In modern industry, the design and application of low fugitive emission valves are increasingly becoming essential technical measures for reducing environmental pollution, improving production efficiency, and ensuring equipment safety. Fugitive emissions refer to the unintentional release of gases, liquids, or other harmful substances into the atmosphere due to equipment leaks or other causes. These emissions primarily stem from valves, flanges, pumps, compressors, and other pipeline components. With stricter environmental regulations and a growing emphasis on environmental protection in industrial sectors, low fugitive emission valves have become a key tool in reducing these harmful emissions.
Low fugitive emission valves play a critical role not only in energy conservation and enhancing production safety but also in reducing the emission of volatile organic compounds (VOCs) and other pollutants. To fully understand the importance, design principles, technological innovations, and application fields of low fugitive emission valves, this article delves into this technical domain.
Fugitive emissions refer to uncontrolled leakage of gases or liquids into the atmosphere in industrial facilities, chemical plants, refineries, natural gas treatment stations, and other manufacturing settings, often due to equipment damage, aging, or poor maintenance. These emissions typically consist of volatile organic compounds, greenhouse gases, toxic gases, and other pollutants. One of the most common sources of fugitive emissions is valves.
Valves, as essential pipeline control devices, frequently regulate fluid flow, pressure, and temperature. However, prolonged operation, material aging, or poor sealing can lead to valve leaks. Common leakage modes include seal failure, microcracks in the valve stem or body, and wear on packing.
Fugitive emissions have far-reaching effects on the environment and human health. The release of harmful gases such as volatile organic compounds (VOCs), methane, nitrogen oxides (NOx), and sulfur dioxide (SO2) not only causes air pollution but can also lead to a range of environmental issues. For example, VOC accumulation undergoes photochemical reactions under sunlight to produce ozone, exacerbating air pollution and contributing to urban smog, which negatively affects respiratory health.
In addition, toxic gases such as benzene and formaldehyde pose direct harm to humans, and prolonged exposure may lead to severe health issues like cancer and neurological disorders. The release of greenhouse gases, such as carbon dioxide and methane, accelerates global warming and negatively impacts climate change. Therefore, reducing fugitive emissions from industrial facilities, especially leaks in valves and pipeline systems, is crucial for both environmental protection and public health.
While both valve leakage and fugitive emissions involve the abnormal release of fluids or gases, there is a clear distinction between the two. Valve leakage typically refers to intentional or unintentional fluid leakage at the valve's sealing components, which can be categorized as external or internal leaks. On the other hand, fugitive emissions refer to subtle and often unexpected releases of harmful substances, particularly volatile organic compounds (VOCs), which can have potential environmental and health impacts.
External Leakage: External leakage occurs when pressure inside the valve escapes to the surrounding environment. This is usually confirmed through a shell test to check for leaks in the valve body.
Internal Leakage: Internal leakage happens when fluid leaks through the valve seat or closure components into the connected pipeline system while the valve is closed. It is examined through seat leakage or closure tests, with allowable leakage depending on the testing standards. While internal leakage usually occurs within the pipeline system, it may also extend to the external environment when the valve is located at the pipeline's end.
Fugitive emissions are difficult to detect and are typically undesirable. In industrial settings, these emissions often involve harmful gases such as VOCs, released through leaks in equipment such as flanged joints, pumps, compressors, storage tanks, and valves. VOC emissions are harmful to the environment and are generally measured in parts per million (ppm).
The design of low fugitive emission valves aims to reduce gas and liquid leaks by optimizing the valve sealing system. This goal is achieved through several technical improvements.
Low fugitive emission valves utilize advanced sealing materials such as PTFE (polytetrafluoroethylene), graphite packing, polyurethane, and others. These materials exhibit excellent resistance to high temperatures, corrosion, and wear, ensuring that the valve maintains a seal even in high-pressure, high-temperature environments. Furthermore, these materials retain their elasticity and durability over extended use, reducing leaks caused by aging or wear. For instance, PTFE sealing materials maintain their sealing performance under high-temperature and high-pressure conditions and are widely used in industries like petrochemical, natural gas treatment, pharmaceuticals, and food processing.
