GB 16248-1996 Hygienic standard for respirable coal dust in the air of workplaces
Some standard content:
GB16248-1996
This standard is developed by using a dust sampler with the characteristic of separating respirable dust particles to measure the concentration of respirable coal dust in the air of workplaces with different types of coal and coal mining methods in my country, and analyze the proportional relationship with the total coal dust concentration. This is the first time that my country has proposed this standard.
This standard shall be implemented from September 1, 1996. Appendix A and Appendix B of this standard are both appendices to the standard. This standard is proposed by the Ministry of Health of the People's Republic of China. The drafting units of this standard are: Institute of Occupational Disease Prevention and Control of Kailuan Mining Bureau, Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine. The main drafters of this standard are: Zhang Guoxiang, Fu Shaochang, Huang Hehui, Cheng Yuhai, and Zhang Yuying. This standard is interpreted by the Institute of Labor Hygiene and Occupational Diseases, Chinese Academy of Preventive Medicine, which is the technical management unit entrusted by the Ministry of Health. 586
1 Scope
National Standard of the People's Republic of China
Health standard for respirable coal dust in the air of workplace
This standard specifies the maximum permissible concentration of respirable coal dust in the air of workplace and its monitoring and inspection methods. This standard is applicable to all types of coal dust workplaces where the free silica content in the air is less than 10%. 2 Referenced standards
GB 16248—1996
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and the parties using this standard should explore the possibility of using the latest versions of the following standards. GB5748—85 Determination of dust in the air of the workplace TJ36--79 Hygiene standard for industrial enterprise design 3 Definitions
This standard adopts the following definitions.
3.1 Coal dust
Coal dust with a free silicon dioxide content of less than 10% in the workplace air. 3.2 Respirable coal dust Respirable coal dust is coal dust with an aerodynamic diameter of less than 7.07μm in the workplace air, and a collection efficiency of 50% for 5μm particles. The respirable dust sampler should have the following characteristics for separating particles: p=1-
Where: P——permeability,
D—dust aerodynamic diameter, μm; D. --7. 07 μm.
4 Hygiene requirements
(D≤D.)www.bzxz.net
(D > D.)
The maximum allowable concentration of respirable coal dust with a free silicon dioxide content of less than 10% is 3.5mg/m2.5 Monitoring and inspection methods
For the determination of respirable coal dust concentration in the workplace, see Appendix A (Appendix to the standard). For the determination of free silicon dioxide content in respirable coal dust, see Appendix B (Appendix to the standard). Approved by the State Administration of Technical Supervision on April 3, 1996. (1)
Implementation on September 1, 1996
A1 Principle
GB16248--1996
Appendix A
(Appendix to the standard)
Method for determination of respirable coal dust concentration
A certain volume of dust-laden air is extracted. When passing through the sampling head, coarse dust particles impact on an impact plate coated with silicone oil (or adhesive) of known mass, while respirable dust is retained on a filter membrane of known mass. The mass concentration (mg/m\) of total coal dust and respirable coal dust per unit volume of air is calculated from the increase in dust on the impact plate and filter membrane after sampling. A2 Equipment
A2.1 Sampler: A respirable dust sampler that has passed the inspection of a unit designated or entrusted by the State Technical Supervision Bureau must be used. When sampling in a workplace with explosion-proof requirements, an explosion-proof dust sampler must be used. A2.2 Classification preselector (sampling head): This standard uses an impact sampling head with a sampling flow rate of 20L/min. The separation performance of the sampling head for dust particles should meet the performance requirements of this standard. The airtightness of the sampling head should meet the requirements of A2 in Appendix A (Supplement) of GB5748-85.
A2.3 Filter membrane: Perchloroethylene fiber filter membrane (dust measurement filter membrane), with a diameter of 40mmA2.4 Impact plate: Use a circular impact plate. A2.5 Gas flow meter: Use a 20L/min flow meter. The flow meter should be calibrated with a soap film flow meter or a bell-type gas flow meter every six months. If the flow meter is found to be obviously contaminated, it should be cleaned and calibrated in time. A2.6 Balance: Analytical balance with a sensitivity of 0.00001g, which shall be calibrated once a year according to the requirements of the metrology department. A2.7 Silicone oil: Methyl silicone oil with a viscosity of 60,000. A2.8 Timer: Stopwatch or timer equivalent to a stopwatch. A2.9 Dryer: Contains color-changing silica gel.
