Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is drafted in accordance with the rules given in GB/T 1.1-2009 Directives for standardization—Part 1: Structure and drafting of standards.
Attention is drawn to the possibility that some of the elements of this standard may be the subject of patent rights. The issuing authority of this standard shall not be held responsible for identifying any or all such patent rights.
This standard is a revision of DL/T 677-2009, including the main technical contents:
——The definition of on-line checking is added.
——The technical requirements of various on-line chemical instruments are modified.
——The complete machine error test principle, complete machine error calculation equations and technical requirements of various on-line chemical instruments are modified.
——Some test items of on-line chemical instruments are deleted.
——Relevant annexes and tables are modified according to the revised contents.
This standard was proposed by the China Electricity Council (CEC).
This standard is under the jurisdiction of Technical Committee on Power Plant Chemistry of Standardization Administration of Power Industry (DL/TC13).
The previous editions of standards replaced by this standard are as follows:
——DL/T 677-1999 and DL/T 677-2009.
In the process of implementing this standard, the relevant comments and recommendations, whenever necessary, may be fed back to the Standardization Center of China Electricity Council (No.1, 2nd Lane, Baiguang Road, Beijing, 100761, China).
Inspection code of on-line chemical instruments for power plant
1 Scope
This standard specifies the technical requirements, test conditions and test methods of on-line instruments for conductivity, pH, sodium ion, dissolved oxygen and silicate in power plants.
This standard is applicable to the acceptance test of the above-mentioned on-line chemical instruments in power plants when they are newly purchased and the measurement test during operation. It may also serve as a reference for laboratory chemical instruments.
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 6903 Analysis of water used in boil and cooling system—General rule
GB/T 12148 Methods for analysis of water for boiler and for cooling—Determination of total silicon—Photometric method by conversion with hydrofluoric acid for low silicon
GB/T 12149 Analysis of water used in boiler and cooling system—Determination of silica—Molybdenum blue colorimetry
GB/T 13966 Terminology for analytical instruments
GB/T 27501 Preparation method of buffer solutions for the measurement of pH value
DL/T 913 Quality inspection guide for water quality analyzers in thermal power plant
JJG 119 Verification regulation of laboratory pH meters
JJG 291 Dissolved oxygen meter with covered-membrane-electrode
JJG 376 Electrolytic conductivity meters
JJG 757 Verification regulation of ionometers
3 Terms and definitions
For the purpose of this standard, the following terms and definitions apply.
3.1
on-line chemical instruments
on-line industrial process composition analysis instrument specially used for chemical supervision in the production process of power plants, that is, on-line industrial chemical analysis instrument. In the electric power industry, in order to distinguish electrical measuring instruments from thermal instruments, it is called on-line chemical analysis instruments, referred to as on-line chemical instruments for short
3.2
on-line checking
method for local on-line inspection of on-line chemical instruments, or simulating the normal measurement state of on-line chemical instruments to continuously introduce standard water samples close to the measured water samples into the on-line chemical instruments for accuracy inspection
3.3
operating error
error measured at any point within normal operating conditions
3.4
indication error
difference between the indication value of the instrument and the measured [agreed] true value
3.5
fiducial error
ratio of instrument's indication error to fiducial value
Note: The fiducial value of this standard adopts the maximum value in measuring range.
3.6
maximum value in measuring range—M
minimum value one order of magnitude higher than the standard value of the water sample monitored by the instrument
Note: See Annex A for M values of different water samples.
3.7
display devices fiducial error
ratio of the indication error of the display device to the maximum value in measuring range of the display device
3.8
temperature compensation additional error
error generated when the instrument is used under non-standard conditions, called additional error. In order to test the self compensation performance of the instrument under different temperature conditions, this index is defined as the temperature compensation additional error
3.9
sample line leakage additional error
relative error of instrument indication value caused by leakage of measurement system
3.10
zero error
error of indication measured by the instrument when the agreed true value is zero
3.11
stability
ability of a measuring instrument to keep its measuring characteristics constant under specified conditions and to keep it constant during continuous operation within a certain period of time (24h)
3.12
repeatability
degree of consistency of a series of results measured by using the same method, the same specimen and under the same conditions. The same conditions include the same operator, the same instrument, the same laboratory and a short time interval
Note: Repeatability represents the random error of instrument, excluding drift and backlash.
3.13
indication of a measuring instrument
value measured and displayed by the measuring instrument
3.14
standard material
material with sufficient accuracy to calibrate or verify instruments, evaluate measurement methods or assign values to other materials
4 Quality acceptance of on-line chemical instruments
4.1 On-line chemical instruments shall be accepted according to the requirements of this standard. See Tables 1, 2, 4, 5, 7, 8, 10, 11 and 13 for specific testing items and technical requirements.
4.2 The standard instruments and devices (standard conductivity meter, standard hydrogen exchange column, standard pH meter, and mobile pH, sodium, dissolved oxygen standard water sample preparation device) used to inspect the on-line chemical instruments of the pure water system shall be traceable and qualified by the primary laboratory of chemical instruments in the power plant.
5 On-line conductivity meter
5.1 Technical requirements
5.1.1 The test items, technical requirements and test cycles of complete machine of on-line conductivity meter shall meet those specified in Table 1.
Table 1 Test items, technical requirements and test cycle of complete machine of on-line conductivity meter
Item Requirements Test cycle
In operating After overhaul Newly purchased
Test for complete machine a Operating error δG
% −10<δG<10 Once per month b √ √
Fiducial error δZ
% −1<δZ<1 Once per month b √ √
a Test the operating error or fiducial error according to the test principle for complete machine specified in 5.4.1.
b For on-line conductivity meters that have passed the test for three consecutive test cycles, the test cycle may be relaxed to once every three months.
