Flow Measurement; Flow Time - Emerson FloBoss 103 Instruction Manual

FloBoss 103/104 Instruction Manual
1.3.1

Flow Measurement

The primary function of the FB100-Series is to measure the flow of
natural gas through an orifice or turbine or rotary meter in accordance
with the 1992 American Petroleum Institute (API) and American Gas
Association (AGA) standards.
The primary inputs used for AGA3 flow measurement function are
differential pressure, static pressure, and temperature. The differential
and static pressure inputs, which are sampled once per second, come
from the Dual-Variable Sensor. The temperature input, which is
sampled and linearized once per second, comes from an RTD probe.
The primary inputs used for AGA7 flow measurement are Pulse Input
(PI) counts, static pressure, and temperature. The Pulse Input counts are
acquired from a rotary meter (pulse interface module) or turbine meter
(PI on termination board), the static pressure (including auxiliary
pressure) inputs come from the pressure transducers, and the
temperature input is read from an RTD probe.
Flow Calculations for
The flow calculation is in accordance with ANSI/API 2530-92 (AGA
Orifice Metering
Report No. 3 1992), API Chapter 14.2 (AGA Report No. 8 1992 2nd
printing 1994), and API Chapter 21.1. The flow calculation may be
configured for either metric or English units.
Flow Timer The differential pressure stored for each second is compared to the
configured low flow cutoff. If the differential pressure is less than or
equal to the low flow cutoff or the converted static pressure is less than
or equal to zero, flow is considered to be zero for that second.
Flow time for a recalculation period is defined to be the number of
seconds for which the differential pressure exceeded the low flow
cutoff.
Input and Extension
Each second the FB100-Series stores the measured input for differential
Calculation
pressure, static pressure, and temperature and calculates the Integral
Value (IV). IV is the square root of the absolute upstream static pressure
multiplied by the differential pressure.
The FB100-Series calculates flow time averages of the inputs and the IV
over the configured calculation period, unless there is no flow for an
entire calculation period. Linear averages of the inputs are recorded to
allow monitoring during no flow periods.
Instantaneous Rate
The instantaneous value of the Integral Value (IV) is used with the
previous calculation period's Integral Multiplier Value (IMV) to
Calculations
compute the instantaneous flow rate.
The IMV is defined as the value resulting from the calculation of all
other factors of the flow rate equation not included in the IV. The
instantaneous flow rate is used with the volumetric heating value to
compute the instantaneous energy rate.
Flow and Energy
The averages of the differential and static pressure, temperature, and
sum of the IV are used with the flow time to compute the flow and
Revised August-2017 General Information 1-11