GB/T 45124-2024Measurement of liquid flow in closed conduits - Volumetric method (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for standardization work Part 1: Structure and drafting rules for standardization documents" Drafting.

This document is modified to adopt ISO 8316:1987 "Measurement of liquid flow in closed conduits - Volumetric trough liquid collection method".

Compared with ISO 8316:1987, this document has made the following structural adjustments.

--- Appendix A corresponds to Appendix D in ISO 8316:1987;

--- Appendix B corresponds to Appendix C in ISO 8316:1987;

--- Appendix C corresponds to Appendix A in ISO 8316:1987;

--- Appendix E corresponds to Appendix B in ISO 8316:1987;

--- Appendix H corresponds to Appendix E in ISO 8316:1987.

The technical differences between this document and ISO 8316:1987 and their reasons are as follows.

--- Deleted the statement that the device needs to be subject to regular verification (see Chapter 1), which conflicts with the existing standards in my country;

--- Changed the symbol table (see 3.2) to comply with the latest provisions of ISO 5168;

--- Added two typical flow device schematics of static volume method (see 4.1.1), and changed the flow device principle of dynamic volume method

Figure (see 4.1.2) to better adapt to the current status of domestic device technology;

--- The optimal uncertainty of the device (see 4.2.1) has been changed to better adapt to the current status of domestic device technology;

--- Added the uncertainty table of standard devices (see Table 2) to better adapt to the current status of domestic device technology;

--- Added two accurate measurement requirements (i) and (j) (see 4.2.2) to reduce the source of error;

---Changed the cross-sectional length of the commutator trickle, added three open commutators and one closed commutator structure schematic diagram (see 5.1) to better adapt to the current status of domestic commutator technology;

--- Changed the commutation cycle reading scale value (see 5.2) because the commutation cycle scale value accuracy in the industry has been improved;

--- The minimum change requirement of the liquid level has been deleted. Due to different settings of the working volume, the minimum change of the liquid level is not necessarily 1m (See 5.3 of ISO 8316:1987);

--- Changed the residual liquid discharge waiting time (see 5.5), based on the waiting time of the metal measuring vessel in the dripping state;

--- Added device software requirements (see 5.6), because existing standard devices in the industry basically have software;

--- Changed the principle description of the static volume method and the dynamic volume method (see 6.1 and 6.2) to better adapt to the current status of volume method technology;

--- Changed the number of measurements for each measuring point (see 6.4) to be consistent with the existing standards in my country;

--- The structure and content of Chapter 8 (see Chapter 8) have been changed to meet the uncertainty requirements in the existing standards of my country.

The following editorial changes were made to this document.

--- In order to coordinate with the existing standards, the name of the standard is changed to "Volumetric method for measuring liquid flow in closed pipes";

--- Added the one-way valve identification in the volume flow device schematic diagram of the static start-stop method (see A.1);

--- Added measurement control system (see Appendix D);

--- Changed the query table of pure water density under standard atmospheric pressure (see Appendix E);

--- Added correction for density measurement using a densitometer (see Appendix F);

--- Added uncertainty calculation examples (see Appendix G);

--- Changed the t distribution table (see Appendix H);

--- Deleted the reference to ISO 4185 and included the document as a reference.

1 Scope

This document describes a method for determining the flow rate of a liquid in a closed conduit by measuring the volume of liquid flowing into a working volume per unit time.

(hereinafter referred to as "volumetric method"), including principle, apparatus, implementation steps, flow calculation and measurement-related uncertainty assessment.

The method described in this document is applicable to liquids that meet the following conditions.

a) The measuring medium is a low vapor pressure liquid (to ensure that any liquid evaporating from the working volume does not affect the required measurement accuracy).

accuracy);

b) low viscosity (will not change or unduly delay the measurement of the liquid level in the working volume);

c) Non-toxic and non-corrosive characteristics.

Theoretically, there is no limit to the application of this method, but for practical reasons this measurement method is usually used for flow rates less than 5400m3/h occasions and laboratory fixed devices. However, this method has a natural or artificial reservoir as the volume tank this document does not cover such applications.

Due to the high accuracy of this method, it is often used as a benchmark method to calibrate other volume flow measurement or mass flow measurement.

For calibrating mass flow measuring devices, the density of the liquid needs to be known accurately.

If the volumetric flow measurement device is used for statutory measurement, it must undergo measurement standard assessment and authorization.

2 Normative references

The contents of the following documents constitute the essential clauses of this document through normative references in this document.

For referenced documents without a date, only the version corresponding to that date applies to this document; for referenced documents without a date, the latest version (including all amendments) applies to this document.

Note. GB/T 17611-1998 Measurement terms and symbols for fluid flow in closed pipes (ISO 4006:1991, IDT) Note. GB/T 27759-2011 Fluid flow measurement uncertainty assessment procedure (ISO 5168:2005, IDT)

3 Terms, definitions and symbols