Mastering Valve Fugitive Emissions: Standards & Control

Fugitive Emissions Testing for Valves

Valves often include dynamic sealing structures, such as the seal between the valve stem and the packing gland. Leakage from the valve stem packing is a primary source of external valve leaks. Historically, the industrial and engineering sectors have not focused much on valve external leakage characteristics. Operational personnel typically judge whether a valve requires attention based on visible leaks or the detection of strong odors.

Importance of Fugitive Emissions Control

In petrochemical production, many substances can cause severe air pollution, with some being toxic or even highly toxic. Petrochemical products generally have small molecular weights, making them prone to leaking from production equipment and difficult to detect visually. With increased public awareness of environmental pollution, the need for quantitative control of valve emissions has become a priority.

Development of Standards

The ASME/API standards have traditionally set very basic requirements for valve leakage, primarily focusing on the absence of visible leaks during sealing tests. However, in the 1970s, several U.S. petrochemical plants, in cooperation with Canadian and European counterparts and valve manufacturers, began researching valve emissions and proposed quantifiable indicators. These efforts have influenced the standards of the U.S. Environmental Protection Agency (EPA).

For example, the EPA's requirements for industrial equipment emissions have evolved from an initial limit of 5000×10⁻⁶ to 2500×10⁻⁶, and eventually to 1500×10⁻⁶ by 1997. Specific states, such as California, have set even stricter limits, such as 500×10⁻⁶.

Key Standards for Valve Emissions

To meet rising environmental standards globally, several key standards for valve emissions have been developed, including ISO 15848-1, ISO 15848-2, and API 622.

• ISO 15848-1 specifies the requirements for type testing of valve emissions.
• ISO 15848-2 outlines product testing requirements for valve emissions.
• The API 622 standard, introduced by the American Petroleum Institute, focuses on the packing material testing before valves are evaluated under API 624.
• The API 624 standard sets requirements for the design, materials, manufacture, assembly, testing, inspection, and documentation of fugitive emission valves, mandating approximately 310 cycles at varying temperatures.
• API 641 pertains to valves that operate with a quarter-turn, such as ball valves.

Classification of Emissions

The ISO 15848 standards categorize valves based on their fugitive emission performance into three classes:

• Class A: ≤ 1.0E-05 mg/(s*m); ≤ 50 ppmv
• Class B: ≤ 1.0E-04 mg/(s*m); ≤ 100 ppmv
• Class C: ≤ 1.0E-02 mg/(s*m); ≤ 500 ppmv

TA Luft

TA Luft, or "Technical Instructions on Air Quality Control," provides guidelines for controlling air pollution in Germany. It includes requirements for measuring and reducing valve emissions, encompassing various temperature and valve cycling tests.

Conclusion

The evolution of fugitive emission standards reflects the growing environmental awareness and the need for stringent control measures in the petrochemical industry. Standards such as ISO 15848 and API 622/624 provide comprehensive frameworks for assessing and minimizing valve emissions, contributing to better environmental protection.

FAQs

1. What are fugitive emissions in valves?
   • Fugitive emissions refer to leaks of gases or vapors from pressurized equipment, including valves, due to faulty seals or other imperfections.
2. Why are fugitive emissions a concern in the petrochemical industry?
   • Many petrochemical substances are toxic or harmful to the environment, making their control crucial for safety and regulatory compliance.
3. What is the difference between ISO 15848-1 and ISO 15848-2?
   • ISO 15848-1 focuses on type testing requirements for valve emissions, while ISO 15848-2 outlines product testing requirements.
4. How do API 622 and API 624 standards relate?
   • API 622 tests the packing material of valves, and only if it passes can the valve proceed to testing under API 624, which covers the entire valve design and function.
5. What does the classification system in ISO 15848 signify?
   • The classification system (Class A, B, C) in ISO 15848 indicates the level of allowable fugitive emissions from valves, with Class A being the most stringent.