A3 Determination procedure
A3.1 Preparation of sampling head
A3.1.1 Clean the inner and outer walls of the sampling head and the impact plate with a neutral detergent. A3.1.2 Use a clean grease applicator or elbow tweezers to dip silicone oil and apply it from the center to the outer periphery of the impact plate. The diameter should not exceed 15mm. The amount of silicone oil applied to the impact plate should be 5mg to 8mg. The silicone oil on the impact plate will gradually spread evenly over time and needs to be left for more than 12 hours. At this time, dust pollution should be avoided.
A3.2 Weighing the impact plate
Use tweezers to pick up the impact plate coated with silicone oil, place it on a balance and weigh it to constant weight, record the initial mass, and place it in a numbered storage box for later use.
A3.3 Weighing the filter membrane
Use tweezers to remove the backing paper on both sides of the filter membrane, place it in the center of the balance pan and weigh it to constant weight, record the initial mass, then put the filter membrane into the filter membrane holder, and put it into a numbered sample box for later use. A3.4 Installation of the impact plate and filter membrane
Take out the weighed impact plate, with the oiled side facing up, carefully place it in the numbered sampling head, fix it, and then screw on the cover. Then take out the filter membrane holder, place it on the base of the sampling head, and tighten it tightly, and you are ready to go to the scene for sampling. A4 On-site sampling
A4.1 Setting up the sampler: At the sampling site, place the sampler on the bracket, install the sampling head on the sampler, and adjust it to the height of the operator's breathing belt. The air inlet of the sampling head should face the dusty airflow. If there is splashing coal slime, slag particles, etc. that may contaminate the sample during the production process, the air inlet of the sampling head can be sideways to the dusty airflow. A4.2 Time to start sampling: For continuous dust-generating work points, sampling should be started 30 minutes after the start of the operation. For discontinuous dust-generating work points, sampling should start when the workers are working.
A4.3 Sampling flow rate: During the entire sampling process, the flow rate should be constant and must be maintained at 20L/min. A4.4 The duration of sampling should be determined based on the estimated value of the dust concentration at the dust measurement point and the minimum value of the dust increment required on the filter membrane. Generally, it should not be less than 10 minutes. When the coal dust concentration is high, it can be sampled for 3 minutes to 5 minutes. A4.5 The dust increment collected on the impact plate and the filter membrane should not be less than 0.5 mg, but not more than 10 mg. A5 Processing of samples after sampling
A5.1 At the end of sampling, turn off the sampler switch and record the duration of sampling, sampling location, sample number, working conditions, etc. Then carefully remove the sampling head, cover it with a protective cover, gently put it in the sample box, and take it back to the laboratory for analysis. A5.2 Wipe the sampling head clean, carefully remove the impact plate and filter membrane. Under normal circumstances, there is no need for drying treatment, and it can be directly placed on the balance for weighing and recording its mass.
A5.3 When the relative humidity at the sampling site is above 90%, the impact plate and filter membrane should be placed in a dryer to dry for 2 hours, then weighed and their mass recorded. Then, they should be placed in a dryer to dry for 30 minutes and weighed again. If there are droplets on the filter membrane, they should be placed in a dryer first, weighed and their mass recorded after 12 hours, then placed in a dryer again and weighed again after 2 hours. When the difference between two adjacent masses does not exceed 0.01 mg, the minimum value should be taken.
A6 Calculation of coal dust concentration
A6.1 The respirable coal dust concentration is calculated according to formula (A1): R=m2_mi
×1000
The total dust concentration is calculated according to formula (A2):
(G, - G)±(m2 m) × 1 000
Wherein: R
-respirable coal dust concentration, mg/m3;
The mass of the filter membrane before sampling, mg;
The mass of the filter membrane after sampling, mg;
Total coal dust concentration, mg/m3;
The mass of the impact plate before sampling, mg;
G,-The mass of the impact plate after sampling, mg, Q-Sampling flow rate, 20L/min;
t Sampling time,min.
A7 Explanation
(Al)
This method is the basic method for determining the concentration of respirable coal dust. If other instruments or methods are used to determine the concentration of respirable coal dust, the sampling performance of the respirable coal dust must meet the requirements of this standard. 589
B1 Principle
GB 16248-1996
Appendix B
(Subject Appendix)
Determination of free silicon dioxide content in respirable coal dust by infrared spectrometry The most common material in industrial dust is α-quartz. In the infrared spectrum, α-quartz has specific strong absorption bands at 12.5 (800cm-1), 12.8 (780cm=1) and 14.4 (694cm=1)μm. Within a certain range, its absorbance value is linearly related to the mass of α-quartz. B2 Equipment and Reagents
B2.1 Equipment
a) Infrared spectrophotometer;
b) Tablet press and tablet mold;
c) Analytical balance with a sensitivity of 0.00001g or 0.000001g;
e) Drying oven and dryer;
f) Agate mortar,
g) 200-mesh dust sieve;
h) Porcelain crucible;
i) Crucible tongs.
