Industry requirements for safer, trouble-free, and continuous process operations need to be balanced with cost control, maintenance resources, budgets, greater efficiency, and better use of primary raw materials.
Oxygen (O2) level monitoring in safety-relevant applications can be significantly improved with in situ Tunable Diode Laser (TDL) measurements that not only avoid the drawbacks of conditioning and sampling systems, but also allow fast measurement directly in the process line or vessel. In situ TDL measurements also allow for operations close to Limiting Oxygen Content levels, reducing the costs of inerting without compromising on safety.
TDL oxygen sensors work on the principle of laser absorption spectroscopy and measure O2 directly from the gas stream, without any sampling or conditioning. These sensors are often part of a more complex safety installation which monitors the O2 measurement, verifies the sensor, and validates inerting.
TDL sensors for process applications have two basic design types, cross-stack and probe-type, and consist of a laser diode and detector contained in a single unit, requiring a single flange connection.
Moisture and dust can severely affect the performance of extractive systems, but since no sampling or conditioning is required, the blow-back filter process adaptions on the GPro 500 TDL are especially good at coping with process gases that contain particularly high levels of dust or liquids. The METTLER TOLEDO M400 transmitter can also be used to determine the interval and duration of blow-back cycles to clean filters inside to out.
TDL sensors are practically drift free and can be calibrated just once a year, representing a huge saving in time spent on maintenance and operational downtime. In situ TDLs only need air as a calibration gas, and no nitrogen (or any other 0% O2 calibration gas) is required. The highly stable zero point of TDL sensors are proven over extended time periods, regardless of the harshness of the process conditions, taking a considerable logistics burden away from technicians.
METTLER TOLEDO TDL sensors allow for direct control self-testing via a DCS (Distributed Control System), commonly used in manufacturing processes that are continuous or batch-oriented. This means that verification measurements in air can be quickly and inexpensively conducted from a control room, considerably increasing the system’s operational uptime, and leads to greater productivity and process availability.
Download our white paper to understand the benefits of TDLs and how to integrate them into a DCS system for fully automated O2 verification.