Core Regulatory Principles for the Design Life of Pressure Vessels
In China’s special equipment safety management system, there is no uniform, fixed design life applicable to all pressure vessels. According to the current “Safety Technical Supervision Regulations for Stationary Pressure Vessels” and other relevant regulations, the core principle is that…The design documents must clearly specify the design service life..
This means that the design life of a pressure vessel is determined during the design phase through comprehensive calculations by the design organization, taking into account such factors as the equipment’s intended application, the working medium, operating conditions, and material properties. Regulations require the manufacturer to fabricate the vessel strictly in accordance with the design documentation and to clearly indicate the specified design life on the nameplate and data sheet.
Guidance of technical standards on design life
When determining the design service life, the design organization shall strictly comply with the relevant national technical standards. Taking the GB/T 150 series of standards for pressure vessels as an example, the determination of the design life must take into account multiple technical factors in a comprehensive manner:
- Corrosion allowance: Based on the corrosivity of the medium and the expected service life, appropriately specify a corrosion allowance for material thickness.
- Material properties: Select materials that can maintain adequate mechanical properties and fatigue resistance over the long term under the design temperature and pressure.
- Structural form: To prevent severe stress concentrations and thereby enhance the equipment’s fatigue life.
The strict implementation of these technical standards is the foundation for ensuring the safe and reliable operation of pressure vessels throughout their design life.
Considerations for the Design Life of Typical Equipment Such as Gas Storage Tanks
As a common pressure vessel in industrial applications, the design service life of an air receiver tank is a key concern for many enterprises. Typically, the design life of a standard air storage tank is set to10 years, 15 years, or 20 years, but this is not a legally mandated uniform standard.
The specific design life of a gas storage tank depends entirely on its condition at the time of manufacture.Design drawings and technical documentsIf the stored medium is corrosive or possesses special properties, the design institute may reduce the design life or specify higher‑grade materials and enhanced corrosion‑protection measures. Therefore, the user shall meticulously verify the equipment’s nameplate and the design service life indicated on the as‑built drawings during procurement and acceptance.
Mechanisms for Handling Structures Upon Reaching Their Design Service Life
When a pressure vessel (including a gas storage tank) reaches its design service life, it does not necessarily have to be immediately and compulsorily scrapped. National regulations provide a scientifically sound and compliant pathway for the continued operation of such equipment:
- Safety Assessment and Inspection: The user shall engage a qualified special equipment inspection agency to conduct a comprehensive safety assessment and regular inspections of the equipment.
- Handle the change procedures.If the inspection and assessment conclude that the equipment remains fit for continued use, the user shall submit the relevant report to the original registration authority to apply for the amendment or extension of the design service life.
- Shorten the inspection cycleFor equipment approved for continued use beyond its original service life, inspection bodies typically, based on the equipment’s actual condition, appropriately shorten the subsequent periodic inspection intervals to enhance safety oversight.
Through this closed-loop management mechanism—characterized by clear design, regular inspections, and periodic assessments—we have both ensured the inherent safety of pressure vessels and achieved the rational utilization of equipment resources.