Validation of OGI sensitivity

Supporting the validation of optical gas imaging systems

In 2016, the US EPA released a regulation, called Subpart OOOOa that recommends leak detection and repair (LDAR) for oil and gas operations sites. It recommends Optical Gas Imaging as the BSER (Best System of Emission Reduction) to use for leak detection.

NPL's miniature Controlled Release Facility (mini-CRF) provides a system to test compliance of OGI cameras to the OOOOa standard. It contains an array of Mass Flow Controllers (MFCs) that control the flow of gas from cylinders of propane and methane and a balance gas of air or nitrogen. These are used to achieve the required test gas mix by dynamic dilution, following guidance in BS EN ISO 6145-7:2010.

Mini-CRF capabilities

The miniature Controlled Release Facility (mini-CRF) provides a system to test compliance of OGI cameras to the OOOOa standard. It controls the flow of gas from cylinders of propane and methane to an emission node where it provides a test source for demonstrating compliance with the OOOOa sensitivity requirement.

                   
The summary specifications are:

• Comprised of four MFCs – two at 500 ml/min (maximum) for methane and propane, one at 10 l/min (maximum) for methane and one 100 l/min (maximum) for air/nitrogen.
• Computer controlled operation that can log the outputs of all of the MFCs at about 0.25 Hz. All can be calibrated and are traceable to the SI using primary piston flow meters.
• Portable system weighing around 10 kg that can be used either on site at NPL or at external sites to support testing and training.

In addition to providing the required hydrocarbon release defined in the regulation, NPL has the capability to control other parameters which influence successful gas detection by OGI systems. These include:

• Control of the temperature differential between the gas and the surroundings using a thermally controlled board.
• Control of the wind speed to a maximum of 10 m/s using a tuneable fan and measured by an anemometer.
• Assessment of the range dependence to a maximum of 20 m.

Other test facilities for OGI cameras

In addition to the mini-CRF, NPL can also provide other controlled sources of emissions for testing and training purposes. This includes the larger CRF facility for fugitive emissions system validation and the leak simulation facility that can generate controlled gas leaks from a wide range of realistic sources, including pipe flanges.

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