4　Piping Class

4.0.1　Petrochemical metallic piping may be classified on the basis of delivery fluids and the design conditions according to Table 4.0.1 of this code.Common toxic，flammable and combustible fluids may be determined in accordance with Appendix A of this code.Piping class codes shall comply with Appendix B of this code.

4.0.2　In addition to Article 4.0.1 of this code，petrochemical piping classification shall also comply with the following requirements:

1　Class of piping for conveying oxygen gas shall be determined based on design conditions and Class II flammable and combustible gas as specified in Table 4.0.1 of this code；

2　Class of piping for conveying toxic or different mixed combustible/flammable fluids shall be determined based on their hazardous levels and contents；

3　Class of piping for simultaneously conveying toxic and combustible/flammable fluids shall be determined based on the higher piping class as specified in Table 4.0.1 of this code.

4.0.3　In addition to compliance with classes of piping，inspection levels for piping listed in Table 4.01 of this code shall also comply with the following requirements:

1　Inspection level for titanium and titanium alloy，zirconium and zirconium alloy，nickel and nickel alloy，high nickel chrome molybdenum austenitic stainless steel piping and piping for severe cyclic conditions shall not be less than Grade 1；

2　Inspection level for chromium molybdenum alloy，duplex stainless，aluminum and aluminum alloy piping shall not be less than Grade 2；

3　Inspection level for austenitic stainless piping and carbon piping required for impact test in design documents shall not be less than Grade 3.

4.0.4　Construction and acceptance of oxygen piping shall also comply with GB 16912 Safety Technical Regulation for Oxygen and Relative Gases Produced with Cryogenic Method.