In the industrial field, the fugitive emission control performance of valves is of critical importance. It not only affects production efficiency and product quality but also directly impacts environmental safety and personnel health. As global awareness of environmental protection and industrial safety continues to grow, countries have successively established strict testing and certification standards to ensure that valves can effectively prevent medium leakage under various operating conditions. This article will provide a detailed introduction to the main international valve fugitive emission test standards, key sealing technologies, as well as the success factors and practical guidelines for achieving low-emission sealing.
Internationally, there are many standards for testing and certifying the fugitive emission control performance of process control valves. These standards provide strict specifications for valve emission control, ensuring that valves can effectively prevent medium leakage under all operating conditions. The following are the main international valve fugitive emission test standards currently in use:
In Europe, the ISO 15848-1 test standard is currently recognized as the dominant testing standard. This standard sets strict requirements for valve fugitive emission control, covering the entire process from design to testing. It requires valves to control leakage at the molecular level, meaning that even small molecules like helium must be effectively sealed. The ISO 15848-1 standard not only imposes very high demands on valve sealing performance but also provides detailed specifications for testing methods and certification procedures, ensuring the accuracy and reliability of test results.
In the United States, the API 624 standard is the main standard for fugitive emission testing. Similar to ISO 15848-1, API 624 also specifies sealing performance requirements for valves under different operating conditions. It particularly emphasizes sealing performance under harsh conditions such as high temperature, high pressure, and corrosive media, ensuring that valves can operate stably over the long term in actual industrial environments. The API 624 standard also provides strict regulations on valve material selection, design details, and testing methods to meet the high fugitive emission control requirements of the U.S. industry.
Germany has particularly strict fugitive emission control requirements for valves in the chemical and petrochemical industries. All valves used in these industries must obtain VDI 2440 certification. VDI 2440 certification not only focuses on valve sealing performance but also comprehensively evaluates overall design, material quality, and manufacturing processes. Valves certified under VDI 2440 can maintain excellent sealing performance under extreme conditions, effectively preventing the leakage of harmful media and ensuring the safe operation of chemical and petrochemical industries.
The fugitive emission control performance of valves mainly relies on their sealing technology. The effectiveness of sealing directly determines whether a valve can effectively prevent medium leakage under various operating conditions. The following are key sealing technologies for valve fugitive emission control and their applications:
Stem packing seals are the most critical fugitive emission control component in a valve because they are the only sealing surfaces in dynamic contact, between the ambient pressure external environment and the high pressure inside the valve. The performance of stem packing seals directly affects valve fugitive emission control, and therefore must be given high attention in design and selection.
Expanded Graphite Packing: Expanded graphite is a common packing material with good sealing performance and high-temperature resistance. It can be woven or molded to seal large-molecule media such as steam. However, when sealing small-molecule media like helium, pure graphite structures need to be used in combination with other materials.
PTFE Packing: Polytetrafluoroethylene (PTFE) packing has excellent chemical stability and good sealing performance, but its usage temperature range is narrow, not exceeding 260°C. Therefore, it is mainly used under low-temperature conditions and has limited application in fire-resistant scenarios.
Spring-Energized Seals: Spring-energized seals achieve sealing through the tension of spring elements. At low pressure, the spring provides tension; at high pressure, the internal system pressure further tightens the seal. These seals can be made of different polymer materials, such as PTFE, and usually require backup rings to improve reliability and high-pressure resistance. In ultra-low-temperature conditions, spring-energized seals typically use special material jackets and springs to ensure reliability under extreme conditions.
Selecting high-quality stem packing materials alone is not enough; the valve design must also be optimized to ensure suitability for low fugitive emission performance.
The sealing stress of stem packing is directly generated by the packing gland and packing follower. This radial force deforms the packing and seals it while creating friction on the stem. Higher sealing stress can effectively reduce leakage but increases stem friction. Therefore, design must balance sealing stress and friction, especially for manually operated or frequently used valves. To achieve low fugitive emission sealing, packing box configurations are typically improved, such as using higher-strength bolts to meet the requirements for high sealing stress.
