Measuring oxygen

Strict control of oxygen levels in many industrial processes is vital to guard against product deterioration and explosions. But most O2 measurement systems are costly to purchase and maintain. Amperometric systems redefine O2 measurement.

Oxygen levels in industrial processes are heavily controlled to contain the risk of explosion of flammable liquids and dusts, as well as to protect products against oxidation. Not only is oxygen monitoring a critical issue in transport systems, storage tanks or centrifuges, the presence of oxygen can also negatively affect the yield of a chemical reaction in a vessel.

When selecting a vendor for a measurement system, technologies and solutions abound, but in many cases a trade-off exists between sufficient performance and reliability, and reasonable maintenance effort and system availability. In order to function correctly, paramagnetic systems need to protect the measurement cell from heat, moisture and/or corrosive gases. However, the more instruments there are between the process and the sensor, the longer the response time will be and the higher the probability of system failure.

Looking at the field of dissolved oxygen measurement however, membrane-based amperometric sensors using the Clark principle have for decades demonstrated optimum performance in a wide range of applications ranging from fermentation processes in breweries, to biopharmaceutical industries, to chemical process applications. This technology, with a proven industrial track record due to its simplicity and ruggedness, is ideally suited for the in-situ measurement of gaseous oxygen.

Amperometric sensors can be maintained in two minutes, with minimum impact on the running process. All that is required is to replace the membrane body and fill it with fresh electrolyte solution. Subsequent calibration can be performed on site using air as a calibration gas.

All amperometric sensors from Mettler Toledo are available in digital versions equipped with Intelligent Sensor Management (ISM) technology offering built-in self-diagnostic abilities in order to detect early signs of failure and alert users. With ‘Plug and Measure’, pre-calibrated sensors can be immediately used in the process. Further features include retractable housings for sensor extraction without process interruption, transmitters for signal conversion and connection to a variety of process control systems. The complete system is available with ATEX Zone 1/FM Class 1 Div 1 approval if required.