5.1.2 When the test result of complete machine is unqualified, the items given in Table 2 shall apply.
Table 2 Test items, technical requirements and test cycles of display device and others of on-line conductivity meter
Item Requirements Test cycle
In operating After overhaul Newly purchased
Test for display device Fiducial error δY
% −0.3<δY<0.3 As required a — √
Temperature compensation additional error δt
×10-3 °C-1 −0.3<%t<0.3 As required a — √
Electrode constant error δD
% −1<δD<1 As required a — √
Exchange column additional error δJ
% −3<δJ<3 As required a — √
Temperature measurement error t
°C –0.5<t<0.5 As required a — √
a When the test result of complete machine is unqualified, the items in this table shall apply.
5.2 Test conditions
The test conditions for on-line conductivity meter shall meet those specified in Table 3.
Table 3 Test conditions for on-line conductivity meter
Test condition Specifications and requirements
Temperature of water sample
°C 5–50
Flow of water sample Flow required by instrument manufacturer
5.3 Test equipment and standard solution
5.3.1 The standard conductivity meter shall meet the following requirements at the same time:
a) the complete machine fiducial error shall not be greater than ± 0.5%.
b) capable of measuring flowing water samples.
c) at least has the function of non-linear temperature compensation for mixed bed effluent water sample, ammonia-containing water sample, hydrogen type cation exchange column effluent or other cation exchange equipment effluent water samples.
d) capable of eliminating the influence of differential capacitance on electrode surface and distributed capacitance of wire.
e) regularly verified to meet the value transfer conditions.
5.3.2 Standard AC resistance box and DC resistance box with accuracy better than Grade 0.1.
5.3.3 Precision thermometer, with measuring range of 0°C–50°C and minimum division value of 0.1°C.
5.3.4 Adjustable constant temperature water bath with accuracy of ± 2°C and range from ambient temperature to 50°C.
5.3.5 The standard hydrogen exchange column shall meet the following requirements at the same time:
a) equipped with hydrogen cation exchange resin with regeneration degree greater than 98%.
b) the resin crack is less than 1%.
c) the exchange column additional error not exceed ± 2%.
Note: Other types of cation exchange equipment meeting the above conditions may be used for standard hydrogen exchange columns.
5.3.6 Potassium chloride standard solution
Note: The conductivity standard solution may be prepared according to B.1 and B.2 in Annex B.
5.3.7 Device capable of continuously producing stable low conductivity water samples.
5.4 Test for the complete machine error
5.4.1 Test principles
For the conductivity meter measuring the conductivity value of water sample not greater than 0.30 μS/cm, the on-line checking shall be adopted to test the complete machine operating error; for conductivity meter measuring the conductivity value greater than 0.30 μS/cm, the on-line checking should be adopted to test the complete machine operating error, or the off-line test method of static standard solution may be adopted to test the complete machine fiducial error.
5.4.2 Test for complete machine operating error (on-line checking)
For the instrument measuring direct conductivity, connect the conductivity cell of the standard meter in parallel (or in series) with the conductivity cell of the tested meter nearby according to Figure 1, and the water sample of the tested meter during normal measurement is used; for the instrument measuring hydrogen conductivity, connect the conductivity cell of the standard meter and the conductivity cell of the tested meter to the standard hydrogen exchange column and the on-line hydrogen exchange column respectively as shown in Figure 2, and the water sample of the tested meter during normal measurement is used. The flow rate of water sample shall be adjusted according to the requirements to meet the conditions specified in Table 2 and remain relatively stable. After the measured values of the tested meter and the standard meter are stable, accurately read the conductivity indication of the tested meter (κJ) and conductivity indication of standard meter (κbB) and record the temperature indication of the standard meter. See Table C.1 in Annex C for the record format of test data.
Figure 1 Schematic diagram of test for complete machine operating error of conductivity meter
Figure 2 Schematic diagram of test for complete machine operating error of hydrogen conductivity meter
See Equation (1) for the calculation method of the complete machine operating error.
(1)
where,
δG——the complete machine operating error, %;
κJ——the conductivity indication of tested meter, μS/cm;
κbB——the conductivity indication of standard meter, μS/cm.
Note: If the conductivity of the water sample is unstable, the device capable of continuously producing stable low conductivity water samples shall be adopted to produce stable conductivity water samples, and the conductivity of the water samples shall be less than 0.30 μS/cm.
5.4.3 Test for complete machine fiducial error (off-line test method of static standard solution)
First, set the electrode constant of the tested meter to be consistent with the electrode constant of the supporting electrode of the instrument, and select the standard solution with conductivity greater than 100 μS/cm and in the measuring range of the tested meter. Thermostate the standard solution to 25°C ± 2°C, put the conductivity electrode of the tested meter into the standard solution, and record the conductivity value (κb) of the standard solution after the temperature is stable, accurately read the indication value (κJ) of the tested meter and the temperature value of the solution. See Table C.2 in Annex C for the record format of test data.
See Equation (2) for the calculation method of the complete machine fiducial error.
(2)
where,
δZ——the complete machine fiducial error, %;
κJ——the conductivity indication of tested meter, μS/cm;
κb——the conductivity of standard solution, μS/cm. The conductivity value of standard solution at reference temperature (25°C) can be found from Table B.1 in Annex B according to the prepared potassium chloride standard solution;
M——the maximum value in measuring range, μS/cm.
Note: If the electrode constant is equal to or less than 0.1 cm-1, the complete machine operating error shall be tested according to 5.4.2.
5.5 Test for display device
5.5.1 Test for fiducial error
5.5.1.1 Test principle
For the conductivity meter with measured conductivity value greater than 0.30 μS/cm, the standard AC resistance box (see Figure 3) shall be used as the standard input signal of conductivity for testing. For conductivity meters with measured conductivity value not greater than 0.3 μS/cm, analog circuits (see Figure 4) shall be used as standard signals of conductivity for testing.
