From refineries processing hazardous chemicals to pharmaceutical and thermal power plants, this valve design is a critical tool that effectively combats environmental pollutants.
By Melanie Jackson and Dan Fisher, Dixon Valve & Coupling Company
Fugitive emissions are the unintentional release of gases or vapors from pressurized equipment due to faulty seals, connections, or other mechanical failures. They can escape from valves, pumps, flanges, and other components in chemical plants, refineries, and manufacturing facilities. Often unnoticed due to their diffused nature, these leaks significantly contribute to environmental pollution.
Unlike exhaust or deliberately vented emissions, fugitive emissions are difficult to quantify and monitor. Key chemicals include volatile organic compounds (VOCs), greenhouse gases (GHGs), and hazardous air pollutants (HAPs).
Types of Fugitive Emissions
Volatile organic compounds, such as benzene, evaporate easily at room temperature, contributing to air pollution. When released, they can form ground-level ozone, a major component of smog, which negatively impacts air quality and human health.
GHGs, like carbon dioxide and methane, drive climate change; carbon dioxide is more prevalent, and methane is at least 28 times more potent.
Hazardous air pollutants, including formaldehyde, are toxic even at low levels and can cause long-term health problems, such as cancer, reproductive issues, and nervous system damage.
Although small leaks across a large facility accumulate significant volumes, especially in continuous operations. Some fugitive emissions contain hazardous chemicals that can cause health problems upon inhalation or through skin contact. Others are highly flammable; even small leaks can trigger explosions, especially in confined spaces or near ignition sources.
Additionally, acids and other caustic substances can corrode metal surfaces, eventually causing equipment failures, larger leaks, malfunctions, or safety hazards.
Regulations
Beyond safety hazards, fugitive emissions have broad environmental implications. To address this, governments worldwide have enacted strict regulations. In the U.S., the Environmental Protection Agency (EPA) enforces several rules under the Clean Air Act (CAA) to curb emissions from various industrial sources, including equipment leaks.
The EPA’s Clean Water Act (CWA) also indirectly addresses fugitive emissions by controlling pollution that contributes to stormwater runoff. The European Union regulates fugitive emissions through its Industrial Emissions Directive (IED).
Violating these regulations is not only detrimental to the environment but can lead to monetary damage.
Consent decrees, used by the EPA, are a penalty to cease or correct certain actions or processes that are polluting the environment. Many major refineries and chemical plants operate under consent decrees that require the installation of equipment to help reduce fugitive emissions. Consent decrees include payments of penalties, which have been as much as $40 million in the past.
Regulatory compliance is driving industries to adopt more effective leak detection and repair programs. These programs involve regular monitoring of equipment and facilities to help identify and quantify fugitive emissions. This allows facilities to address leaks before they cause significant environmental harm or lead to costly fines.
The cost of environmental compliance is just one of the economic consequences of fugitive emissions. Operating costs should also be considered. A boiler fired with natural gas, producing 450 PSI saturated steam and supplied with 230°F feedwater, will yield a steam cost of $2.89 per 1,000 lb.
A small valve leak can be estimated by comparing it to leakage through an orifice. A 1/32” orifice at 450 PSIG will yield a flow of about 10 lbs. per hour, making the cost of the leakage $253.16 per valve, per year. The EPA estimates that there is an average of 7,400 valves at a typical refinery or chemical plant, which brings the average cost of leakage from valves per year for a typical refinery or plant around $1.87 million. A leak-free steam valve not only saves product but pays for itself quickly in terms of energy savings.
The Role of Bellows Sealed Valves
One challenge in reducing fugitive emissions is that industrial valves operate under dynamic conditions, making it difficult to maintain a long-term seal. However, there is a robust, reliable solution to the challenges posed by fugitive emissions – bellows sealed valves.
Bellows sealed valves are designed to address the limitations of conventional valve designs, particularly in high-risk applications. The bellows seal expands and contracts like an accordion as the valve stem moves up or down, enabling precise control of the valve while maintaining a tight, leak-proof seal. Unlike conventional valves that rely on gland packing to seal the stem and bonnet, bellows sealed valves use welded connections.
It is welded to the stem and the valve body, creating a seamless barrier that prevents leaks, even in high-pressure or corrosive environments. Since these valves do not rely on packing material, which degrades over time, they require less frequent maintenance and repair, allowing for more time to make products. This ultimately has a positive impact on uptime and operational costs.
One disadvantage with traditional packed valves is their tendency to loosen up in applications with a lot of thermal cycling. Opening and closing the valve causes rapid wear on the packing and leads to leakage of hot transfer fluids or steam. In contrast, bellows sealed valves do not require adjustments, they are durable, can withstand extreme, corrosive environments and provide a longer service life. Installing bellows sealed valves in the hottest section of the thermal loop eliminates the chance that a leak will cause a serious safety hazard.
Determining Bellows Sealed Valves
There are two ways to manufacture bellows: hydroforming or edge welding. Hydroforming involves pressurizing a metal tube into metal folds, while edge welding entails a series of washer-like plates to form the accordion shape. Both methods form a bellows seal that completes the same task.
However, hydroformed bellows are typically larger and take up more space than welded bellows. There is a common misconception that hydroformed bellows are stronger and will last longer since they incorporate fewer welds. As long as edge-welded bellows are designed and fabricated correctly, and qualified to the MSS SP- 117 standard, the service life should be the same.
When specifying a bellows sealed valve, it is imperative to consider media/corrosion resistance, temperature rating, pressure rating, and cycle life. Standards such as ISO 15848-1, ISO 15848-2, API 622, API 624, and API 641 should be consulted during the selection process. These specifications ensure bellows sealed valves are tested rigorously for performance under challenging conditions, which significantly reduces the likelihood of leaks.
There are low emissions non-bellows valves that meet regulatory standards and minimize fugitive emissions, but they depend on correct installation, may require adjustment, may have a shorter lifespan, and do not eliminate leaks. Therefore, in a critical application requiring absolute sealing, a bellows sealed valve with zero emissions is ideal.
Bellows sealed valves are advantageous for reducing fugitive emissions across many applications. In refineries processing hydrocarbons and hazardous chemicals, they are used in steam, heating fluid lines, and volatile chemical services to prevent leaks.
In the pharmaceutical and chemical industries, purity and safety are critical. Bellows sealed valves prevent contamination by atmospheric gases or the release of toxic fumes. They are also utilized in nuclear and thermal power plants to prevent leakage of radioactive gases or steam.
In cryogenic applications, where gases such as nitrogen, oxygen, and argon must be stored and transported at extremely low temperatures, these valves ensure there are no leaks even under extreme fluctuations.
Fugitive emissions are a silent but significant threat in industrial operations. Bellows sealed valves effectively reduce these emissions, ensure compliance with environmental regulations, and contribute to a cleaner, safer world. As industries prioritize emission control and sustainability, demand for bellows sealed valves will grow, cementing their role as a critical tool in combating fugitive emissions.
About the Experts
Melanie Jackson, an Oklahoma State University graduate with a master’s degree in Agricultural Communications, brings nearly a decade of editorial experience to her role as Creative Production Manager at Dixon. Melanie is dedicated to researching and crafting blog posts, articles, and other marketing materials that communicate Dixon’s industry expertise.
Dan Fisher is Dixon’s Business Development Manager for Specialty Valves, with over 20 years of expertise in metal bellows technology across industrial applications. Dan holds bachelor’s degrees in physics and chemistry from Rhode Island College and an MBA from the University of Houston-Downtown, combining technical acumen with strategic business insights to drive innovative solutions.