GBT 21385 National Standard Certification | How Do Trunnion Mounted Ball Valves Solve Large‑Bore Opening And Closing Challenges in Urban Gas Pipeline Networks?

Preface: The "Opening and Closing Pain Points" of Urban Gas Pipelines and the Core Significance of GBT 21385 National Standard

Urban gas pipelines are the "lifeline" ensuring residential and industrial gas supply, and large-diameter valves, as the "core switches" of pipeline transportation, their opening and closing performance directly determines the safety, stability and efficiency of pipeline operation. In the process of urban gas pipeline upgrading and renovation, the opening and closing problem of large-diameter trunnion ball valves has been plaguing industry practitioners — large-diameter pipelines (DN≥100mm) bear high pressure and the medium is flammable and explosive. Traditional valves are prone to problems such as excessive opening and closing torque, difficult operation, and unstable sealing, which may lead to gas leakage, pipeline paralysis and other safety hazards in severe cases.

The GBT 21385 national standard (the latest current version is GB/T 21385-2025), as the core national standard for metal-sealed ball valves, clearly specifies the technical requirements, test methods, inspection rules and other key contents of flanged, welded and threaded connected metal-sealed ball valves. It is applicable to ball valves with nominal size DN15～DN600 and nominal pressure PN16～PN420, providing an authoritative basis for the production, selection and application of large-diameter trunnion ball valves, and is also the "compliance bottom line" and "technical benchmark" for solving the problem of large-diameter opening and closing. Only trunnion ball valves certified by the GBT 21385 national standard can meet the high-pressure, high-risk and high-reliability operation requirements of urban gas pipelines, avoiding safety and compliance risks from the source.

I. Core Opening and Closing Problems of Large-Diameter trunnion ball valves in Urban Gas Pipelines

In urban gas pipelines, the opening and closing problem of large-diameter trunnion ball valves (usually DN100 and above) is essentially a dual challenge of "torque control under high pressure conditions" and "sealing stability". Specifically, it can be divided into 3 types of core problems, which are also common pain points in the industry:

1. Excessive opening and closing torque, high operation difficulty: The gas pressure in large-diameter pipelines is relatively high (usually ≥PN40). Traditional trunnion ball valves have tight fit between the valve core and the valve seat without a reasonable pressure relief structure, resulting in the need for huge driving force during opening and closing. Manual operation is laborious, and even normal opening and closing cannot be achieved; even with electric drive, valve jamming may occur due to insufficient torque, affecting the efficiency of pipeline maintenance and emergency disposal.

2. Unstable sealing performance, easy to cause leakage: Gas is a flammable and explosive medium, which has extremely high requirements on the sealing performance of valves. During the frequent opening and closing of large-diameter trunnion ball valves, the valve core and valve seat are prone to wear and deformation. Especially under high-pressure conditions, the pressure distribution on the sealing surface is uneven, which is easy to cause gas leakage and埋下 safety hazards; at the same time, if the valve does not meet the sealing standards of the GBT 21385 national standard, it will also face compliance penalties.

3. Insufficient adaptability, short service life: The environment of urban gas pipelines is complex. In some areas, there are problems such as large temperature difference changes and impurities in the medium. The material and structural design of traditional large-diameter trunnion ball valves are not fully adapted to this working condition, which is prone to component corrosion, jamming, aging and other problems, leading to shortened valve service life, increased pipeline operation and maintenance costs, and frequent valve replacement will affect the normal operation of the pipeline.

II. GBT 21385 National Standard Certification: Dual Guarantee of Compliance and Technology for Solving Opening and Closing Problems

GBT 21385 national standard certification is not a simple "qualified inspection", but strictly regulates the opening and closing performance, sealing performance, durability, etc. of large-diameter trunnion ball valves from the whole process of design, material, process, test, providing clear technical guidance for solving opening and closing problems. Its core requirements are mainly reflected in 3 aspects:

1. Material and structure specifications, reducing opening and closing resistance from the source: The GBT 21385 national standard clearly specifies the material standards for the core components of large-diameter trunnion ball valves, such as valve core, valve seat and valve stem, requiring the use of high-strength, corrosion-resistant metal materials. At the same time, it standardizes the fixed structure of the valve core — fixing the valve core through upper and lower support shafts to avoid uneven pressure on the sealing surface caused by the floating of the valve core, thereby reducing the opening and closing torque. Compared with floating ball valves, trunnion ball valves meeting national standard requirements can reduce the opening and closing torque by 30%-50% under large-diameter and high-pressure conditions, greatly improving operational convenience.

2. Mandatory requirements for sealing performance, eliminating leakage risks: The national standard has formulated strict test standards for the sealing performance of trunnion ball valves, including shell test, sealing test, life test, etc., requiring that under nominal pressure, the valve shell has no leakage, the sealing surface has no leakage, and the sealing performance can still meet the requirements after the number of opening and closing times reaches the specified standard. Large-diameter trunnion ball valves certified by the national standard adopt a floating valve seat design, and the medium pressure can push the valve seat to fit the valve core to achieve dynamic sealing. Even after frequent opening and closing, it can maintain stable sealing performance, fundamentally solving the problem of gas leakage.

