Piping and Valves Knowledge: [Question of the Day] 2011-02-09
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This post was last edited by security on 2011-2-10 08:57. Question: What is the basis for classifying the toxicity hazard level of media in pressure pipelines? 1) There must be a reward for participants ； :):victory: 2) Please hide your replies; the method for doing this is: http://bbs.hcbbs.com/thread-492556-1-1.html. Do not edit the replies after posting them. Answer ①: “Acute toxicity” refers to the harm to the human body caused by a large-scale leakage of fluid in an accident situation ； ②“The “maximum allowable concentration” takes into account the potential harm to human health that can occur under normal operating conditions of the piping system, as a result of sealing leaks (such as valve packings or flange gaskets) or sampling and discharge operations ； ③If the degree of toxicity hazard of a medium, as determined by four criteria—acute poisoning symptoms, chronic poisoning conditions, consequences of chronic poisoning, and carcinogenicity—is significantly higher than the level of hazard determined based on acute toxicity or the maximum allowable concentration, then it is necessary to conduct a comprehensive analysis taking into account the specific operating conditions of the pressure pipeline, and to appropriately raise the level of toxicity hazard associated with that medium. See GB/T 20801-2006 \"Code for pressure pipelines – Industrial pipelines\", Implementation Guide, P22
Reply 1#: The security classification should be based primarily on two criteria: acute toxicity and the maximum allowable concentration; the classification shall be determined according to the criterion with the higher level of toxicological hazard
This post was last edited by loeyshek on 2011-2-9 at 21:46. The classification of the toxicity level of substances in pressure pipelines should comply with the standards specified in GB5044 \"Classification of Hazards from Occupational Exposure to Toxic Substances\", which uses six criteria as the basis for such classification: acute toxicity, incidence of acute poisoning, incidence of chronic poisoning, consequences of chronic poisoning, carcinogenicity, and the maximum allowable concentration.
The classification of the toxicity level of the medium in pressure pipelines shall comply with the provisions of GB5044 \"Classification of Hazards from Occupational Exposure to Toxic Substances\". The classification criteria are based on six indicators, namely acute toxicity, incidence of acute poisoning, incidence of chronic poisoning, consequences of chronic poisoning, carcinogenicity, and the maximum allowable concentration, as shown in Table A-1； Table A-1 Criteria for classifying the degree of toxicity hazards of substances
Indicators | Classification
I (Extremely hazardous) | II (Highly hazardous) | III (Moderately hazardous)
Acute toxicity
Inhalation (LC50, mg/m³) | <200 | 200–<2000 | 2000–≤20000
Dermal (LD50, mg/kg) | <100 | 100–<500 | 500–≤2500
Oral (LD50, mg/kg) | <25 | 25–<500 | 500–≤5000
Incidence of acute poisoning | Poisoning frequently occurs during production; consequences are severe | Poisoning may occur during production; prognosis is good | Poisoning occurs occasionally
Prevalence of chronic poisoning | High prevalence rate (≥5%) | Relatively high prevalence rate (<5%) or high incidence of symptoms (≥20%) | Occasional cases of poisoning or relatively high incidence of symptoms (≥10%)
Consequences of chronic poisoning | Continued progression or incurability after exposure ceases | Generally curable after exposure ceases | Recovery is possible after exposure ceases; no serious consequences result
Carcinogenicity | Human carcinogen | Suspected human carcinogen | Carcinogen in experimental animals
Maximum allowable concentration (mg/m³) | <0.1 | 0.1–<1.0 | 1.0–≤10
Indicators | Classification
I (Extremely hazardous) | II (Highly hazardous) | III (Moderately hazardous)
Acute toxicity
Inhalation (LC50, mg/m³) | <200 | 200–<2000 | 2000–≤20000
Dermal (LD50, mg/kg) | <100 | 100–<500 | 500–≤2500
Oral (LD50, mg/kg) | <25 | 25–<500 | 500–≤5000
Incidence of acute poisoning | Poisoning frequently occurs during production; consequences are severe | Poisoning may occur during production; prognosis is good | Poisoning occurs occasionally
Prevalence of chronic poisoning | High prevalence rate (≥5%) | Relatively high prevalence rate (<5%) or high incidence of symptoms (≥20%) | Occasional cases of poisoning or relatively high incidence of symptoms (≥10%)
