pH/ORP sensors fortified for harsh environment

Foxboro has expanded its line of rebuildable, pH and ORP sensor offerings with new electrodes, reference junctions, and electrolytes that make them suitable for harsh processing environments.

Foxboro Model 871PH pH and ORP sensors are now available with new electrodes, including the same domed glass electrodes used in award-winning DolpHin and #61652; pH sensors, as well as with Nafion ion barriers, Variopin quick cable connectors, and protective Polytetrafluoroethylene (PTFE) (Teflon) collars.

"Demand for pH and ORP sensors that are totally rebuildable in the field has been steady and now customers can reduce maintenance costs even further when using them in harsh environments.

The new glass electrode technology we are offering, for example, has already been proven to last twice as long in harsh environments as conventional electrodes," said Ken Brown, vice president and general manager of Foxboro Measurements and Instruments.

All model 871PH sensors include a robust and continuously reusable Ryton or CPVC body with interchangeable measuring electrodes, reference junctions and electrolytes, all of which are replaceable in the field.

They are suitable for most pH and ORP measurement applications and available with a variety of glass pH, metallic pH and ORP electrodes.

Choice of measuring electrode and body material Measuring electrode bodies are available in either Ryton to match the Ryton sensor body or PTFE to be used with a CPVC sensor body.

The electrodes themselves are available in domed, spherical or ruggedised flat glass, antimony, platinum or gold materials.

The domed glass electrode uses the same formulation as the DolpHin sensor and is recommended for the harshest applications: temperatures up to 121 degrees C (250 F) and extremes of chemical concentrations.

This pH glass also increases response speed up to five times and allows longer duty cycles compared to conventional sensors.

The spherical glass electrodes are for standard process applications up to 100C (212 F), and the flat ruggedised glass electrodes are for applications where the process water contains solid materials with pH up to 12 and temperatures up to 85C (185 F).

The metallic electrodes are best for solutions containing hydrofluoric acid or other chemicals; and platinum or gold electrodes for ORP applications.

All electrodes are interchangeable and their plug-in design facilitates quick and easy replacement to address changes in measurement conditions or application.

The expanded 871PH line also features a patented, field replaceable double junction reference with ion barrier for harsh applications containing strong chemical concentrations that may poison the reference electrolyte.

This junction includes a Nafion ion barrier in addition to the external ceramic junction.

This construction allows charge transfer while minimising poisoning of the electrode and preventing silver ion from migrating to the external junction and causing clogging.

An optional PTFE collar is compatible with all of the electrode and junction choices to protect the electrode sides and junction from abrasion and coating.

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