B2.2 Reagents
a) Standard α-quartz dust, purity above 99%, particle size less than 5μm. b) Potassium bromide, high-grade pure or spectral pure, after passing through a 200-mesh sieve, grind by wet method, dry at 150℃, and store in a desiccator for use. c) Anhydrous ethanol, analytical grade.
B3 Dust sample collection and treatment
B3.1 Sampling
Respirable coal dust shall be sampled in accordance with the provisions of Appendix A. B3.2 Sample treatment
B3.2.1 After dust collection, the dust-receiving surface of the filter membrane is folded inward three times and placed in a porcelain crucible, and then placed in a low-temperature ashing furnace or a resistance furnace (less than 600°C) for ashing, cooled, and placed in a dryer for standby use. Weigh 250 mg of potassium bromide and the ashed dust sample together, put them into an agate mortar, grind and mix them, and then put them into a drying oven (110 ± 5°C) together with the tableting mold for 10 minutes. Place the dried mixed sample in the tableting mold, pressurize it to 25MPa for 3 minutes, and the prepared ingot is used as the test sample. B3.2.2 Take a blank filter membrane, put it into a porcelain crucible for ash treatment, and then put it into an agate mortar together with 250 mg of potassium bromide for grinding and mixing. Press the tablets according to the above method, and the prepared tablets are used as reference samples. "B4 Sample determination
B4.1 Test conditions: According to the performance of various types of infrared spectrophotometers, record the spectrum from 900 to 600 cm-1 on the X-axis, calibrate the zero point and 100% at 900 cm-1, and express the absorbance value on the Y-axis.
B4.2 Place the determination sample tablet and the reference sample tablet in the light path of the sample chamber for scanning, record the absorbance value at 800 cm-, subtract the absorbance value of the reference sample from the absorbance value of the determination sample, check the α-quartz standard curve, and calculate the free silica in coal dust 590
B5 Preparation of α-quartz standard curve
GB 16248-1996
B5.1 Accurately weigh different doses of standard quartz dust (10μg~1000μg), add 250mg of potassium bromide to each, place in an agate mortar and grind thoroughly until homogeneous, and make transparent ingots according to the above sample preparation method. B5.2 The analytical conditions for preparing quartz standard curve samples should be completely consistent with the conditions of the measured samples. B5.3 Place different doses of standard quartz ingots in the sample chamber light path for scanning at 800cm-1, 780cm-1 and 694cm- 1 The absorbance values at three locations are taken as the ordinate, and the quartz mass is taken as the abscissa. Three α-quartz standard curves of different wavelengths are drawn, and the regression equation of the standard curve is obtained. In the absence of interference, the 800cm-1 standard curve is generally selected for quantitative analysis. B6 Calculation of free silica content in dust According to the average absorbance value of the dust samples measured three times, the mass of free silica (mg) is obtained by checking the quartz standard curve. The free silica α-quartz content in the dust is calculated according to formula (B1). SiO2(F)(%) =
#×100
Wherein: SiO2(F)——the content of free silicon dioxide (α-quartz) in dust, %; m-the mass of free silicon dioxide measured in dust sample, mg; G——the mass of dust sample, mg.
B7 Notes
. (B1)
B7.1 The minimum detection amount of α-quartz in this method is 10μg, the average recovery rate is 96.0%~~99.8%, and the accuracy (CV) is 0.64%~1.41%.
B7.2 The particle size of dust has a certain influence on the measurement results. Therefore, the quartz dust used to make the standard curve should be fully ground so that its dispersion is less than Only when the 5um content is more than 95%, can the analysis and determination be carried out. B7.3 The ash temperature of the coal dust sample has a certain influence on the quantitative result. If there are a large amount of kaolin components in the coal dust sample, it will decompose when ash is higher than 600℃, and produce interference near 800cm-1. If the ash temperature is less than 600℃, this interference band can be eliminated. B7.4 If the dust contains clay, mica, amphibole, feldspar and other components, it may produce interference near 800cm-1. The standard curve of 694cm-1 can be used for quantitative analysis.
