Turbine meters measure natural gas flow by counting the revolutions of a rotor within the meter. The document discusses turbine meter operating conditions, performance requirements, calibration, installation specifications, and environmental considerations. Turbine meters should be installed and calibrated according to manufacturer specifications to ensure accurate measurement of natural gas flow.

1. AGA REPORT NO.7
MEASUREMENT OF NATURAL GAS BY
TURBINE METERS.
NJOKU, WILLIAM.
CHIBUZOR,
ITEC/SCAAP TRAINEE
1ST AUGUST – 31ST
OCTOBER,2014

2. TABLE OF CONTENTS
 CHAPTERS PAGE
1.INTRODUCTION……………….…………………
… 3-6
2.OPERATION CONDITION…..……………………
7-13
3.PERFORMANCE REQUIREMENTS.………….
14-17
4.TURBINE METER CALIBRATION..…………….
18-19
5.TURBINE METER INSTALLATION
SPECIFICATIONS…………………………………
.. 20-29
6.ENVIRONMENTAL CONSIDERATIONS……..

3. 1. INTRODUCTION
SCOPE
 Turbine meter is an axial flow meter which
can be used for measurement of natural gas.
About 2inch/50.8mm and larger bore
diameter in which the entire gas stream flows
through the meter rotor relative to its
rotational speed.
 It could be used to measure a broad range of
fluid other than natural gas .e.g. Well
effluents/crude oil on the well head.

4. PRINCIPLE OF MEASUREMENT OF TURBINE
METERS
 Turbine meters are inferential meters that measures flow
by counting the revolutions of a rotor, with blades, which
turns in proportion to the gas flow velocity.
 From the geometry and dimensions of the rotor blades
and flow channel, for a particular turbine meter size and
model, the gas volume at line conditions can be inferred
from counting the number of rotor revolutions.
 The revolutions are transferred into digital readout or
electronic signals by some combination of mechanical
gearing, generated electronic or optical pulses, or
frequency. The accumulated line volume can be
converted to base volume at standard or contract
conditions by accessory devices.

5. PRINCIPLE OF MEASUREMENT OF TURBINE
METERS
 Turbine can operate over a wide range of gas and ambient conditions.
 The upper flow capacities are established and limited by maximum local
internal gas velocities, noise generation, erosion, rotor speed, shaft
bearing wear and pressure losses.
 The maximum flow capacity at line conditions is fixed for a particular
turbine meter regardless of the operating pressure and temperature.
 The maximum base flow capacity increases in accordance with Boyle’s
laws and charles’ law ie Pα1/V(mass and temperature constant) and
VαT(Pressure constant) respectively. Minimum flow capacities are
limited by fluid and non fluid drag (i.e., wind age and mechanical friction
losses, respectively) that cause a particular turbine meter design to
exceed the desired or prescribed performance limits.
 Turbine meter is calibrated base on the k-factor :Pulse/unit volume or
liter.

6. PRINCIPLE OF MEASUREMENT OF TURBINE
METERS

7. 2. OPERATING CONDITIONS
GAS QUALITY
 The meter should operate with any of the
normal range natural gas composition
mixture, reference to table 1 of AGA Report
No.8, Compressibility factors of natural gas
and other related hydrocarbon gases. See
table below:

8. RANGES OF GAS MIXTURE CHARACTERISTICS
CONSISTENT WITH THIS REPORT
QUALITY NORMAL RANGE EXPANDED
RANGE
Relative density* .554 to .87 0.07 to 1.52
Gross heating
value**
447 to 1150
Btu/Scf
0 to 1800 Btu/Scf
Gross heating
value***
18.7 to 45.1mj/m3 0 to 66mj/m3
Mole percent
Methane
45.0 to 100.0 0 to 100.0
Mole percent
Nitrogen
0 to 50.0 0 to 100.00
Mole percent
carbon dioxide
0 to 30.00 0 to 100.00
Mole percent
ethane
0 to 10.0 0 to 100.00
Mole percent 0 to 4.0 0 to 12.0

9. RANGES OF GAS MIXTURE CHARACTERISTICS
CONSISTENT WITH THIS REPORT
*Reference Condition: Relative density at
60OF/15.556OC, 14.73 Pisa.
**Reference Conditions: Combustion at 60OF
, 14.73psia; density 60OF/15.556OC,
14.73psia
***Reference Conditions: Combustion at 25OC,
0.101325mpa; density at 0OC, 0.101325mpa.
# The normal range is considered to be zero
for these compounds.

