【2026 Pressure Vessels】Why does GB/T 150.1-2024 dedicate a separate chapter 4 to \"failure modes\"?

The old standard (version 2011) did not neglect safety; rather, it spread the requirements for controlling these 13 modes across various sections such as materials, design, and manufacturing. Designers often follow formulas as prescribed, but they may not develop a systematic understanding at the strategic level of \"which 13 risks I need to guard against.\" The establishment of Chapter 4 in the 2024 version is aimed at making this implicit security logic explicit.

II. The question then arises: Since the old standard has been in use for many years, why must the 2024 version be treated separately? Design by Rule has proven to be effective over the past few decades. However, the boundaries of engineering practice are constantly expanding, and some of the \"implicit assumptions\" of old standards are being challenged by new failure cases and device scales. Chapter 4 was introduced in response to the following practical engineering considerations: 1. The shift from the concept that instability occurs only under external pressure to the understanding that buckling can also occur under internal pressure. In GB/T150.3-2024, new sections 7.3.2.2 (Criteria for buckling of elliptical heads under internal pressure) and 7.4.2.2 (Criteria for buckling of disc-shaped heads under internal pressure) were added. In the past, we believed that internal pressure would only generate tensile stress, but engineering practice with large thin-walled vessels has shown that under internal pressure, the crown area of the head may develop circumferential compressive stress sufficient to cause instability. This addition states that the assumed boundary of \"internal pressure safety\" has been exceeded, and the failure mode of \"buckling\" must be identified at the design input stage.

2. From \"material homogeneity\" to \"environmentally induced fracture\": GB/T150.1-2024 specifically lists \"environmentally induced fracture\" among the long-term failure modes. This includes wet hydrogen sulfide stress corrosion cracking, chloride ion stress corrosion cracking, hydrogen-induced cracking, etc. As chemical media become increasingly complex, materials fail not only due to insufficient strength but also because of specific medium environments. Including \"environmentally induced fracture\" in Chapter 4 forces designers to take into account the coupling effect of \"material-media-stress\" during the material selection and design stages, rather than focusing solely on strength calculations.

3. Formal integration with the damage identification system: TSG21-2016, the \"Safety Technical Inspection Regulations for Fixed Pressure Vessels,\" requires that design documents reflect the \"mechanism of damage.\" GB/T30579-2022 \"Identification of Damage Modes in Pressure Equipment\" details dozens of specific types of damage patterns. The 13 failure modes in Chapter 4 of GB/T150.1-2024 precisely constitute the focal point of these two standards at the \"design stage\". It resolves the potential disconnects that existed in the past, where design was based on 150, damage assessment on 30579, and supervision and inspection followed TSG standards, thereby achieving consistency across the entire life cycle – from design to manufacturing, use, and inspection.

III. The core purpose of Chapter 4: Shifting from \"checking formulas\" to \"preventing failures\". The introduction of Chapter 4 represents an important shift in design philosophy: designing according to rules does not mean merely checking formulas; even when following a conventional design approach, it is necessary first to identify potential failure modes. The traditional design process was linear: receive requirements → calculate thickness → produce drawings. The new process should be circular: receive requirements → identify relevant items among the 13 failure modes outlined in Chapter 4 → select appropriate standard provisions (such as strength calculations per 150.3, welding procedures per 150.4, and anti-corrosion measures per 30579) → verify the entire process.

For example, in the case of a hydrogenation reactor that is started and stopped frequently: The old approach was to calculate the thickness based on internal pressure and the service life using fatigue criteria. New approach: Identify those involving environmentally induced failure (hydrogen corrosion), creep (high temperature), fatigue, and corrosion fatigue according to Chapter 4. Subsequently, hydrogen corrosion resistance is achieved through material selection (150.2) and heat treatment (150.4); creep resistance relies on high-temperature endurance strength (150.2/150.3); and fatigue resistance is attained through structural optimization and testing (Appendix 150.3).

IV. Impact on the implementation of design documents: After the implementation of 150.1-2024, it will be difficult for design documents that merely refer to “GB/T150” in a general manner to pass rigorous review and inspection processes. It is recommended to make the following adjustments in the design specifications: Explicitly state the results of failure mode identification. It is suggested to add a statement in the “Design Basis” or “Technical Specifications” section stating that: “The design of this container complies with the requirements of Chapter 4 of GB/T150.1-2024; the relevant failure modes identified are: short-term – plastic collapse, buckling.” ； Cycle – Fatigue (design cycle count N=××) ； Long-term – the environment facilitates fractures. Prevention and control measures for various failure modes are detailed in the relevant sections. ”This transforms \"passive formula checking\" into \"proactive risk prevention\", creating a clear chain of responsibility tracing.

Special justification for multi-mode coupling: For complex vessels involving both high-temperature creep and corrosion, or cryogenic conditions and fatigue, reliance solely on Section 150.3 is not sufficient. The design documents should clearly state which standard clauses are used to control the various identified failure modes, and how the interactions between these modes are assessed.

Meeting higher-level requirements for document control: GB/T150.1-2024 strengthens the quality control of design documents. Design documents for Class III containers require approval at four levels (including approval by the technical supervisor), and they must be retained for a period no shorter than the design service life of the container. The failure mode identification records in Chapter 4 will be one of the primary documents used by the inspection department to verify the completeness of design inputs.