5.5.1.2 Test method
Standard AC resistance box and standard DC resistance box with accuracy better than Grade 0.1 are used to simulate solution equivalent resistance RX and temperature resistance Rt respectively as the analog signal of test. Adjust the analog temperature resistance Rt so that the temperature displayed by the instrument is 25°C. Set the conductivity cell constant of the tested meter to 0.01 (or 0.1). The connection between the tested meter and the standard AC resistance is shown in Figure 3. For the conductivity meter with measured conductivity value not greater than 0.30 μS/cm, the AC resistance box RX in Figure 3 is replaced by the analog circuit in Figure 4, where, RX is a standard AC resistance box.
Figure 3 Connection between the tested meter and the standard resistance box
Figure 4 Analog circuit for test of display device of pure water conductivity meter
After the measured value of the tested meter is stable, the analog equivalent resistance signal is input to the display device according to the calculation result of Equation (3).
(3)
where,
RX——the equivalent resistance, Ω;
J——the conductivity cell constant set by the tested meter, cm-1;
κL——the theoretical conductivity, μS/cm.
Record the electrical conductivity indication value, κS, of the tested meter. See Equation (4) for the calculation method of fiducial error of display device. See Table C.3 in Annex C for the record format of test data.
(4)
where,
δY——the fiducial error of display device, %;
κS——the conductivity indication of tested meter, μS/cm;
κL——the theoretical conductivity, μS/cm;
M——the maximum value in measuring range, μS/cm.
5.5.2 Test for temperature compensation additional error of display device
Standard AC resistance box and standard DC resistance box with accuracy better than Grade 0.1 are used to simulate solution equivalent resistance RX and temperature resistance Rt respectively as the analog signal of test, which shall be connected in Figure 3.
Set the instrument temperature compensation correctly according to the manual of the tested meter. For example, the non-linear compensation mode for pure water or ultra-pure water is selected to measure the direct conductivity of water samples in mixed bed effluent (desalted water, etc.); the non-linear compensation mode for acidic water sample is selected to measure the hydrogen conductivity of hydrogen cation exchange column effluent water sample; the non-linear compensation mode for ammonia water sample is selected to measure the direct conductivity of ammonia water sample; and the linear compensation of 2% is selected to measure the conductivity of common water sample. The test for temperature compensation additional error of the display device of the on-line conductivity meter used for different types of water samples shall be carried out according to the following procedure:
a) measure the effluent sample of the mixed bed. Set the electrode constant of the tested meter to 0.01 cm-1. Adjust the analog temperature resistance Rt so that the temperature displayed by the instrument is 25°C, and then adjust the solution equivalent resistance RX to 100,000Ω using Equation (3) so that the conductivity displayed by the instrument is 0.1 μS/cm, and record the indication value κt1 of the instrument. Adjust the analog temperature resistance Rt so that the temperature displayed by the instrument is 35°C, calculate the solution equivalent resistance RX as 69,930Ω using Equation (5), adjust RX value as 69,930Ω, and record the indication value κt2 of the instrument.
b) Measure the effluent sample of the hydrogen cation exchange column. Set the electrode constant of the tested meter to 0.01 cm-1. Adjust the analog temperature resistance Rt so that the temperature displayed by the instrument is 25°C, and then adjust the solution equivalent resistance RX to 100,000Ω using Equation (3) so that the conductivity displayed by the instrument is 0.1 μS/cm, and record the indication value κt1 of the instrument. Adjust the analog temperature resistance Rt so that the temperature displayed by the instrument is 35°C, calculate the solution equivalent resistance RX as 72,464Ω using Equation (5), adjust RX as 72,464Ω, and record the indication value κt2 of the instrument.
c) Measure ammonia water samples. Set the electrode constant of the tested meter to 0.1cm-1. Adjust the analog temperature resistance Rt so that the temperature displayed by the instrument is 25°C, and then adjust the solution equivalent resistance RX to 33,333Ω using Equation (3) so that the conductivity displayed by the instrument is 3 μS/cm, and record the indication value κt1 of the instrument. Adjust the analog temperature resistance Rt so that the temperature displayed by the instrument is 35°C, calculate the solution equivalent resistance RX as 28,490Ω using Equation (5), adjust RX value as 28,490Ω, and record the indication value κt2 of the instrument.
d) Measure common water samples. Set the electrode constant of the tested meter to 1cm-1. Adjust the analog temperature resistance Rt so that the temperature displayed by the instrument is 25°C, and then adjust the solution equivalent resistance RX to 2,000Ω using Equation (3) so that the conductivity displayed by the instrument is 500 μS/cm, and record the indication value κt1 of the instrument. Adjust the analog temperature resistance Rt so that the temperature displayed by the instrument is 35°C, calculate the solution equivalent resistance RX as 1,667Ω using Equation (5), adjust RX value as 1,667Ω, and record the indication value κt2 of the instrument.
(5)
where,
RX——the equivalent resistance value of solution at temperature t, Ω;
J——the electrode constant set by the tested meter, cm-1;
κ——the theoretical conductivity at 25°C, μS/cm;
β——the temperature coefficient of solution.
Note: The temperature coefficients of different water samples are measured in the following ways: for the on-line conductivity meter measuring the effluent sample of the mixed bed, the conductivity value at 25°C is 0.1 μS/cm and β is taken as 0.043 at 35°C; for the on-line hydrogen conductivity meter measuring the effluent sample of hydrogen cation exchange column, the conductivity value at 25°C is 0.1 μS/cm and β is taken as 0.038 at 35°C; for the on-line conductivity meter measuring ammonia water sample, the conductivity value at 25°C is 3 μS/cm and β is taken as 0.017 at 35°C; for the on-line conductivity meter measuring common water samples, the conductivity value at 25°C is 500 μS/cm and β is taken as 0.02 at 35°C.
See Equation (6) for the calculation method of the temperature compensation additional error of the display device. See Table C.4 in Annex C for the record format of test.
