ASTM D4409-95(1999)
(Test Method)Standard Test Method for Velocity Measurements of Water in Open Channels with Rotating Element Current Meters
Standard Test Method for Velocity Measurements of Water in Open Channels with Rotating Element Current Meters
SCOPE
1.1 This test method describes the design and use of cup-type or vane-type vertical axis current meters and propeller-type horizontal axis current meters for measuring water velocities in open channels.
1.2 This test method is intended primarily for those meters customarily used in open-channel hydraulic (as distinguished from oceanographic) applications with an operator in attendance.
1.3 This test method is intended primarily for current meters that measure one component or filament of flow.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D 4409–95 (Reapproved 1999)
Standard Test Method for
Velocity Measurements of Water in Open Channels with
Rotating Element Current Meters
This standard is issued under the fixed designation D 4409; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (ε) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This test method describes the design and use of 3.1 Definitions: For definitions of other terms used in this
cup-type or vane-type vertical axis current meters and test method, refer to Terminology D 1129.
propeller-type horizontal axis current meters for measuring 3.2 Definitions of Terms Specific to This Standard:
water velocities in open channels. 3.2.1 current meter—an instrument used to measure the
1.2 This test method is intended primarily for those meters speed or velocity of flowing water at a point.
customarily used in open-channel hydraulic (as distinguished 3.2.2 Price-type current meters—generic name for specific
from oceanographic) applications with an operator in atten- vertical axis meters with a rotating element consisting of six
dance. conical cups and constructed as described in Refs (1-3).
1.3 Thistestmethodisintendedprimarilyforcurrentmeters 3.2.3 spin test— a test performed to check the bearings of a
that measure one component or filament of flow. current meter. This test is used primarily with vertical axis
1.4 This standard does not purport to address all of the current meters.
safety concerns, if any, associated with its use. It is the 3.2.4 turbulence—irregular condition of flow in which the
responsibility of the user of this standard to establish appro- velocity exhibits a random variation with time and space
priate safety and health practices and determine the applica- coordinates so that statistically distinct average values can be
bility of regulatory limitations prior to use. discerned.
2. Referenced Documents 4. Summary of Test Method
2.1 ASTM Standards: 4.1 The angular velocity of the rotating element is a
D 1129 Terminology Relating to Water function of water speed at the point of immersion.This angular
D 2777 Practice for Determination of Precision and Bias of velocity is determined from the meter output and its functional
Applicable Methods of Committee D-19 on Water relation to the water speed is determined by calibration.
D 3858 Test Method for Open-Channel Flow Measurement
5. Significance and Use
of Water by Velocity-Area Method
5.1 This test method describes the design and use of various
2.2 ISO Standards:
types of current meters. These current meters are commonly
ISO 2537 Liquid Flow Measurement in Open Channels—
usedtomeasurethevelocityatapointinanopenchannelcross
Rotating Element Current Meters
section as part of a velocity-area traverse to determine the
ISO 3454 Liquid Flow Measurement in Open Channels—
flowrate of water. To this end it should be used in conjunction
Direct Depth Sounding and Suspension Equipment
with Test Method D 3858.
ISO 3455 Liquid Flow Measurement in Open Channels—
Calibration of Rotating-Element Current Meters in
6. Interferences
Straight Open Tanks
6.1 As with any intrusive flow measuring device, rotating
element current meters are subject to damage by debris,
especially in high velocity flows, and to fouling by floating
This test method is under the jurisdiction ofASTM Committee D-19 on Water
materials such as aquatic growths and sewage.
and is the direct responsibility of Subcommittee D19.07 on Sediments, Geomor-
6.2 Owing to bearing friction, each rotating element current
phology, and Open-Channel Flow.
Current edition approved Dec. 10, 1995. Published February 1996. Originally
meter has a limiting low velocity below which it does not
published as D 4409 – 84. Last previous edition D 4409 – 91.
Annual Book of ASTM Standards, Vol 11.01.
3 4
Published by International Standards Organization and available from Ameri- The boldface numbers refer to the list of references at the end of this test
can National Standards Institute, 11 W. 42nd St., 13th floor, New York, NY 10036. method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 4409
function reliably. This velocity is different for each type of 7.1.3.3 Iftherevolutioncountistobemademanuallybythe
meter but, in general, % errors tend to become large as the operator, the audible or visual signals (as distinguished from
velocities decrease below 0.1 to 0.2 ft/s (0.03 to 0.06 m/s). recorded signals) shall not occur at a frequency greater than 3,
and preferably 2.75, cps.
