Measuring Natural Gas via a Turbine Meter
Best Practices
The QRATE Scanner 3300 calculates gas flow through outputs from a MVT connected to a turbine meter (or directly
from the output from the turbine meter) in accordance with AGA 7 and API MPMS Chapter 21.1 industry standards. For
optimum performance, ensure that the turbine and MVT installation complies with the industry recommendations listed
below:
•
Install the turbine flowmeter in the meter run such that there are 10 nominal diameters of straight pipe upstream
and 5 nominal diameters of straight pipe downstream of the meter. Both inlet and outlet pipe should be of the same
nominal size as the meter.
•
Straightening vanes are recommended for eliminating swirl conditions. If used, they should be installed 5 diameters
of straight pipe upstream of the meter.
•
Where an RTD is used to facilitate compensated gas measurement from a gas turbine meter, locate the RTD within 5
diameters of straight pipe downstream of the meter outlet and upstream of any valve or flow restriction.
Installation Procedure—Direct Mount to a Turbine Meter
A MVT can be mounted directly to a gas turbine meter for measuring natural gas. A pipe adapter and union are attached
to the MVT, allowing a direct connection to the turbine meter.
An external pressure transducer is required for converting the pressure to a 4-20 mA or 1-5 V signal, and the MVT must
be equipped with the analog input necessary to receive the pressure signal from the transducer.
Flow
Adapter/union
(CSA-approved)
RTD assembly
10 pipe diameters
upstream (minimum)
5 pipe diameters
downstream (minimum)
External pressure transducer
(connected to meter
pressure port)
3/4” conduit
connection (for input/output and
communications)
Figure 2.13 - Direct-mount installation for use with a gas turbine meter
To connect the MVT to a turbine meter using this method, perform the following steps:
1. Position the MVT above the gas turbine flowmeter.
2. Plug the MVT cable connector into the magnetic pickup of the turbine meter and hand-tighten the knurled nut on the
connector.
3. Screw the MVT onto the flowmeter threads surrounding the magnetic pickup with the display facing the desired
direction.
CAUTION Do not use Teflon tape on the threads of the union, adapter, or pipe plugs. Use of
Teflon tape will void the explosion-proof rating of the instrument.
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Section 2
QRATE Scanner 3300 integrated control flow computer