10. OPERATING PRESSURE
 The operating condition is always with the range
specified by the meter manufacturer.
TEMPERATURES, GAS AND AMBIENT
 The turbine meter should operate within the given
manufacturers flowing gas and ambient temperature
specification.
 Depending on the material of construction, turbine
flow meters can operate over a flowing gas and
ambient range of -40OF to 165OF (-40OC to 74OC).
 It is important the flowing gas temperature remain
above the hydrocarbon dew point of the gas to avoid
positive meter damage and error in measurement.

11. EFFECT OF GAS DENSITY
 The density could have three principle effects on the
meter performance of the gas turbine meter;
 RANGEABILITY : The rangeability of a turbine meter
increases as gas density increases ie Turndown
ratio(Ratio of the maximum to minimum flow rates
base on specified performance requirement)
 PRESSURE DROP: The pressure loss across a
turbine meter increases as the gas density increases.
 ERROR: The operating characteristics may change
as gas density changes.

12. GAS FLOW RATE CONSIDERATIONS
 The manufacturer shall provide the range of flow rate at
various pressures.
CHOICE OF TURBINE BLADE TYPE
 For precision applications, the use of Helical blade
turbines rather than Flat blade turbines is recommended
as the helical blade have;
 Better flow stability
 Lower sensitivity to viscosity variations
 Very good linearity(±0.15% or better)
 Greater operating flexibility owing to the possibility of less
frequent calibration and of using performance table or
curves(k-factor versus flow rate); ISO4124 or
APIMPMS5.3

13. FLAT AND HELICAL BLADE TURBINE METER

14. 3. PERFORMANCE REQUIREMENTS
 GENERAL PERFORMANCE TOLERANCE
Flow limits for Qmin, Qt and Qmax for each meter
design and size are specified by the manufacturer.
Under atmospheric pressure the meter performance
shall be within the following tolerances after
calibration;
 Repeatability........................ ±0.2% from Qt to Qmax
 Maximum peak-to-peak error….. 1.0% above Qt
 Maximum error…………. ±1.0% from Qt to Qmax,
and
±1.5% from Qmin to Qt
 Transition flow rate…… Qt not greater than 0.2

15. IMPORTANT POINTS
 The tolerances apply after adjustment of the change
gears(if any) and/or k-factor setting and final application
of the final meter factor.
 The tolerances apply after any corrections carried out
within meter but prior to the application of any
linearization algorithms by equipment auxiliary to meter.
 These tolerances are applicable at atmospheric pressure.
Turbine meter performance are expected to improve
dramatically relative to the operating gas pressure
increase. The increase in meter performance is with
smaller values for repeatability and maximum peak-to-
peak error, provided the meter is calibrated for the
intended condition.

16. PRESSSURE INFLUENCE
 According to the research on effect of
pressure on turbine meter performance
conducted in 2002 and 2003,to minimize
error, the turbine meter should be calibrated
for the applicable operating conditions.

17. INDIVIDUAL METER TESTS
 The manufacturer shall test the integrity of all
pressure-containing components for every
turbine meter. This test shall be conducted in
compliance with the appropriate industrial
standard, (ANSI/ASME B16.1, B16.34 etc)

18. 4. TURBINE METER CALIBRATION
 For establishment of satisfactory performance
characteristics, every turbine meter should be
calibrated under a condition acceptable and agreed
upon between the parties of the transaction.
 For best performance, the calibration conditions
should correspond to the expected in-service
conditions such as;
Fluid characteristics, operating pressure, expected
flow rates, the use of a dedicated meter body, inlet
and outlet piping characteristics, including other
factors that can affect meter performance.

19. CALIBRATION CONDITION
 Research has shown that the performance of
turbine flow meters varies with changes in flow
rate and operating pressures.
 This significant variations are related to changes
in Reynolds number; Re= U.D.ρ/μ.
 The changes in some cases also relates to
density and are significant at low and
intermediate operating pressure and flow rates.
 Therefore for optimal measurement, attention to
these variations and changes are very
important.

20. 5. TURBINE FLOW METER INSTALLATION SPECIFI
CATIONS
GENERAL CONSIDERATIONS
 FLOW DIRECTION
 Turbine flow meters designed only for one directional
flow, shall be installed as stipulated. Reverse flow
could damage meter internals and may result to
registration of error.
 The manufacturer may be consulted if reverse flow
has ever occurred. In the case for a reverse flow
expected, additional valving is necessary to allow gas
to flow through the meter in the forward direction only,
unless the meter is recommended for bi-directional
flow.