(6)
where,
δt——the display devices temperature compensation additional error, ×10-3 °C-1;
κt1——the conductivity indication of the tested meter at 25°C, μS/cm;
κt2——the conductivity indication of the tested meter at 35°C, μS/cm;
M——the maximum value in measuring range, μS/cm.
5.6 Test for electrode constant
5.6.1 Test principles
For electrode constants less than 0.1 cm-1, the standard electrode method shall be used for testing. For electrode constants greater than or equal to 0.1 cm-1, the standard electrode method should be used for testing, and the off-line test method of static standard solution may also be used for testing.
5.6.2 Standard electrode method
Connect the standard conductivity cell (with electrode constant of JB) in parallel or series with the tested conductivity cell nearby as shown in Figure 1, and the conductivity of the water sample is within the range of the conductivity of the water sample normally measured by the tested conductivity cell, and keep the conductivity of the water sample unchanged during the test (if the conductivity of the water sample is unstable, use the device required in 5.3.7 to produce the water sample with stable conductivity). Set the temperature compensation mode of standard conductivity meter and tested conductivity meter as no compensation, and record the measured value κb of standard conductivity meter and the measured value κx of the tested conductivity meter after the measured value of the meter is stable. See Equation (7) for the calculation method of the tested electrode constant. See Table C.5 in Annex C for the record format.
(7)
where,
Jx——the tested electrode constant, cm-1;
κb——the measured value of standard conductivity meter, μS/cm;
κx——the measured value of tested conductivity meter, μS/cm;
JB——the electrode constant of standard electrode, cm-1.
5.6.3 Off-line test method of static standard solution
The standard solution with conductivity greater than 100 μS/cm shall be selected when the equivalent resistance of the solution is 5 × 102 Ω to 1 × 104 Ω.
Place the tested electrode in a standard solution with known standard conductivity value (with constant temperature of 25°C ± 2°C). Set the electrode constant of the tested conductivity meter to 1, and measure the conductivity G of the solution.
See Equation (8) for the calculation method of the electrode constant. See Table C.5 in Annex C for the record format.
(8)
where,
Jx——the tested electrode constant, cm-1;
κb——the conductivity of standard solution, μS/cm;
G——the conductance measured by the tested conductivity meter, μS.
5.6.4 Calculation method of electrode constant error
See Equation (9) for the calculation method. See Table C.5 in Annex C for the record format.
δ_D=(J_X-J_g)/J_g ×100% (9)
where,
δD——the electrode constant error, %;
Jx——the tested electrode constant, cm-1;
Jg——the electrode constant given by the manufacturer (or before this calibration), cm-1.
5.7 Test for exchange column additional error
5.7.1 Test methods
Connect the standard conductivity cell to the effluent of the standard hydrogen exchange column, and measure the effluent conductivity κb of the standard hydrogen exchange column by the standard conductivity meter; then connect the standard conductivity cell to the effluent of the tested on-line hydrogen exchange column, and measure the effluent conductivity κz of the tested on-line hydrogen exchange column by the standard conductivity meter.
5.7.2 Calculation method of exchange column additional error
See Equation (10) for the calculation method. See Table C.6 in Annex C for the record format.
δ_J=(κ_z-κ_b)/κ_b ×100% (10)
where,
δJ——the exchange column additional error, %;
κz——the effluent conductivity of on-line hydrogen exchange column, μS/cm;
κb——the effluent conductivity of standard hydrogen exchange column, μS/cm.
Note 1: For the standard hydrogen exchange column and the on-line hydrogen exchange column, the same water sample shall be measured during the test for exchange column additional error, and remain it stable.
Note 2: The hydrogen exchange column used in the on-line hydrogen conductivity meter may adopt other types of cation exchange equipment.
5.8 Test for temperature measurement error
Put the measuring electrode of tested conductivity meter and the standard thermometer into the same aqueous solution, and read the temperature indication tX of the tested meter and standard thermometer indication tB after the reading of the tested meter is stable. The temperature measurement error shall be calculated using Equation (11). See Table C.7 in Annex C for the record format.
t = tX - tB (11)
where,
t——the temperature measurement error, °C;
tX——the temperature indication of tested meter, °C;
tB——the standard thermometer indication, °C.
6 On-line pH meter
6.1 Technical requirements
6.1.1 The test items, technical requirements and test cycle of complete machine of on-line pH meter shall meet those specified in Table 4.
Table 4 Test items, technical requirements and test cycle of complete machine of on-line pH meter
Test item Technical requirements Test cycle
In operating After overhaul Newly purchased
Test for complete machine a Operating error δG –0.05 < δG < 0.05 Once per month √ √
Indication error δS –0.05 < δS < 0.05 Once per month √ √
Indication repeatability S S < 0.03 As required b — √
Temperature compensation additional error pHt
°C-1 –0.01 < pHt < 0.01 As required c — √
a Test the operating error or fiducial error according to the test principle for complete machine specified in 6.4.1.
b Test it when the meter reading is unstable.
c Test it when the operating error or indication error of complete machine exceeds the standard.