3. Requirements for adaptability and durability, adapting to complex pipeline working conditions: Combined with the operation characteristics of urban gas pipelines, the GBT 21385 national standard puts forward clear requirements for the temperature resistance, corrosion resistance, anti-jamming and other performance of valves, requiring valves to adapt to temperature difference changes in different regions, resist impurity wear in the medium, and standardize the assembly and commissioning process of valves to ensure that valves are not prone to jamming, aging and other problems during long-term operation, extend service life and reduce operation and maintenance costs.

III. trunnion ball valves Complying with GBT 21385 National Standard: 3 Core Technologies to Solve Large-Diameter Opening and Closing Problems

Relying on the technical specifications of the GBT 21385 national standard, the industry has developed large-diameter trunnion ball valves suitable for urban gas pipelines through optimized design and innovative processes. Its core technologies mainly focus on "reducing opening and closing torque, improving sealing performance, and enhancing adaptability", fundamentally solving the opening and closing problems:

1. Pressure relief structure design, greatly reducing opening and closing torque: The "valve core pressure relief hole" design is adopted. During the opening and closing of the valve, the pressure on both sides of the valve core is balanced through the pressure relief hole, reducing the pressure difference between the valve core and the valve seat, thereby reducing the opening and closing torque and realizing easy opening and closing. At the same time, combined with the worm gear transmission mechanism, the driving force can be further amplified. Whether it is manual operation or electric drive, stable and efficient opening and closing can be achieved, solving the pain point of difficult operation of large-diameter valves. Some high-end products also adopt a pump-controlled motor drive method, which can realize manual/automatic switching and support long-distance automatic operation, improving the efficiency of pipeline operation and maintenance.

2. Double sealing surface + elastic valve seat design, enhancing sealing stability: A double sealing surface design combining metal hard seal and elastic seal is adopted, which not only meets the sealing requirements of the GBT 21385 national standard, but also adapts to the sealing needs of different working conditions — metal hard seal ensures sealing reliability under high pressure and high temperature, while elastic seal makes up for minor wear of the sealing surface to achieve "zero leakage". At the same time, the elastic valve seat can automatically adjust the fitting degree according to the medium pressure, avoiding sealing failure caused by pressure fluctuation, and adapting to the pressure change characteristics of urban gas pipelines.

3. Corrosion-resistant and anti-jamming technology, improving durability and adaptability: The core components are made of corrosion-resistant materials such as stainless steel and Hastelloy, and the surface is hardened to resist impurity wear and corrosion in the gas medium; the valve stem adopts a packing seal structure to prevent gas leakage and avoid valve stem jamming; in addition, a lubrication mechanism is set inside the valve to reduce friction between components, extend the opening and closing life, ensure the valve operates stably for a long time in complex pipeline environments, and reduce operation and maintenance costs.

IV. Selection Suggestions: How to Choose Large-Diameter trunnion ball valves Complying with GBT 21385 National Standard and Suitable for Pipelines?

For urban gas pipeline practitioners, choosing large-diameter trunnion ball valves certified by the GBT 21385 national standard is the key to solving opening and closing problems and ensuring pipeline safety. When selecting, focus on 3 points:

1. Confirm national standard certification qualifications: Prioritize manufacturers with GBT 21385 national standard certification certificates, verify whether the certification scope covers the required nominal size and nominal pressure, avoid selecting "fake certification" products, ensure that the valve meets industry compliance requirements, and avoid safety and compliance risks from the source.

2. Match pipeline working condition parameters: Select the corresponding fixed ball valve model according to the actual pressure, medium composition and caliber of the pipeline — for example, for high-pressure pipelines (PN≥100), ball valves with pressure relief structure can be selected; for areas with more impurities in the medium, valves with wear-resistant materials can be selected to ensure that the opening and closing performance of the valve is perfectly adapted to the pipeline working conditions.

3. Pay attention to core performance indicators: Focus on the opening and closing torque, sealing performance, service life and other indicators of the valve, prioritize products with small opening and closing torque, stable sealing and strong durability, and pay attention to the manufacturer's after-sales service to ensure that problems can be solved in a timely manner when the valve has problems during later operation, reducing operation and maintenance costs.

Conclusion: GBT 21385 National Standard Leads, trunnion ball valves Guard the Safety of Urban Gas Pipelines

The safe operation of urban gas pipelines is inseparable from the reliable support of every core component. The opening and closing problem of large-diameter trunnion ball valves is both a technical challenge and a compliance requirement. As the "vane" of the industry, GBT 21385 national standard certification provides authoritative specifications for the R&D, production and application of large-diameter trunnion ball valves, and the innovative design based on national standard technology fundamentally solves the pain points such as excessive opening and closing torque, unstable sealing and insufficient adaptability.

Choosing large-diameter trunnion ball valves certified by the GBT 21385 national standard can not only ensure the safe, stable and efficient operation of urban gas pipelines, reduce safety hazards and operation and maintenance costs, but also meet industry compliance requirements, avoiding penalties and risks caused by non-compliant products. In the future, with the continuous upgrading of urban gas pipelines, the GBT 21385 national standard will be further improved, and the technology of large-diameter trunnion ball valves will continue to innovate, escorting urban energy transportation.