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Reference, Installation, and Operations Manual Section 2: Product overview
3-9000-743 Rev S June 2013
Description 9
21
Section 2: Product overview
2.1 Description
The Daniel Ultrasonic Gas Flow Meter measures the flow of gas, especially natural gas, by
measuring the difference in signal transit time with and against the gas flow across one or more
measurement path(s). A signal transmitted in the flow direction travels faster than one
transmitted against the flow direction. Each measurement path is defined by a transducer pair
in which each transducer alternately acts as transmitter and receiver. The meter uses the transit
time measurements and transducer location information to calculate the mean gas velocity.
The Daniel Ultrasonic Gas Flow Meter offers bi-directional measurement capability (due to
meter symmetry) over a wide range of flow rates with no pressure loss. Accuracy, safety,
reliability, and ease-of-use are some of the many benefits of Daniel Ultrasonic Gas Flow Meters.
Computer simulations of various gas velocity profiles demonstrate that four measurement
paths provide an optimum solution for measuring asymmetric flow. The Daniel SeniorSonic
TM
Meter (Models 3400 and 3422) utilizes four cross-bore, parallel-plane measurement paths to
offer a high degree of accuracy, repeatability, and superior low-flow capabilities without the
compromises associated with conventional technologies. These features make the
SeniorSonic
TM
Meter the best choice for custody transfer applications.
Daniel offers two JuniorSonic
TM
Meter models (3410 and 3420) for applications that are
cost-sensitive and/or do not require custody-transfer levels of accuracy. Model 3410 utilizes one
measurement path; Model 3420 utilizes two measurement paths. Unlike the SeniorSonic
TM
Meter designs, the JuniorSonic
TM
design bounces the ultrasonic signal across the meter body.
Each transducer is angled 60° from horizontal (60
o
included angle). The path is often referred to
as a bounce-path (as the signal is bounced off the meter body) or a centerline path (as it goes
through the center-line of the meter body). The 3420 model’s two paths are configured at right
angles to one another in a “bulls-eye” arrangement. The bounce-path method simplifies
construction of the meter and makes the meter less susceptible to interference from pipeline
liquids.
Since the JuniorSonic
TM
Gas Flow Meter utilizes center-line paths, an additional piece of
information is needed to determine the average velocity of the moving gas (remember that not
all gas is moving at the same velocity). A “flow profile correction factor”, sometimes called the
Reynold's Number correction factor, is needed to correct the velocity measured along the
path(s) to the correct average for the cross sectional area. (see Section 5.6.11 and
Equation 6-18 for Reynolds correction information). This can be accomplished by either using a
fixed value or more accurately by measuring pressure and temperature, and then applying an
active correction to the measured transit times.
The dual-path configuration (3420 model) provides a more representative measurement of the
entire flow profile than the single-path configuration (3410 model).
The Daniel Ultrasonic Flow Gas Meter’s U.L. safety listing is accomplished through a
combination of an explosion-proof electronics enclosure, and intrinsically safe transducers. The
transducers and transducer leads are designed for maximum safety in a Class 1, Division 1 area
without need of further protection when installed in accordance with the field wiring diagram
(Daniel P/N DE-21056, see Appendix I).