6.1.2 When the test result of complete machine is unqualified, the items given in Table 5 shall apply.
Table 5 Test items, technical requirements and test cycle of display device and electrode of on-line pH meter
Test item Technical requirements Test cycle
In operating After overhaul Newly purchased
Indication error pH –0.03<pH<0.03 As required a — √
Indication error caused by input impedance pHR –0.01
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Quality acceptance of on-line chemical instruments
5 On-line conductivity meter
5.1 Technical requirements
5.2 Test conditions
5.3 Test equipment and standard solution
5.4 Test for the complete machine error
5.5 Test for display device
5.6 Test for electrode constant
5.7 Test for exchange column additional error
5.8 Test for temperature measurement error
6 On-line pH meter
6.1 Technical requirements
6.2 Test conditions
6.3 Test equipment and standard solution
6.4 Test for complete machine error
6.5 Test for display device
6.6 Test for temperature measurement error
6.7 Test for electrode performance
7 On-line sodium meter
7.1 Technical requirements
7.2 Test conditions
7.3 Test equipment and standard solution
7.4 Test for complete machine error
7.5 Test for display device indication error
8 On-line dissolved oxygen meter
8.1 Technical requirements
8.2 Test conditions
8.3 Test equipment and standard solution
8.4 Test for complete machine error
8.5 Test for zero error
8.6 Test for temperature influence additional error
8.7 Test for sample line leakage additional error
9 On-line silicon meter
9.1 Technical requirements
9.2 Test conditions
9.3 Standard solution
9.4 Test for the complete machine error
9.5 Test for repeatability of complete machine
9.6 Anti phosphate interference performance test
Annex A (Normative) Maximum value M in measuring range
Annex B (Normative) Preparation method of conductivity standard solution
Annex C (Informative) Record format of on-line conductivity meter test results
Annex D (Informative) Preparation device for low conductivity standard water sample
Annex E (Normative) Preparation method of pH standard buffer solution
Annex F (Informative) Record format of on-line pH meter test results
Annex G (Normative) Preparation and preservation of sodium standard solution
Annex H (Informative) Record format of on-line sodium meter test results
Annex I (Informative) Preparation device for low concentration dissolved oxygen standard water sample
Annex J (Informative) Record format of on-line dissolved oxygen meter test results
Annex K (Normative) Preparation method of silicon dioxide standard solution
Annex L (Informative) Record format of on-line silicon meter test results
发电厂在线化学仪表检验规程
1 范围
本标准规定了发电厂在线电导率、pH、钠离子、溶解氧和硅酸根仪表的技术要求、检验条件及检验方法等内容。
本标准适用于发电厂上述在线化学仪表新购置时的验收检验和运行期间的测量检验。实验室化学仪表可参照本标准。
2 规范性引用文件
