Sensia 3300 EFM, Installation, Operation & Maintenance Manual

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Measuring Natural Gas via a Differential Pressure Meter
Best Practices
The Scanner 3300 calculates gas flow through outputs from a MVT connected to a differential pressure meter. For best
measurement accuracy, ensure that the meter run complies with the following AGA 3 and ISO 5167 guidelines, as appli-
cable:
• Do not place unit near vents or bleed holes that discharge corrosive vapors or gases.
• Consider the orientation of the meter run when determining the best position for mounting the MVT.
– If the MVT is mounted to a horizontal pipeline, make sure process connections are at the top of the line, and
mount the MVT above the pressure connections at the pipe.
– If the MVT is mounted to a vertical pipeline, install the sensor above the differential pressure source
connections, or install a condensate (drip) pot to prevent the accumulation of liquid in interconnecting tubes.
Slope all tubing upward at least 1 in./LF to avoid liquid entrapment.
• Mount the MVT as near level and as free from vibration as possible.
• Ensure the high port of the sensor (marked H) is connected to the upstream side of the meter run.
• Flow should remain subsonic throughout the measuring section and should be single phase.
• Pipe diameters (D) should be between 2 in. (50 mm) and 39 in. (1,000 mm) per ISO 5167; or greater than 2 in. (50
mm) per AGA 3.
• Pipe Reynolds numbers must be above 5,000.
• d (orifice diameter) must be greater than or equal to 0.45 in. (11.5 mm).
• β (diameter ratio) must be greater than or equal to 0.1 and less than or equal to 0.75.
• Gauge lines should be of uniform internal diameter and constructed of material compatible with the fluid being
measured. For most applications, the bore should be no smaller than 1/4 in. (6 mm) and preferably, 3/8 in. (10
mm) in diameter. The internal diameter should not exceed 1 in. (25 mm). If high-temperature fluids are likely to be
encountered, make sure the measuring tube used is rated for the anticipated temperature range.
• Gauge line length should be minimized to help prevent pulsation-induced errors.
• Gauge lines should slope downward to the meter at a minimum of 1 in. per foot.
• If gauge lines must slope in more than one direction, do not allow more than one bend and install a liquid or gas
trap, as applicable. A liquid trap should be installed at the lowest point in a gas service installation.
• Gauge lines should be supported to prevent sag and vibration.
• Where pulsation is anticipated, full-port manifold valves with a nominal internal diameter consistent with the gauge
lines are recommended.
If the MVT is mounted to a cone meter, consider the following best practices as well:
• Position the cone meter so that there are 0 to 5 diameters of straight pipe upstream of the meter and 0 to 3 diameters
of straight pipe downstream of the meter.
• Install the meter so that the static pressure tap is upstream of the differential pressure tap. The high side of the
integral MVT must also be situated upstream.
• Install shutoff valves directly on the pressure taps. Choose a shutoff valve that is rated for the ambient temperatures of
the location and the operating pressure of the pipe in which it will be installed, and suitable for use with dangerous or
corrosive fluids or gases, if applicable. The valves must not affect the transmission of the differential pressure signal.
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Section 2 Scanner 3300 EFM