Summary of Common Issues in Pressure Vessel Design Reviews

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Design Conditions Diagram 1. The operating parameters in the design conditions diagram (such as pressure, temperature, materials, pipe end orientation, etc.) do not match those specified on the design drawings； 2. There are missing items in the design condition diagram ； 1) The design conditions diagram lacks information on the natural conditions of the location where the pressure vessel will be used ； 2) The main components of the medium and its properties are missing in the design condition diagram ； 3) The expected service life is missing in the design condition diagram ； 4) The design condition diagram lacks device diagrams; the geometric dimensions in the diagram are incomplete, and information such as the orientation of pipe openings is missing ； 3. The design condition sheet lacks the confirmation signature of the client (orderer) ； 4. The design condition diagram cannot be replaced by the construction drawings provided by the user; it must be prepared using the tables specified in the program documents and signed accordingly. Design data table 1: The operating parameters in the design data (technical specifications) table of the overall diagram do not match the parameters shown in the design conditions diagram ； 2. Missing items in the design data table: (1) The design data table lacks information on operating conditions and design parameters: operating temperature, main components of the medium, properties of the medium (toxicity and explosion risk), volume, heat exchange area, specifications of the heat exchange tubes, number of stages, material of the main pressure-bearing components. It also lacks information on natural conditions such as seismic intensity, earthquake classification, soil type at the site, and basic wind pressure ； ⑵Storage containers, such as liquefied gas tanks, do not indicate a filling coefficient ； ⑶Storage containers prone to stress corrosion do not specify the limited content of corrosive agents ； ⑷The design service life of the pressure vessel is not specified in the design data sheet ； ⑸The type of leakage test is not specified in the design data sheet ； ⑹Containers equipped with safety valves lack the set pressure of the safety valves as well as their specifications and models. 3. The design parameters filled in the design data (technical specifications) table are incorrect ； ⑴The shell-and-tube heat exchanger does not specify the inlet and outlet operating temperatures for the tube side and the shell side separately ； ⑵The metal wall temperatures of the tube side and shell side were determined improperly ； ⑶In the technical specifications table, the operating temperature specified is ⑷; for devices with jackets, the design temperature of the inner cylinder is set at a lower value, without taking into account the influence of the jacket temperature ； ⑸The corrosion margins for the tube side and shell side of the heat exchanger are not specified separately ； ⑹The corrosion margin of the jacketed vessel was not filled in separately for the inner tube and the jacket ； The selection of the corrosion margin for the inner cylinder in the jacket did not take into account the influence of the media in the inner cylinder chamber and the jacket chamber ； ⑺When the medium is a liquefied gas, the design pressure is not determined based on the saturated vapor pressure at the design temperature. 4. For equipment for which the maximum allowable operating pressure must be specified, most of them have the following problems: (1) Containers equipped with safety valves or rupture discs that require a gas-tightness test do not indicate the maximum allowable operating pressure as required by the ‘Regulations on Solid and Liquid Containers’ ； ⑵The set pressure of the safety valve is not chosen appropriately ； ⑶The pressure for the hydrostatic test was determined incorrectly. For containers equipped with safety valves and subject to airtightness testing, although the maximum allowable operating pressure is indicated in the diagram, the pressure for the hydrostatic test was still calculated using the design pressure instead of the maximum allowable operating pressure ； ⑷The maximum allowable operating pressure was determined incorrectly; it only meets the strength requirements for the shell (cylinder, head, or sphere), without any strength verification being conducted for other pressure-bearing components such as manholes, flanges, flat covers, and reinforcement elements for openings ； Due to the excessively high value set for the maximum allowable operating pressure, other pressure-bearing components (manholes, flanges, reinforcement for openings, etc.) fail to meet the strength requirements. 5. The names used in the design data table do not follow the names specified in current codes and standards; for example, the welding joint coefficient is still referred to as the weld coefficient, the non-destructive testing ratio is called the inspection length, the filling coefficient is still termed the filling factor, the set pressure of the safety valve is still referred to as the opening pressure, and the level of non-destructive testing technology is called the radiographic quality, among other things.