下列文件对于本文件的应用是必不可少的。凡是注日期的引用文件，仅注日期的版本适用于本文件。凡是不注日期的引用文件，其最新版本(包括所有的修改单)适用于本文件。
GB／T 6903 锅炉用水和冷却水分析方法 通则
GB／T 12148 锅炉用水和冷却水分析方法 全硅的测定 低含量硅氢氟酸转化法
GB／T 12149 锅炉用水和冷却水分析方法硅的测定 钼蓝比色法
GB／T 13966 分析仪器术语
GB／T 27501 pH测定用缓冲溶液制备方法
DL／T 913 火电厂水质分析仪表质量验收导则
JJG 119 实验室pH(酸度)计检定规程
JJG 291 覆膜电极溶解氧测定仪检定规程
JJG 376 电导仪检定规程
JJG 757 离子计检定规程
3 术语和定义
下列术语和定义适用于本标准。
3.1
在线化学仪表 on-line chemical instruments
用于发电厂生产过程中化学监督专用的在线工业流程式成分分析仪表，即为在线工业化学分析仪表。在电力行业中，为了区别电测仪表和热工仪表而称为在线化学分析仪表，简称在线化学仪表。
3.2
水样流动检验法 on-line checking
对在线化学仪表进行就地在线检验，或模拟在线化学仪表正常测量状态，向在线化学仪表连续通入与测量水样水质接近的标准水样进行准确性检验的方法。
3.3
工作误差 operating error
在正常工作条件内任意一点上测定的误差。
3.4
示值误差 error of indication
仪表的示值与被测量的[约定]真值之差。
3.5
引用误差 fiducial error
仪表的示值误差与引用值之比。
注：本标准引用值采用量程范围内最大值。
3.6
量程范围内最大值M maximum value in measuring range—M
比仪表所监测水样的标准值高一数量级的最小值。
注：不同水样的M值见附录A。
3.7
二次仪表引用误差 display devices fiducial error
二次仪表的示值误差与二次仪表量程范围内最大值之比。
3.8
温度补偿附加误差 temperature compensation additional error
仪表在非标准条件下使用时所产生的误差称为附加误差，为了检验在不同温度条件下仪表自度补偿性能，该项指标定义为温度补偿附加误差。
3.9
流路泄漏附加误差 sample line leakage additional error
测量系统泄漏造成的仪表示值的相对误差。
3.10
零点误差 zero error
仪表在约定真值为零时，测量的示值误差。
3.11
稳定性 stability
在规定条件下，计量仪表保持其计量特性恒定不变，并在一定时间内(24h)连续运行中仪表保持恒定不变的能力。
3.12
重复性 repeatability
用相同的方法、相同的试样，在相同的条件下测得的一系列结果的一致程度。相同的条件是指同一操作者、同一仪器、同一实验室和短暂的时间间隔。
注：重复性表征仪表随机误差的大小，不包括漂移和回差等。
3.13
示值 indication of a measuring instrument
测量仪表所显示的被测量的值。
3.14
标准物质 standard material
具有足够的准确度，可用以校准或检定仪表、评定测量方法或给其他物质赋值的物质。
4 在线化学仪表的质量验收
4.1 在线化学仪表应按本标准的要求进行验收，具体检测项目与技术要求见表1、表2、表4、表5、表7、表8、表10、表11和表13。
4.2 用于检验纯水系统在线化学仪表的标准仪表和装置(标准电导率表、标准氢交换柱、标准pH表，流动pH、钠、溶解氧标准水样制备装置)应经过电厂化学仪表一级实验室的溯源并达到合格。
5 在线电导率表
5.1 技术要求
5.1.1 在线电导率表整机检验项目、技术要求和检验周期应符合表1的规定。
表1 在线电导率表整机检验项目、技术要求和检验周期
项目 要求 检验周期
运行中 机组检修后 新购置
整机检验a 工作误差δG
％ －10＜δG＜10 1次／1个月 b √ √
引用误差δZ
％ －1＜δZ＜1 1次／1个月b √ √
a 根据5.4.1整机检验原则进行工作误差或引用误差的检验。
b 对于连续3个检验周期检验合格的在线电导率表，检验周期可放宽到3个月。
5.1.2 当整机检验结果不合格时，再进行表2项目的检验。
表2 在线电导率表二次仪表及其他检验项目、技术要求和检验周期
项目 要求 检验周期
运行中 机组检修后 新购置
二次仪表检验 引用误差δY
％ －0.3＜δY＜0.3 根据需要a — √
温度补偿附加误差δt
×10－3℃－1 －0.3＜％t＜0.3 根据需要a — √
电极常数误差δD
％ －1＜δD＜1 根据需要a — √
交换柱附加误差δJ
％ －3＜δJ＜3 根据需要a — √
温度测量误差t
℃ －0.5＜t＜0.5 根据需要a — √
a 当整机检验不合格时，进行该项目的检验。
5.2 检验条件
在线电导率表检验条件应符合表3的规定。
表3 在线电导率表检验条件
检验条件 规范与要求
水样温度
℃ 5～50
水样流量 仪表制造厂要求的流量
5.3 检验设备与标准溶液
5.3.1 标准电导率表应同时满足以下要求：
a)整机引用误差不大于±0.5％。
b)能够测量流动水样。
c)至少具有分别对混床出水水样、含氨水样、氢型阳离子交换柱出水或其他形式的阳离子交换设备出水水样进行非线性温度补偿的功能。
d)能够消除电极表面微分电容和导线分布电容的影响。
e)定期检定，具备量值传递条件。
5.3.2 准确度等级优于0.1级的标准交流电阻箱、直流电阻箱。
5.3.3 精密温度计，测量范围为0℃～50℃，最小分度值为0.1℃。
5.3.4 精度为±2℃，范围为室温至50℃可调恒温水浴。
5.3.5 标准氢交换柱应同时满足以下要求：
a)装有再生度大于98％的氢型阳离子交换树脂。
b)树脂裂纹小于1％。
c)交换柱附加误差不超过±2％。
注：标准氢交换柱可采用满足上述条件的其他形式阳离子交换设备。
5.3.6 氯化钾标准溶液。
注：可按照附录B中B.1、B.2的规定进行电导率标准溶液的制备。
5.3.7 具有能够连续产生稳定低电导率水样的装置。
5.4 整机误差检验
5.4.1 检验原则
对于测量水样电导率值不大于0.30S／cm的电导率表，应采用水样流动法检验整机工作误差；对于测量电导率值大于0.30μS／cm的电导率表，宜采用水样流动检验法检验整机工作误差，也可采用静态标准溶液离线检验法检验整机引用误差。
5.4.2 整机工作误差检验(水样流动检验法)