B7.5 In order to reduce the random error of measurement, the laboratory temperature should be controlled at 18℃~~24℃, and the relative humidity should be less than 50%. 5911 Accurately weigh different doses of standard quartz dust (10μg～1000μg), add 250mg potassium bromide respectively, put them in an agate mortar and grind them thoroughly, and make transparent ingots according to the above sample preparation method. B5.2 The analytical conditions for preparing the quartz standard curve sample should be exactly the same as those of the sample to be tested. B5.3 Place different doses of standard quartz ingots in the light path of the sample chamber for scanning, and use the absorbance values at 800cm-1, 780cm-1 and 694cm-1 as the vertical coordinates, and the quartz mass as the horizontal coordinates to draw three α-quartz standard curves of different wavelengths, and calculate the regression equation of the standard curve. In the absence of interference, the 800cm-1 standard curve is generally used for quantitative analysis. B6 Calculation of free silica content in dust According to the average absorbance value of the dust sample measured three times, check the quartz standard curve to calculate the free silica mass (mg). Calculate the free silica α-quartz content in dust according to formula (B1). SiO2(F)(%) =
#×100
Wherein: SiO2(F)——free silicon dioxide (α-quartz) content in dust, %; m-mass of free silicon dioxide measured in dust sample, mg; G——mass of dust sample, mg.
B7 Notes
. (B1)
B7.1 The minimum detection amount of α-quartz in this method is 10μg, the average recovery rate is 96.0%~~99.8%, and the accuracy (CV) is 0.64%~1.41%.
B7.2 The dust particle size has a certain influence on the determination result. Therefore, the quartz dust used to make the standard curve should be fully ground so that the dispersion of less than 5um accounts for more than 95% before analysis and determination can be carried out. B7.3 The ash temperature of coal dust samples has a certain influence on the quantitative results. If there are a large amount of kaolin components in the coal dust sample, it will decompose when ash temperature is higher than 600℃, causing interference near 800cm-1. If the ash temperature is lower than 600℃, this interference band can be eliminated. B7.4 If the dust contains clay, mica, amphibole, feldspar and other components, interference may occur near 800cm-1. The standard curve of 694cm-1 can be used for quantitative analysis.
B7.5 In order to reduce the random error of measurement, the laboratory temperature should be controlled at 18℃~~24℃, and the relative humidity should be less than 50%. 5911 Accurately weigh different doses of standard quartz dust (10μg～1000μg), add 250mg potassium bromide respectively, put them in an agate mortar and grind them thoroughly, and make transparent ingots according to the above sample preparation method. B5.2 The analytical conditions for preparing the quartz standard curve sample should be exactly the same as those of the sample to be tested. B5.3 Place different doses of standard quartz ingots in the light path of the sample chamber for scanning, and use the absorbance values at 800cm-1, 780cm-1 and 694cm-1 as the vertical coordinates, and the quartz mass as the horizontal coordinates to draw three α-quartz standard curves of different wavelengths, and calculate the regression equation of the standard curve. In the absence of interference, the 800cm-1 standard curve is generally used for quantitative analysis. B6 Calculation of free silica content in dust According to the average absorbance value of the dust sample measured three times, check the quartz standard curve to calculate the free silica mass (mg). Calculate the free silica α-quartz content in dust according to formula (B1). SiO2(F)(%) =
#×100
Wherein: SiO2(F)——free silicon dioxide (α-quartz) content in dust, %; m-mass of free silicon dioxide measured in dust sample, mg; G——mass of dust sample, mg.
B7 Notes
. (B1)
B7.1 The minimum detection amount of α-quartz in this method is 10μg, the average recovery rate is 96.0%~~99.8%, and the accuracy (CV) is 0.64%~1.41%.
B7.2 The dust particle size has a certain influence on the determination result. Therefore, the quartz dust used to make the standard curve should be fully ground so that the dispersion of less than 5um accounts for more than 95% before analysis and determination can be carried out. B7.3 The ash temperature of coal dust samples has a certain influence on the quantitative results. If there are a large amount of kaolin components in the coal dust sample, it will decompose when ash temperature is higher than 600℃, causing interference near 800cm-1. If the ash temperature is lower than 600℃, this interference band can be eliminated. B7.4 If the dust contains clay, mica, amphibole, feldspar and other components, interference may occur near 800cm-1. The standard curve of 694cm-1 can be used for quantitative analysis.
B7.5 In order to reduce the random error of measurement, the laboratory temperature should be controlled at 18℃~~24℃, and the relative humidity should be less than 50%. 591
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.