The Metering Research Facility:
Typical Projects Performed

by Ed Bowles Flow Measurement Section Manager Southwest Research Institute

The GRI Metering Research Facility (MRF) works with flow meter and valve manufacturers, natural gas production and gathering companies, natural gas transmission pipeline companies, and local natural gas distribution companies. The following five projects are typical MRF projects.

1. Accurate Gas Measurement at Custody Transfer Points. Deregulation and open access in the U.S. natural gas industry in the 1990s built a competitive market, motivating more efficient company operations. Gas companies are facing constant pressure to earn greater profits and cut costs. With many more participants buying and selling gas in the United States marketplace, the accurate measurement of gas at custody transfer points is paramount (a custody transfer point is the location where gas changes ownership, such as from gas supplier to gas consumer). If there is a bias in the custody transfer meter, that bias penalizes one side of the transaction, thus, increasing operating costs and hurting competition.
   
   The MRF provides value to the industry through its ability to identify and eliminate gas measurement bias errors. Since the inception of the MRF in 1991, a research initiative has been underway to identify and eliminate the measurement biases associated with commonly used gas-metering equipment (e.g., orifice flow meters, turbine meters, ultrasonic meters, etc.).
   
   
2. Gas Meter Calibrations. Gas companies find operational and economic advantage in having gas flow meters calibrated before field installation. The MRF provides accurate flow meter calibrations traceable to the U.S. National Institute of Standards and Technology (NIST)---correcting flow meter bias errors as small as 0.05%.
   
   The MRF is one of just a few facilities in the world that can perform high-accuracy, gas flow meter calibrations under field-like operating conditions. The closed-loop, re-circulating, gas flow calibration facilities at the MRF provide maximum controllability of pressure, temperature and flow rate, resulting in stable flow conditions over long testing times. A key feature of the MRF is its primary calibration system based on gyroscopically-balanced weigh tanks, the most accurate means known for measuring gas mass flow rate.
   
   
3. Gas Sampling. In addition to focusing on volumetric flow rate measurement, the MRF program also addresses natural gas composition determination (i.e., heating value determination). As an example, the MRF is evaluating commonly used gas-sampling methods to determine which provide the most accurate characterization of natural gas mixtures flowing through pipelines. The American Petroleum Institute (API) and the United States Gas Processors Association (GPA) are using the results of this research work to update their natural gas sampling standards. It has been estimated that the economic impact of improved gas sampling techniques for custody transfer is on the order of $50 million annually in the United States.
   
   
4. Flow Conditioners. The piping geometry upstream of a gas flow meter can create flow field distortions that can adversely affect measurement accuracy. If these flow distortions are allowed to propagate to the flow meter, measurement bias errors can result.
   
   A device called a flow conditioner is sometimes placed upstream of a flow meter to help eliminate flow distortions before they reach the meter and bias the measurement. An extensive research program has been conducted at the MRF to characterize the flow performance of commercially available flow conditioners.
   
   
5. Energy Rate Measurement Research. In the United States, natural gas is bought and sold based on the amount of energy delivered. This requires that both gas volume and heating value be measured accurately. Gas volume is usually measured with a conventional flow meter, such as an orifice meter or a turbine meter. Heating value is normally determined from a compositional analysis of the gas mixture. The compositional analysis is typically acquired via gas chromatography. The MRF, with co-funding from GRI and the United States Department of Energy, is researching more cost-effective methods for determining energy flow rate.

The MRF is a one-of-a-kind facility, unique in its capability. The MRF has a reputation in government circles and throughout the U.S. natural gas industry as the best-equipped facility/resource for advancing the state of the art of gas measurement technology.

To learn more about the MRF, please visit www.grimrf.org.

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