对于测量直接电导率的仪表，按图1将标准表的电导池就近与被检表的电导池并联(或串联)连接，水样为被检表正常测量时的水样；对于测量氢电导率的仪表，按图2将标准表的电导池和被检表的电导池分别连接在标准氢交换柱和在线氢交换柱后，水样为被检表正常测量时的水样。水样的流速按照要求调整至符合表2的规定条件，并保持相对稳定。被检表和标准表测量值稳定后，精确读取被检表电导率示值(κJ)与标准表电导率示值(κbB)，并记录标准表的温度示值。检验数据的记录格式见附录C中的表C.1。
被检仪表电导池
标准表电导池
水样
图1 电导率表整机工作误差检验示意图
被检仪表电导池
标准表电导池
在线氢交换柱
标准氢交换柱
水样
图2 氢电导率表整机工作误差检验示意图
整机工作误差计算方法见式(1)。
(1)
式中：
δG——整机工作误差，％；
κJ——被检表电导率示值，μS／cm；
κbB——标准表电导率示值，μS／cm。
注：如果水样电导率不稳定，则使用能够连续产生稳定低电导率水样的装置产生稳定电导率的水样，水样电导率应小于0.30μS／cm。
5.4.3 整机引用误差检验(静态标准溶液离线检验法)
首先设定被检表的电极常数与仪表配套电极的电极常数一致，选择电导率大于100μS／cm并且在被检表量程范围内的标准溶液。将标准溶液恒温至25℃±2℃，将被检表的电导电极置入标准溶液之中，待温度稳定后记录标准溶液的电导率值(κb)，精确读取被检表的示值(κJ)及溶液的温度值。检验数据的记录格式见附录C中的表C.2。
整机引用误差计算方法见式(2)。
(2)
式中：
δZ——整机引用误差，％；
κJ——被检表电导率示值，μS／cm；
κb——标准溶液电导率，μS／cm，标准溶液在基准温度(25℃)时的电导率值可根据所配制的氯化钾标准溶液由附录B中的表B.1查出；
M——量程范围内最大值，μS／cm。
注：电极常数等于或小于0.1cm－1级别的电极应根据5.4.2检验整机工作误差。
5.5 二次仪表检验
5.5.1 引用误差检验
5.5.1.1 检验原则
对于测量电导率值大于0.30μS／cm的电导率表，应采用标准交流电阻箱(见图3)作为电导率标准输入信号进行检验。对于测量电导率值不大于0.3μS／cm的电导率表，应采用模拟电路(见图4)作为电导率标准信号进行检验。
5.5.1.2 检验方法
用准确度等级优于0.1级的标准交流电阻箱和标准直流电阻箱，分别模拟溶液等效电阻RX和温度电阻Rt，作为检验的模拟信号。调节模拟温度电阻Rt，使仪表显示的温度为25℃。将被检表的电导池常数设为0.01(或0.1)。被检表与标准交流电阻之间连接如图3所示，对于测量电导率值不大于0.30μS／cm的电导率表，用图4的模拟电路取代图3中的交流电阻箱RX，其中RX为标准交流电阻箱。
电导率仪表
图3 被检表与标准电阻箱之间的连接
图4 纯水电导率表二次仪表检验模拟电路
被检表测量值稳定后，再根据式(3)的计算结果向二次仪表输入模拟等效电阻信号。
(3)
式中：
RX——等效电阻，Ω；
J——被检表设定的电导池常数，cm－1；
κL——理论电导率，μS／cm。
记录被检表电导率示值κS，二次仪表引用误差的计算方法见式(4)。检验数据的记录格式见附录C中的表C.3。
(4)
式中：
δY——二次仪表引用误差，％；
κS——被检表电导率示值，μS／cm；
κL——理论电导率，μS／cm；
M——量程范围内最大值，μS／cm。
5.5.2 二次仪表温度补偿附加误差检验
用准确度等级优于0.1级的标准交流电阻箱和标准直流电阻箱，分别模拟溶液等效电阻RX和温度电阻Rt，作为检验的模拟信号，按图3连接。
根据被检表说明书，对仪表温度补偿进行正确设置。例如，测量混床出水(除盐水等)水样直接电导率选择纯水或超纯水非线性补偿方式，测量氢型阳离子交换柱出水水样氢电导率选择针对酸性水样的非线性补偿方式，测量加氨水样直接电导率选择针对加氨水样的非线性补偿方式，测量普通水样电导率选择线性补偿2％。测量不同类型水样的在线电导率表二次仪表温度补偿附加误差检验按如下步骤进行：
a)测量混床出水水样。将被检表的电极常数设为0.01cm－1。调节模拟温度电阻Rt，使仪表显示的温度为25℃，然后按式(3)调节溶液等效电阻RX为100000Ω，使仪表显示电导率为0.1μS／cm，记录仪表示值κt1。调节模拟温度电阻Rt，使仪表显示的温度为35℃，按式(5)计算出溶液等效电阻RX为69930Ω，调节RX为69930Ω，记录仪表示值κt2值。
b)测量氢型阳离子交换柱出水水样。将被检表的电极常数设为0.01cm－1。调节模拟温度电阻Rt，使仪表显示的温度为25℃，然后按式(3)调节溶液等效电阻RX为100000Ω，使仪表显示电导率为0.1μS／cm，记录仪表示值κt1。调节模拟温度电阻Rt，使仪表显示的温度为35℃，按式(5)计算出溶液等效电阻RX为72464Ω，调节RX为72464Ω，记录仪表示值κt2值。
c)测量加氨水样。将被检表的电极常数设为0.1cm－1。调节模拟温度电阻Rt，使仪表显示的温度为25℃，然后按式(3)调节溶液等效电阻RX为33333Ω，使仪表显示电导率为3μS／cm，记录仪表示值κt1。调节模拟温度电阻Rt，使仪表显示的温度为35℃，按式(5)计算出溶液等效电阻RX为28490Ω，调节RX为28490Ω，记录仪表示值κt2值。
d)测量普通水样。将被检表的电极常数设为1cm－1。调节模拟温度电阻Rt，使仪表显示的温度为25℃，然后按式(3)调节溶液等效电阻RX为2000Ω，使仪表显示电导率为500μS／cm，记录仪表示值κt1值。调节模拟温度电阻Rt，使仪表显示的温度为35℃，按式(5)计算出溶液等效电阻RX为1667Ω，调节RX为1667Ω，记录仪表示值κt2值。
(5)
式中：
RX——温度为t时的溶液等效电阻值，Ω；
J——被检表设定的电极常数，cm－1；
κ——25℃时的理论电导率值，μS／cm；
β——溶液的温度系数。
注：不同水样的温度系数按照以下方式取值：测量混床出水水样在线电导率表，25℃的电导率值为0.1μS／cm，在35℃时，β取0.043；测量氢型阳离子交换柱出水水样在线氢电导率表，25℃的电导率值为0.1μS／cm，在35℃时，β取0.038；测量加氨水样在线电导率表，25℃的电导率值为3μS／cm，在35℃时，β取0.017；测量普通水样在线电导率表，25℃的电导率值为500μS／cm，在35℃时，β取0.02。
二次仪表的温度补偿附加误差的计算方法见式(6)。检验的记录格式见附录C中的表C.4。
(6)
式中：
δt——二次仪表温度补偿附加误差，×10－3℃－1；
κt1——25℃时被检表电导率示值，μS／cm；
