How to Determine the Design Pressure of a Pressure Vessel

I. Core Determination Principles
The design pressure is the maximum pressure set at the top of the pressure vessel. It must be determined in conjunction with the type of safety relief device and must not be lower than the working pressure.

II. Determination Methods for Different Devices

1. Safety Valve Only: First, determine the safety valve opening pressure, generally 1.05 to 1.1 times the working pressure. The final design pressure of the pressure vessel should be equal to or slightly greater than the safety valve opening pressure, and the opening pressure must not exceed the design pressure.

2. Rupture Disc Only: First, determine the design burst pressure of the rupture disc. The design pressure should not be lower than the sum of the design burst pressure and the upper limit of the selected rupture disc's manufacturing range, and the rupture disc's rated pressure must not exceed the design pressure.

3. Safety Valve and Rupture Disc Simultaneously: The pressure requirements of both must be met separately. The design pressure is the greater of the two requirements, and neither of the rated pressures must exceed the design pressure. 

4. Other Special Scenarios: For outlet pipelines equipped with safety valves: the pressure should not be lower than the safety valve opening pressure plus the pipeline pressure drop. For liquefied gas without insulation: the pressure should not be lower than 50°C corresponding to the saturated vapor pressure of the medium.