Consequences of chronic poisoning | Continued progression or incurability after exposure ceases | Generally curable after exposure ceases | Recovery is possible after exposure ceases; no serious consequences result
Carcinogenicity | Human carcinogen | Suspected human carcinogen | Carcinogen in experimental animals
Maximum allowable concentration (mg/m³) | <0.1 | 0.1–<1.0 | 1.0–≤10
Criteria for classification: 1. Acute toxicity – Based on the data obtained from animal tests regarding the median lethal concentration (LC50) upon inhalation through the respiratory tract, or the median lethal dose (LD50) via oral or dermal exposure; the lowest value among LC50 and LD50 is used as the indicator of acute toxicity. 2 The incidence of acute poisoning is a qualitative indicator based on the prevalence of acute poisoning and its consequences ； It can be divided into four categories: prone to poisoning, susceptible to poisoning, occasionally poisoned, and no acute poisoning. Designating conditions that can lead to fatal poisoning or disability as severe consequences of poisoning ； A good prognosis is indicated for those who recover easily. 3 Prevalence of chronic poisoning is generally based on the incidence of poisoning among workers in industries where contact with toxic substances occurs ； However, in the absence of prevalence data, the incidence of toxic symptoms or toxicological markers can be used. 4 Consequences of chronic poisoning: Based on the outcome of chronic poisoning, it is classified into four categories: continued progression or inability to be cured after discontinuing exposure, near-complete recovery, and spontaneous recovery. The consequences of chronic poisoning can be determined based on the nature of the damaged lesions as observed in animal experiments (progressive, irreversible, reversible), as well as the pathophysiological characteristics of the target organs (repair capacity, regenerative capacity, functional reserve). 5 Carcinogenicity: Based primarily on data on the carcinogenicity of this toxin published by the International Agency for Research on Cancer or other recognized sources, it is classified as a human carcinogen, a suspected human carcinogen, an animal carcinogen, or non-carcinogenic. 6 Maximum allowable concentration: It is mainly based on the maximum allowable concentrations of hazardous substances in workshop air listed in Table 4 of TJ 36—79, \"Hygienic Standards for Industrial Enterprise Design\". 7 The criteria for classifying the degree of hazard associated with occupational exposure to toxins are shown in Table 1; these classifications include extremely hazardous, highly hazardous, moderately hazardous, and mildly hazardous. Table 1: Criteria for classifying the degree of hazard associated with occupational exposure to toxins. Criteria | Classification: I (Extremely hazardous) | II (Highly hazardous) | III (Moderately hazardous) | IV (Mildly hazardous) Acute poisoning: Inhalation LC50, mg/m3; Peroral LD50, mg/kg; Oral LD50, mg/kg – 5000. Incidence of acute poisoning: Poisoning is likely to occur during production, with serious consequences; Poisoning may occur during production, but the prognosis is good; Poisoning occurs occasionally; No cases of acute poisoning have been reported yet, but there are acute effects. Chronic poisoning: Incidence rate (≥5%); Relatively high incidence rate
When determining the category of pressure vessels, a classification should be made based on the severity of toxic hazards posed by the medium to human health under accident conditions. In other words, classification is carried out through comprehensive analysis using the two indicators of acute toxicity and the maximum allowable concentration, in combination with the classification of other indicators, after thorough consideration.
sh3059-2001
ASME B31.3 response 1# security
Reply 1# security: The classification of the toxicity level of media should comply with the provisions of GB5044 \"Classification of the Hazard Levels of Toxic Substances Exposed in the Workplace\". The classification criteria are based on six indicators, including acute toxicity, incidence of acute poisoning, incidence of chronic poisoning, consequences of chronic poisoning, carcinogenicity, and the maximum allowable concentration
They are classified according to design pressure, temperature, medium toxicity, and flammability