Flow metering and flow control

If your pumping application requires accurate, metered flows, with difficult fluids, in a rugged environment, you should consider an Accustaltic Pump. Combining both flow control and flow metering into one device, the accustaltic pump is accurate and repeatable. There are no delicate parts, fins, or bearings to be fouled by the metered fluid.  If fluid compatibility is an issue, tubing can be mixed and matched to provide the perfect combination of performance and chemical resistance.

Using the pump as a flowmeter:

The accustaltic pump is positive-displacement pump, meaning that each turn pumps a known amount of liquid. this means that by simply counting the number of turns, you can know exactly how much fluid you are pumping. This can be by a hall-effect or reed switch on the shaft, or by a rotary encoder. You can see both above and below the simple shaft sensor that tells the rate controller or PLC exactly how fast the pump is turning. Brackets and mounts are available for many common speed sensors.

Great for:

• Continuous flow industrial processes
• metered dosing
• Viscous, abrasive, corrosive, caustic and shear sensitive materials
• Dividing one flow into multiple metered flows
• Lubricant pumping
• Glue pumping
• Very large flows (to 40 GPM), where the pulse of a hose pump is undesirable.
• Pressures to 60 psi and higher(4 bar)

Tubing displacement and flow curve linearity:

The tubing displacement is how much fluid is pumped with one full revolution of the pump. For the pump to have a linear flow rate, this displacement must remain constant over the speed range of the pump. In an Accu-Staltic pump, displacement changes very little with speed or time when properly installed.

Below is an actual evaluation using Norprene 3/8" ID tubing. Curves will vary slightly with the type and size of the tubing you choose.

The flatness of the curves at left shows the uniformity of the pump as a flowmeter over the various speeds.

Note that under higher inlet manifold pressures (blue line at left), the soft Norprene has an increase in displacement, as the tube stretches. Stiffer tubes such as Suprene, Prothane, and Santoprene will be less affected by this phenomena.

Linear Flow Rate:

A good metering pump has a linear flow rate: ie: when the speed of the pump doubles, the flow doubles. You can see in the graphs below, how the flow rate of a typical configuration remains linear. The more linear the flow rate, the more accurate your application.

In the table at left, you can see that even after 100 hours of pumping, the flow rate per second is nearly unchanged.

It is interesting to note the slight loss of linearity when the pump is required to lift (pull vacuum) as shown in the green line. The effect really only becomes significant at very high pump RPMs. This is due to wearing and loss of elasticity in the rubber compounds over time and is normal. Flooding the pump inlet, and keeping to lower pump speeds can pretty much keep this phenomena under control.

In cases where the inlet must lift, or higher accuracy and wide speed ranges are required, choosing other, more elastic hose polymers such as Prothane II, will maximize the pump's linearity.

Want to Learn More?

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