This standard specifies the structure, technical requirements, test methods, inspection rules and marking, packaging, transportation and storage of nitrogen oxide (including nitrogen monoxide and nitrogen dioxide) detection tubes. This standard applies to the longer nitrogen oxide detection tubes (hereinafter referred to as detection tubes). MT 272-1994 Nitrogen oxide detection tube MT272-1994 Standard download decompression password: www.bzxz.net

Coal Industry Standard of the People's Republic of China
Nitrogen Oxide Detector Tube
Subject Content and Scope of Application
MT 272-94
This standard specifies the structure, technical requirements, test methods, inspection rules and marking, packaging, transportation and storage of nitrogen oxide (including nitrogen monoxide and nitrogen dioxide) detector tubes.
This standard applies to the comparative length nitrogen oxide detector tube (hereinafter referred to as the detector tube). 2 Reference standards
GB7230
GB 10111
3 Structure
Gas detection tube device
Random sampling method using random numbers 3.1 The structure of the detection tube is shown in Figure 1
Figure 1 Schematic diagram of nitrogen oxide detection tube
1-tube tip; 2-starting end lining plug; 3-isolation layer 4-indicator powder; 5-glass tube; 6-lining plug 3.2 The measurement range of the detection tube is 1~50ppm, and the minimum graduation value should comply with the provisions of Table 1: Table 1
Measuring range
1~10
>10~20
>20~50
Technical requirements
The interfaces of each layer of the detection tube filling should be neat. The graduation line of the detection tube should be clear and firm. 4.3
The length difference of each box of detection tubes should not exceed 5mm. 4.4
The distance between the liner plug at the start end of the test tube and the tip of the tube should not be less than 5mm. Minimum graduation value
4.5 The difference between the longest and shortest ends of the interface between the isolation layer and the indicator powder along the longitudinal direction of the tube wall should not exceed 1mm. Ministry of Energy of the People's Republic of China approved ppm on May 1, 1992
Implementation on October 1, 1994
MT 272-94
4.6 After the test, the difference between the longest and shortest ends of the interface between the discolored part and the undiscolored part of the indicator powder along the longitudinal direction of the tube wall should not exceed 20% of the average value of the two.
4.7 After the drop test, the filling of the test tube should be tight, and there should be no gap between the liner plug and the isolation layer. 4.8 The minimum detection concentration of the test tube is 1.0ppm. 4.9 The precision (CV) of the test tube is less than or equal to 10%. 4.10 The accuracy of the test tube at room temperature should meet the requirements of Table 2. Table 2
Accuracy, %
Test range, ppm
>17~50
4.11 The validity period of the test tube shall be no less than 1 year. Relative error of test value
4.12 The test tube must be used in conjunction with a special sampler that meets the requirements of Article 3.2 of GB7230. 5 Test method
5.14.1 and 4.2 are checked by sensory inspection.
5.24.3~4.6 are measured with a steel ruler with a graduation value of 0.5mm. Average relative error of the measured value
5.3 Drop test
Ten test tubes are randomly selected from the sample for drop test. During the test, the starting end of the test tube is bundled downward, and it is freely dropped 10 times from a height of 25mm to a 5mm thick rubber plate, and then its internal filling is inspected. 5.4. Minimum detection concentration test
Randomly select 10 test tubes from the sample, use the nitrogen dioxide standard gas sample with a concentration of 1.0±0.20ppm, and test it at room temperature according to the method specified in the instruction manual to check whether the color change is obvious. The uncertainty of the standard gas sample is ±3% (the same below). 5.5 Precision and accuracy test
Randomly select 20 test tubes from the sample, use the nitrogen dioxide standard gas sample specified in Table 3, and repeat the test 10 times for each concentration of standard gas sample at room temperature according to the method specified in the instruction manual. The measured value of the test tube is calculated according to formula (1): Lcenter
Where: X—measured value of the test tube, ppm; L—measured value of the color change length of the indicator powder, mm, C.—concentration of the test tube close to the graduation line of the standard gas sample concentration, ppm; L—length from the starting end of the graduation line of the test tube to the graduation line close to the concentration of the standard gas sample, mm. The precision of the test tube is calculated according to formula (2):
c. V. (%) =
Wherein:
Standard deviation;
X-average value of the test tube measurement value, ppm. The accuracy of the test tube is calculated according to formula (3) and formula (4): MT 272--94
Wherein: A, relative error of the measurement value, %; A2--relative error of the average value of the measurement value, %;-measurement value of the test tube, ppm;
-average value of the test tube measurement value, ppm; standard gas sample concentration, ppm.
