ASME MFC-22:2007 pdf download Measurement of Liquid by Turbine Flowmeters
rangeability or turndocwn: flowmeter rangeability is theratio of the maximum to minimum flow rates orReynolds number in the range over which the metermeets a specified uncertainty and / or accuracy.
repeatability of measurements (qualitatioe): the closeness ofagreement among a series of results obtained with thesame method on identical test material, under the sameconditions (i.e., same operator, same apparatus,samelaboratory, and short intervals of time).
reproducibility: the closeness of agreement betweenresults obtained when the conditions of measurementdiffer; for example, with respect to different test appara-tus, operators, facilities, time intervals, etc.
Reynolds nunber: a dimensionless parameter expressingthe ratio between inertia and viscous forces.
turbine meter: a flow measuring device with a rotor thatresponds to the velocity of flowing fluid in closed con-duit. The flowing fluid causes the rotor to move with atangential velocity that is directly linearly proportionalto the volumetric flow rate.
3.2 Symbols
See Table 1.
4PRINCIPLE OF MEASUREMENT4.1 Measuring Mechanism
The measuring mechanism consists of the rotor, rotorshafting, bearings, and the necessary supporting struc-ture (Figs. 2 and 3). The flowing fluid passing throughthe blades of the rotor,which are at an angle to thedirection of the flow, imparts a tangential force on theblades. This tangential force causes the rotation of therotor that is directly linearly proportional to the axial
flow rate through the meter. For ideal fluids and friction-less rotor, the rate of rotation is linearly proportional tothe axial flow velocity and the constant of proportional-ity is a function of the blade angle.
4.2 Output and Readout Device
4.2.1 The rate of revolution of the rotor is normallydetermined from the blade passing frequency or by othermeans that relates to the rate of rotation.
4.2.2Turbine meter output may be mechanical,electrical, electromechanical, optical, analog, and digital.The readout devices may be of any form suitable for theapplication.
4.2.3 For electrical pulse output meters, the outputincludes the pulse detector system and all electrical con-nections necessary to transmit the indicated rotor revo-lutions outside the body for uncorrected volumeregistration.
5 SELECTION OF METER AND ACCESSORY
EQUIPMENT FOR FLOW RATE DETERMINATIONFor proper selection and operation of the meter, thefollowing information may be necessary:
(a) fluid properties of the flowing stream includingviscosity, vapor pressure, toxicity, corrosiveness,lubrica-tion properties,specific gravity, etc.
(b) flow rate range and operational conditions includ-ing unidirectional or bidirectional flows and continuousor intermittent flows
(c) performance characteristics that are required forthe application including linearity over a specified flowrange, repeatability at any flow rate, and improved lin-earity over a flow range
dj the flange rating, area classification, materials, anddimensions of the equipment used
(e) available space for the meter installation and prov-ing facility, if required for the application
f)operating pressure ranges, acceptable pressurelosses through the meter installation, and necessary con-sideration to avoid vaporization of the fluid while pass-ing through the meter
(g) operating temperature range and the applicabilityof the automatic temperature compensation
h)effects of corrosive fluids and contaminants on themeter
(i) amount and size of the suspended solids in theflowing stream including filtering equipment for themetering section
(jtypes of readout and printout devices, or desiredoutput system to be used for signal preamplificationand output units of the measurement as required(k) for multiple meter-run installations and how ameter is taken in or out of service during operation of the entire system
ASME MFC-22:2007 pdf download
