Goals and Topics of the Orifice Flow Meter Research Study:

The orifice flow meter research program is not currently active in the 2002 Gas Technology Institute (GTI) research.

The orifice meter research program began in 1989 at the Metering Research Facility (MRF) with the objective of solving installation effects issues and operational issues (adverse effects of abnormal operating conditions), such as:

• Bent or backwards-facing orifice plates

• Contaminated or dirty orifice plates

• Roughened meter tubes

Currently, the MRF orifice flow meter research program is focused on creating a report highlighting nonstandard operational effects and their importance for metering accuracy. The operational effects report informs orifice meter users of many causes of orifice flow measurement errors not discussed in the standards and how they affect measurement accuracy and custody transfer. This report was released in May 2002.

Based on the orifice meter tests at the MRF and past research, a topical report to GTI was released in early 2002, which discusses:

• Present orifice flow meter standards

• Related research on roughness effects

• High-pressure differentials

• Low-pressure differentials

• Errors associated with pulsation effects

• Errors associated with meter characteristic effects

Benefit of the Orifice Flow Meter Research to Industry:

	Inside surface of artificially roughened meter tube on an orifice meter run

Orifice meters comprise a significant portion of the natural gas flow meters currently used in the United States. For many years, these meters have been in use and have been widely studied and characterized by correlations such as the Reader-Harris/Gallagher equation. The correlations and standards now in use assume ideal or stated ranges of operating conditions, such as:

• Clean meter tubes

• Known surface roughnesses

• Sharp edges on orifice plates

• Differential pressures within operating ranges of the transmitter equipment

Biases and errors occur when orifice meters in the field are operated outside the ideal or standard conditions.

Because the natural gas industry relies heavily on orifice meters throughout the country, the costs associated with biases and errors stemming from nonstandard operating conditions can be significant. Approximately 20 to 70 trillion cubic feet of natural gas are measured each year in the United States. Even if the gas volume unaccounted for because of measurement uncertainty and bias was as little as 0.01%, the cost to the industry is $6 to 21 million per year assuming the average value of the gas is approximately $3 per 1,000 cubic feet.

While some operational and installation errors can cause obvious measurement biases (as much as 20%) that are immediately discovered and resolved, other errors can cause much smaller, less obvious biases that can be more costly in the long run. Identifying these causes of bias and quantifying their effects has the potential to reduce costs associated with custody transfer disputes, balancing of accounts, and prior period adjustments.

Primary Investigator:  Darin L. George, Ph.D., MRF Senior Research Engineer

To find out how the Metering Research Facility can assist you with flow measurement, meter development, calibration, testing, and training, or how you can contract with SwRI, please contact Terry Grimley at tgrimley@swri.org or (210) 522-2353.