Test range
>17～50
5.6 Test data processing
Standard gas sample concentration
5.6.1 When calculating the test tube measurement value, the significant figures are retained to 1 decimal place. 5.6.2 When calculating the precision and accuracy of the test tube, calculate to two decimal places and round to one decimal place. 6 Inspection rules
Products are divided into factory inspection and type inspection
6.1 Factory inspection
6.1.1 Products shall be inspected by the factory quality inspection department. They can only leave the factory after passing the inspection and issuing a certificate of conformity. 6.1.2 Each batch of products leaving the factory shall be subject to factory inspection. The factory inspection items include 4.1 to 4.10. 6.2 Type inspection
6.2.1 Type inspection shall be conducted in any of the following cases: a.
When a new product or old product is transferred to another factory for trial production and identification; after formal production, if there are major changes in structure, materials, and processes that may affect product performance; during normal production, an inspection shall be conducted once a year. After one year of suspension, when production is resumed,
when the factory inspection results are significantly different from the last type inspection, the national quality supervision agency proposes a type inspection requirement. 6.2.2 Type inspection items include 4.1 to 4.10. 6.3 Samplingwww.bzxz.net
(3)
(4)
6.3.1 Factory inspection sampling
150 pieces shall be sampled from the same batch of products that have been packaged into boxes and are ready to be shipped, in accordance with the method specified in GB10111, with each box as the unit. 6.3.2 Sampling for type inspection
150 tubes shall be sampled from the qualified products after factory inspection in accordance with the method specified in GB10111, in boxes. 6.3.3 Randomly select 3 boxes from the sample for inspection in 4.3; then randomly select 10 tubes from each box after mixing the test tubes for inspection in 4.1, 153
MT 272—94
4.2, 4.4, 4.5; randomly select 10 tubes for inspection in 4.7; randomly select 10 tubes for inspection in 4.8; randomly select 20 tubes for inspection in 4.9 and 4.10, and then use the test tubes used for testing higher concentration accuracy to test in 4.6. 6.4 Judgment rules
6.4.1 For 4.3, if 2 boxes fail to meet the requirements, it shall be judged as unqualified. 6.4.2 For 4.1, 4.2, 4.4, and 4.5, if 3 test tubes fail to meet the requirements, they will be judged as unqualified. 6.4.3 For 4.6 and 4.7, if 2 test tubes fail to meet the requirements, they will be judged as unqualified. 6.4.4 For 4.8, if 2 test tubes fail to meet the requirements, they will be judged as unqualified; if 1 test tube fails to meet the requirements, the number of test tubes should be doubled for re-testing. If the requirements are still not met, it will be judged as unqualified. 6.4.5 For 4.9, if the requirements are not met, it will be judged as unqualified. 6.4.6 For 4.10, if both items fail to meet the requirements, it will be judged as unqualified; if 1 item fails to meet the requirements, the number of test tubes should be doubled for re-testing. If the requirements are still not met, it will be judged as unqualified. 7 Marking, packaging, transportation, storage
7.1 Marking
.7.1.1 Product marking
The markings on each test tube shall include:
Measuring instrument marking;
Trademark;
Batch number.
Packaging marking
The markings on the test tube packaging box shall include: a.
Manufacturer's name;
Product name and model;
Quantity;
Trademark;
Batch number;
Validity period;
Manufacturing measuring instrument license number;
Instrument inspection certificate number;
Safety mark and its number.
The packaging box shall have "Fragile" and "Handle with care" markings. 7.2 Packaging
Test tubes should be packed in a hard box according to a certain quantity and fixed with soft objects. They should not shake. The box should be accompanied by the instruction manual and product certificate.
7.3 Transportation
Avoid dropping or smashing during shipment and ship as fragile items. 7.4 Storage
Test tubes should be stored in a room at room temperature and in a dry place, and strictly prevent sunlight exposure. .154
Additional Notes:
This standard was proposed by China Coal Research Institute. MT272—94
This standard is under the jurisdiction of Fushun Branch of China Coal Research Institute. This standard was jointly drafted by Fushun Branch of China Coal Research Institute and Hebi Mining Bureau. The main drafters of this standard are Yang Wenzheng, Chen Xingye and Ye Zhanying. This standard is entrusted to Fushun Branch of China Coal Research Institute for interpretation. 155
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