21. METER ORIENTATION AND SUPPORT
 Turbine meter designed for horizontal
installation, shall be installed as stipulated.
 For vertical installation, the manufacturers
recommendations for piping configuration
and maintenance should be followed. The
meter piping should be adequately supported
and installed so as to minimize strain on the
meter body.

22. METER RUN CONNECTION
 Meter and adjacent pipe section should have
same nominal diameter. Meter inlet and
outlet connections and flanges shall be
aligned correctly concentrically and gasket
shall not protrude into the flowing gas to
avoid affecting the flow performance.

23. TEMPERATURE WELL LOCATION
 Temperature well shall be located downstream
of the meter to keep distances to a minimum.
 Temperature well are installed between one and
five nominal pipe diameters from the meter
outlet but upstream from any valve or flow
restrictor. It is important that the temperature
well be installed to ensure that heat transfer
from the adjacent piping and radiation affect
from the sun do not influence the temperature
reading of the flowing gas.

24. PRESSURE TAP LOCATION
 The pressure tap designed by the
manufacturers on the meter shall be used as
the point of pressure sensing for recording or
integrating instruments and during
calibration.

25. FLOW CONDITIONING
 The conditioner is installed at the upstream
of the turbine meter to eliminate the effect of
swirl and or asymmetric flow. Headers,
Pipefitting's, valves and regulators preceding
the inlet may cause disturbed flow conditions
which will be absorbed by the flow
conditioner. There shall be no protrusion into
the pipe between the meter and flow
conditioner to avoid gas flow disturbances.

26. RECOMMENDED INSTALLATION
CONFIGURATIONS
 Turbine meters may be operated according to
the recommended installation configuration with
acceptable results, while more severe piping
arrangements may result in considerable error.
The magnitude of error, if any, will be a function
of the extent of the flow disturbances, the
meter’s design, the quality of external and
internal flow conditioning, and/or the meter’s
ability to adjust to such conditions. More so
other configurations may be used provided they
are shown to be acceptable based on published
experimental data.

27. RECOMMENDED INSTALLATION
CONFIGURATIONS
 The recommended installation, diagram below,
includes at least 10 nominal pipe diameter of
straight pipe upstream of the meter inlet, with a
flow conditioner outlet located 5 nominal pipe
diameters upstream of the meter inlet.
 A minimum length of 5 nominal pipe diameter of
straight pipe is included downstream of the
meter. There shall be no pipe connections within
the upstream or downstream piping other than
pressure taps, temperature wells or flow
conditioning elements.

28. RECOMMENDED INSTALLATION
CONFIGURATIONS

29. RECOMMENDED INSTALLATION
CONFIGURATIONS
NOTES:
[1] Recommended spacing, unless otherwise
supported by published test data for the flow
conditioning element.
[2] No pipe connections or protrusions allowed
within this upstream section.
[3] For recommended size of blow down valve
see table 2, Located downstream of the
meter.

30. 6. ENVIRONMENTAL CONSIDERATIONS
TEMPERATURE
 Turbine meter should be installed and used
within the ambient flowing gas temperature
limits based on manufacturers specifications.
VIBRATION
 Though turbine meters are not susceptible to
vibration. Vibration frequency need to be
avoided as it might excite the natural
frequencies of the piping set, potentially leading
to excessive noise, structural damage to the
pipe and as well reduce bearing service life of
the meter.

31. PULSATION
 Pulsation may occur depending on the design of
the system and the operating condition.
 Equipments like compressors and fast-cycling
regulators connected near the turbine will cause
the meter to over register due to the generated
flow pulsations from those equipments.
 So pulsation dampers installed between the
source of pulsation and the meter helps to
eliminate pulsation induced measurement error.

32. FILTRATION AND STRAINERS
 Filtration is recommended for most meter
applications. The accumulation of deposits due to a
mixture of dirt, mill scale, condensates and or
lubricating oils will detoriate meter performance.
Under such conditions, it is recommended that a
strainer with a basket of 3/32inch maximum hole size
and 40 mesh wire liners be installed upstream of the
meter to trap the major part of this foreign material.
Preferably 10-micron filters could be installed for fine
dust/particle removal to save the bearing life.
 A pressure differential gauge should be installed
across the filter or strainer to indicate pressure drop
increase resulting from build up of foreign materials.

