In order to determine the grade and technical requirements of the pressure vessels, the toxicity hazard of media and explosion risk extent are classified in this standard.
This standard is designed to classify the toxicity hazard and explosion hazard of chemical media used or stored in chemical pressure vessels (including raw material, finished product, semi-finished product, intermediate, byproduct and impurity), and determines hereby the grade and technical requirements of consistence, imperviousness of pressure vessels.
2 Normative Standards
GB 5044 C 85 Classifications of Health Hazard Levels from Occupational Exposure to Toxic Substances
State Bureau of Quality and Technical Supervision Pressure Vessel Safety Technology and Supervision Code (1999) (hereafter referred to PVSTSC as simply)
3. Classified criterions
3.0.1 The toxicity hazard and explosion risk extent of chemical media determined in this standard means the severity that media contact human body largely which caused by accident or chronic occupational hazards caused by gas leak frequently during the production run of pressure vessel. 3.0.2 The toxicity hazard extent of chemical media is classified base on the 6 classified indices stated in GB 5044. (Detailed in Appendix A --- Classified criteria of toxicity hazard extent).
It is divided into Extremely Hazardous, Highly Hazardous and Moderately Hazardous according to degree of toxicity hazard. (Note 1)
3.0.3 The toxicity hazard extent shall be classified according to the accidental state and hazard caused by the large contact between media and human body when it is use to determine grade of pressure vessels. Wherefore, the standard mainly focused on two indices of acute poisoning and maximum allowable concentration, and considered the ascription of indices, classified after and classified after general analysis and balances. The toxicity extents of Extremely Hazardous, Highly Hazardous and Moderately Hazardous of common chemical media are listed in Table 3.03-1 and 3.0.3-3.
3.0.4Not only the accidental state shall be based on, but also the chronicity potential hazard caused by recurrent leak shall be involved when technical requirements of consistence, imperviousness of chemical pressure vessels are determined. Wherefore, the standard mainly focused on three indices of acute poisoning, maximum allowable concentration and carcinogenicity, considered the ascription of indices, and classified after general analysis and balances. Certain media shall be classified according to one of its obvious hazard extents (such as carcinogenicity).Therefore, grade ascription of minority media listed in Table 3.0.3 - 1 and Table 3.0.3-3 are adjusted, details see the comments in tables.
3.0.5 Make the classification for media of explosion risk (Note 2) according to PVSTSC. The media of explosion risk means the gas or explosion admixture mixed by liquid steam, haze and air, and the lower explosive limit is less than 10%, or difference between upper explosion limit and lower explosive limit is large than or equal to 20% of media. Details see Table 3.0.5.
3.0.6 Shall consider on the media which are provided with maximal toxicity hazard or maximal explosion risk extent when multifold chemical media are involved. When a certain media is low content, the classification shall be considered roundly according to the hazard extent and content, and classified according to the classified criterion by the technological design of design organization or product & technology department of application organization.
3.0.7 The chemical media which are not listed in this standard shall be complied with aforesaid classification criterion, and classified by referring to the classification of close media.
