Particle Time of Flight
By T Moorhouse (ex-Photon Control), contributor, S Ante, Photon Control R&D, Braver, Martec Asset Solutions
Electricity+Control (July 2015) pages 18 – 20)
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The goal of this project was to create precise optical flow meters for the oil and gas industry optimised for measuring flare gas flow in explosive atmospheres. The flow meters had to incorporate enclosed electronics yet allow easy installation, accessibility and servicing.
Optical techniques for measuring gas flow use the principles of optical velocimetry, which measures gas flow velocity. From this, we can obtain the volumetric flow rate. Within this model, there is both Laser Doppler Velocimeters (LDV) and optical transit time velocimeters. Within the latter, there is a further subdivision into laser-two-focus (L2F) and scintillation-based and absorption based transit time velocimeters. This article addresses L2F.
As with any technology, there are numerous practical issues that a user may encounter in real world installations. Contamination of optical components is an inevitable concern when contemplating a flow measurement system using optics in a flare gas environment. This is especially so with flare gas, which generally has a variable composition and liquid content. We addressed this issue at the beginning of our Optical Gas Flow Meter (OFM) probe development by implementing a shroud design. This solution dramatically improved the resistance of the device to concurrent liquid hydrocarbons, which are known to cause problems for other types of flare meters. window surfaces. This has now become a standard feature for all OFMs produced by the R&D at companies represented by the authors.
- Flow measurement in explosive atmospheres can be complex.
- Optical flow meters use the principle of optical velocimetry.
- Volumetric flow rates can be determined from gas flow velocity.