κt2——35℃时被检表电导率示值，μS／cm；
M——量程范围内最大值，μS／cm。
5.6 电极常数检验
5.6.1 检验原则
对于电极常数小于0.1cm－1的电极，应采用标准电极法进行检验。对于电极常数大于或等于0.1cm－1的电极，宜采用标准电极法进行检验，也可采用静态标准溶液离线检验法检验。
5.6.2 标准电极法
按图1将标准电导池(电极常数为JB)就近与被检电导池并联或串联连接，水样的电导率在被检电导池正常测量水样的电导率范围内，保持水样的电导率在检验期间不变(如果水样电导率不稳定，则使用5.3.7要求的装置产生电导率稳定的水样)。设置标准电导率表和被检电导率表的温度补偿方式为不补偿，待仪表测量值稳定后，记录标准电导率表测量值κb和被检电导率表测量值κX。被检电极常数的计算方法见式(7)。记录格式见附录C中的表C.5。
(7)
式中：
JX——被检电极常数，cm－1；
κb——标准电导率表测量值，μS／cm；
κX——被检电导率表测量值，μS／cm；
JB——标准电极的电极常数，cm－1。
5.6.3 静态标准溶液离线检验法
选用电导率大于100μS／cm的标准溶液，所选用的标准溶液应当在溶液的等效电阻为5×102Ω～1×104Ω之间选择。
将被检电极置入已知标准电导率值的标准溶液中(恒温25℃±2℃)。将被检电导率表的电极常数设为1，测量溶液的电导G。
电极常数的计算方法见式(8)。记录格式见附录C中的表C.5。
(8)
式中：
JX——被检电极常数，cm－l；
κb——标准溶液电导率，μS／cm；
G——被检电导率表测量的电导，μS。
5.6.4 电极常数误差计算方法
计算方法见式(9)。记录格式见附录C中的表C.5。
(9)
式中：
δD——电极常数误差，％；
JX——被检电极常数，cm－1；
Jg——厂家给定(或本次标定前)的电极常数，cm－1。
5.7 交换柱附加误差检验
5.7.1 检验方法
将标准电导池连接在标准氢交换柱出水中，用标准电导率表测量标准氢交换柱出水电导率κb；然后将标准电导池连接在被检在线氢交换柱出水中，用标准电导率表测量被检在线氢交换柱出水电导率κz。
5.7.2 交换柱附加误差计算方法
计算方法见式(10)。记录格式见附录C中的表C.6。
(10)
式中：
δJ——交换柱附加误差，％；
κz——在线氢交换柱出水电导率，μS／cm；
κb——标准氢交换柱出水电导率，μS／cm。
注1：交换柱附加误差检验时标准氢交换柱和在线氢交换柱应测量同一水样，并在检验期间保持稳定不变。
注2：在线氢电导率表采用的氢交换柱可采用其他形式的阳离子交换设备。
5.8 温度测量误差检验
将被检电导率表测量电极和标准温度计放入同一杯水溶液中，待被检表读数稳定后，同时读取被检表温度示值tX和标准温度计示值tB。温度测量误差按式(11)计算。记录格式见附录C中的表C.7。
t＝tX－tB (11)
式中：
t——温度测量误差，℃；
tX——被检表温度示值，℃；
tB——标准温度计示值，℃。
6 在线pH表
6.1 技术要求
6.1.1 在线pH表整机检验项目、技术要求和检验周期应符合表4的规定。
表4 在线pH表整机检验项目、技术要求和检验周期
项目 要求 检验周期
运行中 机组检修后 新购置
整机检验a 工作误差δG －0.05＜δG＜0.05 1次／1个月 √ √
示值误差δS －0.05＜δS＜0.05 1次／1个月 √ √
示值重复性S S＜0.03 根据需要b — √
温度补偿附加误差pHt
℃－1 －0.01＜pHt＜0.01 根据需要c — √
a 根据6.4.1整机检验原则进行工作误差或示值误差的检验。
b 当发现仪表读数不稳定时进行检验。
c 当发现仪表整机工作误差或整机示值误差超标时进行检验。
6.1.2 当整机检验结果不合格时，再进行表5项目的检验。
表5 在线pH表二次仪表及电极检验项目、技术要求与检验周期
项目 技术要求 检验周期
运行中 机组检修后 新购置
示值误差pH －0.03＜pH＜0.03 根据需要a — √
输入阻抗引起的示值误差pHR －0.01＜pHR＜0.01 根据需要a — √
温度测量误差t
℃ －0.5＜t＜0.5 根据需要a — √
参比电极检验 参比电极内阻kΩ ≤10 根据需要a — —
电极电位稳定性 在±2mV／8h之内 根据需要a — —
玻璃电极检验 玻璃电极内阻RNMΩ 5～20(低阻)；
100～250(高阻) 根据需要a — —
百分理论斜率PTS
％ ≥90 根据需要a — —
a 当发现仪表整机工作误差或整机示值误差超标时进行检验。
6.2 检验条件
在线pH表检验条件应符合表6的规定。
表6 在线pH表检验条件
检验条件 规范与要求
水样温度
℃ 5～50
水样流量 仪表制造厂要求的流量
6.3 检验设备与标准溶液
6.3.1 低电导率pH标准水样制备装置(参见附录D中的D.1)。
6.3.2 pH表检定仪，准确度等级不低于0.01级。
6.3.3 高阻开关，绝缘电阻优于1×1012Ω。
6.3.4 直流电阻箱，准确度等级优于0.1级。
6.3.5 pH标准缓冲溶液，优先选用国家计量标准物(配制pH标准溶液的方法见附录E)。
6.3.6 精度为±2℃、范围为室温至50℃的可调整恒温水浴。
6.3.7 精密温度计，测量范围为0℃～50℃，最小分度值为0.1℃。
6.3.8 标准pH表应同时满足以下要求：
a)pH测量示值误差小于0.02。
b)在线测量纯水pH值时不受静电荷、液接电位和地回路的影响。
c)具有消除温度变化引起的能斯特方程中的斜率变化、参比电极电位变化和溶液离子平衡常数变化引起的附加误差的性能。
6.4 整机误差检验
6.4.1 检验原则
对于测量水样电导率值不大于100μS／cm的在线pH表，应采用水样流动检验法进行整机工作误差的在线检验。对于测量水样电导率值大于100μS／cm的在线pH表，采用静态标准溶液离线检验法进行整机示值误差检验。
6.4.2 整机工作误差检验(水样流动检验法)
整机工作误差检验(水样流动检验法)可分为方法1和方法2，方法1用于检验测量给水、凝结水和蒸汽水样的pH表；方法2用于检验测量炉水、内冷水的pH表。
方法1：将在线表测量水样分别引入标准表传感器入口和在线表传感器入口，水样的流速按照要求调整至符合表5的规定条件，并保持相对稳定。待仪表示值稳定后，记录标准表示值BZ和被检表的示值Si。
方法2：利用流动标准水样制备装置产生标准水样，其电导率应在被检表运行期间所监测水样的电导率范围内。将标准水样接到标准pH表传感器入口，标准pH表传感器出口接入被检表的传感器。待仪表示值稳定后，记录标准表示值BZ和被检表的示值Si。
