ISO 9555-3:1992 オープンチャネル内の液体の流れの測定—定常流の測定のためのトレーサー希釈法—パート3：化学トレーサー | ページ 2

3.1 定義

希釈法を含む流量測定の多くの側面に関する定義は、ISO 772 に記載されています。ISO 9555 のこの部分の目的のために、以下の定義が適用されます。

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75% of the member bodies casting a vote.

International Standard ISO 9555-3 was prepared by Technical Committee ISO/TC 113, Measurement of liquid flow in open channels, Sub-Committee SC 4, Dilution methods.

ISO 9555 consists of the following parts, under the general title Measurement of liquid flow in open channels — Tracer dilution methods for the measurement of steady flow:

• Part 1: General
• Part 2: Radioactive tracers
• Part 3: Chemical tracers
• Part 4: Fluorescent tracers

Annex A forms an integral part of this part of ISO 9555.

Introduction

The former standard series ISO 555 was subdivided into parts on the basis of the method of field measurement, i.e. constant-rate injection method and integration (sudden injection) method. Since the choice of the type of tracer to be used in a field measurement will often depend on the expertise and the laboratory facilities available, this new series of standards ISO 9555 is divided into parts based on the type of tracer used. This revision has enabled the unnecessary repetition of text of the various parts to be avoided and will, it is hoped, prove to be a more convenient form of presentation for the user.

ISO 9555 deals with the measurement of steady flow in open channels by dilution methods using tracers. The methods described may also be applied to the measurement of slowly varying flow, but they may only be used when flow conditions ensure adequate mixing of the injected solution throughout the flow.

For the measurement of very large flows, tracer methods can be onerous in terms of tracer costs and measurement times. However, the use of tracers often reduces danger to personnel during flood periods.

ISO 9555-1 presents the general principles of the methods of constantrate injection and integration (sudden injection). ISO 9555-2, ISO 9555-3 and ISO 9555-4 deal with the specific aspects of the use of radioactive, chemical and fluorescent tracers, respectively, as well as specific analytical procedures.

This approach has been adopted for the following reasons:

• to facilitate subsequent updating, additions or revisions which concern only ISO 9555-2, ISO 9555-3 or ISO 9555-4;
• to provide a more practical document for the user, who is often obliged to choose the tracer best suited to the available analytical equipment.

1 Scope

This part of ISO 9555 deals with the use of chemical tracers in discharge measurements by the dilution method. Apparatus and methods of general application are set out in ISO 9555-1 and are not repeated here, with the exception of those relating specifically to chemical tracers.

Chemical tracers have several advantages as follows.

• a) As with fluorescent tracers, the handling of the tracer follows normal chemical laboratory practice, and no special equipment (e.g. radiation shielding) is required. Care is still required, however, when handling concentrated tracer, to avoid contamination of samples and, with some tracers, for reasons of chemical toxicity.
• b) In general, chemical tracers are widely available commercially, and may be stored indefinitely.
• c) Analysis may be possible using laboratory facilities currently used for water quality determination.
• d) In general, chemical tracers are photochemically stable.

The disadvantages of chemical tracers are as follows:

• a) Their detection limits are relatively high and therefore a larger quantity of tracer is required for each gauging than in the case of radioactive or fluorescent tracers. For practical reasons this may restrict their application to small discharges. However, for certain tracers, reconcentration techniques can permit the measurement of large discharges (of the order of 1 000 m³/s) where conditions of mixing and tracer loss are acceptable.
• b) With the exception of the conductivity method for sodium choride, the determination ranges of laboratory analysis methods are limited, so dilution of river samples may be necessary before analysis. This limitation means that the constant-rate injection method is preferable for chemical tracers (excepting the conductivity method) since determination of the peak concentrations resulting from a sudden injection would be difficult.
• c) Natural background levels, particularly of conductivity (resulting from dissolved solids in natural waters), may be high and variable, and this necessitates the use of a larger amount of tracer than would be apparent from a consideration of detection limits only.
• d) It is not possible to use a carrier, as in the case of radioactive tracers, and losses by adsorption may be serious in some cases.

2 Normative reference

The following standard contains provisions which, through reference in this text, constitute provisions of this part of ISO 9555. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of ISO 9555 are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.

3 Definitions and symbols

3.2 Symbols

The symbols used in this part of ISO 9555 are defined where they occur in the text.

3.3 Units of measurement

The units of measurement used in this part of ISO 9555 are SI units.