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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard supersedes GB/T 1576-2008 Water quality for industrial boilers. In addition to a number of editorial changes, the following main technical changes have been made with respect to GB/T 1576-2008:
——The definitions of raw water and desalted water are modified; the term “internal chemical boiler water treatment” is changed to “internal treatment”, with its definition modified; and the term “water treatment by natural occurring alkalinity in raw water” is added (see clause 3; clause 3 in Edition 2008);
——4.1 “General” is added (see 4.1);
——The index value of the turbidity of the boiler feed water is unified; the pH value of the boiler feed water and the alkalinity of the boiler water are modified; the conductivity index of the boiler water is added (see Table 1; Table 1 in Edition 2008);
——The application scope and requirements of internal treatment are modified (see 4.3.1; 4.2.1 in Edition 2008);
——The index of iron in boiler feed water is added (see Table 2);
——The dissolved oxygen index of boiler feed water and the lower limit of alkalinity in concurrent boiler feed water are modified; the conductivity indexes of boiler feed water and boiler water of both once-through boiler and concurrent boiler are added (see Table 3; Table 3 in Edition 2008);
——The index of copper in the back water is added (see Table 4);
——The index of “oil” is deleted; the upper limit of pH in boiler water is modified; the indexes of iron, oil, phenolphthalein alkalinity and dissolved oxygen are added (see Table 5; Tables 3 and 4 in Edition 2008);
——The boiler blowdown rate control requirements for make-up water quality are deleted (see 4.5.4 in Edition 2008);
——In the water quality analysis method, the turbidity determination method is changed from Annex A in Edition 2008 to the one in GB/T 15893.1; for the oil determination, the method in Annex C of Edition 2008 is deleted; for total iron determination, the method in GB/T 14427 is added; for the dissolved solid determination, the method in GB/T 14415 is added, and the copper determination method in GB/T 13689 is added; for chloride determination (ammonium thiocyanate titration method), the method is changed from that in Annex G of Edition 2008 to the one in GB/T 29340 (see clause 5; clause 5 as well as Annexes A, C and G in Edition 2008);
——The provisions of B.4.2 in Annex B are modified (see B.4.2; D.4.2 in Edition 2008);
——The Annexes A, C and G in Edition 2008 are deleted (see Annexes A, C and G in Edition 2008).
This standard was proposed by and is under the jurisdiction of SAC/TC 262 National Technical Committee on Boilers and Pressure Vessels of Standardization Administration of China.
The previous editions of this standard replaced by this standard are as follows:
——GB 1576-1979, GB 1576-1985, GB 1576-1996, GB 1576-2001 and GB/T 1576-2008.
Water quality for industrial boilers
1 Scope
This standard specifies the water quality requirements for boiler feed water, boiler water, back water and make-up water of industrial boilers in operation.
This standard is applicable to fixed steam boilers, multifunctional boilers and hot water boilers with rated outlet steam pressure less than 3.8 MPa and with water as medium.
