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API MPMS 5.3:2005 pdf download

API MPMS 5.3:2005 pdf download.Manual of Petroleum Measurement Standards Chapter 5—Metering
Section 3—Measurement of Liquid Hydrocarbons by Turbine Meters. TEMPERATURE CHANGES
In addition to atTecting changes in viscosity, significant variations in the temperature of the liquid can also aulect meter performance by causing changes in the physical dimensions of the meter. For greatest accuracy, the meter should be proved in the range of normal operating conditions.
A calculated temperature correction based on the volume weighted average temperature of the delivery. may be used to correct indicated volume to a volume at a base or reference temperature. CHANGES
A change in the density of the metered liquid can result insignificant differences in meter factor, thereby requiring themeter to be proved. For liquids with a relative density ofapproximately 0.7 or less,consideration must be given toraising the value of the meter’s minimum flow rate to main-tain linearity.The driving torque of the flowing stream on therotor is proportional to the liquid density multiplied by thesquare of the liquid velocity.
The driving torque at the minimum flow rate can be main-tained by increasing the minimum flow rate for low densityliquids. The amount of increase in minimum flow rate willvary depending on meter size and type, and the magnitude ofthe change in fluid density.To establish the minimum flowrate, several provings should be made at different rates until a meter factor that yields an acceptable linearity and repeatabil-ity can be determined.
To maintain meter rangeability the maximum flow rate canalso be increased, up to the limit allowed by the meter manu-facturer. PRESSURE CHANGES
If the pressure of the liquid when it is metered varies fromthe pressure that existed during proving, the relative volumeof the liquid will change as a result of its compressibility.(The physical dimensions of the meter will also change as aresult of the expansion or contraction of its housing underpressure.) The potential for error increases in proportion tothe difference between the proving and opcrating conditions.For greatest accuracy, the meter should be proved at the oper-ating conditions (sce API MPMS Chapters 4 and 12).
Volumetric corrections for the pressure effects on liquidswith vapor pressures above atmospheric pressure are refer-enced to the equilibrium vapor pressure of the liquid at thestandard temperature,60°F,15℃,or 20°C,rather than toatmospheric pressure,which is the typical reference for liq-uids with measurement temperature vapor pressures below atmospheric pressure.Both the volume of the liquid in theprover and the registered metered volume are corrected fromthe measurement pressure to the equivalent volumes at theequilibrium vapor pressure at the standard temperature, 60°F,15°C,or 20°C.This is a two-step calculation that involvescorrecting both measurement volumes to the equivalent vol-umes at equilibrium vapor pressure at measurement tempera-ture.The volumes are then corrected to the equivalentvolumes at the equilibrium vapor pressure at the standardtemperature,60°F,15°C,or 20°C. A detailed discussion ofthis calculation is included in API MPMS Chapter 12.2. DEPOSITs OR DEBRIS
Deposits or debris on the turbine meter rotor will decreasethe flow area, thereby increasing the liquid velocity, throughthe rotor.This will increase the rotor velocity, and thus themeter k-factor,for a given flow rate. The effect is less fortwo-bladed helical turbine meters,but may still be substan-tial,depending on the coating thickness and the size of themeter. Deposits or debris on other internal components of theturbine meter, or on the flow conditioning element, may alsohave a significant effect on meter performance.


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