Some standard content:
GB/T4200
--1997
《High Temperature Work Classification》standard is a unique labor safety and health classification management standard in my country, which is applicable to the evaluation and classification of heat intensity and grade of high temperature work environment. When revising this standard, the internationally accepted WBGT index method was adopted to replace the temperature difference evaluation method used in my country's GB1200--84 standard. At the same time, the new revised standard adds a correction factor for directional radiation heat. This standard shall be implemented from October 1, 1997. From the date of entry into force, this standard shall also replace GB4200-84. Appendices A, B and C of this standard are all appendices of the standard. This standard was proposed by the Ministry of Labor of the People's Republic of China. The drafting unit of this standard: Institute of Labor Health and Occupational Diseases, Chinese Academy of Preventive Medicine. The main drafters of this standard: Huang Haichao, Wei Yida, Fu Hong, Gan Yongxiang, Dai Zizhu, Li Tianlin. 1 ScopewwW.bzxz.Net
National Standard of the People's Republic of China
Classified standard of working in the hot environment
Classified standard of working in the hot environment This standard specifies the classification of heat intensity in the hot working environment. This standard is applicable to the implementation of labor safety and health classification management for hot working. 2 Definitions
This standard adopts the following definitions,
2.1 Productive heat sourceproductive hot sourceProduction equipment, products or workpieces that can generate and dissipate heat during the production process. 2.2 Workplacework-place
GB/T 4200--1997
Replaces GB4200-84
The place where workers need to stay frequently or regularly to perform production operations or observe production conditions. If workers need to operate at different locations in the workshop due to production labor needs, the entire workshop can be called a workplace. 2.3 WBGT-index WBGT-index
WBGT-index is also called wet bulb globe temperature (), which is an empirical index indicating the heat intensity of human contact in the production environment. It uses three parameters: natural wet bulb temperature (tnw), globe temperature (t) and dry bulb temperature (ta), and is calculated using the following formula. Indoor work:
WBGT == 0. 7 tnw + 0.3 t
Outdoor work:
WBGT = 0. 7 tnw + 0. 2 tu + 0. 1 ta2.4 The work in the environment with high temperature During the production labor process, the work at the workplace with an average WBGT index equal to or greater than 25°C. 2.5 Working time exposed in the environment with high temperature The cumulative time (min) that workers actually contact high temperature work in one working day (8h). 2.6 Radiant heat of fixed direction Heat radiated from a productive heat source in a certain direction at the workplace. 3 Classification of hot work
Hot work is divided into four levels according to the WBGT index of the workplace and the time of exposure to hot work. The higher the level, the greater the heat intensity, see Table 1.
Approved by the State Bureau of Technical Supervision on March 14, 1997, implementation of 199710-01
Exposure to high temperature
Working time
121~240
241~360
Correction coefficient of directional radiant heat
GB/T4200-1997
High temperature work classification
WBGT index, C
31~32
For any high temperature work where the average directional radiant heat intensity at the workplace is equal to or greater than 2kW/m2, the level should be increased accordingly on the basis of Chapter 3 of this standard, but the maximum shall not exceed Level V. 78
A1 Measurement time
GB/T 4200-1997
Appendix A
(Appendix to the standard)
WBGT index measurement and calculation method
For workers who are exposed to high temperature all year round, the measurement value in the hottest season should be used as the basis for classification. For workers who are exposed to high temperature seasonally or irregularly, the measurement value in the hottest month of the season should be used as the basis for classification. For workers who are engaged in outdoor work, the measurement value on a sunny day with solar radiation in the hottest month of summer should be used as the basis for classification. When production is normal and the heat source at the workplace is stable, the same workplace should be measured three times in one working month, that is, after work: 9:00~10:00; 13:00~~14:00; and 16:00~~17:00, for three consecutive days, and the average value is taken. In case of special production processes and unstable heat sources at the workplace, measurements can be made at any time according to the production process or specific conditions, and the same measuring point can be measured three times in a row, and the average value is taken. A2 Measurement location and position
Choose a place where workers often operate, stay or take a temporary rest. The general measurement height is 1.5m for standing work and 1.1m for sitting work. If the actual heating of workers is uneven, the ankles, abdomen and head should be measured. When standing, the measurement points are 0.1, 1.1 and 1.7m above the ground; when sitting, the measurement points are 0.1, 0.6 and 1.1m above the ground. A3 The average value calculation formula of WBGT index
WBGT =WBGT*+(2 × WBGT)+WBGTm4
A4 Measuring instruments and methods
A4.1 The measuring instrument is a WBGT measuring instrument, or a dry-bulb thermometer, a natural wet-bulb thermometer, or a black-globe thermometer, and the measurements and calculations are made at various locations.