7. Apparatus 7.1.3.4 A timing device is a necessary adjunct to the meter
so that the revolution rate can be determined from the
7.1 Current Meters— Rotating element current meters con-
revolution count. In the simplest configuration this system can
sist of a rotating element with shaft and bearings, a mechanism
consist of a manual stopwatch for timing audible or visual
for detecting and registering revolutions, and a frame which
signals.
supportstheforegoingelementsandprovidesforsuspensionof
7.1.3.5 If the current meter system has a direct readout in
themeterandtheinsertionofstabilizingfinsifneeded.Current
velocity units, the user must be furnished an accuracy state-
meters covered by this test method do not customarily incor-
ment which includes the readout. Also, the user must be
porate direction-measuring devices.
provided with a procedure to check for system malfunctions.
7.1.1 Rotor Configuration—Horizontal-axis meters have
7.1.4 Frame—The frame houses the current-meter elements
propeller-type rotors comprised of two or more blades. Inter-
and provides for suspending the meter in the flow. Depending
changeable elements of different pitch or diameter can be used
upon the intended use of the meter, the frame can be designed
to cover a wider range of velocities. Vertical-axis meters have
for suspension by rigid rod only, by cable-and-weight only, or
a rotating wheel made up of several cup-type or vane-type
it can provide for both types of suspension.
elements. Rotors employing six conical cups (for example,
7.1.4.1 The connection for rod mounting shall provide, in
Price-type meters) are frequently used but other configurations
conjunction with the rod, rigidity and vibration-free perfor-
are permissible provided the following requirements are met:
mance at the highest velocity claimed for the meter, and shall
7.1.1.1 The relation between velocity and rotation rate must
provide for adjustable meter position along the rod. Fixed rod
be stable, that is, there should be no significant uncertainties in
position is necessary for some applications, such as for
the meter’s rating curve due to unstable flow separations at the
measuring through ice cover. Rods must be provided with
cups or similar hydrodynamic causes.
suitable fixtures to accommodate fins as specified in 7.1.4.3.
7.1.1.2 If fractions of revolutions are to be registered, the
7.1.4.2 The connection for cable suspension shall permit the
angular movement of the rotor must be the same during each
meter to swivel in a vertical plane so that it can seek and
measured fraction.
maintain a horizontal orientation.
7.1.2 Bearings:
7.1.4.3 Fins—Meters to be suspended by cable must pro-
7.1.2.1 Bearing design shall permit the meter to be used in
vide for stabilizing fins to be inserted into the frame. Provision
sediment-laden water, without affecting the accuracy of the
shall be made for balancing the meter-fin unit about its pivot
meter.
while immersed in water, so that it can operate in a level
7.1.2.2 If a particular oil is required for bearing lubrication,
position at all velocities claimed for the meter.
thesuppliershallfurnishitwiththeinstrument.Informationfor
7.1.5 Other General Requirements:
obtaining replacement oil shall also be furnished.
7.1.5.1 The meter design and construction shall be suffi-
7.1.2.3 At the highest velocity claimed for the meter,
ciently sturdy for normal field use and the materials shall be
properly maintained bearings shall function without adversely
usable in normally encountered fresh and saline waters without
affecting meter performance for a period of time customarily
undue corrosion or wear.
associated with normal use or for the period of time between
7.1.5.2 The meter shall offer low resistance to the flow and
recommended recalibrations. If bearing replacement is needed
must be able to maintain a stable position with respect to the
to meet this requirement, such replacement shall be possible in
flow.
the field.
7.1.5.3 Meter parts shall be interchangeable among other
7.1.2.4 At the lowest velocity claimed for the meter, prop-
erly maintained bearings shall function consistently and not meters of the same model and manufacturer. The manufacturer
contribute to undue deviations in meter response. shall state which parts can be replaced without requiring
7.1.2.5 No breaking-in period for the bearings shall be recalibration.
required after meter delivery. 7.1.5.4 Design features which permit minor repairs or parts
replacement by the user in the field are encouraged. Any
7.1.3 Registering Revolutions—The current meter shall be
equipped with a mechanism which detects and signals either special purpose tools needed for such repairs or replacement
shall be furnished with the meter.
single revolutions of the rotor or known fractions or multiples
thereof. This detection can be by mechanical-electric contact,
7.1.5.5 For high-inertia, vertical-axis meters, spin test dura-
by magnetic, optical, or other methods, and shall produce a tions shall be recommended for effective use of the meters at
signal which is audible, visible, or recordable by other means. their lowest claimed velocity. See Refs (1-3) for Price-type
7.1.3.1 Amechanical-electriccontactdeviceshallnotaddin meters. Users shall be provided with alternative procedures for
qualitative indications of internal friction in meters that are not
any significant manner to the internal friction at the lowest
velocity claimed for the meter. amenable to spin testing.
