Exceptional Measurement Accuracy with pH Sensor for Low Conductivity Waters

Get the application noteEnsuring the purity of boiler feedwater demands the use of highly capable pH electrodes. 

Power plant cycle chemistry guidelines and standards specify narrow ranges of pH to minimize corrosion of highly valuable components. In addition, makeup water treatment systems using two-pass reverse osmosis optimize performance by careful control of pH between passes. In both of these applications, pH must be measured accurately under the difficult conditions of low conductivity.

The higher the water purity, the lower is its conductivity. As pH electrodes require some conductance to make measurements, establishing precise pH levels in pure waters requires the use of specialized sensors.

METTLER TOLEDO Thornton’s pHure Sensor LE has been designed to provide reliable, continuous, on-line pH monitoring in power plant cycle chemistry.

The pHure Sensor LE is an advanced, single probe pH sensor incorporating a measuring electrode with glass membrane, a reference electrode with liquid junction / diaphragm, and temperature compensator. The built in temperature compensator allows comparison with power cycle chemistry guidelines which are referenced to the industry standard of 25 °C.

This pH solution temperature compensation is only provided in instruments designed for pure water measurement (such as METTLER TOLEDO Thornton pHure Sensors and transmitters). This means that pHure Sensor LE conforms to the requirements of ASTM Standard D5128, Test Method for On-Line pH Measurement of Water of Low Conductivity.

pHure Sensor LE is available with Intelligent Sensor Management (ISM®). This technology offers a number of valuable features, including predictive diagnostics that show when maintenance and calibration will be required. In addition, the pHure Sensor LE can be calibrated away from the measurement point via a PC / laptop then stored until required. If sensor exchange at a measurement point is required, it is a simple case of removing the installed sensor and replacing it with a precalibrated one.


Each power plant is unique, with variables including the incoming water, fuel it uses, amount of power it generates, boiler type or steam generator used and the metallurgy of the water course through the power plant. However, one feature that is common to all is corrosion.

This application note details how the use of pH sensors in pure water applications for power plants helps prevent corrosion. Measuring pH accurately allows the right amount of chemicals to be dosed into the water system. This ensures that enough are added to meet the specifications set to keep the system operating optimally without over addition, which would represent an unnecessary overuse of chemicals and associated overspend.

Download the White Paper

Learn more about ISM software: https://www.mt.com/ism

Visit METTLER TOLEDO Process and Analytics websitehttps://www.mt.com/pro

Find METTLER TOLEDO on Facebook: https://www.facebook.com/mettlertoledo


EPRI Publishes Findings On On-line Chloride and Sulfate Analysis

As fossil plants look for new methods of minimizing corrosion, on-line analyzers are gaining importance.…

Read More

Calculated pH Based on Conductivity

Conductivity sensors can do more than just measure conductivity. Calculated values using conductivity…

Read More

The Easy Way to Minimize Corrosion Control Hydrazine Dosing with ORP

Oxidation reduction potential (ORP) measurement continues to be an essential tool in power plant water…

Read More
View All
Sign-up for
POWER Magazine's
DecisionBriefs
Monthly e-Newsletter!
Email is required