What is the scope of pressure vessels governed by the Code of Acceptance?

To facilitate safety technology supervision and management, pressure vessels within the scope of application of these regulations are classified into three categories. The criteria for classification are as follows: A vessel falls under Category 3 if it meets one of the following conditions: 1) High-pressure vessel； 2) Medium-pressure vessels (only for media with extremely high and high toxicity) ； 3) Medium-pressure storage vessels (only for flammable or moderately hazardous media with a pV product of 10 MPa·m3 or greater) ； 4) Medium-pressure reaction vessel (only for flammable or moderately hazardous media with a pV product of 0.5 MPa·m3 or greater) ； 5) Low-pressure vessels (only for media with extremely high or high toxicity, and a pV product of 0.2 MPa·m3 or greater) ； 6) High-pressure and medium-pressure shell-and-tube waste heat boilers ； 7) Medium-pressure glass-lined pressure vessels ； 8) Pressure vessels manufactured from materials with a high strength level (meaning that the minimum specified value for tensile strength in the relevant standards is 540 Mpa or higher) ； 9) Mobile pressure vessels, including railway tank cars (for liquefied gases and cryogenic liquids), tank trucks, and tank containers (for liquefied gases and cryogenic liquids), etc ； 10) Spherical storage tanks (volume greater than or equal to 50 m3) ； 11) Cryogenic liquid storage vessels (capacity greater than 5 m3). A pressure vessel falls under Category II in any of the following situations (except as specified in Paragraph 1 of this article): 1) Medium-pressure vessels ； 2) Low-pressure vessels (only for media with extremely high and high toxicity) ； 3) Low-pressure reaction vessels and low-pressure storage vessels (only for flammable media or media with moderate toxicity) ； 4) Low-pressure shell-and-tube waste heat boiler ； 5) Low-pressure glass-lined pressure vessels. Low-pressure vessels are classified as Class 1 pressure vessels (except as provided in Paragraphs 1 and 2 of this article).

The original poster has seen many of your questions; you can read the TSGR004-2009 Regulations on Safety Supervision of Fixed Pressure Vessels, as much of the information there can answer your questions. Note: There are amendment sheets for this standard.