Navigating Valve Emission Standards: A Comparative Guide to API 624, API 641, ISO 15848-1, and TA Luft
Understanding Valve Emissions Standards: API 624, API 641, ISO 15848-1, and TA Luft
Valves and connectors are responsible for over 90% of emissions from leaking equipment, according to the Environmental Protection Agency (EPA). These emissions pose significant environmental and health risks, prompting governments worldwide to establish regulations aimed at reducing fugitive emissions.
To address this challenge, various standards have been developed to ensure valve integrity and minimize leakage. Among the most notable are API 624, API 641, ISO 15848-1, and TA Luft. Understanding these standards can help industry professionals select the appropriate testing protocols for their specific applications.
API 624 and API 641: The U.S. Approach
The American Petroleum Institute (API) introduced API 624 and API 641 to establish emission control benchmarks for valves. These standards align with the EPA’s efforts under the Clean Air Act, which has evolved since its inception in 1963 to address growing environmental concerns.
API 624 focuses on the performance of packing in rising stem valves. Introduced in 2014, it requires valves to undergo 310 mechanical cycles, three temperature cycles at 500°F (with an optional cycle at -20°F), and testing at a maximum pressure of 600 psi. Methane is used as the test medium, and the allowable leakage limit is set at 100 ppm, following the EPA Method 21 for fugitive emissions evaluation.
API 641, released in 2016, applies to quarter-turn valves and assesses both the packing and boundary connections. This standard involves 610 mechanical cycles, three temperature cycles up to 500°F, and pressures between 100 and 600 psi. Like API 624, it uses methane as the test medium and enforces a leakage limit of 100 ppm.
ISO 15848-1: A Global Standard
Established in 2006, ISO 15848-1 is a widely recognized international standard for shut-off and control valves. It provides a flexible testing framework with different classifications for temperature, tightness, and endurance. Unlike API standards, ISO 15848-1 allows for both methane and helium as test mediums.
The standard classifies leakage rates into three categories:
Endurance classes are also defined based on the number of mechanical cycles required for qualification. Shut-off valves range from 205 cycles (CO1) to 2,500 cycles (CO3), while control valves undergo anywhere from 20,000 cycles (CC1) to 100,000 cycles (CC3). Temperature classifications extend from -196°C to 400°C, and pressure ratings are determined by the valve material's P/T rating. Notably, ISO 15848-1 allows for a single stem seal adjustment (SSA) per endurance class if leakage exceeds a specified threshold, offering greater flexibility in valve qualification.
TA Luft: Germany’s Rigorous Standard
Germany’s TA Luft (Technical Instructions on Air Quality Control) has been a key regulatory framework since 1964. The most recent update in 2021 aligns its testing requirements with ISO 15848-1 (2015). However, TA Luft imposes its own stricter leakage limits, categorized as:
Unlike other standards, TA Luft’s leakage criteria are pressure-dependent, meaning the permissible emission levels vary based on the operating pressure and temperature conditions.
Which Standard Should Be Used?
The choice of standard depends on the specific needs of end users and industry requirements. While API 624 and API 641 are widely used in the U.S. for petroleum industry applications, ISO 15848-1 provides a more versatile approach by accommodating multiple test mediums, broader temperature ranges, and pressure-dependent qualifications. Additionally, ISO 15848-1 offers tiered tightness classifications and allows limited adjustments, making it a more adaptable standard for diverse applications.
TA Luft, on the other hand, enforces stricter emission limits, making it ideal for industries operating under stringent environmental regulations.
Final Thoughts
Fugitive emissions control is crucial for environmental sustainability and regulatory compliance. While each standard serves a valuable purpose, ISO 15848-1 stands out as the most comprehensive due to its flexibility and detailed classification system. Adopting this standard more widely in the U.S. could enhance valve testing procedures and contribute to more effective emissions reduction strategies.
........................................................................................................................................................................................
Since 2013, TC2 has been helping companies improve their business performance. Today, we are a dynamic group offering a high level of specialization in the T.I.C. (Testing, Inspection, and Certification) industry.
Our Services are:
? Vendor Management Services
??Engineering & Technical Services
?? Assurance Services