ISO 12101:2025 is officially titled:“ Industrial valves— Measurement, test and qualification procedures for fugitive emissions— Classification system and qualification procedures for type testing of stem seals for valves.” π www. valve-world. net Valve World August 2025
relied on their own test procedures, long before standards such as Germany’ s TA-Luft, ISO 15848-1, or the API 624 and 641 tests became prevalent. While useful, these standards each serve different segments. API 624 targets rising stem valves. API 641 addresses quarter-turn valves. ISO 15848-1 is broader, covering a variety of valve types and test temperatures, but it’ s also more complex. TA-Luft is a regulatory emission standard with stricter leak limits, especially in Germany. Each standard defines its own test media( methane or helium), temperature ranges, cycle counts, and leak classes. ISO 15848- 1, for instance, spans temperatures from-196 ° C to + 400 ° C, while API standards cap at 260 ° C. It also categorises stem seals by tightness( A, B, C) and endurance. During testing, many valve manufacturers struggle to meet the requirements for fugitive emissions, like class AH— tightness class H with helium. This level is typically achievable only with bellows seals or equivalent shaft sealing. Still, end users often demand it—
sometimes even for graphite seals or for valve types( such as gate or globe valves) that are not optimally designed for such performance. And that’ s the crux: achieving these results depends not just on the seal, but on the entire assembly, including how it’ s installed. Details like the torque on the gland follower or packing compression or stress must be just right. Too often, users rely on brochures filled with lofty promises— temperature ranges from-200 ° C to 800 ° C, for example. But in our lab, seals like these fail at‘ just’ 200 ° C. Why? Upon investigation, the manufacturer reveals:“ Oh, those values are valid if you use an extension.” A valve extension places the stem seal outside the hot or cold zone— often outside the insulation— so it sits at ambient conditions. But if that’ s not stated clearly, is it fair to include it in the data sheet? As I often joke with manufacturers:“ Can I claim car tyres that last 200,000 km without wear?” They say no. I reply:“ Sure— if they’ re only used on the spare wheel in your trunk!”
FUGITIVE EMISSIONS
Limitations of current standards
API 622 offers a performance test for valve packing, simulating 1,510 cycles and up to 41,4 barg( 600 psig) methane as test gas, cycling between ambient and 260 ° C. It uses a standardised fixture, which helps compare products under identical conditions. But that’ s exactly the limitation: standardised fixtures don’ t reflect how seals actually perform in real valves, especially when manufacturers rely on specific geometries, coatings or loading mechanisms to optimise performance. ISO 12101 takes a different approach. Instead of dictating a single rigid test fixture, it provides seal manufacturers with the flexibility to define their own test setup— allowing for innovation and better real-world relevance. The fixture design must still be reported, ensuring transparency for valve manufacturers who want to replicate the performance.
Why ISO 12101 was needed
For years, I believed a new standard was essential— one focused specifically on stem seals. Too often, critical data like minimum surface pressure, installation instructions, or true performance limits were missing from documentation. Rather than pursue a national or European( CEN) standard, I contacted NEN( Royal Netherlands Standardisation Institute) in 2019 to propose an international ISO standard directly. Since then, I’ ve served as Team Leader of ISO / TC 153 WG 5, the group behind ISO 12101. From the start, we aimed to include the entire supply chain. I invited both ESA( European Sealing Association) and FSA( Fluid Sealing Association)— key stakeholders representing the global sealing industry— to actively participate. ESA alone includes over 50 companies, with 12,500 employees and billions in annual turnover. Although one might expect resistance from seal manufacturers— after all, testing costs money— the opposite has proven true. ESA and FSA now support the standard. They understand its long-term value: a shared benchmark that raises quality, improves performance, and builds trust across the industry.
Testing the stem seal of a cryogenic valve using a helium detector with sniffer probe.
ISO 12101 for valve stem seal qualification
ISO 12101:2025 is officially titled:“ Industrial valves— Measurement, test and qualification procedures for fugitive emissions— Classification system and qualification procedures for type testing of stem seals for valves.” π www. valve-world. net Valve World August 2025
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