O2E2 Dust Explosion Oxygen Safety Monitor For Dense Phase Pneumatic Conveying

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• Transport dust, flakes and solids safely
• Reliable laser diode technology
• Fast response--seconds
• Sample flow sensing, automatic backflush
• Nitrogen purge for Class I Div 2 hazardous locations
• Pressure and temperature corrected sensor, insensitive to movement
• Autocalibration built in
• Low volume particle pre-filters, 5 um and .01 um, included

Here is a truly digital oxygen analyzer with analog and digital interfaces for control, display, and datalogging of either nitrogen blanketing of powder storage or of nitrogen content in recirculating pneumatic transport systems.

Two Stage Filtration - Programmable Filter Backflush. The Oxigraf O2E2 is the next generation process monitor for dust conveyance. To keep the analyzer from being contaminated by the process dust, Oxigraf uses a two-stage filter. Each filter is independently backflushed while your gas sampling continues. No interuption of monitoring for periodic filter purge.

Tunable Diode Laser Spectroscopy. The Oxigraf is the next generation oxygen safety sensor. Laser diode absorption spectroscopy assures stable, long-life oxygen measurement: there are no electrochemical cells to replace or paramagnetic sensors to recalibrate. The laser diode, derived from high reliability telecommunications VCSEL (vertical cavity surface emitting laser) diode technology, is rated for more than 500,000 hours mean time to failure. The laser diode is thermally and electronically tuned to measure the absorption of oxygen at 763 nm, and also periodically measures the background to provide an automated zero. Pressure and temperature corrections are made to yield the correct oxygen concentration as the weather changes.

Temperature, Pressure, and Humidity. Temperature and pressure corrections are important. The Oxigraf sensor is corrected to within ±0.2 % over pressure changes of 50% and temperature changes from 0 to 50 C°. An oxygen sensor that only measures oxygen partial pressure instead of concentration, would report an oxygen variation of 2% with a 10% variation in barometric pressure. Humidity changes can also change the oxygen dilution caused by humidity, and the Oxigraf sensor is not corrected for humidity. A hot, wet day relative humidity of 50% at 37 C° (99 F°) corresponds to an absolute humidity of 3.2%. Such a water vapor dilution causes a variation from the cold, dry air oxygen concentration of 20.9% to 20.2%, a change of 0.7%.

Fast Response. Industrial processes need fast measurement of oxygen and timely update of operating conditions. The Oxigraf Safety Monitor responds in less than a second. The transit time of the gas sample through the sampling tube may be 1 second per meter of sampling tube. To respond within 5 seconds, a monitor with a 1 second response time would need to be placed within 4 meters of the potential hazard. Electrochemical sensors may require 20 or more seconds to respond to large, abrupt changes in oxygen concentration.

Sample Flow Monitor. The Model O2E2 includes a sampling pump, hydrophobic filter, and flow sensor. Any flow blockage or pump failure is reported as a low flow fault Warning and initiates a back-flush sequence. The set point for flow restriction is user adjustable. Status of the flow is reported via the communication port, and a warning condition is triggered as well. Thus remote monitoring of the flow system is enabled.

Remote Display and Remote Maintenance. The Oxigraf Safety Monitor includes various communication outputs. A 4-20 mA current output may be programmed to relate oxygen concentration. The Horn-Strobe/Alarm relay may be enabled by a programmable combination of the two independent high/low alarm settings, the System OK/Fault or the operation Warning information. Up to five relays are available to denote System OK, various Warning states, two independent high/low alarms, and a general alarm.

Insensitivity to Movement. The Oxigraf technology has no moving parts, in contrast to paramagnetic technology. Laser diode technology will have no false alarms due to equipment vibration and is transportable.

Code Access. The 12-key capacitive-touch panel permits access control for maintenance and unit calibration.

The Oxigraf O2E2 Product Development Team