The clearance of the packing box is a key factor affecting packing sealing performance. Under high sealing stress, packing is prone to extrusion, leading to loss of sealing stress and packing damage. Therefore, the packing box clearance must be kept to a minimum while ensuring valve operability. Critical areas include the bottom of the packing box and the inner and outer diameters of the packing follower. Additionally, chamfers and fillets of the packing box and other components must be designed to prevent packing extrusion.
Stem surface roughness is crucial for low fugitive emission control. Excessive or insufficient roughness can cause packing material to be carried away, affecting sealing performance. Appropriate surface roughness ensures good sealing contact between the packing and stem while avoiding sticking caused by overly smooth surfaces. Therefore, stem surface roughness must be strictly controlled during manufacturing to meet low-emission control requirements.
The installation process of packing is also critical for low fugitive emission control. Laboratory installation conditions may differ from actual field or manufacturer installation processes. Correct installation steps are key to achieving low fugitive emission sealing, with particular attention to:
Avoiding Packing Damage: Packing must be handled carefully during installation to prevent damage. Each layer must achieve sufficient sealing stress to ensure performance.
Repeated Testing and Adjustment: Multiple experiments and adjustments may be required during installation to achieve ideal sealing. This requires experienced personnel with a high level of responsibility to strictly follow installation guidelines.
Achieving low fugitive emission sealing is crucial for valve performance. It can effectively reduce medium leakage, improve production efficiency, and ensure environmental safety and personnel health. The three main success factors are:
Low-emission packing usually contains special fillers and barrier agents, making its structure dense and capable of effectively preventing medium leakage. Graphite packing is preferred under high-temperature conditions, while spring-energized seals are more suitable for low-temperature conditions. Choosing the right sealing material is the foundation for achieving low-emission sealing.
The overall condition of the valve directly affects sealing performance. Valve design, manufacturing quality, and maintenance must meet low fugitive emission requirements. The packing box configuration, stem surface roughness, and other design details must be optimized to ensure sealing performance.
Proper installation is key to achieving low-emission sealing. Installers must strictly follow installation guidelines, ensure packing is not damaged, and that each layer achieves sufficient sealing stress. Multiple experiments and adjustments may be required to achieve optimal sealing performance.
To ensure that valves can effectively achieve low fugitive emission sealing in actual applications, the following practical guidelines and recommendations are provided:
When selecting valves, it is essential to ensure that they have passed relevant tests and certifications. Whether ISO 15848-1, API 624, or VDI 2440, these standards provide rigorous guarantees for valve fugitive emission control performance. Certified valves have undergone strict evaluations in design, material selection, and manufacturing processes, ensuring effective prevention of medium leakage.
During the design stage, valve fugitive emission performance should be fully considered. Optimizing the configuration of the packing box, selecting appropriate sealing materials, and controlling stem surface roughness are key to achieving low fugitive emission sealing. These design optimizations can effectively enhance valve sealing performance and reduce the risk of leakage.
Proper installation and regular maintenance are crucial to ensuring long-term stable valve operation. Installation personnel must receive professional training and strictly follow installation guidelines. At the same time, regular inspection and maintenance of valves, along with timely replacement of damaged seals, can effectively extend the service life of the valve and ensure its sealing performance.
The professional competence of operating and maintenance personnel is critical to valve fugitive emission control. Regular training for relevant personnel, to familiarize them with valve structure, sealing principles, and operation and maintenance methods, can effectively reduce leakage incidents caused by human factors.
Valve fugitive emission control is an important aspect of industrial production, directly related to production efficiency, product quality, environmental safety, and personnel health. Strict international testing and certification standards provide strong assurance for valve emission control, while high-quality sealing materials, optimized designs, and proper installation and maintenance are key to achieving low fugitive emission sealing. Through this detailed introduction, readers can gain a deeper understanding of valve fugitive emission control. In practical applications, only by comprehensively considering these factors can valves reliably prevent medium leakage under all operating conditions, contributing to safe and environmentally responsible industrial production.