This standard is not applicable to boilers made of aluminum.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 601 Chemical reagent - Preparations of standard volumetric solutions
GB/T 603 Chemical reagent - Preparations of reagent solutions for use in test methods
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 6903 Analysis of water used in boil and cooling system - General rule
GB/T 6904 Water used in industrial circulating cooling system and boiler - Determination of pH
GB/T 6907 Analysis of water used in boil and cooling system - The sampling method of water
GB/T 6908 Analysis of water used in boil and cooling system - Determination of electrical conductivity
GB/T 6909 Analysis of water used in boiler and cooling system - Determination of hardness
GB/T 6913 Analysis of water used in boiler and cooling system - Determination of phosphate
GB/T 12145 Quality criterion of water and steam for generating unit and steam power equipment
GB/T 12151 Analysis of water used in boiler and cooling system - Determination of turbidity - Formazine turbidity
GB/T 12152 Water for boiler and cooling system-Determination of mineral oil
GB/T 12157 Water for industrial circulating cooling system and boiler - Determination of dissolved oxygen
GB/T 13689 Water for industrial circulating cooling system and boiler - Determination of copper
GB/T 14415 Water for industrial circulating cooling system and boiler - Determination of solids matter
GB/T 14427 Analysis of water used in boil and cooling system - Determination of iron
GB/T 15453 Water for industrial circulating cooling system and boiler - Determination of chlorine
GB/T 15893.1 Industrial circulating cooling water - Determination of turbidity - Diffused radiation method
GB/T 29340 Analysis of water used in boil and cooling system - Determination of chloride - Ammonium thiocyanate titration method
DL/T 502.1 Analytical methods of steam and water in power plants - Part 1: General rule
DL/T 502.25 Analytical methods of steam and water in power plants - Part 25: Determination of iron (Spectrometric method using sulphosalicylic acid)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
raw water
the source water of the boiler make-up water
3.2
softened water
water from which all or most of the calcium and magnesium ions are removed
3.3
desalted water
finished water obtained by removing impurities in water such as suspended matters, colloids, anion and cation using various water treatment processes
Note: The desalted water in this standard mainly refers to the water having been subjected to reverse osmosis treatment or reverse osmosis plus ion exchange treatment.
3.4
make-up water
water used to supplement the loss of steam and water in boilers and heating systems
3.5
boiler feed water
the water that enters the boiler directly, usually composed of make-up water, back water and drain water
3.6
boiler water
water in the boiler in operation, which absorbs heat to produce steam or hot water
3.7
back water
water formed by condensation of steam from steam boiler after acting or carrying out heat exchange, which then backs to the boiler
3.8
water treatment by natural occurring alkalinity in raw water
water treatment method whereby boiler scaling and corrosion can be effectively avoided or mitigated only by alkalinity in raw water and reasonable sewage discharge when the alkalinity in raw water is greater than the hardness of 1 mmol/L or above
3.9
internal treatment
water treatment method of avoiding or mitigating boiler scale and corrosion by adding agents, partial softening or water treatment by natural occurring alkalinity in raw water combining reasonable sewage discharge methods
3.10
external treatment
water treatment method of treating, by means of necessary processes, the impurities, which is harmful to the operation of boiler, in raw water before it enters the boiler
4 Water quality standard
4.1 General
4.1.1 All measurement units of hardness and alkalinity in the water quality indexes shall be based on monovalent ions.
4.1.2 All dissolved oxygen indexes are the control indexes after deoxidation treatment.
4.1.3 One of the conductivity and dissolved solid in the boiler water can be selected as the control index of the boiler water concentration.
4.1.4 The sulfite index in boiler water is suitable for boilers with sulfite as an oxygen scavenger. The phosphate index is suitable for boilers with phosphate as a scale inhibitor.
4.1.5 When the stopped (standby) boiler is started (with preparation), the water quality of the boiler water shall meet the requirements of this standard within 8 hours or after the boiler water is concentrated by 10 times.
4.2 Water quality of natural circulation steam boilers and multifunctional boilers adopting external treatment
4.2.1 The water quality of the boiler feed water and boiler water of natural circulation steam boilers and multifunctional boilers adopting external treatment shall meet the requirements of Table 1.
4.2.2 For boilers supplying steam to turbines, the steam quality shall comply with the standard for steam drum boiler with a rated steam pressure falling within the range of 3.8 MPa to 5.8 MPa according to GB/T 12145.
4.2.3 For boilers with rated evaporating capacity larger than or equal to 10 t/h, the boiler feed water shall be deaerated; for the boiler with rated evaporating capacity less than 10 t/h, if local oxygen corrosion is found, deoxidation measures shall also be taken.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Water quality standard
5 Methods for water quality analysis
Annex A (Normative) Determination of dissolved oxygen (oxygen electrode method)
Annex B (Normative) Determination of dissolved solids (gravimetric method)
Annex C (Normative) Indirect determination of dissolved solids in boiler water
Annex D (Normative) Determination of phosphate (phosphorus molybdenum blue colorimetry)
Annex E (Normative) Determination of alkalinity (acid-base titration)
Annex F (Normative) Determination of sulphite (iodometric method)