7.1.3.2 The contact device must always actuate the signal at 7.1.5.6 The user shall be provided with the means (detailed
precisely the same position in each revolution (fraction or dimensions, templates, or forms) to ascertain gradual changes
multiple). in rotor configuration, where appropriate. See also 10.2.
D 4409
7.1.5.7 Information on depth (pressure) limitation on meter information on this capability for the usable range of approach
submergence and on temperature effects, if any, on meter angles claimed for the meter.
performance shall be furnished by the manufacturer. 9.1.4 Recalibrate meters when their performance is suspect.
7.2 Suspension Equipment—Description and requirements Some organizations establish routine recalibration policies,
for suspension equipment are available in Refs (2, 3) and ISO such as annually or based on hours of use. In the case of
3454. This test method includes only those elements which instruments made to stringent specifications, repairs and parts
directly affect the meter performance. replacement may be made without recalibration requirements.
7.2.1 Rods—The rod for which the meter rating is valid, if 9.2 Towing Tank Calibration—Current meters usually are
calibrated (rated) in a towing tank. Guidelines for this type of
not furnished with the meter, shall be precisely specified with
regard to dimensions and configuration. calibration are given in ISO 3455.
9.3 Water Tunnel Calibration—Current meters also can be
7.2.2 Cable and Weight:
7.2.2.1 The cable suspension system for which the meter calibrated in flowing water—in a facility that provides a
uniform velocity distribution in a test area large enough to
rating is valid, if not furnished with the meter, shall be
precisely specified with regard to dimensions and configura- avoid blockage effects, provided that the accuracy of the
system is demonstrably high. If this procedure is used, provide
tion, including dimensions of the sounding weight, its distance
some indication of the scale and intensity of the turbulence.
from the meter, connecting strap details, cable dimensions, etc.
9.4 Group Ratings— A rating equation provided by a
7.2.2.2 Theweight shall offer minimal resistance totheflow
manufacturer for a specific type of current meter is sometimes
and should be able to maintain a stable and level position. It
used in place of an individual calibration equation.
shall be so shaped that the current meter is not subject to shed
9.4.1 Base group ratings can be made, based on individual
eddies or other instabilities; and it shall be heavy enough to
ratings of a significant number of meters with specified type of
avoid excessive downstream deflection of the cable, particu-
suspension (4). Preferably both new and well-maintained used
larly in deep and swift currents. If some deflection is unavoid-
meters should be included. Make the size, make-up, and
able, tables for air-line and wet-line corrections are available.
standard deviation of the sample known to the user.
7.2.2.3 The suspension cable preferably shall be reverse-lay
9.4.2 A group rating pertains only to current meters manu-
sounding cable to minimize torque on the immersed meter and
facturedinaspecificmanner.Anychangeinthemanufacturing
weight. However, even this type of cable may cause or allow
process requires reexamination of the group equation and
meter yaw and subsequent meter registration errors for Price-
appropriate adjustment if needed.
type current meters in velocities below 1.00 ft/s (0.305 m/s).
7.2.2.4 For protection of the meter it is preferable that the
10. Field Use and Maintenance
weight be mounted below the meter.
10.1 Spin Tests (see also 7.1.5.5):
10.1.1 Make spin tests for meters that are amenable to spin
8. Sampling
tests at least once during each day’s use. More frequent testing
8.1 Sampling, as defined in Terminology D 1129, is not
is recommended when velocities are low, when silt concentra-
applicable in this test method. Sampling to obtain a reliable
tion is high, or a meter malfunction is suspected.
measurement of average velocity in a cross section is covered
10.1.1.1 Spin tests must be made with the meter supported
in Test Method D 3858.
in a level and wind-free environment. The spin shall meet the
specified duration after a firm manual start and shall come to a
9. Calibration
gradual stop. Spin duration information must be supplied by
9.1 General Calibration Requirements:
the manufacturer for a specific meter. Some organizations
9.1
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