Fugitive Emissions Standards for Valves

Valves and connectors account for over 90% of emissions from leaking equipment, according to the Environmental Protection Agency (EPA) [1]. Because these emissions can cause many health and environmental issues, countries have created laws and regulations that help reduce the leakage of these emissions.

API 624 AND API 641

Through the EPA, the Clean Air Act was introduced in the United States in 1963. As environmental problems increased, this act evolved through multiple milestones and the implementation of the 1990 Clean Air Act Amendments. With the laws and regulations provided by the EPA, the American Petroleum Institute (API) created standards for valves to reduce fugitive emissions in the U.S. specific to its industry.

The API 624 – Type Testing of Rising Stem Valves Equipped with Graphite Packing for Fugitive Emissions, was issued in February 2014. This test uses methane as the medium for testing leakage. The API 624 is a valve-type test meant to focus on the performance of the packing of rising stem valves. To qualify the valve for the API 624 testing, the packing must have previously qualified according to the API 622 test, which focuses on the packing sets in the valve. There are 310 mechanical cycles, three temperature cycles at 500°F, with the option of one cycle at -20°F, and a maximum allowed pressure of 600 psi for the API-624 test. During the test, no stem seal adjustments are allowed. The API 624 uses the EPA Method 21 as the basis when evaluating the leakage of fugitive emissions and has an allowable leakage limit of 100 ppm.
Figure 1. Overview of API 624

The API 641 – Type Testing of Quarter-turn Valves for Fugitive Emissions, issued in October 2016, is a valve-type test for quarter-turn valves. Like the API 624, the test focuses on the performance of the packing, as well as the boundary connections, and uses methane as a test medium. This test produces 610 mechanical cycles, three temperature cycles up to a maximum of 500 °F, and a minimum allowed pressure of 100 psi, with a maximum allowed pressure of 600 psi. No stem seal adjustments are allowed during testing. The API 641 uses the EPA Method 21 as the basis when evaluating the leakage of fugitive emissions. The allowable leakage limit is 100 ppm.
Figure 2. Overview of API 641

ISO 15848-1

In 1947, a group of delegates from 25 countries founded the International Organization for Standardization (ISO). They unified under the goal of ensuring that products and services would be safe, reliable and an acceptable quality. Over the years, hundreds of different international standards were developed and published by ISO. In January 2006, through the guidance of an international team, the ISO 15848-1 (Industrial valves — Measurement, test and qualification procedures for fugitive emissions — Part 1: Classification system and qualification procedures for type testing of valves) was issued.

The ISO 15848-1 is a valve-type test used for shut-off valves and control valves focused on the performance of the packing and body seals. This test uses methane or helium for the test medium. The ISO 15848-1 tests within three types of classes: temperature class, tightness class and endurance class. There are three tightness classes a valve can achieve while qualifying for the ISO 15848-1. For methane: AM ≤ 50 ppm, BM ≤ 100 ppm, CM ≤ 500 ppm. For helium: AH ≤ 1.0E-05 mg/(s*m), BH ≤ 1.0E-04 mg/(s*m) and CH ≤ 1.0E-02 mg/(s*m). If the leak rate surpasses a tightness class limit, one stem seal adjustment may be done (one per endurance class). If the valve still is above a tightness class of C after the stem seal adjustment or surpasses a 50 ppm leakage rate on the valve’s body seal, then it is disqualified. The three endurance classes for shut-off (CO) and control (CC) valves are CO1/CC1, CO2/CC2 and CO3/CC3. To reach a higher endurance class, the previous one must be attained first. Each endurance class must undergo several mechanical cycles. For shut-off valves: CO1 – 205 cycles, CO2 – 1500 cycles, and CO3 – 2500 cycles. For control valves: CC1 – 20,000 cycles, CC2 – 60,000 cycles, and CC3 – 100,000 cycles. The temperature classes range from -196°C, -46°C, -29°C, room temperature (RT), 200°C and 400°C. The test pressure used will be according to the P/T rating of the valve material.
Figure 3. Overview of ISO 15848-1

TA Luft

The Technical Instructions on Air Quality Control (TA Luft), established in 1964 and most recently updated in December 2021, is the general administrative regulation on the Federal Emission Protection Law of the German federal government. In previous editions, TA Luft used the VDI 2440 standard as guidance for emission regulations for valves in Germany. After the recent update in 2021, TA Luft uses the ISO 15848-1(2015) standard for guidance when dealing with emissions standards for valves.

While the testing parameters of the TA Luft must follow the ISO 15848-1(2015) standard, TA Luft regulates permissible leakage limits. Instead of following the tightness classes of ISO 15848-1, TA Luft has designated its own leakage limits and tightness classes of: LA ≤ 1.0E-05 mg/(s*m), LB ≤ 1.0E-04 mg/(s*m) and LC ≤ 1.0E-02 mg/(s*m). These leakage limits apply for both helium and methane according to TA Luft. The tightness criteria, unlike the other standards mentioned, is also pressure dependent. Depending on the tightness class that needs to be reached, the pressure and temperature must fall within a certain parameter.
Figure 4. Overview of TA Luft

Conclusion

Each of these standards is relevant for valve testing parameters but which to use is dependent on end-user test requirements. However,  ISO 15848-1 has a wider range of test options for the end user. Compared to  API testing, which only uses methane as a medium and has a determined maximum temperature and pressure rating, ISO 15848-1 can use helium or methane as the medium, has a wide range of temperatures to choose from, and the pressure depends on the P/T rating of the valve. Also, if the valve surpasses a leakage rate of 100 ppm, according to API, the valve is disqualified. ISO 15848-1 has tightness classes (A – C) and one SSA per endurance class, which give the valve a broader range of acceptability. Since ISO 15848-1 offers this wide range of testing, the end user can choose to test valves according to their functionality in their given application. Because of this, I believe ISO 15848-1 should be the set standard in the US when doing emissions testing on valves.

Tripp Lowery is a project engineer for amtec North America, Inc. in Athens, OH, focused on testing sealability and the reduction of fugitive emissions from valves. Aspiring to become a valve specialist who travels the world for work, Tripp obtained a B.S.M.E from Ohio University.

REFERENCE:

[1] Leak detection and repair: A best practices guide. Washington, DC: U.S. Environmental Protection Agency, Office of Enforcement and Compliance Assurance, 2010.