33. THROTHLING
 Throttling devices like closed valves or
regulators are not to be installed at close
proximity as recommended, especially
upstream to the meter.
 Close installation of such a device may result
to an increased uncertainty and/or possibly
reduce bearing life.

34. PRECAUTIONAL MEASURES
 INSTALLATION RESIDUES
 For possible damage prevention,
measurement cartridge or meter should be
removed if any work such as welding,
hydrostatic testing etc., is being carried out
very close to the meter. Inside of the turbine
meter and piping shall be cleaned thoroughly
and inspected for construction debris prior to
replacement.

35. VALVE GREASE
 Grease can possibly flow from pipeline valve into the gas stream
during lubrication, as such could adhere to turbine blades,
thereby affecting meter performance. Such valve type should not
be installed upstream of a turbine meter.
RUN-PRESSURIZATION
 Good practice to provide isolation block valves for meter runs so
that the meter(s) can be maintained and calibrated without
service interruptions. For single meter run stations, a flow by pass
line should also be considered. The isolation valve must be
operated in the proper sequence and slowly to avoid reverse
spinning and/or over speeding the meter during start up which
could damage the stationery rotor.
 If operating pressure are over 200psig, a small pressure-loading
line and valve around a large or fast acting inlet block valve will
allow the meter run to be pressurized slowly to avoid the above
damage.

36. RUN-PRESSURIZATION
 Recommended sizes for pressure loading
lines and valves are the same as those for
blown down valves and the blown down
valves are sized to suit the meter capacity to
avoid creating extreme gas velocity

37. TABLE 2- METER TO BLOWN DOWN VALVES
SIZING
METER RUN VALVE SIZE
MM INCHES MM INCHES
50 2 6 0.25
80 3 13 0.50
100 4 13 0.50
150 6 25 1.0
200 8 25 1,0
300 12 25 1.0

38. 7. VOLUMETRIC AND MASS FLOW
MEASUREMENT
 Turbine meter is a velocity-measuring device.
Rotor revolutions are counted mechanically
or electrically and can be converted to a
continuously totalized volumetric registration
since the flowing volume is at flowing
pressure and temperature conditions, it must
be corrected to the specified base conditions
for account purposes.

39. EMPLOYING GENERAL GAS EQUATION/LAW
 b= base condition,
 f= flowing condition
 r= rated condition.
 (Pf )(Vf)= (Zf)(N)(R)(Tf)………. For flow condition.
 (Pb)(Vb)= (Zb)(N)(R)(Tb)…….. For base condition.
P= Absolute pressure
V= volume
Z= compressibility factor
N= Number of moles of gas
T= Absolute temperature
R= Universal gas constant.

40. EMPLOYING GENERAL GAS EQUATION/LAW
 Since R is an independent gas constant from
pressure, temperature and for the same number of
moles, Therefore the two equation can be combined
to yield:
 Vb = Vf (Pf/Pb)(Tb/Tf)(Zb/Zf)
FLOW RATE AT FLOWING CONDITION :
 Qf = Vf/t………
Qf = Volumetric flow rate at flowing condition
Vf = Volume measured at flowing condition during
a time interval ‘t’.
t = time.

41. FLOW RATE AT BASE CONDITION
 Qb = Qf (Pf/Pb)(Tb/Tf)(Zb/Zf).
EQUATIONS FOR CALCULATING MASS
FLOW.
 Mass flow measurement can be employed to arrive at base
volume (Vb) or base volume flow rate (Qb) through the use
of a densitometer or calculations from compositional
analysis. The mass or mass rate of flow is:
 M= (Vf)(ρf)
M= Total mass through the meter
Vf = Total volume through the meter
ρf= Density of flowing gas.

42. EQUATIONS FOR CALCULATING MASS FLOW
 Where
Qm= Mass rate of flow
Qf= Volume rate of flow(actual or registered)
ρf = Density of flowing gas.
since the mass or mass rate of flow at
flowing conditions equals the mass at base
conditions, it can be stated that:
(Vb) (ρb) = (Vf)(ρf) or
(Vb)=(Vf) ρf/ρb

43. EQUATIONS FOR CALCULATING MASS FLOW
 (Qb)= (Qf) ρf /ρb.
 This equations shows that the base volume
(Vb) or base volume flow rate (Qb) can be
calculated by knowing the density of the
fluid at both flowing and base conditions
without the need to measure the flowing
pressure (Pf) or the flowing Temperature
(Tf) and calculating the compressibility
multiplier.

44. YOU
THANK