Selecting a Chemical Metering Pump, by Montana ProMinent Representative - Able Wright, Inc

www.ablewright.com

ProMinent Fluid Controls offers a full line of chemical feed pumps and analyzer / controllers.

Chemical Metering Pumps are often one of the more critical pieces of equipment a wastewater treatment plant has to manage, which makes their proper selection very important. In the following, we provide an overview of some metering pump design issues to keep in mind during unit selection …

1. Flowrate and Pressure Capability – Most chemical metering pumps allow adjustment of both the stroke length and stroke frequency. For best fit, the "normal" flowrate requirements should fall within a range of 30% to 70% of the selected pump´s operating range. This allows some reserve flow capacity, and avoids operating the pump at low stroke frequencies, where they aren´t as accurate. Be sure to allow 10-15% reserve pressure capacity to accommodate the head loss between the pump and the injection point.

2. Chemical Compatibility – Metering pump components (diaphragm, liquid end body, valves, springs, connectors, etc.) must be constructed of the proper materials to insure long, reliable life and proper operation. Dependent upon the chemical service, typical component material alternatives include: stainless steel, polypropylene, PVC, PVDF, and PTFE. We custom build our metering pumps on each application to insure chemical compatibility. The system in the photo above utilizes a PTFE diaphragm & PVDF in the liquid end, valves and piping for pumping 93% sulfuric acid.

3. Upgrade Capability – Metering pump applications vary from very simple on-off systems to systems with analog input signal for dose control, and/or alarm outputs. It is often desirable to interconnect the chemical feed system with a plant SCADA system. Many options are available. Analyzer / Controllers are available (i.e.: pH, chlorine residual, etc.) to automatically control metering pumps to maintain a desired chemical treatment set-point.

4. De-Gas for Hypo – Sodium hypochlorite and other chemicals will off-gas, causing air bound pump heads, loss of prime, and other problems. Alternate liquid ends are available to mitigate this situation and provide more reliable performance, such as:

a) Bleed Valve Liquid End – provides an adjustable bleed valve to return a constant flow to the chemical tank, preventing off-gas vapors from accumulating in the pump head.

b) Auto De-Gassing Liquid End – provides a second discharge valve on the top of the liquid end to vent off-gas vapors and a small return flow, routing them to the chemical tank.

5. Pre-Engineered Systems – Complete packaged systems can be factory designed, assembled, tested, and delivered to the jobsite ready to work. Custom systems can be factory built to your specifications and include components such as:

- Wall or floor-mount skid support, containment deck, and/or enclosure.

- Calibration columns, flow monitors, wye strainers, & pulsation dampeners.

- Backpressure, pressure relief, solenoid, and line valves; pressure gauges.

- Auto-switchover pump control panels, SCADA interconnection panels, etc.

6. Service and Support – Factory support is important, but don´t overlook the benefit of local technical service & support. Chemical feed systems in critical applications such as disinfection cannot be ignored when problems occur. In addition to technical field service, Able Wright provides free phone support to our customers: 24 hours per day, seven days per week. Does your chemical feed provider do this?

Please feel free to contact us if we can be of assistance during selection of your next chemical metering pump system.

Able Wright, Inc. is the Montana and northern Wyoming distributor for ProMinent Fluid Controls. Able Wright is a provider of water treatment equipment and technical services, specializing in disinfection and chemical feed for Montana, Wyoming, Idaho, and Washington. www.AbleWright.com

ProMinent Fluid Controls is the reliable solutions partner for water treatment and a manufacturer of components and systems for chemical fluid handling. The ProMinent USA headquarters are located in Pittsburgh, PA.