GB/T 6908-2018Analysis of water used in boiler and cooling system—Determination of electrical conductivity (English PDF)

Foreword

This standard was drafted in accordance with the rules given in GB/T 1.1-2009.

This standard replaces GB/T 6908-2008 "Determination of Conductivity of Boiler Water and Cooling Water Analysis Methods", and GB/T 6908- In 2008, in addition to editorial changes, the main technical changes are as follows.

--- Revised scope (see Chapter 1, Chapter 1 of the 2008 edition);

--- Adjust the contents of Table 1 in 5.8 to Appendix A (see Appendix A, 2008 edition 5.8);

--- Deleted Table 2 in 7.2 (see 2008 edition 7.2);

--- Added the requirement to "measure water samples with conductivity less than 3µS/cm" (see 7.4);

--- Removed the operation of "conductivity constant correction" (see 2008 edition 7.6);

--- Modify "precision" to "permitted poor" (see Chapter 9, Chapter 8 of the 2008 edition);

--- Removed the test report (see Chapter 9 of the 2008 edition).

1 Scope

This standard specifies the method for determining the conductivity of boiler water and cooling water.

This standard is applicable to the determination of conductivity in boiler water, cooling water and demineralized water.

This standard also applies to the determination of the conductivity of natural water and domestic water.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 6682-2008 Analytical laboratory water specifications and test methods

GB/T 6907 boiler water and cooling water analysis method water sample collection method

3 Principle

The acid, alkali, and salt electrolyte dissolved in water dissociate into positive and negative ions in the solution, so that the electrolyte solution has electrical conductivity and conductivity. The size is expressed in terms of conductivity.

4 Reagents or materials

4.1 General. Reagents and water used in this standard, unless otherwise specified, should be used with superior grade reagents and in accordance with GB/T 6682 secondary water.

4.2 Potassium chloride.

4.3 Potassium chloride standard solution I. c (KCl) = 0.1 mol/L. Weigh 7.455g of potassium chloride which was previously dried at 105 ° C ~ 110 ° C for 2 h, Dissolve in water, transfer to a 1000 mL volumetric flask, dilute to the mark at (20 ± 2) °C, and mix. Put in a polyethylene bottle or a hard glass bottle Medium, sealed and preserved. Or use a commercially available standard solution.

4.4 Potassium chloride standard solution II. c (KCl) = 0.01 mol/L. Weigh 0.7455g of potassium chloride dried at 105 ° C ~ 110 ° C for 2 h, After dissolving in water, transfer it to a 1000 mL volumetric flask, dilute to the mark at (20 ± 2) °C, and mix. Put in a polyethylene bottle or a hard glass bottle, Sealed and stored. Or use a commercially available standard solution.

4.5 Potassium chloride standard solution III. c (KCl) = 0.001 mol/L. Pipette 100 mL of potassium chloride standard solution at (20 ± 2) °C with a pipette (4.4) In a 1000 mL volumetric flask, dilute to the mark with first-grade water and mix.

4.6 Potassium chloride standard solution IV. c (KCl) = 1 x 10^-4 mol/L. Pipette 10 mL of potassium chloride standard solution at (20 ± 2) °C In a liquid (4.4) to 1000 mL volumetric flask, dilute to the mark with primary water and mix.

5 Instruments

5.1 Conductivity meter. Select the appropriate conductivity meter according to the conductivity measurement range of the water sample to be tested. Measuring conductivity less than 0.1µS/cm When the water sample is used, the instrument resolution is 0.005 µS/cm.

5.2 Conductive electrode (referred to as electrode). Select the appropriate conductivity electrode according to the conductivity measurement range of the water sample to be tested. […]