【2026 Knowledge Expansion】GB/T150 and TSG21 do not apply to pressure-bearing components such as pump casings and compressor housings; this does not mean that such components can be designed arbitrarily without any regulatory constraints
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Question 1: Why are pressure-bearing components such as pump casings and compressor housings, which are indeed subject to pressure, \"excluded\" by 150/TSG21? In fact, the nature of the load is completely different. The design logic of the GB/T 150 series of standards assumes that internal/external pressure is the primary loading factor; the overall strength is calculated based on film stress, with only secondary loads such as those resulting from openings, flanges, and supports being taken into account. This approach is suitable for stationary pressure-bearing equipment.
For components such as pump casings, compressor cylinders, and hydraulic cylinders, the primary load is not merely internal pressure; the stress conditions are much more complex: 1. In centrifugal pumps, the rotation of the impeller creates a centrifugal force field, resulting in continuous pressure fluctuations in the flow channels. The casing is subjected to a combined load of this pressure field, vibrations caused by rotor imbalance, and thermal shocks. Given the high frequency of start-up and shutdown cycles, the risk of fatigue failure is extremely high. 2. Reciprocating compressor cylinder: The reciprocating motion of the piston causes periodic fluctuations in gas pressure. The cylinder is subjected over time to alternating internal pressures, lateral forces from the piston, and inertial loads transmitted by the connecting rods; alternating stresses are the main cause of failure. 3. Hydraulic cylinder: The piston rod moves back and forth, and the cylinder barrel is subjected to thermal-mechanical coupled loads resulting from internal pressure, bending moments exerted by the piston rod, and seal wear; the stress conditions involved are well beyond those encountered in static loading situations.
That is, GB/T 150 applies to containers that are under static pressure; the failure modes include static strength, creep, and uniform corrosion； Components such as pumps, compressors, and hydraulic cylinders are subjected to pressure while in motion, and their failure modes mainly include fatigue, wear, and rotor dynamics failures. Their design systems and verification logic are completely different; such components fall under the jurisdiction of their respective machine-specific standards and are not covered by the 150 standard.
Similarly, the TSG21 supervision regulations apply primarily to fixed and stationary pressure-bearing equipment. Rotating/reciprocating pressure-bearing components are classified under other categories in the catalog of special equipment or according to the standards for their respective machine products, and are not included in the supervision system for pressure vessel records.
Question 2: The absence of application of standards does not mean there is no oversight. This is the most common mistake made on site: the fact that GB/T150 and TSG21 are not applicable does not mean that such components can be designed arbitrarily without any regulatory constraints; it’s merely a change in the applicable standards. The specific standard guidelines for various types of moving pressure-bearing components are as follows:
The aforementioned host standards set clear and mandatory requirements regarding component wall thickness, hydrostatic testing, non-destructive testing, and strength verification; they simply do not adopt the calculation logic of GB/T 150.
As an \"example\": According to the API610 standards, the hydrostatic test requirement for pump casings is 1.5*the maximum allowable operating pressure, with a superpressure of not less than 0.175 MPa; this differs from the 150 standard formula of \"1.25*design pressure\", but the logic behind the safety checks is similar.
Two major frequent errors at the site: 1. Design-related mistake: The wall thickness formula from GB/T150 was used directly to calculate the pump casing, resulting in thicknesses that were lower than the requirements specified by API standards; this led to the products being rejected by the client after delivery and requiring rework. 2. Misconceptions on the user side: The cylinder of the hydrogen compressor inside the device was sent to an inspection agency for registration as a pressure vessel, but was rejected; Article TSG21 explicitly excludes it from the scope of supervision.
Question 3: Under what circumstances will it fall back under the jurisdiction of 150/TSG21? Not all pressure-bearing components associated with the unit are excluded; auxiliary stationary pressure equipment represents a key exception to the core boundaries and is a focal point for on-site demarcation. Chapter 1 of TSG21‑2016 specifies a simplified list of items subject to regulation, defining separately certain pressure-containing equipment used with certain types of machinery: gas storage tanks and the pressure vessels of accumulators that include mobile air compressors.
Clear distinction: The compressor’s main cylinder body is a moving pressure-bearing component, and it is excluded from the scope of TSG21 and GB/T150.
The compressor skid is equipped with a horizontal gas storage tank: it is a stationary pressure-bearing device that falls under the jurisdiction of TSG21; only the requirements of the general provisions, design, and manufacturing sections apply to it, while certain provisions regarding use management and periodic inspection are exempted.