Standard No.:	DL/T 677-2018
English Name:	Inspection code of on-line chemical instruments for power plant
Chinese Name:	发电厂在线化学仪表检验规程
Professional Classification:	DL    Professional Standard - Electricity
Issued by:	NEA
Issued on:	2018-4-3
Implemented on:	2018-7-1
Status:	valid
Superseding:	DL/T 677-2009 Checking and calibration code for on-line chemical monitoring instrument of power plant
Language:	English
File Format:	PDF
Word Count:	30000 words
Price(USD):	850.0
Delivery:	via email in 1 business day

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