Mettler Toledo InPro 6850i G Gas-Phase Oxygen Sensor

Overview

Mettler Toledo InPro 6850i G is an amperometric oxygen sensor for measuring oxygen in the gas phase directly in the process. It belongs to the InPro 6000 G series, which Mettler Toledo describes as providing high operational availability together with excellent measurement performance. The Mettler Toledo InPro 6850i G is installed in the process without an expensive gas sample conditioning system, and maintenance or replacement can be carried out without interrupting the process. It uses Intelligent Sensor Management, or ISM, so that the sensor carries its own calibration data and diagnostics and is recognised automatically when it is plugged into a compatible transmitter.

In the Gulf region, the typical question is how to prove that a vessel, tank or powder line is truly inert. Chemical, petrochemical, pharmaceutical and food plants in Oman and the GCC use nitrogen blanketing and inertization to prevent explosive atmospheres and oxidation, and the Mettler Toledo InPro 6850i G gives them a direct oxygen reading in the vessel or vent line. It complements the gas analyzers already listed by Seven Star LLC, including the Southland OMD-21 portable percent oxygen analyzer, the Systech ZR810 zirconia oxygen analyzer for nitrogen and the Systech ZR810 zirconia oxygen analyzer for argon and hydrogen. Seven Star LLC supplies the Mettler Toledo InPro 6850i G with engineering support in Muscat.

Operating Principle

The Mettler Toledo InPro 6850i G and its series companions work on the amperometric, polarographic principle, in accordance with ISO 5814 and EN 25 814. Oxygen from the gas diffuses through an oxygen-selective membrane to a platinum cathode, where it is reduced. The resulting electrical current is proportional to the oxygen partial pressure at the membrane, and an electrolyte-filled inner body completes the circuit with an anode and a silver/silver chloride reference. The sensor produces a current of 50 to 110 nA in ambient air at 25 degrees Celsius, and its residual signal in nitrogen is no more than 0.1 percent of the air signal.

For the Mettler Toledo InPro 6850i G the inner body is the ppm version with a platinum anode, which gives a detection limit of 0.03 volume percent oxygen, equal to 300 ppm of gas. Accuracy is better than plus or minus 1 percent of the reading plus 0.03 volume percent, and the 90 percent response time is 20 seconds or better at 25 degrees Celsius. The measurement is only slightly affected by many organic and inorganic substances, and it is insensitive to humidity, so there is no need to dry the gas before the measurement. A built-in RTD provides automatic temperature compensation.

Engineering Design of the Mettler Toledo InPro 6850i G

The Mettler Toledo InPro 6850i G has a sensor shaft of 12 mm diameter in 120 mm or 220 mm immersion length, with a Pg 13.5 threaded sleeve and a K8S cable connection for the digital ISM signal. The wetted parts are stainless steel 1.4404, equal to AISI 316L, supplied with a 3.1 material certificate and a surface roughness below 0.4 micrometre Ra, and a C22 wetted-material version is listed in the ordering table. The oxygen-selective membrane is a PTFE, silicone and PTFE sandwich that is FDA compliant and reinforced with a steel mesh, and the wetted O-rings are silicone approved to FDA and USP Class VI, with Kalrez available.

The Mettler Toledo InPro 6850i G is designed for ease of service. Mettler Toledo quotes two-minute maintenance because the membrane body and the exchangeable inner body are replaceable parts, and a membrane kit includes four membrane bodies, an O-ring set and 25 mL of electrolyte. It is steam-sterilizable, with a mechanical temperature resistance of minus 5 to 121 degrees Celsius, tolerates pressures of 0.2 to 9 bar absolute during measuring and 12 bar absolute mechanically, and fits the InFit 761 static housing and the InTrac 777 e and 797 e retractable housings.

Key Features

The following features explain the position of the Mettler Toledo InPro 6850i G in nitrogen blanketing and inertization monitoring:

• In-situ gas-phase oxygen measurement that avoids an expensive gas sample conditioning system.
• Sensor maintenance or replacement without process interruption, using a two-minute membrane body exchange.
• ISM digital technology with Plug and Measure operation and diagnostics for predictive maintenance.
• Insensitivity to humidity and negligible interference from many organic and inorganic substances.
• ATEX certification as Ex ia IIC and FM intrinsic-safety classification for Class I, II and III, Division 1 hazardous locations.
• Wetted stainless steel 1.4404 (316L) with a 3.1 material certificate and a surface finish certificate.
• FDA and USP Class VI compliant O-ring and membrane materials, with a MaxCert certificate package.
• Steam-sterilizable to 121 degrees Celsius and suitable for pressures up to 9 bar absolute during measuring.

Industrial Applications

Mettler Toledo lists nitrogen blanketing, inertization monitoring, vent gas, centrifugation, drying, pelletizing, storage and packaging among the typical applications of the Mettler Toledo InPro 6850i G in chemical manufacturing, together with milling, powder storage and packaging in chemical and food powder processing. In Oman, that maps to nitrogen-blanketed storage tanks and reactors in petrochemical and specialty chemical plants, inerted dryers and centrifuges, powder silos in food and fertiliser plants, and vent lines where the oxygen level must stay below a defined limit before flare or release.

Biotechnology and pharmaceutical facilities use the Mettler Toledo InPro 6850i G for storage and packaging areas, and breweries use it for CO2 purity checks before recovery. Because the Mettler Toledo InPro 6850i G is certified for hazardous locations, it can be fitted to equipment in classified areas at Sohar, Duqm and Salalah when connected through a suitable intrinsically safe transmitter. Seven Star LLC supplies the sensor with the matching housing, cable and calibration accessories, and our team can review the process connection and the transmitter before an order.

Technical Specifications

The table lists data for the Mettler Toledo InPro 6850i G from the Mettler Toledo technical data sheet for the InPro 6000 G gas phase oxygen sensor series.

How to Order

To request a formal quotation for the Mettler Toledo InPro 6850i G, tell us the immersion length, the process connection or housing, the wetted material and the transmitter you intend to use. Seven Star LLC supplies Mettler Toledo process sensors to customers in Oman and the GCC, with engineering support from our instrumentation division in Muscat, and the technical data sheet attached to this page.