A4.2 The temperature sensing part of the natural wet-bulb thermometer should be a cylinder with an outer diameter of 6mm ± 1mm, a length of 30mm ± 5mm, a measuring range of 5 to 40℃, and an accuracy of ±0.5℃.
A4.3 The diameter of the black ball of the black ball thermometer is 150mm, and it is a matte black ball with an average radiation coefficient of 0.95. The thinner the copper ball wall, the better. The measuring range is 20 to 120℃, and the accuracy is ±1℃. A4.4 The measuring range of the dry-bulb thermometer is 10 to 60℃, and the accuracy is ±0.5℃. When measuring, care should be taken to prevent the influence of radiant heat. A4.5 When measuring the dry-bulb, wet-bulb and black-bulb temperatures, a tripod bracket should be used to suspend the three thermometers so that the ambient air can flow through the temperature sensing part of the sphere without restriction.
A4.6 When measuring the wet bulb temperature, wrap a layer of wet gauze strips on the temperature-sensitive part of the wet bulb thermometer. The gauze strips should cover the entire temperature-sensitive sphere of the wet bulb thermometer. When measuring, let it evaporate naturally (do not force ventilation artificially) and read the measured value every 30 minutes. Care should be taken to keep the gauze strips clean and moist, and wash them before using them again. A4.7 It takes a long time for the black globe thermometer to reach a stable state, so the black globe temperature is generally read and recorded every 25 minutes. A5 Time-weighted WBGT index calculation formula
In workplaces where the heat intensity of the production environment varies greatly, or when the workers operate at different work locations in the workshop due to production needs: When the contact heat intensity is inconsistent, the time-weighted average formula should be used to calculate the WBGT index: (WBGT)t + (WBGT,)2 + ... +(WBGTWBGT =
t,+t2+... + t.
WBGT,-——WBGT measured at the first work location, C,.+---..( A2 )
GB/T 4200
WBGT WBGT measured at the second work location, C; WBGT.—.WBGT measured at the nth work location, C; t++t?++++++t, --
Operators in 1.2..…n actual stay time at each work location, min. Appendix B
(Standard Appendix)
Measurement and calculation of exposure time to high temperature work
B1 Exposure time to high temperature work refers to the cumulative time (min) that workers actually operate, stay and take short breaks in a hot environment due to production needs in one working day (8h).
B2 The measurement method is to randomly select 23 workers to be tested from the same type of work or production position. Under normal production conditions, the shift records the actual exposure time of workers at each work position to high temperature work for three consecutive days and take the average value. B3 If workers need to work in different positions within one working day, the actual exposure time to high temperature work in each position should be measured separately, and the WBGT index of their position I work location should be measured at the same time, so as to calculate the time-weighted average WBGT index according to A5 in Appendix A. Appendix C
(Standard Appendix)
Measurement and calculation method of directional radiation heat
C1 For the measurement time, location and position of directional radiation heat, please refer to the method principles specified in A1, A2 and A5 in Appendix A of this standard. C2 The measuring instrument uses a directional radiation heat meter to measure in the direction to be measured.
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