What are metering pumps?

A metering pump is designed to transfer a precise volume of fluid and are characterized by their accuracy.  One of the standards we often refer to is the American Petroleum Institute (API) Standard 675, which stipulates performance characteristics for controlled volume positive displacement pumps.

We offer two brands of metering pumps, the Hayward Z series (available with either analog or digital interface) and the Wanner Engineering S & P series.  All are positive displacement pumps utilizing one or more diaphragms to displace precise volumes of fluid with the primary difference being that the Wanner P series is capable of higher pressures and there are more models contributing to a broader range of flows.

S Series : 0.5 to 3 GPH with output pressures up to 145 PSI

S Series Solenoid Metering PumpsThe S Series solenoid metering pumps by Wanner Engineering are for the most common lower flow and pressure general chemical metering applications.  The least expensive design provides a manual dial stroke control and the more expensive models provide full pulse-in control and analog control to set the pulse frequency from an external source. 

The price range for S Series solenoid pumps is $350 to $2,290 depending upon materials of construction. 

There is some overlap between the S Series and Z Series metering pumps (below); pricing and features are similar however the S Series has a broader range of materials to choose from and for our International customers, can be provided with optional EU or UK compatible power plugs.

Z Series : 1 to 29 GPH with output pressures up to 232 PSI

Z Series solenoid metering pumpsThis series of metering pumps consists of three models with each available in either constant, proportional or timed dosage configurations.  The Z series style pump are relatively inexpensive ($500-$1,100) and is comprised of a control unit that houses the electronics and magnet, and a diaphragm in contact with the liquid to be dosed.  These are not self-priming pumps, you must initially prime the pump chamber before dosing will begin.  Although they can be used for water, most applications for this style metering pumps are for chemical products such as ulphuric Acid)  The body and connectors are made of PVDF, the diaphragm is made of PTFE and the check balls are made of ceramic..

The Z Series metering pumps are energy efficient using solenoids which only draw the power required for the given flow rate and pressure.  The digital interface version's intelligent display enable intuitive programming in as many as five languages.

 

P Series : 0.6 to 843 GPH with out pressures up to 2,500 PSI

Wanner Engineering P Series Metering PumpsThis series of metering pumps consists of six models and are capable of high pressures.  The P series is a completely different style of metering pump than the S and Z series style solenoid driven metering pumps.  The P series is based upon the Wanner Engineering Hydra-Cell™ design, using one or more hydraulically balanced diaphragms to precisely dose fluids in compliance with API 675 performance characteristics standards of linearity, repeatability and accuracy.

Thus the P Series metering pumps have a broader application base, not only due to their higher pressure capabilities but also due to their sealless design which lends itself to pumping viscous, abrasive and other "difficult to handle" fluids such as isocynates, polyols, blowing agents, catalysts, acids and de-ionized water.

Unlike the commodity style S and Z Series metering pumps, the P series flow rate is dictated by the shaft speed of the pump motor.  The pump motors are typically 1800 RPM and a gearbox is used to mechanically reduce the pump shaft speed.  The flow rate can only be varied by varying the pump shaft speed, which is typically achieved using a programmable variable frequency drive (VFD).  For more complex pump control we offer a touch-screen PLC interface.

How to choose a metering pump?

Start by defining the performance parameters such as the flow rate (and range if it is to be variable) and the pressure required.  Generally speaking if it falls within the capabilities of the S or Z Series, this will be your least expensive option.  The P Series is generally applied to difficult fluids, higher flow rates and pressure and for applications requiring a high level of user feedback or control.

Comparing the S & Z series metering pumps, the Z series offers more features than the S Series where they overlap, although most of the Z series pumps have higher flow and pressure capabilities compared to the S series.

When in doubt, contact us !  The best way for us to begin assisting you is to use our online application based inquiry form; we can usually reply with a proposal within 24 hours.