The valve body design of low fugitive emission valves is focused on minimizing the possibility of leaks. The design must ensure both structural strength and precision of the valve's contact surfaces. The valve seat and core require a strict fit, and precisely machined seat and core components enable more efficient sealing. Additionally, low fugitive emission valves are typically made of stainless steel or other corrosion-resistant materials to further enhance their sealing performance.
The valve stem, a key component connecting the actuator and the valve seat, directly influences the valve's leakage rate. Low fugitive emission valves employ multi-seal designs for the stem, including bellows, O-rings, and other multi-seal structures, ensuring effective prevention of gas leaks even with frequent stem movement.
To ensure the sealing performance of low fugitive emission valves, manufacturers conduct strict leakage tests for each valve. Common testing methods include nitrogen leakage testing, helium leakage testing, gas absorption guns, and water immersion methods. These tests ensure that the leakage rate of the valve meets industry standards, typically requiring leakage levels to be no higher than 100 ppm.
Low fugitive emission valves are widely used in industries such as petroleum, natural gas, chemical, power generation, pharmaceuticals, and food processing. Particularly in areas where fugitive emissions must be strictly controlled, low fugitive emission valves play an irreplaceable role.
The petroleum and natural gas industry is one of the main application fields for low fugitive emission valves. In these industries, the transportation of natural gas through pipelines and the refining process generate large amounts of VOCs. If valves do not seal properly, fugitive emissions can severely pollute the air and lead to resource wastage. Low fugitive emission valves are critical in these environments.
For example, in natural gas processing plants, low fugitive emission ball valves and globe valves are commonly used for regulating and switching natural gas. Since natural gas contains a high amount of methane, leaks can result in resource loss and safety hazards such as explosions. Low fugitive emission valves help reduce leakage risks and enhance safety and environmental protection.
The chemical and pharmaceutical industries involve numerous volatile chemicals. If valve seals fail, harmful gases can leak and pose threats to the environment and worker health. Low fugitive emission valves, utilizing efficient sealing technologies, can function stably in these high-risk environments and ensure that harmful substances do not leak into the atmosphere.
The food processing and packaging industry has stringent requirements for hygiene and safety. Low fugitive emission valves not only prevent the leakage of volatile components in food raw materials but also ensure a clean and pollution-free production environment. These valves are widely used in gas delivery, liquid regulation, and other processes to mitigate the pollution risks associated with equipment leaks.
To ensure the performance of low fugitive emission valves, strict testing standards have been established by national and international standardization organizations. Some of the key standards include:
ISO 15848: This standard specifies the testing methods and performance requirements for low fugitive emission valves, including gas leakage and sealing life tests. It is a globally recognized certification standard for low fugitive emission valves across multiple industries.
API 622: This standard targets valves with rising stem designs using graphite packing and specifies the test methods for low fugitive emissions, requiring that leakage be below prescribed limits.
API 624: This standard sets leakage testing standards for specific valves, such as gate valves, requiring exceptionally low leakage rates in high-pressure environments.
API 641: This standard applies to quarter-turn valves, requiring that valves maintain low fugitive emissions under various working conditions and undergo comprehensive leakage testing.
Low fugitive emission valves effectively reduce harmful gas leaks in industrial facilities, protect the environment, and enhance production efficiency, reduce energy consumption, and extend equipment lifespan. With the gradual tightening of environmental regulations and the increasing focus on green manufacturing in industrial sectors, low fugitive emission valves will play a more important role in the future.
By employing advanced sealing technologies, optimized valve body designs, and stringent leakage testing, low fugitive emission valves have become vital technical tools for environmental protection and industrial safety. Whether in petrochemical, natural gas processing, or the food and pharmaceutical industries, low fugitive emission valves are essential in helping industrial facilities develop in a more environmentally friendly and sustainable direction.
