Page 57 - Instrumentation Reference Book 3E

42 Measurement of flow
duations of the burette it is possible to determine BS 5781, Specification for Measurement & Calibration
flow rate. A typical calibration system is illu- Systems (1979)
strated in Figure 1.60. BS 5192, Specification for Electromagnetic Flowmeters
(1980)
BS 6199, Measurement of Liquid Flow in Closed Con-
Water-displacement method In this method a duits Using Weighting and Volumetric Methods
(1981)
cylinder closed at one end is inverted over a water Cheremisinoff, N. P., Applied Fluid Flow Measurement,
bath as shown in Figure 1.61. As the cylinder is Dekker (1979)
lowered into the bath a trapped volume of gas is Durrani, T. S. and C. A. Created, Laser Systems in Flow
developed. This gas can escape via a pipe con- Measurement, Plenum (1977)
nected to the cylinder out through the flowmeter Haywood, A. T. J., Flowmeter-A Basic Guide and
being calibrated. The time of the fall of the cylin- Sourcebook for Users, Macmillan (1979)
der combined with the knowledge of the volume/ Henderson, F. M., Open Channel Flow, Macmillan
length relationship leads to a determination of the (1966)
amount of gas displaced which can be compared Holland, F. A,, Fluid Flow for Chemical Engineers,
Arnold (1973)
with that measured by the flowmeter under cali- International Organization for Standardization, IS0
bration. 3354. (1975) Measurement of Clean Water Flow in
Closed Conduits (Velocity Area Method Using Cur-
rent Meters)
Gravimetric method Here gas is diverted via the Linford, A., Flow Measurement and Meters, E. & F.N.
meter under test into a gas-collecting vessel over a Spon
measured period of time. By weighing the collect- Miller, R. W., Flow Measurement Engineering Hand-
ing vessel before diversion and again after diver- book, McGraw-Hill(l982)
sion the difference will be due to the enclosed gas, Shercliff, J. A,, The Theory of Electromagnetic Flow
Measurement, Cambridge University Press (1 962)
and flow can be determined. This flow can then Watrasiewisy, B. M. and M. J. Rudd, Laser Doppler
be compared with that measured by the flow- Measurements, Butterworth (1975)
meter.
It should be noted that the cost of developing
laboratory flow calibration systems as outlined
can be quite prohibitive and it may be somewhat 1.8 Further reading
more cost-effective to have systems calibrated by
the various national standards laboratories (such Akers, P. etal., Weirs and Flumes for Flow Measure-
ment, Wiley (1978)
as NEL and SIRA) or by manufacturers, rather Baker, R. C., Introductory aide to Flow Measurement,
than committing capital to what may be an infre- Mechanical Engineering Publications (1989)
quently used system. Fowles, G., Flow, Level and Pressure Measurement
in the Water Industry, Butterworth-Heinemann
(1993)
1.7 References Furness, R. A,, Fluid Flow Measurement, Longman
(1989)
Spitzer, D., Flow Measurement, Instrument Society of
BS 1042, Methods for the Measurement of Fluid Flow in America (1991)
Pipes, Part I Orijke Plates, Nozzles & Venturi Tubes, Spitzer, D., Industrial Flow Measurement, Instrument
Part 2a Pitot Tubes (1964) Society of America (1 990)
BS 3680, Methods of Measurement of Liquid Flow in
Open Channels (1969-1983)