How to Perform a Direct Measurement
This sampling technique is utilized to determine actual emission rates from various sources (i.e. separator vent, tank vessel manifold, wellhead vent etc.), and can be quantified to determine a facility’s PTE. OTA utilizes an easily transportable metering tube with size varying orifice plates designed based on the American Gas Association, Report No. 3 – Third Edition, Part 3, “Orifice Metering of Natural Gas” standards (AGA, 1992). Our proprietary calculation program utilizes the corresponding equations from Part 3 to determine flow rates. Our highly trained field technicians choose an orifice based on site-specific characteristics to ensure the vapor is measured accurately. A data logger is installed inline, downstream of the orifice at a precisely located tap hole to measure pressure and temperature differentials. Readings are measured in increments contiguously over a twenty-four hour testing period. This measuring technique yields detailed vapor flow results that show total, incremental, and peak flows.
A natural gas sample is extracted directly from the tank battery by securely fastening a vacuum pumped sample cylinder to the single point of emission, impeding atmosphere contamination.
This test measures the storage vessels’ working, breathing, and flash emissions.