The OFS technique is based on the NOAA Wave Propagation Laboratory published paper: Wind Measurements By Temporal Cross-Correlation Of Optical Scintillations showing how this method could be used to measure changes in air flow by analyzing the movement of air through a beam of light.

Further refinements are constantly in process, enabling OFS to become the sensor of choice for industrial customers concerned with Continuous Emissions Monitoring Systems (CEMS) to help reduce greenhouse gas emissions. Today, OFS 2000 flow meters are installed world-wide in a variety of applications where accurate air/gas flow monitoring is a critical factor.

OFS technology has proven successful in a variety of challenging applications that include high temperatures, high and variable opacity and dust concentrations, thermal oxidizers, wet scrubbers, flare stacks, incinerators, SRU, cat crackers, glass furnaces and similar processes with entrained / suspended liquid droplets.

Importantly, OFS measurements are not affected by:

• Distance
• Pressure
• Temperature
• Gas Density
• Moisture
• Opacity
• Gas Composition
• Speed of Sound

The OFS technique is based on optical scintillation (light fluctuation) and temporal cross-correlation (i.e. time of flight). OSi’s patented OFS technique uses a partially-coherent LED and works by clocking the speed of the shadows that pass by the two optical detectors located on the OFS receiver. The accuracy of OFS technology has been proven both in NIST’s wind tunnel and in numerous real-world installations.

OFS is essentially maintenance-free, and with the use of gate valves, they can be easily isolated from the process for window cleaning. Internal diagnostics and self-check built into the OFS are constantly monitoring system health and alert the user if window cleaning is required. (Typically semi-annually or less on the dirtiest stack applications.)

A key advantage of this technology is OFS can install in tight spaces with minimum space requirements of 2 upstream / 1 downstream diameters. No re-piping is needed. Installation is to standard ANSI pattern 4” pipe flange with other size adapters available from the factory. OFS can be installed on live process pipes using hot tap procedure and gate valves for isolation. No shutdown needed.

All OFS models are equipped with 4-20mA Current Loop, RS-232 Serial ASCII, Modbus data outputs, and can be configured with Limited Distance Modem, and Fiber Optic Interface for long-distance serial communications. There are two dry contact relays standard for fault and calibration.

All OFS models also come standard with two 4-20 mA inputs to accept data from temperature and pressure transmitters. Note that this is not a requirement for measurement but will enable OFS to report standard volumetric flow. Users can pair OFS with a concentration analyzer for highly accurate mass flowmeasurements.

• Flare Stacks
• Incinerators
• Thermal Oxidizers
• Terminal Loading Stations
• Boilers
• CEMS
• Secondary Air
• Primary Air
• Sulphur Recovery Units (SRU)
• FCCU
• Bag Houses
• Combustion Air Flow
• Wet Scrubbers

• A full cross path measurement of the process flow
• Non-intrusive measurement (will not create a pressure drop)
• Ability to handle high temperatures
• A stable technology that does not drift
• 5000/1 turn down and ability to monitor from extremely slow to extremely fast flow with one sensor 0.03-170 m/sec
• No re-piping required
  

Optical Scientific, Inc.

Tel: +01 301 963 3630
E infofpt@opticalscientific.com
W opticalscientific.com