less often.

Viscous Liquids

Some pumping mechanisms work better with viscous liquids than others. Peristaltic pumps do well. PC, gear, vane and lobe pumps gain efficiency on viscous liquids and like a lubricating film. Hydra-Cell Pro pumps will function for liquids having viscosities up to 1,100 cps (about 5,200 SSU). What they add on that duty is lack of a mechanical seal and the ability to carry solids with the viscous liquid.

Non-Newtonian fluids change viscosity with shear. At low pressure people often use a centrifugal pump. A Hydra-Cell Pro has a short, high-frequency stroke and will move sauces (ketchup), bentonite and paper/pulp slurry without the solids and viscosity limits of a centrifugal pump.

Non-Lubricating Liquids

Thin liquids — water, fuel, solvents, liquefied gases, surfactants — starve close-clearance pumps of the cooling and lubrication film they require. Slip (ineffency) climbs fast as pressure rises. Centrifugal pumps handle those fluids at a modest pressure. When the application needs higher discharge pressure, a PD pump is requried. Check-valve flow control holds volumetric efficiency better than a PC, gear, vane or lobe style pump. Centrifugal pumps are also a poor fit for chemical metering due to low flow, steady rate, or requirement for operating consistent flow across a variable pressure range.

Hazardous Liquids

Hazardous can mean temperature, chemistry, toxicity or environmental risk. Those applications benefit from a simple pump design with few leak paths and minimal requirements for personnel to maintain the pump. The only Hydra-Cell Pro parts in contact with the liquid are the check valves and the elastomers. The components in contact with the liquid are rated for 15°F to 250°F. Fewer parts also means more material choices: Hastelloy and ceramic valves for aggressive chemistry, stainless alloys or tungsten carbide for abrasion.

No mechanical seal reduce chance of fugitive emissions. Packing and seals on piston, plunger, PC, gear, vane and lobe pumps wear and then leak.

Pump Sizing and Piping

Hydra-Cell Pro pumps will lift, so they can fit some low-NPSHa applications.  Locate the pump as close to the feed tank as you can. On a pressure-fed inlet, oversize the suction pipe to reduce turbulence. Cavitation and a closed suction will not damage the Hydra-Cell Pro pump but the pump only operates smoothly when the flow rate at the pump inlet is the same or higher than the required discharge rate.

Solids and viscous liquids usually benefit from a slower RPM — “oversizing” the pump. Lower speed and a larger internal path reduce wear on the valves and make it easier for the liquid to fill the head.

The pump is not magic. It competes across several design families because the process end is simple and sealless.

Related Articles

• Hydra-Cell Pro design overview
• Comparison to piston and plunger pumps
• Comparison to progressing cavity pumps
• Comparison to external gear pumps
• Comparison to AODD pumps
• Peristaltic vs AODD
• Horsepower for high-temperature liquids